Status of groundwater quality in the San Fernando--San Gabriel study unit, 2005--California GAMA Priority Basin Project

USGS Publications Warehouse

Land, Michael; Kulongoski, Justin T.; Belitz, Kenneth

2012-01-01

Groundwater quality in the approximately 460-square-mile San Fernando--San Gabriel (FG) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study area is in Los Angeles County and includes Tertiary-Quaternary sedimentary basins situated within the Transverse Ranges of southern California. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA FG study was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer systems (hereinafter referred to as primary aquifers) throughout California. The assessment is based on water-quality and ancillary data collected in 2005 by the USGS from 35 wells and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifers were defined by the depth interval of the wells listed in the CDPH database for the FG study unit. The quality of groundwater in primary aquifers may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. This study assesses the status of the current quality of the groundwater resource by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources in the primary aquifers of the FG study unit, not the treated drinking water delivered to consumers by water purveyors.

Hydrogeologic Framework of Bedrock Units and Initial Salinity Distribution for a Simulation of Groundwater Flow for the Lake Michigan Basin

USGS Publications Warehouse

Lampe, David C.

2009-01-01

The U.S. Geological Survey is assessing groundwater availability in the Lake Michigan Basin. As part of the assessment, a variable-density groundwater-flow model is being developed to simulate the effects of groundwater use on water availability throughout the basin. The hydrogeologic framework for the Lake Michigan Basin model was developed by grouping the bedrock geology of the study area into hydrogeologic units on the basis of the functioning of each unit as an aquifer or confining layer within the basin. Available data were evaluated based on the areal extent of coverage within the study area, and procedures were established to characterize areas with sparse data coverage. Top and bottom altitudes for each hydrogeologic unit were interpolated in a geographic information system for input to the model and compared with existing maps of subsurface formations. Fourteen bedrock hydrogeologic units, making up 17 bedrock model layers, were defined, and they range in age from the Jurassic Period red beds of central Michigan to the Cambrian Period Mount Simon Sandstone. Information on groundwater salinity in the Lake Michigan Basin was compiled to create an input dataset for the variable-density groundwater-flow simulation. Data presented in this report are referred to as 'salinity data' and are reported in terms of total dissolved solids. Salinity data were not available for each hydrogeologic unit. Available datasets were assigned to a hydrogeologic unit, entered into a spatial database, and data quality was visually evaluated. A geographic information system was used to interpolate salinity distributions for each hydrogeologic unit with available data. Hydrogeologic units with no available data either were set equal to neighboring units or were vertically interpolated by use of values from units above and below.

Ground-water data collected in the Missouri River Basin units in Kansas during 1953

USGS Publications Warehouse

Mason, B.J.

1954-01-01

Ground-water studies in the Missouri River basin were begun by the United States Geological Survey during the fall of 1945 as a part of a program for the development of the resources of the basin by the United States Bureau of Reclamation and other Federal Agencies. The studies of the ground-water resources in the part of Kansas that lies within the Missouri River basin have been coordinated with the cooperative program of ground water studies which were already being made in Kansas by the U. S. Geological Survey, the State Geological Survey of Kansas, the Division of Sanitation of the Kansas State Board of Health, and the Division of Water Resources of the Kansas State Board of Agriculture.Areas in which ground-water data have been and are being collected are the following: Almena unit in Norton and Phillips Counties; Bostwick unit in Jewell, Republic, and Cloud Counties; Cedar Bluff unit in Ellis, Rush, and Trego Counties; Glen Elder unit in Mitchell County; Kanopolis unit in Ellsworth, McPherson, and Saline Counties; Kirwin unit in Phillips, Smiths and Osborne Counties; St. Francis unit in Cheyenne County; Webster unit in Osborne County; and Wilson unit in Lincoln County. (See fig. 1.) Data relating to the Ladder Creek project in Greeley, Gove, Lane, Logan, Scott, Wallace, and Wichita Counties will be published later in a separate report.

Status and understanding of groundwater quality in the two southern San Joaquin Valley study units, 2005-2006 - California GAMA Priority Basin Project

USGS Publications Warehouse

Burton, Carmen A.; Shelton, Jennifer L.; Belitz, Kenneth

2012-01-01

Groundwater quality in the southern San Joaquin Valley was investigated from October 2005 through March 2006 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project is conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board and the Lawrence Livermore National Laboratory. There are two study units located in the southern San Joaquin Valley: the Southeast San Joaquin Valley (SESJ) study unit and the Kern County Subbasin (KERN) study unit. The GAMA Priority Basin Project in the SESJ and KERN study units was designed to provide a statistically unbiased, spatially distributed assessment of untreated groundwater quality within the primary aquifers. The status assessment is based on water-quality and ancillary data collected in 2005 and 2006 by the USGS from 130 wells on a spatially distributed grid, and water-quality data from the California Department of Public Health (CDPH) database. Data was collected from an additional 19 wells for the understanding assessment. The aquifer systems (hereinafter referred to as primary aquifers) were defined as that part of the aquifer corresponding to the perforation interval of wells listed in the CDPH database for the SESJ and KERN study units. The status assessment of groundwater quality used data from samples analyzed for anthropogenic constituents such as volatile organic compounds (VOCs) and pesticides, as well as naturally occurring inorganic constituents such as major ions and trace elements. The status assessment is intended to characterize the quality of untreated groundwater resources within the primary aquifers in the SESJ and KERN study units, not the quality of drinking water delivered to consumers. Although the status assessment applies to untreated groundwater, Federal and California regulatory and non-regulatory water-quality benchmarks that apply to drinking water are used to provide context for the results. Relative-concentrations (sample concentration divided by benchmark concentration) were used for evaluating groundwater. A relative-concentration greater than 1.0 indicates a concentration greater than the benchmark and is classified as high. The relative-concentration threshold for classifying inorganic constituents as moderate or low was 0.5; for organic constituents the threshold between moderate and low was 0.1. Aquifer-scale proportion was used as the primary metric for assessing the quality of untreated groundwater for the study units. High aquifer-scale proportion is defined as the areal percentage of the primary aquifers with a high relative-concentration for a particular constituent or class of constituents. Moderate and low aquifer-scale proportions were defined as the areal percentage of the primary aquifers with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable for the two study units in the southern San Joaquin Valley (within 90 percent confidence intervals). The status assessment showed that inorganic constituents were more prevalent than organic constituents and that relative-concentrations were higher for inorganic constituents than for organic constituents. For inorganic constituents with human-health benchmarks, the relative-concentration of at least one constituent in the SESJ study unit was high in 30 percent of the primary aquifers. In the KERN study unit, the relative-concentration of at least one constituent was high in 23 percent of the primary aquifers. In the SESJ and KERN study units, the inorganic constituents with human-health benchmarks detected at high relative-concentrations in more than 2 percent of the primary aquifers were arsenic, boron, vanadium, nitrate, uranium, and gross alpha radioactivity. Additional constituents with human-health benchmarks—antimony, radium, and fluoride—were detected at high relative-concentrations in the KERN study unit. For inorganic constituents with aesthetic benchmarks (secondary maximum contaminant levels, SMCLs), the relative-concentration of at least one constituent in the SESJ study unit was high in 6.6 percent of the primary aquifers. In the KERN study unit, the relative-concentration of at least one constituent was high in 22 percent of the primary aquifers. Inorganic constituents with aesthetic benchmarks detected at high relative-concentrations in the primary aquifers in the SESJ and KERN study units were iron and manganese. Additional constituents with aesthetic benchmarks—total dissolved solids (TDS), sulfate, and chloride—were detected at high relative-concentrations in the KERN study unit. In contrast, the status assessment for organic constituents with human-health benchmarks showed that relative-concentrations were high in 4.8 percent and 2.1 percent of the primary aquifers in the SESJ and KERN study units, respectively. The special-interest constituent, perchlorate, was detected at high relative-concentrations in 1.2 percent of the primary aquifers in the SESJ study unit. Twenty-eight of the 78 VOCs (not including fumigants) analyzed were detected. Of these 28 VOCs, benzene had high relative-concentrations in the SESJ study unit, and relative-concentrations for the other 27 VOCs were moderate and low. Five of the 10 fumigants were detected; 1,2-dibromo-3-chloropropane (DBCP) was the only fumigant with high relative-concentrations in the SESJ and KERN study units. Of the 136 pesticides and pesticide degradates analyzed, 33 were detected. Human-health benchmarks were established for eighteen of the detected pesticides. Dieldrin was detected at moderate relative-concentrations in the SESJ and KERN study units. All other pesticides detected with human-health benchmarks were present at low relative-concentrations. The detection frequencies for two of these pesticides—simazine and atrazine—were greater than or equal to 10 percent in the SESJ and KERN study units. The understanding assessment of groundwater quality included an analysis of correlations of selected water-quality constituents or classes of constituents with potential explanatory factors. The understanding assessment indicated that the concentrations of many trace elements and major ions were correlated to well depth, groundwater age, and/or geochemical conditions. Many trace elements were positively correlated with depth. Arsenic, boron, vanadium, fluoride, manganese, and iron concentrations increased with well depth or depth to top-of-perforations. The concentrations for these trace elements also were higher in older (pre-modern) groundwater. In contrast, uranium concentrations decreased with increasing depth and groundwater age. Most trace elements were correlated to geochemical conditions. Arsenic, antimony, boron, fluoride, manganese, and iron concentrations generally were higher wherever the pH of the groundwater was greater than 7.6. Concentrations for these constituents generally were higher at low concentrations of dissolved oxygen (DO). Uranium was the exception; uranium concentrations generally were lower at high pH and at high concentrations of DO. Nitrate concentrations generally were lower in deeper wells. Nitrate concentrations also were higher in groundwater with higher DO. Total dissolved solids, sulfate, and chloride concentrations were higher in the KERN study unit than in the SESJ study unit. Total dissolved solids were negatively correlated with pH in the KERN study unit. Total dissolved solids and sulfate were higher in areas with more agricultural land use. Chloride concentrations increased with depth to top-of-perforations in the KERN study unit. Organic constituents and constituents of special interest, like many inorganic constituents, were correlated with well depth, groundwater age, and DO. Unlike most trace elements, however, solvent and pesticide detections, and total trihalomethanes (THM), DBCP, and perchlorate concentrations decreased with increasing well depth. Volatile organic compound, solvent, and pesticide detections, and THM concentrations also were lower in older (pre-modern) groundwater than in modern-age groundwater. Solvent detections and total THM, DBCP, and perchlorate concentrations increased with increasing DO concentrations.

Hydrogeologic Framework, Groundwater Movement, and Water Budget in Tributary Subbasins and Vicinity, Lower Skagit River Basin, Skagit and Snohomish Counties, Washington

USGS Publications Warehouse

Savoca, Mark E.; Johnson, Kenneth H.; Sumioka, Steven S.; Olsen, Theresa D.; Fasser, Elisabeth T.; Huffman, Raegan L.

2009-01-01

A study to characterize the groundwater-flow system in four tributary subbasins and vicinity of the lower Skagit River basin was conducted by the U.S. Geological Survey to assist Skagit County and the Washington State Department of Ecology in evaluating the effects of potential groundwater withdrawals and consumptive use on tributary streamflows. This report presents information used to characterize the groundwater and surface-water flow system in the subbasins, and includes descriptions of the geology and hydrogeologic framework of the subbasins; groundwater recharge and discharge; groundwater levels and flow directions; seasonal groundwater-level fluctuations; interactions between aquifers and the surface-water system; and a water budget for the subbasins. The study area covers about 247 mi2 along the Skagit River and its tributary subbasins (East Fork Nookachamps Creek, Nookachamps Creek, Carpenter Creek, and Fisher Creek) in southwestern Skagit County and northwestern Snohomish County, Washington. The geology of the area records a complex history of accretion along the continental margin, mountain building, deposition of terrestrial and marine sediments, igneous intrusion, and the repeated advance and retreat of continental glaciers. A simplified surficial geologic map was developed from previous mapping in the area, and geologic units were grouped into nine hydrogeologic units consisting of aquifers and confining units. A surficial hydrogeologic unit map was constructed and, with lithologic information from 296 drillers'logs, was used to produce unit extent and thickness maps and four hydrogeologic sections. Groundwater in unconsolidated aquifers generally flows towards the northwest and west in the direction of the Skagit River and Puget Sound. This generalized flow pattern is likely complicated by the presence of low-permeability confining units that separate discontinuous bodies of aquifer material and act as local groundwater-flow barriers. Groundwater-flow directions in the sedimentary aquifer likely reflect local topographic relief (radial flow from bedrock highs) and more regional westward flow from the mountains to the Puget Sound. The largest groundwater-level fluctuations observed during the monitoring period (October 2006 through September 2008) occurred in wells completed in the sedimentary aquifer, and ranged from about 3 to 27 feet. Water levels in wells completed in unconsolidated hydrogeologic units exhibited seasonal variations ranging from less than 1 to about 10 feet. Synoptic streamflow measurements made in August 2007 and June 2008 indicate a total groundwater discharge to creeks in the tributary subbasin area of about 13.15 and 129.6 cubic feet per second (9,520 and 93,830 acre-feet per year), respectively. Streamflow measurements illustrate a general pattern in which the upper reaches of creeks in the study area tended to gain flow from the groundwater system, and lower creek reaches tended to lose water. Large inflows from tributaries to major creeks in the study area suggest the presence of groundwater discharge from upland areas underlain by bedrock. The groundwater system within the subbasins received an average (September 1, 2006 to August 31, 2008) of about 92,400 acre-feet or about 18 inches of recharge from precipitation a year. Most of this recharge (65 percent) discharges to creeks, and only about 3 percent is withdrawn from wells. The remaining groundwater recharge (32 percent) leaves the subbasin groundwater system as discharge to the Skagit River and Puget Sound.

Groundwater quality in the Madera and Chowchilla subbasins of the San Joaquin Valley, California

USGS Publications Warehouse

Shelton, Jennifer L.; Fram, Miranda S.; Belitz, Kenneth

2013-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s untreated groundwater quality and increases public access to groundwater-quality information. The Madera and Chowchilla subbasins of the San Joaquin Valley constitute one of the study units being evaluated. The Madera-Chowchilla study unit is about 860 square miles and consists of the Madera and Chowchilla groundwater subbasins of the San Joaquin Valley Basin (California Department of Water Resources, 2003; Shelton and others, 2009). The study unit has hot, dry summers and cool, moist winters. Average annual rainfall ranges from 11 to 15 inches, most of which occurs between November and February. The main surface-water features in the study unit are the San Joaquin, Fresno, and Chowchilla Rivers, and the Madera and Chowchilla canals. Land use in the study unit is about 69 percent (%) agricultural, 28% natural (mainly grasslands), and 3% urban. The primary crops are orchards and vineyards. The largest urban area is the city of Madera. The primary aquifer system is defined as those parts of the aquifer corresponding to the perforated intervals of wells listed in the California Department of Public Health (CDPH) database. In the Madera-Chowchilla study unit, these wells typically are drilled to depths between 200 and 800 feet, consist of a solid casing from land surface to a depth of about 140 to 400 feet, and are perforated below the solid casing. Water quality in the primary aquifer system may differ from that in the shallower and deeper parts of the aquifer system. The primary aquifer system in the study unit consists of Quaternary-age alluvial-fan and fluvial deposits that were formed by the rivers draining the Sierra Nevada. Sediments consist of gravels, sands, silts, and clays and generally are coarser closest to the Sierra Nevada and become finer towards the center of the basin. The structure and composition of the deposits in the Madera-Chowchilla study unit are different from those in other parts of the eastern San Joaquin Valley because the Fresno and Chowchilla Rivers primarily drain the Sierra Nevada foothills, whereas the larger rivers drain higher elevations with greater sediment supply. These differences in the sources of sediments are important because they may affect the groundwater chemistry and the physical structure of the sedimentary deposits. Some of the clay layers are lacustrine deposits, the most extensive of which, the Corcoran Clay, underlies the western part of the study unit and divides the primary aquifer system into an unconfined to semi-confined upper system and a largely confined lower system. Regional lateral flow of groundwater is southwest towards the valley trough. Irrigation return flows are the major source of groundwater recharge, and groundwater pumping is the major source of discharge. Groundwater on a lateral flow path may be repeatedly extracted by pumping wells and reapplied at the surface multiple times before reaching the valley trough, resulting in a substantial component of downward vertical flow (Burow and others, 2004; Phillips and others, 2007; Faunt, 2009). This flow pattern enhances movement of water from shallow depths to the primary aquifer system.

Bibliography of groundwater resources of the glacial aquifer systems in Washington, Idaho, and northwestern Montana, 1905-2011

USGS Publications Warehouse

Kahle, Sue C.; Futornick, Zoe O.

2012-01-01

The U.S. Geological Survey Groundwater Resources Program is undertaking a series of regional groundwater availability studies to improve our understanding of groundwater availability in major aquifers across the Nation. One of the objectives of the Glacial Principal Aquifers study (proposed) is to provide information on the occurrence of groundwater in glacial aquifers in the United States, an area that includes parts of the northern continental States and much of Alaska. Toward this effort, a literature search was conducted to identify readily available documents that describe the occurrence of groundwater in glacial aquifers in the United States. This bibliography provides citations for documents, as well as codes indicating types of information available in each, for Washington, Idaho, and northwestern Montana—an area corresponding approximately to the southern extent of the Cordilleran ice sheet.

Mapping Evapotranspiration Units in the Basin and Range Carbonate-Rock Aquifer System, White Pine County, Nevada, and Adjacent Areas in Nevada and Utah

USGS Publications Warehouse

Smith, J. LaRue; Laczniak, Randell J.; Moreo, Michael T.; Welborn, Toby L.

2007-01-01

Accurate estimates of ground-water discharge are crucial in the development of a water budget for the Basin and Range carbonate-rock aquifer system study area. One common method used throughout the southwestern United States is to estimate ground-water discharge from evapotranspiration (ET). ET is a process by which water from the Earth's surface is transferred to the atmosphere. The volume of water lost to the atmosphere by ET can be computed as the product of the ET rate and the acreage of vegetation, open water, and moist soil through which ET occurs. The procedure used in the study groups areas of similar vegetation, water, and soil conditions into different ET units, assigns an average annual ET rate to each unit, and computes annual ET from each ET unit within the outer extent of potential areas of ground-water discharge. Data sets and the procedures used to delineate the ET-unit map used to estimate ground-water discharge from the study area and a qualitative assessment of the accuracy of the map are described in this report.

Groundwater quality in the San Francisco Bay groundwater basins, California

USGS Publications Warehouse

Parsons, Mary C.; Kulongoski, Justin T.; Belitz, Kenneth

2013-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Selected groundwater basins of the San Francisco Bay area constitute one of the study units being evaluated.

ALTERNATIVE REMEDIATION TECHNOLOGY STUDY FOR GROUNDWATER TREATMENT AT 200-PO-1 OPERABLE UNIT AT HANFORD SITE

DOE Office of Scientific and Technical Information (OSTI.GOV)

DADO MA

2008-07-31

This study focuses on the remediation methods and technologies applicable for use at 200-PO-I Groundwater Operable Unit (OU) at the Hanford Site. The 200-PO-I Groundwater au requires groundwater remediation because of the existence of contaminants of potential concern (COPC). A screening was conducted on alternative technologies and methods of remediation to determine which show the most potential for remediation of groundwater contaminants. The possible technologies were screened to determine which would be suggested for further study and which were not applicable for groundwater remediation. COPCs determined by the Hanford Site groundwater monitoring were grouped into categories based on properties linkingmore » them by remediation methods applicable to each COPC group. The screening considered the following criteria. (1) Determine if the suggested method or technology can be used for the specific contaminants found in groundwater and if the technology can be applied at the 200-PO-I Groundwater au, based on physical characteristics such as geology and depth to groundwater. (2) Evaluate screened technologies based on testing and development stages, effectiveness, implementability, cost, and time. This report documents the results of an intern research project conducted by Mathew Dado for Central Plateau Remediation in the Soil and Groundwater Remediation Project. The study was conducted under the technical supervision of Gloria Cummins and management supervision of Theresa Bergman and Becky Austin.« less

Southwest principal aquifers regional ground-water quality assessment

USGS Publications Warehouse

Anning, D.W.; Thiros, Susan A.; Bexfield, L.M.; McKinney, T.S.; Green, J.M.

2009-01-01

The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey is conducting a regional analysis of water quality in the principal aquifers in the southwestern United States. The Southwest Principal Aquifers (SWPA) study is building a better understanding of the susceptibility and vulnerability of basin-fill aquifers in the region to ground-water contamination by synthesizing the baseline knowledge of ground-water quality conditions in 15 basins previously studied by the NAWQA Program. The improved understanding of aquifer susceptibility and vulnerability to contamination is assisting in the development of tools that water managers can use to assess and protect the quality of ground-water resources. This fact sheet provides an overview of the basin-fill aquifers in the southwestern United States and description of the completed and planned regional analyses of ground-water quality being performed by the SWPA study.

Groundwater quality in the San Diego Drainages Hydrogeologic Province, California

USGS Publications Warehouse

Wright, Michael T.; Belitz, Kenneth

2011-01-01

More than 40 percent of California's drinking water is from groundwater. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State's groundwater quality and increases public access to groundwater-quality information. The San Diego Drainages Hydrogeologic Province (hereinafter referred to as San Diego) is one of the study units being evaluated. The San Diego study unit is approximately 3,900 square miles and consists of the Temecula Valley, Warner Valley, and 12 other alluvial basins (California Department of Water Resources, 2003). The study unit also consists of all areas outside defined groundwater basins that are within 3 kilometers of a public-supply well. The study unit was separated, based primarily on hydrogeologic settings, into four study areas: Temecula Valley, Warner Valley, Alluvial Basins, and Hard Rock (Wright and others, 2005). The sampling density for the Hard Rock study area, which consists of areas outside of groundwater basins, was much lower than for the other study areas. Consequently, aquifer proportions for the Hard Rock study area are not used to calculate the aquifer proportions shown by the pie charts. An assessment of groundwater quality for the Hard Rock study area can be found in Wright and Belitz, 2011. The temperatures in the coastal part of the study unit are mild with dry summers, moist winters, and an average annual rainfall of about 10 inches. The temperatures in the mountainous eastern part of the study unit are cooler than in the coastal part, with an annual precipitation of about 45 inches that occurs mostly in the winter. The primary aquifers consist of Quaternary-age alluvium and weathered bedrock in the Temecula Valley, Warner Valley, and Alluvial Basins study areas, whereas in the Hard Rock study area the primary aquifers consist mainly of fractured and decomposed granite of Mesozoic age. The primary aquifers are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health (CDPH) database. Public-supply wells typically are drilled to depths between 200 and 700 feet, consist of solid casing from the land surface to a depth of about 60 to 170 feet, and are perforated, or consist of an open hole, below the solid casing. Water quality in the shallow and deep parts of the aquifer system may differ from water quality in the primary aquifers. Municipal water use accounts for approximately 70 percent of water used in the study unit; the majority of the remainder is used for agriculture, industry, and commerce. Groundwater accounts for approximately 8 percent of the municipal supply, and surface water, the majority of which is imported, accounts for the rest. Recharge to groundwater occurs through stream-channel infiltration from rivers and their tributaries, infiltration in engineered recharge basins, and infiltration of water from precipitation and irrigation. The primary source of discharge is water pumped from wells.

Groundwater resources of the East Mountain area, Bernalillo, Sandoval, Santa Fe, and Torrance Counties, New Mexico, 2005

USGS Publications Warehouse

Bartolino, James R.; Anderholm, Scott K.; Myers, Nathan C.

2010-01-01

The groundwater resources of about 400 square miles of the East Mountain area of Bernalillo, Sandoval, Santa Fe, and Torrance Counties in central New Mexico were evaluated by using groundwater levels and water-quality analyses, and updated geologic mapping. Substantial development in the study area (population increased by 11,000, or 50 percent, from 1990 through 2000) has raised concerns about the effects of growth on water resources. The last comprehensive examination of the water resources of the study area was done in 1980-this study examines a slightly different area and incorporates data collected in the intervening 25 years. The East Mountain area is geologically and hydrologically complex-in addition to the geologic units, such features as the Sandia Mountains, Tijeras and Gutierrez Faults, Tijeras syncline and anticline, and the Estancia Basin affect the movement, availability, and water quality of the groundwater system. The stratigraphic units were separated into eight hydrostratigraphic units, each having distinct hydraulic and chemical properties. Overall, the major hydrostratigraphic units are the Madera-Sandia and Abo-Yeso; however, other units are the primary source of supply in some areas. Despite the eight previously defined hydrostratigraphic units, water-level contours were drawn on the generalized regional potentiometric map assuming all hydrostratigraphic units are connected and function as a single aquifer system. Groundwater originates as infiltration of precipitation in upland areas (Sandia, Manzano, and Manzanita Mountains, and the Ortiz Porphyry Belt) and moves downgradient into the Tijeras Graben, Tijeras Canyon, San Pedro synclinorium, and the Hagan, Estancia, and Espanola Basins. The study area was divided into eight groundwater areas defined on the basis of geologic, hydrologic, and geochemical information-Tijeras Canyon, Cedar Crest, Tijeras Graben, Estancia Basin, San Pedro Creek, Ortiz Porphyry Belt, Hagan Basin, and Upper Sandia Mountains. View report for unabridged abstract.

Hydrogeologic framework, groundwater movement, and water budget in the Chimacum Creek basin and vicinity, Jefferson County, Washington

USGS Publications Warehouse

Jones, Joseph L.; Welch, Wendy B.; Frans, Lonna M.; Olsen, Theresa D.

2011-01-01

This report presents information used to characterize the groundwater flow system in the Chimacum Creek basin. It includes descriptions of the geology and hydrogeologic framework; groundwater recharge and discharge; groundwater levels and flow directions; seasonal fluctuations in groundwater level; interactions between aquifers and the surface-water system; and a groundwater budget. The study area covers 124 square miles in northeastern Jefferson County, Washington, and includes the Chimacum Creek basin, which drains an area of about 37 square miles. The area is underlain by a north-thickening sequence of unconsolidated glacial and interglacial deposits that overlie sedimentary and igneous bedrock units that crop out along the margins and western interior of the study area. Six hydrogeologic units consisting of unconsolidated aquifers and confining units, along with an underlying bedrock unit, were identified. A surficial hydrogeologic map was developed and used with well information from 187 drillers' logs to construct 4 hydrogeologic sections, and maps showing the extent and thickness of the units. Natural recharge was estimated using precipitation-recharge relation regression equations developed for western Washington, and estimates were calculated for return flow from data on domestic indoor and outdoor use and irrigated agriculture. Results from synoptic streamflow measurements and water table elevations determined from monthly measurements at monitoring wells are presented and compared with those from a study conducted during 2002-03. A water budget was calculated comprising long-term average recharge, domestic public-supply withdrawals and return flow, self-supplied domestic withdrawals and return flow, and irrigated agricultural withdrawals and return flow.

Groundwater quality in the Bear Valley and Lake Arrowhead Watershed, California

USGS Publications Warehouse

Mathany, Timothy; Burton, Carmen; Fram, Miranda S.

2017-06-20

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The Bear Valley and Lake Arrowhead Watershed study areas in southern California compose one of the study units being evaluated.

Ground-water discharge determined from estimates of evapotranspiration, Death Valley regional flow system, Nevada and California

USGS Publications Warehouse

Laczniak, Randell J.; Smith, J. LaRue; Elliott, Peggy E.; DeMeo, Guy A.; Chatigny, Melissa A.; Roemer, Gaius J.

2001-01-01

The Death Valley regional flow system (DVRFS) is one of the larger ground-water flow systems in the southwestern United States and includes much of southern Nevada and the Death Valley region of eastern California. Centrally located within the ground-water flow system is the Nevada Test Site (NTS). The NTS, a large tract covering about 1,375 square miles, historically has been used for testing nuclear devices and currently is being studied as a potential repository for the long-term storage of high-level nuclear waste generated in the United States. The U.S. Department of Energy, as mandated by Federal and State regulators, is evaluating the risk associated with contaminants that have been or may be introduced into the subsurface as a consequence of any past or future activities at the NTS. Because subsurface contaminants can be transported away from the NTS by ground water, components of the ground-water budget are of great interest. One such component is regional ground-water discharge. Most of the ground water leaving the DVRFS is limited to local areas where geologic and hydrologic conditions force ground water upward toward the surface to discharge at springs and seeps. Available estimates of ground-water discharge are based primarily on early work done as part of regional reconnaissance studies. These early efforts covered large, geologically complex areas and often applied substantially different techniques to estimate ground-water discharge. This report describes the results of a study that provides more consistent, accurate, and scientifically defensible measures of regional ground-water losses from each of the major discharge areas of the DVRFS. Estimates of ground-water discharge presented in this report are based on a rigorous quantification of local evapotranspiration (ET). The study identifies areas of ongoing ground-water ET, delineates different ET areas based on similarities in vegetation and soil-moisture conditions, and determines an ET rate for each delineated area. Each area, referred to as an ET unit, generally consists of one or more assemblages of local phreatophytes or a unique moist soil environment. Ten ET units are identified throughout the DVRFS based on differences in spectral-reflectance characteristics. Spectral differences are determined from satellite imagery acquired June 21, 1989, and June 13, 1992. The units identified include areas of open playa, moist bare soils, sparse to dense vegetation, and open water. ET rates estimated for each ET unit range from a few tenths of a foot per year for open playa to nearly 9 feet per year for open water. Mean annual ET estimates are computed for each discharge area by summing estimates of annual ET from each ET unit within a discharge area. The estimate of annual ET from each ET unit is computed as the product of an ET unit's acreage and estimated ET rate. Estimates of mean annual ET range from 450 acre-feet in the Franklin Well area to 30,000 acre-feet in Sarcobatus Flat. Ground-water discharge is estimated as annual ET minus that part of ET attributed to local precipitation. Mean annual ground-water discharge estimates range from 350 acre-feet in the Franklin Well area to 18,000 acre-feet in Ash Meadows. Generally, these estimates are greater for the northern discharge areas (Sarcobatus Flat and Oasis Valley) and less for the southern discharge areas (Franklin Lake, Shoshone area, and Tecopa/ California Valley area) than those previously reported.

Nitrate in groundwater of the United States, 1991-2003

USGS Publications Warehouse

Burow, Karen R.; Nolan, Bernard T.; Rupert, Michael G.; Dubrovsky, Neil M.

2010-01-01

An assessment of nitrate concentrations in groundwater in the United States indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high N inputs. During 1991-2003, 5101 wells were sampled in 51 study areas throughout the U.S. as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program. The well networks reflect the existing used resource represented by domestic wells in major aquifers (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations were highest in shallow groundwater beneath agricultural land use in areas with well-drained soils and oxic geochemical conditions. Nitrate concentrations were lowest in deep groundwater where groundwater is reduced, or where groundwater is older and hence concentrations reflect historically low N application rates. Classification and regression tree analysis was used to identify the relative importance of N inputs, biogeochemical processes, and physical aquifer properties in explaining nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that dissolved iron concentrations explained most of the variation in groundwater nitrate concentration, followed by manganese, calcium, farm N fertilizer inputs, percent well-drained soils, and dissolved oxygen. Overall, nitrate concentrations in groundwater are most significantly affected by redox conditions, followed by nonpoint-source N inputs. Other water-quality indicators and physical variables had a secondary influence on nitrate concentrations.

Nitrate-nitrogen contamination in groundwater: Spatiotemporal variation and driving factors under cropland in Shandong Province, China

NASA Astrophysics Data System (ADS)

Liu, J.; Jiang, L. H.; Zhang, C. J.; Li, P.; Zhao, T. K.

2017-08-01

High groundwater nitrate-N is a serious problem especially in highly active agricultural areas. In study, the concentration and spatialtemporal distribution of groundwater nitrate-N under cropland in Shandong province were assessed by statistical and geostatistical techniques. Nitrate-N concentration reached a maximum of 184.60 mg L-1 and 29.5% of samples had levels in excess of safety threshold concentration (20 mg L-1). The median nitrate-N contents after rainy season were significantly higher than those before rainy season, and decreased with increasing groundwater depth. Nitrate-N under vegetable and orchard area are significantly higher than ones under grain. The kriging map shows that groundwater nitrate-N has a strong spatial variability. Many districts, such as Weifang, Linyi in Shandong province are heavily contaminated with nitrate-N. However, there are no significant trends of NO3 --N for most cities. Stepwise regression analysis showed influencing factors are different for the groundwater in different depth. But overall, vegetable yield per unit area, percentages of orchard area, per capita agricultural production, unit-area nitrogen fertilizer, livestock per unit area, percentages of irrigation areas, population per unit area and annual mean temperature are significant variables for groundwater nitrate-N variation.

Ground-water data collected in the Missouri River Basin units in Kansas during 1954

USGS Publications Warehouse

Mason, B.J.; Loye, Linda

1955-01-01

Ground water studies in the Missouri River basin were begun by the United States Geological Survey during the fall of 1945 as a part of a program for the development of the resources of the basin by the United States Bureau of  Reclamation and other federal agencies. The studies of ground-water resources in the part of Kansas that lies within the Missouri River basin have been coordinated with the cooperative program of ground-water studies which were already being made in Kansas by the U.S Geological Survey, the Kansas State Geological Survey, the Division of Sanitation of the Kansas Board of Health and the Division of Water Resources of the Kansas State Board of Agriculture.  

Groundwater quality in the Western San Joaquin Valley study unit, 2010: California GAMA Priority Basin Project

USGS Publications Warehouse

Fram, Miranda S.

2017-06-09

Water quality in groundwater resources used for public drinking-water supply in the Western San Joaquin Valley (WSJV) was investigated by the USGS in cooperation with the California State Water Resources Control Board (SWRCB) as part of its Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project. The WSJV includes two study areas: the Delta–Mendota and Westside subbasins of the San Joaquin Valley groundwater basin. Study objectives for the WSJV study unit included two assessment types: (1) a status assessment yielding quantitative estimates of the current (2010) status of groundwater quality in the groundwater resources used for public drinking water, and (2) an evaluation of natural and anthropogenic factors that could be affecting the groundwater quality. The assessments characterized the quality of untreated groundwater, not the quality of treated drinking water delivered to consumers by water distributors.The status assessment was based on data collected from 43 wells sampled by the U.S. Geological Survey for the GAMA Priority Basin Project (USGS-GAMA) in 2010 and data compiled in the SWRCB Division of Drinking Water (SWRCB-DDW) database for 74 additional public-supply wells sampled for regulatory compliance purposes between 2007 and 2010. To provide context, concentrations of constituents measured in groundwater were compared to U.S. Environmental Protection Agency (EPA) and SWRCB-DDW regulatory and non-regulatory benchmarks for drinking-water quality. The status assessment used a spatially weighted, grid-based method to estimate the proportion of the groundwater resources used for public drinking water that has concentrations for particular constituents or class of constituents approaching or above benchmark concentrations. This method provides statistically unbiased results at the study-area scale within the WSJV study unit, and permits comparison of the two study areas to other areas assessed by the GAMA Priority Basin Project statewide.Groundwater resources used for public drinking water in the WSJV study unit are among the most saline and most affected by high concentrations of inorganic constituents of all groundwater resources used for public drinking water that have been assessed by the GAMA Priority Basin Project statewide. Among the 82 GAMA Priority Basin Project study areas statewide, the Delta–Mendota study area ranked above the 90th percentile for aquifer-scale proportions of groundwater resources having concentrations of total dissolved solids (TDS), sulfate, chloride, manganese, boron, chromium(VI), selenium, and strontium above benchmarks, and the Westside study area ranked above the 90th percentile for TDS, sulfate, manganese, and boron.In the WSJV study unit as a whole, one or more inorganic constituents with regulatory or non-regulatory, health-based benchmarks were present at concentrations above benchmarks in about 53 percent of the groundwater resources used for public drinking water, and one or more organic constituents with regulatory health-based benchmarks were detected at concentrations above benchmarks in about 3 percent of the resource. Individual constituents present at concentrations greater than health-based benchmarks in greater than 2 percent of groundwater resources used for public drinking water included: boron (51 percent, SWRCB-DDW notification level), chromium(VI) (25 percent, SWRCB-DDW maximum contaminant level (MCL)), arsenic (10 percent, EPA MCL), strontium (5.1 percent, EPA Lifetime health advisory level (HAL)), nitrate (3.9 percent, EPA MCL), molybdenum (3.8 percent, EPA HAL), selenium (2.6 percent, EPA MCL), and benzene (2.6 percent, SWRCB-DDW MCL). In addition, 50 percent of the resource had TDS concentrations greater than non-regulatory, aesthetic-based SWRCB-DDW upper secondary maximum contaminant level (SMCL), and 44 percent had manganese concentrations greater than the SWRCB-DDW SMCL.Natural and anthropogenic factors that could affect the groundwater quality were evaluated by using results from statistical testing of associations between constituent concentrations and values of potential explanatory factors, inferences from geochemical and age-dating tracer results, and by considering the water-quality results in the context of the hydrogeologic setting of the WSJV study unit.Natural factors, particularly the lithologies of the source areas for groundwater recharge and of the aquifers, were the dominant factors affecting groundwater quality in most of the WSJV study unit. However, where groundwater resources used for public supply included groundwater recharged in the modern era, mobilization of constituents by recharge of water used for irrigation also affected groundwater quality. Public-supply wells in the Westside study area had a median depth of 305 m and primarily tapped groundwater recharged hundreds to thousands of years ago, whereas public-supply wells in the Delta–Mendota study area had a median depth of 85 m and primarily tapped either groundwater recharged within the last 60 years or groundwater consisting of mixtures of this modern recharge and older recharge.Public-supply wells in the WSJV study unit are screened in the Tulare Formation and zones above and below the Corcoran Clay Member are used. The Tulare Formation primarily consists of alluvial sediments derived from the Coast Ranges to the west, except along the valley trough at the eastern margin of the WSJV study unit where the Tulare Formation consists of fluvial sands derived from the Sierra Nevada to the east. Groundwater from wells screened in the Sierra Nevada sands had manganese-reducing or manganese- and iron-reducing oxidation-reduction (redox) conditions. These redox conditions commonly were associated with elevated arsenic or molybdenum concentrations, and the dominance of arsenic(III) in the dissolved arsenic supports reductive dissolution of iron and manganese oxyhydroxides as the mechanism. In addition, groundwater from many wells screened in Sierra Nevada sands contained low concentrations of nitrite or ammonium, indicating reduction of nitrate by denitrification or dissimilatory processes, respectively.Geology of the Coast Ranges westward of the study unit strongly affects groundwater quality in the WSJV. Elevated concentrations of TDS, sulfate, boron, selenium and strontium in groundwater were primarily associated with aquifer sediments and recharge derived from areas of the Coast Ranges dominated by Cretaceous-to-Miocene age, organic-rich, reduced marine shales, known as the source of selenium in WSJV soils, surface water, and groundwater. Low sulfur-isotopic values (δ34S) of dissolved sulfate indicate that the sulfate was largely derived from oxidation of biogenic pyrite from the shales, and correlations with trace element concentrations, geologic setting, and groundwater geochemical modeling indicated that distributions of sulfate, strontium, and selenium in groundwater were controlled by dissolution of secondary sulfate minerals in soils and sediments.Elevated concentrations of chromium(VI) were primarily associated with aquifer sediments and recharge derived from areas of the Coast Ranges dominated by the Franciscan Complex and ultramafic rocks. The Franciscan Complex also has boron-rich, sodium-chloride dominated hydrothermal fluids that contribute to elevated concentrations of boron and TDS.Groundwater from wells screened in Coast Ranges alluvium was primarily oxic and relatively alkaline (median pH value of 7.55) in the Delta–Mendota study area, and primarily nitrate-reducing or suboxic and alkaline (median pH value of 8.4) in the Westside study area. Many groundwater samples from those wells have elevated concentrations of arsenic(V), molybdenum, selenium, or chromium(VI), consistent with desorption of metal oxyanions from mineral surfaces under those geochemical conditions.High concentrations of benzene were associated with deep wells located in the vicinity of petroleum deposits at the southern end of the Westside study area. Groundwater from these wells had premodern age and anoxic geochemical conditions, and the ratios among concentrations of hydrocarbon constituents were different from ratios found in fuels and combustion products, which is consistent with a geogenic source for the benzene rather than contamination from anthropogenic sources.Water stable-isotope compositions, groundwater recharge temperatures, and groundwater ages were used to infer four types of groundwater: (1) groundwater derived from natural recharge of water from major rivers draining the Sierra Nevada; (2) groundwater primarily derived from natural recharge of water from Coast Ranges runoff; (3) groundwater derived from recharge of pumped groundwater applied to the land surface for irrigation; and (4) groundwater derived from recharge during a period of much cooler paleoclimate. Water previously used for irrigation was found both above and below the Corcoran Clay, supporting earlier inferences that this clay member is no longer a robust confining unit.Recharge of water used for irrigation has direct and indirect effects on groundwater quality. Elevated nitrate concentrations and detections of herbicides and fumigants in the Delta–Mendota study area generally were associated with greater agricultural land use near the well and with water recharged during the last 60 years. However, the extent of the groundwater resource affected by agricultural sources of nitrate was limited by groundwater redox conditions sufficient to reduce nitrate. The detection frequency of perchlorate in Delta–Mendota groundwater was greater than expected for natural conditions. Perchlorate, nitrate, selenium, and strontium concentrations were correlated with one another and were greater in groundwater inferred to be recharge of previously pumped groundwater used for irrigation. The source of the perchlorate, selenium, and strontium appears to be salts deposited in the soils and sediments of the arid WSJV that are dissolved and flushed into groundwater by the increased amount of recharge caused by irrigation. In the Delta–Mendota study area, the groundwater with elevated concentrations of selenium was found deeper in the aquifer system than it was reported by a previous study 25 years earlier, suggesting that this transient front of groundwater with elevated concentrations of constituents derived from dissolution of soil salts by irrigation recharge is moving down through the aquifer system and is now reaching the depth zone used for public drinking water supply.

GREAT (Groundwater Resources & Educational Activities for Teaching). An Iowa Project for Earth/Life/General Science, 7th-9th Grades.

ERIC Educational Resources Information Center

George, Gail, Ed.

These resource materials are a part of a larger plan for groundwater education, as detailed in the Iowa Groundwater Education Strategy. The six units are arranged in priority order. The first unit covers the basics of groundwater and hydrogeology in Iowa. The other five units cover Iowa's groundwater issues in priority order, as outlined in the…

Groundwater quality in the Northern Sacramento Valley, California

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.; Belitz, Kenneth

2011-01-01

Groundwater provides more than 40 percent of California's drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State's groundwater quality and increases public access to groundwater-quality information. The Northern Sacramento Valley is one of the study units being evaluated.

Groundwater quality in the Southern Sacramento Valley, California

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.; Belitz, Kenneth

2011-01-01

Groundwater provides more than 40 percent of California's drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State's groundwater quality and increases public access to groundwater-quality information. The Southern Sacramento Valley is one of the study units being evaluated.

Groundwater quality in the Santa Barbara Coastal Plain, California

USGS Publications Warehouse

Davis, Tracy A.; Belitz, Kenneth

2016-10-03

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California established the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The Santa Barbara Coastal Plain is one of the study units.

Groundwater quality in the Klamath Mountains, California

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.

2014-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The Klamath Mountains constitute one of the study units being evaluated.

A conceptual model of the hydrogeologic framework, geochemistry, and groundwater-flow system of the Edwards-Trinity and related aquifers in the Pecos County region, Texas

USGS Publications Warehouse

Bumgarner, Johnathan R.; Stanton, Gregory P.; Teeple, Andrew; Thomas, Jonathan V.; Houston, Natalie A.; Payne, Jason; Musgrove, MaryLynn

2012-01-01

A conceptual model of the hydrogeologic framework, geochemistry, and groundwater-flow system of the Edwards-Trinity and related aquifers, which include the Pecos Valley, Igneous, Dockum, Rustler, and Capitan Reef aquifers, was developed as the second phase of a groundwater availability study in the Pecos County region in west Texas. The first phase of the study was to collect and compile groundwater, surface-water, water-quality, geophysical, and geologic data in the area. The third phase of the study involves a numerical groundwater-flow model of the Edwards-Trinity aquifer in order to simulate groundwater conditions based on various groundwater-withdrawal scenarios. Resource managers plan to use the results of the study to establish management strategies for the groundwater system. The hydrogeologic framework is composed of the hydrostratigraphy, structural features, and hydraulic properties of the groundwater system. Well and geophysical logs were interpreted to define the top and base surfaces of the Edwards-Trinity aquifer units. Elevations of the top and base of the Edwards-Trinity aquifer generally decrease from the southwestern part of the study area to the northeast. The thicknesses of the Edwards-Trinity aquifer units were calculated using the interpolated top and base surfaces of the hydrostratigraphic units. Some of the thinnest sections of the aquifer were in the eastern part of the study area and some of the thickest sections were in the Pecos, Monument Draw, and Belding-Coyanosa trough areas. Normal-fault zones, which formed as growth and collapse features as sediments were deposited along the margins of more resistant rocks and as overlying sediments collapsed into the voids created by the dissolution of Permian-age evaporite deposits, were delineated based on the interpretation of hydrostratigraphic cross sections. The lowest aquifer transmissivity values were measured in the eastern part of the study area; the highest transmissivity values were measured in a faulted area of the Monument Draw trough. Hydraulic conductivity values generally exhibited the same trends as the transmissivity values. Groundwater-quality data and groundwater-level data were used in context with the hydrogeologic framework to assess the chemical characteristics of water from different sources, regional groundwater-flow paths, recharge sources, the mixing of water from different sources, and discharge in the study area. Groundwater-level altitudes generally decrease from southwest to northeast and regional groundwater flow is from areas of recharge south and west to the north and northeast. Four principal sources of recharge to the Edwards-Trinity aquifer were identified: (1) regional flow that originated as recharge northwest of the study area, (2) runoff from the Barilla, Davis, and Glass Mountains, (3) return flow from irrigation, and (4) upwelling from deeper aquifers. Results indicated Edwards-Trinity aquifer water in the study area was dominated by mineralized, regional groundwater flow that most likely recharged during the cooler, wetter climates of the Pleistocene with variable contributions of recent, local recharge. Groundwater generally flows into the down-dip extent of the Edwards-Trinity aquifer where it discharges into overlying or underlying aquifer units, discharges from springs, discharges to the Pecos River, follows a regional flow path east out of the study area, or is withdrawn by groundwater wells. Structural features such as mountains, troughs, and faults play a substantial role in the distribution of recharge, local and regional groundwater flow, spring discharge, and aquifer interaction.

Hydrogeologic framework and hydrologic budget components of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

USGS Publications Warehouse

Kahle, S.C.; Morgan, D.S.; Welch, W.B.; Ely, D.M.; Hinkle, S.R.; Vaccaro, J.J.; Orzol, L.L.

2011-01-01

The Columbia Plateau Regional Aquifer System (CPRAS) covers an area of about 44,000 square miles in a structural and topographic basin within the drainage of the Columbia River in Washington, Oregon, and Idaho. The primary aquifers are basalts of the Columbia River Basalt Group (CRBG) and overlying sediment. Eighty percent of the groundwater use in the study area is for irrigation, in support of a $6 billion per year agricultural economy. Water-resources issues in the Columbia Plateau include competing agricultural, domestic, and environmental demands. Groundwater levels were measured in 470 wells in 1984 and 2009; water levels declined in 83 percent of the wells, and declines greater than 25 feet were measured in 29 percent of the wells. Conceptually, the system is a series of productive basalt aquifers consisting of permeable interflow zones separated by less permeable flow interiors; in places, sedimentary aquifers overly the basalts. The aquifer system of the CPRAS includes seven hydrogeologic units-the overburden aquifer, three aquifer units in the permeable basalt rock, two confining units, and a basement confining unit. The overburden aquifer includes alluvial and colluvial valley-fill deposits; the three basalt units are the Saddle Mountains, Wanapum, and Grande Ronde Basalts and their intercalated sediments. The confining units are equivalent to the Saddle Mountains-Wanapum and Wanapum-Grande Ronde interbeds, referred to in this study as the Mabton and Vantage Interbeds, respectively. The basement confining unit, referred to as Older Bedrock, consists of pre-CRBG rocks that generally have much lower permeabilities than the basalts and are considered the base of the regional flow system. Based on specific-capacity data, median horizontal hydraulic conductivity (Kh) values for the overburden, basalt units, and bedrock are 161, 70, and 6 feet per day, respectively. Analysis of oxygen isotopes in water and carbon isotopes in dissolved inorganic carbon from groundwater samples indicates that groundwater in the CPRAS ranges in age from modern (10,000 years). The oldest groundwater resides in deep, downgradient locations indicating that groundwater movement and replenishment in parts of this regional aquifer system have operated on long timescales under past natural conditions, which is consistent with the length and depth of long flow paths in the system. The mean annual recharge from infiltration of precipitation for the 23-year period 1985-2007 was estimated to be 4.6 inches per year (14,980 cubic feet per second) using a polynomial regression equation based on annual precipitation and the results of recharge modeling done in the 1980s. A regional-scale hydrologic budget was developed using a monthly SOil WATer (SOWAT) Balance model to estimate irrigation-water demand, groundwater flux (recharge or discharge), direct runoff, and soil moisture within irrigated areas. Mean monthly irrigation throughout the study area peaks in July at 1.6 million acre-feet (MAF), of which 0.45 and 1.15 MAF are from groundwater and surface-water sources, respectively. Annual irrigation water use in the study area averaged 5.3 MAF during the period 1985-2007, with 1.4 MAF (or 26 percent) supplied from groundwater and 3.9 MAF supplied from surface water. Mean annual recharge from irrigation return flow in the study area was 4.2 MAF (1985-2007) with 2.1 MAF (50 percent) occurring within the predominately surface-water irrigated regions of the study area. Annual groundwater-use estimates were made for public supply, self-supplied domestic, industrial, and other uses for the period 1984 through 2009. Public supply groundwater use within the study area increased from 200,600 acre-feet per year (acre-ft/yr) in 1984 to 269,100 acre-ft/yr in 2009. Domestic self-supplied groundwater use increased from 54,580 acre-ft/yr in 1984 to 71,160 acre-ft/yr in 2009. Industrial groundwater use decreased from 53,390 acre-ft/yr in 1984 t

Groundwater-quality data in the Cascade Range and Modoc Plateau study unit, 2010-Results from the California GAMA Program

USGS Publications Warehouse

Shelton, Jennifer L.; Fram, Miranda S.; Belitz, Kenneth

2013-01-01

Groundwater quality in the 39,000-square-kilometer Cascade Range and Modoc Plateau (CAMP) study unit was investigated by the U.S. Geological Survey (USGS) from July through October 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The CAMP study unit is the thirty-second study unit to be sampled as part of the GAMA PBP. The GAMA CAMP study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer system is defined as that part of the aquifer corresponding to the open or screened intervals of wells listed in the California Department of Public Health (CDPH) database for the CAMP study unit. The quality of groundwater in shallow or deep water-bearing zones may differ from the quality of groundwater in the primary aquifer system; shallow groundwater may be more vulnerable to surficial contamination. In the CAMP study unit, groundwater samples were collected from 90 wells and springs in 6 study areas (Sacramento Valley Eastside, Honey Lake Valley, Cascade Range and Modoc Plateau Low Use Basins, Shasta Valley and Mount Shasta Volcanic Area, Quaternary Volcanic Areas, and Tertiary Volcanic Areas) in Butte, Lassen, Modoc, Plumas, Shasta, Siskiyou, and Tehama Counties. Wells and springs were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells). Groundwater samples were analyzed for field water-quality indicators, organic constituents, perchlorate, inorganic constituents, radioactive constituents, and microbial indicators. Naturally occurring isotopes and dissolved noble gases also were measured to provide a dataset that will be used to help interpret the sources and ages of the sampled groundwater in subsequent reports. In total, 221 constituents were investigated for this study. Three types of quality-control samples (blanks, replicates, and matrix spikes) were collected at approximately 10 percent of the wells in the CAMP study unit, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Blanks rarely contained detectable concentrations of any constituent, suggesting that contamination from sample collection procedures was not a significant source of bias in the data for the groundwater samples. Replicate samples generally were within the limits of acceptable analytical reproducibility. Matrix-spike recoveries were within the acceptable range (70 to 130 percent) for approximately 90 percent of the compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, untreated groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is served to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-regulatory benchmarks established for aesthetic concerns by CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. All organic constituents and most inorganic constituents that were detected in groundwater samples from the 90 grid wells in the CAMP study unit were detected at concentrations less than drinking-water benchmarks. Of the 148 organic constituents analyzed, 27 were detected in groundwater samples; concentrations of all detected constituents were less than regulatory and nonregulatory health-based benchmarks, and all were less than 1/10 of benchmark levels. One or more organic constituents were detected in 52 percent of the grid wells in the CAMP study unit: VOCs were detected in 30 percent, and pesticides and pesticide degradates were detected in 31 percent. Trace elements, major ions, nutrients, and radioactive constituents were sampled for at 90 grid wells in the CAMP study unit, and most detected concentrations were less than health-based benchmarks. Exceptions include three detections of arsenic greater than the USEPA maximum contaminant level (MCL-US) of 10 micrograms per liter (µg/L), two detections of boron greater than the CDPH notification level (NL-CA) of 1,000 µg/L, two detections of molybdenum greater than the USEPA lifetime health advisory level (HAL-US) of 40 µg/L, two detections of vanadium greater than the CDPH notification level (NL-CA) of 50 µg/L, one detection of nitrate, as nitrogen, greater than the MCL-US of 10 milligrams per liter (mg/L), two detections of uranium greater than the MCL-US of 30 µg/L and the MCL-CA of 20 picocuries per liter (pCi/L), one detection of radon-222 greater than the proposed MCL-US of 4,000 pCi/L, and two detections of gross alpha particle activity greater than the MCL-US of 15 pCi/L. Results for inorganic constituents with non-regulatory benchmarks set for aesthetic concerns showed that iron concentrations greater than the CDPH secondary maximum contaminant level (SMCL-CA) of 300 µg/L were detected in four grid wells. Manganese concentrations greater than the SMCL-CA of 50 µg/L were detected in nine grid wells. Chloride and TDS were detected at concentrations greater than the upper SMCL-CA benchmarks of 500 mg/L and 1,000 mg/L, respectively, in one grid well. Microbial indicators (total coliform and Escherichia coli [E. coli]) were detected in 11 percent of the 83 grid wells sampled for these analyses in the CAMP study unit. The presence of total coliform was detected in nine grid wells, and the presence of E. coli was detected in one of these same grid wells.

Groundwater quality in the South Coast Range Coastal groundwater basins, California

USGS Publications Warehouse

Burton, Carmen A.; Belitz, Kenneth

2013-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project (PBP) of the GAMA Program provides a comprehensive assessment of the State’s untreated groundwater quality and increases public access to groundwater-quality information. The coastal basins in the Southern Coast Ranges constitute one of the study units being evaluated.

Evaluation of radon occurrence in groundwater from 16 geologic units in Pennsylvania, 1986–2015, with application to potential radon exposure from groundwater and indoor air

USGS Publications Warehouse

Gross, Eliza L.

2017-05-11

Results from 1,041 groundwater samples collected during 1986‒2015 from 16 geologic units in Pennsylvania, associated with 25 or more groundwater samples with concentrations of radon-222, were evaluated in an effort to identify variations in radon-222 activities or concentrations and to classify potential radon-222 exposure from groundwater and indoor air. Radon-222 is hereafter referred to as “radon.” Radon concentrations in groundwater greater than or equal to the proposed U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) for public-water supply systems of 300 picocuries per liter (pCi/L) were present in about 87 percent of the water samples, whereas concentrations greater than or equal to the proposed alternative MCL (AMCL) for public water-supply systems of 4,000 pCi/L were present in 14 percent. The highest radon concentrations were measured in groundwater from the schists, gneisses, and quartzites of the Piedmont Physiographic Province.In this study, conducted by the U.S. Geological Survey in cooperation with the Pennsylvania Department of Health and the Pennsylvania Department of Environmental Protection, groundwater samples were aggregated among 16 geologic units in Pennsylvania to identify units with high median radon concentrations in groundwater. Graphical plots and statistical tests were used to determine variations in radon concentrations in groundwater and indoor air. Median radon concentrations in groundwater samples and median radon concentrations in indoor air samples within the 16 geologic units were classified according to proposed and recommended regulatory limits to explore potential radon exposure from groundwater and indoor air. All of the geologic units, except for the Allegheny (Pa) and Glenshaw (Pcg) Formations in the Appalachian Plateaus Physiographic Province, had median radon concentrations greater than the proposed EPA MCL of 300 pCi/L, and the Peters Creek Schist (Xpc), which is in the Piedmont Physiographic Province, had a median radon concentration greater than the EPA proposed AMCL of 4,000 pCi/L. Median concentrations of radon in groundwater and indoor air were determined to differ significantly among the geologic units (Kruskal-Wallis test, significance probability, p<0.001), and Tukey’s test indicated that radon concentrations in groundwater and indoor air in the Peters Creek Schist (Xpc) were significantly higher than those in the other units. Also, the Peters Creek Schist (Xpc) was determined to be the area with highest potential of radon exposure from groundwater and indoor air and one of two units with the highest percentage of population assumed to be using domestic self-supplied water (81 percent), which puts the population at greater potential of exposure to radon from groundwater.Potential radon exposure determined from classification of geologic units by median radon concentrations in groundwater and indoor air according to proposed and recommended regulatory limits is useful for drawing general conclusions about the presence, variation, and potential radon exposure in specific geologic units, but the associated data and maps have limitations. The aggregated indoor air radon data have spatial accuracy limitations owing to imprecision of geocoded test locations. In addition, the associated data describing geologic units and the public water supplier’s service areas have spatial and interpretation accuracy limitations. As a result, data and maps associated with this report are not recommended for use in predicting individual concentrations at specific sites nor for use as a decision-making tool for property owners to decide whether to test for radon concentrations at specific locations. Instead, the data and maps are meant to promote awareness regarding potential radon exposure in Pennsylvania and to point out data gaps that exist throughout the State.

Groundwater quality in the Tahoe and Martis Basins, California

USGS Publications Warehouse

Fram, Miranda S.; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California's drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State's groundwater quality and increases public access to groundwater-quality information. The Tahoe and Martis Basins and surrounding watersheds constitute one of the study units being evaluated.

Groundwater quality in the South Coast Interior Basins, California

USGS Publications Warehouse

Parsons, Mary C.; Belitz, Kenneth

2014-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s untreated groundwater quality and increases public access to groundwater-quality information. The South Coast Interior Basins constitute one of the study units being evaluated.

Groundwater quality in the western San Joaquin Valley, California

USGS Publications Warehouse

Fram, Miranda S.

2017-06-09

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The Western San Joaquin Valley is one of the study units being evaluated. 

Groundwater-quality data in the Bear Valley and Selected Hard Rock Areas study unit, 2010: Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Belitz, Kenneth

2013-01-01

Groundwater quality in the 112-square-mile Bear Valley and Selected Hard Rock Areas (BEAR) study unit was investigated by the U.S. Geological Survey (USGS) from April to August 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The BEAR study unit was the thirty-first study unit to be sampled as part of the GAMA-PBP. The GAMA Bear Valley and Selected Hard Rock Areas study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system and to facilitate statistically consistent comparisons of untreated groundwater quality throughout California. The primary aquifer system is defined as the zones corresponding to the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the BEAR study unit. Groundwater quality in the primary aquifer system may differ from the quality in the shallow or deep water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. In the BEAR study unit, groundwater samples were collected from two study areas (Bear Valley and Selected Hard Rock Areas) in San Bernardino County. Of the 38 sampling sites, 27 were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the primary aquifer system in the study unit (grid sites), and the remaining 11 sites were selected to aid in the understanding of the potential groundwater-quality issues associated with septic tank use and with ski areas in the study unit (understanding sites). The groundwater samples were analyzed for organic constituents (volatile organic compounds [VOCs], pesticides and pesticide degradates, pharmaceutical compounds, and wastewater indicator compounds [WICs]), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), and inorganic constituents (trace elements, nutrients, dissolved organic carbon [DOC], major and minor ions, silica, total dissolved solids [TDS], alkalinity, and arsenic and iron species), and uranium and other radioactive constituents (radon-222 and activities of tritium and carbon-14). Isotopic tracers (of hydrogen and oxygen in water, of nitrogen and oxygen in dissolved nitrate, of dissolved boron, isotopic ratios of strontium in water, and of carbon in dissolved inorganic carbon) and dissolved noble gases (argon, helium-4, krypton, neon, and xenon) were measured to help identify the sources and ages of sampled groundwater. In total, groundwater samples were analyzed for 289 unique constituents and 8 water-quality indicators in the BEAR study unit. Quality-control samples (blanks, replicate pairs, or matrix spikes) were collected at 13 percent of the sites in the BEAR study unit, and the results for these samples were used to evaluate the quality of the data from the groundwater samples. Blank samples rarely contained detectable concentrations of any constituent, indicating that contamination from sample collection or analysis was not a significant source of bias in the data for the groundwater samples. Replicate pair samples all were within acceptable limits of variability. Matrix-spike sample recoveries were within the acceptable range (70 to 130 percent) for approximately 84 percent of the compounds. This study did not evaluate the quality of water delivered to consumers. After withdrawal, groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is delivered to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-health-based benchmarks established for aesthetic concerns by CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. All concentrations of organic and special-interest constituents from grid sites sampled in the BEAR study unit were less than health-based benchmarks. In total, VOCs were detected in 17 of the 27 grid sites sampled (approximately 63 percent), pesticides and pesticide degradates were detected in 4 grid sites (approximately 15 percent), and perchlorate was detected in 21 grid sites (approximately 78 percent). Inorganic constituents (trace elements, major and minor ions, nutrients, and uranium and other radioactive constituents) were sampled for at 27 grid sites; most concentrations were less than health-based benchmarks. Exceptions include one detection of arsenic greater than the USEPA maximum contaminant level (MCL-US) of 10 micrograms per liter (μg/L), three detections of uranium greater than the MCL-US of 30 μg/L, nine detections of radon-222 greater than the proposed MCL-US of 4,000 picocuries per liter (pCi/L), and one detection of fluoride greater than the CDPH maximum contaminant level (MCL-CA) of 2 milligrams per liter. Concentrations of inorganic constituents with non-health-based benchmarks (iron, manganese, chloride, and TDS) were less than the CDPH secondary maximum contaminant level (SMCL-CA) in most grid sites. Exceptions include two detections of iron greater than the SMCL-CA of 300 μg/L and one detection of manganese greater than the SMCL-CA of 50 μg/L.

Status and understanding of groundwater quality in the North San Francisco Bay Shallow Aquifer study unit, 2012; California GAMA Priority Basin Project (ver. 1.1, February 2018)

USGS Publications Warehouse

Bennett, George L.

2017-07-20

Groundwater quality in the North San Francisco Bay Shallow Aquifer study unit (NSF-SA) was investigated as part of the Priority Basin Project of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is in Marin, Mendocino, Napa, Solano, and Sonoma Counties and included two physiographic study areas: the Valleys and Plains area and the surrounding Highlands area. The NSF-SA focused on groundwater resources used for domestic drinking water supply, which generally correspond to shallower parts of aquifer systems than that of groundwater resources used for public drinking water supply in the same area. The assessments characterized the quality of untreated groundwater, not the quality of drinking water.This study included three components: (1) a status assessment, which characterized the status of the quality of the groundwater resources used for domestic supply for 2012; (2) an understanding assessment, which evaluated the natural and human factors potentially affecting water quality in those resources; and (3) a comparison between the groundwater resources used for domestic supply and those used for public supply.The status assessment was based on data collected from 71 sites sampled by the U.S. Geological Survey for the GAMA Priority Basin Project in 2012. To provide context, concentrations of constituents measured in groundwater were compared to U.S. Environmental Protection Agency (EPA) and California State Water Resources Control Board Division of Drinking Water regulatory and non-regulatory benchmarks for drinking-water quality. The status assessment used a grid-based method to estimate the proportion of the groundwater resources that has concentrations of water-quality constituents approaching or above benchmark concentrations. This method provides statistically unbiased results at the study-area scale and permits comparisons to other GAMA Priority Basin Project study areas.In the NSF-SA study unit as a whole, inorganic constituents with human-health benchmarks were detected at high relative concentrations (RCs) in 27 percent of the shallow aquifer system, and inorganic constituents with secondary maximum contaminant levels (SMCL) were detected at high RCs in 24 percent of the system. The inorganic constituents detected at high RCs were arsenic, boron, fluoride, manganese, nitrate, iron, sulfate, and total dissolved solids (TDS). Organic constituents with human-health benchmarks were detected at high RCs in 1 percent of the shallow aquifer system. Of the 148 organic constituents analyzed, 30 constituents were detected, although only 1, chloroform, had a detection frequency greater than 10 percent.Natural and anthropogenic factors that could affect the groundwater quality were evaluated by using results from statistical testing of associations between constituent concentrations and values of potential explanatory factors. Groundwater age class (modern, mixed, or pre-modern), redox class (oxic or anoxic), aquifer lithology class (metamorphic, sedimentary, or volcanic), and dissolved oxygen concentrations were the explanatory factors that explained distribution patterns of most of the inorganic constituents best. Groundwater classified primarily as pre-modern or mixed in age was associated with higher concentrations of arsenic and fluoride than waters classified as modern. Anoxic or mixed redox conditions were associated with higher concentrations of boron, fluoride, and manganese. Similar patterns of association with explanatory variables were seen for inorganic constituents with aesthetic-based benchmarks detected at high concentrations. Nitrate and perchlorate had higher concentrations in oxic than in the anoxic redox class and were positively correlated with urban land use.The NSF-SA water-quality results were compared to those of the GAMA North San Francisco Bay Public-Supply Aquifer study unit (NSF-PA). The NSF-PA was sampled in 2004 and covers much of the same area as the NSF-SA, but focused on the deeper public-supply aquifer system. The comparison of the NSF-PA to the NSF-SA showed that there were more differences between the Valleys and Plains study areas of the two study units than between the Highlands study areas of the two study units. As expected from the shallower depth of wells, the NSF-SA Valleys and Plains study area had a lesser proportion of pre-modern age groundwater and greater proportion of modern age groundwater than the NSF-PA Valleys and Plains study area. In contrast, well depths and groundwater ages were not significantly different between the two Highlands study areas. Arsenic, manganese, and nitrate were present at high RCs, and perchlorate was detected in greater proportions of the NSF-SA Valleys and Plains study area than the NSF-PA Valleys and Plains study area.

Twenty years of global groundwater research: A Science Citation Index Expanded-based bibliometric survey (1993-2012)

NASA Astrophysics Data System (ADS)

Niu, Beibei; Loáiciga, Hugo A.; Wang, Zhen; Zhan, F. Benjamin; Hong, Song

2014-11-01

A bibliometric analysis was conducted to evaluate groundwater research from different perspectives in the period 1993-2012 based on the Science Citation Index-Expanded (SCIE) database. The bibliometric analysis summarizes output, categorical, geographical, and institutional patterns, as well as research hotspots in global groundwater studies. Groundwater research experienced notable growth in the past two decades. ;Environmental sciences;, ;water resources; and ;multidisciplinary geosciences; were the three major subject categories. The Journal of Hydrology published the largest number of groundwater-related publications in the surveyed period. Major author clusters and research regions are located in the United States, Western Europe, Eastern and Southern Asia, and Eastern Australia. The United States was a leading contributor to global groundwater research with the largest number of independent and collaborative papers, its dominance affirmed by housing 12 of the top 20 most active institutions reporting groundwater-related research. The US Geological Survey, the Chinese Academy of Sciences, and the USDA Agricultural Research Service were the three institutions with the largest number of groundwater-related publications. A keywords analysis revealed that groundwater quality and contamination, effective research technologies, and treatment technologies for water-quality improvement were the main research areas in the study period. Several keywords such as ;arsenic;, ;climate change;, ;fluoride;, ;groundwater management;, ;hydrogeochemistry;, ;uncertainty;, ;numerical modeling;, ;seawater intrusion;, ;adsorption;, ;remote sensing;, ;land use;, ;USA;(as study site), and ;water supply; received dramatically increased attention during the study period, possibly signaling future research trends.

Status and understanding of groundwater quality in the Sierra Nevada Regional study unit, 2008: California GAMA Priority Basin Project

USGS Publications Warehouse

Fram, Miranda S.; Belitz, Kenneth

2014-01-01

Statistical tests were used to evaluate relations between constituent concentrations and potential explanatory factors descriptive of land use, geography, depth, geochemical conditions, and groundwater age. Higher concentrations of trace elements, radioactive constituents, and constituents with aesthetic-based benchmarks generally were associated with anoxic conditions, higher pH, and location within a particular compositional band in the Sierra Nevada batholith corresponding to the southwestern part of the study unit. High concentrations of organic constituents generally were associated with greater proportions of urban land use. No significant relations were observed between the concentrations of organic constituents and measures of well depth or groundwater age, perhaps because of the high proportions of springs and modern groundwater in the dataset.

The combined use of 87Sr/86Sr and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst

USGS Publications Warehouse

Katz, B.G.; Bullen, T.D.

1996-01-01

The hydrochemical interaction between groundwater and lakewater influences the composition of water that percolates downward from the surficial aquifer system through the underlying intermediate confining unit and recharges the Upper Floridan aquifer along highlands in Florida. The 87Sr/86Sr ratio along with the stable isotopes, D, 18O, and 13C were used as tracers to study the interaction between groundwater, lakewater, and aquifer minerals near Lake Barco, a seepage lake in the mantled karst terrane of northern Florida. Upgradient from the lake, the 87Sr/86Sr ratio of groundwater decreases with depth (mean values of 0.71004, 0.70890, and 0.70852 for water from the surficial aquifer system, intermediate confining unit, and Upper Floridan aquifer, respectively), resulting from the interaction of dilute oxygenated recharge water with aquifer minerals that are less radiogenic with depth. The concentrations of Sr2+ generally increase with depth, and higher concentrations of Sr2+ in water from the Upper Floridan aquifer (20-35 ??g/L), relative to water from the surficial aquifer system and the intermediate confining unit, result from the dissolution of Sr-bearing calcite and dolomite in the Eocene limestone. Dissolution of calcite [??13C = -1.6 permil (???)] is also indicated by an enriched ??13CDIC (-8.8 to - 11.4???) in water from the Upper Floridan aquifer, relative to the overlying hydrogeologic units (??13CDIC < - 16???). Groundwater downgradient from Lake Barco was enriched in 18O and D relative to groundwater upgradient from the lake, indicating mixing of lakewater leakage and groundwater. Downgradient from the lake, the 87Sr/86Sr ratio of groundwater and aquifer material become less radiogenic and the Sr2+ concentrations generally increase with depth. However, Sr2+ concentrations are substantially less than in upgradient groundwaters at similar depths. The lower Sr2+ concentrations result from the influence of anoxic lakewater leakage on the mobility of Sr2+ from clays. Based on results from mass-balance modeling, it is probable that cation exchange plays the dominant role in controlling the 87Sr/86Sr ratio of groundwater, both upgradient and downgradient from Lake Barco. Even though groundwater from the three distinct hydrogeologic units displays considerable variability in Sr concentration and isotopic composition, the dominant processes associated with the mixing of lakewater leakage with groundwater, as well as the effects of mineral-water interaction, can be ascertained by integrating the use of stable and radiogenic isotopic measurements of groundwater, lakewater, and aquifer minerals.

Effects of model layer simplification using composite hydraulic properties

USGS Publications Warehouse

Kuniansky, Eve L.; Sepúlveda, Nicasio; Elango, Lakshmanan

2011-01-01

Groundwater provides much of the fresh drinking water to more than 1.5 billion people in the world (Clarke et al., 1996) and in the United States more that 50 percent of citizens rely on groundwater for drinking water (Solley et al., 1998). As aquifer systems are developed for water supply, the hydrologic system is changed. Water pumped from the aquifer system initially can come from some combination of inducing more recharge, water permanently removed from storage, and decreased groundwater discharge. Once a new equilibrium is achieved, all of the pumpage must come from induced recharge and decreased discharge (Alley et al., 1999). Further development of groundwater resources may result in reductions of surface water runoff and base flows. Competing demands for groundwater resources require good management. Adequate data to characterize the aquifers and confining units of the system, like hydrologic boundaries, groundwater levels, streamflow, and groundwater pumping and climatic data for recharge estimation are to be collected in order to quantify the effects of groundwater withdrawals on wetlands, streams, and lakes. Once collected, three-dimensional (3D) groundwater flow models can be developed and calibrated and used as a tool for groundwater management. The main hydraulic parameters that comprise a regional or subregional model of an aquifer system are the hydraulic conductivity and storage properties of the aquifers and confining units (hydrogeologic units) that confine the system. Many 3D groundwater flow models used to help assess groundwater/surface-water interactions require calculating ?effective? or composite hydraulic properties of multilayered lithologic units within a hydrogeologic unit. The calculation of composite hydraulic properties stems from the need to characterize groundwater flow using coarse model layering in order to reduce simulation times while still representing the flow through the system accurately. The accuracy of flow models with simplified layering and hydraulic properties will depend on the effectiveness of the methods used to determine composite hydraulic properties from a number of lithologic units.

Groundwater-quality data in the Klamath Mountains study unit, 2010: results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Belitz, Kenneth

2014-01-01

Groundwater quality in the 8,806-square-mile Klamath Mountains (KLAM) study unit was investigated by the U.S. Geological Survey (USGS) from October to December 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The KLAM study unit was the thirty-third study unit to be sampled as part of the GAMA-PBP. The GAMA Klamath Mountains study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer system is defined by the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the KLAM study unit. Groundwater quality in the primary aquifer system may differ from the quality in the shallower or deeper water-bearing zones; shallower groundwater may be more vulnerable to surficial contamination. In the KLAM study unit, groundwater samples were collected from sites in Del Norte, Siskiyou, Humboldt, Trinity, Tehama, and Shasta Counties, California. Of the 39 sites sampled, 38 were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the primary aquifer system in the study unit (grid sites), and the remaining site was non-randomized (understanding site). The groundwater samples were analyzed for basic field parameters, organic constituents (volatile organic compounds [VOCs] and pesticides and pesticide degradates), inorganic constituents (trace elements, nutrients, major and minor ions, total dissolved solids [TDS]), radon-222, gross alpha and gross beta radioactivity, and microbial indicators (total coliform and Escherichia coli [E. coli]). Isotopic tracers (stable isotopes of hydrogen and oxygen in water, isotopic ratios of dissolved strontium in water, and stable isotopes of carbon in dissolved inorganic carbon), dissolved noble gases, and age-dating tracers (tritium and carbon-14) were measured to help identify sources and ages of sampled groundwater. Quality-control samples (field blanks, replicate sample pairs, and matrix spikes) were collected at 13 percent of the sites in the KLAM study unit, and the results were used to evaluate the quality of the data from the groundwater samples. Field blank samples rarely contained detectable concentrations of any constituent, indicating that contamination from sample collection or analysis was not a significant source of bias in the data for the groundwater samples. More than 99 percent of the replicate pair samples were within acceptable limits of variability. Matrix-spike sample recoveries were within the acceptable range (70 to 130 percent) for approximately 91 percent of the compounds. This study did not evaluate the quality of water delivered to consumers. After withdrawal, groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is delivered to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-health-based benchmarks established for aesthetic concerns by the CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. All concentrations of organic constituents from grid sites sampled in the KLAM study unit were less than health-based benchmarks. In total, VOCs were detected in 16 of the 38 grid sites sampled (approximately 42 percent), pesticides and pesticide degradates were detected in 8 grid sites (about 21 percent), and microbial indicators were detected in 14 grid sites (approximately 37 percent). Inorganic constituents (trace elements, major and minor ions, nutrients, and uranium and other radioactive constituents) and microbial indicators were sampled for at 38 grid sites, and all concentrations were less than health-based benchmarks, with the exception of one detection of boron greater than the CDPH notification level of 1,000 micrograms per liter (μg/L). Generally, concentrations of inorganic constituents with non-health-based benchmarks (iron, manganese, chloride, and TDS) were less than the CDPH secondary maximum contaminant level (SMCL-CA). Exceptions include three detections of iron greater than the SMCL-CA of 300 μg/L, four detections of manganese greater than the SMCL-CA of 50 μg/L, one detection of chloride greater than the recommended SMCL-CA of 250 μg/L, and one detection of TDS greater than the recommended SMCL-CA of 500 μg/L.

Groundwater quality in the North San Francisco Bay shallow aquifer, California

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.

2018-02-23

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The North San Francisco Bay Shallow Aquifer constitutes one of the study units being evaluated.

Groundwater conditions and studies in the Augusta–Richmond County area, Georgia, 2008–2009

USGS Publications Warehouse

Gonthier, Gerard; Lawrence, Stephen J.; Peck, Michael F.; Holloway, O. Gary

2011-01-01

Groundwater studies and monitoring efforts conducted during 2008–2009, as part of the U.S. Geological Survey (USGS) Cooperative Water Program with the City of Augusta in Richmond County, Georgia, provided data for the effective management of local water resources. During 2008–2009 the USGS completed: (1) installation of three monitoring wells and the collection of lithologic and geophysical logging data to determine the extent of hydrogeologic units, (2) collection of continuous groundwater-level data from wells near Well Fields 2 and 3, (3) collection of synoptic groundwater-level measurements and construction of potentiometric-surface maps in Richmond County to establish flow gradients and groundwater-flow directions in the Dublin and Midville aquifer systems, (4) completion of a 24-hour aquifer test to determine hydraulic characteristics of the lower Dublin aquifer, and upper and lower Midville aquifers in Well Field 2, and (5) collection of groundwater samples from selected wells in Well Field 2 for laboratory analysis of volatile organic compounds and groundwater tracers to assess groundwater quality and estimate the time of groundwater recharge. Potentiometric-surface maps of the Dublin and Midville aquifer systems for 2008–2009 indicate that the general groundwater flow direction within Richmond County is eastward toward the Savannah River, with the exception of the area around Well Field 2, where pumping interrupts the eastward flow of water toward the Savannah River and causes flow lines to bend toward the center of pumping. Results from a 24-hour aquifer test conducted in 2009 within the upper and lower Midville aquifers at Well Field 2 indicated a transmissivity and storativity for the upper and lower Midville aquifers, combined, of 4,000 feet-squared per day and 2x10-4, respectively. The upper and lower Midville aquifers and the middle lower Midville confining unit, which is 85-feet thick in this area, yielded horizontal hydraulic conductivity and specific storage values of about 45 feet per day and 2x10-6 ft-1, respectively. Results from the 24-hour aquifer test also indicate a low horizontal hydraulic conductivity for the lower Dublin aquifer of less than 1 foot per day. Of the 35 volatile organic compounds (VOCs) analyzed in 23 groundwater samples during 2008–2009, only six were detected above laboratory reporting limits in samples from eight wells. No concentration in groundwater samples collected during 2008–2009 exceeded drinking water standards. Trichloroethene had the maximum VOC concentration (1.9 micrograms per liter) collected from a water sample during 2008–2009. Water-quality sampling of several wells near Well Field 2 indicate that, while in operation, the northernmost production well might have diverted groundwater, containing low levels of trichloroethene from at least two other production wells. Analysis of sulfur hexafluoride data indicate the average year of recharge ranges between 1981 and 1984 for water samples from five wells open to the upper and lower Midville aquifers, and 1991 for a water sample from one shallow well open to the lower Dublin aquifer. All of these ages suggest a short flow path and nearby source of contamination. The actual source of low levels of VOCs at Well Field 2 remains unknown. Three newly installed monitoring wells indicate that hydrogeologic units beneath Well Fields 2 and 3 are composed of sand and clay layers. Hydrogeologic units, encountered at Well Field 2, in order of increasing depth are the lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer. West of Well Field 3, hydrogeologic units, in order of increasing depth are the Upper Three Runs aquifer, Gordon confining unit, Gordon aquifer, lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer.

Status of groundwater quality in the Southern, Middle, and Northern Sacramento Valley study units, 2005-08: California GAMA Priority Basin Project

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.; Belitz, Kenneth

2011-01-01

Groundwater quality in the Southern, Middle, and Northern Sacramento Valley study units was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study units are located in California's Central Valley and include parts of Butte, Colusa, Glenn, Placer, Sacramento, Shasta, Solano, Sutter, Tehama, Yolo, and Yuba Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The three study units were designated to provide spatially-unbiased assessments of the quality of untreated groundwater in three parts of the Central Valley hydrogeologic province, as well as to provide a statistically consistent basis for comparing water quality regionally and statewide. Samples were collected in 2005 (Southern Sacramento Valley), 2006 (Middle Sacramento Valley), and 2007-08 (Northern Sacramento Valley). The GAMA studies in the Southern, Middle, and Northern Sacramento Valley were designed to provide statistically robust assessments of the quality of untreated groundwater in the primary aquifer systems that are used for drinking-water supply. The assessments are based on water-quality data collected by the USGS from 235 wells in the three study units in 2005-08, and water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer systems (hereinafter, referred to as primary aquifers) assessed in this study are defined by the depth intervals of the wells in the CDPH database for each study unit. The quality of groundwater in shallow or deep water-bearing zones may differ from quality of groundwater in the primary aquifers; shallow groundwater may be more vulnerable to contamination from the surface. The status of the current quality of the groundwater resource was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifers of the three Sacramento Valley study units, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentrations divided by benchmark concentrations) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than 1.0 indicates a concentration greater than a benchmark. For organic (volatile organic compounds and pesticides) and special-interest (perchlorate) constituents, relative-concentrations were classified as high (greater than 1.0); moderate (equal to or less than 1.0 and greater than 0.1); or low (equal to or less than 0.1). For inorganic (major ion, trace element, nutrient, and radioactive) constituents, the boundary between low and moderate relative-concentrations was set at 0.5. Aquifer-scale proportions were used in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifers that have a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifers that have moderate and low relative-concentrations, respectively. Two statistical approaches-grid-based, which used one value per grid cell, and spatially-weighted, which used the full dataset-were used to calculate aquifer-scale proportions for individual constituents and classes of constituents. High and moderate aquifer-scale proportions were significantly greater for inorgani

Groundwater quality in the Central Sierra Nevada, California

USGS Publications Warehouse

Fram, Miranda S.; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California's drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State's groundwater quality and increases public access to groundwater-quality information. Two small watersheds of the Fresno and San Joaquin Rivers in the Central Sierra Nevada constitute one of the study units being evaluated.

Groundwater quality in the Southern Sierra Nevada, California

USGS Publications Warehouse

Fram, Miranda S.; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California's drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State's groundwater quality and increases public access to groundwater-quality information. The Tehachapi-Cummings Valley and Kern River Valley basins and surrounding watersheds in the Southern Sierra Nevada constitute one of the study units being evaluated.

Groundwater-quality data in the Santa Barbara study unit, 2011: results from the California GAMA Program

USGS Publications Warehouse

Davis, Tracy A.; Kulongoski, Justin T.; Belitz, Kenneth

2013-01-01

Groundwater quality in the 48-square-mile Santa Barbara study unit was investigated by the U.S. Geological Survey (USGS) from January to February 2011, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The Santa Barbara study unit was the thirty-fourth study unit to be sampled as part of the GAMA-PBP. The GAMA Santa Barbara study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system, and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer system is defined as those parts of the aquifers corresponding to the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the Santa Barbara study unit. Groundwater quality in the primary aquifer system may differ from the quality in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. In the Santa Barbara study unit located in Santa Barbara and Ventura Counties, groundwater samples were collected from 24 wells. Eighteen of the wells were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells), and six wells were selected to aid in evaluation of water-quality issues (understanding wells). The groundwater samples were analyzed for organic constituents (volatile organic compounds [VOCs], pesticides and pesticide degradates, and pharmaceutical compounds); constituents of special interest (perchlorate and N-nitrosodimethylamine [NDMA]); naturally occurring inorganic constituents (trace elements, nutrients, major and minor ions, silica, total dissolved solids [TDS], alkalinity, and arsenic, chromium, and iron species); and radioactive constituents (radon-222 and gross alpha and gross beta radioactivity). Naturally occurring isotopes (stable isotopes of hydrogen and oxygen in water, stables isotopes of inorganic carbon and boron dissolved in water, isotope ratios of dissolved strontium, tritium activities, and carbon-14 abundances) and dissolved noble gases also were measured to help identify the sources and ages of the sampled groundwater. In total, 281 constituents and water-quality indicators were measured. Three types of quality-control samples (blanks, replicates, and matrix spikes) were collected at up to 12 percent of the wells in the Santa Barbara study unit, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Blanks rarely contained detectable concentrations of any constituent, suggesting that contamination from sample collection procedures was not a significant source of bias in the data for the groundwater samples. Replicate samples generally were within the limits of acceptable analytical reproducibility. Matrix-spike recoveries were within the acceptable range (70 to 130 percent) for approximately 82 percent of the compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, untreated groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is served to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH and to non-regulatory benchmarks established for aesthetic concerns by CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. All organic constituents and most inorganic constituents that were detected in groundwater samples from the 18 grid wells in the Santa Barbara study unit were detected at concentrations less than drinking-water benchmarks. Of the 220 organic and special-interest constituents sampled for at the 18 grid wells, 13 were detected in groundwater samples; concentrations of all detected constituents were less than regulatory and non-regulatory health-based benchmarks. In total, VOCs were detected in 61 percent of the 18 grid wells sampled, pesticides and pesticide degradates were detected in 11 percent, and perchlorate was detected in 67 percent. Polar pesticides and their degradates, pharmaceutical compounds, and NDMA were not detected in any of the grid wells sampled in the Santa Barbara study unit. Eighteen grid wells were sampled for trace elements, major and minor ions, nutrients, and radioactive constituents; most detected concentrations were less than health-based benchmarks. Exceptions are one detection of boron greater than the CDPH notification level (NL-CA) of 1,000 micrograms per liter (μg/L) and one detection of fluoride greater than the CDPH maximum contaminant level (MCL-CA) of 2 milligrams per liter (mg/L). Results for constituents with non-regulatory benchmarks set for aesthetic concerns from the grid wells showed that iron concentrations greater than the CDPH secondary maximum contaminant level (SMCL-CA) of 300 μg/L were detected in three grid wells. Manganese concentrations greater than the SMCL-CA of 50 μg/L were detected in seven grid wells. Chloride was detected at a concentration greater than the SMCL-CA recommended benchmark of 250 mg/L in four grid wells. Sulfate concentrations greater than the SMCL-CA recommended benchmark of 250 mg/L were measured in eight grid wells, and the concentration in one of these wells was also greater than the SMCL-CA upper benchmark of 500 mg/L. TDS concentrations greater than the SMCL-CA recommended benchmark of 500 mg/L were measured in 17 grid wells, and concentrations in six of these wells were also greater than the SMCL-CA upper benchmark of 1,000 mg/L.

Groundwater quality in the shallow aquifers of the Tulare, Kaweah, and Tule Groundwater Basins and adjacent highlands areas, Southern San Joaquin Valley, California

USGS Publications Warehouse

Fram, Miranda S.

2017-01-18

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The shallow aquifers of the Tulare, Kaweah, and Tule groundwater basins and adjacent highlands areas of the southern San Joaquin Valley constitute one of the study units being evaluated.

Status and understanding of groundwater quality in the San Diego Drainages Hydrogeologic Province, 2004: California GAMA Priority Basin Project

USGS Publications Warehouse

Wright, Michael T.; Belitz, Kenneth

2011-01-01

Groundwater quality in the approximately 3,900-square-mile (mi2) San Diego Drainages Hydrogeologic Province (hereinafter San Diego) study unit was investigated from May through July 2004 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in southwestern California in the counties of San Diego, Riverside, and Orange. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA San Diego study was designed to provide a statistically robust assessment of untreated-groundwater quality within the primary aquifer systems. The assessment is based on water-quality and ancillary data collected by the USGS from 58 wells in 2004 and water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer systems (hereinafter referred to as the primary aquifers) were defined by the depth interval of the wells listed in the California Department of Public Health (CDPH) database for the San Diego study unit. The San Diego study unit consisted of four study areas: Temecula Valley (140 mi2), Warner Valley (34 mi2), Alluvial Basins (166 mi2), and Hard Rock (850 mi2). The quality of groundwater in shallow or deep water-bearing zones may differ from that in the primary aquifers. For example, shallow groundwater may be more vulnerable to surficial contamination than groundwater in deep water-bearing zones. This study had two components: the status assessment and the understanding assessment. The first component of this study-the status assessment of the current quality of the groundwater resource-was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. The status assessment is intended to characterize the quality of groundwater resources within the primary aquifers of the San Diego study unit, not the treated drinking water delivered to consumers by water purveyors. The second component of this study-the understanding assessment-identified the natural and human factors that affect groundwater quality by evaluating land use, well construction, and geochemical conditions of the aquifer. Results from these evaluations were used to help explain the occurrence and distribution of selected constituents in the study unit. Relative-concentrations (sample concentration divided by benchmark concentration) were used as the primary metric for relating concentrations of constituents in groundwater samples to water-quality benchmarks for those constituents that have Federal and (or) California benchmarks. For organic and special-interest constituents, relative-concentrations were classified as high (> 1.0), moderate (> 0.1 and ≤1.0), and low (≤0.1). For inorganic constituents, relative concentrations were classified as high (> 1.0), moderate (> 0.5 and ≤1.0), and low (≤0.5). Grid-based and spatially weighted approaches were then used to evaluate the proportion of the primary aquifers (aquifer-scale proportions) with high, moderate, and low relative-concentrations for individual compounds and classes of constituents. One or more of the inorganic constituents with health-based benchmarks were high (relative to those benchmarks) in 17.6 percent of the primary aquifers in the Temecula Valley, Warner Valley, and Alluvial Basins study areas (hereinafter also collectively referred to as the Alluvial Fill study areas because they are composed of alluvial fill aquifers), and in 25.0 percent of the Hard Rock study area. Inorganic constituents with health-based benchmarks that were frequently detected at high relative-concentrations included vanadium (V), arsenic (As), and boron (B). Vanadium and As concentrations were not significantly correlated to either urban or agricultural land use indicating natural sources as the primary contributors of these constituents to groundwater. The positive correlation of B concentration to urban land-use was significant which indicates that anthropogenic activities are a contributing source of B to groundwater. The correlation of V, As and B concentrations to pH was positive, indicating that in alkaline groundwater these constituents are being desorbed from, or being inhibited from adsorbing to, particle surfaces. Inorganic constituents with aesthetic benchmarks that were detected at high relative-concentrations include manganese (Mn), iron (Fe), and total dissolved solids (TDS). In the Alluvial Fill study areas, Mn and TDS were detected at high relative-concentrations in 13.7 percent of the primary aquifers, and Fe in 6.9 percent. In the Hard Rock study area, Mn was detected at high relative-concentrations in 33.3 percent of the primary aquifers, and TDS in 16.7 percent; Fe was not detected at high relative-concentrations. Total dissolved solids concentrations were significantly correlated to agricultural land use suggesting that agricultural practices are a contributing source of TDS to groundwater. Manganese and Fe concentrations were highest in groundwater with low dissolved oxygen and pH indicating that the reductive dissolution of oxyhydroxides may be an important mechanism for the mobilization of Mn and Fe in groundwater. TDS concentrations were highest in shallow wells and in modern (< 50 yrs) groundwater which indicates anthropogenic activities as a source of TDS concentrations in groundwater. The relative-concentrations of organic constituents with health-based benchmarks were high in 3.0 percent of the primary aquifers in the Alluvial Fill study areas. A single detection in the Alluvial Basins study area of the discontinued gasoline oxygenate methyl tert-butyl ether (MTBE) was the only organic constituent detected at a high relative-concentration; high relative-concentrations of these constituents were not detected in the Hard Rock study area. Twelve of 88 VOCs and 14 of 123 pesticides and pesticide degradates analyzed in grid wells were detected. Chloroform was the only VOC detected in more than 10 percent of the grid wells. The herbicides simazine, atrazine, and prometon were each detected in greater than 10 percent of the grid wells. Perchlorate was detected in 22 percent of the grid wells sampled. The understanding assessment showed a significant correlation of trihalomethanes (THMs) and solvents to urban land-use, indicating that detections of these constituents are more likely to occur in groundwater underlying urbanized areas of the study unit. MTBE concentrations were negatively correlated to the distance from the nearest leaking underground fuel tank, indicating that point sources are the most significant contributing factor for MTBE concentrations to groundwater in the study unit. The positive correlation of THM and herbicide concentrations to modern groundwater was significant, as was the negative correlation of herbicide concentrations to pH and anoxic groundwater. The negative correlation of herbicides to pH and anoxic groundwater was likely due to the fact that these constituents were detected more frequently in shallow wells where groundwater conditions tend to be oxic with relatively low pH.

Groundwater quality in the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts, California

USGS Publications Warehouse

Parsons, Mary C.; Belitz, Kenneth

2014-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s untreated groundwater quality and increases public access to groundwater-quality information. Selected groundwater basins in the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts constitute one of the study units being evaluated.

Groundwater quality in the shallow aquifers of the Monterey Bay, Salinas Valley, and adjacent highland areas, California

USGS Publications Warehouse

Burton, Carmen

2018-05-30

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. The shallow aquifers of the groundwater basins around Monterey Bay, the Salinas Valley, and the highlands adjacent to the Salinas Valley constitute one of the study units.

Geomatics for Mapping of Groundwater Potential Zones in Northern Part of the United Arab Emiratis - Sharjah City

NASA Astrophysics Data System (ADS)

Al-Ruzouq, R.; Shanableh, A.; Merabtene, T.

2015-04-01

In United Arab Emirates (UAE) domestic water consumption has increased rapidly over the last decade. The increased demand for high-quality water, create an urgent need to evaluate the groundwater production of aquifers. The development of a reasonable model for groundwater potential is therefore crucial for future systematic developments, efficient management, and sustainable use of groundwater resources. The objective of this study is to map the groundwater potential zones in northern part of UAE and assess the contributing factors for exploration of potential groundwater resources. Remote sensing data and geographic information system will be used to locate potential zones for groundwater. Various maps (i.e., base, soil, geological, Hydro-geological, Geomorphologic Map, structural, drainage, slope, land use/land cover and average annual rainfall map) will be prepared based on geospatial techniques. The groundwater availability of the basin will qualitatively classified into different classes based on its hydro-geo-morphological conditions. The land use/land cover map will be also prepared for the different seasons using a digital classification technique with a ground truth based on field investigation.

The combined use of 87Sr/86Sr and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst

NASA Astrophysics Data System (ADS)

Katz, Brian G.; Bullen, Thomas D.

1996-12-01

The hydrochemical interaction between groundwater and lakewater influences the composition of water that percolates downward from the surficial aquifer system through the underlying intermediate confining unit and recharges the Upper Floridan aquifer along highlands in Florida. The 87Sr/86Sr ratio along with the stable isotopes, D, 18O, and 13C were used as tracers to study the interaction between groundwater, lakewater, and aquifer minerals near Lake Barco, a seepage lake in the mantled karst terrane of northern Florida. Upgradient from the lake, the 87Sr/86Sr ratio of groundwater decreases with depth (mean values of 0.71004, 0.70890, and 0.70852 for water from the surficial aquifer system, intermediate confining unit, and Upper Floridan aquifer, respectively), resulting from the interaction of dilute oxygenated recharge water with aquifer minerals that are less radiogenic with depth. The concentrations of Sr2+ generally increase with depth, and higher concentrations of Sr2+ in water from the Upper Floridan aquifer (20-35 μg/L), relative to water from the surficial aquifer system and the intermediate confining unit, result from the dissolution of Sr-bearing calcite and dolomite in the Eocene limestone. Dissolution of calcite [δ13C= -1.6permil(‰)] is also indicated by an enriched δ13CDIC(-8.8 to -11.4 ‰) in water from the Upper Floridan aquifer, relative to the overlying hydrogeologic units (δ13CDIC< -16‰). Groundwater downgradient from Lake Barco was enriched in18O and D relative to groundwater upgradient from the lake, indicating mixing of lakewater leakage and groundwater. Downgradient from the lake, the 87Sr/86Sr ratio of groundwater and aquifer material become less radiogenic and the Sr2+ concentrations generally increase with depth. However, Sr2+ concentrations are substantially less than in upgradient groundwaters at similar depths. The lower Sr2+ concentrations result from the influence of anoxic lakewater leakage on the mobility of Sr2+ from clays. Based on results from mass-balance modeling, it is probable that cation exchange plays the dominant role in controlling the 87Sr/86Sr ratio of groundwater, both upgradient and downgradient from Lake Barco. Even though groundwater from the three distinct hydrogeologic units displays considerable variability in Sr concentration and isotopic composition, the dominant processes associated with the mixing of lakewater leakage with groundwater, as well as the effects of mineral-water interaction, can be ascertained by integrating the use of stable and radiogenic isotopic measurements of groundwater, lakewater, and aquifer minerals.

Generalized hydrogeologic framework and groundwater budget for a groundwater availability study for the glacial aquifer system of the United States

USGS Publications Warehouse

Reeves, Howard W.; Bayless, E. Randall; Dudley, Robert W.; Feinstein, Daniel T.; Fienen, Michael N.; Hoard, Christopher J.; Hodgkins, Glenn A.; Qi, Sharon L.; Roth, Jason L.; Trost, Jared J.

2017-12-14

The glacial aquifer system groundwater availability study seeks to quantify (1) the status of groundwater resources in the glacial aquifer system, (2) how these resources have changed over time, and (3) likely system response to future changes in anthropogenic and environmental conditions. The glacial aquifer system extends from Maine to Alaska, although the focus of this report is the part of the system in the conterminous United States east of the Rocky Mountains. The glacial sand and gravel principal aquifer is the largest source of public and self-supplied industrial supply for any principal aquifer and also is an important source for irrigation supply. Despite its importance for water supply, water levels in the glacial aquifer system are generally stable varying with climate and only locally from pumping. The hydrogeologic framework developed for this study includes the information from waterwell records and classification of material types from surficial geologic maps into likely aquifers dominated by sand and gravel deposits. Generalized groundwater budgets across the study area highlight the variation in recharge and discharge primarily driven by climate.

Hydrogeologic setting, hydraulic properties, and ground-water flow at the O-Field area of Aberdeen Proving Ground, Maryland

USGS Publications Warehouse

Banks, W.S.; Smith, B.S.; Donnelly, C.A.

1996-01-01

The U.S. Army disposed chemical agents, laboratory materials, and unexploded ordnance at O-Field in the Edgewood area of Aberdeen Proving Ground, Maryland, from before World War II until at least the 1950's. Soil, ground water, surface water,and wetland sediments in the O-Field area were contaminated from the disposal activity. A ground-water-flow model of the O-Field area was constructed by the U.S. Geological Survey (USGS) in 1989 to simulate flow in the central and southern part of the Gunpowder Neck. The USGS began an additional study of the contamination in the O-Field area in cooperation with the U.S. Army in 1990 to (1) further define the hydrogeologic framework of the O-Field area, (2) characterize the hydraulic properties of the aquifers and confining units, and (3) define ground-water flow paths at O-Field based on the current data and simulations of ground-water flow. A water-table aquifer, an upper confining unit, and an upper confined aquifer comprise the shallow ground-water aquifer system of the O-Field area. A lower confining unit, through which ground-water movement is negligible, is considered a lower boundary to the shallow aquifer system. These units are all part of the Pleistocene Talbot Formation. The model developed in the previous study was redesigned using the data collected during this study and emphasized New O-Field. The current steady-state model was calibrated to water levels of June 1993. The rate of ground-water flow calculated by the model was approximately 0.48 feet per day (ft/d) and the rate determined from chlorofluorocarbon dates was approximately 0.39 ft/d.

Relationship between altitude and lithium in groundwater in the United States of America: results of a 1992-2003 study.

PubMed

Huber, Rebekah S; Kim, Namkug; Renshaw, Carl E; Renshaw, Perry F; Kondo, Douglas G

2014-11-01

Therapeutic dosages of lithium are known to reduce suicide rates, which has led to investigations of confounding environmental risk factors for suicide such as lithium in groundwater. It has been speculated that this might play a role in the potential relationship between suicide and altitude. A recent study in Austria involving geospatial analysis of lithium in groundwater and suicide found lower levels of lithium at higher altitudes. Since there is no reason to suspect this correlation is universal given variation in geology, the current study set out to investigate the relationship between altitude and lithium in groundwater in the United States of America (USA). The study utilised data extracted from the National Water-Quality Assessment programme implemented by the United States Geological Survey that has collected 5,183 samples from 48 study areas in USA for the period of 1992 to 2003. Lithium was the trace-element of interest and 518 samples were used in the current analyses. Due to uneven lithium sampling within the country, only the states (n=15) with the highest number of lithium samples were included. Federal information processing standard codes were used to match data by county with the mean county altitude calculated using altitude data from the Shuttle Radar Topography Mission. The study was controlled for potential confounding factors known to affect levels of lithium in groundwater including aquifer, aquifer type, lithology, water level and the depths of wells. The levels of lithium in groundwater, increased with altitude (R(2) = 0.226, P <0.001) during the study period. These findings differ from the Austrian study and suggest a need for further research accounting also for the impact of geographical variation.

Conceptual model of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada

USGS Publications Warehouse

Long, Andrew J.; Aurand, Katherine R.; Bednar, Jennifer M.; Davis, Kyle W.; McKaskey, Jonathan D.R.G.; Thamke, Joanna N.

2014-01-01

The three uppermost principal aquifer systems of the Northern Great Plains—the glacial, lower Tertiary, and Upper Cretaceous aquifer systems—are described in this report and provide water for irrigation, mining, public and domestic supply, livestock, and industrial uses. These aquifer systems primarily are present in two nationally important fossil-fuelproducing areas: the Williston and Powder River structural basins in the United States and Canada. The glacial aquifer system is contained within glacial deposits that overlie the lower Tertiary and Upper Cretaceous aquifer systems in the northeastern part of the Williston structural basin. Productive sand and gravel aquifers exist within this aquifer system. The Upper Cretaceous aquifer system is contained within bedrock lithostratigraphic units as deep as 2,850 and 8,500 feet below land surface in the Williston and Powder River structural basins, respectively. Petroleum extraction from much deeper formations, such as the Bakken Formation, is rapidly increasing because of recently improved hydraulic fracturing methods that require large volumes of relatively freshwater from shallow aquifers or surface water. Extraction of coalbed natural gas from within the lower Tertiary aquifer system requires removal of large volumes of groundwater to allow degasification. Recognizing the importance of understanding water resources in these energy-rich basins, the U.S. Geological Survey (USGS) Groundwater Resources Program (http://water.usgs.gov/ogw/gwrp/) began a groundwater study of the Williston and Powder River structural basins in 2011 to quantify this groundwater resource, the results of which are described in this report. The overall objective of this study was to characterize, quantify, and provide an improved conceptual understanding of the three uppermost and principal aquifer systems in energy-resource areas of the Northern Great Plains to assist in groundwater-resource management for multiple uses. The study area includes parts of Montana, North Dakota, South Dakota, and Wyoming in the United States and Manitoba and Saskatchewan in Canada. The glacial aquifer system is contained within glacial drift consisting primarily of till, with smaller amounts of glacial outwash sand and gravel deposits. The lower Tertiary and Upper Cretaceous aquifer systems are contained within several formations of the Tertiary and Cretaceous geologic systems, which are hydraulically separated from underlying aquifers by a basal confining unit. The lower Tertiary and Upper Cretaceous aquifer systems each were divided into three hydrogeologic units that correspond to one or more lithostratigraphic units. The period prior to 1960 is defined as the predevelopment period when little groundwater was extracted. From 1960 through 1990, numerous flowing wells were installed near the Yellowstone, Little Missouri and Knife Rivers, resulting in local groundwater declines. Recently developed technologies for the extraction of petroleum resources, which largely have been applied in the study area since about 2005, require millions of gallons of water for construction of each well, with additional water needed for long-term operation; therefore, the potential for an increase in groundwater extraction is high. In this study, groundwater recharge and discharge components were estimated for the period 1981–2005. Groundwater recharge primarily occurs from infiltration of rainfall and snowmelt (precipitation recharge) and infiltration of streams into the ground (stream infiltration). Total estimated recharge to the Williston and Powder River control volumes is 4,560 and 1,500 cubic feet per second, respectively. Estimated precipitation recharge is 26 and 15 percent of total recharge for the Williston and Powder River control volumes, respectively. Estimated stream infiltration is 71 and 80 percent of total recharge for the Williston and Powder River control volumes, respectively. Groundwater discharge primarily is to streams and springs and is estimated to be about 97 and 92 percent of total discharge for the Williston and Powder River control volumes, respectively. Most of the remaining discharge results from pumped and flowing wells. Groundwater flow in the Williston structural basin generally is from the west and southwest toward the east, where discharge to streams occurs. Locally, in the uppermost hydrogeologic units, groundwater generally is unconfined and flows from topographically high to low areas, where discharge to streams occurs. Groundwater flow in the Powder River structural basin generally is toward the north, with local variations, particularly in the upper Fort Union aquifer, where flow is toward streams.

Regional groundwater characteristics and hydraulic conductivity based on geological units in Korean peninsula

NASA Astrophysics Data System (ADS)

Kim, Y.; Suk, H.

2011-12-01

In this study, about 2,000 deep observation wells, stream and/or river distribution, and river's density were analyzed to identify regional groundwater flow trend, based on the regional groundwater survey of four major river watersheds including Geum river, Han river, Youngsan-Seomjin river, and Nakdong river in Korea. Hydrogeologial data were collected to analyze regional groundwater flow characteristics according to geological units. Additionally, hydrological soil type data were collected to estimate direct runoff through SCS-CN method. Temperature and precipitation data were used to quantify infiltration rate. The temperature and precipitation data were also used to quantify evaporation by Thornthwaite method and to evaluate groundwater recharge, respectively. Understanding the regional groundwater characteristics requires the database of groundwater flow parameters, but most hydrogeological data include limited information such as groundwater level and well configuration. In this study, therefore, groundwater flow parameters such as hydraulic conductivities or transmissivities were estimated using observed groundwater level by inverse model, namely PEST (Non-linear Parameter ESTimation). Since groundwater modeling studies have some uncertainties in data collection, conceptualization, and model results, model calibration should be performed. The calibration may be manually performed by changing parameters step by step, or various parameters are simultaneously changed by automatic procedure using PEST program. In this study, both manual and automatic procedures were employed to calibrate and estimate hydraulic parameter distributions. In summary, regional groundwater survey data obtained from four major river watersheds and various data of hydrology, meteorology, geology, soil, and topography in Korea were used to estimate hydraulic conductivities using PEST program. Especially, in order to estimate hydraulic conductivity effectively, it is important to perform in such a way that areas of same or similar hydrogeological characteristics should be grouped into zones. Keywords: regional groundwater, database, hydraulic conductivity, PEST, Korean peninsular Acknowledgements: This work was supported by the Radioactive Waste Management of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (2011T100200152)

Proglacial Groundwater Flux and Storage in the Cordillera Blanca, Peru

NASA Astrophysics Data System (ADS)

Chavez, D.; McKenzie, J. M.; Baraer, M.; Mark, B. G.

2012-12-01

As tropical glaciers continue to rapidly retreat in the Cordillera Blanca, Peru, dry-season water resources are becoming more dependent on groundwater baseflow. Therefore, understanding the flux and storage of proglacial groundwater is necessary to forecast how groundwater storage can offset decreasing water resources. Recent studies of the Rio Santa Watershed, which drains the western slopes of the Cordillera Blanca, have identified that groundwater is the largest contributor to outflow from many watersheds during the dry season and that the flux of groundwater is temporarily available (< 4years). These groundwater estimates are based on chemical mass balance models that use hydrochemical and isotopic results primarily from surface water samples and stream discharge measurements. Although effective, this approach is limited by the absence of data from proglacial aquifers. In July, 2012, we installed six groundwater monitoring wells to a maximum depth of 6 m in two proglacial valleys in the Cordillera Blanca. For each well, water samples were collected for hydrochemical and isotopic analysis, slug-tests were conducted to measure hydraulic conductivity, and water levels were continuously monitored using pressure transducers. In both valleys we observed an upper layer of clay to silt sized glaciolacustrine material at each drill site. This layer was typically less than 5 m in thickness and had a low hydraulic conductivity (< 10-7 m/s). Underlying the clay layer were water bearing units of course material (either well-sorted sand/gravel or talus deposits) with an average hydraulic conductivity of 10-5 m/s. Additionally numerous discontinuous sand lenses and localized glaciofluvial gravel deposits were observed within the clay layer. The glaciolacustrine deposits behave as confining units that were capable of generating localized artesian conditions in the coarse grain units. The occurrence of the clay units adjacent to the main stream channels suggests that the flatness of the valley floors is not the result of river meander. The coarse grained units have the potential to act as important aquifers with significant groundwater storage and flow. Our preliminary findings indicate that the course grained units are important hydrogeological conduits with the ability to buffer low flow conditions in proglacial streams during the dry season. We present a new schematic model of how groundwater moves through these important proglacial environments, providing temporal storage of glacial meltwater and precipitation.

Ground-water recharge in the arid and semiarid southwestern United States - Climatic and geologic framework: Chapter A in Ground-water recharge in the arid and semiarid southwestern United States (Professional Paper 1703)

USGS Publications Warehouse

Stonestrom, David A.; Harrill, James R.; Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

2007-01-01

Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Niño and Pacific Decadal Oscillations strongly but irregularly control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of multidecadal droughts unlike any in the modern instrumental record. Anthropogenically induced climate change likely will reduce ground-water recharge through diminished snowpack at higher elevations, and perhaps through increased drought. Future changes in El Niño and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Land-use modifications influence ground-water recharge directly through vegetation, irrigation, and impermeable area, and indirectly through climate change. High ranges bounding the study area—the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east—provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive Paleozoic aquifers in mountainous recharge areas, and distinct modes of recharge in the Colorado Plateau and Basin and Range subregions.

Groundwater discharge by evapotranspiration, Dixie Valley, west-central Nevada, March 2009-September 2011

USGS Publications Warehouse

Garcia, C. Amanda; Huntington, Jena M; Buto, Susan G.; Moreo, Michael T.; Smith, J. LaRue; Andraski, Brian J.

2014-01-01

Mean annual basin-scale ETg totaled about 28 million cubic meters (Mm3) (23,000 acre-feet [acre-ft]), and represents the sum of ETg from all ET units. Annual groundwater ET from vegetated areas totaled about 26 Mm3 (21,000 acre-ft), and was dominated by the moderate-to-dense shrubland ET unit (54 percent), followed by sparse shrubland (37 percent) and grassland (9 percent) ET units. Senesced grasses observed in the northern most areas of the moderate-to-dense ET unit likely confounded the vegetation index and led to an overestimate of ETg for this ET unit. Therefore, mean annual ETg for moderate-to-dense shrubland presented here is likely an upper bound. Annual groundwater ET from the playa ET unit was 2.2 Mm3 (1,800 acre-ft), whereas groundwater ET from the playa lake ET unit was 0–0.1 Mm3 (0–100 acre-ft). Oxygen-18 and deuterium data indicate discharge from the playa center predominantly represents removal of local precipitation-derived recharge. The playa lake estimate, therefore, is considered an upper bound. Mean annual ETg estimates for Dixie Valley are assumed to represent the pre‑development, long-term ETg rates within the study area.

Analysis of Infrequent (Quasi-Decadal) Large Groundwater Recharge Events: A Case Study for Northern Utah, United States

NASA Astrophysics Data System (ADS)

Masbruch, M.; Rumsey, C.; Gangopadhyay, S.; Susong, D.; Pruitt, T.

2015-12-01

There has been a considerable amount of research linking climatic variability to hydrologic responses in arid and semi-arid regions such as the western United States. Although much effort has been spent to assess and predict changes in surface-water resources, little has been done to understand how climatic events and changes affect groundwater resources. This study focuses on quantifying the effects of large quasi-decadal groundwater recharge events on groundwater in the northern Utah portion of the Great Basin for the period 1960 to 2013. Groundwater-level monitoring data were analyzed with climatic data to characterize climatic conditions and frequency of these large recharge events. Using observed water-level changes and multivariate analysis, five large groundwater recharge events were identified within the study area and period, with a frequency of about 11 to 13 years. These events were generally characterized as having above-average annual precipitation and snow water equivalent and below-average seasonal temperatures, especially during the spring (April through June). Existing groundwater flow models for several basins within the study area were used to quantify changes in groundwater storage from these events. Simulated groundwater storage increases per basin from a single event ranged from about 115 Mm3 (93,000 acre-feet) to 205 Mm3 (166,000 acre-ft). Extrapolating these amounts over the entire northern Great Basin indicates that even a single large quasi-decadal recharge event could result in billions of cubic meters (millions of acre-feet) of groundwater recharge. Understanding the role of these large quasi-decadal recharge events in replenishing aquifers and sustaining water supplies is crucial for making informed water management decisions.

Hydraulic-property estimates for use with a transient ground-water flow model of the Death Valley regional ground-water flow system, Nevada and California

USGS Publications Warehouse

Belcher, Wayne R.; Elliott, Peggy E.; Geldon, Arthur L.

2001-01-01

The Death Valley regional ground-water flow system encompasses an area of about 43,500 square kilometers in southeastern California and southern Nevada, between latitudes 35? and 38?15' north and longitudes 115? and 117?45' west. The study area is underlain by Quaternary to Tertiary basin-fill sediments and mafic-lava flows; Tertiary volcanic, volcaniclastic, and sedimentary rocks; Tertiary to Jurassic granitic rocks; Triassic to Middle Proterozoic carbonate and clastic sedimentary rocks; and Early Proterozoic igneous and metamorphic rocks. The rock assemblage in the Death Valley region is extensively faulted as a result of several episodes of tectonic activity. This study is comprised of published and unpublished estimates of transmissivity, hydraulic conductivity, storage coefficient, and anisotropy ratios for hydrogeologic units within the Death Valley region study area. Hydrogeologic units previously proposed for the Death Valley regional transient ground-water flow model were recognized for the purpose of studying the distribution of hydraulic properties. Analyses of regression and covariance were used to assess if a relation existed between hydraulic conductivity and depth for most hydrogeologic units. Those analyses showed a weak, quantitatively indeterminate, relation between hydraulic conductivity and depth.

Status and understanding of groundwater quality in the Klamath Mountains study unit, 2010: California GAMA Priority Basin Project

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.; Belitz, Kenneth

2014-01-01

Groundwater quality in the Klamath Mountains (KLAM) study unit was investigated as part of the Priority Basin Project of the California Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in Del Norte, Humboldt, Shasta, Siskiyou, Tehama, and Trinity Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA Priority Basin Project was designed to provide a spatially unbiased, statistically robust assessment of the quality of untreated (raw) groundwater in the primary aquifer system. The assessment is based on water-quality data and explanatory factors for groundwater samples collected in 2010 by the USGS from 39 sites and on water-quality data from the California Department of Public Health (CDPH) water-quality database. The primary aquifer system was defined by the depth intervals of the wells listed in the CDPH water-quality database for the KLAM study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. This study included two types of assessments: (1) a status assessment, which characterized the status of the current quality of the groundwater resource by using data from samples analyzed for volatile organic compounds, pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements, and (2) an understanding assessment, which evaluated the natural and human factors potentially affecting the groundwater quality. The assessments were intended to characterize the quality of groundwater resources in the primary aquifer system of the KLAM study unit, not the quality of treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentrations divided by the health- or aesthetic-based benchmark concentrations) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than (>) 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to (≤) 1.0 indicates a concentration less than or equal to a benchmark. Relative-concentrations of organic constituents were classified as “high” (relative-concentration > 1.0), “moderate” (0.1 Aquifer-scale proportion was used in the status assessment as the primary metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentages of the primary aquifer system with moderate and low relative-concentrations, respectively. The KLAM study unit includes more than 8,800 square miles (mi2), but only those areas near the sampling sites, about 920 mi2, are included in the areal assessment of the study unit. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. To confirm this methodology, 90 percent confidence intervals were calculated for the grid-based high aquifer-scale proportions and were compared to the spatially weighted results, which were found to be within these confidence intervals in all cases. Grid-based results were selected for use in the status assessment unless, as was observed in a few cases, a grid-based result was zero and the spatially weighted result was not zero, in which case, the spatially weighted result was used. The status assessment showed that inorganic constituents with human-health benchmarks were detected at high relative-concentrations in 2.6 percent of the primary aquifer system and at moderate relative-concentrations in 10 percent of the system. The high aquifer-scale proportion for inorganic constituents mainly reflected the high aquifer-scale proportions of boron. Inorganic constituents with secondary maximum contaminant levels were detected at high relative-concentrations in 13 percent of the primary aquifer system and at moderate relative-concentrations in 10 percent of the system. The constituents present at high relative-concentrations included iron and manganese. Organic constituents with human-health benchmarks were not detected at high relative-concentrations, but were detected at moderate relative-concentrations in 1.9 percent of the primary aquifer system. The 1.9 percent reflected a spatially weighted moderate aquifer-scale proportion for the gasoline additive methyl tert-butyl ether. Of the 148 organic constituents analyzed, 14 constituents were detected. Only one organic constituent had a detection frequency of greater than 10 percent—the trihalomethane, chloroform. The second component of this study, the understanding assessment, identified the natural and human factors that may have affected the groundwater quality in the KLAM study unit by evaluating statistical correlations between water-quality constituents and potential explanatory factors. The potential explanatory factors evaluated were aquifer lithology, land use, hydrologic conditions, depth, groundwater age, and geochemical conditions. Results of the statistical evaluations were used to explain the occurrence and distribution of constituents in the KLAM study unit. Groundwater age distribution (modern, mixed, or pre-modern), redox class (oxic, mixed, or anoxic), and dissolved oxygen concentration were the explanatory factors that best explained occurrence patterns of the inorganic constituents. High concentrations of boron were found to be associated with groundwater classified as mixed or pre-modern with respect to groundwater age. Boron was also negatively correlated to dissolved oxygen and positively correlated to specific conductance. Iron and manganese concentrations were strongly associated with low dissolved oxygen concentrations, anoxic and mixed redox classifications, and pre-modern groundwater. Specific conductance concentrations were found to be related to pre-modern groundwater, low dissolved oxygen concentrations, and high pH. Chloroform was selected for additional evaluation in the understanding assessment because it was detected in more than 10 percent of wells sampled in the KLAM study unit. Septic tank density was the only explanatory factor that was found to relate to chloroform concentrations.

Groundwater quality in the Santa Clara River Valley, California

USGS Publications Warehouse

Burton, Carmen A.; Landon, Matthew K.; Belitz, Kenneth

2011-01-01

The Santa Clara River Valley (SCRV) study unit is located in Los Angeles and Ventura Counties, California, and is bounded by the Santa Monica, San Gabriel, Topatopa, and Santa Ynez Mountains, and the Pacific Ocean. The 460-square-mile study unit includes eight groundwater basins: Ojai Valley, Upper Ojai Valley, Ventura River Valley, Santa Clara River Valley, Pleasant Valley, Arroyo Santa Rosa Valley, Las Posas Valley, and Simi Valley (California Department of Water Resources, 2003; Montrella and Belitz, 2009). The SCRV study unit has hot, dry summers and cool, moist winters. Average annual rainfall ranges from 12 to 28 inches. The study unit is drained by the Ventura and Santa Clara Rivers, and Calleguas Creek. The primary aquifer system in the Ventura River Valley, Ojai Valley, Upper Ojai Valley, and Simi Valley basins is largely unconfined alluvium. The primary aquifer system in the remaining groundwater basins mainly consists of unconfined sands and gravels in the upper portion and partially confined marine and nonmarine deposits in the lower portion. The primary aquifer system in the SCRV study unit is defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health (CDPH) database. Public-supply wells typically are completed in the primary aquifer system to depths of 200 to 1,100 feet below land surface (bls). The wells contain solid casing reaching from the land surface to a depth of about 60-700 feet, and are perforated below the solid casing to allow water into the well. Water quality in the primary aquifer system may differ from the water in the shallower and deeper parts of the aquifer. Land use in the study unit is approximately 40 percent (%) natural (primarily shrubs, grassland, and wetlands), 37% agricultural, and 23% urban. The primary crops are citrus, avocados, alfalfa, pasture, strawberries, and dry beans. The largest urban areas in the study unit are the cities of Ventura, Oxnard, Camarillo, Simi Valley, Newhall, and Santa Clarita. Currently, groundwater pumping for agricultural use accounts for the greatest amount of discharge from the aquifer system in the SCRV study unit, followed by municipal use. Recharge to the groundwater system is through stream-channel infiltration from the three main river systems and by direct infiltration of precipitation and irrigation. Recharge facilities in the Oxnard forebay play an important role in recharging the local aquifer systems.

Modeling contribution of shallow groundwater to evapotranspiration and yield of maize in an arid area

NASA Astrophysics Data System (ADS)

Gao, Xiaoyu; Huo, Zailin; Qu, Zhongyi; Xu, Xu; Huang, Guanhua; Steenhuis, Tammo S.

2017-02-01

Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m3. The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.

Modeling contribution of shallow groundwater to evapotranspiration and yield of maize in an arid area

PubMed Central

Gao, Xiaoyu; Huo, Zailin; Qu, Zhongyi; Xu, Xu; Huang, Guanhua; Steenhuis, Tammo S.

2017-01-01

Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m3. The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater. PMID:28220874

Modeling contribution of shallow groundwater to evapotranspiration and yield of maize in an arid area.

PubMed

Gao, Xiaoyu; Huo, Zailin; Qu, Zhongyi; Xu, Xu; Huang, Guanhua; Steenhuis, Tammo S

2017-02-21

Capillary rise from shallow groundwater can decrease the need for irrigation water. However, simple techniques do not exist to quantify the contribution of capillary flux to crop water use. In this study we develop the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) for calculating capillary fluxes from shallow groundwater using readily available data. The model combines an analytical solution of upward flux from groundwater with the EPIC crop growth model. AWPM-SG was calibrated and validated with 2-year lysimetric experiment with maize. Predicted soil moisture, groundwater depth and leaf area index agreed with the observations. To investigate the response of model, various scenarios were run in which the irrigation amount and groundwater depth were varied. Simulations shows that at groundwater depth of 1 m capillary upward supplied 41% of the evapotranspiration. This reduced to 6% at groundwater depth of 2 m. The yield per unit water consumed (water productivity) was nearly constant for 2.3 kg/m 3 . The yield per unit water applied (irrigation water productivity) increased with decreasing irrigation water because capillary rise made up in part for the lack of irrigation water. Consequently, using AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater.

Geology, ground-water hydrology, geochemistry, and ground-water simulation of the Beaumont and Banning Storage Units, San Gorgonio Pass area, Riverside County, California

USGS Publications Warehouse

Rewis, Diane L.; Christensen, Allen H.; Matti, Jonathan; Hevesi, Joseph A.; Nishikawa, Tracy; Martin, Peter

2006-01-01

Ground water has been the only source of potable water supply for residential, industrial, and agricultural users in the Beaumont and Banning storage units of the San Gorgonio Pass area, Riverside County, California. Ground-water levels in the Beaumont area have declined as much as 100 feet between the early 1920s and early 2000s, and numerous natural springs have stopped flowing. In 1961, the San Gorgonio Pass Water Agency (SGPWA) entered into a contract with the California State Department of Water Resources to receive 17,300 acre-feet per year of water to be delivered by the California State Water Project (SWP) to supplement natural recharge. Currently (2005), a pipeline is delivering SWP water into the area, and the SGPWA is artificially recharging the ground-water system using recharge ponds located along Little San Gorgonio Creek in Cherry Valley with the SWP water. In addition to artificial recharge, SGPWA is considering the direct delivery of SWP water for the irrigation of local golf courses and for agricultural supply in lieu of ground-water pumpage. To better understand the potential hydrologic effects of different water-management alternatives on ground-water levels and movement in the Beaumont and Banning storage units, existing geohydrologic and geochemical data were compiled, new data from a basin-wide ground-water level and water-quality monitoring network were collected, monitoring wells were installed near the Little San Gorgonio Creek recharge ponds, geohydrologic and geochemical analyses were completed, and a ground-water flow simulation model was developed. The San Gorgonio Pass area was divided into several storage units on the basis of mapped or inferred faults. This study addresses primarily the Beaumont and Banning storage units. The geologic units in the study area were generalized into crystalline basement rocks and sedimentary deposits. The younger sedimentary deposits and the surficial deposits are the main water-bearing deposits in the San Gorgonio Pass area. The water-bearing deposits were divided into three aquifers: (1) the perched aquifer, (2) the upper aquifer, and (3) the lower aquifer based on lithologic and downhole geophysical logs. Natural recharge in the San Gorgonio Pass area was estimated using INFILv3, a deterministic distributed- parameter precipitation-runoff model. The INFILv3 model simulated that the potential recharge of precipitation and runoff in the Beaumont and Banning storage units was about 3,710 acre-feet per year and that the potential recharge in 28 sub-drainage basins upstream of the storage units was about 6,180 acre-feet per year. The water supply for the Beaumont and Banning storage units is supplied by pumping ground water from wells in the Canyon (Edgar and Banning Canyons), Banning Bench, Beaumont, and Banning storage units. Total annual pumpage from the Beaumont and Banning storage units ranged from about 1,630 acre-feet in 1936 to about 20,000 acre-feet in 2003. Ground-water levels declined by as much as 100 feet in the Beaumont storage unit from 1926-2003 in response to ground-water pumping of about 450,160 acre-feet during this period. Since ground-water development began in the San Gorgonio Pass area, there have been several sources of artificial recharge to the basin including return flow from applied water on crops, golf courses, and landscape; septic-tank seepage; and infiltration of storm runoff diversions and imported water into recharge ponds. Return flow from applied water and septic-tank seepage was estimated to reach a maximum of about 8,100 acre-feet per year in 2003. Owing to the great depth of water in much of study area (in excess of 150 feet), the return flow and septic-tank seepage takes years to decades to reach the water table. Stable-isotope data indicate that the source of ground-water recharge was precipitation from storms passing through the San Gorgonio Pass as opposed to runoff from the higher altitudes of the San Bernar

Basewide Groundwater Operable Unit. Groundwater Operable Unit Remedial Investigation/Feasibility Study Report. Volume 1

DTIC Science & Technology

1994-06-01

units would be reused in the remedy. Contingency measures to be included in the remedy are potential metals removal prior to water end use, potential...onbase reuse of a portion of the water, and wellhead treatment on offbase supply wells. The contingency measures will only be implemented if necessary...94 LEGEND Ouatmar aluvi dposts agua Frmaion(cosoldatd aluval epoits W iead rdetilnsMhte omtin(neitccnlmeae ansoe9ndkeca F 70 Quvatei-lernayalvu e pk

Groundwater-Quality Data in the South Coast Interior Basins Study Unit, 2008: Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Kulongoski, Justin T.; Ray, Mary C.; Belitz, Kenneth

2009-01-01

Groundwater quality in the approximately 653-square-mile South Coast Interior Basins (SCI) study unit was investigated from August to December 2008, as part of the Priority Basins Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basins Project was developed in response to Legislative mandates (Supplemental Report of the 1999 Budget Act 1999-00 Fiscal Year; and, the Groundwater-Quality Monitoring Act of 2001 [Sections 10780-10782.3 of the California Water Code, Assembly Bill 599]) to assess and monitor the quality of groundwater used as public supply for municipalities in California, and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). SCI was the 27th study unit to be sampled as part of the GAMA Priority Basins Project. This study was designed to provide a spatially unbiased assessment of the quality of untreated groundwater used for public water supplies within SCI, and to facilitate statistically consistent comparisons of groundwater quality throughout California. Samples were collected from 54 wells within the three study areas [Livermore, Gilroy, and Cuyama] of SCI in Alameda, Santa Clara, San Benito, Santa Barbara, Ventura, and Kern Counties. Thirty-five of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells), and 19 were selected to aid in evaluation of specific water-quality issues (understanding wells). The groundwater samples were analyzed for organic constituents [volatile organic compounds (VOCs), pesticides and pesticide degradates, polar pesticides and metabolites, and pharmaceutical compounds], constituents of special interest [perchlorate and N-nitrosodimethylamine (NDMA)], naturally occurring inorganic constituents [trace elements, nutrients, major and minor ions, silica, total dissolved solids (TDS), and alkalinity], and radioactive constituents [gross alpha and gross beta radioactivity and radon-222]. Naturally occurring isotopes [stable isotopes of hydrogen, oxygen, and carbon, and activities of tritium and carbon-14] and dissolved noble gases also were measured to help identify the sources and ages of the sampled groundwater. In total, 288 constituents and water-quality indicators (field parameters) were investigated. Three types of quality-control samples (blanks, replicates, and matrix spikes) each were collected at approximately 4-11 percent of the wells, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a significant source of bias in the data obtained from the groundwater samples. Differences between replicate samples generally were less than 10 percent relative standard deviation, indicating acceptable analytical reproducibility. Matrix spike recoveries were within the acceptable range (70 to 130 percent) for most compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, untreated groundwater typically is treated, disinfected, and/or blended with other waters to maintain water quality. Regulatory thresholds apply to water that is served to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and nonregulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH), and to nonregulatory thresholds established for aesthetic and technical concerns by CDPH. Comparisons between data collected for this study and thresholds for drinking water are for illustrative purposes only, and are not indicative of complia

Legacy Nitrate Impacts on Groundwater and Streams

NASA Astrophysics Data System (ADS)

Tesoriero, A. J.; Juckem, P. F.; Miller, M. P.

2017-12-01

Decades of recharge of high-nitrate groundwater have created a legacy—a mass of high-nitrate groundwater—that has implications for future nitrate concentrations in groundwater and in streams. In the United States, inorganic nitrogen fertilizer applications to the land surface have increased ten-fold since 1950, resulting in sharp increases in nitrate concentrations in recharging groundwater, which pose a risk to deeper groundwater and streams. This study assesses the factors that control time lags and eventual concentrations of legacy nitrate in groundwater and streams. Results from the USGS National Water-Quality Assessment Project are presented which elucidate nitrate trends in recharging groundwater, delineate redox zones and assess groundwater and stream vulnerability to legacy nitrate sources on a regional scale. This study evaluated trends and transformations of agricultural chemicals based on groundwater age and water chemistry data along flow paths from recharge areas to streams at 20 study sites across the United States. Median nitrate recharge concentrations in these agricultural areas have increased markedly over the last 50 years, from 4 to 7.5 mg N/L. The effect that nitrate accumulation in shallow aquifers will have on drinking water quality and stream ecosystems is dependent on the redox zones encountered along flow paths and on the age distribution of nitrate discharging to supply wells and streams. Delineating redox zones on a regional scale is complicated by the spatial variability of reaction rates. To overcome this limitation, we applied logistic regression and machine learning techniques to predict the probability of a specific redox condition in groundwater in the Chesapeake Bay watershed and the Fox-Wolf-Peshtigo study area in Wisconsin. By relating redox-active constituent concentrations in groundwater samples to indicators of residence time and/or electron donor availability, we were able to delineate redox zones on a regional scale - an important indicator of groundwater vulnerability and the vulnerability of streams to legacy nitrate sources.

Hydrogeology of a hazardous-waste disposal site near Brentwood, Williamson County, Tennessee

USGS Publications Warehouse

Tucci, Patrick; Hanchar, D.W.; Lee, R.W.

1990-01-01

Approximately 44,000 gal of industrial solvent wastes were disposed in pits on a farm near Brentwood, Tennessee, in 1978, and contaminants were reported in the soil and shallow groundwater on the site in 1985. In order for the State to evaluate possible remedial-action alternatives, an 18-month study was conducted to define the hydrogeologic setting of the site and surrounding area. The area is underlain by four hydrogeologic units: (1) an upper aquifer consisting of saturated regolith, Bigby-Cannon Limestone, and weathered Hermitage Formation; (2) the Hermitage confining unit; (3) a lower aquifer consisting of the Carters Limestone; and (4) the Lebanon confining unit. Wells generally are low yielding less than 1 gal/min ), although locally the aquifers may yield as much as 80 gal/minute. This lower aquifer is anisotropic, and transmissivity of this aquifer is greatest in a northwest-southeast direction. Recharge to the groundwater system is primarily from precipitation, and estimates of average annual recharge rates range from 6 to 15 inches/year. Discharge from the groundwater system is primarily to the Little Harpeth River and its tributaries. Groundwater flow at the disposal site is mainly to a small topographic depression that drains the site. Geochemical data indicate four distinct water types. These types represent (1) shallow, rapidly circulating groundwater; (2) deeper (> than 100 ft), rapidly circulating groundwater; (3) shallow, slow moving groundwater; and (4) deeper, slow moving groundwater. Results of the numerical model indicate that most flow is in the upper aquifer. (USGS)

Conceptual understanding and groundwater quality of selected basin-fill aquifers in the Southwestern United States

USGS Publications Warehouse

Thiros, Susan A.; Bexfield, Laura M.; Anning, David W.; Huntington, Jena M.

2010-01-01

The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey has been conducting a regional analysis of water quality in the principal aquifer systems in the southwestern United States (hereinafter, “Southwest”) since 2005. Part of the NAWQA Program, the objective of the Southwest Principal Aquifers (SWPA) study is to develop a better understanding of water quality in basin-fill aquifers in the region by synthesizing information from case studies of 15 basins into a common set of important natural and human-related factors found to affect groundwater quality.The synthesis consists of three major components:1. Summary of current knowledge about the groundwater systems, and the status of, changes in, and influential factors affecting quality of groundwater in basin-fill aquifers in 15 basins previously studied by NAWQA (this report).2. Development of a conceptual model of the primary natural and human-related factors commonly affecting groundwater quality, thereby building a regional understanding of the susceptibility and vulnerability of basin-fill aquifers to contaminants.3. Development of statistical models that relate the concentration or occurrence of specific chemical constituents in groundwater to natural and human-related factors linked to the susceptibility and vulnerability of basin-fill aquifers to contamination.Basin-fill aquifers occur in about 200,000 mi2 of the 410,000 mi2 SWPA study area and are the primary source of groundwater supply for cities and agricultural communities. Four of the principal aquifers or aquifer systems of the United States are included in the basin-fill aquifers of the study area: (1) the Basin and Range basin-fill aquifers in California, Nevada, Utah, and Arizona; (2) the Rio Grande aquifer system in New Mexico and Colorado; (3) the California Coastal Basin aquifers; and (4) the Central Valley aquifer system in California. Because of the generally limited availability of surface-water supplies in the arid to semiarid climate, cultural and economic activities in the Southwest are particularly dependent on supplies of good-quality groundwater. Irrigation and public-supply withdrawals from basin-fill aquifers in the study area account for about one quarter of the total withdrawals from all aquifers in the United States.Many factors influence the quality of groundwater in the 15 case-study basins, but some common factors emerge from the basin summaries presented in this report. These factors include the chemical composition of the recharge water, consolidated rock geology and composition of aquifer materials derived from consolidated rock, and land and water use. The major water-quality issues in many of the developed case-study basins are increased concentrations of dissolved solids, nitrate, and VOCs in groundwater as a result of human activities.The information presented and the citations listed in this report serve as a resource for those interested in the groundwater-flow systems in the NAWQA case-study basins. The summaries of water-development history, hydrogeology, conceptual understanding of the groundwater system under both predevelopment and modern conditions, and effects of natural and human-related factors on groundwater quality presented in the sections on each basin also serve as a foundation for the synthesis and modeling phases of the SWPA regional study.

Hydrogeologic framework and groundwater conditions of the Ararat Basin in Armenia

USGS Publications Warehouse

Valder, Joshua F.; Carter, Janet M.; Medler, Colton J.; Thompson, Ryan F.; Anderson, Mark T.

2018-01-17

Armenia is a landlocked country located in the mountainous Caucasus region between Asia and Europe. It shares borders with the countries of Georgia on the north, Azerbaijan on the east, Iran on the south, and Turkey and Azerbaijan on the west. The Ararat Basin is a transboundary basin in Armenia and Turkey. The Ararat Basin (or Ararat Valley) is an intermountain depression that contains the Aras River and its tributaries, which also form the border between Armenia and Turkey and divide the basin into northern and southern regions. The Ararat Basin also contains Armenia’s largest agricultural and fish farming zone that is supplied by high-quality water from wells completed in the artesian aquifers that underlie the basin. Groundwater constitutes about 40 percent of all water use, and groundwater provides 96 percent of the water used for drinking purposes in Armenia. Since 2000, groundwater withdrawals and consumption in the Ararat Basin of Armenia have increased because of the growth of aquaculture and other uses. Increased groundwater withdrawals caused decreased springflow, reduced well discharges, falling water levels, and a reduction of the number of flowing artesian wells in the southern part of Ararat Basin in Armenia.In 2016, the U.S. Geological Survey and the U.S. Agency for International Development (USAID) began a cooperative study in Armenia to share science and field techniques to increase the country’s capabilities for groundwater study and modeling. The purpose of this report is to describe the hydrogeologic framework and groundwater conditions of the Ararat Basin in Armenia based on data collected in 2016 and previous hydrogeologic studies. The study area includes the Ararat Basin in Armenia. This report was completed through a partnership with USAID/Armenia in the implementation of its Science, Technology, Innovation, and Partnerships effort through the Advanced Science and Partnerships for Integrated Resource Development program and associated partners, including the Government of Armenia, Armenia’s Hydrogeological Monitoring Center, and the USAID Global Development Lab and its GeoCenter.The hydrogeologic framework of the Ararat Basin includes several basin-fill stratigraphic units consisting of interbedded dense clays, gravels, sands, volcanic basalts, and andesite deposits. Previously published cross sections and well lithologic logs were used to map nine general hydrogeologic units. Hydrogeologic units were mapped based on lithology and water-bearing potential. Water-level data measured in the water-bearing hydrogeologic units 2, 4, 6, and 8 in 2016 were used to create potentiometric surface maps. In hydrogeologic unit 2, the estimated direction of groundwater flow is from the west to north in the western part of the basin (away from the Aras River) and from north to south (toward the Aras River) in the eastern part of the basin. In hydrogeologic unit 4, the direction of groundwater flow is generally from west to east and north to south (toward the Aras River) except in the western part of the basin where groundwater flow is toward the north or northwest. Hydrogeologic unit 6 has the same general pattern of groundwater flow as unit 4. Hydrogeologic unit 8 is the deepest of the water-bearing units and is confined in the basin. Groundwater flow generally is from the south to north (away from the Aras River) in the western part of the basin and from west to east and north to south (toward the Aras River) elsewhere in the basin.In addition to water levels, personnel from Armenia’s Hydrogeological Monitoring Center also measured specific conductance at 540 wells and temperature at 2,470 wells in the Ararat Basin using U.S. Geological Survey protocols in 2016. The minimum specific conductance was 377 microsiemens per centimeter (μS/cm), the maximum value was 4,000 μS/cm, and the mean was 998 μS/cm. The maximum water temperature was 24.2 degrees Celsius. An analysis between water temperature and well depth indicated no relation; however, spatially, most wells with cooler water temperatures were within the 2016 pressure boundary or in the western part of the basin. Wells with generally warmer water temperatures were in the eastern part of the basin.Samples were collected from four groundwater sites and one surface-water site by the U.S. Geological Survey in 2016. The stable-isotope values were similar for all five sites, indicating similar recharge sources for the sampled wells. The Hrazdan River sample was consistent with the groundwater samples, indicating the river could serve as a source of recharge to the Ararat artesian aquifer.

Groundwater availability of the Denver Basin aquifer system, Colorado

USGS Publications Warehouse

Paschke, Suzanne

2011-01-01

The Denver Basin aquifer system is a critical water resource for growing municipal, industrial, and domestic uses along the semiarid Front Range urban corridor of Colorado. The confined bedrock aquifer system is located along the eastern edge of the Rocky Mountain Front Range where the mountains meet the Great Plains physiographic province. Continued population growth and the resulting need for additional water supplies in the Denver Basin and throughout the western United States emphasize the need to continually monitor and reassess the availability of groundwater resources. In 2004, the U.S. Geological Survey initiated large-scale regional studies to provide updated groundwater-availability assessments of important principal aquifers across the United States, including the Denver Basin. This study of the Denver Basin aquifer system evaluates the hydrologic effects of continued pumping and documents an updated groundwater flow model useful for appraisal of hydrologic conditions.

Groundwater-quality data in 12 GAMA study units: Results from the 2006–10 initial sampling period and the 2008–13 trend sampling period, California GAMA Priority Basin Project

USGS Publications Warehouse

Mathany, Timothy M.

2017-03-09

The Priority Basin Project (PBP) of the Groundwater Ambient Monitoring and Assessment (GAMA) program was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey in cooperation with the California State Water Resources Control Board. From 2004 through 2012, the GAMA-PBP collected samples and assessed the quality of groundwater resources that supply public drinking water in 35 study units across the State. Selected sites in each study unit were sampled again approximately 3 years after initial sampling as part of an assessment of temporal trends in water quality by the GAMA-PBP. Twelve of the study units, initially sampled during 2006–11 (initial sampling period) and sampled a second time during 2008–13 (trend sampling period) to assess temporal trends, are the subject of this report.The initial sampling was designed to provide a spatially unbiased assessment of the quality of untreated groundwater used for public water supplies in the 12 study units. In these study units, 550 sampling sites were selected by using a spatially distributed, randomized, grid-based method to provide spatially unbiased representation of the areas assessed (grid sites, also called “status sites”). After the initial sampling period, 76 of the previously sampled status sites (approximately 10 percent in each study unit) were randomly selected for trend sampling (“trend sites”). The 12 study units sampled both during the initial sampling and during the trend sampling period were distributed among 6 hydrogeologic provinces: Coastal (Northern and Southern), Transverse Ranges and Selected Peninsular Ranges, Klamath, Modoc Plateau and Cascades, and Sierra Nevada Hydrogeologic Provinces. For the purposes of this trend report, the six hydrogeologic provinces were grouped into two hydrogeologic regions based on location: Coastal and Mountain.The groundwater samples were analyzed for a number of synthetic organic constituents (volatile organic compounds, pesticides, and pesticide degradates), constituents of special interest (perchlorate and 1,2,3-trichloropropane), and natural inorganic constituents (nutrients, major and minor ions, and trace elements). Isotopic tracers (tritium, carbon-14, and stable isotopes of hydrogen and oxygen in water) also were measured to help identify processes affecting groundwater quality and the sources and ages of the sampled groundwater. More than 200 constituents and water-quality indicators were measured during the trend sampling period.Quality-control samples (blanks, replicates, matrix-spikes, and surrogate compounds) were collected at about one-third of the trend sites, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. On the basis of detections in laboratory and field blank samples collected by GAMA-PBP study units, including the 12 study units presented here, reporting levels for some groundwater results were adjusted in this report. Differences between replicate samples were mostly within acceptable ranges, indicating low variability in analytical results. Matrix-spike recoveries were largely within the acceptable range (70 to 130 percent).This study did not attempt to evaluate the quality of water delivered to consumers. After withdrawal, groundwater used for drinking water typically is treated, disinfected, and blended with other waters to achieve acceptable water quality. The comparison benchmarks used in this report apply to treated water that is served to the consumer, not to untreated groundwater. To provide some context for the results, however, concentrations of constituents measured in these groundwater samples were compared with benchmarks established by the U.S. Environmental Protection Agency and the State of California. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks.Most organic constituents that were detected in groundwater samples from the trend sites were found at concentrations less than health-based benchmarks. One volatile organic compound—perchloroethene—was detected at a concentration greater than the health-based benchmark in samples from one trend site during the initial and trend sampling periods. Chloroform was detected in at least 10 percent of the samples at trend sites in both sampling periods. Methyl tert-butyl ether was detected in samples from more than 10 percent of the trend sites during the initial sampling period. No pesticide or pesticide degradate was detected in greater than 10 percent of the samples from trend sites or at concentrations greater than their health-based benchmarks during either sampling period. Nutrients were not detected at concentrations greater than their health-based benchmarks during either sampling period.Most detections of major ions and trace elements in samples from trend sites were less than health-based benchmarks during both sampling periods. Arsenic and boron each were detected at concentrations greater than the health-based benchmark in samples from four trend sites during the initial and trend sampling periods. Molybdenum was detected in samples from four trend sites at concentrations greater than the health-based benchmark during both sampling periods. Samples from two of these trend sites had similar molybdenum concentrations, and two had substantially different concentrations during the initial and trend sampling periods. Uranium was detected at a concentration greater than the health-based benchmark only at two trend sites.

Influence of perched groundwater on base flow

USGS Publications Warehouse

Niswonger, Richard G.; Fogg, Graham E.

2008-01-01

Analysis with a three‐dimensional variably saturated groundwater flow model provides a basic understanding of the interplay between streams and perched groundwater. A simplified, layered model of heterogeneity was used to explore these relationships. Base flow contribution from perched groundwater was evaluated with regard to varying hydrogeologic conditions, including the size and location of the fine‐sediment unit and the hydraulic conductivity of the fine‐sediment unit and surrounding coarser sediment. Simulated base flow was sustained by perched groundwater with a maximum monthly discharge in excess of 15 L/s (0.6 feet3/s) over the length of the 2000‐m stream reach. Generally, the rate of perched‐groundwater discharge to the stream was proportional to the hydraulic conductivity of sediment surrounding the stream, whereas the duration of discharge was proportional to the hydraulic conductivity of the fine‐sediment unit. Other aspects of the perched aquifer affected base flow, such as the depth of stream penetration and the size of the fine‐sediment unit. Greater stream penetration decreased the maximum base flow contribution but increased the duration of contribution. Perched groundwater provided water for riparian vegetation at the demand rate but reduced the duration of perched‐groundwater discharge nearly 75%.

Brackish groundwater in the United States

USGS Publications Warehouse

Stanton, Jennifer S.; Anning, David W.; Brown, Craig J.; Moore, Richard B.; McGuire, Virginia L.; Qi, Sharon L.; Harris, Alta C.; Dennehy, Kevin F.; McMahon, Peter B.; Degnan, James R.; Böhlke, John Karl

2017-04-05

For some parts of the Nation, large-scale development of groundwater has caused decreases in the amount of groundwater that is present in aquifer storage and that discharges to surface-water bodies. Water supply in some areas, particularly in arid and semiarid regions, is not adequate to meet demand, and severe drought is affecting large parts of the United States. Future water demand is projected to heighten the current stress on groundwater resources. This combination of factors has led to concerns about the availability of freshwater to meet domestic, agricultural, industrial, mining, and environmental needs. To ensure the water security of the Nation, currently [2016] untapped water sources may need to be developed.Brackish groundwater is an unconventional water source that may offer a partial solution to current and future water demands. In support of the national census of water resources, the U.S. Geological Survey completed the national brackish groundwater assessment to better understand the occurrence and characteristics of brackish groundwater in the United States as a potential water resource. Analyses completed as part of this assessment relied on previously collected data from multiple sources; no new data were collected. Compiled data included readily available information about groundwater chemistry, horizontal and vertical extents and hydrogeologic characteristics of principal aquifers (regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water), and groundwater use. Although these data were obtained from a wide variety of sources, the compiled data are biased toward shallow and fresh groundwater resources; data representing groundwater that is at great depths and is saline were not as readily available.One of the most important contributions of this assessment is the creation of a database containing chemical characteristics and aquifer information for the known areas with brackish groundwater in the United States. Previously published digital data relating to brackish groundwater resources were limited to a small number of State- and regional-level studies. Data sources for this assessment ranged from single publications to large datasets and from local studies to national assessments. Geochemical data included concentrations of dissolved solids, major ions, trace elements, nutrients, and radionuclides as well as physical properties of the water (pH, temperature, and specific conductance). Additionally, the database provides selected well information (location, yield, depth, and contributing aquifer) necessary for evaluating the water resource.The assessment was divided into national-, regional-, and aquifer-scale analyses. National-scale analyses included evaluation of the three-dimensional distribution of observed dissolved-solids concentrations in groundwater, the three-dimensional probability of brackish groundwater occurrence, and the geochemical characteristics of saline (greater than or equal to 1,000 mg/L of dissolved solids) groundwater resources. Regional-scale analyses included a summary of the percentage of observed grid cell volume in the region that was occupied by brackish groundwater within the mixture of air, water, and rock for multiple depth intervals. Aquifer-scale analyses focused primarily on four regions that contained the largest amounts of observed brackish groundwater and included a generalized description of hydrogeologic characteristics from previously published work; the distribution of dissolved-solids concentrations; considerations for developing brackish groundwater resources, including a summary of other chemical characteristics that may limit the use of brackish groundwater and the ability of sampled wells producing brackish groundwater to yield useful amounts of water; and the amount of saline groundwater being used in 2010.

Groundwater-quality data in the northern Coast Ranges study unit, 2009: Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Dawson, Barbara J.; Shelton, Jennifer L.; Belitz, Kenneth

2011-01-01

This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, untreated groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is served to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwa

Hydrogeology of the Little Spokane River Basin, Spokane, Stevens, and Pend Oreille Counties, Washington

USGS Publications Warehouse

Kahle, Sue C.; Olsen, Theresa D.; Fasser, Elisabeth T.

2013-01-01

A study of the hydrogeologic framework of the Little Spokane River Basin was conducted to identify and describe the principal hydrogeologic units in the study area, their hydraulic characteristics, and general directions of groundwater movement. The Little Spokane River Basin includes an area of 679 square miles in northeastern Washington State covering parts of Spokane, Stevens, and Pend Oreille Counties. The groundwater system consists of unconsolidated sedimentary deposits and isolated, remnant basalt layers overlying crystalline bedrock. In 1976, a water resources program for the Little Spokane River was adopted into rule by the State of Washington, setting instream flows for the river and closing its tributaries to further uses. Spokane County representatives are concerned about the effects that additional groundwater development within the basin might have on the Little Spokane River and on existing groundwater resources. Information provided by this study will be used in future investigations to evaluate the effects of potential increases in groundwater withdrawals on groundwater and surface-water resources in the basin. The hydrogeologic framework consists of eight hydrogeologic units: the Upper aquifer, Upper confining unit, Lower aquifers, Lower confining unit, Wanapum basalt unit, Latah unit, Grande Ronde basalt unit, and Bedrock. The Upper aquifer is composed mostly of sand and gravel and varies in thickness from 4 to 360 ft, with an average thickness of 70 ft. The aquifer is generally finer grained in areas farther from main outwash channels. The estimated horizontal hydraulic conductivity ranges from 4.4 to 410,000 feet per day (ft/d), with a median hydraulic conductivity of 900 ft/d. The Upper confining unit is a low-permeability unit consisting mostly of silt and clay, and varies in thickness from 5 to 400 ft, with an average thickness of 100 ft. The estimated horizontal hydraulic conductivity ranges from 0.5 to 5,600 ft/d, with a median hydraulic conductivity of 8.2 ft/d. The Lower aquifers unit consists of localized confined aquifers or lenses consisting mostly of sand that occur at depth in various places in the basin; thickness of the unit ranges from 8 to 150 ft, with an average thickness of 50 ft. The Lower confining unit is a low-permeability unit consisting mostly of silt and clay; thickness of the unit ranges from 35 to 310 ft, with an average thickness of 130 ft. The Wanapum basalt unit includes the Wanapum Basalt of the Columbia River Basalt Group, thin sedimentary interbeds, and, in some places, overlying loess. The unit occurs as isolated remnants on the basalt bluffs in the study area and ranges in thickness from 7 to 140 ft, with an average thickness of 60 ft. The Latah unit is a mostly low-permeability unit consisting of silt, clay, and sand that underlies and is interbedded with the basalt units. The Latah unit ranges in thickness from 10 to 700 ft, with an average thickness of 250 ft. The estimated horizontal hydraulic conductivity ranges from 0.19 to 15 ft/d, with a median hydraulic conductivity of 0.56 ft/d. The Grande Ronde unit includes the Grande Ronde Basalt of the Columbia River Basalt Group and sedimentary interbeds. Unit thickness ranges from 30 to 260 ft, with an average thickness of 140 ft. The estimated horizontal hydraulic conductivity ranges from 0.03 to 13 ft/d, with a median hydraulic conductivity of 2.9 ft/d. The Bedrock unit is the only available source of groundwater where overlying sediments are absent or insufficiently saturated. The estimated horizontal hydraulic conductivity ranges from 0.01 to 5,000 ft/d, with a median hydraulic conductivity of 1.4 ft/d. The altitude of the buried bedrock surface ranges from about 2,200 ft to about 1,200 ft. Groundwater movement in the Little Spokane River Basin mimics the surface-water drainage pattern of the basin, moving from the topographically high tributary-basin areas toward the topographically lower valley floors. Water-level altitudes range from more than 2,700 ft to about 1,500 ft near the basin’s outlet.

Geomorphological control on podzolisation - An example from a tropical barrier island

NASA Astrophysics Data System (ADS)

Martinez, Pedro; Buurman, Peter; Lopes-Mazzetto, Josiane Millani; Giannini, Paulo César Fonseca; Schellekens, Judith; Vidal-Torrado, Pablo

2018-05-01

We investigated how the geomorphology of coastal barrier islands impacts soil hydrology and drainage at the landscape scale. Ilha Comprida is a Holocene barrier island with a 2.5 km-long cliff that is perpendicular to the coastal shore which provides an ideal condition to study the relation between age, relief, hydrology, and podzol morphology. Five geomorphic units were identified that differed in surface morphology and alignment of ridges and swales. Optical stimulated luminescence (OSL) dating showed that these geomorphic units had growth phases that decreased in age from west to east (Units I-V, from 5250 ± 820 to 325 ± 31 years ago, respectively). The geomorphic units were studied in two parallel 3 km transects on the southern part of the island. Along transect A-B, about 1 km from the southern shore, deep augerings were used to study sedimentary sequence and soil development, while on transect C-D on the southern shore, the continuous cliff exposure allowed more detailed morphological investigation. On all geomorphic units excluding the youngest, podzolisation has been the main soil-forming process. Groundwater level was monitored monthly for two years in 14 deep wells along transect A-B. Groundwater level during the formation of the B horizon was ascertained by determination of Fe. Podzol morphology (color of B horizon and its boundary with the E horizon) generally showed correlation to groundwater levels for both transects, except for the podzols in southwestern part of the island (Unit II). The podzols of Unit II showed an extremely thick (3 m) Bhm horizon devoid of Fe, indicating that they were formed under poor drainage conditions. However, soil morphology (undulating EB horizon boundary) and measured groundwater levels (below the B horizons) demonstrated that drainage has been improved. The extremely thick B horizon (3 m) in those podzols, which was formed in approximately 3000 years, and its genesis is explained by concentrated lateral flow of DOM-loaded groundwater due to the converging ridge alignments found in these units, in combination with a gradual uplift of the southwestern part of the island.

Estimated ground-water discharge by evapotranspiration from Death Valley, California, 1997-2001

USGS Publications Warehouse

DeMeo, Guy A.; Laczniak, Randell J.; Boyd, Robert A.; Smith, J. LaRue; Nylund, Walter E.

2003-01-01

The U.S. Geological Survey, in cooperation with the National Park Service and Inyo County, Calif., collected field data from 1997 through 2001 to accurately estimate the amount of annual ground-water discharge by evapotranspiration (ET) from the floor of Death Valley, California. Multispectral satellite-imagery and National Wetlands Inventory data are used to delineate evaporative ground-water discharge areas on the Death Valley floor. These areas are divided into five general units where ground-water discharge from ET is considered to be significant. Based upon similarities in soil type, soil moisture, vegetation type, and vegetation density; the ET units are salt-encrusted playa (21,287 acres), bare-soil playa (75,922 acres), low-density vegetation (6,625 acres), moderate-density vegetation (5,019 acres), and high-density vegetation (1,522 acres). Annual ET was computed for ET units with micrometeorological data which were continuously measured at six instrumented sites. Total ET was determined at sites that were chosen for their soil- and vegetated-surface conditions, which include salt-encrusted playa (extensive salt encrustation) 0.17 feet per year, bare-soil playa (silt and salt encrustation) 0.21 feet per year, pickleweed (pickleweed plants, low-density vegetation) 0.60 feet per year, Eagle Borax (arrowweed plants and salt grass, moderate-density vegetation) 1.99 feet per year, Mesquite Flat (mesquite trees, high-density vegetation) 2.86 feet per year, and Mesquite Flat mixed grasses (mixed meadow grasses, high-density vegetation) 3.90 feet per year. Precipitation, flooding, and ground-water discharge satisfy ET demand in Death Valley. Ground-water discharge is estimated by deducting local precipitation and flooding from cumulative ET estimates. Discharge rates from ET units were not estimated directly because the range of vegetation units far exceeded the five specific vegetation units that were measured. The rate of annual ground-water discharge by ET for each ET unit was determined by fitting the annual ground-water ET for each site with the variability in vegetation density in each ET unit. The ET rate representing the midpoint of each ET unit was used as the representative value. The rate of annual ground-water ET for the playa sites did not require scaling in this manner. Annual ground-water discharge by ET was determined for all five ET units: salt-encrusted playa (0.13 foot), bare-soil playa (0.15 foot), low-density vegetation (1.0 foot), moderate-density vegetation (2.0 feet), and high-density vegetation (3.0 feet), and an area of vegetation or bare soil not contributing to ground-water discharge unclassified (0.0 foot). The total ground-water discharge from ET for the Death Valley floor is about 35,000 acre-feet and was computed by summing the products of the area of each ET unit multiplied by a corresponding ET rate for each unit.

Assessing groundwater policy with coupled economic-groundwater hydrologic modeling

NASA Astrophysics Data System (ADS)

Mulligan, Kevin B.; Brown, Casey; Yang, Yi-Chen E.; Ahlfeld, David P.

2014-03-01

This study explores groundwater management policies and the effect of modeling assumptions on the projected performance of those policies. The study compares an optimal economic allocation for groundwater use subject to streamflow constraints, achieved by a central planner with perfect foresight, with a uniform tax on groundwater use and a uniform quota on groundwater use. The policies are compared with two modeling approaches, the Optimal Control Model (OCM) and the Multi-Agent System Simulation (MASS). The economic decision models are coupled with a physically based representation of the aquifer using a calibrated MODFLOW groundwater model. The results indicate that uniformly applied policies perform poorly when simulated with more realistic, heterogeneous, myopic, and self-interested agents. In particular, the effects of the physical heterogeneity of the basin and the agents undercut the perceived benefits of policy instruments assessed with simple, single-cell groundwater modeling. This study demonstrates the results of coupling realistic hydrogeology and human behavior models to assess groundwater management policies. The Republican River Basin, which overlies a portion of the Ogallala aquifer in the High Plains of the United States, is used as a case study for this analysis.

Status and understanding of groundwater quality in the North San Francisco Bay groundwater basins, 2004

USGS Publications Warehouse

Kulongoski, Justin T.; Belitz, Kenneth; Landon, Matthew K.; Farrar, Christopher

2010-01-01

Groundwater quality in the approximately 1,000-square-mile (2,590-square-kilometer) North San Francisco Bay study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in northern California in Marin, Napa, and Sonoma Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA North San Francisco Bay study was designed to provide a spatially unbiased assessment of untreated groundwater quality in the primary aquifer systems. The assessment is based on water-quality and ancillary data collected by the USGS from 89 wells in 2004 and water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer systems (hereinafter referred to as primary aquifers) were defined by the depth interval of the wells listed in the CDPH database for the North San Francisco Bay study unit. The quality of groundwater in shallower or deeper water-bearing zones may differ from that in the primary aquifers; shallower groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifers of the North San Francisco Bay study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California benchmarks. A relative-concentration greater than (>) 1.0 indicates a concentration above a benchmark, and less than or equal to (=) 1.0 indicates a concentration equal to or below a benchmark. Relative-concentrations of organic and special interest constituents were classified as ?high? (relative-concentration > 1.0), ?moderate? (0.1 1.0), ?moderate? (0.5 < relative-concentration = 1.0), or ?low? (relative-concentration = 0.5). Aquifer-scale proportion was used as a metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the primary aquifers that have a relative-concentration greater than 1.0; proportion is calculated on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifers that have moderate and low relative-concentrations, respectively. Two statistical approaches-grid-based and spatially-weighted-were used to evaluate aquifer-scale proportion for individual constituents and classes of constituents. Grid-based and spatially-weighted estimates were comparable in the North San Francisco Bay study unit (90-percent confidence intervals). For inorganic constituents with human-health benchmarks, relative-concentrations were high in 14.0 percent of the primary aquifers, moderate in 35.8 percent, and low in 50.2 percent. The high aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of arsenic (10.0 percent), boron (4.1 percent), and lead (1.6 percent). In contrast, relative-concentrations of organic constituents (one or more) were high in 1.4 percent, moderate in 4.9 percent, and low in 93.7 percent (not detected in 64.8 percent) of the primary aquifers. The high aquifer-scale proport

The National Water-Quality Assessment Program of the United States: Strategies for Monitoring Trends and Results from the First Two Decades of Study: 1991-2011

NASA Astrophysics Data System (ADS)

Lindsey, B.; McMahon, P.; Rupert, M.; Tesoriero, J.; Starn, J.; Anning, D.; Green, C.

2012-04-01

The U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program was implemented in 1991 to provide long-term, consistent, and comparable information on the quality of surface and groundwater resources of the United States. Findings are used to support national, regional, state, and local information needs with respect to water quality. The three main goals of the program are to 1) assess the condition of the nation's streams, rivers, groundwater, and aquatic systems; 2) assess how conditions are changing over time; and 3) determine how natural features and human activities affect these conditions, and where those effects are most pronounced. As data collection progressed into the second decade, the emphasis of the interpretation of the data has shifted from primarily understanding status, to evaluation of trends. The program has conducted national and regional evaluations of change in the quality of water in streams, rivers, groundwater, and health of aquatic systems. Evaluating trends in environmental systems requires complex analytical and statistical methods, and a periodic re-evaluation of the monitoring methods used to collect these data. Examples given herein summarize the lessons learned from the evaluation of changes in water quality during the past two decades with an emphasis on the finding with respect to groundwater. The analysis of trends in groundwater is based on 56 well networks located in 22 principal aquifers of the United States. Analysis has focused on 3 approaches: 1) a statistical analysis of results of sampling over various time scales, 2) studies of factors affecting trends in groundwater quality, and 3) use of models to simulate groundwater trends and forecast future trends. Data collection for analysis of changes in groundwater-quality has focused on decadal resampling of wells. Understanding the trends in groundwater quality and the factors affecting those trends has been conducted using quarterly sampling, biennial sampling, and more recently continuous monitoring of selected parameters in a small number of wells. Models such as MODFLOW have been used for simulation and forecasting of future trends. Important outcomes from the groundwater-trends studies include issues involving statistics, sampling frequency, changes in laboratory analytical methods over time, the need for groundwater age-dating information, the value of understanding geochemical conditions and contaminant degradation, the need to understand groundwater-surface water interaction, and the value of modeling in understanding trends and forecasting potential future conditions. Statistically significant increases in chloride, dissolved solids, and nitrate concentrations were found in a large number of well networks over the first decadal sampling period. Statistically significant decreases of chloride, dissolved solids, and nitrate concentrations were found in a very small number of networks. Trends in surface-water are analyzed within 8 large major river basins within the United States with a focus on issues of regional importance. Examples of regional surface-water issues include an analysis of trends in dissolved solids in the Southeastern United States, trends in pesticides in the north-central United States, and trends in nitrate in the Mississippi River Basin. Evaluations of ecological indicators of water quality include temporal changes in stream habitat, and aquatic-invertebrate and fish assemblages.

Hydrogeologic framework and estimates of ground-water volumes in Tertiary and upper Cretaceous hydrogeologic units in the Powder River basin, Wyoming

USGS Publications Warehouse

Hinaman, Kurt

2005-01-01

The Powder River Basin in Wyoming and Montana is an important source of energy resources for the United States. Coalbed methane gas is contained in Tertiary and upper Cretaceous hydrogeologic units in the Powder River Basin. This gas is released when water pressure in coalbeds is lowered, usually by pumping ground water. Issues related to disposal and uses of by-product water from coalbed methane production have developed, in part, due to uncertainties in hydrologic properties. One hydrologic property of primary interest is the amount of water contained in Tertiary and upper Cretaceous hydrogeologic units in the Powder River Basin. The U.S. Geological Survey, in cooperation with the Bureau of Land Management, conducted a study to describe the hydrogeologic framework and to estimate ground-water volumes in different facies of Tertiary and upper Cretaceous hydrogeologic units in the Powder River Basin in Wyoming. A geographic information system was used to compile and utilize hydrogeologic maps, to describe the hydrogeologic framework, and to estimate the volume of ground water in Tertiary and upper Cretaceous hydrogeologic units in the Powder River structural basin in Wyoming. Maps of the altitudes of potentiometric surfaces, altitudes of the tops and bottoms of hydrogeologic units, thicknesses of hydrogeologic units, percent sand of hydrogeologic units, and outcrop boundaries for the following hydrogeologic units were used: Tongue River-Wasatch aquifer, Lebo confining unit, Tullock aquifer, Upper Hell Creek confining unit, and the Fox Hills-Lower Hell Creek aquifer. Literature porosity values of 30 percent for sand and 35 percent for non-sand facies were used to calculate the volume of total ground water in each hydrogeologic unit. Literature specific yield values of 26 percent for sand and 10 percent for non-sand facies, and literature specific storage values of 0.0001 ft-1 (1/foot) for sand facies and 0.00001 ft-1 for non-sand facies, were used to calculate a second volume of ground water for each hydrogeologic unit. Significant figure considerations limited estimates of ground-water volumes to two significant digits. A total ground-water volume of 2.0x1014 ft3 (cubic feet) was calculated using porosity values, and a total ground-water volume of 3.6x1013 ft3 was calculated using specific yield and specific storage values. These results are consistent with retention properties, which would have some of the total water being retained in the sediments. Sensitivity analysis shows that the estimates of ground-water volume are most sensitive to porosity. The estimates also are sensitive to confined thickness and saturated thickness. Better spatial information for hydrogeologic units could help refine the ground-water volume estimates.

Modeling the Effects of Groundwater-fed Irrigation on Terrestrial Hydrology over the Conterminous United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leng, Guoyong; Huang, Maoyi; Tang, Qiuhong

2014-06-01

Human alteration of the land surface hydrologic cycle is substantial. Recent studies suggest that local water management practices including groundwater pumping and irrigation could significantly alter the quantity and distribution of water in the terrestrial system, with potential impacts on weather and climate through land-atmosphere feedbacks. In this study, we incorporated a groundwater withdrawal scheme into the Community Land Model version 4 (CLM4). To simulate the impact of irrigation realistically, we calibrated the CLM4 simulated irrigation amount against observations from agriculture census at the county scale over the conterminous United States (CONUS). The water used for irrigation was then removedmore » from the surface runoff and groundwater aquifer according to a ratio determined from the county-level agricultural census data. Based on the simulations, the impact of groundwater withdrawals for irrigation on land surface and subsurface fluxes were investigated. Our results suggest that the impacts of irrigation on latent heat flux and potential recharge when water is withdrawn from surface water alone or from both surface and groundwater are comparable and local to the irrigation areas. However, when water is withdrawn from groundwater for irrigation, greater effects on the subsurface water balance were found, leading to significant depletion of groundwater storage in regions with low recharge rate and high groundwater exploitation rate. Our results underscore the importance of local hydrologic feedbacks in governing hydrologic response to anthropogenic change in CLM4 and the need to more realistically simulate the two-way interactions among surface water, groundwater, and atmosphere to better understand the impacts of groundwater pumping on irrigation efficiency and climate.« less

Geologic and hydrogeologic characteristics of the Ogallala Formation and White River Group, Belvoir Ranch near Cheyenne, Laramie County, Wyoming

USGS Publications Warehouse

Bartos, Timothy T.; Diehl, Sharon F.; Hallberg, Laura L.; Webster, Daniel M.

2014-01-01

The geologic and hydrogeologic characteristics of Tertiary lithostratigraphic units (Ogallala Formation and White River Group) that typically compose or underlie the High Plains aquifer system in southeastern Wyoming were described physically and chemically, and evaluated at a location on the Belvoir Ranch in Laramie County, Wyoming. On the basis of this characterization and evaluation, three Tertiary lithostratigraphic units were identified using physical and chemical characteristics determined during this study and previous studies, and these three units were determined to be correlative with three identified hydrogeologic units composing the groundwater system at the study site—a high-yielding aquifer composed of the entire saturated thickness of the heterogeneous and coarse-grained fluvial sediments assigned to the Ogallala Formation (Ogallala aquifer); an underlying confining unit composed primarily of very fine-grained volcaniclastic sediments and mudrocks assigned to the Brule Formation of the White River Group and some additional underlying sediments that belong to either the Brule or Chadron Formation, or both (Brule confining unit); and an underlying low-yielding aquifer composed primarily of poorly sorted fluvial sediments assigned to the Chadron Formation of the White River Group (Chadron aquifer). Despite widely varying sediment heterogeneity and consolidation, some limited hydraulic connection throughout the full vertical extent of the Ogallala aquifer was indicated but not conclusively proven by interpretation of similar chemical and isotopic characteristics, modern apparent groundwater ages, and similar hydraulic-head responses measured continuously in two Ogallala aquifer monitoring wells installed for this study at two different widely separated (83 feet) depth intervals. Additional work beyond the scope of this study, such as aquifer tests, would be required to conclusively determine hydraulic connection within the Ogallala aquifer. Groundwater levels (hydraulic heads) measured continuously using water-level recorders in both monitoring wells completed in the Ogallala aquifer showed a consistent strong upward vertical gradient in the Ogallala aquifer, indicating the potential for water to move from deeper to shallower parts of the aquifer, regardless of the time of year and the presumed effects of pumping of public-supply and industrial wells in the area. Continuous measurement of groundwater levels in the shallowest monitoring well, installed near the water table, and examination of subsequently constructed water-level hydrographs indicated substantial groundwater recharge is likely during the spring of 2009 and 2010 from the ephemeral stream (Lone Tree Creek) located adjacent to the study site that flows primarily in response to spring snowmelt from the adjacent Laramie Mountains and surface runoff from precipitation events. Using the water-table fluctuation method, groundwater recharge was estimated to be about 13 inches for the period beginning in early October 2009 and ending in late June 2010, and about 4 inches for the period beginning in March 2011 and ending in early July 2011. Comparison of previously measured groundwater levels (hydraulic heads) and groundwater-quality characteristics in nearby monitoring wells completed in the Chadron aquifer with those measured in the two monitoring wells installed for this study in the Ogallala aquifer, combined with detailed lithologic characterization, strongly indicated the Brule confining unit hydraulically confines and isolates the Chadron aquifer from the overlying Ogallala aquifer, thus likely limiting hydraulic connection between the two units. Consequently, because of the impermeable nature of the Brule confining unit and resulting hydraulic separation of the Ogallala and Chadron aquifers, and compared with local and regional hydrostratigraphic definitions of the High Plains aquifer system, the groundwater system in Tertiary lithostratigraphic units overlying the Upper Cretaceous Lance Formation at the location studied on the Belvoir Ranch was defined as being composed of, from shallowest to deepest, the High Plains aquifer system (high-yielding Ogallala aquifer only, composed of the saturated Ogallala Formation); the Brule confining unit composed of the Brule Formation of the White River Group and an underlying fine-grained depth interval with sediments that belong to either the Brule or Chadron Formation, or both; and the low-yielding Chadron aquifer (composed of poorly sorted coarse-grained sediments with substantial fine-grained matrix material assigned to the Chadron Formation of the White River Group).

Geologic Setting and Hydrogeologic Units of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

USGS Publications Warehouse

Kahle, Sue C.; Olsen, Theresa D.; Morgan, David S.

2009-01-01

The Columbia Plateau Regional Aquifer System (CPRAS) covers approximately 44,000 square miles of northeastern Oregon, southeastern Washington, and western Idaho. The area supports a $6 billion per year agricultural industry, leading the Nation in production of apples and nine other commodities (State of Washington Office of Financial Management, 2007; U.S. Department of Agriculture, 2007). Groundwater availability in the aquifers of the area is a critical water-resource management issue because the water demand for agriculture, economic development, and ecological needs is high. The primary aquifers of the CPRAS are basalts of the Columbia River Basalt Group (CRBG) and overlying basin-fill sediments. Water-resources issues that have implications for future groundwater availability in the region include (1) widespread water-level declines associated with development of groundwater resources for irrigation and other uses, (2) reduction in base flow to rivers and associated effects on temperature and water quality, and (3) current and anticipated effects of global climate change on recharge, base flow, and ultimately, groundwater availability. As part of a National Groundwater Resources Program, the U.S. Geological Survey began a study of the CPRAS in 2007 with the broad goals of (1) characterizing the hydrologic status of the system, (2) identifying trends in groundwater storage and use, and (3) quantifying groundwater availability. The study approach includes documenting changes in the status of the system, quantifying the hydrologic budget for the system, updating the regional hydrogeologic framework, and developing a groundwater-flow simulation model for the system. The simulation model will be used to evaluate and test the conceptual model of the system and later to evaluate groundwater availability under alternative development and climate scenarios. The objectives of this study were to update the hydrogeologic framework for the CPRAS using the available geologic mapping and well information and to develop a digital, three-dimensional hydrogeologic model that could be used as the basis of a groundwater-flow model. This report describes the principal geologic and hydrogeologic units of the CPRAS and geologic map and well data that were compiled as part of the study. The report also describes simplified regional hydrogeologic sections and unit extent maps that were used to conceptualize the framework prior to development of the digital 3-dimensional framework model.

Sandcastle Moats and Petunia Bed Holes. A Book about Groundwater.

ERIC Educational Resources Information Center

Nickinson, Pat

This book provides five instructional units on groundwater. Units included are: (1) "Where's the Groundwater?" (describing the concepts of a saturated zone, water table, hydrologic cycle, recharge and discharge, core of depression, subsidence, and saltwater intrusion); (2) "How Does It Travel?" (discussing porosity,…

Evaluation of water stress and groundwater storage using a global hydrological model

NASA Astrophysics Data System (ADS)

Shiojiri, D.; Tanaka, K.; Tanaka, S.

2017-12-01

United Nations reported the number of people will reach 9.7 billion in 2050, and this rapid growth of population will increase water use. To prevent global water shortage, it is important to identify the problematic areas in order to maintain water resources sustainability. Moreover, groundwater availability is decreasing in some areas due to excessive groundwater extraction compared to the groundwater recharge capacity. The development of a hydrological model that can simulate the current status of the world's water resources represents an important tool to achieve sustainable water resources management. In this study, a global hydrological simulation is conducted at a 20km spatial resolution using the land surface model SiBUC, which is coupled to the river routing model HydroBEAM. In the river routing model, we evaluate water stress by comparing the excess of water demand with the river water demand. Areas with high water stress are seen in United States, India, and east part of China; however, for the case of Africa the overall water stress is zero. This could be because rain-fed agriculture is the norm in Africa and thus irrigation water demand is low, which affects water stress index. Sustainability of groundwater resources is also evaluated in the river routing model by setting a virtual groundwater tank. When the amount of groundwater withdrawal constantly exceeds groundwater recharge, the volume in the tank falls below zero and the area is regarded as unsustainable in terms of groundwater usage. Such areas are mostly seen in central United States, northeast China, the region between northwest India and Pakistan. In the simulation with SiBUC, the amount of groundwater recharge is assumed as the proportion of water that flows from the second to the third soil layer. This proportion will be estimated by comparing monthly variations of terrestrial water storage (TWS) derived from the observations of the GRACE satellite with the simulated TWS variations. From this comparison, the suitability of the simulated amount of groundwater will also assess.

Numerical simulation of groundwater flow in the Columbia Plateau Regional Aquifer System, Idaho, Oregon, and Washington

USGS Publications Warehouse

Ely, D. Matthew; Burns, Erick R.; Morgan, David S.; Vaccaro, John J.

2014-01-01

Groundwater pumping has increased substantially over the past 40–50 years; this increase resulted in declining water levels at depth and decreased base flows over much of the study area. The effects of pumping are mitigated somewhat by the increase of surface-water irrigation, especially in the shallow Overburden unit, and commingling wells in some areas. During dry to average years, groundwater pumping causes a net loss of groundwater in storage and current condition (2000–2007) groundwater pumping exceeds recharge in all but the wettest of years.

Status and understanding of groundwater quality in the northern San Joaquin Basin, 2005

USGS Publications Warehouse

Bennett, George L.; Fram, Miranda S.; Belitz, Kenneth; Jurgens, Bryant C.

2010-01-01

Groundwater quality in the 2,079 square mile Northern San Joaquin Basin (Northern San Joaquin) study unit was investigated from December 2004 through February 2005 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001 that was passed by the State of California and is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The Northern San Joaquin study unit was the third study unit to be designed and sampled as part of the Priority Basin Project. Results of the study provide a spatially unbiased assessment of the quality of raw (untreated) groundwater, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 61 wells in parts of Alameda, Amador, Calaveras, Contra Costa, San Joaquin, and Stanislaus Counties; 51 of the wells were selected using a spatially distributed, randomized grid-based approach to provide statistical representation of the study area (grid wells), and 10 of the wells were sampled to increase spatial density and provide additional information for the evaluation of water chemistry in the study unit (understanding/flowpath wells). The primary aquifer systems (hereinafter, primary aquifers) assessed in this study are defined by the depth intervals of the wells in the California Department of Public Health database for each study unit. The quality of groundwater in shallow or deep water-bearing zones may differ from quality of groundwater in the primary aquifers; shallow groundwater may be more vulnerable to contamination from the surface. Two types of assessments were made: (1) status, assessment of the current quality of the groundwater resource; and (2) understanding, identification of the natural and human factors affecting groundwater quality. Relative-concentrations (sample concentrations divided by benchmark concentrations) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. Benchmarks used in this study were either health-based (regulatory and non-regulatory) or aesthetic based (non-regulatory). For inorganic constituents, relative-concentrations were classified as high (equal to or greater than 1.0), indicating relative-concentrations greater than benchmarks; moderate (equal to or greater than 0.5, and less than 1.0); or, low (less than 0.5). For organic and special- interest constituents [1,2,3-trichloropropane (1,2,3-TCP), N-nitrosodimethylamine (NDMA), and perchlorate], relative- concentrations were classified as high (equal to or greater than 1.0); moderate (equal to or greater than 0.1 and less than 1.0); or, low (less than 0.1). Aquifer-scale proportion was used as the primary metric in the status assessment for groundwater quality. High aquifer- scale proportion is defined as the percentage of the primary aquifer with relative-concentrations greater than 1.0; moderate and low aquifer-scale proportions are defined as the percentage of the primary aquifer with moderate and low relative- concentrations, respectively. The methods used to calculate aquifer-scale proportions are based on an equal-area grid; thus, the proportions are areal rather than volumetric. Two statistical approaches - grid-based, which used one value per grid cell, and spatially weighted, which used the full dataset - were used to calculate aquifer-scale proportions for individual constituents and classes of constituents. The spatially weighted estimates of high aquifer-scale proportions were within the 90-percent confidence intervals of the grid-based estimates in all cases. The understanding assessment used statistical correlations between constituent relative-concentrations and

Ground-water hydrology of the Willamette basin, Oregon

USGS Publications Warehouse

Conlon, Terrence D.; Wozniak, Karl C.; Woodcock, Douglas; Herrera, Nora B.; Fisher, Bruce J.; Morgan, David S.; Lee, Karl K.; Hinkle, Stephen R.

2005-01-01

The Willamette Basin encompasses a drainage of 12,000 square miles and is home to approximately 70 percent of Oregon's population. Agriculture and population are concentrated in the lowland, a broad, relatively flat area between the Coast and Cascade Ranges. Annual rainfall is high, with about 80 percent of precipitation falling from October through March and less than 5 percent falling in July and August, the peak growing season. Population growth and an increase in cultivation of crops needing irrigation have produced a growing seasonal demand for water. Because many streams are administratively closed to new appropriations in summer, ground water is the most likely source for meeting future water demand. This report describes the current understanding of the regional ground-water flow system, and addresses the effects of ground-water development. This study defines seven regional hydrogeologic units in the Willamette Basin. The highly permeable High Cascade unit consists of young volcanic material found at the surface along the crest of the Cascade Range. Four sedimentary hydrogeologic units fill the lowland between the Cascade and Coast Ranges. Young, highly permeable coarse-grained sediments of the upper sedimentary unit have a limited extent in the floodplains of the major streams and in part of the Portland Basin. Extending over much of the lowland where the upper sedimentary unit does not occur, silts and clays of the Willamette silt unit act as a confining unit. The middle sedimentary unit, consisting of permeable coarse-grained material, occurs beneath the Willamette silt and upper sedimentary units and at the surface as terraces in the lowland. Beneath these units is the lower sedimentary unit, which consists of predominantly fine-grained sediments. In the northern part of the basin, lavas of the Columbia River basalt unit occur at the surface in uplands and beneath the basin-fill sedimentary units. The Columbia River basalt unit contains multiple productive water-bearing zones. A basement confining unit of older marine and volcanic rocks of low permeability underlies the basin and occurs at land surface in the Coast Range and western part of the Cascade Range. Most recharge in the basin is from infiltration of precipitation, and the spatial distribution of recharge mimics the distribution of precipitation, which increases with elevation. Basinwide annual mean recharge is estimated to be 22 inches. Rain and snowmelt easily recharge into the permeable High Cascade unit and discharge within the High Cascade area. Most recharge in the Coast Range and western part of the Cascade Range follows short flowpaths through the upper part of the low permeability material and discharges to streams within the mountains. Consequently, recharge in the Coast and Ranges is not available as lateral ground-water flow into the lowland, where most ground-water use occurs. Within the lowland, annual mean recharge is 16 inches and most recharge occurs from November to April, when rainfall is large and evapotranspiration is small. From May to October recharge is negligible because precipitation is small and evapotranspiration is large. Discharge of ground water is mainly to streams. Ground-water discharge is a relatively large component of flow in streams that drain the High Cascade unit and parts of the Portland Basin where permeable units are at the surface. In streams that do not head in the High Cascade area, streamflow is generally dominated by runoff of precipitation. Ground-water in the permeable units in the lowland discharges to the major streams where there is a good hydraulic connection between aquifers and streams. Ground-water discharge to smaller streams, which flow on the less permeable Willamette silt unit, is small and mostly from the Willamette silt unit. Most ground-water withdrawals occur within the lowland. Irrigation is the largest use of ground water, accounting for 240,000 acre feet of withdrawals, or 81 p

Progress Toward Cleanup of Operable Unit 1 Groundwater at the US DOE Mound, Ohio, Site: Success of a Phase-Combined Remedy – 15310

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hooten, Gwendolyn; Cato, Rebecca; Looney, Brian

2015-03-01

Operable Unit 1 (OU-1) soil and groundwater have been affected by volatile organic compounds (VOC) Present groundwater remedy is collection, treatment, and disposal (pump and treat [P&T]) Several combinations of technologies were used to address soil and groundwater contamination Monitored natural attenuation (MNA) is a viable alternative Majority of source term has been excavated VOC concentrations in groundwater have decreased Attenuation mechanisms have been observed in the subsurface at OU-1

Technical/ administrative options for managing tritium MCL exceedances in P-area groundwater and Steel Creek

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, J.

2017-04-01

This white paper was requested by the Core Team (United States Department of Energy [USDOE], United States Environmental Protection Agency [USEPA], and South Carolina Department of Health and Environmental Control [SCDHEC]) at the P-Area Groundwater (PAGW) Operable Unit (OU) Scoping Meeting held in January 2017 to discuss recent data and potential alternatives in support of a focused Corrective Measures Study/Feasibility Study (CMS/FS). This white paper presents an overview of the problem, and a range of technical and administrative options for addressing the tritium contamination in groundwater and Steel Creek. As tritium cannot be treated practicably, alternatives are limited to mediamore » transfer, containment and natural attenuation principally relying on radioactive decay. Using other groundwater OU decisions involving tritium as precedent, Savannah River Nuclear Solutions (SRNS) recommends that final tritium alternatives be evaluated in a CMS/FS, understanding that the likely preferred remedy will include natural attenuation with land use controls (LUCs). This is based on the inability to significantly reduce tritium impact to Steel Creek using an engineered solution as compared to natural attenuation. The timing of this evaluation could be conducted concurrently with the final remedy evaluation for volatile organic compounds (VOCs).« less

Hydrogeologic framework, groundwater and surface-water systems, land use, pumpage, and water budget of the Chamokane Creek basin, Stevens County, Washington

USGS Publications Warehouse

Kahle, Sue C.; Taylor, William A.; Lin, Sonja; Sumioka, Steven S.; Olsen, Theresa D.

2010-01-01

A study of the water resources of the unconsolidated groundwater system of the Chamokane Creek basin was conducted to determine the hydrogeologic framework, interactions of shallow and deep parts of the groundwater system with each other and the surface-water system, changes in land use and land cover, and water-use estimates. Chamokane Creek basin is a 179 mi2 area that borders and partially overlaps the Spokane Indian Reservation in southern Stevens County in northeastern Washington State. Aquifers within the Chamokane Creek basin are part of a sequence of glaciofluvial and glaciolacustrine sediment that may reach total thicknesses of about 600 ft. In 1979, most of the water rights in the Chamokane Creek basin were adjudicated by the United States District Court requiring regulation in favor of the Spokane Tribe of Indians' senior water right. The Spokane Tribe, the State of Washington, and the United States are concerned about the effects of additional groundwater development within the basin on Chamokane Creek. Information provided by this study will be used to evaluate the effects of potential increases in groundwater withdrawals on groundwater and surface-water resources within the basin. The hydrogeologic framework consists of six hydrogeologic units: The Upper outwash aquifer, the Landslide Unit, the Valley Confining Unit, the Lower Aquifer, the Basalt Unit, and the Bedrock Unit. The Upper outwash aquifer occurs along the valley floors of the study area and consists of sand, gravel, cobbles, boulders, with minor silt and (or) clay interbeds in places. The Lower aquifer is a confined aquifer consisting of sand and gravel that occurs at depth below the Valley confining unit. Median horizontal hydraulic conductivity values for the Upper outwash aquifer, Valley confining unit, Lower aquifer, and Basalt unit were estimated to be 540, 10, 19, and 3.7 ft/d, respectively. Many low-flow stream discharge measurements at sites on Chamokane Creek and its tributaries were at or near zero flow. The most notable exception is where Chamokane Creek is supported by discharge of large springs from the Upper outwash aquifer in the southern part of the basin. Most high-flow measurements indicated gains in streamflow (groundwater discharging to the stream). Large streamflow losses, however, were recorded near the north end of Walkers Prairie where streamflow directly recharges the Upper outwash aquifer. The similarity in seasonal water-level fluctuations in the Upper outwash aquifer and the Lower aquifer indicate that these systems may be fairly well connected. Land use and land cover change analysis indicates that Chamokane Creek basin has been dominated by forests with some pasture and agricultural lands with sparse residential development from the 1980s to present. Loss in forest cover represents the largest change in land cover in the basin between 1987 and 2009. This appears to be mostly due to forestry activities, especially in the northern part of the basin. Since 1987, more than 18,000 acres of evergreen forest have been logged and are at various stages of regrowth. Estimated average annual total groundwater pumpage in the basin increased from 224 million gallons per year (Mgal/yr) in 1980 to 1,330 Mgal/yr in 2007. The largest withdrawals during 2007 were to supply two fish hatcheries, with a combined total annual pumpage of about 1,150 Mgal. Annual groundwater pumpage values from 1980 through 2007 for the study area ranged from 21.1 to 28.9 Mgal/yr for domestic wells and 0.38 to 23.7 Mgal/yr for public supply. An approximate water budget for a typical year in the Chamokane Creek basin indicates that 19.6 in. of precipitation are balanced by 4.7 in. of streamflow discharge from the basin, and 14.9 in. of evapotranspiration.

Groundwater Quality in the Central Eastside San Joaquin Valley, California

USGS Publications Warehouse

Belitz, Kenneth; Landon, Matthew K.

2010-01-01

The Central Eastside study unit is located in California's San Joaquin Valley. The 1,695 square mile study unit includes three groundwater subbasins: Modesto, Turlock, and Merced (California Department of Water Resources, 2003). The primary water-bearing units consist of discontinuous lenses of gravel, sand, silt, and clay, which are derived largely from the Sierra Nevada Mountains to the east. Public-supply wells provide most of the drinking water supply in the Central Eastside. Consequently, the primary aquifer in the Central Eastside study unit is defined as that part of the aquifer corresponding to the perforated interval of wells listed in the California Department of Public Health database. Public-supply wells are typically drilled to depths of 200 to 350 feet, consist of solid casing from the land surface to a depth of about 100 to 200 feet, and they are perforated below the solid casing. Water quality in the shallower and deeper parts of the aquifer system may differ from that in the primary aquifer. The Central Eastside study unit has hot and dry summers and cool, moist, winters. Average annual rainfall ranges from 11 to 15 inches. The Stanislaus, Tuolumne, and Merced Rivers, with headwaters in the Sierra Nevada Mountains, are the primary streams traversing the study unit. Land use in the study unit is approximately 59 percent (%) agricultural, 34% natural (primarily grassland), and 7% urban. The primary crops are almonds, walnuts, peaches, grapes, grain, corn, and alfalfa. The largest urban areas (2003 population in parentheses) are the cities of Modesto (206,872), Turlock (63,467), and Merced (69,512). Municipal water use accounts for about 5% of the total water use in the Central Eastside study unit, with the remainder used for irrigated agriculture. Groundwater accounts for about 75% of the municipal supply, and surface water accounts for about 25%. Recharge to the groundwater flow system is primarily from percolation of irrigation return, precipitation, seepage from reservoirs and rivers, and urban return (Burow and others, 2004; Phillips and others, 2007). The primary sources of discharge are pumping for irrigation and municipal supply, evaporation from areas with a shallow depth to water, and discharge to streams. Recharge at shallow depths and pumping from wells at greater depths causes downward movement of groundwater in the aquifer in the Central Eastside. This vertical movement of water has the potential to carry chemical constituents from shallow depths to the greater depths where supply wells commonly are perforated.

Status and understanding of groundwater quality in the Northern Coast Ranges study unit, 2009: California GAMA Priority Basin Project

USGS Publications Warehouse

Mathany, Timothy M.; Belitz, Kenneth

2015-01-01

Chloroform, simazine, and perchlorate were observed in the Interior Basins and Coastal Basins study areas, predominantly at shallow sites with top-of-perforation depths ≤70 feet below land surface, with modern water (post-1950s), and with oxic groundwater conditions.

Status and understanding of groundwater quality in the Santa Clara River Valley, 2007-California GAMA Priority Basin Project

USGS Publications Warehouse

Burton, Carmen A.; Montrella, Joseph; Landon, Matthew K.; Belitz, Kenneth

2011-01-01

Groundwater quality in the approximately 460-square-mile Santa Clara River Valley study unit was investigated from April through June 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project is conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board and the Lawrence Livermore National Laboratory. The Santa Clara River Valley study unit contains eight groundwater basins located in Ventura and Los Angeles Counties and is within the Transverse and Selected Peninsular Ranges hydrogeologic province. The Santa Clara River Valley study unit was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer system. The assessment is based on water-quality and ancillary data collected in 2007 by the USGS from 42 wells on a spatially distributed grid, and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system was defined as that part of the aquifer system corresponding to the perforation intervals of wells listed in the CDPH database for the Santa Clara River Valley study unit. The quality of groundwater in the primary aquifer system may differ from that in shallow or deep water-bearing zones; for example, shallow groundwater may be more vulnerable to surficial contamination. Eleven additional wells were sampled by the USGS to improve understanding of factors affecting water quality.The status assessment of the quality of the groundwater used data from samples analyzed for anthropogenic constituents, such as volatile organic compounds (VOCs) and pesticides, as well as naturally occurring inorganic constituents, such as major ions and trace elements. The status assessment is intended to characterize the quality of untreated groundwater resources in the primary aquifers of the Santa Clara River Valley study unit, not the quality of treated drinking water delivered to consumers. Relative-concentrations (sample concentration divided by health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California benchmarks. A relative-concentration greater than 1.0 indicates a concentration greater than a benchmark. For organic and special interest constituents, relative-concentrations were classified as high (greater than 1.0); moderate (greater than 0.1 and less than or equal to 1.0); and low (less than or equal to 0.1). For inorganic constituents, relative-concentrations were classified as high (greater than 1.0); moderate (greater than 0.5 and less than or equal to 1.0); and low (less than or equal to 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the areal percentage of the primary aquifer system with relative-concentrations greater than 1.0. Moderate and low aquifer-scale proportions are defined as the areal percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches, grid-based and spatially weighted, were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the Santa Clara River Valley study unit (within 90 percent confidence intervals). The status assessment showed that inorganic constituents were more prevalent and relative-concentrations were higher than for organic constituents. For inorganic constituents with human-health benchmarks, relative-concentrations (of one or more constituents) were high in 21 percent of the primary aquifer system areally, moderate in 30 percent, and low or not detected in 49 percent. Inorganic constituents with human-health benchmarks with high aquifer-scale proportions were nitrate (15 percent of the primary aquifer system), gross alpha radioactivity (14 percent), vanadium (3.4 percent), boron (3.2 percent), and arsenic (2.3 percent). For inorganic constituents with aesthetic benchmarks, relative-concentrations (of one or more constituents) were high in 54 percent of the primary aquifer system, moderate in 41 percent, and low or not detected in 4 percent. The inorganic constituents with aesthetic benchmarks with high aquifer-scale proportions were total dissolved solids (35 percent), sulfate (22 percent), manganese (38 percent), and iron (22 percent). In contrast, the results of the status assessment for organic constituents with human-health benchmarks showed that relative-concentrations were high in 0 percent (not detected above benchmarks) of the primary aquifer system, moderate in 2.4 percent, and low or not detected in 97 percent. Relative-concentrations of the special interest constituent, perchlorate, were moderate in 12 percent of the primary aquifer system and low or not detected in 88 percent. Relative-concentrations of two VOCs-carbon tetrachloride and trichloroethene (TCE)-were moderate in 2.4 percent of the primary aquifer system. One VOC-chloroform (water disinfection byproduct)-was detected in more than 10 percent of the primary aquifer system but at low relative-concentrations. Of the 88 VOCs and gasoline oxygenates analyzed, 71 were not detected. Pesticides were low or not detected in 100 percent of the primary aquifer system. Of the 118 pesticides and pesticide degradates analyzed, 13 were detected and 5 of those had human-health benchmarks. Two of these five pesticides-simazine and atrazine-were detected in more than 10 percent of the primary aquifer system. The second component of this study, the understanding assessment, was to identify the natural and human factors that affect groundwater quality on the basis of the evaluation of land use, physical characteristics of the wells, and geochemical conditions of the aquifer. Results from these analyses are used to explain the occurrence and distribution of selected constituents in the primary aquifer system of the Santa Clara River Valley study unit. The understanding assessment indicated that water quality varied spatially primarily in relation to depth, groundwater age, reduction-oxidation conditions, pH, and location in the regional groundwater flow system. High and moderate relative-concentrations of nitrate and low relative-concentrations of pesticides were correlated with shallow depths to top-of-perforation, and with high dissolved oxygen. Groundwater of modern and mixed ages had higher nitrate than pre-modern-age groundwater. Decreases in concentrations of total dissolved solids (TDS) and sulfate were correlated with increases in pH. This relationship probably indicates relations of these constituents with increasing depth across most of the Santa Clara River Valley study unit. Previous studies have indicated multiple sources of high concentrations of TDS and sulfate and multiple geochemical processes affecting these constituents in the Santa Clara River Valley study unit. Manganese and iron concentrations were highest in pre-modern-age groundwater at depth and in the downgradient area of the Santa Clara River Valley study unit (closest to the coastline), indicating the prevalence of reducing groundwater conditions in these aquifer zones.

Estimated use of water in the United States in 2005

USGS Publications Warehouse

Kenny, Joan F.; Barber, Nancy L.; Hutson, Susan S.; Linsey, Kristin S.; Lovelace, John K.; Maupin, Molly A.

2009-01-01

About 67 percent of fresh groundwater withdrawals in 2005 were for irrigation, and 18 percent were for public supply. More than half of fresh groundwater withdrawals in the United States in 2005 occurred in six States. In California, Texas, Nebraska, Arkansas, and Idaho, most of the fresh groundwater withdrawals were for irrigation. In Florida, 52 percent of all fresh groundwater withdrawals were for public supply, and 34 percent were for irrigation.

Groundwater studies in arid areas in Egypt using LANDSAT satellite images

NASA Technical Reports Server (NTRS)

Elshazly, E. M.; Abdelhady, M. A.; Elshazly, M. M.

1977-01-01

Various features are interpreted which have strong bearing on groundwater in the arid environment. These include the nature of geological and lithologic units, structural lineaments, present and old drainage systems, distribution and form of water pools, geomorphologic units, weathering surfaces and other weathering phenomena, desert soils, sand dunes and dune sand accumulations, growths of natural vegetation and agriculture, and salt crusts and other expressions of salinization. There are many impressive examples which illustrate the significance of satellite image interpretation on the regional conditions of groundwater which could be traced and interconnected over several tens or even several hundreds of kilometers. This is especially true in the northern Western Desert of Egypt where ground water issuing from deep strata comes to the surface along ENE-WSW and ESE-WNW fault lines and fracture systems. Another striking example is illustrated by the occurrence of fresh to brackish groundwater on the Mediterranean Sea Coastal Zone of the Western Desert where the groundwater is found in the form of lenses floating on the saline sea water.

Status and understanding of groundwater quality in the South Coast Range-Coastal study unit, 2008: California GAMA Priority Basin Project

USGS Publications Warehouse

Burton, Carmen A.; Land, Michael; Belitz, Kenneth

2013-01-01

Groundwater quality in the South Coast Range–Coastal (SCRC) study unit was investigated from May through November 2008 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in the Southern Coast Range hydrologic province and includes parts of Santa Barbara and San Luis Obispo Counties. The GAMA Priority Basin Project is conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board and the Lawrence Livermore National Laboratory. The GAMA Priority Basin Project was designed to provide a statistically unbiased, spatially distributed assessment of untreated groundwater quality within the primary aquifer system. The primary aquifer system is defined as that part of the aquifer corresponding to the perforation interval of wells listed in the California Department of Public Health (CDPH) database for the SCRC study unit. The assessments for the SCRC study unit were based on water-quality and ancillary data collected in 2008 by the USGS from 55 wells on a spatially distributed grid, and water-quality data from the CDPH database. Two types of assessments were made: (1) status, assessment of the current quality of the groundwater resource, and (2) understanding, identification of the natural and human factors affecting groundwater quality. Water-quality and ancillary data were collected from an additional 15 wells for the understanding assessment. The assessments characterize untreated groundwater quality, not the quality of treated drinking water delivered to consumers by water purveyors. The first component of this study, the status assessment of groundwater quality, used data from samples analyzed for anthropogenic constituents such as volatile organic compounds (VOCs) and pesticides, as well as naturally occurring inorganic constituents such as major ions and trace elements. Although the status assessment applies to untreated groundwater, Federal and California regulatory and non-regulatory water-quality benchmarks that apply to drinking water are used to provide context for the results. Relative-concentrations (sample concentration divided by benchmark concentration) were used for evaluating groundwater. A relative-concentration greater than (>) 1.0 indicates a concentration greater than the benchmark and is classified as high. Inorganic constituents are classified as moderate if relative-concentrations are >0.5 and less than or equal to (≤) 1.0, or low if relative-concentrations are ≤0.5. For organic constituents, the boundary between moderate and low relative-concentrations was set at 0.1. Aquifer-scale proportion was used in the status assessment as the primary metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the areal percentage of the primary aquifer system with a high relative-concentration for a particular constituent or class of constituents. Moderate and low aquifer-scale proportions were defined as the areal percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable for the study (within 90 percent confidence intervals). For inorganic constituents with human-health benchmarks, relative-concentrations were high for at least one constituent for 33 percent of the primary aquifer system in the SCRC study unit. Arsenic, molybdenum, and nitrate were the primary inorganic constituents with human-health benchmarks that were detected at high relative-concentrations. Inorganic constituents with aesthetic benchmarks, referred to as secondary maximum contaminant levels (SMCLs), had high relative-concentrations for 35 percent of the primary aquifer system. Iron, manganese, total dissolved solids (TDS), and sulfate were the inorganic constituents with SMCLs detected at high relative-concentrations. In contrast to inorganic constituents, organic constituents with human-health benchmarks were not detected at high relative-concentrations in the primary aquifer system in the SCRC study unit. Of the 205 organic constituents analyzed, 21 were detected—13 with human-health benchmarks. Perchloroethene (PCE) was the only VOC detected at moderate relative-concentrations. PCE, dichlorodifluoromethane (CFC-12), and chloroform were detected in more than 10 percent of the primary aquifer system. Of the two special-interest constituents, one was detected; perchlorate, which has a human-health benchmark, was detected at moderate relative-concentrations in 29 percent of the primary aquifer system and had a detection frequency of 60 percent in the SCRC study unit. The second component of this study, the understanding assessment, identified the natural and human factors that may have affected groundwater quality in the SCRC study unit by evaluating statistical correlations between water-quality constituents and potential explanatory factors. The potential explanatory factors evaluated were land use, septic tank density, well depth and depth to top-of-perforations, groundwater age, density and distance to the nearest formerly leaking underground fuel tank (LUFT), pH, and dissolved oxygen (DO) concentration. Results of the statistical evaluations were used to explain the occurrence and distribution of constituents in the study unit. DO was the primary explanatory factor influencing the concentrations of many inorganic constituents. Arsenic, iron, and manganese concentrations increased as DO concentrations decreased, consistent with patterns expected as a result of reductive dissolution of iron and (or) manganese oxides in aquifer sediments. Molybdenum concentrations increased in anoxic conditions and in oxic conditions with high pH, reflecting two mechanisms for the mobilization of molybdenum—reductive dissolution and pH-dependent desorption under oxic conditions from aquifer sediments. Nitrate concentrations decreased as DO concentrations decreased which would be consistent with degradation of nitrate under anoxic conditions (denitrification). It also is possible that nitrate concentrations decreased in relation to increasing depth and groundwater age and not as a result of denitrification. Groundwater age was another explanatory factor frequently correlated to several inorganic constituents. Iron and manganese concentrations were higher in pre-modern (water recharged before 1952) or mixed-age groundwater. This correlation is one indication that iron and manganese are from natural sources. Nitrate, TDS, and sulfate concentrations were higher in modern groundwater (water recharged since 1952) and may indicate that human activities increase concentrations of nitrate, TDS, and sulfate. Land use was a third explanatory factor frequently correlated with inorganic constituents. Nitrate, TDS, and sulfate concentrations were higher in agricultural land-use areas than in natural land-use areas, indicating that increased concentrations may be a result of agricultural practices. Organic constituents usually were detected at low relative-concentrations; therefore, statistical analyses of relations to explanatory factors usually were done for classes of constituents (for example, pesticides or solvents) as well as for selected constituents. The number of VOCs detected in a well was not correlated to any of the explanatory factors evaluated. The number of pesticide and solvent detections and PCE and CFC-12 concentrations were higher in modern groundwater than in pre-modern groundwater. PCE and CFC-12 also were positively correlated to the density of LUFTs. PCE was negatively correlated to natural land use. Chloroform concentrations were positively correlated to the density of septic systems. Perchlorate concentrations were greater in agricultural areas than in urban or natural areas. Correlation of perchlorate with DO may indicate that perchlorate biodegradation under anoxic conditions may occur. Anthropogenic sources have contributed perchlorate to groundwater in the SCRC study unit, although low levels of perchlorate may occur naturally.

Remedial investigation work plan for Bear Creek Valley Operable Unit 4 (shallow groundwater in Bear Creek Valley) at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-07-01

To effectively evaluate the cumulative impact of releases from multiple sources of contamination, a structured approach has been adopted for Oak Ridge Reservation (ORR) based on studies of the groundwater and surface water separate from studies of the sources. Based on the realization of the complexity of the hydrogeologic regime of the ORR, together with the fact that there are numerous sources contributing to groundwater contamination within a geographical area, it was agreed that more timely investigations, at perhaps less cost, could be achieved by separating the sources of contamination from the groundwater and surface water for investigation and remediation.more » The result will be more immediate attention [Records of Decision (RODs) for interim measures or removal actions] for the source Operable Units (OUs) while longer-term remediation investigations continue for the hydrogeologic regimes, which are labeled as integrator OUs. This remedial investigation work plan contains summaries of geographical, historical, operational, geological, and hydrological information specific to the unit. Taking advantage of the historical data base and ongoing monitoring activities and applying the observational approach to focus data gathering activities will allow the feasibility study to evaluate all probable or likely alternatives.« less

Remedial Investigation work plan for Bear Creek Valley Operable Unit 4 (shallow groundwater in Bear Creek Valley) at the Oak Ridge Y-12 Plant, Oak Ridge, Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-09-01

To effectively evaluate the cumulative impact of releases from multiple sources of contamination, a structured approach has been adopted for Oak Ridge Reservation (ORR) based on studies of the groundwater and surface water separate from studies of the sources. Based on the realization of the complexity of the hydrogeologic regime of the ORR, together with the fact that there are numerous sources contributing to groundwater contamination within a geographical area, it was agreed that more timely investigations, at perhaps less cost, could be achieved by separating the sources of contamination from the groundwater and surface water for investigation and remediation.more » The result will be more immediate attention [Records of Decision (RODS) for interim measures or removal actions] for the source Operable Units (OUs) while longer-term remediation investigations continue for the hydrogeologic regime`s, which are labeled as integrator OUs. This Remedial Investigation work plan contains summaries of geographical, historical, operational, geological, and hydrological information specific to the unit. Taking advantage of the historical data base and ongoing monitoring activities and applying the observational approach to focus data gathering activities will allow the Feasibility Study to evaluate all probable or likely alternatives.« less

40 CFR 264.92 - Ground-water protection standard.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 26 2011-07-01 2011-07-01 false Ground-water protection standard. 264... Releases From Solid Waste Management Units § 264.92 Ground-water protection standard. The owner or operator... constituents under § 264.93 detected in the ground water from a regulated unit do not exceed the concentration...

40 CFR 264.92 - Ground-water protection standard.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 25 2010-07-01 2010-07-01 false Ground-water protection standard. 264... Releases From Solid Waste Management Units § 264.92 Ground-water protection standard. The owner or operator... constituents under § 264.93 detected in the ground water from a regulated unit do not exceed the concentration...

40 CFR 264.92 - Ground-water protection standard.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 26 2014-07-01 2014-07-01 false Ground-water protection standard. 264... Releases From Solid Waste Management Units § 264.92 Ground-water protection standard. The owner or operator... constituents under § 264.93 detected in the ground water from a regulated unit do not exceed the concentration...

40 CFR 264.92 - Ground-water protection standard.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 27 2012-07-01 2012-07-01 false Ground-water protection standard. 264... Releases From Solid Waste Management Units § 264.92 Ground-water protection standard. The owner or operator... constituents under § 264.93 detected in the ground water from a regulated unit do not exceed the concentration...

40 CFR 264.92 - Ground-water protection standard.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 27 2013-07-01 2013-07-01 false Ground-water protection standard. 264... Releases From Solid Waste Management Units § 264.92 Ground-water protection standard. The owner or operator... constituents under § 264.93 detected in the ground water from a regulated unit do not exceed the concentration...

Effects of natural and human factors on groundwater quality of basin-fill aquifers in the southwestern United States-conceptual models for selected contaminants

USGS Publications Warehouse

Bexfield, Laura M.; Thiros, Susan A.; Anning, David W.; Huntington, Jena M.; McKinney, Tim S.

2011-01-01

As part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program, the Southwest Principal Aquifers (SWPA) study is building a better understanding of the factors that affect water quality in basin-fill aquifers in the Southwestern United States. The SWPA study area includes four principal aquifers of the United States: the Basin and Range basin-fill aquifers in California, Nevada, Utah, and Arizona; the Rio Grande aquifer system in New Mexico and Colorado; and the California Coastal Basin and Central Valley aquifer systems in California. Similarities in the hydrogeology, land- and water-use practices, and water-quality issues for alluvial basins within the study area allow for regional analysis through synthesis of the baseline knowledge of groundwater-quality conditions in basins previously studied by the NAWQA Program. Resulting improvements in the understanding of the sources, movement, and fate of contaminants are assisting in the development of tools used to assess aquifer susceptibility and vulnerability.This report synthesizes previously published information about the groundwater systems and water quality of 15 information-rich basin-fill aquifers (SWPA case-study basins) into conceptual models of the primary natural and human factors commonly affecting groundwater quality with respect to selected contaminants, thereby helping to build a regional understanding of the susceptibility and vulnerability of basin-fill aquifers to those contaminants. Four relatively common contaminants (dissolved solids, nitrate, arsenic, and uranium) and two contaminant classes (volatile organic compounds (VOCs) and pesticide compounds) were investigated for sources and controls affecting their occurrence and distribution above specified levels of concern in groundwater of the case-study basins. Conceptual models of factors that are important to aquifer vulnerability with respect to those contaminants and contaminant classes were subsequently formed. The conceptual models are intended in part to provide a foundation for subsequent development of regional-scale statistical models that relate specific constituent concentrations or occurrence in groundwater to natural and human factors.

Ground-water flow in the shallow aquifer system at the Naval Weapons Station Yorktown, Virginia

USGS Publications Warehouse

Smith, Barry S.

2001-01-01

The Environmental Directorate of the Naval Weapons Station Yorktown, Virginia, is concerned about possible contamination of ground water at the Station. Ground water at the Station flows through a shallow system of layered aquifers and leaky confining units. The units of the shallow aquifer system are the Columbia aquifer, the Cornwallis Cave confining unit, the Cornwallis Cave aquifer, the Yorktown confining unit, and the Yorktown-Eastover aquifer. The Eastover-Calvert confining unit separates the shallow aquifer system from deeper confined aquifers beneath the Station. A three-dimensional, finite-difference, ground-water flow model was used to simulate steady-state ground-water flow of the shallow aquifer system in and around the Station. The model simulated ground-water flow from the peninsular drainage divide that runs across the Lackey Plain near the southern end of the Station north to King Creek and the York River and south to Skiffes Creek and the James River. The model was calibrated by minimizing the root mean square error between 4 7 measured and corresponding simulated water levels. The calibrated model was used to determine the ground-water budget and general directions of ground-water flow. A particle-tracking routine was used with the calibrated model to estimate groundwater flow paths, flow rates, and traveltimes from selected sites at the Station. Simulated ground-water flow velocities of the Station-area model were small beneath the interstream areas of the Lackey Plain and Croaker Flat, but increased outward toward the streams and rivers where the hydraulic gradients are larger. If contaminants from the land surface entered the water table at or near the interstream areas of the Station, where hydraulic gradients are smaller, they would migrate more slowly than if they entered closer to the streams or the shores of the rivers where gradients commonly are larger. The ground-water flow simulations indicate that some ground water leaks downward from the water table to the Yorktown confining unit and, where the confining unit is absent, to the Yorktown-Eastover aquifer. The velocities of advective-driven contaminants would decrease considerably when entering the Yorktown confining unit because the hydraulic conductivity of the confining unit is small compared to that of the aquifers. Any contaminants that moved with advective ground-water flow near the groundwater divide of the Lackey Plain would move relatively slowly because the hydraulic gradients are small there. The direction in which the contaminants would move, however, would be determined by precisely where the contaminants entered the water table. The model was not designed to accurately simulate ground-water flow paths through local karst features. Beneath Croaker Flat, ground water flows downward through the Columbia aquifer and the Yorktown confining unit into the Yorktown-Eastover aquifer. Analyses of the movement of simulated particles from two adjacent sites at Croaker Flat indicated that ground-water flow paths were similar at first but diverged and discharged to different tributaries of Indian Field Creek or to the York River. These simulations indicate that complex and possibly divergent flow paths and traveltimes are possible at the Station. Although the Station-area model is not detailed enough to simulate ground-water flow at the scales commonly used to track and remediate contaminants at specific sites, general concepts about possible contaminant migration at the Station can be inferred from the simulations.

Superfund record of decision (EPA Region 7): Cornhusker Army Ammunition Plant, Operable Unit 1, Hall County, Grand Island, NE, September 29, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1995-04-01

The decision document presents the selected interim remedial action for the groundwater operable unit at the Cornhusker Army Ammunition Plant (CAAP). Operable Unit One encompasses the explosives groundwater plume(s), both on-post and off-post. Explosives of concern in the contaminant plume include RDX, TNT, HMX, and their decomposition products. The objective of the interim action is to contain the plume and prevent further migration of contaminants, and does not encompass full restoration of the plume of contaminated groundwater. The recommended alternatives provide an approach to containing and removing contaminant mass from the groundwater plume. This approach will control further migration ofmore » the plume and reduce the levels of the contamination in groundwater.« less

Groundwater quality in the shallow aquifers of the Monterey Bay, Salinas Valley, and adjacent highland areas, Southern Coast Ranges, California

USGS Publications Warehouse

Burton, Carmen

2018-05-30

The Monterey-Salinas Shallow Aquifer study unit covers approximately 7,820 square kilometers (km2) in Santa Cruz, Monterey, and San Luis Obispo Counties in the Central Coast Hydrologic Region of California. The study unit was divided into four study areas—Santa Cruz, Pajaro Valley, Salinas Valley, and Highlands. More than 75 percent of the water used for drinking-water supply in the Central Coast Hydrologic Region of California is groundwater, and there are more than 8,000 well driller’s logs for domestic wells (California Department of Water Resources, 2013).

Groundwater Quality in the Shallow Aquifers of the Monterey Bay, Salinas Valley, and Adjacent Highland Areas, Southern Coast Ranges, California

USGS Publications Warehouse

Burton, Carmen

2018-05-30

The Monterey-Salinas Shallow Aquifer study unit covers approximately 7,820 square kilometers (km2) in Santa Cruz, Monterey, and San Luis Obispo Counties in the Central Coast Hydrologic Region of California. The study unit was divided into four study areas—Santa Cruz, Pajaro Valley, Salinas Valley, and Highlands. More than 75 percent of the water used for drinking-water supply in the Central Coast Hydrologic Region of California is groundwater, and there are more than 8,000 well driller’s logs for domestic wells (California Department of Water Resources, 2013).

Geophysical Tools for an Improved Hydrogeologic Conceptual Model of the Big Chino Sub-basin, Central Arizona

NASA Astrophysics Data System (ADS)

Macy, J. P.; Kennedy, J.

2017-12-01

Water users and managers who rely on the Verde River system and its aquifers for water supplies have an intrinsic interest in developing the best possible tools for assessing the effects of groundwater withdrawals. Past, present, and future groundwater withdrawals from the Big Chino sub-basin will affect groundwater levels in the Big Chino area and groundwater discharge at the headwaters of the Verde River, specifically at the Upper Verde Springs, which is believed to be a major discharge zone of groundwater from the sub-basin. The amount and timing of reduced discharge as base flow is a function of connections between hydrogeologic (aquifer) units, aquifer storage properties and transmissivity, and proximity of withdrawal locations to discharge areas. To better define the aquifer units and aquifer storage properties, the United States Geological Survey, Cities of Prescott and Prescott Valley, and Salt River Project have initiated an ongoing geophysical study using controlled-source audio-frequency magnetotellurics (CSAMT) and repeat microgravity methods. CSAMT, a high-energy electromagnetic method sensitive to lithologic variations between rock and sediment types, is useful for defining aquifers at depths of up to 600 meters. Visual display of CSAMT profiles using Google Earth is useful for understanding and visualizing the relation between geophysics and Big Chino Sub-basin hydrogeology. Initial results from repeat microgravity surveys, which measure changes in subsurface mass (and therefore aquifer storage) over time, reveal spatial variation in the relation between aquifer storage changes and groundwater level changes. This variation reflects different confining conditions and multiple aquifer systems in different parts of the aquifer. Information about confining conditions and multiple aquifers could improve numerical groundwater models and predictions of future groundwater-level and base-flow depletion.

Effects of daily precipitation and evapotranspiration patterns on flow and VOC transport to groundwater along a watershed flow path

USGS Publications Warehouse

Johnson, Richard L.; Thoms, R.B.; Zogorski, J.S.

2003-01-01

MTBE and other volatile organic compounds (VOCs) are widely observed in shallow groundwater in the United States, especially in urban areas. Previous studies suggest that the atmosphere and/or nonpoint surficial sources could be responsible for some of those VOCs, especially in areas where there is net recharge to groundwater. However, in semi-arid locations where annual potential evapotranspiration can exceed annual precipitation, VOC detections in groundwater can be frequent. VOC transport to groundwater under net discharge conditions has not previously been examined. A numerical model is used here to demonstrate that daily precipitation and evapotranspiration (ET) patterns can have a significant effect on recharge to groundwater, water table elevations, and VOC transport. Ten-year precipitation/ET scenarios from six sites in the United States are examined using both actual daily observed values and “average” pulsed precipitation. MTBE and tetrachloroethylene transport, including gas-phase diffusion, are considered. The effects of the precipitation/ET scenarios on net recharge and groundwater flow are significant and complicated, especially under low-precipitation conditions when pulsed precipitation can significantly underestimate transport to groundwater. In addition to precipitation and evapotranspiration effects, location of VOC entry into the subsurface within the watershed is important for transport in groundwater. This is caused by groundwater hydraulics at the watershed scale as well as variations in ET within the watershed. The model results indicate that it is important to consider both daily precipitation/ET patterns and location within the watershed in order to interpret VOC occurrence in groundwater, especially in low-precipitation settings.

The hydrogeology of complex lens conditions in Qatar

NASA Astrophysics Data System (ADS)

Lloyd, J. W.; Pike, J. G.; Eccleston, B. L.; Chidley, T. R. E.

1987-01-01

The emirate of Qatar lies on a peninsula extending northward from the mainland of Saudi Arabia into the Arabian Gulf. The peninsula is underlain by sedimentary rocks ranging from late Cretaceous to Holocene age but only two Lower Tertiary units are identified as aquifers. The groundwater distribution in these units is seen to be controlled by facies distributions related to tectonically controlled sedimentation and subsequent dissolution. Dissolution has created permeability, in the Umm er Rhaduma limestones and in the overlying Rus anhydrites. In the latter case the dissolution has lead to extensive surface collapse which has provided a mechanism for recharge from runoff. Despite very low rainfall and high evaporation rates, recharge related to storm runoff has resulted in the establishment of a complex fresh groundwater lens in both aquifer units. The lens is constrained by saline groundwaters which in the lower unit are controlled by heads in eastern Saudi Arabia but in the upper unit by the Arabian Gulf sea level. Groundwater abstraction is shown to be distorting the fresh groundwater lens configuration, and estimates of the resultant flow responses affecting the lens are given.

Geo-electrical investigation of near surface conductive structures suitable for groundwater accumulation in a resistive crystalline basement environment: A case study of Isuada, southwestern Nigeria

NASA Astrophysics Data System (ADS)

Kayode, J. S.; Adelusi, A. O.; Nawawi, M. N. M.; Bawallah, M.; Olowolafe, T. S.

2016-07-01

This paper presents a geophysical surveying for groundwater identification in a resistive crystalline basement hard rock in Isuada area, Southwestern Nigeria. Very low frequency (VLF) electromagnetic and electrical resistivity geophysical techniques combined with well log were used to characterize the concealed near surface conductive structures suitable for groundwater accumulation. Prior to this work; little was known about the groundwater potential of this area. Qualitative and semi-quantitative interpretations of the data collected along eight traverses at 20 m spacing discovered conductive zones suspected to be fractures, faults, and cracks which were further mapped using Vertical Electrical Sounding (VES) technique. Forty VES stations were utilized using Schlumberger configurations with AB/2 varying from 1 to 100 m. Four layers i.e. the top soil, the weathered layer, the partially weathered/fractured basement and the fresh basement were delineated from the interpreted resistivity curves. The weathered layers constitute the major aquifer unit in the area and are characterized by moderately low resistivity values which ranged between about 52 Ωm and 270 Ωm while the thickness varied from 1 to 35 m. The depth to the basement and the permeable nature of the weathered layer obtained from both the borehole and the hand-dug wells was used to categorize the groundwater potential of the study area into high, medium and low ratings. The groundwater potential map revealed that about 45% of the study area falls within the low groundwater potential rating while about 10% constitutes the medium groundwater potential and the remaining 45% constitutes high groundwater potential. The low resistivity, thick overburden, and fractured bedrock constitute the aquifer units and the series of basement depressions identified from the geoelectric sections as potential conductive zones appropriate for groundwater development.

Water resources of the Swinomish Indian Reservation, Washington

USGS Publications Warehouse

Drost, B.W.

1979-01-01

Average total inflow to and outflow from the hydrologic system of the Swinomish Indian Reservation, Wash., is 24 cfs (cubic feet per second). Recharge to the ground-water reservoir is 8 cfs. The study area is underlain by three types of unconsolidated deposits: the uppermost unit is till, the intermediate unit is sand and gravel, and the lowermost unit is clay and silt. During 1975 the average rate of water use was 0.19 cfs. About 70 percent was pumped from the ground-water reservoir and the rest was imported. Dissolved-solids concentrations are 10-20 mg/L (milligrams per liter). In the zone of saltwater, differsion concentrations up to 1,570 mg/L were measured. Human interaction with the hydrologic system has had little effect on water quality. Ground-water quality is generally well within acceptable limits for most uses. If 20 percent of ground-water can be intercepted then a net rate of withdrawal of 1.6 cfs can be attained. Aquiculture development is possible on the two largest streams in the reservation in the form of incubation stations handling 600,000 eggs each. (Woodard-USGS)

Long-term groundwater depletion in the United States

USGS Publications Warehouse

Konikow, Leonard F.

2015-01-01

The volume of groundwater stored in the subsurface in the United States decreased by almost 1000 km3 during 1900–2008. The aquifer systems with the three largest volumes of storage depletion include the High Plains aquifer, the Mississippi Embayment section of the Gulf Coastal Plain aquifer system, and the Central Valley of California. Depletion rates accelerated during 1945–1960, averaging 13.6 km3/year during the last half of the century, and after 2000 increased again to about 24 km3/year. Depletion intensity is a new parameter, introduced here, to provide a more consistent basis for comparing storage depletion problems among various aquifers by factoring in time and areal extent of the aquifer. During 2001–2008, the Central Valley of California had the largest depletion intensity. Groundwater depletion in the United States can explain 1.4% of observed sea-level rise during the 108-year study period and 2.1% during 2001–2008. Groundwater depletion must be confronted on local and regional scales to help reduce demand (primarily in irrigated agriculture) and/or increase supply.

A MANUAL OF INSTRUCTIONAL PROBLEMS FOR THE U.S.G.S. MODFLOW MODEL

EPA Science Inventory

A recent report by the United States Environmental Protection Agency Groundwater Modeling Policy Study Group (van der Heijde and Park, 1986) offered several approaches to training Agency staff in the application of groundwater modeling. They identified the problem that current t...

Groundwater-quality data in the Western San Joaquin Valley study unit, 2010 - Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Landon, Matthew K.; Shelton, Jennifer L.; Belitz, Kenneth

2013-01-01

Groundwater quality in the approximately 2,170-square-mile Western San Joaquin Valley (WSJV) study unit was investigated by the U.S. Geological Survey (USGS) from March to July 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program's Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The WSJV study unit was the twenty-ninth study unit to be sampled as part of the GAMA-PBP. The GAMA Western San Joaquin Valley study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system, and to facilitate statistically consistent comparisons of untreated groundwater quality throughout California. The primary aquifer system is defined as parts of aquifers corresponding to the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the WSJV study unit. Groundwater quality in the primary aquifer system may differ from the quality in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. In the WSJV study unit, groundwater samples were collected from 58 wells in 2 study areas (Delta-Mendota subbasin and Westside subbasin) in Stanislaus, Merced, Madera, Fresno, and Kings Counties. Thirty-nine of the wells were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells), and 19 wells were selected to aid in the understanding of aquifer-system flow and related groundwater-quality issues (understanding wells). The groundwater samples were analyzed for organic constituents (volatile organic compounds [VOCs], low-level fumigants, and pesticides and pesticide degradates), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), and naturally occurring inorganic constituents (trace elements, nutrients, dissolved organic carbon [DOC], major and minor ions, silica, total dissolved solids [TDS], alkalinity, total arsenic and iron [unfiltered] and arsenic, chromium, and iron species [filtered]). Isotopic tracers (stable isotopes of hydrogen, oxygen, and boron in water, stable isotopes of nitrogen and oxygen in dissolved nitrate, stable isotopes of sulfur in dissolved sulfate, isotopic ratios of strontium in water, stable isotopes of carbon in dissolved inorganic carbon, activities of tritium, and carbon-14 abundance), dissolved standard gases (methane, carbon dioxide, nitrogen, oxygen, and argon), and dissolved noble gases (argon, helium-4, krypton, neon, and xenon) were measured to help identify sources and ages of sampled groundwater. In total, 245 constituents and 8 water-quality indicators were measured. Quality-control samples (blanks, replicates, or matrix spikes) were collected at 16 percent of the wells in the WSJV study unit, and the results for these samples were used to evaluate the quality of the data from the groundwater samples. Blanks rarely contained detectable concentrations of any constituent, suggesting that contamination from sample collection procedures was not a significant source of bias in the data for the groundwater samples. Replicate samples all were within acceptable limits of variability. Matrix-spike recoveries were within the acceptable range (70 to 130 percent) for approximately 87 percent of the compounds. This study did not evaluate the quality of water delivered to consumers. After withdrawal, groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is delivered to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-regulatory benchmarks established for aesthetic concerns by CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. Most inorganic constituents detected in groundwater samples from the 39 grid wells were detected at concentrations less than health-based benchmarks. Detections of organic and special-interest constituents from grid wells sampled in the WSJV study unit also were less than health-based benchmarks. In total, VOCs were detected in 12 of the 39 grid wells sampled (approximately 31 percent), pesticides and pesticide degradates were detected in 9 grid wells (approximately 23 percent), and perchlorate was detected in 15 grid wells (approximately 38 percent). Trace elements, major and minor ions, and nutrients were sampled for at 39 grid wells; most concentrations were less than health-based benchmarks. Exceptions include two detections of arsenic greater than the USEPA maximum contaminant level (MCL-US) of 10 micrograms per liter (μg/L), 20 detections of boron greater than the CDPH notification level (NL-CA) of 1,000 μg/L, 2 detections of molybdenum greater than the USEPA lifetime health advisory level (HAL-US) of 40 μg/L, 1 detection of selenium greater than the MCL-US of 50 μg/L, 2 detections of strontium greater than the HAL-US of 4,000 μg/L, and 3 detections of nitrate greater than the MCL-US of 10 μg/L. Results for inorganic constituents with non-health-based benchmarks (iron, manganese, chloride, sulfate, and TDS) showed that iron concentrations greater than the CDPH secondary maximum contaminant level (SMCL-CA) of 300 μg/L were detected in five grid wells. Manganese concentrations greater than the SMCL-CA of 50 μg/L were detected in 16 grid wells. Chloride concentrations greater than the recommended SMCL-CA benchmark of 250 milligrams per liter (mg/L) were detected in 14 grid wells, and concentrations in 5 of these wells also were greater than the upper SMCL-CA benchmark of 500 mg/L. Sulfate concentrations greater than the recommended SMCL-CA benchmark of 250 mg/L were measured in 21 grid wells, and concentrations in 13 of these wells also were greater than the SMCL-CA upper benchmark of 500 mg/L. TDS concentrations greater than the SMCL-CA recommended benchmark of 500 mg/L were measured in 36 grid wells, and concentrations in 20 of these wells also were greater than the SMCL-CA upper benchmark of 1,000 mg/L.

Groundwater-quality data in the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit, 2008-2010--Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Wright, Michael T.; Beuttel, Brandon S.; Belitz, Kenneth

2012-01-01

Groundwater quality in the 12,103-square-mile Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts (CLUB) study unit was investigated by the U.S. Geological Survey (USGS) from December 2008 to March 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program's Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The CLUB study unit was the twenty-eighth study unit to be sampled as part of the GAMA-PBP. The GAMA CLUB study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer systems, and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer systems (hereinafter referred to as primary aquifers) are defined as parts of aquifers corresponding to the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the CLUB study unit. The quality of groundwater in shallow or deep water-bearing zones may differ from the quality of groundwater in the primary aquifers; shallow groundwater may be more vulnerable to surficial contamination. In the CLUB study unit, groundwater samples were collected from 52 wells in 3 study areas (Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts) in San Bernardino, Riverside, Kern, San Diego, and Imperial Counties. Forty-nine of the wells were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells), and three wells were selected to aid in evaluation of water-quality issues (understanding wells). The groundwater samples were analyzed for organic constituents (volatile organic compounds [VOCs], pesticides and pesticide degradates, and pharmaceutical compounds), constituents of special interest (perchlorate and N-nitrosodimethylamine [NDMA]), naturally-occurring inorganic constituents (trace elements, nutrients, major and minor ions, silica, total dissolved solids [TDS], alkalinity, and species of inorganic chromium), and radioactive constituents (radon-222, radium isotopes, and gross alpha and gross beta radioactivity). Naturally-occurring isotopes (stable isotopes of hydrogen, oxygen, boron, and strontium in water, stable isotopes of carbon in dissolved inorganic carbon, activities of tritium, and carbon-14 abundance) and dissolved noble gases also were measured to help identify the sources and ages of sampled groundwater. In total, 223 constituents and 12 water-quality indicators were investigated. Three types of quality-control samples (blanks, replicates, and matrix spikes) were collected at up to 10 percent of the wells in the CLUB study unit, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination from sample collection procedures was not a significant source of bias in the data for the groundwater samples. Replicate samples generally were within the limits of acceptable analytical reproducibility. Median matrix-spike recoveries were within the acceptable range (70 to 130 percent) for approximately 85 percent of the compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, untreated groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is delivered to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-regulatory benchmarks established for aesthetic concerns by CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. Most inorganic constituents detected in groundwater samples from the 49 grid wells were detected at concentrations less than drinking-water benchmarks. In addition, all detections of organic constituents from the CLUB study-unit grid-well samples were less than health-based benchmarks. In total, VOCs were detected in 17 of the 49 grid wells sampled (approximately 35 percent), pesticides and pesticide degradates were detected in 5 of the 47 grid wells sampled (approximately 11 percent), and perchlorate was detected in 41 of 49 grid wells sampled (approximately 84 percent). Trace elements, major and minor ions, and nutrients were sampled for at 39 grid wells, and radioactive constituents were sampled for at 23 grid wells; most detected concentrations were less than health-based benchmarks. Exceptions in the grid-well samples include seven detections of arsenic greater than the USEPA maximum contaminant level (MCL-US) of 10 micrograms per liter (μg/L); four detections of boron greater than the CDPH notification level (NL-CA) of 1,000 μg/L; six detections of molybdenum greater than the USEPA lifetime health advisory level (HAL-US) of 40 μg/L; two detections of uranium greater than the MCL-US of 30 μg/L; nine detections of fluoride greater than the CDPH maximum contaminant level (MCL-CA) of 2 milligrams per liter (mg/L); one detection of nitrite plus nitrate (NO2-+NO3-), as nitrogen, greater than the MCL-US of 10 mg/L; and four detections of gross alpha radioactivity (72-hour count), and one detection of gross alpha radioactivity (30-day count), greater than the MCL-US of 15 picocuries per liter. Results for constituents with non-regulatory benchmarks set for aesthetic concerns showed that a manganese concentration greater than the CDPH secondary maximum contaminant level (SMCL-CA) of 50 μg/L was detected in one grid well. Chloride concentrations greater than the recommended SMCL-CA benchmark of 250 mg/L were detected in three grid wells, and one of these wells also had a concentration that was greater than the upper SMCL-CA benchmark of 500 mg/L. Sulfate concentrations greater than the recommended SMCL-CA benchmark of 250 mg/L were measured in six grid wells. TDS concentrations greater than the SMCL-CA recommended benchmark of 500 mg/L were measured in 20 grid wells, and concentrations in 2 of these wells also were greater than the SMCL-CA upper benchmark of 1,000 mg/L.

Groundwater-quality data in seven GAMA study units: results from initial sampling, 2004-2005, and resampling, 2007-2008, of wells: California GAMA Program Priority Basin Project

USGS Publications Warehouse

Kent, Robert; Belitz, Kenneth; Fram, Miranda S.

2014-01-01

The Priority Basin Project (PBP) of the Groundwater Ambient Monitoring and Assessment (GAMA) Program was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The GAMA-PBP began sampling, primarily public supply wells in May 2004. By the end of February 2006, seven (of what would eventually be 35) study units had been sampled over a wide area of the State. Selected wells in these first seven study units were resampled for water quality from August 2007 to November 2008 as part of an assessment of temporal trends in water quality by the GAMA-PBP. The initial sampling was designed to provide a spatially unbiased assessment of the quality of raw groundwater used for public water supplies within the seven study units. In the 7 study units, 462 wells were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the study area. Wells selected this way are referred to as grid wells or status wells. Approximately 3 years after the initial sampling, 55 of these previously sampled status wells (approximately 10 percent in each study unit) were randomly selected for resampling. The seven resampled study units, the total number of status wells sampled for each study unit, and the number of these wells resampled for trends are as follows, in chronological order of sampling: San Diego Drainages (53 status wells, 7 trend wells), North San Francisco Bay (84, 10), Northern San Joaquin Basin (51, 5), Southern Sacramento Valley (67, 7), San Fernando–San Gabriel (35, 6), Monterey Bay and Salinas Valley Basins (91, 11), and Southeast San Joaquin Valley (83, 9). The groundwater samples were analyzed for a large number of synthetic organic constituents (volatile organic compounds [VOCs], pesticides, and pesticide degradates), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), and naturally-occurring inorganic constituents (nutrients, major and minor ions, and trace elements). Naturally-occurring isotopes (tritium, carbon-14, and stable isotopes of hydrogen and oxygen in water) also were measured to help identify processes affecting groundwater quality and the sources and ages of the sampled groundwater. Nearly 300 constituents and water-quality indicators were investigated. Quality-control samples (blanks, replicates, and samples for matrix spikes) were collected at 24 percent of the 55 status wells resampled for trends, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a noticeable source of bias in the data for the groundwater samples. Differences between replicate samples were mostly within acceptable ranges, indicating acceptably low variability in analytical results. Matrix-spike recoveries were within the acceptable range (70 to 130 percent) for 75 percent of the compounds for which matrix spikes were collected. This study did not attempt to evaluate the quality of water delivered to consumers. After withdrawal, groundwater typically is treated, disinfected, and blended with other waters to maintain acceptable water quality. The benchmarks used in this report apply to treated water that is served to the consumer, not to untreated groundwater. To provide some context for the results, however, concentrations of constituents measured in these groundwater samples were compared with benchmarks established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH). Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. Most constituents that were detected in groundwater samples from the trend wells were found at concentrations less than drinking-water benchmarks. Four VOCs—trichloroethene, tetrachloroethene, 1,2-dibromo-3-chloropropane, and methyl tert-butyl ether—were detected in one or more wells at concentrations greater than their health-based benchmarks, and six VOCs were detected in at least 10 percent of the samples during initial sampling or resampling of the trend wells. No pesticides were detected at concentrations near or greater than their health-based benchmarks. Three pesticide constituents—atrazine, deethylatrazine, and simazine—were detected in more than 10 percent of the trend-well samples during both sampling periods. Perchlorate, a constituent of special interest, was detected more frequently, and at greater concentrations during resampling than during initial sampling, but this may be due to a change in analytical method between the sampling periods, rather than to a change in groundwater quality. Another constituent of special interest, 1,2,3-TCP, was also detected more frequently during resampling than during initial sampling, but this pattern also may not reflect a change in groundwater quality. Samples from several of the wells where 1,2,3-TCP was detected by low-concentration-level analysis during resampling were not analyzed for 1,2,3-TCP using a low-level method during initial sampling. Most detections of nutrients and trace elements in samples from trend wells were less than health-based benchmarks during both sampling periods. Exceptions include nitrate, arsenic, boron, and vanadium, all detected at concentrations greater than their health-based benchmarks in at least one well during both sampling periods, and molybdenum, detected at concentrations greater than its health-based benchmark during resampling only. The isotopic ratios of oxygen and hydrogen in water and tritium and carbon-14 activities generally changed little between sampling periods, suggesting that the predominant sources and ages of groundwater in most trend wells were consistent between the sampling periods.

Fluor Hanford, Inc. Groundwater and Technical Integration Support (Master Project) Quality Assurance Management Plan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fix, N. J.

The scope of the Fluor Hanford, Inc. Groundwater and Technical Integration Support (Master Project) is to provide technical and integration support to Fluor Hanford, Inc., including operable unit investigations at 300-FF-5 and other groundwater operable units, strategic integration, technical integration and assessments, remediation decision support, and science and technology. This Quality Assurance Management Plan provides the quality assurance requirements and processes that will be followed by the Fluor Hanford, Inc. Groundwater and Technical Integration Support (Master Project).

Predicting geogenic arsenic contamination in shallow groundwater of south Louisiana, United States.

PubMed

Yang, Ningfang; Winkel, Lenny H E; Johannesson, Karen H

2014-05-20

Groundwater contaminated with arsenic (As) threatens the health of more than 140 million people worldwide. Previous studies indicate that geology and sedimentary depositional environments are important factors controlling groundwater As contamination. The Mississippi River delta has broadly similar geology and sedimentary depositional environments to the large deltas in South and Southeast Asia, which are severely affected by geogenic As contamination and therefore may also be vulnerable to groundwater As contamination. In this study, logistic regression is used to develop a probability model based on surface hydrology, soil properties, geology, and sedimentary depositional environments. The model is calibrated using 3286 aggregated and binary-coded groundwater As concentration measurements from Bangladesh and verified using 78 As measurements from south Louisiana. The model's predictions are in good agreement with the known spatial distribution of groundwater As contamination of Bangladesh, and the predictions also indicate high risk of As contamination in shallow groundwater from Holocene sediments of south Louisiana. Furthermore, the model correctly predicted 79% of the existing shallow groundwater As measurements in the study region, indicating good performance of the model in predicting groundwater As contamination in shallow aquifers of south Louisiana.

Changes in projected spatial and seasonal groundwater recharge in the upper Colorado River Basin

USGS Publications Warehouse

Tillman, Fred; Gangopadhyay, Subhrendu; Pruitt, Tom

2017-01-01

The Colorado River is an important source of water in the western United States, supplying the needs of more than 38 million people in the United States and Mexico. Groundwater discharge to streams has been shown to be a critical component of streamflow in the Upper Colorado River Basin (UCRB), particularly during low-flow periods. Understanding impacts on groundwater in the basin from projected climate change will assist water managers in the region in planning for potential changes in the river and groundwater system. A previous study on changes in basin-wide groundwater recharge in the UCRB under projected climate change found substantial increases in temperature, moderate increases in precipitation, and mostly periods of stable or slight increases in simulated groundwater recharge through 2099. This study quantifies projected spatial and seasonal changes in groundwater recharge within the UCRB from recent historical (1950 to 2015) through future (2016 to 2099) time periods, using a distributed-parameter groundwater recharge model with downscaled climate data from 97 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections. Simulation results indicate that projected increases in basin-wide recharge of up to 15% are not distributed uniformly within the basin or throughout the year. Northernmost subregions within the UCRB are projected an increase in groundwater recharge, while recharge in other mainly southern subregions will decline. Seasonal changes in recharge also are projected within the UCRB, with decreases of 50% or more in summer months and increases of 50% or more in winter months for all subregions, and increases of 10% or more in spring months for many subregions.

Changes in Projected Spatial and Seasonal Groundwater Recharge in the Upper Colorado River Basin.

PubMed

Tillman, Fred D; Gangopadhyay, Subhrendu; Pruitt, Tom

2017-07-01

The Colorado River is an important source of water in the western United States, supplying the needs of more than 38 million people in the United States and Mexico. Groundwater discharge to streams has been shown to be a critical component of streamflow in the Upper Colorado River Basin (UCRB), particularly during low-flow periods. Understanding impacts on groundwater in the basin from projected climate change will assist water managers in the region in planning for potential changes in the river and groundwater system. A previous study on changes in basin-wide groundwater recharge in the UCRB under projected climate change found substantial increases in temperature, moderate increases in precipitation, and mostly periods of stable or slight increases in simulated groundwater recharge through 2099. This study quantifies projected spatial and seasonal changes in groundwater recharge within the UCRB from recent historical (1950 to 2015) through future (2016 to 2099) time periods, using a distributed-parameter groundwater recharge model with downscaled climate data from 97 Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections. Simulation results indicate that projected increases in basin-wide recharge of up to 15% are not distributed uniformly within the basin or throughout the year. Northernmost subregions within the UCRB are projected an increase in groundwater recharge, while recharge in other mainly southern subregions will decline. Seasonal changes in recharge also are projected within the UCRB, with decreases of 50% or more in summer months and increases of 50% or more in winter months for all subregions, and increases of 10% or more in spring months for many subregions. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Basewide Groundwater Operable Unit. Groundwater Operable Unit Remedial Investigation/Feasibility Study Report. Volume 2

DTIC Science & Technology

1994-06-01

Boron -- - .- Cadmium (3.9) (1.1) 1.4a,c 0 .55a.b Chromium , Hexavalent (16) lid _______ Chromium , Trivalent 1,700 21016li Cobalt -- -- .- Copper (18...same time period as those for VOCs should be used, if possible. Response: Four figures have been prepared showing the lead, nickel, chromium , manganese...equipment proposed at the GWTP, and the only NSPS source category that might be considered applicable to the existing thermal fume incinerator is Subpart E

Ground-Water Quality Data in the Middle Sacramento Valley Study Unit, 2006 - Results from the California GAMA Program

USGS Publications Warehouse

Schmitt, Stephen J.; Fram, Miranda S.; Milby Dawson, Barbara J.; Belitz, Kenneth

2008-01-01

Ground-water quality in the approximately 3,340 square mile Middle Sacramento Valley study unit (MSACV) was investigated from June through September, 2006, as part of the California Groundwater Ambient Monitoring and Assessment (GAMA) program. The GAMA Priority Basin Assessment project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The Middle Sacramento Valley study was designed to provide a spatially unbiased assessment of raw ground-water quality within MSACV, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 108 wells in Butte, Colusa, Glenn, Sutter, Tehama, Yolo, and Yuba Counties. Seventy-one wells were selected using a randomized grid-based method to provide statistical representation of the study unit (grid wells), 15 wells were selected to evaluate changes in water chemistry along ground-water flow paths (flow-path wells), and 22 were shallow monitoring wells selected to assess the effects of rice agriculture, a major land use in the study unit, on ground-water chemistry (RICE wells). The ground-water samples were analyzed for a large number of synthetic organic constituents (volatile organic compounds [VOCs], gasoline oxygenates and degradates, pesticides and pesticide degradates, and pharmaceutical compounds), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, and carbon-14, and stable isotopes of hydrogen, oxygen, nitrogen, and carbon), and dissolved noble gases also were measured to help identify the sources and ages of the sampled ground water. Quality-control samples (blanks, replicates, laboratory matrix spikes) were collected at approximately 10 percent of the wells, and the results for these samples were used to evaluate the quality of the data for the ground-water samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a noticeable source of bias in the data for the ground-water samples. Differences between replicate samples were within acceptable ranges, indicating acceptably low variability. Matrix spike recoveries were within acceptable ranges for most constituents. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, or blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH) and thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. Comparisons between data collected for this study and drinking-water thresholds are for illustrative purposes only and are not indicative of compliance or noncompliance with regulatory thresholds. Most constituents that were detected in ground-water samples were found at concentrations below drinking-water thresholds. VOCs were detected in less than one-third and pesticides and pesticide degradates in just over one-half of the grid wells, and all detections of these constituents in samples from all wells of the MSACV study unit were below health-based thresholds. All detections of trace elements in samples from MSACV grid wells were below health-based thresholds, with the exceptions of arsenic and boro

Facies analysis of Late Proterozoic through Lower Cambrian rocks of the Death Valley regional ground-water system and surrounding areas, Nevada and California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sweetkind, D.S.; White, D.K.

Late Proterozoic through Lower Cambrian rocks in the southern Great Basin form a westward-thickening wedge of predominantly clastic deposits that record deposition on the early western shelf edge of western North America (Stewart and Poole, 1974; Poole and others, 1992). Regional analyses of geologic controls on ground-water flow in the southern Great Basin typically combined lithostratigraphic units into more general hydrogeologic units that have considerable lateral extent and distinct hydrologic properties. The Late Proterozoic through Lower Cambrian rocks have been treated as a single hydrogeologic unit, named the lower clastic aquitard (Winograd and Thordarson, 1975) or the quartzite confining unitmore » (Laczniak and others, 1996), that serves as the hydrologic basement to the flow system. Although accurate in a general sense, this classification ignores well-established facies relations within these rocks that might increase bedrock permeability and locally influence ground-water flow . This report presents a facies analysis of Late Proterozoic through Lower Cambrian rocks (hereafter called the study interval) in the Death Valley regional ground-water flow system - that portion of the southern Great Basin that includes Death Valley, the Nevada Test Site, and the potential high-level nuclear waste underground repository at Yucca Mountain (fig. 1). The region discussed in this report, hereafter called the study area, covers approximately 100,000 km2 (lat 35 degrees-38 degrees 15'N., long 115 degrees-118 degrees W.). The purpose of this analysis is to provide a general documentation of facies transitions within the Late Proterozoic through Lower Cambrian rocks in order to provide an estimate of material properties (via rock type, grain size, and bedding characteristics) for specific hydrogeologic units to be included in a regional ground-water flow model.« less

Groundwater withdrawals under drought: reconciling GRACE and land surface models in the United States High Plains Aquifer

USDA-ARS?s Scientific Manuscript database

Advanced Land Surface Models (LSM) offer a powerful tool for studying hydrological variability. Highly managed systems, however, present a challenge for these models, which typically have simplified or incomplete representations of human water use. Here we examine recent groundwater declines in the ...

Potential effects of regional pumpage on groundwater age distribution

USGS Publications Warehouse

Zinn, Brendan A.; Konikow, Leonard F.

2007-01-01

Groundwater ages estimated from environmental tracers can help calibrate groundwater flow models. Groundwater age represents a mixture of traveltimes, with the distribution of ages determined by the detailed structure of the flow field, which can be prone to significant transient variability. Effects of pumping on age distribution were assessed using direct age simulation in a hypothetical layered aquifer system. A steady state predevelopment age distribution was computed first. A well field was then introduced, and pumpage caused leakage into the confined aquifer of older water from an overlying confining unit. Large changes in simulated groundwater ages occurred in both the aquifer and the confining unit at high pumping rates, and the effects propagated a substantial distance downgradient from the wells. The range and variance of ages contributing to the well increased substantially during pumping. The results suggest that the groundwater age distribution in developed aquifers may be affected by transient leakage from low‐permeability material, such as confining units, under certain hydrogeologic conditions.

40 CFR 257.22 - Ground-water monitoring systems.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Ground-water monitoring systems. 257... Waste Disposal Units Ground-Water Monitoring and Corrective Action § 257.22 Ground-water monitoring systems. (a) A ground-water monitoring system must be installed that consists of a sufficient number of...

40 CFR 257.22 - Ground-water monitoring systems.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Ground-water monitoring systems. 257... Waste Disposal Units Ground-Water Monitoring and Corrective Action § 257.22 Ground-water monitoring systems. (a) A ground-water monitoring system must be installed that consists of a sufficient number of...

Ground-water age, flow, and quality near a landfill, and changes in ground-water conditions from 1976 to 1996 in the Swinomish Indian Reservation, northwestern Washington

USGS Publications Warehouse

Thomas, B.E.; Cox, S.E.

1998-01-01

This report describes the results of two related studies: a study of ground-water age, flow, and quality near a landfill in the south-central part of the Swinomish Indian Reservation; and a study of changes in ground-water conditions for the entire reservation from 1976 to 1996. The Swinomish Indian Reservation is a 17-square-mile part of Fidalgo Island in northwestern Washington. The groundwater flow system in the reservation is probably independent of other flow systems in the area because it is almost completely surrounded by salt water. There has been increasing stress on the ground-water resources of the reservation because the population has almost tripled during the past 20 years, and 65 percent of the population obtain their domestic water supply from the local ground-water system. The Swinomish Tribe is concerned that increased pumping of ground water might have caused decreased ground-water discharge into streams, declines in ground-water levels, and seawater intrusion into the ground-water system. There is also concern that leachate from an inactive landfill containing mostly household and wood-processing wastes may be contaminating the ground water. The study area is underlain by unconsolidated glacial and interglacial deposits of Quaternary age that range from about 300 to 900 feet thick. Five hydrogeologic units have been defined in the unconsolidated deposits. From top to bottom, the hydrogeologic units are a till confining bed, an outwash aquifer, a clay confining bed, a sea-level aquifer, and an undifferentiated unit. The ground-water flow system of the reservation is similar to other island-type flow systems. Water enters the system through the water table as infiltration and percolation of precipitation (recharge), then the water flows downward and radially outward from the center of the island. At the outside edges of the system, ground water flows upward to discharge into the surrounding saltwater bodies. Average annual recharge is estimated to be about 3 inches, or 12 percent of the average annual precipitation. Ground water in the outwash aquifer near the landfill is estimated to be between 15 and 43 years old. Some deeper ground waters and ground water near the discharge areas close to the shoreline are older than 43 years. Analysis of water-quality data collected for this study and review of existing data indicate that material in the landfill has had no appreciable impact on the current quality of ground water outside of the landfill. The water quality of samples from seven wells near to and downgradient from the landfill appears to be similar to the ground-water quality throughout the entire study area. The high iron and manganese concentrations found in most of the samples from wells near the landfill are probably within the range of natural concentrations for the study area. Ground-water pumping during the past 20 years has not caused any large changes in ground-water discharge to streams, ground-water levels, or seawater intrusion into the ground-water system. Ground-water discharge into Snee-oosh Creek and Munks Creek had similar magnitudes in the summers of 1976 and 1996; flows in both creeks during those summers ranged from 0.07 t 0.15 cubic feet per second. Ground-water levels changed minimally between 1976 and 1996. The average water-level change for 20 wells with more than 10 years between measurements was -0.7 feet and the two largest waterlevel declines were 6 and 9 feet. No appreciable seawater intrusion was found in the ground water in 1996, and there was no significant increase in the extent of seawater intrusion from 1976 to 1996. Median chloride concentrations of water samples collected from wells were 22 milligrams per liter in 1976 and 18 milligrams per liter in 1996.

Codes for the identification of aquifer names and geologic units in the United States and the Caribbean outlying areas

USGS Publications Warehouse

,

1988-01-01

This standard provides codes to be used for the identification of aquifer names and geologic units in the United States, the Caribbean and other outlying areas. Outlying areas include Puerto Rico, the Virgin Islands, American Samoa, the Midway Islands, Trust Territories of the Pacific Islands, and miscellaneous Pacific Islands. Each code identifies an aquifer or rock-stratigraphic unit and its age designation. The codes provide a standardized base for use by organizations in the storage, retrieval, and exchange of ground-water data; the indexing and inventory of ground-water data and information; the cataloging of ground-water data acquisition activities; and a variety of other applications.

Codes for the identification of aquifer names and geologic units in the United States and the Caribbean outlying areas

USGS Publications Warehouse

,

1985-01-01

This standard provides codes to be used for the identification of aquifer names and geologic units in the United States, the Caribbean and other outlying areas. Outlying areas include Puerto Rico, the Virgin Islands, American Samoa, the Midway Islands, Trust Territories of the Pacific Islands, and miscellaneous Pacific Islands. Each code identifies an aquifer or rock-stratigraphic unit and its age designation. The codes provide a standardized base for use by organizations in the storage, retrieval, and exchange of ground-water data; the indexing and inventory of ground-water data and information; the cataloging of ground-water data acquisition activities; and a variety of other applications.

Temperature logging of groundwater in bedrock wells for geothermal gradient characterization in New Hampshire, 2012

USGS Publications Warehouse

Degnan, James; Barker, Gregory; Olson, Neil; Wilder, Leland

2012-01-01

Maximum groundwater temperatures at the bottom of the logs were between 11.7 and 17.3 degrees Celsius. Geothermal gradients were generally higher than typically reported for other water wells in the United States. Some of the high gradients were associated with high natural gamma emissions. Groundwater flow was discernible in 5 of the 10 wells studied but only obscured the portion of the geothermal gradient signal where groundwater actually flowed through the well. Temperature gradients varied by mapped bedrock type but can also vary by differences in mineralogy or rock type within the wells.

Development of unconfined conditions in multi-aquifer flow systems: a case study in the Rajshahi Barind, Bangladesh

NASA Astrophysics Data System (ADS)

Rushton, K. R.; Zaman, M. Asaduz

2017-01-01

Identifying flow processes in multi-aquifer flow systems is a considerable challenge, especially if substantial abstraction occurs. The Rajshahi Barind groundwater flow system in Bangladesh provides an example of the manner in which flow processes can change with time. At some locations there has been a decrease with time in groundwater heads and also in the magnitude of the seasonal fluctuations. This report describes the important stages in a detailed field and modelling study at a specific location in this groundwater flow system. To understand more about the changing conditions, piezometers were constructed in 2015 at different depths but the same location; water levels in these piezometers indicate the formation of an additional water table. Conceptual models are described which show how conditions have changed between the years 2000 and 2015. Following the formation of the additional water table, the aquifer system is conceptualised as two units. A pumping test is described with data collected during both the pumping and recovery phases. Pumping test data for the Lower Unit are analysed using a computational model with estimates of the aquifer parameters; the model also provided estimates of the quantity of water moving from the ground surface, through the Upper Unit, to provide an input to the Lower Unit. The reasons for the substantial changes in the groundwater heads are identified; monitoring of the recently formed additional water table provides a means of testing whether over-abstraction is occurring.

Groundwater-Quality Data in the Colorado River Study Unit, 2007: Results from the California GAMA Program

USGS Publications Warehouse

Goldrath, Dara A.; Wright, Michael T.; Belitz, Kenneth

2010-01-01

Groundwater quality in the 188-square-mile Colorado River Study unit (COLOR) was investigated October through December 2007 as part of the Priority Basin Project of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001, and the U.S. Geological Survey (USGS) is the technical project lead. The Colorado River study was designed to provide a spatially unbiased assessment of the quality of raw groundwater used for public water supplies within COLOR, and to facilitate statistically consistent comparisons of groundwater quality throughout California. Samples were collected from 28 wells in three study areas in San Bernardino, Riverside, and Imperial Counties. Twenty wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the Study unit; these wells are termed 'grid wells'. Eight additional wells were selected to evaluate specific water-quality issues in the study area; these wells are termed `understanding wells.' The groundwater samples were analyzed for organic constituents (volatile organic compounds [VOC], gasoline oxygenates and degradates, pesticides and pesticide degradates, pharmaceutical compounds), constituents of special interest (perchlorate, 1,4-dioxane, and 1,2,3-trichlorpropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), and radioactive constituents. Concentrations of naturally occurring isotopes (tritium, carbon-14, and stable isotopes of hydrogen and oxygen in water), and dissolved noble gases also were measured to help identify the sources and ages of the sampled groundwater. In total, approximately 220 constituents and water-quality indicators were investigated. Quality-control samples (blanks, replicates, and matrix spikes) were collected at approximately 30 percent of the wells, and the results were used to evaluate the quality of the data obtained from the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a significant source of bias in the data. Differences between replicate samples were within acceptable ranges and matrix-spike recoveries were within acceptable ranges for most compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, raw groundwater typically is treated, disinfected, or blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to water that is served to the consumer, not to raw groundwater. However, to provide some context for the results, concentrations of constituents measured in the raw groundwater were compared to regulatory and nonregulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH) and to thresholds established for aesthetic concerns by CDPH. Comparisons between data collected for this study and drinking-water thresholds are for illustrative purposes only and do not indicate compliance or noncompliance with those thresholds. The concentrations of most constituents detected in groundwater samples were below drinking-water thresholds. Volatile organic compounds (VOC) were detected in approximately 35 percent of grid well samples; all concentrations were below health-based thresholds. Pesticides and pesticide degradates were detected in about 20 percent of all samples; detections were below health-based thresholds. No concentrations of constituents of special interest or nutrients were detected above health-based thresholds. Most of the major and minor ion constituents sampled do not have health-based thresholds; the exception is chloride. Concentrations of chloride, sulfate, and total dis

Assessment of hydrogeochemical status of groundwater in a coastal region of Southeast coast of India

NASA Astrophysics Data System (ADS)

Chidambaram, S.; Sarathidasan, J.; Srinivasamoorthy, K.; Thivya, C.; Thilagavathi, R.; Prasanna, M. V.; Singaraja, C.; Nepolian, M.

2018-03-01

A study was conducted in a coastal region of Cuddalore district of Tamil Nadu, India, to identify the hydrogeochemical processes controlling the groundwater chemistry. The major geological units of the study area are sandstone, clay, alluvium, and laterite soils of Tertiary and Quaternary age. A total of 64 groundwater samples were measured for major ions and stable isotopes. Higher electrical conductivity values indicate the poor quality groundwater along the coastal region. Saline water intrusion mainly affects the hydrochemical composition of the aquifer water reflected by Na-Cl-type waters. Cl-/(Cl- + HCO3 -) ratio also indicates the mixing of fresh groundwater with saline water. The results of δD and δ18O analyses show that isotopic compositions of groundwater ranges from - 7.7 to - 2.1‰ for δ18O and from - 55.6 to - 18.5‰ for δD. Correlation and factor analysis were carried out to find the association of ions and to determine the major factors controlling the groundwater chemistry of the region. The study indicates that ion exchange, weathering, salt water intrusion along the coast, and anthropogenic impacts are the major controlling factors for the groundwater chemistry of the region.

Estimates of ground-water discharge as determined from measurements of evapotranspiration, Ash Meadows area, Nye County, Nevada

USGS Publications Warehouse

Laczniak, R.J.; DeMeo, G.A.; Reiner, S.R.; Smith, J. LaRue; Nylund, W.E.

1999-01-01

Ash Meadows is one of the major discharge areas within the regional Death Valley ground-water flow system of southern Nevada and adjacent California. Ground water discharging at Ash Meadows is replenished from inflow derived from an extensive recharge area that includes the eastern part of the Nevada Test Site (NTS). Currently, contaminants introduced into the subsurface by past nuclear testing at NTS are the subject of study by the U.S. Department of Energy's Environmental Restoration Program. The transport of any contaminant in contact with ground water is controlled in part by the rate and direction of ground-water flow, which itself depends on the location and quantity of ground water discharging from the flow system. To best evaluate any potential risk associated with these test-generated contaminants, studies were undertaken to accurately quantify discharge from areas downgradient from the NTS. This report presents results of a study to refine the estimate of ground-water discharge at Ash Meadows. The study estimates ground-water discharge from the Ash Meadows area through a rigorous quantification of evapotranspiration (ET). To accomplish this objective, the study identifies areas of ongoing ground-water ET, delineates unique areas of ET defined on the basis of similarities in vegetation and soil-moisture conditions, and computes ET rates for each of the delineated areas. A classification technique using spectral-reflectance characteristics determined from satellite images recorded in 1992 identified seven unique units representing areas of ground-water ET. The total area classified encompasses about 10,350 acres dominated primarily by lush desert vegetation. Each unique area, referred to as an ET unit, generally consists of one or more assemblages of local phreatophytes. The ET units identified range from sparse grasslands to open water. Annual ET rates are computed by energy-budget methods from micrometeorological measurements made at 10 sites within six of the seven identified ET units. Micrometeorological data were collected for a minimum of 1 year at each site during 1994 through 1997. Evapotranspiration ranged from 0.6 foot per year in a sparse, dry saltgrass environment to 8.6 feet per year over open water. Ancillary data, including water levels, were collected during this same period to gain additional insight into the evapotranspiration process. Water levels measured in shallow wells showed annual declines of more than 10 feet and daily declines as high as 0.3 foot attributed to water losses associated with evapotranspiration. Mean annual ET from the Ash Meadows area is estimated at 21,000 acre-feet. An estimate of ground-water discharge, based on this ET estimate, is presented as a range to account for uncertainties in the contribution of local precipitation. The estimates given for mean annual ground-water discharge range from 18,000 to 21,000 acre-feet. The low estimate assumes a large contribution from local precipitation in computed ET rates; whereas, the high estimate assumes no contribution from local precipitation. The range presented is only slightly higher than previous estimates of ground-water discharge from the Ash Meadows area based primarily on springflow measurements.

A zonal evaluation of intrinsic susceptibility in selected principal aquifers of the United States

USGS Publications Warehouse

Wellman, Tristan P.; Kauffman, Leon; Clark, Brian

2012-01-01

A method was developed to evaluate intrinsic groundwater susceptibility in 11 study areas across the United States. Calibrated groundwater-flow models and a variable-advection particle-tracking scheme that accounts for uncertainty were used to derive ranges of conservative solute concentration and groundwater age within spatially defined zones from solute loading to the water table. Aquifers were partitioned into six zones; four relative depth zones and two zones to represent pumping wells and surface water. Five years after solute was introduced in simulated recharge and stream leakage, normalized zone concentrations were detected at values above 10-4 in the shallowest aquifer zone, well zone, and surface-water zone for 10 of the 11 study areas. At the 125-year time scale, 9 out of the 11 study areas exhibited detectable concentrations in all zones and the majority of zones possess concentrations that are substantial relative to the source concentration (ClCo > 10-1). Thresholds defined by the time representing the earliest 1% of groundwater-transit times were used to identify fast transport pathways within the groundwater. The 1% thresholds occurred in a period of days to years for the shallow zone, days to decades for the well and surface-water zones, and years to millennia for the deeper zones. Thresholds defined by the 99th percentile of groundwater travel times were used to reflect late-time response and ranged considerably between study area (~102 to ~106 years), which highlights the potential for chemical constituents to persist in groundwater for long periods under a conservative state. The results of this investigation provide an instructive example of the intricate relations between climate and aquifer characteristics and their role on solute transport in groundwater. The proposed method accounts for dynamical processes in the aquifer and complements more traditional assessments of susceptibility using (apparent) mean water age.

High Plains regional ground-water study

USGS Publications Warehouse

Dennehy, Kevin F.

2000-01-01

Over the last 25 years, industry and government have made large financial investments aimed at improving water quality across the Nation. Significant progress has been made; however, many water-quality concerns remain. In 1991, the U.S. Geological Survey (USGS) began implementing a full-scale National Water-Quality Assessment Program to provide consistent and scientifically sound information for managing the Nation's water resources. The goals of the NAWQA Program are to (1) describe current water-quality conditions for a large part of the Nation's freshwater streams and aquifers, (2) describe how water quality is changing over time, and (3) improve our understanding of the primary natural and human factors affecting water quality. Assessing the quality of water in every location in the Nation would not be practical; therefore, NAWQA Program studies are conducted within a set of areas called study units (fig. 1). These study units are composed of more than 50 important river and aquifer systems that represent the diverse geography, water resources, and land and water uses of the Nation. The High Plains Regional Ground-Water Study is one such study area, designed to address issues relevant to the High Plains Aquifer system while supplementing water-quality information collected in other study units across the Nation. Implementation of the NAWQA Program for the High Plains Regional Ground-Water Study area began in 1998.

Status and understanding of groundwater quality in the Monterey-Salinas Shallow Aquifer Study Unit, 2012–13: California GAMA Priority Basin Project

USGS Publications Warehouse

Burton, Carmen; Wright, Michael

2018-05-30

Groundwater quality in the approximately 7,820-square-kilometer (km2) Monterey-Salinas Shallow Aquifer (MS-SA) study unit was investigated from October 2012 to May 2013 as part of the second phase of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is in the central coast region of California in the counties of Santa Cruz, Monterey, and San Luis Obispo. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in cooperation with the U.S. Geological Survey and the Lawrence Livermore National Laboratory.The MS-SA study was designed to provide a statistically robust assessment of untreated-groundwater quality in the shallow aquifer systems. The assessment was based on water-quality samples collected by the U.S. Geological Survey from 100 groundwater sites and 70 household tap sites, along with ancillary data such as land use and well-construction information. The shallow aquifer systems were defined by the depth interval of wells associated with domestic supply. The MS-SA study unit consisted of four study areas—Santa Cruz (210 km2), Pajaro Valley (360 km2), Salinas Valley (2,000 km2), and Highlands (5,250 km2).This study had two primary components: the status assessment and the understanding assessment. The first primary component of this study—the status assessment—assessed the quality of the groundwater resource indicated by data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally present inorganic constituents, such as major ions and trace elements. The status assessment is intended to characterize the quality of groundwater resources in the shallow aquifer system of the MS-SA study unit, not the treated drinking water delivered to consumers by water purveyors. As opposed to the public wells, however, water from private wells, which often tap the shallow aquifer, is usually consumed without any treatment. The second component of this study—the understanding assessment—identified the natural and human factors that potentially affect groundwater quality by evaluating land-use characteristics, measures of location, geologic factors, groundwater age, and geochemical conditions of the shallow aquifer. An additional component of this study was a comparison of MS-SA water-quality results to those of the GAMA Monterey Bay and Salinas Valley Groundwater Basins study unit. This study unit covered much of the same areal extent as the MS-SA, but assessed the deeper, public drinking-water aquifer system.Relative concentrations (sample concentration divided by the benchmark concentration) were used to evaluate concentrations of constituents in groundwater samples relative to water-quality benchmarks for those constituents that have Federal or California benchmarks, such as maximum contaminant levels. For organic and special-interest constituents, relative concentrations were classified as high, greater than 1.0; moderate, greater than 0.1 and less than or equal to 1.0; or low, less than or equal to 0.1. For inorganic constituents, relative concentrations were classified as high, greater than 1.0; moderate, greater than 0.5 and less than or equal to 1.0; or low, less than or equal to 0.5. A relative concentration greater than 1.0 indicates that the concentration was greater than a benchmark. Aquifer-scale proportions were used to quantify regional-scale groundwater quality. The aquifer-scale proportions are the areal percentages of the shallow aquifer system where relative concentrations for a given constituent or class of constituents were high, moderate, or low.Inorganic constituents were measured at high and moderate relative concentrations more frequently than organic constituents. In the MS-SA study unit, inorganic constituents with benchmarks were detected at high relative concentrations in 51 percent of the study unit. The greatest proportions of high relative concentrations of trace elements and radioactive constituents were in the Highlands and Santa Cruz study areas, whereas high relative concentrations of nutrients were most often detected in the Salinas Valley and Pajaro Valley study areas and salinity indicators were most often detected in the Highlands and Salinas Valley study areas. The trace elements detected at high relative concentrations were arsenic, boron, iron, manganese, molybdenum, selenium, and strontium. The radioactive constituents detected at high relative concentrations were adjusted gross alpha radioactivity and uranium. The nutrient detected at high relative concentrations was nitrate plus nitrite. The salinity indicators detected at high relative concentrations were chloride, sulfate, and total dissolved solids.Organic constituents (VOCs and pesticides) were not detected at high relative concentrations in any of the study areas. The fumigant 1,2-dichloropropane was detected at moderate relative concentrations. The VOC chloroform and the pesticide simazine were the only organic constituents detected in more than 10 percent of samples. The constituents of special interest NDMA (N-nitrosodimethylamine) and perchlorate were detected at high relative concentrations in the MS-SA study unit.Selected constituents were evaluated with explanatory factors to identify potential sources or processes that could explain their presence and distribution. Trace elements and radioactive constituents came from natural sources and were not elevated by anthropogenic sources or processes, except for selenium and the radioactive constituent uranium. Arsenic, manganese, iron, selenium, and uranium concentrations were all influenced by oxidation-reduction conditions.Unlike other trace elements and radioactive constituents, uranium and selenium can be affected by agricultural practices. Uranium and selenium can be released from aquifer sediments as a result of irrigation recharge water interacting with bicarbonate systems.Nitrate can be strongly affected by anthropogenic sources. Nitrate concentrations were significantly higher in modern groundwater, indicating recent inputs of nitrate to the shallow aquifer system. Nitrate was positively correlated with agricultural land use, indicating that irrigation-return water could be leaching nitrogen fertilizer and naturally present nitrate to elevate nitrate concentrations in shallow groundwater.The salinity indicators total dissolved solids, chloride, and sulfate all had natural sources in the MS-SA study unit, primarily marine sediments. Concentrations of the constituents were elevated as a result of evaporative concentration of irrigation water or precipitation. Sulfate concentrations were significantly correlated to agricultural land use, indicating that agricultural land-use practices are a contributing source of sulfate to groundwater.The samples with most of the detections of VOCs were from sites in the Pajaro Valley and northern part of the Salinas Valley. Most of the samples with pesticide detections were from sites in the Salinas Valley study area. The herbicide simazine was positively correlated to the percentage of agricultural land use, and its concentrations were higher in modern groundwater than in pre-modern groundwater.Perchlorate, similar to nitrate, has natural and anthropogenic sources. Correlations of perchlorate to dissolved oxygen, nitrate, and percentage of agricultural land use indicated that the irrigation-return water could be leaching naturally present perchlorate, as well as perchlorate from historical applications of Chilean nitrate fertilizer, to increase perchlorate concentrations in groundwater.The quality of the water in the shallow aquifer system from this study was compared with the quality of water in the public drinking-water aquifer in a previous GAMA (MS-PA) study in the same area. The shallow system was more oxic and had more sites with modern groundwater than the public drinking-water aquifer, which was more anoxic and had sites with more pre-modern groundwater. Arsenic and selenium were found at high relative concentrations in a greater proportion of the shallow system. Manganese and iron were found at high relative concentrations in a greater proportion of the public drinking-water aquifer. Uranium was found at higher relative concentrations in a greater proportion of the shallow system. Concentrations of arsenic, iron, manganese, and molybdenum are not likely to change much as groundwater percolates from the shallow system to the public drinking-water aquifer because there are no anthropogenic sources affecting these constituents. Uranium and selenium concentrations in the public drinking-water aquifer could be affected by the higher concentrations in the shallow system because of irrigation-return water, however.Nitrate and salinity indicators had concentrations that were much higher in the shallow system than the deeper public drinking-water aquifer. High concentrations of these constituents in the shallow system could lead to increased concentrations in the public drinking-water aquifer in parts of the study units because of land-use practices, such as irrigated agriculture.Organic constituents were detected more frequently in the public drinking-water aquifer than in the shallow system, possibly because more of the sites sampled in the public drinking-water aquifer were in urban areas compared to the sites sampled for the shallow system or because sources of contamination have decreased as a result of changes in use at the land surface.

Development of a regional groundwater flow model for the area of the Idaho National Engineering Laboratory, Eastern Snake River Plain Aquifer

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCarthy, J.M.; Arnett, R.C.; Neupauer, R.M.

This report documents a study conducted to develop a regional groundwater flow model for the Eastern Snake River Plain Aquifer in the area of the Idaho National Engineering Laboratory. The model was developed to support Waste Area Group 10, Operable Unit 10-04 groundwater flow and transport studies. The products of this study are this report and a set of computational tools designed to numerically model the regional groundwater flow in the Eastern Snake River Plain aquifer. The objective of developing the current model was to create a tool for defining the regional groundwater flow at the INEL. The model wasmore » developed to (a) support future transport modeling for WAG 10-04 by providing the regional groundwater flow information needed for the WAG 10-04 risk assessment, (b) define the regional groundwater flow setting for modeling groundwater contaminant transport at the scale of the individual WAGs, (c) provide a tool for improving the understanding of the groundwater flow system below the INEL, and (d) consolidate the existing regional groundwater modeling information into one usable model. The current model is appropriate for defining the regional flow setting for flow submodels as well as hypothesis testing to better understand the regional groundwater flow in the area of the INEL. The scale of the submodels must be chosen based on accuracy required for the study.« less

Hydrogeologic and geochemical characterization of groundwater resources in Rush Valley, Tooele County, Utah

USGS Publications Warehouse

Gardner, Philip M.; Kirby, Stefan

2011-01-01

The water resources of Rush Valley were assessed during 2008–2010 with an emphasis on refining the understanding of the groundwater-flow system and updating the groundwater budget. Surface-water resources within Rush Valley are limited and are generally used for agriculture. Groundwater is the principal water source for most other uses including supplementing irrigation. Most groundwater withdrawal in Rush Valley is from the unconsolidated basin-fill aquifer where conditions are generally unconfined near the mountain front and confined at lower altitudes near the valley center. Productive aquifers also occur in fractured bedrock along the valley margins and beneath the basin-fill deposits in some areas.Drillers’ logs and geophysical gravity data were compiled and used to delineate seven hydrogeologic units important to basin-wide groundwater movement. The principal basin-fill aquifer includes the unconsolidated Quaternary-age alluvial and lacustrine deposits of (1) the upper basin-fill aquifer unit (UBFAU) and the consolidated and semiconsolidated Tertiary-age lacustrine and alluvial deposits of (2) the lower basin-fill aquifer unit (LBFAU). Bedrock hydrogeologic units include (3) the Tertiary-age volcanic unit (VU), (4) the Pennsylvanian- to Permian-age upper carbonate aquifer unit (UCAU), (5) the upper Mississippian- to lower Pennsylvanian-age upper siliciclastic confining unit (USCU), (6) the Middle Cambrian- to Mississippian-age lower carbonate aquifer unit (LCAU), and (7) the Precambrian- to Lower Cambrian-age noncarbonate confining unit (NCCU). Most productive bedrock wells in the Rush Valley groundwater basin are in the UCAU.Average annual recharge to the Rush Valley groundwater basin is estimated to be about 39,000 acre-feet. Nearly all recharge occurs as direct infiltration of snowmelt and rainfall within the mountains with smaller amounts occurring as infiltration of streamflow and unconsumed irrigation water at or near the mountain front. Groundwater generally flows from the higher altitude recharge areas toward two distinct valley-bottom discharge areas: one in the vicinity of Rush Lake in northern Rush Valley and the other located west and north of Vernon. Average annual discharge from the Rush Valley groundwater basin is estimated to be about 43,000 acre-feet. Most discharge occurs as evapotranspiration in the valley lowlands, as discharge to springs and streams, and as withdrawal from wells. Subsurface discharge outflow to Tooele and Cedar Valleys makes up only a small fraction of natural discharge.Groundwater samples were collected from 25 sites (24 wells and one spring) for geochemical analysis. Dissolved-solids concentrations in water from these sites ranged from 181 to 1,590 milligrams per liter. Samples from seven wells contained arsenic concentrations that exceed the Environmental Protection Agency Maximum Contaminant Level of 10 micrograms per liter. The highest arsenic levels are found north of Vernon and in southeastern Rush Valley. Stable-isotope ratios of oxygen and deuterium, along with dissolved-gas recharge temperatures, indicate that nearly all modern groundwater is meteoric and derived from the infiltration of high altitude precipitation in the mountains. These data are consistent with recharge estimates made using a Basin Characterization Model of net infiltration that shows nearly all recharge occurring as infiltration of precipitation and snowmelt within the mountains surrounding Rush Valley. Tritium concentrations between 0.4 and 10 tritium units indicate the presence of modern (less than 60 years old) groundwater at 7 of the 25 sample sites. Apparent 3H/3He ages, calculated for six of these sites, range from 3 to 35 years. Adjusted minimum radiocarbon ages of premodern water samples range from about 1,600 to 42,000 years with samples from 11 of 13 sites being more than 11,000 years. These data help to identify areas where modern groundwater is circulating through the hydrologic system on time scales of decades or less and indicate that large parts of the principal basin-fill and the bedrock aquifers are much less active and receive little to no modern recharge.

Estimates of groundwater age from till and carbonate bedrock hydrogeologic units at Jefferson Proving Ground, Southeastern Indiana, 2007-08

USGS Publications Warehouse

Buszka, Paul M.; Lampe, David C.; Egler, Amanda L.

2010-01-01

During 2007-08, the U.S. Geological Survey, in cooperation with the U.S. Department of the Army, conducted a study to evaluate the relative age of groundwater in Pre-Wisconsinan till and underlying shallow and deep carbonate bedrock units in and near an area at Jefferson Proving Ground (JPG), southeastern Indiana, which was used during 1984-94 to test fire depleted uranium (DU) penetrators. The shallow carbonate unit includes about the upper 40 feet of bedrock below the bedrock-till surface; the deeper carbonate unit includes wells completed at greater depth. Samples collected during April 2008 from 15 wells were analyzed for field water-quality parameters, dissolved gases, tritium, and chlorofluorocarbon (CFC) compounds; samples from 14 additional wells were analyzed for tritium only. Water-level gradients in the Pre-Wisconsinan till and the shallow carbonate unit were from topographically higher areas toward Big Creek and Middle Fork Creek, and their tributaries. Vertical gradients were strongly downward from the shallow carbonate unit toward the deep carbonate unit at 3 of 4 paired wells where water levels recovered after development; indicating the general lack of flow between the two units. The lack of post development recovery of water levels at 4 other wells in the deep carbonate unit indicate that parts of that unit have no appreciable permeability. CFC and tritium-based age dates of Pre-Wisconsinan till groundwater are consistent with infiltration of younger (typically post-1960 age) recharge that 'mixes' with older recharge from less permeable or less interconnected strata. Part of the recharge to three till wells dated from the early to mid-1980s (JPG-DU-03O, JPG-DU-09O, and JPG-DU-10O). Age dates of young recharge in water from two till wells predated 1980 (JPG-DU-04O and JPG-DU-06O). Tritium-based age dates of water from seven other till wells indicated post-1972 age recharge. Most wells in the Pre-Wisconsinan till have the potential to produce groundwater that partially was recharged during or after DU penetrator testing; their water quality can indicate the presence of DU-related contaminants. The shallow carbonate unit near Big Creek is a karst flow system that may be recharged in part from areas with smaller thicknesses of overlying till or through more permeable parts of the till. This is indicated by CFC- and tritium-based piston-flow (non-mixing) model age dates of early-1980s for water from JPG-DU-02I, similar tritium-based ages of water produced from nearby wells MW-5 and MW-11, and cave development along the creek. The CFC and tritium-based age dates indicate that water samples from JPG-DU-01I and JPG-DU-03I were best described as mixtures of post-1984 modern recharge and submodern (1953 or older) recharge. These five wells produced groundwater that was recharged, at least partially, during or after DU-penetrator testing and are within or downgradient from the DU Impact Area with respect to groundwater flow directions inferred from water-level contours. Wells with groundwater age dates that are near to or after the onset (1984) of DU penetrator testing and that have a plausible connection to a contaminant source can be used to indicate the presence or absence of contaminants from DU penetrator or DU-related corrosion products in groundwater. Groundwater-age dates indicate that the ages of recharge sampled from shallow carbonate unit wells JPG-DU-04I, JPG-DU-05I, JPG-DU-06I, JPG-DU-09I, and JPG-DU-10D in easternmost (upgradient) and southernmost wells in the shallow carbonate unit are submodern (1953 or older) and predate the DU testing by at least 30 or more years. Water-quality data from these five wells are not likely to represent effects from DU-projectile testing or corrosion for years. Well JPG-DU-09D in the deep carbonate unit produced groundwater samples with a submodern (1953 or older) age date. The slow recovery of water levels in most wells in the deep carbonate unit is consis

Groundwater Quality Data for the Tahoe-Martis Study Unit, 2007: Results from the California GAMA Program

USGS Publications Warehouse

Fram, Miranda S.; Munday, Cathy; Belitz, Kenneth

2009-01-01

Groundwater quality in the approximately 460-square-mile Tahoe-Martis study unit was investigated in June through September 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The study was designed to provide a spatially unbiased assessment of the quality of raw groundwater used for public water supplies within the Tahoe-Martis study unit (Tahoe-Martis) and to facilitate statistically consistent comparisons of groundwater quality throughout California. Samples were collected from 52 wells in El Dorado, Placer, and Nevada Counties. Forty-one of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study area (grid wells), and 11 were selected to aid in evaluation of specific water-quality issues (understanding wells). The groundwater samples were analyzed for a large number of synthetic organic constituents (volatile organic compounds [VOC], pesticides and pesticide degradates, and pharmaceutical compounds), constituents of special interest (perchlorate and N-nitrosodimethylamine [NDMA]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, carbon-14, strontium isotope ratio, and stable isotopes of hydrogen and oxygen of water), and dissolved noble gases also were measured to help identify the sources and ages of the sampled groundwater. In total, 240 constituents and water-quality indicators were investigated. Three types of quality-control samples (blanks, replicates, and samples for matrix spikes) each were collected at 12 percent of the wells, and the results obtained from these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that data for the groundwater samples were not compromised by possible contamination during sample collection, handling or analysis. Differences between replicate samples were within acceptable ranges. Matrix spike recoveries were within acceptable ranges for most compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, raw water typically is treated, disinfected, or blended with other waters to maintain water quality. Regulatory thresholds apply to water that is served to the consumer, not to raw groundwater. However, to provide some context for the results, concentrations of constituents measured in the raw groundwater were compared with regulatory and nonregulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH), and with aesthetic and technical thresholds established by CDPH. Comparisons between data collected for this study and drinking-water thresholds are for illustrative purposes only and do not indicate of compliance or noncompliance with regulatory thresholds. The concentrations of most constituents detected in groundwater samples from the Tahoe-Martis wells were below drinking-water thresholds. Organic compounds (VOCs and pesticides) were detected in about 40 percent of the samples from grid wells, and most concentrations were less than 1/100th of regulatory and nonregulatory health-based thresholds, although the conentration of perchloroethene in one sample was above the USEPA maximum contaminant level (MCL-US). Concentrations of all trace elements and nutrients in samples from grid wells were below regulatory and nonregulatory health-based thresholds, with five exceptions. Concentra

Well Construction Details, Groundwater Elevations, and Figures for the Tijeras Arroyo Groundwater Area at Sandia National Laboratories, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Copland, John R.

This Sandia National Laboratories / New Mexico (SNL/NM) submittal contains groundwater information that the United States Geological Survey (USGS) has requested. The USGS will use the information to assist Kirtland Air Force Base (KAFB) in its ongoing groundwater studies. The information in this submittal contains well-construction details and groundwater-elevation data for monitoring wells that SNL/NM has installed. Relevant well-construction data from other government agencies are also summarized. This submittal contains four data tables and three figures. Information in the tables has been used by SNL/NM to prepare groundwater compliance reports that have previously incorporated the three figures. The figures depictmore » the potentiometric surface for the Perched Groundwater System, the potentiometric surface for the Regional Aquifer, and a Conceptual Site Model for the vicinity of Tijeras Arroyo in the northern portion of KAFB.« less

Investigating Vertical Mixing Between Two Carbonate Aquifers Using a Multiport Well, Central Texas

NASA Astrophysics Data System (ADS)

Kromann, J.; Wong, C. I.; Hunt, B.; Smith, B.; Banner, J. L.

2011-12-01

Determining the occurrence and extent of mixing between vertically-adjacent aquifers is critical to dual-aquifer management. This can be challenging due to variable well depths and uncertainty as to hydrostratigraphic sources of groundwater. This study uses a multiport monitor well to investigate the degree of aquifer mixing between the overlying Edwards aquifer and underlying Trinity aquifer in central Texas. The results will inform dual-aquifer management as the Trinity aquifer is being developed as an alternative water source to the Edwards aquifer due to pumping limits and projections of increasing water demand. Water levels from isolated hydrostratigraphic units (n = 19) were measured monthly in the well as climate conditions transitioned from wet to dry (Sept 2010 to May 2011). Groundwater was sampled over a two-week interval in May to June 2011. At the start of the monitoring interval, water levels were high in the Edwards and the uppermost units of the Trinity relative to the rest of the Trinity units. Water levels decreased to lower elevations, from about 635 to 585 ft-msl, under dry conditions. Water levels in the lowermost Trinity declined less, from about 630 to 620 ft-msl, under dry conditions. Two zones separating the Edwards and lowermost Trinity showed almost no head change during this period. The water-level variations between the two aquifers suggest that: i) vertical flow potential from the Edwards to the Trinity occurs during dry conditions, ii) the uppermost stratigraphic units of the Trinity and Edwards are mixing, and iii) portions of the Trinity behave as an aquitard, providing hydrologic separation between the Edwards and lowermost Trinity units. Groundwater samples indicate the presence of three distinct hydrochemical facies: Ca-HCO3 (Edwards), Ca-HCO3-SO4 (lowermost Trinity), and Ca-SO4 (Trinity-Glen Rose Fm), suggesting little vertical flow and mixing. Covariation between groundwater 87Sr/86Sr values and SO4 concentrations from units of the Edwards and lowermost Trinity units can be accounted for by a two-end-member fluid mixing model, which uses a unit from the Edwards and lowermost Trinity as end members. This may indicate that 87Sr/86Sr values and SO4 concentrations are controlled by varying extents of mixing between the two units. Groundwater from units in the Glen Rose Formation (between the Edwards and lowermost Trinity units) cannot be accounted for by this mixing process due to elevated SO4 concentrations likely associated with dissolution of evaporites. 87Sr/86Sr values of evaporites recovered from the well are consistent with 87Sr/86Sr values of groundwater from these Glen Rose units. Although the geochemical model results suggest possible mixing between the Edwards and Trinity aquifers, water-level variations and the presence of distinct hydrochemical facies indicate that vertical flow between the Edwards and Trinity is limited to the uppermost units of the Trinity. This study suggests that the Edwards aquifer and lowermost Trinity units are not likely in hydrologic communication and independent management may be possible.

The influence of vegetation on the hydrodynamics and geomorphology of a tree island in Everglades National Park (Florida, United States)

USGS Publications Warehouse

Sullivan, Pamela L.; Engel, Victor C.; Ross, Michael S.; Price, René M.

2013-01-01

Transpiration-driven nutrient accumulation has been identified as a potential mechanism governing the creation and maintenance of wetland vegetation patterning. This process may contribute to the formation of nutrient-rich tree islands within the expansive oligotrophic marshes of the Everglades (Florida, United States). This study presents hydrogeochemical data indicating that tree root water uptake is a primary driver of groundwater ion accumulation across one of these islands. Sap flow, soil moisture, water level, water chemistry, and rainfall were measured to identify the relationships between climate, transpiration, and groundwater uptake by phreatophytes and to examine the effect this uptake has on groundwater chemistry and mineral formation in three woody plant communities of differing elevations. During the dry season, trees relied more on groundwater for transpiration, which led to a depressed water table and the advective movement of groundwater and dissolved ions, including phosphorus, from the surrounding marsh towards the centre of the island. Ion exclusion during root water uptake led to elevated concentrations of all major dissolved ions in the tree island groundwater compared with the adjacent marsh. Groundwater was predominately supersaturated with respect to aragonite and calcite in the lower-elevation woody communities, indicating the potential for soil formation. Elevated groundwater phosphorous concentrations detected in the highest-elevation woody community were associated with the leaching of inorganic sediments (i.e. hydroxyapatite) in the vadose zone. Understanding the complex feedback mechanisms regulating plant/groundwater/surface water interactions, nutrient dynamics, and potential soil formation is necessary to manage and restore patterned wetlands such as the Everglades.

Evaluation of the importance of clay confining units on groundwaterflow in alluvial basins using solute and isotope tracers: the case of Middle San Pedro Basin in southeastern Arizona (USA)

USGS Publications Warehouse

Hopkins, Candice B.; McIntosh, Jennifer C.; Eastoe, Chris; Dickinson, Jesse; Meixner, Thomas

2014-01-01

As groundwater becomes an increasingly important water resource worldwide, it is essential to understand how local geology affects groundwater quality, flowpaths and residence times. This study utilized multiple tracers to improve conceptual and numerical models of groundwater flow in the Middle San Pedro Basin in southeastern Arizona (USA) by determining recharge areas, compartmentalization of water sources, flowpaths and residence times. Ninety-five groundwater and surface-water samples were analyzed for major ion chemistry (water type and Ca/Sr ratios) and stable (18O, 2H, 13C) and radiogenic (3H, 14C) isotopes, and resulting data were used in conjunction with hydrogeologic information (e.g. hydraulic head and hydrostratigraphy). Results show that recent recharge (<60 years) has occurred within mountain systems along the basin margins and in shallow floodplain aquifers adjacent to the San Pedro River. Groundwater in the lower basin fill aquifer (semi confined) was recharged at high elevation in the fractured bedrock and has been extensively modified by water-rock reactions (increasing F and Sr, decreasing 14C) over long timescales (up to 35,000 years BP). Distinct solute and isotope geochemistries between the lower and upper basin fill aquifers show the importance of a clay confining unit on groundwater flow in the basin, which minimizes vertical groundwater movement.

Phase I and II feasibility study report for the 300-FF-5 operable unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1993-12-31

The purpose of this Phase I/II feasibility study is to assemble and screen a list of alternatives for remediation of the 300-FF-5 operable site on the Hanford Reservation. This screening is based on information gathered in the Phase I Remedial Investigation (RI) and on currently available information on remediation technologies. The alternatives remaining after screening provide a range of response actions for remediation. In addition, key data needs are identified for collection during a Phase II RI (if necessary). This Phase I/II FS represents a primary document as defined by the Tri-Party Agreement, but will be followed by a Phasemore » III FS that will further develop the alternatives and provide a detailed evaluation of them. The following remedial action objectives were identified for the 300-FF-5 operable unit: Limit current human exposure to contaminated groundwater in the unit; Limit discharge of contaminated groundwater to the Columbia River; Reduce contaminant concentrations in groundwater below acceptable levels by the year 2018.« less

Ground-water quality assessment of the central Oklahoma Aquifer, Oklahoma; project description

USGS Publications Warehouse

Christenson, S.C.; Parkhurst, D.L.

1987-01-01

In April 1986, the U.S. Geological Survey began a pilot program to assess the quality of the Nation's surface-water and ground-water resources. The program, known as the National Water-Quality Assessment (NAWQA) program, is designed to acquire and interpret information about a variety of water-quality issues. The Central Oklahoma aquifer project is one of three ground-water pilot projects that have been started. The NAWQA program also incudes four surface-water pilot projects. The Central Oklahoma aquifer project, as part of the pilot NAWQA program, will develop and test methods for performing assessments of ground-water quality. The objectives of the Central Oklahoma aquifer assessment are: (1) To investigate regional ground-water quality throughout the aquifer in the manner consistent with the other pilot ground-water projects, emphasizing the occurrence and distribution of potentially toxic substances in ground water, including trace elements, organic compounds, and radioactive constituents; (2) to describe relations between ground-water quality, land use, hydrogeology, and other pertinent factors; and (3) to provide a general description of the location, nature, and possible causes of selected prevalent water-quality problems within the study unit; and (4) to describe the potential for water-quality degradation of ground-water zones within the study unit. The Central Oklahoma aquifer, which includes in descending order the Garber Sandstone and Wellington Formation, the Chase Group, the Council Grove Group, the Admire Group, and overlying alluvium and terrace deposits, underlies about 3,000 square miles of central Oklahoma and is used extensively for municipal, industrial, commercial, and domestic water supplies. The aquifer was selected for study by the NAWQA program because it is a major source for water supplies in central Oklahoma and because it has several known or suspected water-quality problems. Known problems include concentrations of arsenic, chromium, selenium, and gross-alpha activity that exceed drinking-water standards. Suspected problems include possible contamination of the aquifer by oil-field brines and drilling fluids, pesticides, industrial chemicals, septic-tank effluent, fertilizers, and leakage from sewage systems and underground tanks used for storage of hydrocarbons. There are four major components of the Central Oklahoma aquifer project. The first component is the collection and analysis of existing information, including chemical, hydrologic, and land-use data. The second component is the geohydrologic and geochemical investigations of the aquifer flow system. The third component is the sampling for a wide variety of inorganic, organic, and radioactive constituents as part a regional survey that will produce a consistent set of data among all ground-water pilot projects. These data can be used to: (1) Define regional ground-water quality within the Central Oklahoma aquifer, and (2) compare water quality in the Central Oklahoma aquifer to the water quality in the other ground-water study units of the NAWQA program. The fourth component is topical studies that will address, in more detail, some of the major water-quality issues pertaining to the aquifer.

Groundwater and climate change: mitigating the global groundwater crisis and adapting to climate change model

USDA-ARS?s Scientific Manuscript database

To better understand the effects of climate change on global groundwater resources, the United Nations Educational, Scientific, and Cultural Organization (UNESCO) International Hydrological Programme (IHP) initiated the GRAPHIC (Groundwater Resources Assessment under the Pressures of Humanity and Cl...

The Use of Hydrograph Analysis and Impulse Response Functions to Improve Understanding of Groundwater Flooding: A Case Study from the Chalk Aquifer, United Kingdom.

NASA Astrophysics Data System (ADS)

Ascott, M.; Bloomfield, J.; Macdonald, D.; Marchant, B.; McKenzie, A.

2017-12-01

The Cretaceous Chalk, the most important aquifer in the United Kingdom (UK) for public water supply, underlies many large cities in southern and eastern England including parts of London, however, it is prone to groundwater flooding. We have developed a new approach to analyse the spatio-temporal extent of groundwater flooding using statistical analysis of groundwater level hydrographs and impulse response functions (IRFs) applied to a major Chalk groundwater flooding event in the UK during winter 2013/14. Using monthly groundwater levels for 26 boreholes in the Chalk and a new standardised index for groundwater flooding, we have: estimated standardised series; grouped them using k-means cluster analysis; and, cross-correlated the cluster centroids with the Standardised Precipitation Index accumulated over time intervals between 1 and 60 months. This analysis reveals two spatially coherent groups of standardised hydrographs which respond to precipitation over different timescales. We estimate IRF models of the groundwater level response to effective precipitation for three boreholes in each group. The IRF models support the SPI analysis showing different response functions between the two groups. If we apply identical effective precipitation inputs to each of the IRF models we see differences between the hydrographs from each group. It is proposed that these differences are due to the intrinsic, hydrogeological properties of the Chalk and of overlying relatively low permeability superficial deposits. Consequently, it is concluded that the overarching controls on groundwater flood response are a complex combination of antecedent conditions, rainfall and catchment hydrogeological properties. These controls should be taken into consideration when anticipating and managing future groundwater flood events.

Geologic map of the Mound Spring quadrangle, Nye and Clark Counties, Nevada, and Inyo County, California

USGS Publications Warehouse

Lundstrom, Scott C.; Mahan, Shannon; Blakely, Richard J.; Paces, James B.; Young, Owen D.; Workman, Jeremiah B.; Dixon, Gary L.

2003-01-01

The Mound Spring quadrangle, the southwestern-most 7.5' quadrangle of the area of the Las Vegas 1:100,000-scale quadrangle, is entirely within the Pahrump Valley, spanning the Nevada/California State line. New geologic mapping of the predominantly Quaternary materials is combined with new studies of gravity and geochronology in this quadrangle. Eleven predominantly fine-grained units are delineated, including playa sediment, dune sand, and deposits associated with several cycles of past groundwater discharge and distal fan sedimentation. These units are intercalated with 5 predominantly coarse-grained alluvial-fan and wash gravel units mainly derived from the Spring Mountains. The gravel units are distinguished on the basis of soil development and associated surficial characteristics. Thermoluminescence and U-series geochronology constrain most of the units to the Holocene and late and middle Pleistocene. Deposits of late Pleistocene groundwater discharge in the northeast part of the quadrangle are associated with a down-to-the-southwest fault zone that is expressed by surface fault scarps and a steep gravity gradient. The gravity field also defines a northwest-trending uplift along the State line, in which the oldest sediments are poorly exposed. About 2 km to the northeast a prominent southwest-facing erosional escarpment is formed by resistant beds in middle Pleistocene fine-grained sediments that dip northeast away from the uplift. These sediments include cycles of groundwater discharge that were probably caused by upwelling of southwesterly groundwater flow that encountered the horst.

California GAMA program: ground-water quality data in the San Diego drainages hydrogeologic province, California, 2004

USGS Publications Warehouse

Wright, Michael T.; Belitz, Kenneth; Burton, Carmen A.

2005-01-01

Because of concerns over ground-water quality, the California State Water Resources Control Board (SWRCB), in collaboration with the U.S. Geological Survey and Lawrence Livermore National Laboratory, has implemented the Ground-Water Ambient Monitoring and Assessment (GAMA) Program. A primary objective of the program is to provide a current assessment of ground-water quality in areas where public supply wells are an important source of drinking water. The San Diego GAMA study unit was the first region of the state where an assessment of ground-water quality was implemented under the GAMA program. The San Diego GAMA study unit covers the entire San Diego Drainages hydrogeologic province, and is broken down into four distinct hydrogeologic study areas: the Temecula Valley study area, the Warner Valley study area, the Alluvial Basins study area, and the Hard Rock study area. A total of 58 ground-water samples were collected from public supply wells in the San Diego GAMA study unit: 19 wells were sampled in the Temecula Valley study area, 9 in the Warner Valley study area, 17 in the Alluvial Basins study area, and 13 in the Hard Rock study area. Over 350 chemical and microbial constituents and water-quality indicators were analyzed for in this study. However, only select wells were measured for all constituents and water-quality indicators. Results of analyses were calculated as detection frequencies by constituent classification and by individual constituents for the entire San Diego GAMA study unit and for the individual study areas. Additionally, concentrations of constituents that are routinely monitored were compared to maximum contaminant levels (MCL) and secondary maximum contaminant levels (SMCL). Concentrations of constituents classified as 'unregulated chemicals for which monitoring is required' (UCMR) were compared to the 'detection level for the purposes of reporting' (DLR). Eighteen of the 88 volatile organic compounds (VOCs) and gasoline oxygenates analyzed for were detected in ground-water samples. Twenty-eight wells sampled in the San Diego GAMA study had at least a single detection of VOCs or gasoline oxygenates. These constituents were most frequently detected in the Alluvial Basin study area (11 of 17 wells), and least frequently detected in the Warner Valley study area (one of nine wells). Trihalomethanes (THMs) were the most frequently detected class of VOCs (18 of 58 wells). The most frequently detected VOCs were chloroform (18 of 58 wells), bromodichloromethane (8 of 58 wells), and methyl tert-butyl ether (MTBE) (7 of 58 wells). Three VOCs were detected at concentrations greater than their MCLs. Tetrachloroethylene (PCE) and trichloroethylene (TCE) were detected in one well in the Hard Rock study area at concentrations of 9.75 and 7.27 micrograms per liter (?g/L), respectively; the MCL for these compounds is 5 ?g/L. MTBE was detected in one well in the Alluvial Basins study area at a concentration of 28.3 ?g/L; the MCL for MTBE is 13 ?g/L. Twenty-one of the 122 pesticides and pesticide degradates analyzed for were detected in ground-water samples. Pesticide or pesticide degradates were detected in 33 of 58 wells sampled, and were most frequently detected in the Temecula Valley study area wells (9 of 14 wells), and least frequently in the Warner Valley study area wells (3 of 9 wells). Herbicides were the most frequently detected class of pesticides (31 of 58 wells), and simazine was the most frequently detected compound (27 of 58 wells), followed by deethylatrazine (14 of 58 wells), prometon (10 of 58 wells), and atrazine (9 of 58 wells). None of the pesticides detected in ground-water samples had concentrations that exceeded MCLs. Eight waste-water indicator compounds were detected in ground-water samples. Twenty-one of 47 wells sampled for waste-water indicator compounds had at least a single detection. Waste-water indicator compounds were detected most frequently in the Allu

Hydrogeology and groundwater quality of Highlands County, Florida

USGS Publications Warehouse

Spechler, Rick M.

2010-01-01

Groundwater is the main source of water supply in Highlands County, Florida. As the demand for water in the county increases, additional information about local groundwater resources is needed to manage and develop the water supply effectively. To address the need for additional data, a study was conducted to evaluate the hydrogeology and groundwater quality of Highlands County. Total groundwater use in Highlands County has increased steadily since 1965. Total groundwater withdrawals increased from about 37 million gallons per day in 1965 to about 107 million gallons per day in 2005. Much of this increase in water use is related to agricultural activities, especially citrus cultivation, which increased more than 300 percent from 1965 to 2005. Highlands County is underlain by three principal hydrogeologic units. The uppermost water-bearing unit is the surficial aquifer, which is underlain by the intermediate aquifer system/intermediate confining unit. The lowermost hydrogeologic unit is the Floridan aquifer system, which consists of the Upper Floridan aquifer, as many as three middle confining units, and the Lower Floridan aquifer. The surficial aquifer consists primarily of fine-to-medium grained quartz sand with varying amounts of clay and silt. The aquifer system is unconfined and underlies the entire county. The thickness of the surficial aquifer is highly variable, ranging from less than 50 to more than 300 feet. Groundwater in the surficial aquifer is recharged primarily by precipitation, but also by septic tanks, irrigation from wells, seepage from lakes and streams, and the lateral groundwater inflow from adjacent areas. The intermediate aquifer system/intermediate confining unit acts as a confining layer (except where breached by sinkholes) that restricts the vertical movement of water between the surficial aquifer and the underlying Upper Floridan aquifer. The sediments have varying degrees of permeability and consist of permeable limestone, dolostone, or sand, or relatively impermeable layers of clay, clayey sand, or clayey carbonates. The thickness of the intermediate aquifer system/ intermediate confining unit ranges from about 200 feet in northwestern Highlands County to more than 600 feet in the southwestern part. Although the intermediate aquifer system is present in the county, it is unclear where the aquifer system grades into a confining unit in the eastern part of the county. Up to two water-bearing units are present in the intermediate aquifer system within the county. The lateral continuity and water-bearing potential of the various aquifers within the intermediate aquifer system are highly variable. The Floridan aquifer system is composed of a thick sequence of limestone and dolostone of Upper Paleocene to Oligocene age. The top of the aquifer system ranges from less than 200 feet below NGVD 29 in extreme northwestern Highlands County to more than 600 feet below NGVD 29 in the southwestern part. The principal source of groundwater supply in the county is the Upper Floridan aquifer. As of 2005, about 89 percent of the groundwater withdrawn from the county was obtained from this aquifer, mostly for agricultural irrigation and public supply. Over most of Highlands County, the Upper Floridan aquifer generally contains freshwater, and the Lower Floridan aquifer contains more mineralized water. The potentiometric surface of the Upper Floridan aquifer is constantly fluctuating, mainly in response to seasonal variations in rainfall and groundwater withdrawals. The potentiometric surface of the Upper Floridan aquifer in May 2007, which represents the hydrologic conditions near the end of the dry season when water levels generally are near their lowest, ranged from about 79 feet above NGVD 29 in northwestern Highlands County to about 40 feet above NGVD 29 in the southeastern part of the county. The potentiometric surface of the Upper Floridan aquifer in September 2007 was about 3 to 10 feet high

Superfund record of decision (EPA Region 4): Marine Corps Base (site 35), operable unit 10, Camp Lejeune, NC, September 22, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-01-01

This decision document presents the selected remedy for surficial groundwater for a portion of Operable Unit (OU) No. 10 (Site 35), Marine Corps Base (MCB), Camp Lejeune, North Carolina. Five Remedial Action Alternatives (RAAs) were evaluated as part of an interim remedial investigation/feasibility study for surficial groundwater at OU No. 10 (Site 35). These RAAs included RAA 1 (No Action), RAA 2 (No Action With Institutional Controls), RAA 3 (Groundwater Collection and On-site Treatment), RAA 4 (In Situ Air Sparging and Off-Gas Carbon Adsorption) and RAA 5 (In Well Aeration and Off-Gas Adsorption). After all five RAAs were compared tomore » established criteria, RAA 5 was selected as the preferred alternative.« less

Ground-water monitoring in the Albuquerque area

USGS Publications Warehouse

Thorn, Condé R.

1996-01-01

At present (1996), all drinking water for Albuquerque residents comes from ground-water reserves. The Albuquerque area is the largest population center in the State and the largest consumer of ground water. Recent reports concerning the water resources of the Albuquerque area suggest that the Albuquerque Basin may soon face serious water-availability and water-quality problems due to anticipated ground-water development. Recent studies completed by the U.S. Geological Survey (USGS) have improved the understanding of the ground-water resources in the Albuquerque Basin. These studies have indicated that the more permeable units within the aquifer system--the upper Santa Fe Group--are less extensive than previously thought, and that water-levels have declined as much as 160 feet.

Satellites measure recent rates of groundwater depletion in California's Central Valley

NASA Astrophysics Data System (ADS)

Famiglietti, J. S.; Lo, M.; Ho, S. L.; Bethune, J.; Anderson, K. J.; Syed, T. H.; Swenson, S. C.; de Linage, C. R.; Rodell, M.

2011-02-01

In highly-productive agricultural areas such as California's Central Valley, where groundwater often supplies the bulk of the water required for irrigation, quantifying rates of groundwater depletion remains a challenge owing to a lack of monitoring infrastructure and the absence of water use reporting requirements. Here we use 78 months (October, 2003-March, 2010) of data from the Gravity Recovery and Climate Experiment satellite mission to estimate water storage changes in California's Sacramento and San Joaquin River Basins. We find that the basins are losing water at a rate of 31.0 ± 2.7 mm yr-1 equivalent water height, equal to a volume of 30.9 km3 for the study period, or nearly the capacity of Lake Mead, the largest reservoir in the United States. We use additional observations and hydrological model information to determine that the majority of these losses are due to groundwater depletion in the Central Valley. Our results show that the Central Valley lost 20.4 ± 3.9 mm yr-1 of groundwater during the 78-month period, or 20.3 km3 in volume. Continued groundwater depletion at this rate may well be unsustainable, with potentially dire consequences for the economic and food security of the United States.

Hydrogeologic setting, water budget, and preliminary analysis of ground-water exchange at Lake Starr, a seepage lake in Polk County, Florida

USGS Publications Warehouse

Swancar, Amy; Lee, T.M.; O'Hare, T. M.

2000-01-01

Lake Starr, a 134-acre seepage lake of multiple-sinkhole origin on the Lake Wales Ridge of central Florida, was the subject of a detailed water-budget study from August 1996 through July 1998. The study monitored the effects of hydrogeologic setting, climate, and ground-water pumping on the water budget and lake stage. The hydrogeologic setting of the Lake Starr basin differs markedly on the two sides of the lake. Ground water from the surficial aquifer system flows into the lake from the northwest side of the basin, and lake water leaks out to the surficial aquifer system on the southeast side of the basin. Lake Starr and the surrounding surficial aquifer system recharge the underlying Upper Floridan aquifer. The rate of recharge to the Upper Floridan aquifer is determined by the integrity of the intermediate confining unit and by the downward head gradient between the two aquifers. On the inflow side of the lake, the intermediate confining unit is more continuous, allowing ground water from the surficial aquifer system to flow laterally into the lake. Beneath the lake and on the southeast side of the basin, breaches in the intermediate confining unit enhance downward flow to the Upper Floridan aquifer, so that water flows both downward and laterally away from the lake through the ground-water flow system in these areas. An accurate water budget, including evaporation measured by the energy-budget method, was used to calculate net ground-water flow to the lake, and to do a preliminary analysis of the relation of net ground-water fluxes to other variables. Water budgets constructed over different timeframes provided insight on processes that affect ground-water interactions with Lake Starr. Weekly estimates of net ground-water flow provided evidence for the occurrence of transient inflows from the nearshore basin, as well as the short-term effects of head in the Upper Floridan aquifer on ground-water exchange with the lake. Monthly water budgets showed the effects of wet and dry seasons, and provided evidence for ground-water inflow generated from the upper basin. Annual water budgets showed how differences in timing of rainfall and pumping stresses affected lake stage and lake ground-water interactions. Lake evaporation measurements made during the study suggest that, on average, annual lake evaporation exceeds annual precipitation in the basin. Rainfall was close to the long-term average of 51.99 inches per year for the 2 years of the study (50.68 and 54.04 inches, respectively). Lake evaporation was 57.08 and 55.88 inches per year for the same 2 years, making net precipitation (rainfall minus evaporation) negative during both years. If net precipitation to seepage lakes in this area is negative over the long-term, then the ability to generate net ground-water inflow from the surrounding basin plays an important role in sustaining lake levels. Evaporation exceeded rainfall by a similar amount for both years of the study, but net ground-water flow differed substantially between the 2 years. The basin contributed net ground-water inflow to the lake in both years, however, net ground-water inflow was not sufficient to make up for the negative net precipitation during the first year, and the lake fell 4.9 inches. During the second year, net ground-water inflow exceeded the difference between evaporation and rainfall and the lake rose by 12.7 inches. The additional net ground-water inflow in the second year was due to both an increase in the amount of gross ground-water inflow and a decrease in lake leakage (ground-water outflow). Ground-water inflow was greater during the second year because more rain fell during the winter, when evaporative losses were low, resulting in greater ground-water recharge. However, decreased lake leakage during this year was probably at least as important as increased ground-water inflow in explaining the difference in net ground-water flow to the lake between the 2 years. Estimates of lake leakage

Role of surface-water and groundwater interactions on projected summertime streamflow in snow dominated regions : An integrated modeling approach

USGS Publications Warehouse

Huntington, Justin L.; Niswonger, Richard G.

2012-01-01

Previous studies indicate predominantly increasing trends in precipitation across the Western United States, while at the same time, historical streamflow records indicate decreasing summertime streamflow and 25th percentile annual flows. These opposing trends could be viewed as paradoxical, given that several studies suggest that increased annual precipitation will equate to increased annual groundwater recharge, and therefore increased summertime flow. To gain insight on mechanisms behind these potential changes, we rely on a calibrated, integrated surface and groundwater model to simulate climate impacts on surface water/groundwater interactions using 12 general circulation model projections of temperature and precipitation from 2010 to 2100, and evaluate the interplay between snowmelt timing and other hydrologic variables, including streamflow, groundwater recharge, storage, groundwater discharge, and evapotranspiration. Hydrologic simulations show that the timing of peak groundwater discharge to the stream is inversely correlated to snowmelt runoff and groundwater recharge due to the bank storage effect and reversal of hydraulic gradients between the stream and underlying groundwater. That is, groundwater flow to streams peaks following the decrease in stream depth caused by snowmelt recession, and the shift in snowmelt causes a corresponding shift in groundwater discharge to streams. Our results show that groundwater discharge to streams is depleted during the summer due to earlier drainage of shallow aquifers adjacent to streams even if projected annual precipitation and groundwater recharge increases. These projected changes in surface water/groundwater interactions result in more than a 30% decrease in the projected ensemble summertime streamflow. Our findings clarify causality of observed decreasing summertime flow, highlight important aspects of potential climate change impacts on groundwater resources, and underscore the need for integrated hydrologic models in climate change studies.

Groundwater quality in the Monterey Bay and Salinas Valley groundwater basins, California

USGS Publications Warehouse

Kulongoski, Justin T.; Belitz, Kenneth

2011-01-01

The Monterey-Salinas study unit is nearly 1,000 square miles and consists of the Santa Cruz Purisima Formation Highlands, Felton Area, Scotts Valley, Soquel Valley, West Santa Cruz Terrace, Salinas Valley, Pajaro Valley, and Carmel Valley groundwater basins (California Department of Water Resources, 2003; Kulongski and Belitz, 2011). These basins were grouped into four study areas based primarily on geography. Groundwater basins in the north were grouped into the Santa Cruz study area, and those to the south were grouped into the Monterey Bay, the Salinas Valley, and the Paso Robles study areas (Kulongoski and others, 2007). The study unit has warm, dry summers and cool, moist winters. Average annual rainfall ranges from 31 inches in Santa Cruz in the north to 13 inches in Paso Robles in the south. The study areas are drained by several rivers and their principal tributaries: the Salinas, Pajaro, and Carmel Rivers, and San Lorenzo Creek. The Salinas Valley is a large intermontane valley that extends southeastward from Monterey Bay to Paso Robles. It has been filled, up to a thickness of 2,000 feet, with Tertiary and Quaternary marine and terrestrial sediments that overlie granitic basement. The Miocene-age Monterey Formation and Pliocene- to Pleistocene-age Paso Robles Formation, and Pleistocene to Holocene-age alluvium contain freshwater used for supply. The primary aquifers in the study unit are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells are typically drilled to depths of 200 to 650 feet, consist of solid casing from the land surface to depths of about 175 to 500 feet, and are perforated below the solid casing. Water quality in the primary aquifers may differ from that in the shallower and deeper parts of the aquifer system. Groundwater movement is generally from the southern part of the Salinas Valley north towards the Monterey Bay. Land use in the study unit is about 44 percent (%) natural (mostly grassland and forests), 43% agricultural, and 13% urban. The primary agricultural uses are row crops, pasture, hay, and vineyards. The largest urban areas are the cities of Santa Cruz, Watsonville, Monterey, Salinas, King City, and Paso Robles. Recharge to the groundwater system is primarily from stream-channel infiltration from the major rivers and their tributaries, and from infiltration of water from precipitation and irrigation. The primary sources of discharge are water pumped for irrigation and municipal supply, evaporation, and discharge to streams.

Determination of fluoride source in ground water using petrographic studies in Dashtestan area, south of Iran

NASA Astrophysics Data System (ADS)

Battaleb-Looie, Sedigheh; Moore, Farid, ,, Dr.

2010-05-01

The groundwater occurs in Dashtestan area, contains a high level of fluoride. Since groundwater is vastly used for drinking and irrigation purposes, the local residents are at high risk of fluoride toxicity, as already evidenced by the occurrence of dental Fluorosis in many residents. 35 surface and groundwater samples were collected in September, 2009. The results show that in 23 samples the fluoride concentration is above the permissible level (1.5ppm). Petrographic study of lithological units in the catchment area indicates that mica minerals are the most probable source of fluoride content in the study area.

Superfund record of decision amendment (EPA Region 5): Ninth Avenue Dump, Gary, IN, September 13, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The decision document, together with Records of Decision dated June 30, 1989 (PB90-114810) and September 20, 1988 (PB89-153837) and an Explanation of Significant Differences dated October 1991, present the selected remedial action for the Ninth Avenue Dump site. The remedial action for the site consists of two operable units. The first operable unit addressed an oil layer floating on the groundwater by means of oil and groundwater extraction, oil storage, reintroduction of the groundwater, containment with a slurry wall, and management of excess surface water. The extracted groundwater was treated prior to reintroduction. The second operable unit, which is beingmore » amended by this decision document, addresses the remaining threats at the site.« less

Field Evaluation Of Arsenic Transport Across The Ground-Water/Surface Water Interface: Ground-Water Discharge And Iron Oxide Precipitation

EPA Science Inventory

A field investigation was conducted to examine the distribution of arsenic in ground water, surface water, and sediments at a Superfund Site in the northeastern United States (see companion presentation by K. G. Scheckel et al). Ground-water discharge into the study area was cha...

Understanding and managing the effects of groundwater pumping on streamflow

USGS Publications Warehouse

Leake, Stanley A.; Barlow, Paul M.

2013-01-01

Groundwater is a critical resource in the United States because it provides drinking water, irrigates crops, supports industry, and is a source of water for rivers, streams, lakes, and springs. Wells that pump water out of aquifers can reduce the amount of groundwater that flows into rivers and streams, which can have detrimental impacts on aquatic ecosystems and the availability of surface water. Estimation of rates, locations, and timing of streamflow depletion due to groundwater pumping is needed for water-resource managers and users throughout the United States, but the complexity of groundwater and surface-water systems and their interactions presents a major challenge. The understanding of streamflow depletion and evaluation of water-management practices have improved during recent years through the use of computer models that simulate aquifer conditions and the effects of pumping groundwater on streams.

Status and understanding of groundwater quality in the South Coast Interior groundwater basins, 2008: California GAMA Priority Basin Project

USGS Publications Warehouse

Parsons, Mary C.; Kulongoski, Justin T.; Belitz, Kenneth

2014-01-01

Groundwater quality in the approximately 653-square-mile (1,691-square-kilometer) South Coast Interior Basins (SCI) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The South Coast Interior Basins study unit contains eight priority groundwater basins grouped into three study areas, Livermore, Gilroy, and Cuyama, in the Southern Coast Ranges hydrogeologic province. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA South Coast Interior Basins study was designed to provide a spatially unbiased assessment of untreated (raw) groundwater quality within the primary aquifer system, as well as a statistically consistent basis for comparing water quality between basins. The assessment was based on water-quality and ancillary data collected by the USGS from 50 wells in 2008 and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system was defined by the depth intervals of the wells listed in the CDPH database for the SCI study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as trace elements and minor ions. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifer system of the SCI study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic constituents and special-interest constituents were classified as “high” (relative-concentration greater than 1.0), “moderate” (relative-concentration greater than 0.1 and less than or equal to 1.0), or “low” (relative-concentration less than or equal to 0.1). Relative-concentrations of inorganic constituents were classified as “high” (relative-concentration greater than 1.0), “moderate” (relative-concentration greater than 0.5 and less than or equal to 1.0), or “low” (relative-concentration less than or equal to 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the areal percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the SCI study unit (within 90-percent confidence intervals). Inorganic constituents (one or more) with health-based benchmarks were detected at high relative-concentrations in 29 percent of the primary aquifer system, at moderate relative-concentrations in 37 percent, and at low relative-concentrations in 34 percent. High aquifer-scale proportions of inorganic constituents primarily reflected high aquifer-scale proportions of nitrate (14 percent), boron (8.6 percent), molybdenum (8.6 percent), and arsenic (5.7 percent). In contrast, the relative-concentrations of organic constituents (one or more) were high in 1.6 percent, moderate in 2.0 percent, and low or not detected in 96 percent of the primary aquifer system. Of the 207 organic and special-interest constituents analyzed for, 15 constituents were detected. Perchlorate was found at moderate relative-concentrations in 34 percent of the aquifer. Two organic constituents were frequently detected (in greater than 10 percent of samples): the trihalomethane chloroform and the herbicide simazine. The second component of this study, the understanding assessment, identified natural and human factors that may have affected groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. This evaluation was done by using statistical tests of correlations between these potential explanatory factors and water-quality data. Concentrations of arsenic, molybdenum, and manganese were generally greater in anoxic and pre-modern groundwater than other groundwater. In contrast, concentrations of nitrate and perchlorate were significantly higher in oxic and modern groundwater. Concentrations of simazine were greater in modern than pre-modern groundwater. Chloroform detections were positively correlated with greater urban land use. Boron concentrations and chloroform detections were higher in the Livermore study area than in the other study areas of the SCI; total dissolved solids and sulfate concentrations were greater in the Cuyama study area.

Geohydrology and water chemistry in the Rialto-Colton Basin, San Bernardino County, California

USGS Publications Warehouse

Woolfenden, Linda R.; Kadhim, Dina

1997-01-01

The 40-square-mile Rialto-Colton ground- water basin is in western San Bernardino County, California, about 60 miles east of Los Angeles.This basin was chosen for storage of imported water because of the good quality of native ground water, the known capacity for additional ground-water storage in the basin, and the availability of imported water. Because the movement and mixing of imported water needed to be determined, the San Bernardino Valley Municipal Water District entered into a cooperative program with the U.S.Geological Survey in 1991 to study the geohydrology and water chemistry in the Rialto- Colton basin. Ground-water flow and chemistry were investigated using existing data, borehole- geophysical and lithologic logs from newly drilled test holes, measurement of water levels, and chemical analyses of water samples. The Rialto-Colton basin is bounded on the northwest and southeast by the San Gabriel Mountains and the Badlands, respectively. The San Jacinto Fault and Barrier E form the northeastern boundary, and the Rialto-Colton Fault forms the southwestern boundary. Except in the southeastern part of the basin, the San Jacinto and Rialto-Colton Faults act as groundwater barriers that impede ground- water flow into and out of the basin.Barrier E generally does not impede ground- water flow into the basin. The ground-water system consists primarily of gravel, sand, silt, and clay. The maximum thickness is greater than 1,000 feet. The ground- water system is divided into four water-bearing units: river-channel deposits, and upper, middle, and lower water-bearing units. Relatively impermeable consolidated deposits underlie the lower water- bearing unit and form the lower boundary of the ground- water system. Ground water moves from east to west in the river-channel deposits and upper water-bearing unit in the southeastern part of the basin, and from northwest to southeast in the middle and lower water-bearing units. Two major internal faults, Barrier J and an unnamed fault, affect ground-water movement. Ground water moves across Barrier J in the unfaulted part of the ground-water system. The unnamed fault is a partial barrier to ground-water movement in the middle water- bearing unit and an effective barrier in the lower water-bearing unit.Imported water flows laterally across the unnamed fault above the saturated zone. Major sources of recharge to the ground- water system are underflow; precipitation that collects in small streams that drain the San Gabriel Mountains and the Badlands or runs off the mountain front as sheet flow, and sub-surface inflow; imported water; seepage loss from the Santa Ana River and Warm Creek; infiltration of rainfall; and irrigation return flow. The main component of discharge is pumpage. Long-term water levels in production wells reflect precipitation cycles. During a 194777 dry period, water levels in three wells declined almost continuously?as much as 100 feet in one well.Water levels in a well north of Barrier J are not affected by stresses on the groundwater system south of the barrier, indicating that these two parts of the ground-water system are not well connected. Water levels in cluster wells east of the unnamed fault north and south of the Linden Ponds artificial-recharge site rose as much as 70 feet during 1992-95. The rise in water levels in wells near the recharge ponds was observed within 2 months after the beginning of recharge. Water levels in most wells west of the unnamed fault changed very little during 1992-95. Water-chemistry data indicate that chemical characteristics vary within the groundwater system, and that dissolvedsolids concentrations are generally higher in the river-channel deposits, upper water- bearing unit, and the consolidated deposits than in the middle and lower water-bearing units. The chemical characteristics in water from the middle water-bearing unit were similar for most wells sampled west of the unnamed fault. In water from well

Estimating discharge of shallow groundwater by transpiration from greasewood in the Northern Great Basin

USGS Publications Warehouse

Nichols, William D.

1993-01-01

Evapotranspiration from bare soil and phreatophytes is a principal mechanism of groundwater discharge in arid and semiarid regions of the midwestern and western United States including the Great Basin. The imbalance between independent estimates of groundwater recharge from precipitation and of groundwater discharge based on estimates of groundwater evapotranspiration leads to large uncertainties in groundwater budgets. Few studies have addressed this problem. Energy budget micrometeorological field studies were conducted in a stand of sparse-canopy greasewood growing in an area of shallow groundwater in the western Great Basin during the summer of 1989. The data were used to calculate above-canopy fluxes of sensible and latent heat using the energy budget-Bowen ratio method. The calculated energy budget fluxes were used, with soil surface and plant canopy temperature measurements, to calibrate and apply a two-component, energy-combination model that partitions the energy and heat fluxes between bare soil and the canopy. This permitted the separation of evaporation from the soil and transpiration from greasewood. The calibrated model was used to estimate daily transpiration of groundwater by greasewood growing in an area with a depth to water of about 2 m. The daily rate of groundwater discharge by transpiration during July and August was estimated to be 2.4 mm. A period of 100 days for groundwater discharge at this rate was assumed to estimate an annual discharge of groundwater of 24 cm at the study site.

40 CFR 264.97 - General ground-water monitoring requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... collection of ground-water samples. The annular space (i.e., the space between the bore hole and well casing... 40 Protection of Environment 27 2013-07-01 2013-07-01 false General ground-water monitoring... FACILITIES Releases From Solid Waste Management Units § 264.97 General ground-water monitoring requirements...

Groundwater: Illinois' Buried Treasure. Education Activity Guide.

ERIC Educational Resources Information Center

Environmental Education Association of Illinois, Chicago.

Groundwater is an extremely valuable resource that many feel has been too long neglected and taken for granted. There is growing recognition in Illinois and throughout the United States that comprehensive groundwater protection measures are vital. Illinois embarked on a course in protecting groundwater resources with the passage of the Illinois…

Hydrogeologic framework and groundwater/surface-water interactions of the South Fork Nooksack River Basin, northwestern Washington

USGS Publications Warehouse

Gendaszek, Andrew S.

2014-01-01

A hydrogeologic framework of the South Fork (SF) Nooksack River Basin in northwestern Washington was developed and hydrologic data were collected to characterize the groundwater-flow system and its interaction with surface‑water features. In addition to domestic, agricultural, and commercial uses of groundwater within the SF Nooksack River Basin, groundwater has the potential to provide ecological benefits by maintaining late-summer streamflows and buffering stream temperatures. Cold-water refugia, created and maintained in part by groundwater, have been identified by water-resource managers as key elements to restore the health and viability of threatened salmonids in the SF Nooksack River. The SF Nooksack River drains a 183-square mile area of the North Cascades and the Puget Lowland underlain by unconsolidated glacial and alluvial sediments deposited over older sedimentary, metamorphic, and igneous bedrock. The primary aquifer that interacts with the SF Nooksack River was mapped within unconsolidated glacial outwash and alluvial sediment. The lower extent of this unit is bounded by bedrock and fine-grained, poorly sorted unconsolidated glaciomarine and glaciolacustrine sediments. In places, these deposits overlie and confine an aquifer within older glacial sediments. The extent and thickness of the hydrogeologic units were assembled from mapped geologic units and lithostratigraphic logs of field-inventoried wells. Generalized groundwater-flow directions within the surficial aquifer were interpreted from groundwater levels measured in August 2012; and groundwater seepage gains and losses to the SF Nooksack River were calculated from synoptic streamflow measurements made in the SF Nooksack River and its tributaries in September 2012. A subset of the field-inventoried wells was measured at a monthly interval to determine seasonal fluctuations in groundwater levels during water year 2013. Taken together, these data provide the foundation for a future groundwater-flow model of the SF Nooksack River Basin that may be used to investigate the potential effects of future climate change, land use, and groundwater pumping on water resources in the study area. Site-specific hydrologic data, including time series of longitudinal temperature profiles measured with a fiber-optic distributed temperature sensor and continuous monitoring of stream stage and water levels measured in wells in adjacent wetlands and aquifers, also were measured to characterize the interaction among the SF Nooksack River, surficial aquifers, and riparian wetlands.

Occurrence and availability of ground water in the Athens region, northeastern Georgia

USGS Publications Warehouse

Radtke, D.B.; Cressler, C.W.; Perlman, H.A.; Blanchard, H.E.; McFadden, K.W.; Brooks, Rebekah

1986-01-01

A study was conducted to assess the occurrence and availability of groundwater in the crystalline rocks of the Piedmont area in northeastern Georgia and to determine whether groundwater is a viable alternative or supplemental source for industrial, public and private supplies. The area is underlain by a variety of metamorphic and igneous rocks. The quantity of water that a rock unit can supply to wells is determined by the number, capacity, and interconnection of the secondary openings. Of an estimated 10,000 successful wells drilled in the Athens Region, 972 wells are reported by drilling contractors to supply from 20 to 300 gal/min. Studies of well sites revealed that high yielding wells can be developed only where the water bearing units have undergone significant increases in secondary permeability. This occurs mainly in association with (1) contact zones between rock units of contrasting character, (2) contact zones within multilayered rock units, (3) fault zones, (4) stress-relief fractures, and (5) shear zones. Groundwater may be a viable alternative or supplemental source for industrial, public, and private supplies in much of the Athens Region. In 1980, groundwater made up 38% (18 million gal/day) of the total water used in the area. Yields of 20 to more than 200 gal/min are obtained from wells throughout most of the region, and the water is generally of good chemical quality and is suitable for drinking and many other uses. Concentrations of dissolved constituents are fairly consistent throughout the area. Except for iron, manganese, and fluoride, dissolved constituents rarely exceed drinking water standards. (Lantz-PTT)

Status and understanding of groundwater quality in the Madera, Chowchilla Study Unit, 2008: California GAMA Priority Basin Project

USGS Publications Warehouse

Shelton, Jennifer L.; Fram, Miranda S.; Belitz, Kenneth; Jurgens, Bryant C.

2013-01-01

Groundwater quality in the approximately 860-square-mile Madera and Chowchilla Subbasins (Madera-Chowchilla study unit) of the San Joaquin Valley Basin was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in California's Central Valley region in parts of Madera, Merced, and Fresno Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The Project was designed to provide statistically robust assessments of untreated groundwater quality within the primary aquifer systems in California. The primary aquifer system within each study unit is defined by the depth of the perforated or open intervals of the wells listed in the California Department of Public Health (CDPH) database of wells used for municipal and community drinking-water supply. The quality of groundwater in shallower or deeper water-bearing zones may differ from that in the primary aquifer system; shallower groundwater may be more vulnerable to contamination from the surface. The assessments for the Madera-Chowchilla study unit were based on water-quality and ancillary data collected by the USGS from 35 wells during April-May 2008 and water-quality data reported in the CDPH database. Two types of assessments were made: (1) status, assessment of the current quality of the groundwater resource, and (2) understanding, identification of natural factors and human activities affecting groundwater quality. The primary aquifer system is represented by the grid wells, of which 90 percent (%) had depths that ranged from about 200 to 800 feet (ft) below land surface and had depths to the top of perforations that ranged from about 140 to 400 ft below land surface. Relative-concentrations (sample concentrations divided by benchmark concentrations) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration (RC) greater than 1.0 indicates a concentration above a benchmark. RCs for organic constituents (volatile organic compounds and pesticides) and special-interest constituents (perchlorate) were classified as "high" (RC is greater than 1.0), "moderate" (RC is less than or equal to 1.0 and greater than 0.1), or "low" (RC is less than or equal to 0.1). For inorganic constituents (major and minor ions, trace elements, nutrients, and radioactive constituents), the boundary between low and moderate RCs was set at 0.5. The assessments characterize untreated groundwater quality, not the quality of treated drinking water delivered to consumers by water purveyors; drinking-water benchmarks, and thus relative-concentrations, are used to provide context for the concentrations of constituents measured in groundwater. Aquifer-scale proportion was used in the status assessment as the primary metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with RCs greater than 1.0 for a particular constituent or class of constituents; moderate and low aquifer-scale proportions are defined as the percentages of the area of the primary aquifer system with moderate and low RCs, respectively. Percentages are based on an areal, rather than a volumetric basis. Two statistical approaches--grid-based, which used one value per grid cell, and spatially weighted, which used multiple values per grid cell--were used to calculate aquifer-scale proportions for individual constituents and classes of constituents. The spatially weighted estimates of high aquifer-scale proportions were within the 90% confidence intervals of the grid-based estimates for all constituents except iron. The status assessment showed that inorganic constituents had greater high and moderate aquifer-scale proportions in the Madera-Chowchilla study unit than did organic constituents. RCs for inorganic constituents with health-based benchmarks were high in 37% of the primary aquifer system, moderate in 30%, and low in 33%. The inorganic constituents contributing most to the high aquifer-scale proportion were arsenic (13%), uranium (17%), gross alpha particle activity (20%), nitrate (6.7%), and vanadium (3.3%). RCs for inorganic constituents with non-health-based benchmarks were high in 6.7% of the primary aquifer system, and the constituent contributing most to the high aquifer-scale proportion was total dissolved solids (TDS). RCs for organic constituents with health-based benchmarks were high in 10% of the primary aquifer system, moderate in 3.3%, and low in 40%; organic constituents were not detected in 47% of the primary aquifer system. The fumigant 1,2-dibromo-3-chloropropane (DBCP) was the only organic constituent detected at high RCs. Seven organic constituents were detected in 10% or more of the primary aquifer system: DBCP; the fumigant additive 1,2,3-trichloropropane; the herbicides simazine, atrazine, and diuron; the trihalomethane chloroform; and the solvent tetrachloroethene (PCE). RCs for the special-interest constituent perchlorate were moderate in 20% of the primary aquifer system. The second component of this study, the understanding assessment, identified the natural and human factors that may affect groundwater quality by evaluating statistical correlations between water-quality constituents and potential explanatory factors, such as land use, position relative to important geologic features, groundwater age, well depth, and geochemical conditions in the aquifer. Results of the statistical evaluations were used to explain the distribution of constituents in the study unit. Depth to the top of perforations in the well and groundwater age were the most important explanatory factors for many constituents. High and moderate RCs of nitrate, uranium, and TDS and the presence of herbicides, trihalomethanes, and solvents were all associated with depths to the top of perforations less than 235 ft and modern- and mixed-age groundwater. Positive correlations between uranium, bicarbonate, TDS, and the proportion of calcium and magnesium in the total cations suggest that downward movement of recharge from irrigation water contributed to the elevated concentrations of these constituents in the primary aquifer system. High and moderate RCs of arsenic were associated with depths to the top of perforations greater than 235 ft, mixed- and pre-modern-age groundwater, and location in sediments from the Chowchilla River alluvial fan, suggesting that increased residence time and appropriate aquifer materials were needed for arsenic to accumulate in the groundwater. High and moderate RCs of fumigants were associated with depths to the top of perforations of less than 235 ft and location south of the city of Madera; low RCs of fumigants were detected in wells dispersed across the study unit with a range of depths to top of perforations.

Status and understanding of groundwater quality in the Bear Valley and Lake Arrowhead Watershed Study Unit, 2010: California GAMA Priority Basin Project

USGS Publications Warehouse

Mathany, Timothy; Burton, Carmen

2017-06-20

Groundwater quality in the 112-square-mile Bear Valley and Lake Arrowhead Watershed (BEAR) study unit was investigated as part of the Priority Basin Project (PBP) of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit comprises two study areas (Bear Valley and Lake Arrowhead Watershed) in southern California in San Bernardino County. The GAMA-PBP is conducted by the California State Water Resources Control Board (SWRCB) in cooperation with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory.The GAMA BEAR study was designed to provide a spatially balanced, robust assessment of the quality of untreated (raw) groundwater from the primary aquifer systems in the two study areas of the BEAR study unit. The assessment is based on water-quality collected by the USGS from 38 sites (27 grid and 11 understanding) during 2010 and on water-quality data from the SWRCB-Division of Drinking Water (DDW) database. The primary aquifer system is defined by springs and the perforation intervals of wells listed in the SWRCB-DDW water-quality database for the BEAR study unit.This study included two types of assessments: (1) a status assessment, which characterized the status of the quality of the groundwater resource as of 2010 by using data from samples analyzed for volatile organic compounds, pesticides, and naturally present inorganic constituents, such as major ions and trace elements, and (2) an understanding assessment, which evaluated the natural and human factors potentially affecting the groundwater quality. The assessments were intended to characterize the quality of groundwater resources in the primary aquifer system of the BEAR study unit, not the treated drinking water delivered to consumers. Bear Valley study area and the Lake Arrowhead Watershed study area were also compared statistically on the basis of water-quality results and factors potentially affecting the groundwater quality.Relative concentrations (RCs), which are sample concentration of a particular constituent divided by its associated health- or aesthetic-based benchmark concentrations, were used for evaluating the groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. An RC greater than 1.0 indicates a concentration greater than a benchmark. Organic (volatile organic compounds and pesticides) and special-interest (perchlorate) constituent RCs were classified as “high” (RC greater than 1.0), “moderate” (RC less than or equal to 1.0 and greater than 0.1), or “low” (RC less than or equal to 0.1). For inorganic (radioactive, trace element, major ion, and nutrient) constituents, the boundary between low and moderate RCs was set at 0.5.Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating groundwater quality at the study-unit scale or for its component areas. High aquifer-scale proportion was defined as the percentage of the area of the primary aquifer system with a RC greater than 1.0 for a particular constituent or class of constituents; the percentage is based on area rather than volume. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifer system with moderate and low RCs, respectively. A spatially weighted statistical approach was used to evaluate aquifer-scale proportions for individual constituents and classes of constituents.The status assessment for the Bear Valley study area found that inorganic constituents with health-based benchmarks were detected at high RCs in 9.0 percent of the primary aquifer system and at moderate RCs in 13 percent. The high RCs of inorganic constituents primarily reflected high aquifer-scale proportions of fluoride (in 5.4 percent of the primary aquifer system) and arsenic (3.6 percent). The RCs of organic constituents with health-based benchmarks were high in 1.0 percent of the primary aquifer system, moderate in 8.1 percent, and low in 70 percent. Organic constituents were detected in 79 percent of the primary aquifer system. Two groups of organic constituents and two individual organic constituents were detected at frequencies greater than 10 percent of samples from the USGS grid sites: trihalomethanes (THMs), solvents, methyl tert-butyl ether (MTBE), and simazine. The special-interest constituent perchlorate was detected in 93 percent of the primary aquifer system; it was detected at moderate RCs in 7.1 percent and at low RCs in 86 percent.The status assessment in the Lake Arrowhead Watershed study area showed that inorganic constituents with human-health benchmarks were detected at high RCs in 25 percent of the primary aquifer system and at moderate RCs in 41 percent. The high aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of radon‑222 (in 62 percent of the primary aquifer system) and uranium (26 percent). RCs of organic constituents with health-based benchmarks were moderate in 7.7 percent of the primary aquifer system and low in 46 percent. Organic constituents were detected in 54 percent of the primary aquifer system. The only organic constituents that were detected at frequencies greater than 10 percent of samples from the USGS grid sites were THMs. Perchlorate was detected in 62 percent of the primary aquifer system at uniformly low RCs.The second component of this study, the understanding assessment, identified the natural and human factors that could have affected the groundwater quality in the BEAR study unit by evaluating statistical correlations between water-quality constituents and potential explanatory factors. The potential explanatory factors evaluated were land use (including density of septic tanks and leaking or formerly leaking underground fuel tanks), site type, aquifer lithology, well construction (well depth and depth to the top-of-perforated interval), elevation, aridity index, groundwater-age distribution, and oxidation-reduction condition (including pH and dissolved oxygen concentration). Results of the statistical evaluations were used to explain the distribution of constituents in groundwater of the BEAR study unit.In the Bear Valley study area, high and moderate RCs of fluoride were found in sites known to be influenced by hydrothermic conditions or that had high concentrations of fluoride historically. The high RC of arsenic can likely be attributed to desorption of arsenic from aquifer sediments saturated in old groundwater with high pH under reducing conditions. The THMs were detected more frequently at USGS grid sites that were wells, part of a large urban water system, and surrounded by urban land use. Solvents, MTBE, and simazine were all detected more frequently at USGS grid sites that were wells with a greater urban percentage of surrounding land use and that accessed older groundwater than other USGS grid sites. Comparison between the observed and predicted detection frequencies of perchlorate at USGS grid sites indicated that anthropogenic sources could have contributed to low levels of perchlorate in the groundwater of the Bear Valley study area.In the Lake Arrowhead Watershed study area, high and moderate RCs of radon-222 and uranium can be attributed to older groundwater from the granitic fractured-rock primary aquifer system. Low RCs of THMs were detected at USGS grid sites that were wells and part of small water systems. The similarities between the observed and predicted detection frequencies of perchlorate in samples from USGS grid sites indicated that the source and distribution of perchlorate were most likely attributable to precipitation (rain and snow), with minimal, if any, contribution from anthropogenic sources.

Geomorphology and its implication in urban groundwater environment: case study from Mumbai, India

NASA Astrophysics Data System (ADS)

Rani, V. R.; Pandalai, H. S.; Sajinkumar, K. S.; Pradeepkumar, A. P.

2015-06-01

Landforms of Mumbai Island have been largely modified by the urban sprawl and the demand for groundwater will increase exponentially in the future. Quality and quantity of groundwater occurrence in island are highly influenced by the geomorphic units. As this metropolis receives heavy rainfall, the area rarely faces the issue of water scarcity, nevertheless, quality always remains a question. The landforms of Mumbai Island have been shaped by a combination of fluvial, denudational and marine processes. These landforms are categorized into two broad zones on the basis of its influence in groundwater occurrence. Denudational landforms are categorized as runoff zones whereas the other two are categorized as storage zones. This classification is on the basis of occurrence and storage of groundwater. Mumbai Island is exposed to frequent sea water incursion and groundwater quality has deteriorated. The varied hydrogeological conditions prevalent in this area prevent rapid infiltration. This combined with the overextraction of groundwater resources for agriculture and industry has caused serious concern about the continued availability of potable water. This study aims at validating the geomorphic classification of the landforms with hydrogeochemistry and borehole data and it proved that geomorphology corroborates with groundwater chemistry and subsurface geology.

Optimization Review: Lockwood Operable Unit 1 - Beall Source Area, Billings, Montana

EPA Pesticide Factsheets

The Lockwood Solvent Groundwater Plume Site (LSGPS) consists of two operable units (OUs) and is located on the outskirts of Billings, Montana in EPA Region 8. OU1 consists of contaminated soils and a chlorinated solvent groundwater plume associated with...

Impact of textile dyeing industries effluent on groundwater quality in Karur Amaravathi River basin, Tamil Nadu (India)--a field study.

PubMed

Rajamanickam, R; Nagan, S

2010-10-01

Karur is an industrial town located on the bank of river Amaravathi. There are 487 textile processing units in operation and discharge about 14610 kilo litres per day of treated effluent into the river. The groundwater quality in the downstream is deteriorated due to continuous discharge of effluent. In order to assess the present quality of groundwater, 13 open wells were identified in the river basin around Karur and samples were collected during pre-monsoon, post monsoon and summer, and analyzed for physico-chemical parameters. TDS, total alkalinity, total hardness, calcium, chlorides and sulphates exceeded the desirable limit. Amaravathi River water samples were also colleted at the upstream and downstream of Karur and the result shows the river is polluted. During summer season, there is no flow in the river and the river acts as a drainage for the effluent. Hence, there is severe impact on the groundwater quality in the downstream. The best option to protect the groundwater quality in the river basin is that the textile processing units should adopt zero liquid discharge (ZLD) system and completely recycle the treated effluent.

Two-dimensional direct-current resistivity survey to supplement borehole data in ground-water models of the former Blaine Naval Ammunition Depot, Hastings, Nebraska, September 2003

USGS Publications Warehouse

Kress, Wade H.; Ball, Lyndsay B.; Teeple, Andrew; Turco, Michael J.

2006-01-01

The former Blaine Naval Ammunition Depot located immediately southeast of Hastings, Nebraska, was an ammunition facility during World War II and the Korean Conflict. Waste-management practices during operation and decommissioning of the former Depot resulted in soil and ground-water contamination. Ground-water models have been used by the U.S. Army Corps of Engineers to provide information on the fate and transport of contaminants on the former Depot site. During September 2003, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, Kansas City District, conducted a pilot study to collect two-dimensional direct-current resistivity data on the site along six profiles near existing monitoring wells. The inversion results of field data from five of the six two-dimensional direct-current resistivity profiles display distinct electrical stratigraphy consistent with three resistivity units (low resistivity, high resistivity, and low resistivity). These three resistivity units correlate with rock-stratigraphic or hydrogeologic units described prior to this study. To interpret the resistivity profiles, additional data extending through the lower confining unit into the underlying Niobrara Formation could be used with the existing data to construct forward models for data analysis and interpretation.

Groundwater potential index in a crystalline terrain using remote sensing data

NASA Astrophysics Data System (ADS)

Subba Rao, N.

2006-08-01

Demand for groundwater for drinking, agricultural and industrial purposes has increased due to uncertainty in the surface water supply. Agriculture is the main occupation of the rural people in Guntur district, Andhra Pradesh, India. Development of groundwater in the district is very less, indicating a lot of scope for further development of groundwater resources. However, assessment of groundwater conditions, particularly in a crystalline terrain, is a complex task because of variations in weathering and fracturing zones from place to place. Systematic studies for evaluation of groundwater potential zones have been carried out in a crystalline terrain of the district. Information on soils, geological formations and groundwater conditions is collected during the hydrogeological survey. Topographical and drainage conditions are derived from the Survey of India topographical maps. Geomorphological units and associated landform features inferred and delineated from the Indian remote sensing satellite imagery (IRS ID LISS III FCC) are moderately buried pediplain (BPM), shallow buried pediplain (BPS), valley fills (VF), structural hill (SH), residual hills (RH), lineaments and land use/land cover. A groundwater potential index (GPI) is computed for relative evaluation of groundwater potential zones in the study area by integrating all the related factors of occurrence and movement of groundwater resources. Accordingly, the landforms, BPM, BPS, VF, SH and RH, of the area are categorized as very good groundwater potential zone, good to moderate groundwater potential zone, moderate to poor groundwater potential zone, poor to very poor groundwater potential zone and very poor groundwater potential zone, respectively, for development and utilization of both groundwater and surface water resources for eliminating water scarcity. This study could help to improve the agrarian economy for better living conditions of the rural people. Taking the total weight-score of the GPI into account, a generalized classification of groundwater potential zones is evaluated for a quick assessment of the occurrence of groundwater resources on regional scale.

Water Resources of the Ground-Water System in the Unconsolidated Deposits of the Colville River Watershed, Stevens County, Washington

USGS Publications Warehouse

Kahle, Sue C.; Longpre, Claire I.; Smith, Raymond R.; Sumioka, Steve S.; Watkins, Anni M.; Kresch, David L.

2003-01-01

A study of the water resources of the ground-water system in the unconsolidated deposits of the Colville River Watershed provided the Colville River Watershed Planning Team with an assessment of the hydrogeologic framework, preliminary determinations of how the shallow and deeper parts of the ground-water system interact with each other and the surface-water system, descriptions of water-quantity characteristics including water-use estimates and an estimated water budget for the watershed, and an assessment of further data needs. The 1,007-square-mile watershed, located in Stevens County in northeastern Washington, is closed to further surface-water appropriations throughout most of the basin during most seasons. The information provided by this study will assist local watershed planners in assessing the status of water resources within the Colville River Watershed (Water Resources Inventory Area 59). The hydrogeologic framework consists of glacial and alluvial deposits that overlie bedrock and are more than 700 feet thick in places. Twenty-six hydrogeologic sections were constructed, using a map of the surficial geology and drillers' logs for more than 350 wells. Seven hydrogeologic units were delineated: the Upper outwash aquifer, the Till confining unit, the Older outwash aquifer, the Colville Valley confining unit, the Lower aquifer, the Lower confining unit, and Bedrock. Synoptic stream discharge measurements made in September 2001 identified gaining and losing reaches over the unconsolidated valley deposits. During the September measurement period, the Colville River gained flow from the shallow ground-water system near its headwaters to the town of Valley and lost flow to the shallow ground-water system from Valley to Chewelah. Downstream from Chewelah, the river generally lost flow, but the amounts lost were small and within measurement error. Ground-water levels indicate that the Lower aquifer and the shallow ground-water system may act as fairly independent systems. The presence of flowing wells completed in the Lower aquifer indicates upward head gradients along much of the Colville Valley floor. Total surface- and ground-water withdrawals during 2001 were estimated to be 9,340 million gallons. Water use for 2001, as a percentage of the total, was 75.3 percent for irrigation, 16.3 percent for public supply, 6.5 percent for private wells, and about 1 percent each for industrial and livestock use. An approximate water budget for a typical year in the Colville River Watershed shows that 27 inches of precipitation are balanced by 4.2 inches of streamflow discharge from the basin, 0.3 inch of ground-water discharge from the basin, and 22.5 inches of evapotranspiration.

Hydrogeologic framework and occurrence, movement, and chemical characterization of groundwater in Dixie Valley, west-central Nevada

USGS Publications Warehouse

Huntington, Jena M.; Garcia, C. Amanda; Rosen, Michael R.

2014-01-01

Dixie Valley, a primarily undeveloped basin in west-central Nevada, is being considered for groundwater exportation. Proposed pumping would occur from the basin-fill aquifer. In response to proposed exportation, the U.S. Geological Survey, in cooperation with the Bureau of Reclamation and Churchill County, conducted a study to improve the understanding of groundwater resources in Dixie Valley. The objective of this report is to characterize the hydrogeologic framework, the occurrence and movement of groundwater, the general water quality of the basin-fill aquifer, and the potential mixing between basin-fill and geothermal aquifers in Dixie Valley. Various types of geologic, hydrologic, and geochemical data were compiled from previous studies and collected in support of this study. Hydrogeologic units in Dixie Valley were defined to characterize rocks and sediments with similar lithologies and hydraulic properties influencing groundwater flow. Hydraulic properties of the basin-fill deposits were characterized by transmissivity estimated from aquifer tests and specific-capacity tests. Groundwater-level measurements and hydrogeologic-unit data were combined to create a potentiometric surface map and to characterize groundwater occurrence and movement. Subsurface inflow from adjacent valleys into Dixie Valley through the basin-fill aquifer was evaluated using hydraulic gradients and Darcy flux computations. The chemical signature and groundwater quality of the Dixie Valley basin-fill aquifer, and potential mixing between basin-fill and geothermal aquifers, were evaluated using chemical data collected from wells and springs during the current study and from previous investigations. Dixie Valley is the terminus of the Dixie Valley flow system, which includes Pleasant, Jersey, Fairview, Stingaree, Cowkick, and Eastgate Valleys. The freshwater aquifer in the study area is composed of unconsolidated basin-fill deposits of Quaternary age. The basin-fill hydrogeologic unit can be several orders of magnitude more transmissive than surrounding and underlying consolidated rocks and Dixie Valley playa deposits. Transmissivity estimates in the basin fill throughout Dixie Valley ranged from 30 to 45,500 feet squared per day; however, a single transmissivity value of 0.1 foot squared per day was estimated for playa deposits. Groundwater generally flows from the mountain range uplands toward the central valley lowlands and eventually discharges near the playa edge. Potentiometric contours east and west of the playa indicate that groundwater is moving eastward from the Stillwater Range and westward from the Clan Alpine Mountains toward the playa. Similarly, groundwater flows from the southern and northern basin boundaries toward the basin center. Subsurface groundwater flow likely enters Dixie Valley from Fairview and Stingaree Valleys in the south and from Jersey and Pleasant Valleys in the north, but groundwater connections through basin-fill deposits were present only across the Fairview and Jersey Valley divides. Annual subsurface inflow from Fairview and Jersey Valleys ranges from 700 to 1,300 acre-feet per year and from 1,800 to 2,300 acre-feet per year, respectively. Groundwater flow between Dixie, Stingaree, and Pleasant Valleys could occur through less transmissive consolidated rocks, but only flow through basin fill was estimated in this study. Groundwater in the playa is distinct from the freshwater, basin-fill aquifer. Groundwater mixing between basin-fill and playa groundwater systems is physically limited by transmissivity contrasts of about four orders of magnitude. Total dissolved solids in playa deposit groundwater are nearly 440 times greater than total dissolved solids in the basin-fill groundwater. These distinctive physical and chemical flow restrictions indicate that groundwater interaction between the basin fill and playa sediments was minimal during this study period (water years 2009–11). Groundwater in Dixie Valley generally can be characterized as a sodium bicarbonate type, with greater proportions of chloride north of the Dixie Valley playa, and greater proportions of sulfate south of the playa. Analysis of major ion water chemistry data sampled during the study period indicates that groundwater north and south of Township 22N differ chemically. Dixie Valley groundwater quality is marginal when compared with national primary and secondary drinking-water standards. Arsenic and fluoride concentrations exceed primary drinking water standards, and total dissolved solids and manganese concentrations exceed secondary drinking water standards in samples collected during this study. High concentrations of boron and tungsten also were observed. Chemical comparisons between basin-fill and geothermal aquifer water indicate that most basin-fill groundwater sampled could contain 10–20 percent geothermal water. Geothermal indicators such as high temperature, lithium, boron, chloride, and silica suggest that mixing occurs in many wells that tap the basin-fill aquifer, particularly on the north, south, and west sides of the basin. Magnesium-lithium geothermometers indicate that some basin-fill aquifer water sampled for the current study likely originates from water that was heated above background mountain-block recharge temperatures (between 3 and 15 degrees Celsius), highlighting the influence of mixing with warm water that was possibly derived from geothermal sources.

Effects of seepage from fly-ash settling ponds and construction dewatering on ground-water levels in the Cowles unit, Indiana Dunes National Lakeshore, Indiana

USGS Publications Warehouse

Meyer, William R.; Tucci, Patrick

1979-01-01

Part of the Indiana Dunes National Lakeshore shares a common boundary with the Northern Indiana Public Service Company (NIPSCO). This area is underlain by unconsolidated deposits approximately 180 feet thick. NIPSCO accumulates fly ash from the burning of coal in electric-power generating units in settling ponds. Seepage from the ponds has raised ground-water levels above natural levels approximately 15 feet under the ponds and more than 10 feet within the Lakeshore. NIPSCO is presently (1977) constructing a nuclear powerplant, and construction activities include pumping ground water to dewater the construction site. The company has installed a slurry wall around the site to prevent lowering of ground-water levels within the Lakeshore. Plans call for continuous pumping through at least December 1979. A multilayered digital flow model was constructed to simulate the ground-water system. The model was used to demonstrate the effects of seepage from the fly-ash ponds on ground-water levels. Also, the model indicated a decline of 3 feet or less in the upper sand unit and 5 feet or less in the lower sand unit within the Lakeshore.

Ground Water Atlas of the United States: Introduction and national summary

USGS Publications Warehouse

Miller, James A.

1999-01-01

The Ground Water Atlas of the United States provides a summary of the most important information available for each principal aquifer, or rock unit that will yield usable quantities of water to wells, throughout the 50 States, Puerto Rico, and the U.S. Virgin Islands. The Atlas is an outgrowth of the Regional Aquifer-System Analysis (RASA) program of the U.S. Geological Survey (USGS), a program that investigated 24 of the most important aquifers and aquifer systems of the Nation and one in the Caribbean Islands (fig. 1). The objectives of the RASA program were to define the geologic and hydrologic frameworks of each aquifer system, to assess the geochemistry of the water in the system, to characterize the ground-water flow system, and to describe the effects of development on the flow system. Although the RASA studies did not cover the entire Nation, they compiled much of the data needed to make the National assessments of ground-water resources presented in the Ground Water Atlas of the United States. The Atlas, however, describes the location, extent, and geologic and hydrologic characteristics of all the important aquifers in the United States, including those not studied by the RASA program. The Atlas is written so that it can be understood by readers who are not hydrologists. Simple language is used to explain technical terms. The principles that control the presence, movement, and chemical quality of ground water in different climatic, topographic, and geologic settings are clearly illustrated. The Atlas is, therefore, useful as a teaching tool for introductory courses in hydrology or hydrogeology at the college level and as an overview of ground-water conditions for consultants who need information about an individual aquifer. It also serves as an introduction to regional and National ground-water resources for lawmakers, personnel of local, State, or Federal agencies, or anyone who needs to understand ground-water occurrence, movement, and quality. The purpose of the Ground Water Atlas of the United States is to summarize, in one publication with a common format, the most important ground-water information that has been collected over many years by the USGS, other Federal agencies, and State and local water management agencies. The purpose of this introductory chapter is to describe the content of the Atlas; to discuss the characteristics, use, and limitations of the maps and other types of illustrations used in the different chapters of the book; to summarize the locations of the principal aquifers on a Nationwide map; and to give an example of an aquifer in each principal hydrogeologic setting.

Superfund Record of Decision (EPA Region 4): Agriculture and Nutrition (Montgomery), Operable Unit 2, Montgomery, AL, September 28, 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

This decision document presents the selected remedial action for the T.H. Agriculture and Nutrition (THAN) Site, Montgomery, Alabama. Operable Unit Two (OU2) encompasses the remediation of the contaminated soils and sediments on the Site, and also establishes the performance standards for the groundwater remedy. Upon reaching the cleanup standards for groundwater at an established point(s) of compliance, the groundwater pumping system will be shut down.

Continuous resistivity profiling data from the Corsica River Estuary, Maryland

USGS Publications Warehouse

Cross, V.A.; Bratton, J.F.; Worley, C.R.; Crusius, John; Kroeger, K.D.

2011-01-01

Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine its importance in nutrient delivery to the Chesapeake Bay. The Corsica River Estuary represents a coastal lowland setting typical of much of the eastern bay. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the lower estuary in April and May 2007. Resource managers are concerned about nutrients that are entering the estuary via SGD that may be contributing to eutrophication, harmful algal blooms, and fish kills. Techniques employed in the study included continuous resistivity profiling (CRP), piezometer sampling of submarine groundwater, and collection of a time series of radon tracer activity in surface water. A CRP system measures electrical resistivity of saturated subestuarine sediments to distinguish those bearing fresh water (high resistivity) from those with saline or brackish pore water (low resistivity). This report describes the collection and processing of CRP data and summarizes the results. Based on a grid of 67.6 kilometers of CRP data, low-salinity (high-resistivity) groundwater extended approximately 50-400 meters offshore from estuary shorelines at depths of 5 to >12 meters below the sediment surface, likely beneath a confining unit. A band of low-resistivity sediment detected along the axis of the estuary indicated the presence of a filled paleochannel containing brackish groundwater. The meandering paleochannel likely incised through the confining unit during periods of lower sea level, allowing the low-salinity groundwater plumes originating from land to mix with brackish subestuarine groundwater along the channel margins and to discharge. A better understanding of the spatial variability and geological controls of submarine groundwater flow beneath the Corsica River Estuary could lead to improved models and mitigation strategies for nutrient over-enrichment in the estuary and in other similar settings.

Groundwater vulnerability mapping in Guadalajara aquifers system (Western Mexico)

NASA Astrophysics Data System (ADS)

Rizo-Decelis, L. David; Marín, Ana I.; Andreo, Bartolomé

2016-04-01

Groundwater vulnerability mapping is a practical tool to implement strategies for land-use planning and sustainable socioeconomic development coherent with groundwater protection. The objective of vulnerability mapping is to identify the most vulnerable zones of catchment areas and to provide criteria for protecting the groundwater used for drinking water supply. The delineation of protection zones in fractured aquifers is a challenging task due to the heterogeneity and anisotropy of hydraulic conductivities, which makes difficult prediction of groundwater flow organization and flow velocities. Different methods of intrinsic groundwater vulnerability mapping were applied in the Atemajac-Toluquilla groundwater body, an aquifers system that covers around 1300 km2. The aquifer supplies the 30% of urban water resources of the metropolitan area of Guadalajara (Mexico), where over 4.6 million people reside. Study area is located in a complex neotectonic active volcanic region in the Santiago River Basin (Western Mexico), which influences the aquifer system underneath the city. Previous works have defined the flow dynamics and identified the origin of recharge. In addition, the mixture of fresh groundwater with hydrothermal and polluted waters have been estimated. Two main aquifers compose the multilayer system. The upper aquifer is unconfined and consists of sediments and pyroclastic materials. Recharge of this aquifer comes from rainwater and ascending vertical fluids from the lower aquifer. The lower aquifer consists of fractured basalts of Pliocene age. Formerly, the main water source has been the upper unit, which is a porous and unconsolidated unit, which acts as a semi-isotropic aquifer. Intense groundwater usage has resulted in lowering the water table in the upper aquifer. Therefore, the current groundwater extraction is carried out from the deeper aquifer and underlying bedrock units, where fracture flow predominates. Pollution indicators have been reported in some monitoring wells, which have been related to anthropogenic activity. Vulnerability maps were produced using different parametric methods (e.g.: DRASTIC, GOD, DISCO, AVI), then the results are compared and assessed. Since each one of these methods use different number of parameters and weights, relatively different results were obtained, although the results have been evaluated with common cartographic inputs. The comparison between selected methods shows that the GOD method results are more correlated with the other methods and produces vulnerability maps comparable with them. Even though groundwater vulnerability is a critical issue around the world, no protection zones have been delineated in Guadalajara city, one of the biggest in Latin America. The groundwater contamination in the study area poses a serious risk for a large population and the environment. This work aims to propose an approach for groundwater protection cartography, based on the application and the comparison of results from different contamination vulnerability methods. These outcomes may assist water authorities to identify the higher vulnerable zones of the aquifers, in order to improving and adapting the land planning and management according to the protection of the own water resources.

Guidelines for model calibration and application to flow simulation in the Death Valley regional groundwater system

USGS Publications Warehouse

Hill, M.C.; D'Agnese, F. A.; Faunt, C.C.

2000-01-01

Fourteen guidelines are described which are intended to produce calibrated groundwater models likely to represent the associated real systems more accurately than typically used methods. The 14 guidelines are discussed in the context of the calibration of a regional groundwater flow model of the Death Valley region in the southwestern United States. This groundwater flow system contains two sites of national significance from which the subsurface transport of contaminants could be or is of concern: Yucca Mountain, which is the potential site of the United States high-level nuclear-waste disposal; and the Nevada Test Site, which contains a number of underground nuclear-testing locations. This application of the guidelines demonstrates how they may be used for model calibration and evaluation, and also to direct further model development and data collection.Fourteen guidelines are described which are intended to produce calibrated groundwater models likely to represent the associated real systems more accurately than typically used methods. The 14 guidelines are discussed in the context of the calibration of a regional groundwater flow model of the Death Valley region in the southwestern United States. This groundwater flow system contains two sites of national significance from which the subsurface transport of contaminants could be or is of concern: Yucca Mountain, which is the potential site of the United States high-level nuclear-waste disposal; and the Nevada Test Site, which contains a number of underground nuclear-testing locations. This application of the guidelines demonstrates how they may be used for model calibration and evaluation, and also to direct further model development and data collection.

Groundwater quality in the Northern Atlantic Coastal Plain aquifer system, eastern United States

USGS Publications Warehouse

Lindsey, Bruce; Belitz, Kenneth

2017-01-19

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Northern Atlantic Coastal Plain aquifer system constitutes one of the important areas being evaluated. One or more inorganic constituents with human-health benchmarks were detected at high concentrations in about 15 percent of the study area and at moderate concentrations in about 17 percent. Organic constituents were not detected at high concentrations in the study area.

Groundwater quality in the Coastal Lowlands aquifer system, south-central United States

USGS Publications Warehouse

Barlow, Jeannie R.B.; Belitz, Kenneth

2017-01-19

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Coastal Lowlands aquifer system constitutes one of the important areas being evaluated. One or more inorganic constituents with human-health benchmarks were detected at high concentrations in about 12 percent of the study area and at moderate concentrations in about 18 percent. Organic constituents were not detected at high or moderate concentrations in the study area.

Aquifer tests and simulation of ground-water flow in Triassic sedimentary rocks near Colmar, Bucks and Montgomery Counties, Pennsylvania

USGS Publications Warehouse

Risser, Dennis W.; Bird, Philip H.

2003-01-01

This report presents the results of a study by the U.S. Geological Survey in cooperation with the U.S. Environmental Protection Agency to evaluate ground-water flow in Triassic sedimentary rocks near Colmar, in Bucks and Montgomery Counties, Pa. The study was conducted to help the U.S. Environmental Protection Agency evaluate remediation alternatives at the North Penn Area 5 Superfund Site near Colmar, where ground water has been contaminated by volatile organic solvents (primarily trichloroethene). The investigation focused on determining the (1) drawdown caused by separately pumping North PennWater Authority wells NP–21 and NP–87, (2) probable paths of groundwater movement under present-day (2000) conditions (with NP–21 discontinued), and (3) areas contributing recharge to wells if pumping from wells NP-21 or NP–87 were restarted and new recovery wells were installed. Drawdown was calculated from water levels measured in observation wells during aquifer tests of NP–21 and NP–87. The direction of ground-water flow was estimated by use of a three-dimensional ground-water-flow model.Aquifer tests were conducted by pumping NP–21 for about 7 days at 257 gallons per minute in June 2000 and NP–87 for 3 days at 402 gallons per minute in May 2002. Drawdown was measured in 45 observation wells during the NP–21 test and 35 observation wells during the NP–87 test. Drawdown in observation wells ranged from 0 to 6.8 feet at the end of the NP–21 test and 0.5 to 12 feet at the end of the NP–87 test. The aquifer tests showed that ground-water levels declined mostly in observation wells that were completed in the geologic units penetrated by the pumped wells. Because the geologic units dip about 27 degrees to the northwest, shallow wells up dip to the southeast of the pumped well showed a good hydraulic connection to the geologic units stressed by pumping. Most observation wells down dip from the pumping well penetrated units higher in the stratigraphic section that were not well connected to the units stressed by pumping. The best hydraulic connection to the pumped wells was indicated by large drawdown in observation wells that penetrate the water-bearing unit encountered below 400 feet below land surface in wells NP–21 and NP–87. The hydraulic connection between wells NP–21 (or NP–87) and observation wells in the southern area of ground-water contamination near the BAE Systems facility is good because the observation wells probably penetrate this water-bearing unit.A 3-dimensional, finite-difference, groundwater- flow model was used to simulate flow paths and areas contributing recharge to wells for current (2000) conditions of pumping in the Colmar area and for hypothetical situations of pumping suggested by the U.S. Environmental Protection Agency that might be used for remediation. Simulations indicate that under current conditions, ground water in the northern area of contamination near the former Stabilus facility moves to the northwest and discharges mostly to West Branch Neshaminy Creek; in the southern area of contamination near BAE Systems facility, ground water probably moves west and discharges to a tributary of West Branch Neshaminy Creek near well NP–21. Model simulations indicate that if NP–21 or NP–87 are pumped at 400 gallons per minute, groundwater recharge is likely captured from the southern area of contamination, but ground-water recharge from the northern area of contamination is less likely to be captured by the pumping. Simulations also indicate that pumping of a new recovery well near BAE Systems facility at 8 gallons per minute and two new recovery wells near the former Stabilus facility at a total of about 30 gallons per minute probably would capture most of the ground-water recharge in the areas where contamination is greatest.

Occurrence of pesticides in shallow groundwater of the United States: initial results from the National Water-Quality Assessment program

USGS Publications Warehouse

Kolpin, Dana W.; Barbash, Jack E.; Gilliom, Robert J.

1998-01-01

The first phase of intensive data collection for the National Water-Quality Assessment (NAWQA) was completed during 1993−1995 in 20 major hydrologic basins of the United States. Groundwater land-use studies, designed to sample recently recharged groundwater (generally within 10 years) beneath specific land-use and hydrogeologic settings, are a major component of the groundwater quality as sessment for NAWQA. Pesticide results from the 41 land-use studies conducted during 1993−1995 indicate that pesticides were commonly detected in shallow groundwater, having been found at 54.4% of the 1034 sites sampled in agricultural and urban settings across the United States. Pesticide concentrations were generally low, with over 95% of the detections at concentrations less than 1 μg/L. Of the 46 pesticide compounds examined, 39 were detected. The compounds detected most frequently were atrazine (38.2%), deethylatrazine (34.2%), simazine (18.0%), metolachlor (14.6%), and prometon (13.9%). Statistically significant relations were observed between frequencies of detection and the use, mobility, and persistence of these compounds. Pesticides were commonly detected in both agricultural (56.4%; 813 sites) and urban (46.6%; 221 sites) settings. Frequent detections of pesticides in urban areas indicate that, as is the case with agricultural pesticide use in agricultural areas, urban and suburban pesticide use significantly contribute to pesticide occurrence in shallow groundwater. Although pesticides were detected in groundwater sampled in urban areas and all nine of the agricultural land-use categories examined, significant variations in occurrence were observed among these categories. Maximum contaminant levels (MCLs) established by the U.S. Environmental Protection Agency for drinking water were exceeded for only one pesticide (atrazine, 3 μg/L) at a single location. However, MCLs have been established for only 25 of the 46 pesticide compounds examined, do not cover pesticide degradates, and, at present, do not take into account additive or synergistic effects of combinations of pesticide compounds or potential effects on nearby aquatic ecosystems.

A conjunctive use hydrologic model for a semi-arid region with irrigated agriculture

NASA Astrophysics Data System (ADS)

Ruud, N. C.; Harter, T.

2003-04-01

A GIS-based sub-basin scale conjunctive use (CU) model is developed for a semi-arid agricultural area in the southern San Joaquin Valley, California. The study area is 2230 square kilometers, and consists of 9114 individual landuse units and 26 water service districts. The CU model consists of three sub-models: 1) a surface water supply (SWS) model, 2) an unsaturated zone water budget (UZWB) model, and 3) a groundwater flow model. The study period is 1970-99. For each modeled surface water channel, the SWS model computes monthly surface water deliveries to each district and conveyance losses due to evaporation and seepage. The UZWB model then calculates the monthly water storage changes in the soil root zone and deep vadose zone of each landuse unit. The UZWB model is driven by surface water applications, precipitation, and crop consumptive use (evapotranspiration) demands. Its outputs are the recharge to the unconfined aquifer and the groundwater pumping demand from the unconfined and confined aquifers. The transient recharge and pumping rates become input for the groundwater flow model which calculates changes in unconfined aquifer water levels and inter-district groundwater fluxes. The groundwater flow model was calibrated against data from 1970-85 and validated with data from 1986-99. From 1970-99, a total of 18500 million cubic meters (MCM) of surface water was applied to land units in the study area. Precipitation added from 219 MCM (1990) to 1200 MCM (1998) annually. The combined total annual agricultural and urban consumptive use ranged from 1070 MCM in 1970 to 1540 MCM in 1999. Total annual channel seepage varied over almost two orders of magnitude from a low of 10 MCM in 1977 to 576 MCM in 1983. Diffuse recharge from surface applied water ranged from 79.9 MCM in 1992 to 432 MCM in 1983. The estimated total pumping ranged from 183 MCM in 1978 to 703 MCM in 1990. As expected, pumping was heaviest during the droughts of 1975-77 and 1987-92, and lightest during the wet years of 1973, 1978, 1982-83, 1995, and 1998. The study area cumulative annual groundwater storage changes were computed by the CU model and compared against those of the water-table fluctuation (WTF) method. Relative to 1970, the maximum groundwater accumulation occurred in 1987 with the WTF method and the CU model estimating positive storage changes of 1410 MCM and 1110 MCM. The maximum groundwater overdraft (storage depletion) occurred in 1993 with the WTF method and the CU model estimating negative storage changes of 1990 MCM and 1500 MCM. Annual inter-district net groundwater fluxes ranged from negligibly small (<0.123 MCM) to as much as 98.7 MCM between some of the larger districts.

Evaluation of the ground-water resources of parts of Lancaster and Berks Counties, Pennsylvania

USGS Publications Warehouse

Gerhart, J.M.; Lazorchick, G.J.

1984-01-01

Secondary openings in bedrock are the avenues for virtually all ground-water flow in a 626-sqare-mile area in Lancaster and Berks Counties, Pennsylvania. The number, size, and interconnection of secondary openings are functions of lithology, depth, and topography. Ground water actively circulates to depths of 150 to 300 feet below land surface. Total average annual ground-water recharge for the area is 388 million gallons per day, most of which discharges to streams from local, unconfined flow systems. A digital ground-water flow model was developed to simulate unconfined flow under several different recharge and withdrawal scenarios. On the basis of lithologic and hydrologic differences, the modeled area was sub-divided into 22 hydrogeologic units. A finite-difference grid with rectangular blocks, each 2,015 by 2,332 feet, was used. The model was calibrated under steady-state and transient conditions. The steady-state calibration was used to determine hydraulic conductivities and stream leakage coefficients and the transient calibration was used to determine specific yields. The 22 hydrogeologic units fall into four general lithologies: Carbonate rocks, metamorphic rocks, Paleozoic sedimentary rocks, and Triassic sedimentary rocks. Average hydraulic conductivity ranges from about 8.8 feet per day in carbonate units to about .5 feet per day in metamorphic units. The Stonehenge Formation (limestone) has the greatest average hydraulic conductivity--85.2 feet per day in carbonate units to about 0.11 feet per day in the greatest gaining-strem leakage coefficient--16.81 feet per day. Specific yield ranges from 0.06 to 0.09 in carbonate units, and is 0.02 to 0.015, and 0.012 in metamorphic, Paleozoic sedimentary, and Triassic sedimentary units, respectively. Transient simulations were made to determine the effects of four different combinations of natural and artificial stresses. Natural aquifer conditions (no ground-water withdrawals) and actual aquifer conditions (current ground-water withdrawals) were simulated for two years under normal seasonal and hypothetical drought (60-percent reduction in winter-spring recharge) conditions. In October, 6 months after the hypothetical drought, simulated declines in water-table altitude due to the drought occurred everywhere and ranged from a median of 3.6 feet in carbonate units to 8.7 feet in carbonate units. Simulated base flows for five major streams were reduced by 33 to 51 percent during the hypothetical drought. Also in October, maximum simulated declines in water-table altitude due to ground-water withdrawls ranged from 33 feet in carbonate units to 79 feet in Triassic sedimentary units. Simulated base flows for five major streams were reduced by the amount of ground water withdrawn. Finally, again in October, maximum simulated declines in water-table altitude due to the combination of hypothetical drought and ground-water withdrawls ranged from 38 feet in carbonate units to 109 feet in Triassic sedimentary units. Due to aquifer dewatering, simulated declines were as much as 24 feet greater than the sum of the separate simulated declines that were caused by hypothetical drought and ground-water withdrawals. Some of the greatest simulated declines were in well fields, operated by three municipalities that experienced water-supply problems during the 1980-81 drought.

A new tool to assess groundwater resources in the Mississippi embayment

USGS Publications Warehouse

Clark, Brian R.; Freiwald, David A.

2011-01-01

What is the Mississippi Embayment? The Mississippi embayment study area encompasses approximately 78,000 square miles in eight States and includes large parts of Arkansas, Louisiana, Mississippi, and Tennessee, and smaller areas of Alabama, Illinois, Kentucky, and Missouri (fig. 1). The Mississippi embayment is essentially a basin that slopes toward the Gulf of Mexico and is filled with sediments of alternating sand, silt, and clay layers. There are two principal aquifers in the embayment-the Mississippi River Valley alluvial aquifer (alluvial aquifer) and the middle Claiborne aquifer (fig. 1). The shallow alluvial aquifer is the primary source of groundwater for irrigation in the largely agricultural region, while the deeper middle Claiborne aquifer is a primary source of drinking water for many of the 5.2 million people living in the embayment. The U.S. Geological Survey (USGS) is conducting large-scale multidisciplinary regional studies of groundwater availability for the Nation. Studies comprise individual assessments of regional groundwater-flow systems that encompass varied terrains and document a comprehensive regional and national perspective of groundwater resources. Collectively, these studies are the foundation for the national assessment of groundwater availability and are conducted in cooperation with other Federal, State, local governments, and the private sector. Numerical groundwater-flow models are used in these studies to document effects of human activities and climate variability on groundwater levels, changes in aquifer storage, and flow between groundwater and surface-water bodies. As part of the Mississippi Embayment Regional Aquifer Study (MERAS), a numerical model was constructed of 13 layers over 78,000 square miles representing multiple aquifers and confining units for the period of 1870 to 2007. The model is a tool that was used to assess and better understand groundwater resources.

Physical stratigraphy and hydrostratigraphy of Upper Cretaceous and Paleocene sediments, Burke and Screven Counties, Georgia

USGS Publications Warehouse

Falls, W.F.; Baum, J.S.; Prowell, D.C.

1997-01-01

Six geologic units are recognized in the Cretaceous and the Paleocene sediments of eastern Burke and Screven Counties in Georgia on the basis of lithologic, geophysical, and paleontologic data collected from three continuously cored testholes in Georgia and one testhole in South Carolina. The six geologic units are separated by regional unconformities and are designated from oldest to youngest as the Cape Fear Formation, the Middendorf Formation, the Black Creek Group (undivided), and the Steel Creek Formation in the Upper Cretaceous section, and the Ellenton and the Snapp Formations in the Paleocene section. The geologic units provide a spatial and temporal framework for the identification and correlation of a basal confining unit beneath the Midville aquifer system and five aquifers and five confining units in the Dublin and the Midville aquifer systems. The Dublin aquifer system is divided hydrostratigraphically into the Millers Pond, the upper Dublin, and the lower Dublin aquifers. The Midville aquifer system is divided hydrostratigraphically into the upper and the lower Midville aquifers. The fine-grained sediments of the Millers Pond, the lower Dublin, and the lower Midville confining units are nonmarine deposits and are present in the upper part of the Snapp Formation, the Black Creek Group (undivided), and the Middendorf Formation, respectively. Hydrologic data for specific sets of monitoring wells at the Savannah River Site in South Carolina and the Millers Pond site in Georgia confirm that these three units are leaky confining units and locally impede vertical ground-water flow between adjacent aquifers. The fine-grained sediments of the upper Dublin and the upper Midville confining units are marine-deltaic deposits of the Ellenton Formation and the Black Creek Group (undivided), respectively. Hydrologic data confirm that the upper Dublin confining unit regionally impedes vertical ground-water flow on both sides of the Savannah River. The upper Midville confining unit impedes vertical ground-water flow in the middle and downdip parts of the study area and is a leaky confining unit in the updip part of the study area. Recognition of the upper Dublin confining unit as a regional confining unit between the Millers Pond and the upper Dublin aquifers also confirms that the Millers Pond aquifer is a separate hydrologic unit from the rest of the Dublin aquifer system. This multi-aquifer framework increases the vertical hydrostratigraphic resolution of hydraulic properties and gradients in the Dublin and Midville aquifer systems for the investigation of ground-water flow beneath the Savannah River in the vicinity of the U.S. Department of Energy Savannah River Site.

Improving groundwater predictions utilizing seasonal precipitation forecasts from general circulation models forced with sea surface temperature forecasts

USGS Publications Warehouse

Almanaseer, Naser; Sankarasubramanian, A.; Bales, Jerad

2014-01-01

Recent studies have found a significant association between climatic variability and basin hydroclimatology, particularly groundwater levels, over the southeast United States. The research reported in this paper evaluates the potential in developing 6-month-ahead groundwater-level forecasts based on the precipitation forecasts from ECHAM 4.5 General Circulation Model Forced with Sea Surface Temperature forecasts. Ten groundwater wells and nine streamgauges from the USGS Groundwater Climate Response Network and Hydro-Climatic Data Network were selected to represent groundwater and surface water flows, respectively, having minimal anthropogenic influences within the Flint River Basin in Georgia, United States. The writers employ two low-dimensional models [principle component regression (PCR) and canonical correlation analysis (CCA)] for predicting groundwater and streamflow at both seasonal and monthly timescales. Three modeling schemes are considered at the beginning of January to predict winter (January, February, and March) and spring (April, May, and June) streamflow and groundwater for the selected sites within the Flint River Basin. The first scheme (model 1) is a null model and is developed using PCR for every streamflow and groundwater site using previous 3-month observations (October, November, and December) available at that particular site as predictors. Modeling schemes 2 and 3 are developed using PCR and CCA, respectively, to evaluate the role of precipitation forecasts in improving monthly and seasonal groundwater predictions. Modeling scheme 3, which employs a CCA approach, is developed for each site by considering observed groundwater levels from nearby sites as predictands. The performance of these three schemes is evaluated using two metrics (correlation coefficient and relative RMS error) by developing groundwater-level forecasts based on leave-five-out cross-validation. Results from the research reported in this paper show that using precipitation forecasts in climate models improves the ability to predict the interannual variability of winter and spring streamflow and groundwater levels over the basin. However, significant conditional bias exists in all the three modeling schemes, which indicates the need to consider improved modeling schemes as well as the availability of longer time-series of observed hydroclimatic information over the basin.

Enhancing Groundwater Cost Estimation with the Interpolation of Water Tables across the United States

NASA Astrophysics Data System (ADS)

Rosli, A. U. M.; Lall, U.; Josset, L.; Rising, J. A.; Russo, T. A.; Eisenhart, T.

2017-12-01

Analyzing the trends in water use and supply across the United States is fundamental to efforts in ensuring water sustainability. As part of this, estimating the costs of producing or obtaining water (water extraction) and the correlation with water use is an important aspect in understanding the underlying trends. This study estimates groundwater costs by interpolating the depth to water level across the US in each county. We use Ordinary and Universal Kriging, accounting for the differences between aquifers. Kriging generates a best linear unbiased estimate at each location and has been widely used to map ground-water surfaces (Alley, 1993).The spatial covariates included in the universal Kriging were land-surface elevation as well as aquifer information. The average water table is computed for each county using block kriging to obtain a national map of groundwater cost, which we compare with survey estimates of depth to the water table performed by the USDA. Groundwater extraction costs were then assumed to be proportional to water table depth. Beyond estimating the water cost, the approach can provide an indication of groundwater-stress by exploring the historical evolution of depth to the water table using time series information between 1960 and 2015. Despite data limitations, we hope to enable a more compelling and meaningful national-level analysis through the quantification of cost and stress for more economically efficient water management.

BIOSCREEN: Natural Attenuation Decision Support System. User’s Manual Version 1.3

DTIC Science & Technology

1996-06-01

of Water - Bearing Unit Nj \\ Bottom of Water - --1--. Bearing Unit by Charles J. Newell. Ph.D., P.E. and R. Kevi:n McLeod Groundwater Services, Inc...Application,’ Water Resoi r. Res. 22:1983-1990. Connor, J.A., C.J. Newell, J.P. Nevin, and I IS. Rifaj, 1994. "Guidelines for Use of Groundwater ...Biodegradation Kinetics With an Instantaneous Reaction Model for Groundwater ,’ Water Resources Research, Vol. 26, No. 4, pp. 637-645, April 1990. Rifat. H. S

Quantifying effects of climate change on the snowmelt-dominated groundwater resources of northern New England

USGS Publications Warehouse

Dudley, Robert W.; Hodgkins, Glenn A.; Shanley, James B.; Mack, Thomas J.

2010-01-01

Recent U.S. Geological Survey (USGS) climate studies in New England have shown substantial evidence of hydrologic changes during the last 100 years, including trends toward earlier snowmelt runoff, decreasing occurrence of river ice, and decreasing winter snowpack. These studies are being expanded to include investigation of trends in groundwater levels and fluctuations. Groundwater is an important drinking-water source throughout northern New England (Maine, New Hampshire, and Vermont). The USGS is currently investigating whether or not groundwater recharge from snowmelt and precipitation exhibits historical trends. In addition to trend-testing, groundwater resources also will be analyzed by relating groundwater-level changes to the large year-to-year variability in weather conditions. Introduction The USGS has documented many seasonal climate-related changes in the northeastern United States that have occurred during the last 30 to 150 years. These changes include earlier snowmelt runoff in the late winter and early spring, decreasing duration of ice on rivers and lakes, decreasing ratio of snowfall to total precipitation, and denser and thinner late-winter snowpack. All of these changes are consistent with warming winter and spring air temperatures (Dudley and Hodgkins, 2002; Hodgkins and others, 2002; Huntington and others, 2004; Hodgkins and others, 2005; Hodgkins and Dudley, 2006a; Hodgkins and Dudley, 2006b). Climate-model projections for the Northeast indicate air-temperature warming, earlier snowmelt runoff, increases in annual evaporation, and decreased low streamflows (Hayhoe and others, 2007). The contribution and timing of spring snowmelt to groundwater recharge is particularly important to groundwater resources in the northeastern United States where aquifers typically consist of thin sediments overlying crystalline bedrock with relatively little storage capacity (Mack, 2009). Following spring recharge, groundwater slowly flows into streams throughout the summer. This groundwater flow is a source of cool water during the summer and accounts for a large proportion of the streamflow during summer low-flow periods. Groundwater is an important drinking-water source in northern New England. Approximately 32 percent of public water suppliers draw water from groundwater sources in Vermont, New Hampshire, and Maine, and approximately 40 percent of the population derives its drinking water from private wells (Kenny and others, 2009). It is vital to understand changes that may be occurring to such an important resource for planning industrial and agricultural water uses and protecting drinking water.

Geostatistics-based groundwater-level monitoring network design and its application to the Upper Floridan aquifer, USA.

PubMed

Bhat, Shirish; Motz, Louis H; Pathak, Chandra; Kuebler, Laura

2015-01-01

A geostatistical method was applied to optimize an existing groundwater-level monitoring network in the Upper Floridan aquifer for the South Florida Water Management District in the southeastern United States. Analyses were performed to determine suitable numbers and locations of monitoring wells that will provide equivalent or better quality groundwater-level data compared to an existing monitoring network. Ambient, unadjusted groundwater heads were expressed as salinity-adjusted heads based on the density of freshwater, well screen elevations, and temperature-dependent saline groundwater density. The optimization of the numbers and locations of monitoring wells is based on a pre-defined groundwater-level prediction error. The newly developed network combines an existing network with the addition of new wells that will result in a spatial distribution of groundwater monitoring wells that better defines the regional potentiometric surface of the Upper Floridan aquifer in the study area. The network yields groundwater-level predictions that differ significantly from those produced using the existing network. The newly designed network will reduce the mean prediction standard error by 43% compared to the existing network. The adoption of a hexagonal grid network for the South Florida Water Management District is recommended to achieve both a uniform level of information about groundwater levels and the minimum required accuracy. It is customary to install more monitoring wells for observing groundwater levels and groundwater quality as groundwater development progresses. However, budget constraints often force water managers to implement cost-effective monitoring networks. In this regard, this study provides guidelines to water managers concerned with groundwater planning and monitoring.

Sources of groundwater and characteristics of surface-water recharge at Bell, White, and Suwannee Springs, Florida, 2012–13

USGS Publications Warehouse

Stamm, John F.; McBride, W. Scott

2016-12-21

Discharge from springs in Florida is sourced from aquifers, such as the Upper Floridan aquifer, which is overlain by an upper confining unit that locally can have properties of an aquifer. Water levels in aquifers are affected by several factors, such as precipitation, recharge, and groundwater withdrawals, which in turn can affect discharge from springs. Therefore, identifying groundwater sources and recharge characteristics can be important in assessing how these factors might affect flows and water levels in springs and can be informative in broader applications such as groundwater modeling. Recharge characteristics include the residence time of water at the surface, apparent age of recharge, and recharge water temperature.The groundwater sources and recharge characteristics of three springs that discharge from the banks of the Suwannee River in northern Florida were assessed for this study: Bell Springs, White Springs, and Suwannee Springs. Sources of groundwater were also assessed for a 150-foot-deep well finished within the Upper Floridan aquifer, hereafter referred to as the UFA well. Water samples were collected for geochemical analyses in November 2012 and October 2013 from the three springs and the UFA well. Samples were analyzed for a suite of major ions, dissolved gases, and isotopes of sulfur, strontium, oxygen, and hydrogen. Daily means of water level and specific conductance at White Springs were continuously recorded from October 2012 through December 2013 by the Suwannee River Water Management District. Suwannee River stage at White Springs was computed on the basis of stage at a U.S. Geological Survey streamgage about 2.4 miles upstream. Water levels in two wells, located about 2.5 miles northwest and 13 miles southeast of White Springs, were also used in the analyses.Major ion concentrations were used to differentiate water from the springs and Upper Floridan aquifer into three groups: Bell Springs, UFA well, and White and Suwannee Springs. When considered together, evidence from water-level, specific conductance, major-ion concentration, and isotope data indicated that groundwater at Bell Springs and the UFA well was a mixture of surface water and groundwater from the upper confining unit, and that groundwater at White and Suwannee Springs was a mixture of surface water, groundwater from the upper confining unit, and groundwater from the Upper Floridan aquifer. Higher concentrations of magnesium in groundwater samples at the UFA well than in samples at Bell Springs might indicate less mixing with surface water at the UFA well than at Bell Springs. Characteristics of surface-water recharge, such as residence time at the surface, apparent age, and recharge water temperature, were estimated on the basis of isotopic ratios, and dissolved concentrations of gases such as argon, tritium, and sulfur hexafluoride. Oxygen and deuterium isotopic ratios were consistent with rapid recharge by rainwater for samples collected in 2012, and longer residence time at the surface (ponding) for samples collected in 2013. Apparent ages of groundwater samples, computed on the basis of tritium activity and sulfur hexafluoride concentration, indicated groundwater recharge occurred after the late 1980s; however, the estimated apparent ages likely represent the average of ages of multiple sources. Recharge since the 1980s is consistent with groundwater from shallow sources, such as the upper confining unit and Upper Floridan aquifer. Recharge water temperature computed for the three springs and UFA well averaged 20.1 degrees Celsius, which is similar to the mean annual air temperature of 20.6 degrees Celsius at a nearby weather station for 1960–2014.

GROUND-WATER POLLUTION PROBLEMS IN THE SOUTHEASTERN UNITED STATES

EPA Science Inventory

An evaluation of principal sources of ground-water contamination has been carried out in seven southeastern States--Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Virginia. Natural ground-water quality is good to excellent, except for the presence of ...

Ground-Water Availability in the United States

USGS Publications Warehouse

Reilly, Thomas E.; Dennehy, Kevin F.; Alley, William M.; Cunningham, William L.

2008-01-01

Ground water is among the Nation's most important natural resources. It provides half our drinking water and is essential to the vitality of agriculture and industry, as well as to the health of rivers, wetlands, and estuaries throughout the country. Large-scale development of ground-water resources with accompanying declines in ground-water levels and other effects of pumping has led to concerns about the future availability of ground water to meet domestic, agricultural, industrial, and environmental needs. The challenges in determining ground-water availability are many. This report examines what is known about the Nation's ground-water availability and outlines a program of study by the U.S. Geological Survey Ground-Water Resources Program to improve our understanding of ground-water availability in major aquifers across the Nation. The approach is designed to provide useful regional information for State and local agencies who manage ground-water resources, while providing the building blocks for a national assessment. The report is written for a wide audience interested or involved in the management, protection, and sustainable use of the Nation's water resources.

Statistical robustness of machine-learning estimates for characterizing a groundwater-surface water system, Southland, New Zealand

NASA Astrophysics Data System (ADS)

Friedel, M. J.; Daughney, C.

2016-12-01

The development of a successful surface-groundwater management strategy depends on the quality of data provided for analysis. This study evaluates the statistical robustness when using a modified self-organizing map (MSOM) technique to estimate missing values for three hypersurface models: synoptic groundwater-surface water hydrochemistry, time-series of groundwater-surface water hydrochemistry, and mixed-survey (combination of groundwater-surface water hydrochemistry and lithologies) hydrostratigraphic unit data. These models of increasing complexity are developed and validated based on observations from the Southland region of New Zealand. In each case, the estimation method is sufficiently robust to cope with groundwater-surface water hydrochemistry vagaries due to sample size and extreme data insufficiency, even when >80% of the data are missing. The estimation of surface water hydrochemistry time series values enabled the evaluation of seasonal variation, and the imputation of lithologies facilitated the evaluation of hydrostratigraphic controls on groundwater-surface water interaction. The robust statistical results for groundwater-surface water models of increasing data complexity provide justification to apply the MSOM technique in other regions of New Zealand and abroad.

Entering the policy debate: An economic evaluation of groundwater policy in flux

NASA Astrophysics Data System (ADS)

Livingston, Marie Leigh; Garrido, Alberto

2004-12-01

This is an age of transition in groundwater policy. The ownership and control of aquifers, changing groundwater quality, and the impact of groundwater on the environment command the attention of policy makers around the globe. Substantial pressure exists for change in the laws and regulations governing groundwater, which are critical to the management of this critical resource. The objective of this paper is to contribute to the practical policy debate from an economic perspective. This study begins by outlining the basic stages of change in groundwater policy and their economic relevance. A set of physical, economic, and institutional indicators are suggested that may help to understand various country issues. The indicators are used to describe some actual experiences in groundwater policy in the United States and Spain that are examined for insights into common policy questions. This study suggests that the public authority to initiate groundwater policy innovations often results from the physical ties between surface and groundwater. In contexts rich with spatial and temporal externalities the situation is more complex, but this increases the social benefits that result from successful reform. A credible threat of losing rights is often necessary to create enough incentives to firm existing rights. Reductions in overall use are better achieved through purchasing and retiring rights, rather than through compensation for nonuse. Finally, the policy issues important to groundwater are often more fundamental than pricing alone. These insights may help policy makers adapt to emerging groundwater management problems.

Application of hydrogeology and groundwater-age estimates to assess the travel time of groundwater at the site of a landfill to the Mahomet Aquifer, near Clinton, Illinois

USGS Publications Warehouse

Kay, Robert T.; Buszka, Paul M.

2016-03-02

The U.S. Geological Survey used interpretations of hydrogeologic conditions and tritium-based groundwater age estimates to assess the travel time of groundwater at a landfill site near Clinton, Illinois (the “Clinton site”) where a chemical waste unit (CWU) was proposed to be within the Clinton landfill unit #3 (CLU#3). Glacial deposits beneath the CWU consist predominantly of low-permeability silt- and clay-rich till interspersed with thin (typically less than 2 feet in thickness) layers of more permeable deposits, including the Upper and Lower Radnor Till Sands and the Organic Soil unit. These glacial deposits are about 170 feet thick and overlie the Mahomet Sand Member of the Banner Formation. The Mahomet aquifer is composed of the Mahomet Sand Member and is used for water supply in much of east-central Illinois.Eight tritium analyses of water from seven wells were used to evaluate the overall age of recharge to aquifers beneath the Clinton site. Groundwater samples were collected from six monitoring wells on or adjacent to the CLU#3 that were open to glacial deposits above the Mahomet aquifer (the upper and lower parts of the Radnor Till Member and the Organic Soil unit) and one proximal production well (approximately 0.5 miles from the CLU#3) that is screened in the Mahomet aquifer. The tritium-based age estimates were computed with a simplifying, piston-flow assumption: that groundwater moves in discrete packets to the sampled interval by advection, without hydrodynamic dispersion or mixing.Tritium concentrations indicate a recharge age of at least 59 years (pre-1953 recharge) for water sampled from deposits below the upper part of the Radnor Till Member at the CLU#3, with older water expected at progressively greater depth in the tills. The largest tritium concentration from a well sampled by this study (well G53S; 0.32 ± 0.10 tritium units) was in groundwater from a sand deposit in the upper part of the Radnor Till Member; the shallowest permeable unit sampled by this study. That result indicated that nearly all groundwater sampled from well G53S entered the aquifer as recharge before 1953. Tritium was detected in a trace concentration in one sample from a second monitoring well open to the upper part of the Radnor Till Member (well G07S; 0.11 ± 0.09 tritium units), and not detected in samples collected from two monitoring wells open to a sand deposit in the lower part of the Radnor Till Member, from two samples collected from two monitoring wells open to the Organic Soil unit, and in two samples collected from a production well screened in the middle of the Mahomet aquifer (a groundwater sample and a sequential replicate sample). The lack of tritium in five of the six groundwater samples collected from the shallow permeable units beneath CLU#3 site and the two samples from the one Mahomet aquifer well indicates an absence of post-1952 recharge. Groundwater-flow paths that could contribute post-1952 recharge to the lower part of the Radnor Till Member, the Organic Soil unit, or the Mahomet aquifer at the CLU#3 are not indicated by these data.Hypothetical two-part mixtures of tritium-dead, pre-1953 recharge water and decay-corrected tritium concentrations in post-1952 recharge were computed and compared with tritium analyses in groundwater sampled from monitoring wells at the CLU#3 site to evaluate whether tritium concentrations in groundwater could be represented by mixtures involving some post-1952 recharge. Results from the hypothetical two-part mixtures indicate that groundwater from monitoring well (G53S) was predominantly composed of pre-1953 recharge and that if present, younger, post-1955 recharge, contributed less than 2.5 percent to that sample. The hypothetical two-part mixing results also indicated that very small amounts of post-1952 recharge composing less than about 2.5 percent of the sample volume could not be distinguished in groundwater samples with tritium concentrations less than about 0.15 TU.The piston-flow based age of recharge determined from the tritium concentration in the groundwater sample from monitoring well G53S yielded an estimated maximum vertical velocity from the land surface to the upper part of the Radnor Till Member of 0.85 feet per year or less. This velocity, ifassumed to apply to the remaining glacial till deposits above the Mahomet aquifer, indicates that recharge flows through the 170 feet of glacial deposits between the base of the proposed chemical waste unit and the top of the Mahomet aquifer in a minimum of 200 years or longer. Analysis of hydraulic data from the site, constrained by a tritium-age based maximum groundwater velocity estimate, computed minimum estimates of effective porosity that range from about 0.021 to 0.024 for the predominantly till deposits above the Mahomet aquifer.Estimated rates of transport of recharge from land surface to the Mahomet aquifer for the CLU#3 site computed using the Darcy velocity equation with site-specific data were about 260 years or longer. The Darcy velocity-based estimates were computed using values that were based on tritium data, estimates of vertical velocity and effective porosity and available site-specific data. Solution of the Darcy velocity equation indicated that maximum vertical groundwater velocities through the deposits above the aquifer were 0.41 or 0.61 feet per year, depending on the site-specific values of vertical hydraulic conductivity (laboratory triaxial test values) and effective porosity used for the computation. The resulting calculated minimum travel times for groundwater to flow from the top of the Berry Clay Member (at the base of the proposed chemical waste unit) to the top of the Mahomet aquifer ranged from about 260 to 370 years, depending on the velocity value used in the calculation. In comparison, plausible travel times calculated using vertical hydraulic conductivity values from a previously published regional groundwater flow model were either slightly less than or longer than those calculated using site data and ranged from 230 to 580 years.Tritium data from 1996 to 2011 USGS regional sampling of groundwater from domestic wells in the confined part of the Mahomet aquifer—which are 2.5 to about 40 miles from the Clinton site—were compared with site-specific data from a production well at the Clinton site. Tritium-based groundwater-age estimates indicated predominantly pre- 1953 recharge dates for USGS and other prior regional samples of groundwater from domestic wells in the Mahomet aquifer. These results agreed with the tritium-based, pre-1953 recharge age estimated for a groundwater sample and a sequential replicate sample from a production well in the confined part of the Mahomet aquifer beneath the Clinton site.The regional tritium-based groundwater age estimates also were compared with pesticide detections in samples from distal domestic wells in the USGS regional network that are about 2.5 to 40 miles from the Clinton site to identify whether very small amounts of post-1952 recharge have in places reached confined parts of the Mahomet aquifer at locations other than the Clinton site in an approximately 2,000 square mile area of the Mahomet aquifer. Very small amounts of post-1952 recharge were defined in this analysis as less than about 2.5 percent of the total recharge contributing to a groundwater sample, based on results from the two-part mixing analysis of tritium data from the Clinton site. Pesticide-based groundwater-age estimates based on 22 detections of pesticides (13 of these detections were estimated concentrations), including atrazine, deethylatrazine (2-Chloro-4-isopropylamino-6-amino- s-triazine), cyanazine, diazinon, metolachlor, molinate, prometon, and trifluralin in groundwater samples from 10 domestic wells 2.5 to about 40 miles distant from the Clinton site indicate that very small amounts of post-1956 to post-1992 recharge can in places reach the confined part of the Mahomet aquifer in other parts of central Illinois. The relative lack of tritium in these samples indicate that the amounts of post-1956 to post-1992 recharge contributing to the 10 domestic wells were a very small part of the overall older groundwater sampled from those wells.The flow process by which very small amounts of pesticide-bearing groundwater reached the screened intervals of the 10 domestic wells could not be distinguished between well-integrity related infiltration and natural hydrogeologic features. Potential explanations include: (1) infiltration through man-made avenues in or along the well, (2) flow of very small amounts of post-1956 to post-1992 recharge through sparsely distributed natural permeable aspects of the glacial till and diluted by mixing with older groundwater, or (3) a combination of both processes.Presuming the domestic wells sampled by the USGS in 1996–2011 in the regional study of the confined part of the Mahomet aquifer are adequately sealed and produce groundwater that is representative of aquifer conditions, the regional tritium and pesticide-based groundwater-age results indicate substantial heterogeneity in the glacial stratigraphy above the Mahomet aquifer. The pesticide-based groundwater-age estimates from the domestic wells distant from the Clinton site also indicate that parts of the Mahomet aquifer with the pesticide detections can be susceptible to contaminant sources at the land surface. The regional pesticide and tritium results from the domestic wells further indicate that a potential exists for possible contaminants from land surface to be transported through the glacial drift deposits that confine the Mahomet aquifer in other parts of central Illinois at faster rates than those computed for recharge at the Clinton site, including CLU#3. This analysis indicates the potential value of sub-microgram-per-liter level concentrations of land-use derived indicators of modern recharge to indicate the presence of very small amounts of modern, post-1952 age recharge in overall older, pre-1953 age groundwater.

Geohydrology of Storage Unit III and a combined flow model of the Santa Barbara and foothill ground-water basins, Santa Barbara County, California

USGS Publications Warehouse

Freckleton, John R.; Martin, Peter; Nishikawa, Tracy

1998-01-01

The city of Santa Barbara pumps most of its ground water from the Santa Barbara and Foothill ground-water basins. The Santa Barbara basin is subdivided into two storage units: Storage Unit I and Storage Unit III. The Foothill basin and Storage Unit I of the Santa Barbara basin have been studied extensively and ground-water flow models have been developed for them. In this report, the geohydrology of the Santa Barbara ground- water basin is described with a special emphasis on Storage Unit III in the southwestern part of the basin. The purposes of this study were to summarize and evaluate the geohydrology of Storage Unit III and to develop an areawide model of the Santa Barbara and Foothill basins that includes the previously unmodeled Storage Unit III. Storage Unit III is in the southwestern part of the city of Santa Barbara. It is approximately 3.5 miles long and varies in width from about 2,000 feet in the southeast to 4,000 feet in the north-west. Storage Unit III is composed of the Santa Barbara Formation and overlying alluvium. The Santa Barbara Formation (the principal aquifer) consists of Pleistocene and Pliocene(?) unconsolidated marine sand, silt, and clay, and it has a maximum saturated thickness of about 160 feet. The alluvium that overlies the Santa Barbara Formation has a maximum saturated thickness of about 140 feet. The storage unit is bounded areally by faults and low-permeability deposits and is underlain by rocks of Tertiary age. The main sources of recharge to Storage Unit III are seepage from Arroyo Burro and infiltration of precipitation. Most of the recharge occurs in the northwest part of the storage unit, and ground water flows toward the southeast along the unit's long axis. Lesser amounts of recharge may occur as subsurface flow from the Hope Ranch subbasin and as upwelling from the underlying Tertiary rocks. Discharge from Storage Unit III occurs as pumpage, flow to underground drains, underflow through alluvium in the vicinity of Arroyo Burro across the Lavigia Fault, evapotranspiration, and underflow to the Pacific Ocean. The faults that bound Storage Unit III generally are considered to be effective barriers to the flow of ground water. Interbasin ground-water flow occurs where deposits of younger alluvium along stream channels cross faults. Ground-water quality in Storage Unit III deposits varies with location and depth. Upward leakage of poor-quality water from the underlying Tertiary rocks occurs in the storage unit, and such leakage can be influenced by poor well construction or by heavy localized pumping. The highest dissolved-solids concentration (4,710 milligrams per liter) in ground water resulting from this upward leakage is found in the coastal part of the storage unit. The ground-water system was modeled as two horizontal layers. In the Foothill basin and Storage Unit I the layers are separated by a confining bed. The upper layer represents the upper producing zone and the shallow zone near the coast. The lower layer represents the lower producing zone. In general, the faults in the study area were assumed to be no-flow boundaries, except for the offshore fault that forms the southeast boundary; the southeast boundary was simulated as a general-head boundary. The Storage Unit III model was combined with the preexisting Storage Unit I and Foothill basin models, using horizontal flow barriers, to form an areawide model. The areawide model was calibrated by simulating steady-state predevelopment conditions and transient conditions for 1978-92. The nonpumping steady- state simulation was used to verify that the calibrated model yielded physically reasonable results for predevelopment conditions. The calibrated areawide model calculates water levels in Storage Unit III that are within 10 feet of measured water levels at all sites of comparison. In addition, the model adequately simulates water levels in the Storage Unit I and Foothill basin areas. A total of 33,430 acre-feet of water was pum

Hydrogeologic framework, ground-water quality, and simulation of ground-water flow at the Fair Lawn Well Field Superfund site, Bergen County, New Jersey

USGS Publications Warehouse

Lewis-Brown, Jean C.; Rice, Donald E.; Rosman, Robert; Smith, Nicholas P.

2005-01-01

Production wells in the Westmoreland well field, Fair Lawn, Bergen County, New Jersey (the 'Fair Lawn well field Superfund site'), are contaminated with volatile organic compounds, particularly trichloroethylene, tetrachloroethylene, and 1,1,1-trichloroethane. In 1983, the U.S. Environmental Protection Agency (USEPA) placed the Westmoreland well field on its National Priority List of Superfund sites. In an effort to determine ground-water flow directions, contaminant-plume boundaries, and contributing areas to production wells in Fair Lawn, and to evaluate the effect of present pump-and-treat systems on flowpaths of contaminated ground water, the U.S. Geological Survey (USGS), in cooperation with the USEPA, developed a conceptual hydrogeologic framework and ground-water flow model of the study area. MODFLOW-2000, the USGS three-dimensional finite-difference model, was used to delineate contributing areas to production wells in Fair Lawn and to compute flowpaths of contaminated ground water from three potential contaminant sources to the Westmoreland well field. Straddle-packer tests were used to determine the hydrologic framework of, distribution of contaminants in, and hydrologic properties of water-bearing and confining units that make up the fractured-rock aquifer underlying the study area. The study area consists of about 15 square miles in and near Fair Lawn. The area is underlain by 6 to 100 feet of glacial deposits and alluvium that, in turn, are underlain by the Passaic Formation. In the study area, the Passaic Formation consists of brownish-red pebble conglomerate, medium- to coarse-grained feldspathic sandstone, and micaceous siltstone. The bedrock strata strike N. 9o E. and dip 6.5o to the northwest. The bedrock consists of alternating layers of densely fractured rocks and sparsely fractured rocks, forming a fractured-rock aquifer. Ground-water flow in the fractured-rock aquifer is anisotropic as a result of the interlayering of dipping water-bearing and confining units. Wells of similar depth aligned along the strike of the bedding intersect the same water-bearing units, but wells aligned along the dip of the bedding may intersect different water-bearing units. Consequently, wells aligned along strike are in greater hydraulic connection than wells aligned along dip. The Borough of Fair Lawn pumps approximately 770 million gallons per year from 13 production wells. Hydrographs from six observation wells ranging in depth from 162 to 505 feet in Fair Lawn show that water levels in much of the study area are affected by pumping. Straddle packers were used to isolate discrete intervals within six open-hole observation wells owned by the Fair Lawn Water Department. Transmissivity, water-quality, and static-water-level data were obtained from the isolated intervals. Measured transmissivity ranged from near 0 to 8,900 feet squared per day. The broad range in measured transmissivity is a result of the heterogeneity of the fractured-rock aquifer. Eight water-bearing units and eight confining units were identified in the study area on the basis of transmissivity. The water-bearing units range in thickness from 21 to 95 feet; the mean thickness is 50 feet. The confining units range in thickness from 22 to 248 feet; the mean thickness is 83 feet. Water-level and water-quality data indicate effective separation of water-bearing units by the confining units. Water-quality samples were collected from the six observation wells at 16 depth intervals isolated by the straddle packers in 2000 and 2001. Concentrations of volatile organic compounds generally were low in samples from four of the wells, but were higher in samples from a well in Fair Lawn Industrial Park and in a well in the Westmoreland well field. The digital ground-water flow model was used to simulate steady-state scenarios representing conditions in the study area in 1991 and 2000. These years were chosen because during the intervening period,

Remediation by Natural Attenuation Treatability Study for Operable Unit 5

DTIC Science & Technology

1997-12-01

remaining as a result of all attenuation processes is equivalent to the fraction of contaminant remaining as a result of non - destructive attenuation...Alternative 1-- RNA Combined with LTM, Institutional Controls , Air Sparging Along Main Street, and Groundwater Extraction and Treatment Near Well Pair MW137...MW138 .............................. 6-4 6.3.2 Alternative 2 -- RNA, LTM, Institutional Controls , Air Sparging along Main Street, Groundwater

Numerical analysis of the hydrogeologic controls in a layered coastal aquifer system, Oahu, Hawaii, USA

USGS Publications Warehouse

Oki, D.S.; Souza, W.R.; Bolke, E.L.; Bauer, G.R.

1998-01-01

The coastal aquifer system of southern Oahu, Hawaii, USA, consists of highly permeable volcanic aquifers overlain by weathered volcanic rocks and interbedded marine and terrestrial sediments of both high and low permeability. The weathered volcanic rocks and sediments are collectively known as caprock, because they impede the free discharge of groundwater from the underlying volcanic aquifers. A cross-sectional groundwater flow and transport model was used to evaluate the hydrogeologic controls on the regional flow system in southwestern Oahu. Controls considered were: (a) overall caprock hydraulic conductivity; and (b) stratigraphic variations of hydraulic conductivity in the caprock. Within the caprock, variations in hydraulic conductivity, caused by stratigraphy or discontinuities of the stratigraphic units, are a major control on the direction of groundwater flow and the distribution of water levels and salinity. Results of cross-sectional modeling confirm the general groundwater flow pattern that would be expected in a layered coastal system. Ground-water flow is: (a) predominantly upward in the low-permeability sedimentary units; and (b) predominantly horizontal in the high-permeability sedimentary units.

Status and understanding of groundwater quality in the Monterey Bay and Salinas Valley Basins, 2005-California GAMA Priority Basin Project

USGS Publications Warehouse

Kulongoski, Justin T.; Belitz, Kenneth

2011-01-01

Groundwater quality in the approximately 1,000 square mile (2,590 km2) Monterey Bay and Salinas Valley Basins (MS) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in central California in Monterey, Santa Cruz, and San Luis Obispo Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA MS study was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer systems (hereinafter referred to as primary aquifers). The assessment is based on water-quality and ancillary data collected in 2005 by the USGS from 97 wells and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifers were defined by the depth intervals of the wells listed in the CDPH database for the MS study unit. The quality of groundwater in the primary aquifers may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources in the primary aquifers of the MS study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than (>) 1.0 indicates a concentration greater than a benchmark, and less than or equal to (≤) 1.0 indicates a concentration less than or equal to a benchmark. Relative-concentrations of organic and special interest constituents [perchlorate, N-nitrosodimethylamine (NDMA), and 1,2,3-trichloropropane (1,2,3-TCP)], were classified as "high" (relative-concentration > 1.0), "moderate" (0.1 1.0), "moderate" (0.5 < relative-concentration ≤ 1.0), or "low" (relative-concentration ≤ 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion was defined as the percentage of the area of the primary aquifers with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifers with moderate and low relative-concentrations, respectively. Two statistical approaches-grid-based and spatially weighted-were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially-weighted estimates were comparable in the MS study unit (within 90-percent confidence intervals). Inorganic constituents with human-health benchmarks were detected at high relative-concentrations in 14.5 percent of the primary aquifers, moderate in 35.5 percent, and low in 50.0 percent. High aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of nitrate (7.9 percent), molybdenum (2.9 percent), arsenic (2.8 percent), boron (1.9 percent), and gross alpha-beta radioactivity (1.5 percent). Relative-concentrations of organic constituents (one or more) were high in 0.2 percent, moderate in 6.6 percent, and low in 93.2 percent (not detected in 48.1 percent) of the primary aquifers. The high aquifer-scale proportion of organic constituents primarily reflected high aquifer-scale proportions of tetrachloroethene (0.1 percent) and methyl tert-butyl ether (0.1 percent). Relative-concentration for inorganic constituents with secondary maximum contaminant levels, manganese, total dissolved solids, iron, sulfate, and chloride were high in 18.6, 8.6, 7.1, 2.9, and 1.4 percent of the primary aquifers, respectively. Of the 205 organic and special-interest constituents analyzed, 32 constituents were detected. One organic constituent, the herbicide simazine, was frequently detected (in 10 percent or more of samples), but was detected at low relative-concentrations. The second component of this study, the understanding assessment, identified the natural and human factors that affect groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. Results from these evaluations were used to explain the occurrence and distribution of constituents in the study unit. The understanding assessment indicated that most wells that contained nitrate were classified as being in agricultural land-use areas, and depths to the top of perforations in most of the wells were less than 350 ft (76 m). High and moderate relative-concentrations of arsenic may be attributed to reductive dissolution of manganese or iron oxides, or to desorption or inhibition of arsenic sorption under alkaline conditions. Arsenic concentrations increased with increasing groundwater depth and residence time (age). Simazine was detected more often in groundwater from wells with surrounding land use classified as agricultural or urban, and with top of perforation depths less than 200 ft (61 m), than in groundwater from wells with natural land use or with deeper depths. Tritium, helium-isotope, and carbon-14 data were used to classify the predominant age of groundwater samples into three categories: modern (water that has entered the aquifer since 1953), pre-modern (water that entered the aquifer prior to 1953 to tens of thousands of years ago), and mixed (mixtures of modern- and pre-modern-age waters). Arsenic concentrations were significantly greater in groundwater with pre-modern age classification than in groundwater with modern-age classification, suggesting that arsenic accumulates with groundwater residence time.

Managed aquifer recharge by a check dam to improve the quality of fluoride-rich groundwater: a case study from southern India.

PubMed

Gowrisankar, G; Jagadeshan, G; Elango, L

2017-04-01

In many regions around the globe, including India, degradation in the quality of groundwater is of great concern. The objective of this investigation is to determine the effect of recharge from a check dam on quality of groundwater in a region of Krishnagiri District of Tamil Nadu State, India. For this study, water samples from 15 wells were periodically obtained and analysed for major ions and fluoride concentrations. The amount of major ions present in groundwater was compared with the drinking water guideline values of the Bureau of Indian Standards. With respect to the sodium and fluoride concentrations, 38% of groundwater samples collected was not suitable for direct use as drinking water. Suitability of water for agricultural use was determined considering the electrical conductivity, sodium adsorption ratio, sodium percentage, permeability index, Wilcox and United States Salinity Laboratory diagrams. The influence of freshwater recharge from the dam is evident as the groundwater in wells nearer to the check dam was suitable for both irrigation and domestic purposes. However, the groundwater away from the dam had a high ionic composition. This study demonstrated that in other fluoride-affected areas, the concentration can be reduced by dilution with the construction of check dams as a measure of managed aquifer recharge.

Three-dimensional hydrogeologic framework model for use with a steady-state numerical ground-water flow model of the Death Valley regional flow system, Nevada and California

USGS Publications Warehouse

Belcher, Wayne R.; Faunt, Claudia C.; D'Agnese, Frank A.

2002-01-01

The U.S. Geological Survey, in cooperation with the Department of Energy and other Federal, State, and local agencies, is evaluating the hydrogeologic characteristics of the Death Valley regional ground-water flow system. The ground-water flow system covers an area of about 100,000 square kilometers from latitude 35? to 38?15' North to longitude 115? to 118? West, with the flow system proper comprising about 45,000 square kilometers. The Death Valley regional ground-water flow system is one of the larger flow systems within the Southwestern United States and includes in its boundaries the Nevada Test Site, Yucca Mountain, and much of Death Valley. Part of this study includes the construction of a three-dimensional hydrogeologic framework model to serve as the foundation for the development of a steady-state regional ground-water flow model. The digital framework model provides a computer-based description of the geometry and composition of the hydrogeologic units that control regional flow. The framework model of the region was constructed by merging two previous framework models constructed for the Yucca Mountain Project and the Environmental Restoration Program Underground Test Area studies at the Nevada Test Site. The hydrologic characteristics of the region result from a currently arid climate and complex geology. Interbasinal regional ground-water flow occurs through a thick carbonate-rock sequence of Paleozoic age, a locally thick volcanic-rock sequence of Tertiary age, and basin-fill alluvium of Tertiary and Quaternary age. Throughout the system, deep and shallow ground-water flow may be controlled by extensive and pervasive regional and local faults and fractures. The framework model was constructed using data from several sources to define the geometry of the regional hydrogeologic units. These data sources include (1) a 1:250,000-scale hydrogeologic-map compilation of the region; (2) regional-scale geologic cross sections; (3) borehole information, and (4) gridded surfaces from a previous three-dimensional geologic model. In addition, digital elevation model data were used in conjunction with these data to define ground-surface altitudes. These data, properly oriented in three dimensions by using geographic information systems, were combined and gridded to produce the upper surfaces of the hydrogeologic units used in the flow model. The final geometry of the framework model is constructed as a volumetric model by incorporating the intersections of these gridded surfaces and by applying fault truncation rules to structural features from the geologic map and cross sections. The cells defining the geometry of the hydrogeologic framework model can be assigned several attributes such as lithology, hydrogeologic unit, thickness, and top and bottom altitudes.

Role of aquifer heterogeneity in fresh groundwater discharge and seawater recycling: An example from the Carmel coast, Israel

USGS Publications Warehouse

Weinstein, Y.; Burnett, W.C.; Swarzenski, P.W.; Shalem, Y.; Yechieli, Y.; Herut, B.

2007-01-01

A case study is shown in which the pattern of submarine groundwater discharge and of seawater recycling is controlled by local hydrogeological variability. The coastal aquifer in Dor Bay is composed of two units: a partly confined calcaranitic sandstone (Kurkar) and an overlying loose sand. Groundwater in the Kurkar has elevated activities of 222Rn (∼390 dpm/L) and relatively low 224Ra/223Ra activity ratios (3–4), while the sand groundwater is significantly less radiogenic (6–90 dpm/L) and shows higher 224Ra/223Ra ratios. Groundwater discharging from sand-covered areas of the bay has salinities of 16–31 and an average 222Rn activity of 168 dpm/L, which lies on a mixing line between Rn-rich Kurkar fresh water and Rn-poor seawater. Another key observation is that seawater infiltrates to some extent into onshore sand groundwater, while the fresh water within the submarine Kurkar can be traced up to 40 m offshore. This implies that while fresh water mainly discharges from the Kurkar unit, seawater recycling is limited to the loose sand, and that the discharge from sand-covered areas is a mixture of Kurkar water with recycled seawater. Advection rates from the bay floor were calculated from Rn time series and found to vary between 0 and 36 cm/d, correlating negatively with bay water depth. The average flux was 8.1 cm/d, and it did not seem to change much during March, May, and July 2006. The average amount of fresh water discharging to the bay was 5.0 m3/d per meter of shoreline. Radon activity in the sand groundwater also fluctuates due to influx of Kurkar-type groundwater.

Groundwater availability in the United States: the value of quantitative regional assessments

USGS Publications Warehouse

Dennehy, Kevin F.; Reilly, Thomas E.; Cunningham, William L.

2015-01-01

The sustainability of water resources is under continued threat from the challenges associated with a growing population, competing demands, and a changing climate. Freshwater scarcity has become a fact in many areas. Much of the United States surface-water supplies are fully apportioned for use; thus, in some areas the only potential alternative freshwater source that can provide needed quantities is groundwater. Although frequently overlooked, groundwater serves as the principal reserve of freshwater in the US and represents much of the potential supply during periods of drought. Some nations have requirements to monitor and characterize the availability of groundwater such as the European Union’s Water Framework Directive (EPCEU 2000). In the US there is no such national requirement. Quantitative regional groundwater availability assessments, however, are essential to document the status and trends of groundwater availability for the US and make informed water-resource decisions possible now and in the future. Barthel (2014) highlighted that the value of regional groundwater assessments goes well beyond just quantifying the resource so that it can be better managed. The tools and techniques required to evaluate these unique regional systems advance the science of hydrogeology and provide enhanced methods that can benefit local-scale groundwater investigations. In addition, a significant, yet under-utilized benefit is the digital spatial and temporal data sets routinely generated as part of these studies. Even though there is no legal or regulatory requirement for regional groundwater assessments in the US, there is a logical basis for their implementation. The purpose of this essay is to articulate the rationale for and reaffirm the value of regional groundwater assessments primarily in the US; however, the arguments hold for all nations. The importance of the data sets and the methods and model development that occur as part of these assessments is stressed. These high-value data sets and models should be available in readily accessible formats for use today and in the future. Examples of advances in and accomplishments of two regional groundwater assessments are presented to demonstrate their function, relevance, and value for determining the sustainability of the groundwater resources of the US.

Transboundary study of the Milk River aquifer (Canada, USA): geological, conceptual and numerical models for the sound management of the regional groundwater resources

NASA Astrophysics Data System (ADS)

Pétré, Marie-Amélie; Rivera, Alfonso; Lefebvre, René

2016-04-01

The Milk River transboundary aquifer straddles southern Alberta (Canada) and northern Montana (United States), a semi-arid and water-short region. The extensive use of this regional sandstone aquifer over the 20th century has led to a major drop in water levels locally, and concerns about the durability of the resources have been raised since the mid-1950. Even though the Milk River Aquifer (MRA) has been studied for decades, most of the previous studies were limited by the international border, preventing a sound understanding of the aquifer dynamics. Yet, a complete portrait of the aquifer is required for proper management of this shared resource. The transboundary study of the MRA aims to overcome transboundary limitations by providing a comprehensive characterization of the groundwater resource at the aquifer scale, following a three-stage approach: 1) The development of a 3D unified geological model of the MRA (50,000 km2). The stratigraphic framework on both sides of the border was harmonized and various sources of geological data were unified to build the transboundary geological model. The delineation of the aquifer and the geometry and thicknesses of the geological units were defined continuously across the border. 2) Elaboration of a conceptual hydrogeological model by linking hydrogeological and geochemical data with the 3D unified geological model. This stage is based on a thorough literature review and focused complementary field work on both sides of the border. The conceptual model includes the determination of the groundwater flow pattern, the spatial distribution of hydraulic properties, a groundwater budget and the definition of the groundwater types. Isotopes (3H, 14C, 36Cl) were used to delineate the recharge area as well as the active and low-flow areas. 3) The building of a 3D numerical groundwater flow model of the MRA (26,000 km2). This model is a transposition of the geological and hydrogeological conceptual models. A pre-exploitation steady-state model and a subsequent transient numerical model with several exploitation scenarios were developed. The numerical model aims to test the conceptual model and to provide a basis to assess the best possible uses of this valuable resource that is shared by Canada and the United States of America. This study provides a unique approach with scientific tools for proper aquifer assessment and groundwater management at the aquifer scale, not interrupted by a jurisdictional boundary. These tools are combined and integrated into three models, which together will form the basis of reliable sustainable groundwater and aquifer management in cooperation, thus facilitating the creation of a system of transboundary water governance based on scientific knowledge.

Seasonal forecasting of groundwater levels in natural aquifers in the United Kingdom

NASA Astrophysics Data System (ADS)

Mackay, Jonathan; Jackson, Christopher; Pachocka, Magdalena; Brookshaw, Anca; Scaife, Adam

2014-05-01

Groundwater aquifers comprise the world's largest freshwater resource and provide resilience to climate extremes which could become more frequent under future climate changes. Prolonged dry conditions can induce groundwater drought, often characterised by significantly low groundwater levels which may persist for months to years. In contrast, lasting wet conditions can result in anomalously high groundwater levels which result in flooding, potentially at large economic cost. Using computational models to produce groundwater level forecasts allows appropriate management strategies to be considered in advance of extreme events. The majority of groundwater level forecasting studies to date use data-based models, which exploit the long response time of groundwater levels to meteorological drivers and make forecasts based only on the current state of the system. Instead, seasonal meteorological forecasts can be used to drive hydrological models and simulate groundwater levels months into the future. Such approaches have not been used in the past due to a lack of skill in these long-range forecast products. However systems such as the latest version of the Met Office Global Seasonal Forecast System (GloSea5) are now showing increased skill up to a 3-month lead time. We demonstrate the first groundwater level ensemble forecasting system using a multi-member ensemble of hindcasts from GloSea5 between 1996 and 2009 to force 21 simple lumped conceptual groundwater models covering most of the UK's major aquifers. We present the results from this hindcasting study and demonstrate that the system can be used to forecast groundwater levels with some skill up to three months into the future.

Regional analysis of ground-water recharge: Chapter B in Ground-water recharge in the arid and semiarid southwestern United States (Professional Paper 1703)

USGS Publications Warehouse

Flint, Lorraine E.; Flint, Alan L.; Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

2007-01-01

A modeling analysis of runoff and ground-water recharge for the arid and semiarid southwestern United States was performed to investigate the interactions of climate and other controlling factors and to place the eight study-site investigations into a regional context. A distributed-parameter water-balance model (the Basin Characterization Model, or BCM) was used in the analysis. Data requirements of the BCM included digital representations of topography, soils, geology, and vegetation, together with monthly time-series of precipitation and air-temperature data. Time-series of potential evapotranspiration were generated by using a submodel for solar radiation, taking into account topographic shading, cloudiness, and vegetation density. Snowpack accumulation and melting were modeled using precipitation and air-temperature data. Amounts of water available for runoff and ground-water recharge were calculated on the basis of water-budget considerations by using measured- and generated-meteorologic time series together with estimates of soil-water storage and saturated hydraulic conductivity of subsoil geologic units. Calculations were made on a computational grid with a horizontal resolution of about 270 meters for the entire 1,033,840 square-kilometer study area. The modeling analysis was composed of 194 basins, including the eight basins containing ground-water recharge-site investigations. For each grid cell, the BCM computed monthly values of potential evapotranspiration, soil-water storage, in-place ground-water recharge, and runoff (potential stream flow). A fixed percentage of runoff was assumed to become recharge beneath channels operating at a finer resolution than the computational grid of the BCM. Monthly precipitation and temperature data from 1941 to 2004 were used to explore climatic variability in runoff and ground-water recharge.The selected approach provided a framework for classifying study-site basins with respect to climate and dominant recharge processes. The average climate for all 194 basins ranged from hyperarid to humid, with arid and semiarid basins predominating (fig. 6, chapter A, this volume). Four of the 194 basins had an aridity index of dry subhumid; two of the basins were humid. Of the eight recharge-study sites, six were in semiarid basins, and two were in arid basins. Average-annual potential evapotranspiration showed a regional gradient from less than 1 m/yr in the northeastern part of the study area to more than 2 m/yr in the southwestern part of the study area. Average-annual precipitation was lowest in the two arid-site basins and highest in the two study-site basins in southern Arizona. The relative amount of runoff to in-place recharge varied throughout the study area, reflecting differences primarily in soil water-holding capacity, saturated hydraulic conductivity of subsoil materials, and snowpack dynamics. Climatic forcing expressed in El Niño and Pacific Decadal Oscillation indices strongly influenced the generation of precipitation throughout the study area. Positive values of both indices correlated with the highest amounts of runoff and ground-water recharge.

Chlorinated solvents in groundwater of the United States

USGS Publications Warehouse

Moran, M.J.; Zogorski, J.S.; Squillace, P.J.

2007-01-01

Four chlorinated solvents-methylene chloride, perchloroethene (PCE), 1,1,1-trichloroethane, and trichloroethene (TCE)-were analyzed in samples of groundwater taken throughout the conterminous United States by the U.S. Geological Survey. The samples were collected between 1985 and 2002 from more than 5,000 wells. Of 55 volatile organic compounds (VOCs) analyzed in groundwater samples, solvents were among the most frequently detected. Mixtures of solvents in groundwater were common and may be the result of common usage of solvents or degradation of one solvent to another. Relative to other VOCs with Maximum Contaminant Levels (MCLs), PCE and TCE ranked high in terms of the frequencies of concentrations greater than or near MCLs. The probability of occurrence of solvents in groundwater was associated with dissolved oxygen content of groundwater, sources such as urban land use and population density, and hydraulic properties of the aquifer. The results reinforce the importance of understanding the redox conditions of aquifers and the hydraulic properties of the saturated and vadose zones in determining the intrinsic susceptibility of groundwater to contamination by solvents. The results also reinforce the importance of controlling sources of solvents to groundwater. ?? 2007 American Chemical Society.

Groundwater Profession in Transition: Discovery toAdaptation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narasimhan, T.N.

2005-04-04

Over the past century and half, groundwater has played an important role in the economic prosperity of the United States. The groundwater profession which has contributed to this prosperity has grown through the contributions of the U.S. and State Geological Surveys,academia, and industry. A century ago, the energies of the profession were channeled towards discovering new sources of groundwater in a largely unexplored land, and exploiting the resources for maximum economic benefit. Experience has since revealed that groundwater systems are finite, and are intimately linked to surface water bodies and the biosphere. A consequence is that aggressive exploitation of groundwatermore » can lead to unacceptable environmental degradation and social cost. At present, the groundwater profession is in a state of transition from one of discovery and exploitation, to one of balancing resource development with avoiding unacceptable damage to the environment. This paper outlines the history of the groundwater profession in the United States since the late nineteenth century, and speculates on what may lie ahead in the near future, as the profession makes the transition from discovering new sources of groundwater to one of better understanding and adapting to nature's constraints.« less

Groundwater Profession in Transition: Discovery toAdaptation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narasimhan, T.N.

Over the past century and half, groundwater has played an important role in the economic prosperity of the United States. The groundwater profession which has contributed to this prosperity has grown through the contributions of the U.S. and State Geological Surveys,academia, and industry. A century ago, the energies of the profession were channeled towards discovering new sources of groundwater in a largely unexplored land, and exploiting the resources for maximum economic benefit. Experience has since revealed that groundwater systems are finite, and are intimately linked to surface water bodies and the biosphere. A consequence is that aggressive exploitation of groundwatermore » can lead to unacceptable environmental degradation and social cost. At present, the groundwater profession is in a state of transition from one of discovery and exploitation, to one of balancing resource development with avoiding unacceptable damage to the environment. This paper outlines the history of the groundwater profession in the United States since the late nineteenth century, and speculates on what may lie ahead in the near future, as the profession makes the transition from discovering new sources of groundwater to one of better understanding and adapting to nature's constraints.« less

Groundwater pumping by heterogeneous users

NASA Astrophysics Data System (ADS)

Saak, Alexander E.; Peterson, Jeffrey M.

2012-08-01

Farm size is a significant determinant of both groundwater-irrigated farm acreage and groundwater-irrigation-application rates per unit land area. This paper analyzes the patterns of groundwater exploitation when resource users in the area overlying a common aquifer are heterogeneous. In the presence of user heterogeneity, the common resource problem consists of inefficient dynamic and spatial allocation of groundwater because it impacts income distribution not only across periods but also across farmers. Under competitive allocation, smaller farmers pump groundwater faster if farmers have a constant marginal periodic utility of income. However, it is possible that larger farmers pump faster if the Arrow-Pratt coefficient of relative risk-aversion is sufficiently decreasing in income. A greater farm-size inequality may either moderate or amplify income inequality among farmers. Its effect on welfare depends on the curvature properties of the agricultural output function and the farmer utility of income. Also, it is shown that a flat-rate quota policy that limits the quantity of groundwater extraction per unit land area may have unintended consequences for the income distribution among farmers.

A nationwide classification of New Zealand aquifer properties

NASA Astrophysics Data System (ADS)

Westerhoff, Rogier; Tschritter, Constanze; Rawlinson, Zara; White, Paul

2017-04-01

Groundwater plays an essential role in water provision for domestic, industrial and agricultural use. Groundwater is also vital for ecology and environment, since it provides baseflow to many streams, rivers and wetlands. As groundwater is a 'hidden' resource that is typically poorly understood by the public, simple and informative maps can assist to enhance awareness for understanding groundwater and associated environmental issues. The first national aquifer map for New Zealand (2001) identified 200 aquifers at a scale of approximately 1:5 Million. Subsequently, regional councils and unitary authorities have updated their aquifer boundaries using a variety of methods. However, with increasing demand of groundwater in New Zealand and drought impacts expected to be more significant in the future, more consistent and more advanced aquifer characterisation and mapping techniques are needed to improve our understanding of the available resources. Significant resources have gone into detailed geological mapping in recent years, and the New Zealand 1:250,000 Geological Map (QMAP) was developed and released as a seamless GIS database in 2014. To date, there has been no national assessment of this significant data set for aquifer characterisation purposes. This study details the use of the QMAP lithological and chrono-stratigraphic information to develop a nationwide assessment of hydrogeological units and their properties. The aim of this study is to map hydrogeological units in New Zealand, with a long-term goal to use this as a basis for a nationally-consistent map of aquifer systems and aquifer properties (e.g., hydraulic conductivity estimates). Internationally accepted aquifer mapping studies were reviewed and a method was devised that classifies hydrogeological units based on the geological attributes of the QMAP ArcGIS polygons. The QMAP attributes used in this study were: main rock type; geological age; and secondary rock type. The method was mainly based on values of permeability after global, continental and New Zealand studies. The classification followed a tiered workflow. Tier 1 ('Hydrolithological units') consisted of the classification of only the main rock type, based on median permeability value. Tier 2 ('Hydrogeological units') consisted of a combined classification of main rock type and age, assuming that permeability shows an exponential decay over geological age. Tier 3 ('Hydrogeological units') included all three attributes, where the permeabilities of main and secondary rock types were averaged with weighting. Tier 4 was a simplification of the 10 classes in Tier 3 to four 'Aquifer Potential' classes, i.e., 'Poor', 'Low', 'Medium', and 'High'. The results show a good match with existing overlaying maps of aquifer boundaries The map is capable of refining aquifer boundaries at the regional scale where these boundaries have not been updated since 2001. Additionally, the map provides a quick and simple way to communicate hydrogeological information. This fundamental dataset is essential for future studies of the impact of climate and humans on groundwater in New Zealand. Future work will include categorising geological system knowledge (e.g., depositional environment) to allow for 3D mapping and characterisation, compilation and incorporation of nation-wide measured hydraulic conductivity values, including uncertainty, and linking with other national data sets.

Annual ground-water discharge by evapotranspiration from areas of spring-fed riparian vegetation along the eastern margin of Death Valley, 2000-02

USGS Publications Warehouse

Laczniak, Randell J.; Smith, J. LaRue; DeMeo, Guy A.

2006-01-01

Flow from major springs and seeps along the eastern margin of Death Valley serves as the primary local water supply and sustains much of the unique habitat in Death Valley National Park. Together, these major spring complexes constitute the terminus of the Death Valley Regional Ground-Water Flow System--one of the larger flow systems in the Southwestern United States. The Grapevine Springs complex is the least exploited for water supply and consequently contains the largest area of undisturbed riparian habitat in the park. Because few estimates exist that quantify ground-water discharge from these spring complexes, a study was initiated to better estimate the amount of ground water being discharged annually from these sensitive, spring-fed riparian areas. Results of this study can be used to establish a basis for estimating water rights and as a baseline from which to assess any future changes in ground-water discharge in the park. Evapotranspiration (ET) is estimated volumetrically as the product of ET-unit (general vegetation type) acreage and a representative ET rate. ET-unit acreage is determined from high-resolution multi-spectral imagery; and a representative ET rate is computed from data collected in the Grapevine Springs area using the Bowen-ratio solution to the energy budget, or from rates given in other ET studies in the Death Valley area. The ground-water component of ET is computed by removing the local precipitation component from the ET rate. Two different procedures, a modified soil-adjusted vegetation index using the percent reflectance of the red and near-infrared wavelengths and land-cover classification using multi-spectral imagery were used to delineate the ET units within each major spring-discharge area. On the basis of the more accurate procedure that uses the vegetation index, ET-unit acreage for the Grapevine Springs discharge area totaled about 192 acres--of which 80 acres were moderate-density vegetation and 112 acres were high-density vegetation. ET-unit acreage for two other discharge areas delineated in the Grapevine Springs area (Surprise Springs and Staininger Spring) totaled about 6 and 43 acres, respectively; and for the discharge areas delineated in the Furnace Creek area (Nevares Springs, Cow Creek-Salt Springs, Texas Spring, and Travertine Springs) totaled about 29, 13, 11, and 21 acres, respectively. In discharge areas other than Grapevine Springs, watering and spring diversions have altered the natural distribution of the vegetation. More...

Hydrogeologic Framework of the Yakima River Basin Aquifer System, Washington

USGS Publications Warehouse

Vaccaro, J.J.; Jones, M.A.; Ely, D.M.; Keys, M.E.; Olsen, T.D.; Welch, W.B.; Cox, S.E.

2009-01-01

The Yakima River basin aquifer system underlies about 6,200 square miles in south-central Washington. The aquifer system consists of basin-fill deposits occurring in six structural-sedimentary basins, the Columbia River Basalt Group (CRBG), and generally older bedrock. The basin-fill deposits were divided into 19 hydrogeologic units, the CRBG was divided into three units separated by two interbed units, and the bedrock was divided into four units (the Paleozoic, the Mesozoic, the Tertiary, and the Quaternary bedrock units). The thickness of the basin-fill units and the depth to the top of each unit and interbed of the CRBG were mapped. Only the surficial extent of the bedrock units was mapped due to insufficient data. Average mapped thickness of the different units ranged from 10 to 600 feet. Lateral hydraulic conductivity (Kh) of the units varies widely indicating the heterogeneity of the aquifer system. Average or effective Kh values of the water-producing zones of the basin-fill units are on the order of 1 to 800 ft/d and are about 1 to 10 ft/d for the CRBG units as a whole. Effective or average Kh values for the different rock types of the Paleozoic, Mesozoic, and Tertiary units appear to be about 0.0001 to 3 ft/d. The more permeable Quaternary bedrock unit may have Kh values that range from 1 to 7,000 ft/d. Vertical hydraulic conductivity (Kv) of the units is largely unknown. Kv values have been estimated to range from about 0.009 to 2 ft/d for the basin-fill units and Kv values for the clay-to-shale parts of the units may be as small as 10-10 to 10-7 ft/d. Reported Kv values for the CRBG units ranged from 4x10-7 to 4 ft/d. Variations in the concentrations of geochemical solutes and the concentrations and ratios of the isotopes of hydrogen, oxygen, and carbon in groundwater provided information on the hydrogeologic framework and groundwater movement. Stable isotope ratios of water (deuterium and oxygen-18) indicated dispersed sources of groundwater recharge to the CRBG and basin-fill units and that the source of surface and groundwater is derived from atmospheric precipitation. The concentrations of dissolved methane were larger than could be attributable to atmospheric sources in more than 80 percent of wells with measured methane concentrations. The concentrations of the stable isotope of carbon-13 of methane were indicative of a thermogenic source of methane. Most of the occurrences of methane were at locations several miles distant from mapped structural fault features, suggesting the upward vertical movement of thermogenic methane from the underlying bedrock may be more widespread than previously assumed or there may be a more general occurrence of unmapped (buried) fault structures. Carbon and tritium isotope data and the concentrations of dissolved constituents indicate a complex groundwater flow system with multiple contributing zones to groundwater wells and relative groundwater residence time on the order of a few tens to many thousands of years. Potential mean annual recharge for water years 1950-2003 was estimated to be about 15.6 in. or 7,149 ft3/s (5.2 million acre-ft) and includes affects of human activities such as irrigation of croplands. If there had been no human activities (predevelopment conditions) during that time period, estimated recharge would have been about 11.9 in. or 5,450 ft3/s (3.9 million acre-ft). Estimated mean annual recharge ranges from virtually zero in the dry parts of the lower basin to more than 100 in. in the humid uplands, where annual precipitation is more than 120 in. Groundwater in the different hydrogeologic units occurs under perched, unconfined, semiconfined, and confined conditions. Groundwater moves from topographic highs in the uplands to topographic low areas along the streams. The flow system in the basin-fill units is compartmentalized due to topography and geologic structure. The flow system also is compartmentalized for the CRBG units but not to as large

Evaluation of bias associated with capture maps derived from nonlinear groundwater flow models

USGS Publications Warehouse

Nadler, Cara; Allander, Kip K.; Pohll, Greg; Morway, Eric D.; Naranjo, Ramon C.; Huntington, Justin

2018-01-01

The impact of groundwater withdrawal on surface water is a concern of water users and water managers, particularly in the arid western United States. Capture maps are useful tools to spatially assess the impact of groundwater pumping on water sources (e.g., streamflow depletion) and are being used more frequently for conjunctive management of surface water and groundwater. Capture maps have been derived using linear groundwater flow models and rely on the principle of superposition to demonstrate the effects of pumping in various locations on resources of interest. However, nonlinear models are often necessary to simulate head-dependent boundary conditions and unconfined aquifers. Capture maps developed using nonlinear models with the principle of superposition may over- or underestimate capture magnitude and spatial extent. This paper presents new methods for generating capture difference maps, which assess spatial effects of model nonlinearity on capture fraction sensitivity to pumping rate, and for calculating the bias associated with capture maps. The sensitivity of capture map bias to selected parameters related to model design and conceptualization for the arid western United States is explored. This study finds that the simulation of stream continuity, pumping rates, stream incision, well proximity to capture sources, aquifer hydraulic conductivity, and groundwater evapotranspiration extinction depth substantially affect capture map bias. Capture difference maps demonstrate that regions with large capture fraction differences are indicative of greater potential capture map bias. Understanding both spatial and temporal bias in capture maps derived from nonlinear groundwater flow models improves their utility and defensibility as conjunctive-use management tools.

Hydrogeologic framework refinement, ground-water flow and storage, water-chemistry analyses, and water-budget components of the Yuma area, southwestern Arizona and southeastern California

USGS Publications Warehouse

Dickinson, Jesse; Land, Michael; Faunt, Claudia C.; Leake, S.A.; Reichard, Eric G.; Fleming, John B.; Pool, D.R.

2006-01-01

The ground-water and surface-water system in the Yuma area in southwestern Arizona and southeastern California is managed intensely to meet water-delivery requirements of customers in the United States, to manage high ground-water levels in the valleys, and to maintain treaty-mandated water-quality and quantity requirements of Mexico. The following components in this report, which were identified to be useful in the development of a ground-water management model, are: (1) refinement of the hydrogeologic framework; (2) updated water-level maps, general ground-water flow patterns, and an estimate of the amount of ground water stored in the mound under Yuma Mesa; (3) review and documentation of the ground-water budget calculated by the Bureau of Reclamation, U.S. Department of the Interior (Reclamation); and (4) water-chemistry characterization to identify the spatial distribution of water quality, information on sources and ages of ground water, and information about the productive-interval depths of the aquifer. A refined three-dimensional digital hydrogeologic framework model includes the following hydrogeologic units from bottom to top: (1) the effective hydrologic basement of the basin aquifer, which includes the Pliocene Bouse Formation, Tertiary volcanic and sedimentary rocks, and pre-Tertiary metamorphic and plutonic rocks; (2) undifferentiated lower units to represent the Pliocene transition zone and wedge zone; (3) coarse-gravel unit; (4) lower, middle, and upper basin fill to represent the upper, fine-grained zone between the top of the coarse-gravel unit and the land surface; and (5) clay A and clay B. Data for the refined model includes digital elevation models, borehole lithology data, geophysical data, and structural data to represent the geometry of the hydrogeologic units. The top surface of the coarse-gravel unit, defined by using borehole and geophysical data, varies similarly to terraces resulting from the down cutting of the Colorado River. Clay A is nearly the same as the previous conceptual hydrogeologic model definition (Olmsted and others, 1973), except for a minor westward extension from the city of Yuma. Clay B is extended to the southerly international boundary and increased in areal extent by about two-thirds of the original extent (Olmsted and others, 1973). The other hydrogeologic units generally are the same as in the previous conceptual hydrogeologic model. Before development, the Colorado and Gila Rivers were the sources of nearly all the ground water in the Yuma area through direct infiltration of water from river channels and annual overbank flooding. After construction of upstream reservoirs and clearing and irrigation of the floodplains, the rivers now act as drains for the ground water. Ground-water levels in most of the Yuma area are higher now than they were in predevelopment time. A general gradient of ground-water flow toward the natural discharge area south of the Yuma area still exists, but many other changes in flow are evident. Ground water in Yuma Valley once flowed away from the Colorado River, but now has a component of flow towards the river and Mexicali Valley. A ground-water mound has formed under Yuma Mesa from long-term surface-water irrigation; about 600,000 to 800,000 acre-ft of water are stored in the mound. Ground-water withdrawals adjacent to the southerly international boundary have resulted in water-level declines in that area. The reviewed and documented water budget includes the following components: (1) recharge in irrigated areas, (2) evapotranspiration by irrigated crops and phreatophytes, (3) ground-water return flow to the Colorado River, and (4) ground-water withdrawals (including those in Mexicali Valley). Recharge components were calculated by subtracting the amount of water used by crops from the amount of water delivered. Evapotranspiration rates were calculated on the basis of established methods, thus were appropriate for input to the ground-wate

Status and understanding of groundwater quality in the San Francisco Bay groundwater basins, 2007—California GAMA Priority Basin Project

USGS Publications Warehouse

Parsons, Mary C.; Kulongoski, Justin T.; Belitz, Kenneth

2013-01-01

Groundwater quality in the approximately 620-square-mile (1,600-square-kilometer) San Francisco Bay study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in the Southern Coast Ranges of California, in San Francisco, San Mateo, Santa Clara, Alameda, and Contra Costa Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA San Francisco Bay study was designed to provide a spatially unbiased assessment of the quality of untreated groundwater within the primary aquifer system, as well as a statistically consistent basis for comparing water quality throughout the State. The assessment is based on water-quality and ancillary data collected by the USGS from 79 wells in 2007 and is supplemented with water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system is defined by the depth interval of the wells listed in the CDPH database for the San Francisco Bay study unit. The quality of groundwater in shallower or deeper water-bearing zones may differ from that in the primary aquifer system; shallower groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. Water- quality data from the CDPH database also were incorporated for this assessment. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifer system of the San Francisco Bay study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California benchmarks. A relative-concentration greater than (>) 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to (≤) 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic and special-interest constituents were classified as low (relative- concentration ≤ 0.1), moderate (0.1 1.0). Inorganic constituent relative- concentrations were classified as low (relative-concentration ≤ 0.5), moderate (0.5 1.0). A lower threshold value of relative-concentration was used to distinguish between low and moderate values of organic constituents because organic constituents are generally less prevalent and have smaller relative-concentrations than naturally occurring inorganic constituents. Aquifer-scale proportion was used as the metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the primary aquifer system that has relative-concentration greater than 1.0 for a particular constituent or class of constituents; proportion is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentages of the primary aquifer system that have moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportion for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the San Francisco Bay study unit (90-percent confidence intervals). Inorganic constituents with health-based benchmarks were present at high relative-concentrations in 5.1 percent of the primary aquifer system, and at moderate relative-concentrations in 25 percent. The high aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of barium (3.0 percent) and nitrate (2.1 percent). Inorganic constituents with secondary maximum contaminant levels were present at high relative-concentrations in 14 percent of the primary aquifer system and at moderate relative-concentrations in 33 percent. The constituents present at high relative-concentrations included total dissolved solids (7.0 percent), chloride (6.1 percent), manganese (12 percent), and iron (3.0 percent). Organic constituents with health-based benchmarks were present at high relative-concentrations in 0.6 percent and at moderate relative-concentrations in 12 percent of the primary aquifer system. Of the 202 organic constituents analyzed for, 32 were detected. Three organic constituents were frequently detected (in 10 percent or more of samples): the trihalomethane chloroform, the solvent 1,1,1-trichloroethane and the refrigerant 1,1,2-trichlorotrifluoroethane. One special-interest constituent, perchlorate, was detected at moderate relative-concentrations in 42 percent of the primary aquifer system. The second component of this work, the understanding assessment, identified some of the primary natural and human factors that may affect groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. Results from these evaluations were used to explain the occurrence and distribution of constituents in the study unit.

Hydrologic Data for the Groundwater Flow and Contaminant Transport Model of Corrective Action Units 101 and 102: Central and Western Pahute Mesa, Nye County, Nevada, Revision 0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drici, Warda

2004-02-01

This report documents the analysis of the available hydrologic data conducted in support of the development of a Corrective Action Unit (CAU) groundwater flow model for Central and Western Pahute Mesa: CAUs 101 and 102.

The quality of our Nation's waters: Water quality in principal aquifers of the United States, 1991-2010

USGS Publications Warehouse

DeSimone, Leslie A.; McMahon, Peter B.; Rosen, Michael R.

2015-01-01

About 130 million people in the United States rely on groundwater for drinking water, and the need for high-quality drinking-water supplies becomes more urgent as our population grows. Although groundwater is a safe, reliable source of drinking water for millions of people nationwide, high concentrations of some chemical constituents can pose potential human-health concerns. Some of these contaminants come from the rocks and sediments of the aquifers themselves, and others are chemicals that we use in agriculture, industry, and day-to-day life. When groundwater supplies are contaminated, millions of dollars can be required for treatment so that the supplies can be usable. Contaminants in groundwater can also affect the health of our streams and valuable coastal waters. By knowing where contaminants occur in groundwater, what factors control contaminant concentrations, and what kinds of changes in groundwater quality might be expected in the future, we can ensure the availability and quality of this vital natural resource in the future.

Water quality analysis of groundwater in crystalline basement rocks, Northern Ghana

USGS Publications Warehouse

Anku, Y.S.; Banoeng-Yakubo, B.; Asiedu, D.K.; Yidana, S.M.

2009-01-01

Hydrochemical data are presented for groundwater samples, collected from fractured aquifers in parts of northern Ghana. The data was collected to assess the groundwater suitability for domestic and agricultural use. Results of the study reveal that the pH of the groundwater in the area is slightly acidic to slightly alkaline. The electrical conductivity values, total dissolved solids (TDS) values and calcium, magnesium and sodium concentrations in the groundwater are generally below the limit set by the WHO for potable water supply. On the basis of activity diagrams, groundwater from the fractured aquifers appears to be stable within the montmorillonite field, suggesting weathering of silicate minerals. An inverse distance weighting interpolator with a power of 2 was applied to the data points to produce prediction maps for nitrate and fluoride. The distribution maps show the presence of high nitrate concentrations (50-194??mg/l) in some of the boreholes in the western part of the study area indicating anthropogenic impact on the groundwater. Elevated fluoride level (1.5-4??mg/l), higher than the WHO allowable fluoride concentration of 1.5, is recorded in the groundwater underlying the northeastern part of the study area, more specifically Bongo and its surrounding communities of the Upper East region. Results of this study suggest that groundwater from the fractured aquifers in the area exhibit low sodicity-low salinity (S1-C1), low sodicity-medium salinity (S1-C2) characteristics [United States Salinity Laboratory (USSL) classification scheme]. All data points from this study plot within the 'Excellent to good' category on a Wilcox diagram. Groundwater in this area thus appears to provide irrigation water of excellent quality. The hydrochemical results indicate that, although nitrate and fluoride concentrations in some boreholes are high, the groundwater in the study area, based on the parameters analyzed, is chemically potable and suitable for domestic and agricultural purposes. ?? Springer-Verlag 2008.

Conceptual model and numerical simulation of the groundwater-flow system of Bainbridge Island, Washington

USGS Publications Warehouse

Frans, Lonna M.; Bachmann, Matthew P.; Sumioka, Steve S.; Olsen, Theresa D.

2011-01-01

Groundwater is the sole source of drinking water for the population of Bainbridge Island. Increased use of groundwater supplies on Bainbridge Island as the population has grown over time has created concern about the quantity of water available and whether saltwater intrusion will occur as groundwater usage increases. A groundwater-flow model was developed to aid in the understanding of the groundwater system and the effects of groundwater development alternatives on the water resources of Bainbridge Island. Bainbridge Island is underlain by unconsolidated deposits of glacial and nonglacial origin. The surficial geologic units and the deposits at depth were differentiated into aquifers and confining units on the basis of areal extent and general water-bearing characteristics. Eleven principal hydrogeologic units are recognized in the study area and form the basis of the groundwater-flow model. A transient variable-density groundwater-flow model of Bainbridge Island and the surrounding area was developed to simulate current (2008) groundwater conditions. The model was calibrated to water levels measured during 2007 and 2008 using parameter estimation (PEST) to minimize the weighted differences or residuals between simulated and measured hydraulic head. The calibrated model was used to make some general observations of the groundwater system in 2008. Total flow through the groundwater system was about 31,000 acre-ft/ yr. The recharge to the groundwater system was from precipitation and septic-system returns. Groundwater flow to Bainbridge Island accounted for about 1,000 acre-ft/ yr or slightly more than 5 percent of the recharge amounts. Groundwater discharge was predominately to streams, lakes, springs, and seepage faces (16,000 acre-ft/yr) and directly to marine waters (10,000 acre-ft/yr). Total groundwater withdrawals in 2008 were slightly more than 6 percent (2,000 acre-ft/yr) of the total flow. The calibrated model was used to simulate predevelopment conditions, during which no groundwater pumping or secondary recharge occurred and currently developed land was covered by conifer forests. Simulated water levels in the uppermost aquifer generally were slightly higher at the end of 2008 than under predevelopment conditions, likely due to increased recharge from septic returns and reduced evapotranspiration losses due to conversion of land cover from forests to current conditions. Simulated changes in water levels for the extensively used sea-level aquifer were variable, although areas with declines between zero and 10 feet were common and generally can be traced to withdrawals from public-supply drinking wells. Simulated water-level declines in the deep (Fletcher Bay) aquifer between predevelopment and 2008 conditions ranged from about 10 feet in the northeast to about 25 feet on the western edge of the Island. These declines are related to groundwater withdrawals for public-supply purposes. The calibrated model also was used to simulate the possible effects of increased groundwater pumping and changes to recharge due to changes in land use and climactic conditions between 2008 and 2035 under minimal, expected, and maximum impact conditions. Drawdowns generally were small for most of the Island (less than 10 ft) for the minimal and expected impact scenarios, and were larger for the maximum impact scenario. No saltwater intrusion was evident in any scenario by the year 2035. The direction of flow in the deep Fletcher Bay aquifer was simulated to reverse direction from its predevelopment west to east direction to an east to west direction under the maximum impact scenario.

Groundwater quality in the Southeastern Coastal Plain aquifer system, southeastern United States

USGS Publications Warehouse

Barlow, Jeannie; Lindsey, Bruce; Belitz, Kenneth

2017-01-19

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Southeastern Coastal Plain aquifer system constitutes one of the important areas being evaluated. One or more inorganic constituents with human-health benchmarks were detected at high concentrations in about 6 percent of the study area and at moderate concentrations in about 13 percent. One or more organic constituents with human-health benchmarks were detected at moderate concentrations in about 3 percent of the study area.

Groundwater quality in the Basin and Range Basin-Fill Aquifers, southwestern United States

USGS Publications Warehouse

Musgrove, MaryLynn; Belitz, Kenneth

2017-01-19

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Basin and Range basin-fill aquifers constitute one of the important areas being evaluated. One or more inorganic constituents with human-health benchmarks were detected at high concentrations in about 20 percent of the study area and at moderate concentrations in about 49 percent. Organic constituents were not detected at high concentrations in the study area. One or more organic constituents with human-health benchmarks were detected at moderate concentrations in about 3 percent of the study area.

Assessing aquifer vulnerability from lumped parameter modeling of modern water proportions in groundwater mixtures - Application to nitrate pollution in California's South Coast Range

NASA Astrophysics Data System (ADS)

Hagedorn, B.; Ruane, M.; Clark, N.

2017-12-01

In California, the overuse of synthetic fertilizers and manure in agriculture have caused nitrate (NO3) to be one of the state's most widespread groundwater pollutants. Given that nitrogen fertilizer applications have steadily increased since the 1950s and given that soil percolation and recharge transit times in California can exceed timescales of decades, the nitrate impact on groundwater resources is likely a legacy for years and even decades to come. This study presents a methodology for groundwater vulnerability assessment that operates independently of difficult-to-constrain soil and aquifer property data (i.e., saturated thickness, texture, porosity, conductivity, etc.), but rather utilizes groundwater age and, more importantly, groundwater mixing information to illustrate actual vulnerability at the water table. To accomplish this, the modern (i.e., less than 60-year old) water proportion (MWP) in groundwater mixtures is computed via lumped parameter modeling of chemical tracer (i.e., 3H, 14C and 3Hetrit) data. These MWPs are then linked to groundwater dissolved oxygen (DO) values to describe the risk for soil zone-derived nitrate to accumulate in the saturated zone. Preliminary studies carried out for 71 wells in California's South Coast Range-Coastal (SCRC) study unit reveal MWP values derived from binary dispersion models of 3.24% to 21.8%. The fact that high MWPs generally coincide with oxic (DO ≥1.5 mg/L) groundwater conditions underscores the risk towards increased groundwater NO3 pollution for many of the tested wells. These results support the conclusion that best agricultural management and policy objectives should incorporate groundwater vulnerability models that are developed at the same spatial scale as the decision making.

Evaluating the relationship between topography and groundwater using outputs from a continental-scale integrated hydrology model

NASA Astrophysics Data System (ADS)

Condon, Laura E.; Maxwell, Reed M.

2015-08-01

We study the influence of topography on groundwater fluxes and water table depths across the contiguous United States (CONUS). Groundwater tables are often conceptualized as subdued replicas of topography. While it is well known that groundwater configuration is also controlled by geology and climate, nonlinear interactions between these drivers within large real-world systems are not well understood and are difficult to characterize given sparse groundwater observations. We address this limitation using the fully integrated physical hydrology model ParFlow to directly simulate groundwater fluxes and water table depths within a complex heterogeneous domain that incorporates all three primary groundwater drivers. Analysis is based on a first of its kind, continental-scale, high-resolution (1 km), groundwater-surface water simulation spanning more than 6.3 million km2. Results show that groundwater fluxes are most strongly driven by topographic gradients (as opposed to gradients in pressure head) in humid regions with small topographic gradients or low conductivity. These regions are generally consistent with the topographically controlled groundwater regions identified in previous studies. However, we also show that areas where topographic slopes drive groundwater flux do not generally have strong correlations between water table depth and elevation. Nonlinear relationships between topography and water table depth are consistent with groundwater flow systems that are dominated by local convergence and could also be influenced by local variability in geology and climate. One of the strengths of the numerical modeling approach is its ability to evaluate continental-scale groundwater behavior at a high resolution not possible with other techniques. This article was corrected on 11 SEP 2015. See the end of the full text for details.

Groundwater Drought and Recovery: a Case Study from the United Kingdom

NASA Astrophysics Data System (ADS)

Peach, D.; McKenzie, A. A.; Bloomfield, J.

2012-12-01

An understanding of the processes leading to the onset, duration and end of hydrological droughts is necessary to help improve the management of stressed or scarce water resources during such periods. In particular, the role and use of groundwater during episodes of drought is crucially important, since groundwater can provide relatively resilient water supplies during early stages of drought but maybe highly susceptible to relatively persistent or sustained droughts. Nevertheless, groundwater is seldom considered in drought analyses, and compared with other types of hydrological drought there have been few studies to date. The few previous studies of groundwater droughts at catchment- and regional-scale have shown that catchment and aquifer characteristics exert a strong influence on the spatio-temporal development of groundwater droughts as water deficit propagates through the terrestrial water cycle. In this context, the relationships between hydrogeological heterogeneity, catchment engineering infrastructure (storage), and decisions related to water resource management during drought events all shape the evolution and consequences of groundwater droughts. Here we examine the evolution of a recent regionally significant two-year drought across the United Kingdom (UK) and use it to investigate these relationships. We identify the drivers, characterise the development and spatio-temporal extent of the groundwater drought. In particular, we focus on the unusually rapid end and recovery from drought during what would normally be a period of groundwater recession. The UK, and in particular southern England, relies extensively on groundwater for public water supply, agricultural and industrial use, as well as for sustaining river flows that are essential to ecosystem health. In normal years relatively consistent rainfall patterns prevail, recharging aquifers over winter when evapotranspiration is minimal. However, by March 2012 large parts of the southern UK had experienced accumulated rainfall deficiencies over 24 months or more. Such rainfall deficiencies could, on aver¬age, only be expected around once every 20 to 30 years. The rainfall deficiencies were disproportionately concentrated in the winter/spring periods leading to significant reductions in groundwater recharge over the winters of 2010-11 and particularly 2011-12. At it's height in March 2012 groundwater levels were at historically low levels with estimated overall storage in the Chalk aquifer, the principal aquifer in the UK, lower than at the same time in 1976, the previous benchmark drought for the UK. Natural base levels had been reached or closely approached at a number of index wells early in the hydrometric year and groundwater recession was expected to continue with the prospect of overall groundwater resources being comparable with, or below, the lowest in the last 100 years by the autumn of 2012. However, a significant change in weather in spring 2012 led to three months (April to June) of exceptional rainfall, mitigating the drought and leading to anomalous groundwater recharge at a time of year when soil moisture deficits are normally significant.

Agricultural Groundwater Demands in the Conterminous United States

NASA Astrophysics Data System (ADS)

Ho, M. W.; Parthasarathy, V.; Etienne, E.; Russo, T. A.; Devineni, N.; Lall, U.

2016-12-01

In the conterminous United States (CONUS), over 40% of water consumed for irrigation, livestock and domestic water is sourced from groundwater. The late 20th century and 21st century saw an expansion in irrigated agriculture across the CONUS that was accompanied by increased pumping of groundwater. Groundwater is typically used to mitigate impacts of drought on surface water supplies enabling water demands to be met as well as to augment sparse surface water resources in arid regions or where surface water availability is highly variable temporally and/or spatially. A Demand Sensitive Drought Index (DSDI) is used to examine the impacts of agricultural water needs on groundwater in the CONUS. The DSDI accounts for agricultural water deficits driven by low precipitation, high agricultural water demand, or a combination of both. Changes in groundwater levels relative to agricultural water deficits are characterized relative to precipitation during the growing season and winter precipitation. In several key irrigated agricultural regions in the CONUS, long-term trends in groundwater levels appear to reflect prolonged periods of surface water deficits resulting from land use and associated unsustainable water demands. These areas are subsequent unable to recover from persistent states of agricultural drought. Conversely, reductions in agricultural water demands for crops do not necessarily lead to immediate recovery of groundwater levels due to the demand for groundwater in other sectors. Calls to establish or reform groundwater policies have recently been made in an effort to achieve holistic groundwater management strategies that consider the human demands on both surface water and groundwater. There is a need for relevant groundwater policies to ensure that water demands are adequately managed across sectors without unsustainably depleting groundwater resources and to ensure efficient economic activity.

Potential corrosivity of untreated groundwater in the United States

USGS Publications Warehouse

Belitz, Kenneth; Jurgens, Bryant C.; Johnson, Tyler D.

2016-07-12

Corrosive groundwater, if untreated, can dissolve lead and other metals from pipes and other components in water distribution systems. Two indicators of potential corrosivity—the Langelier Saturation Index (LSI) and the Potential to Promote Galvanic Corrosion (PPGC)—were used to identify which areas in the United States might be more susceptible to elevated concentrations of metals in household drinking water and which areas might be less susceptible. On the basis of the LSI, about one-third of the samples collected from about 21,000 groundwater sites are classified as potentially corrosive. On the basis of the PPGC, about two-thirds of the samples collected from about 27,000 groundwater sites are classified as moderate PPGC, and about one-tenth as high PPGC. Potentially corrosive groundwater occurs in all 50 states and the District of Columbia.National maps have been prepared to identify the occurrence of potentially corrosive groundwater in the 50 states and the District of Columbia. Eleven states and the District of Columbia were classified as having a very high prevalence of potentially corrosive groundwater, 14 states as having a high prevalence of potentially corrosive groundwater, 19 states as having a moderate prevalence of potentially corrosive groundwater, and 6 states as having a low prevalence of potentially corrosive groundwater. These findings have the greatest implication for people dependent on untreated groundwater for drinking water, such as the 44 million people that are self-supplied and depend on domestic wells or springs for their water supply.

[Relationship between groundwater quality index of nutrition element and organic matter in riparian zone and water quality in river].

PubMed

Hua-Shan, Xu; Tong-Qian, Zhao; Hong-Q, Meng; Zong-Xue, Xu; Chao-Hon, Ma

2011-04-01

Riparian zone hydrology is dominated by shallow groundwater with complex interactions between groundwater and surface water. There are obvious relations of discharge and recharge between groundwater and surface water. Flood is an important hydrological incident that affects groundwater quality in riparian zone. By observing variations of physical and chemical groundwater indicators in riparian zone at the Kouma section of the Yellow River Wetland, especially those took place in the period of regulation for water and sediment at the Xiaolangdi Reservoir, relationship between the groundwater quality in riparian zone and the flood water quality in the river is studied. Results show that there will be great risk of nitrogen, phosphorus, nitrate nitrogen and organic matter permeating into the groundwater if floodplain changes into farmland. As the special control unit of nitrogen pollution between rivers and artificial wetlands, dry fanning areas near the river play a very important role in nitrogen migration between river and groundwater. Farm manure as base fertilizer may he an important source of phosphorus leak and loss at the artificial wetlands. Phosphorus leaks into the groundwater and is transferred along the hydraulic gradient, especially during the period of regulation for water and sediment at the Xiaolangdi Reservoir. The land use types and farming systems of the riparian floodplain have a major impact on the nitrate nitrogen contents of the groundwater. Nitrogen can infiltrate and accumulate quickly at anaerobic conditions in the fish pond area, and the annual nitrogen achieves a relatively balanced state in lotus area. In those areas, the soil is flooded and at anaerobic condition in spring and summer, nitrogen infiltrates and denitrification significantly, but soil is not flooded and at aerobic condition in the autumn and winter, and during these time, a significant nitrogen nitrification process occurs. In the area between 50 m and 200 m from the river bank, which is the efficient microbial nitrogen purification unit, nitrification-denitrification is intensive. Farm manure is an important source of organic matter loss at the artificial wetlands. Floodplain has sandy soil texture, with high infiltration capacity and low water and fertilizer conservation ability. Such features are prone for the loss of surface soil nutrition and organic matter if agricultural activities taken place in these areas change the land use of wetlands and apply extensive fertilizer. The infiltrated nutrition elements and organic matter can pollute the groundwater and the river. Compared with the losses of nutrition element and organic matter caused by surface runoff, the infiltrated process is even more prominent. As typical floodplain groundwater-river ecotone, the area between 50 m and 200 m from the river bank is a momentous pollution purification unit. Rational protection for this region is critical for the conservation of water quality in the river and groundwater.

40 CFR 264.90 - Applicability.

Code of Federal Regulations, 2013 CFR

2013-07-01

... applying to a regulated unit with alternative requirements for groundwater monitoring and corrective action for releases to groundwater set out in the permit (or in an enforceable document) (as defined in 40... contributed to the release; and (2) It is not necessary to apply the groundwater monitoring and corrective...

40 CFR 264.90 - Applicability.

Code of Federal Regulations, 2012 CFR

2012-07-01

... applying to a regulated unit with alternative requirements for groundwater monitoring and corrective action for releases to groundwater set out in the permit (or in an enforceable document) (as defined in 40... contributed to the release; and (2) It is not necessary to apply the groundwater monitoring and corrective...

40 CFR 264.90 - Applicability.

Code of Federal Regulations, 2014 CFR

2014-07-01

... applying to a regulated unit with alternative requirements for groundwater monitoring and corrective action for releases to groundwater set out in the permit (or in an enforceable document) (as defined in 40... contributed to the release; and (2) It is not necessary to apply the groundwater monitoring and corrective...

Evaluation of the Source and Transport of High Nitrate Concentrations in Ground Water, Warren Subbasin, California

USGS Publications Warehouse

Nishikawa, Tracy; Densmore, Jill N.; Martin, Peter; Matti, Jonathan

2003-01-01

Ground water historically has been the sole source of water supply for the Town of Yucca Valley in the Warren subbasin of the Morongo ground-water basin, California. An imbalance between ground-water recharge and pumpage caused ground-water levels in the subbasin to decline by as much as 300 feet from the late 1940s through 1994. In response, the local water district, Hi-Desert Water District, instituted an artificial recharge program in February 1995 using imported surface water to replenish the ground water. The artificial recharge program resulted in water-level recoveries of as much as 250 feet in the vicinity of the recharge ponds between February 1995 and December 2001; however, nitrate concentrations in some wells also increased from a background concentration of 10 milligrams per liter to more than the U.S. Environmental Protection Agency (USEPA) maximum contaminant level (MCL) of 44 milligrams per liter (10 milligrams per liter as nitrogen). The objectives of this study were to: (1) evaluate the sources of the high-nitrate concentrations that occurred after the start of the artificial-recharge program, (2) develop a ground-water flow and solute-transport model to better understand the source and transport of nitrates in the aquifer system, and (3) utilize the calibrated models to evaluate the possible effect of a proposed conjunctive-use project. These objectives were accomplished by collecting water-level and water-quality data for the subbasin and assessing changes that have occurred since artificial recharge began. Collected data were used to calibrate the ground-water flow and solute-transport models. Data collected for this study indicate that the areal extent of the water-bearing deposits is much smaller (about 5.5 square miles versus 19 square miles) than that of the subbasin. These water-bearing deposits are referred to in this report as the Warren ground-water basin. Faults separate the ground-water basin into five hydrogeologic units: the west, the midwest, the mideast, the east and the northeast hydrogeologic units. Water-quality analyses indicate that septage from septic tanks is the primary source of the high-nitrate concentrations measured in the Warren ground-water basin. Water-quality and stable-isotope data, collected after the start of the artificial recharge program, indicate that mixing occurs between imported water and native ground water, with the highest recorded nitrate concentrations in the midwest and the mideast hydrogeologic units. In general, the timing of the increase in measured nitrate concentrations in the midwest hydrogeologic unit is directly related to the distance of the monitoring well from a recharge site, indicating that the increase in nitrate concentrations is related to the artificial recharge program. Nitrate-to-chloride and nitrogen-isotope data indicate that septage is the source of the measured increase in nitrate concentrations in the midwest and the mideast hydrogeologic units. Samples from four wells in the Warren ground-water basin were analyzed for caffeine and selected human pharmaceutical products; these analyses suggest that septage is reaching the water table. There are two possible conceptual models that explain how high-nitrate septage reaches the water table: (1) the continued downward migration of septage through the unsaturated zone to the water table and (2) rising water levels, a result of the artificial recharge program, entraining septage in the unsaturated zone. The observations that nitrate concentrations increase in ground-water samples from wells soon after the start of the artificial recharge program in 1995 and that the largest increase in nitrate concentrations occur in the midwest and mideast hydrogeologic units where the largest increase in water levels occur indicate the validity of the second conceptual model (rising water levels). The potential nitrate concentration resulting from a water-level rise in the midwest and

Risk assessment of groundwater environmental contamination: a case study of a karst site for the construction of a fossil power plant.

PubMed

Liu, Fuming; Yi, Shuping; Ma, Haiyi; Huang, Junyi; Tang, Yukun; Qin, Jianbo; Zhou, Wan-Huan

2017-12-20

This paper presents a demonstration of an integrated risk assessment and site investigation for groundwater contamination through a case study, in which the geologic and hydrogeological feature of the site and the blueprint of the fossil power plant (FPP) were closely analyzed. Predictions for groundwater contamination in case of accidents were performed by groundwater modeling system (GMS) and modular three-dimensional multispecies transport model (MT3DMS). Results indicate that the studied site area presents a semi-isolated hydrogeological unit with multiplicity in stratum lithology, the main aquifers at the site are consisted of the filled karst development layer with a thickness between 6.0 and 40.0 m. The poor permeability of the vadose zone at the FPP significantly restricted the infiltration of contaminants through the vadose zone to the subsurface. The limited influence of rarely isotropic porous karstified carbonate rocks on the groundwater flow system premised the simulate scenarios of plume migration. Analysis of the present groundwater chemistry manifested that that the groundwater at the site and the local area are of the HCO 3 -Ca, HCO 3 , and SO 4 -Ca types. A few of the water samples were contaminated by coliform bacteria and ammonia nitrogen as a result of the local cultivation. Prediction results indicate that the impact of normal construction and operation processes on the groundwater environment is negligible. However, groundwater may be partly contaminated within a certain period in the area of leakage from the diesel tanks, the industrial wastewater pool, and the cooling tower water tank in case of accidents. On a positive note, none of the plumes would reach the local sensitive areas for groundwater using. Finally, an anti-seepage scheme and a monitoring program are proposed to safeguard the groundwater protection. The integrated method of the site investigation and risk assessment used in this case study can facilitate the protection of groundwater for the construction of large-scale industrial project.

Ground-Water Flow Model of the Sierra Vista Subwatershed and Sonoran Portions of the Upper San Pedro Basin, Southeastern Arizona, United States, and Northern Sonora, Mexico

USGS Publications Warehouse

Pool, D.R.; Dickinson, Jesse

2007-01-01

A numerical ground-water model was developed to simulate seasonal and long-term variations in ground-water flow in the Sierra Vista subwatershed, Arizona, United States, and Sonora, Mexico, portions of the Upper San Pedro Basin. This model includes the simulation of details of the groundwater flow system that were not simulated by previous models, such as ground-water flow in the sedimentary rocks that surround and underlie the alluvial basin deposits, withdrawals for dewatering purposes at the Tombstone mine, discharge to springs in the Huachuca Mountains, thick low-permeability intervals of silt and clay that separate the ground-water flow system into deep-confined and shallow-unconfined systems, ephemeral-channel recharge, and seasonal variations in ground-water discharge by wells and evapotranspiration. Steady-state and transient conditions during 1902-2003 were simulated by using a five-layer numerical ground- water flow model representing multiple hydrogeologic units. Hydraulic properties of model layers, streamflow, and evapotranspiration rates were estimated as part of the calibration process by using observed water levels, vertical hydraulic gradients, streamflow, and estimated evapotranspiration rates as constraints. Simulations approximate observed water-level trends throughout most of the model area and streamflow trends at the Charleston streamflow-gaging station on the San Pedro River. Differences in observed and simulated water levels, streamflow, and evapotranspiration could be reduced through simulation of climate-related variations in recharge rates and recharge from flood-flow infiltration.

Estimates of nitrate loads and yields from groundwater to streams in the Chesapeake Bay watershed based on land use and geology

USGS Publications Warehouse

Terziotti, Silvia; Capel, Paul D.; Tesoriero, Anthony J.; Hopple, Jessica A.; Kronholm, Scott C.

2018-03-07

The water quality of the Chesapeake Bay may be adversely affected by dissolved nitrate carried in groundwater discharge to streams. To estimate the concentrations, loads, and yields of nitrate from groundwater to streams for the Chesapeake Bay watershed, a regression model was developed based on measured nitrate concentrations from 156 small streams with watersheds less than 500 square miles (mi2 ) at baseflow. The regression model has three predictive variables: geologic unit, percent developed land, and percent agricultural land. Comparisons of estimated and actual values within geologic units were closely matched. The coefficient of determination (R2 ) for the model was 0.6906. The model was used to calculate baseflow nitrate concentrations at over 83,000 National Hydrography Dataset Plus Version 2 catchments and aggregated to 1,966 total 12-digit hydrologic units in the Chesapeake Bay watershed. The modeled output geospatial data layers provided estimated annual loads and yields of nitrate from groundwater into streams. The spatial distribution of annual nitrate yields from groundwater estimated by this method was compared to the total watershed yields of all sources estimated from a Chesapeake Bay SPAtially Referenced Regressions On Watershed attributes (SPARROW) water-quality model. The comparison showed similar spatial patterns. The regression model for groundwater contribution had similar but lower yields, suggesting that groundwater is an important source of nitrogen for streams in the Chesapeake Bay watershed.

Assessment of ground water vulnerability and its application to the development of protection strategy for the water supply aquifer in Owerri, Southeastern Nigeria.

PubMed

Ibe, K M; Nwankwor, G I; Onyekuru, S O

2001-03-01

Pollution vulnerability of the Owerri regional water supply aquifer was evaluated as a basis for developing appropriate protection strategy for the groundwater resource. The assessment was accomplished using Legrand, GOD, Siga and DRASTIC models. Techniques of the models generally involved parameters rating and point count systems, which are based on the evaluation of various parameter in relation to their capacity for enhancing or attenuating contaminants in the groundwater system. Field and laboratory evaluations of the parameters indicate that the Owerri area generally occupies a nearly, flat topography with a relatively high groundwater recharge. The area is underlain by predominantly sandy facies in the Northern area which grades into gravelly sequences towards the southwest. The Southeastern area is distinguished by thick clayey facies that thin westwards towards the Owerri metropolis. Effective hydraulic conductivity (Kz) in the downward direction ranges from 1.44 x 10(-3) to 5.6 x 10(-9) m s(-1); with the upper limits reflecting coarse sands and gravelly units. The amount of clay and clay-size particles in the sandy and gravelly units is negligible, suggesting that the sorptive capacity of the units is low. Depth to water table decreases southwards while hydraulic head gradients vary between 0.09 and 0.22. Groundwater occurs in unconfined conditions in most places except in the southeastern zone where it is semi-confined due to the presence of a clayey unit. The groundwater vulnerability map developed on the basis of the models and several other thematic maps shows that the Owerri metropolis and the southwest area of Owerri have high vulnerability, indicating groundwater pollution. The existing waste disposal sites in these sub-areas should be abandoned and rehabilitated to forstall further pollution of the groundwater system. Areas to the North and Southeast of Owerri have moderate and low vulnerabilities, respectively, indicating the relatively lower sensitivity of the groundwater system in the sub-areas to contamination. The lower sensitivity could further be matched with properly engineered sanitary landfills in the event of choice of sites, as an additional protective strategy for the groundwater system.

An innovative procedure to assess multi-scale temporal trends in groundwater quality: Example of the nitrate in the Seine-Normandy basin, France

NASA Astrophysics Data System (ADS)

Lopez, Benjamin; Baran, Nicole; Bourgine, Bernard

2015-03-01

The European Water Framework Directive (WFD) asks Member States to identify trends in contaminant concentrations in groundwater and to take measures to reach a good chemical status by 2015. In this study, carried out in a large hydrological basin (95,300 km2), an innovative procedure is described for the assessment of recent trends in groundwater nitrate concentrations both at sampling point and regional scales. Temporal variograms of piezometric and nitrate concentration time series are automatically calculated and fitted in order to classify groundwater according to their temporal pattern. These results are then coupled with aquifer lithology to map spatial units within which the modes of diffuse transport of contaminants towards groundwater are assumed to be the same at all points. These spatial units are suitable for evaluating regional trends. The stability over time of the time series is tested based on the cumulative sum principle, to determine the time period during which the trend should be sought. The Mann-Kendall and Regional-Kendall nonparametric tests for monotonic trends, coupled with the Sen-slope test, are applied to the periods following the point breaks thus determined at both the sampling point or regional scales. This novel procedure is robust and enables rapid processing of large databases of raw data. It would therefore be useful for managing groundwater quality in compliance with the aims of the WFD.

Analyses of infrequent (quasi-decadal) large groundwater recharge events in the northern Great Basin: Their importance for groundwater availability, use, and management

USGS Publications Warehouse

Masbruch, Melissa D.; Rumsey, Christine; Gangopadhyay, Subhrendu; Susong, David D.; Pruitt, Tom

2016-01-01

There has been a considerable amount of research linking climatic variability to hydrologic responses in the western United States. Although much effort has been spent to assess and predict changes in surface water resources, little has been done to understand how climatic events and changes affect groundwater resources. This study focuses on characterizing and quantifying the effects of large, multiyear, quasi-decadal groundwater recharge events in the northern Utah portion of the Great Basin for the period 1960–2013. Annual groundwater level data were analyzed with climatic data to characterize climatic conditions and frequency of these large recharge events. Using observed water-level changes and multivariate analysis, five large groundwater recharge events were identified with a frequency of about 11–13 years. These events were generally characterized as having above-average annual precipitation and snow water equivalent and below-average seasonal temperatures, especially during the spring (April through June). Existing groundwater flow models for several basins within the study area were used to quantify changes in groundwater storage from these events. Simulated groundwater storage increases per basin from a single recharge event ranged from about 115 to 205 Mm3. Extrapolating these amounts over the entire northern Great Basin indicates that a single large quasi-decadal recharge event could result in billions of cubic meters of groundwater storage. Understanding the role of these large quasi-decadal recharge events in replenishing aquifers and sustaining water supplies is crucial for long-term groundwater management.

The CHPRC Groundwater and Technical Integration Support (Master Project) Quality Assurance Management Plan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fix, N. J.

The scope of the CH2M Hill Plateau Remediation Company, LLC (CHPRC) Groundwater and Technical Integration Support (Master Project) is for Pacific Northwest National Laboratory staff to provide technical and integration support to CHPRC. This work includes conducting investigations at the 300-FF-5 Operable Unit and other groundwater operable units, and providing strategic integration, technical integration and assessments, remediation decision support, and science and technology. The projects under this Master Project will be defined and included within the Master Project throughout the fiscal year, and will be incorporated into the Master Project Plan. This Quality Assurance Management Plan provides the quality assurancemore » requirements and processes that will be followed by the CHPRC Groundwater and Technical Integration Support (Master Project) and all releases associated with the CHPRC Soil and Groundwater Remediation Project. The plan is designed to be used exclusively by project staff.« less

Groundwater Quality Data in the Mojave Study Unit, 2008: Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Belitz, Kenneth

2009-01-01

Groundwater quality in the approximately 1,500 square-mile Mojave (MOJO) study unit was investigated from February to April 2008, as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). MOJO was the 23rd of 37 study units to be sampled as part of the GAMA Priority Basin Project. The MOJO study was designed to provide a spatially unbiased assessment of the quality of untreated ground water used for public water supplies within MOJO, and to facilitate statistically consistent comparisons of groundwater quality throughout California. Samples were collected from 59 wells in San Bernardino and Los Angeles Counties. Fifty-two of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study area (grid wells), and seven were selected to aid in evaluation of specific water-quality issues (understanding wells). The groundwater samples were analyzed for a large number of organic constituents [volatile organic compounds (VOCs), pesticides and pesticide degradates, and pharmaceutical compounds], constituents of special interest (perchlorate and N-nitrosodimethylamine [NDMA]) naturally occurring inorganic constituents (nutrients, dissolved organic carbon [DOC], major and minor ions, silica, total dissolved solids [TDS], and trace elements), and radioactive constituents (gross alpha and gross beta radioactivity, radium isotopes, and radon-222). Naturally occurring isotopes (stable isotopes of hydrogen, oxygen, and carbon, stable isotopes of nitrogen and oxygen in nitrate, and activities of tritium and carbon-14), and dissolved noble gases also were measured to help identify the sources and ages of the sampled ground water. In total, over 230 constituents and water-quality indicators (field parameters) were investigated. Three types of quality-control samples (blanks, replicates, and matrix spikes) each were collected at approximately 5-8 percent of the wells, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a significant source of bias in the data for the groundwater samples. Differences between replicate samples generally were within acceptable ranges, indicating acceptable analytical reproducibility. Matrix spike recoveries were within acceptable ranges for most compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, untreated groundwater typically is treated, disinfected, or blended with other waters to maintain water quality. Regulatory thresholds apply to water that is served to the consumer, not to untreated ground water. However, to provide some context for the results, concentrations of constituents measured in the untreated ground water were compared with regulatory and non-regulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH) and thresholds established for aesthetic and technical concerns by CDPH. Comparisons between data collected for this study and thresholds for drinking-water are for illustrative purposes only, and are not indicative of compliance or non-compliance with those thresholds. Most constituents that were detected in groundwater samples in the 59 wells in MOJO were found at concentrations below drinking-water thresholds. In MOJO's 52 grid wells, volatile organic compounds (VOCs) were detected in 40 percent of the wells, and pesticides and pesticide degradates were detected in 23 percent of the grid wel

Superfund record of decision (EPA Region 9): Mather Air Force Base, Soil and Groundwater operable units, Sacramento, CA, June 21, 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

The decision document presents the selected remedial actions for the Soil Operable Unit (OU) Sites and Groundwater OU Plumes, at the formerly active Mather Air Force Base (AFB), Sacramento County, California. The purpose of the Record of Decision (ROD) is to decide the appropriate level of remediation necessary to protect human health and the environment, and determine what requirements are applicable or relevant and appropriate requirements (ARARs) based on the groundwater beneficial use designation and site-specific conditions. The ROD has been divided into seven sections which specifically address the range of selected remedial actions for the Soil OU sites andmore » Groundwater OU plumes.« less

Hydrogeologic framework and groundwater/surface-water interactions of the Chehalis River basin, Washington

USGS Publications Warehouse

Gendaszek, Andrew S.

2011-01-01

The Chehalis River has the largest drainage basin of any river entirely contained within the State of Washington with a watershed of approximately 2,700 mi2 and has correspondingly diverse geology and land use. Demands for water resources have prompted the local citizens and governments of the Chehalis River basin to coordinate with Federal, State and Tribal agencies through the Chehalis Basin Partnership to develop a long-term watershed management plan. The recognition of the interdependence of groundwater and surface-water resources of the Chehalis River basin became the impetus for this study, the purpose of which is to describe the hydrogeologic framework and groundwater/surface-water interactions of the Chehalis River basin. Surficial geologic maps and 372 drillers' lithostratigraphic logs were used to generalize the basin-wide hydrogeologic framework. Five hydrogeologic units that include aquifers within unconsolidated glacial and alluvial sediments separated by discontinuous confining units were identified. These five units are bounded by a low permeability unit comprised of Tertiary bedrock. A water table map, and generalized groundwater-flow directions in the surficial aquifers, were delineated from water levels measured in wells between July and September 2009. Groundwater generally follows landsurface-topography from the uplands to the alluvial valley of the Chehalis River. Groundwater gradients are highest in tributary valleys such as the Newaukum River valley (approximately 23 cubic feet per mile), relatively flat in the central Chehalis River valley (approximately 6 cubic feet per mile), and become tidally influenced near the outlet of the Chehalis River to Grays Harbor. The dynamic interaction between groundwater and surface-water was observed through the synoptic streamflow measurements, termed a seepage run, made during August 2010, and monitoring of water levels in wells during the 2010 Water Year. The seepage run revealed an overall gain of 56.8 ± 23.7 cubic feet per second over 32.8 river miles (1.7 cubic feet per second per mile), and alternating gains and losses of streamflow ranging from -48.3 to 30.9 cubic feet per second per mile, which became more pronounced on the Chehalis River downstream of Grand Mound. However, most gains and losses were within measurement error. Groundwater levels measured in wells in unconsolidated sediments fluctuated with changes in stream stage, often within several hours. These fluctuations were set by precipitation events in the upper Chehalis River basin and tides of the Pacific Ocean in the lower Chehalis River basin.±

Groundwater economics: An object-oriented foundation for integrated studies of irrigated agricultural systems

NASA Astrophysics Data System (ADS)

Steward, David R.; Peterson, Jeffrey M.; Yang, Xiaoying; Bulatewicz, Tom; Herrera-Rodriguez, Mauricio; Mao, Dazhi; Hendricks, Nathan

2009-05-01

An integrated foundation is presented to study the impacts of external forcings on irrigated agricultural systems. Individually, models are presented that simulate groundwater hydrogeology and econometric farm level crop choices and irrigated water use. The natural association between groundwater wells and agricultural parcels is employed to couple these models using geographic information science technology and open modeling interface protocols. This approach is used to study the collective action problem of the common pool. Three different policies (existing, regulation, and incentive based) are studied in the semiarid grasslands overlying the Ogallala Aquifer in the central United States. Results show that while regulation using the prior appropriation doctrine and incentives using a water buy-back program may each achieve the same level of water savings across the study region, each policy has a different impact on spatial patterns of groundwater declines and farm level economic activity. This represents the first time that groundwater and econometric models of irrigated agriculture have been integrated at the well-parcel level and provides methods for scientific investigation of this coupled natural-human system. Results are useful for science to inform decision making and public policy debate.

Groundwater-Quality Data in the Madera-Chowchilla Study Unit, 2008: Results from the California GAMA Program

USGS Publications Warehouse

Shelton, Jennifer L.; Fram, Miranda S.; Belitz, Kenneth

2009-01-01

Groundwater quality in the approximately 860-square-mile Madera-Chowchilla study unit (MADCHOW) was investigated in April and May 2008 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The study was designed to provide a spatially unbiased assessment of the quality of raw groundwater used for public water supplies within MADCHOW, and to facilitate statistically consistent comparisons of groundwater quality throughout California. Samples were collected from 35 wells in Madera, Merced, and Fresno Counties. Thirty of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study area (grid wells), and five more were selected to provide additional sampling density to aid in understanding processes affecting groundwater quality (flow-path wells). Detection summaries in the text and tables are given for grid wells only, to avoid over-representation of the water quality in areas adjacent to flow-path wells. Groundwater samples were analyzed for a large number of synthetic organic constituents (volatile organic compounds [VOCs], low-level 1,2-dibromo-3-chloropropane [DBCP] and 1,2-dibromoethane [EDB], pesticides and pesticide degradates, polar pesticides and metabolites, and pharmaceutical compounds), constituents of special interest (N-nitrosodimethylamine [NDMA], perchlorate, and low-level 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), and radioactive constituents (uranium isotopes, and gross alpha and gross beta particle activities). Naturally occurring isotopes and geochemical tracers (stable isotopes of hydrogen, oxygen, and carbon, and activities of tritium and carbon-14), and dissolved noble gases also were measured to help identify the sources and ages of the sampled groundwater. In total, approximately 300 constituents and field water-quality indicators were investigated. Three types of quality-control samples (blanks, replicates, and samples for matrix spikes) each were collected at approximately 11 percent of the wells sampled for each analysis, and the results obtained from these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that data for the groundwater samples were not compromised by possible contamination during sample collection, handling or analysis. Differences between replicate samples were within acceptable ranges. Matrix spike recoveries were within acceptable ranges for most compounds. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, raw groundwater typically is treated, disinfected, or blended with other waters to maintain water quality. Regulatory thresholds apply to water that is served to the consumer, not to raw groundwater. However, to provide some context for the results, concentrations of constituents measured in the raw groundwater were compared with regulatory and non-regulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH), and with aesthetic and technical thresholds established by CDPH. Comparisons between data collected for this study and drinking-water thresholds are for illustrative purposes only, and are not indicative of compliance or non-compliance with regulatory thresholds. The concentrations of most constituents detected in groundwater samples from MADCHOW wells were below drinking-water thresholds. Organic compounds (VOCs and pesticides

Continuous resistivity profiling and seismic-reflection data collected in April 2010 from Indian River Bay, Delaware

USGS Publications Warehouse

Cross, V.A.; Bratton, J.F.; Michael, H.A.; Kroeger, K.D.; Green, Adrian; Bergeron, Emile M.

2014-01-01

A geophysical survey to delineate the fresh-saline groundwater interface and associated sub-bottom sedimentary structures beneath Indian River Bay, Delaware, was carried out in April 2010. This included surveying at higher spatial resolution in the vicinity of a study site at Holts Landing, where intensive onshore and offshore studies were subsequently completed. The total length of continuous resistivity profiling (CRP) survey lines was 145 kilometers (km), with 36 km of chirp seismic lines surveyed around the perimeter of the bay. Medium-resolution CRP surveying was performed using a 50-meter streamer in a baywide grid. Results of the surveying and data inversion showed the presence of many buried paleochannels beneath Indian River Bay that generally extended perpendicular from the shoreline in areas of modern tributaries, tidal creeks, and marshes. An especially wide and deep paleochannel system was imaged in the southeastern part of the bay near White Creek. Many paleochannels also had high-resistivity anomalies corresponding to low-salinity groundwater plumes associated with them, likely due to the presence of fine-grained estuarine mud and peats in the channel fills that act as submarine confining units. Where present, these units allow plumes of low-salinity groundwater that was recharged onshore to move beyond the shoreline, creating a complex fresh-saline groundwater interface in the subsurface. The properties of this interface are important considerations in construction of accurate coastal groundwater flow models. These models are required to help predict how nutrient-rich groundwater, recharged in agricultural watersheds such as this one, makes its way into coastal bays and impacts surface-water quality and estuarine ecosystems.

Groundwater-level trends and implications for sustainable water use in the Kabul Basin, Afghanistan

USGS Publications Warehouse

Mack, Thomas J.; Chornack, Michael P.; Taher, Mohammad R.

2013-01-01

The Kabul Basin, which includes the city of Kabul, Afghanistan, with a population of approximately 4 million, has several Afghan, United States, and international military installations that depend on groundwater resources for a potable water supply. This study examined groundwater levels in the Kabul Basin from 2004 to 2012. Groundwater levels have increased slightly in rural areas of the Kabul Basin as a result of normal precipitation after the drought of the early 2000s. However, groundwater levels have decreased in the city of Kabul due to increasing water use in an area with limited recharge. The rate of groundwater-level decrease in the city is greater for the 2008–2012 period (1.5 meters per year (m/yr) on average) than for the 2004–2008 period (0–0.7 m/yr on average). The analysis, which is corroborated by groundwater-flow modeling and a non-governmental organization decision-support model, identified groundwater-level decreases and associated implications for groundwater sustainability in the city of Kabul. Military installations in the city of Kabul (the Central Kabul subbasin) are likely to face water management challenges resulting from long-term groundwater sustainability concerns, such as the potential drying of shallow water-supply wells. Installations in the northern part of the Kabul Basin may have fewer issues with long-term water sustainability. Groundwater-level monitoring and groundwater-flow simulation can be valuable tools for assessing groundwater management options to improve the sustainability of water resources in the Kabul Basin.

Perchlorate Data for Streams and Groundwater in Selected Areas of the United States, 2004

USGS Publications Warehouse

Kalkhoff, Stephen J.; Stetson, Sarah J.; Lund, Kris D.; Wanty, Richard B.; Linder, Gregory L.

2010-01-01

This report presents data collected as part of a reconnaissance study to evaluate the occurrence of perchlorate in rivers and streams and in shallow aquifers in selected areas of the United States. Perchlorate, a component in rocket fuels, fireworks, and some explosives is soluble in water and persists in soils and water for long periods. It is biologically active at relatively low-levels in the environment, and has been identified as an endocrine-disrupting chemical. The purpose of this reconnaissance was to determine the occurrence of perchlorate in agricultural areas of the Midwestern and North-Central United States and in arid Central and Western parts of the United States. Samples were collected from 171 sites on rivers and streams and 146 sites from wells during the summer and early fall of 2004. Samples were collected from surface-water sites in 19 states and from wells in 5 states. Perchlorate was detected in samples collected in 15 states and was detected in 34 of 182 samples from rivers and streams and in 64 of 148 groundwater samples at concentrations equal to or greater than 0.4 micrograms per liter. Perchlorate concentrations were 1.0 micrograms per liter or greater in surface-water samples from seven states and in groundwater samples in four states. Only one surface-water and one groundwater sample had concentrations greater than 5.0 micrograms per liter. Perchlorate concentrations in followup samples collected from 1 to 3 months after the initial sample were unchanged at four of five stream sites.

Ground-Water Quality Data in the Coachella Valley Study Unit, 2007: Results from the California GAMA Program

USGS Publications Warehouse

Goldrath, Dara A.; Wright, Michael T.; Belitz, Kenneth

2009-01-01

Ground-water quality in the approximately 820 square-mile Coachella Valley Study Unit (COA) was investigated during February and March 2007 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001, and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The study was designed to provide a spatially unbiased assessment of raw ground water used for public-water supplies within the Coachella Valley, and to facilitate statistically consistent comparisons of ground-water quality throughout California. Samples were collected from 35 wells in Riverside County. Nineteen of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study unit (grid wells). Sixteen additional wells were sampled to evaluate changes in water chemistry along selected ground-water flow paths, examine land use effects on ground-water quality, and to collect water-quality data in areas where little exists. These wells were referred to as 'understanding wells'. The ground-water samples were analyzed for a large number of organic constituents (volatile organic compounds [VOC], pesticides and pesticide degradates, pharmaceutical compounds, and potential wastewater-indicator compounds), constituents of special interest (perchlorate and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (uranium, tritium, carbon-14, and stable isotopes of hydrogen, oxygen, and boron), and dissolved noble gases (the last in collaboration with Lawrence Livermore National Laboratory) also were measured to help identify the source and age of the sampled ground water. A quality-control sample (blank, replicate, or matrix spike) was collected at approximately one quarter of the wells, and the results for these samples were used to evaluate the quality of the data for the ground-water samples. Assessment of the quality-control information resulted in V-coding less than 0.1 percent of the data collected. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, and (or) blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is supplied to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH) and thresholds established for aesthetic purposes (secondary maximum contaminant levels, SMCL-CA) by CDPH. Most constituents detected in ground-water samples were at concentrations below drinking-water thresholds. Volatile organic compounds, pesticides, and pesticide degradates were detected in less than one-third of the grid well samples collected. All VOC and pesticide concentrations measured were below health-based thresholds. Potential waste-water indicators were detected in less than half of the wells sampled, and no detections were above health-based thresholds. Perchlorate was detected in seven grid wells; concentrations from two wells were above the CDPH maximum contaminant level (MCL-CA). Most detections of trace elements in samples collected from COA Study Unit wells were below water-quality thresholds. Exceptions include five samples of arsenic that were above the USEPA maximum contaminant level (MCL-US), two detections of boron above the CDPH notification level (NL-CA), and two detections of mol

Quantifying Ground-Water and Surface-Water Discharge from Evapotranspiration Processes in 12 Hydrographic Areas of the Colorado Regional Ground-Water Flow System, Nevada, Utah, and Arizona

USGS Publications Warehouse

DeMeo, Guy A.; Smith, J. LaRue; Damar, Nancy A.; Darnell, Jon

2008-01-01

Rapid population growth in southern Nevada has increased the demand for additional water supplies from rural areas of northern Clark and southern Lincoln counties to meet projected water-supply needs. Springs and rivers in these undeveloped areas sustain fragile riparian habitat and may be susceptible to ground-water withdrawals. Most natural ground-water and surface-water discharge from these basins occurs by evapotranspiration (ET) along narrow riparian corridors that encompassed about 45,000 acres or about 1 percent of the study area. This report presents estimates of ground- and surface-water discharge from ET across 3.5 million acres in 12 hydrographic areas of the Colorado Regional Ground-Water Flow System. Ground-and surface-water discharge from ET were determined by identifying areas of ground- and surface-water ET, delineating areas of similar vegetation and soil conditions (ET units), and computing ET rates for each of these ET units. Eight ET units were identified using spectral-reflectance characteristics determined from 2003 satellite imagery, high-resolution aerial photography, and land classification cover. These ET units are dense meadowland vegetation (200 acres), dense woodland vegetation (7,200 acres), moderate woodland vegetation (6,100 acres), dense shrubland vegetation (5,800 acres), moderate shrubland vegetation (22,600 acres), agricultural fields (3,100 acres), non-phreatophytic areas (3,400,000 acres), and open water (300 acres). ET from diffuse ground-water and channelized surface-water is expressed as ETgs and is equal to the difference between total annual ET and precipitation. Total annual ET rates were calculated by the Bowen ratio and eddy covariance methods using micrometeorological data collected from four sites and estimated at 3.9 ft at a dense woodland site (February 2003 to March 2005), 3.6 ft at a moderate woodland site (July 2003 to October 2006), 2.8 ft at a dense shrubland site (June 2005 to October 2006), and 1.5 ft at a moderate shrubland site (April 2006 to October 2006). Annual ETgs rates were 3.4 ft for dense woodland vegetation, 3.2 ft for moderate woodland vegetation, 2.2 ft for dense shrubland vegetation, and 1.0 ft for moderate shrubland vegetation. Published annual rates of ETgs were used for the other ET units found in the study area. These rates were 3.4 ft for dense meadowland vegetation, 5.2 ft for agricultural fields, and 4.9 ft for open water. For the non-phreatophytic ET unit, ETgs was assumed to be zero. Estimated ground- and surface-water discharge from ET was calculated by multiplying the ETgs by the ET-unit acreage and equaled 24,480 acre-ft for dense woodland vegetation, 19,520 acre-ft for moderate woodland vegetation, 12,760 acre-ft for dense shrubland vegetation, 22,600 acre-ft for moderate shrubland vegetation, 680 acre-ft for dense meadowland vegetation, 16,120 acre-ft for agricultural fields, 1,440 acre-ft for open water, and 0 acre-ft for the non-phreatophytic ET unit. Estimated ground-water and surface-water discharge from ET from each hydrographic area was calculated by summing the total annual ETgs rate for ET units found within each hydrographic area and equaled 1,952 acre-ft for the Black Mountains Area, 6,080 acre-ft for California Wash, 4,090 acre-ft for the Muddy River Springs Area, 11,510 acre-ft for Lower Moapa Valley, 51,960 acre-ft for the Virgin River Valley, 16,168 acre-ft for Lower Meadow Valley Wash, 5,840 acre-ft for Clover Valley, and 0 acre-ft for Coyote Spring Valley, Kane Springs Valley, Tule Desert, Hidden Valley (North), and Garnet Valley. The annual discharge from ETgs for the study area totals about 98,000 acre-ft.

Impacts of Urbanization on Groundwater Quality and Recharge in a Semi-arid Alluvial Basin

USDA-ARS?s Scientific Manuscript database

The management of groundwater resources is paramount in semi-arid regions experiencing urban development. In the southwestern United States, enhancing recharge of urban storm runoff has been identified as a strategy for augmenting groundwater resources. An understanding of how urbanization may impac...

The Maryland Coastal Plain Aquifer Information System: A GIS-based tool for assessing groundwater resources

USGS Publications Warehouse

Andreasen, David C.; Nardi, Mark R.; Staley, Andrew W.; Achmad, Grufron; Grace, John W.

2016-01-01

Groundwater is the source of drinking water for ∼1.4 million people in the Coastal Plain Province of Maryland (USA). In addition, groundwater is essential for commercial, industrial, and agricultural uses. Approximately 0.757 × 109 L d–1 (200 million gallons/d) were withdrawn in 2010. As a result of decades of withdrawals from the coastal plain confined aquifers, groundwater levels have declined by as much as 70 m (230 ft) from estimated prepumping levels. Other issues posing challenges to long-term groundwater sustainability include degraded water quality from both man-made and natural sources, reduced stream base flow, land subsidence, and changing recharge patterns (drought) caused by climate change. In Maryland, groundwater supply is managed primarily by the Maryland Department of the Environment, which seeks to balance reasonable use of the resource with long-term sustainability. The chief goal of groundwater management in Maryland is to ensure safe and adequate supplies for all current and future users through the implementation of appropriate usage, planning, and conservation policies. To assist in that effort, the geographic information system (GIS)–based Maryland Coastal Plain Aquifer Information System was developed as a tool to help water managers access and visualize groundwater data for use in the evaluation of groundwater allocation and use permits. The system, contained within an ESRI ArcMap desktop environment, includes both interpreted and basic data for 16 aquifers and 14 confining units. Data map layers include aquifer and ­confining unit layer surfaces, aquifer extents, borehole information, hydraulic properties, time-series groundwater-level data, well records, and geophysical and lithologic logs. The aquifer and confining unit layer surfaces were generated specifically for the GIS system. The system also contains select groundwater-quality data and map layers that quantify groundwater and surface-water withdrawals. The aquifer information system can serve as a pre- and postprocessing environment for groundwater-flow models for use in water-supply planning, development, and management. The system also can be expanded to include features that evaluate constraints to groundwater development, such as insufficient available drawdown, degraded groundwater quality, insufficient aquifer yields, and well-field interference. Ultimately, the aquifer information system is intended to function as an interactive Web-based utility that provides a broad array of information related to groundwater resources in Maryland’s coastal plain to a wide-ranging audience, including well drillers, consultants, academia, and the general public.

A multidisciplinary analysis of groundwater declines and agricultural production in the High Plains Aquifer of Kansas

NASA Astrophysics Data System (ADS)

Steward, David R.; Bruss, Paul J.; Yang, Xiaoying; Staggenborg, Scott A.; Welch, Stephen M.; Apley, Michael D.

2014-05-01

The High Plains Aquifer provides groundwater for 30% of the irrigated agriculture in the USA. Within Kansas, groundwater supports the congressional district with highest market value of agriculture. And yet, over-pumping and associated groundwater declines threaten the long-term prospects. The groundwater portion of this study quantifies the availability of groundwater stores over the next 100 years. A water-use function is developed to quantify the historical and future impacts of irrigation on corn production. A relationship between corn consumption per head of cattle quantifies the herd size that can be supported by irrigated corn. Together, we project the impacts of changes in groundwater stores on corn and cattle production for the next century. Scenarios analyze the impacts of water savings today on current and future agriculture production. Reference: Steward, D. R., Bruss, P. J., Yang, X., Staggenborg, S. A., Welch, S. M. and M. D. Apley, Tapping unsustainable groundwater stores for agricultural production in the High Plains Aquifer of Kansas, projections to 2110, Proceedings of the National Academy of Sciences of the United States of America, 110(37) E3477-E3486, September 10, 2013. http://dx.doi.org/10.1073/pnas.1220351110

Hydrogeology and hydrogeologic terranes of the Blue Ridge and Piedmont Physiographic Provinces in the eastern United States

USGS Publications Warehouse

Mesko, Thomas O.; Swain, Lindsay A.; Hollyday, E.F.

2000-01-01

Severe and prolonged droughts between 1961 and 1988, combined with increased demands for freshwater supplies in the United States, have resulted in a critical need to assess the potential for development of ground- and surface-water supplies. Rapid industrial growth and urban expansion have caused existing freshwater supplies to be used at or near maximum capacity. Begun in 1978, the Regional Aquifer-System Analysis (RASA) Program of the U.S. Geological Survey (USGS) is a systematic effort to study a number of the Nation's most important aquifer systems, which, in aggregate, underlie much of the country and represent an important component of the Nation's total water supply. The broad objective for each of the 28 studies in the program is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system.In 1988, as part of the RASA Program, the USGS began a 6-year study of the ground-water resources of parts of 11 States in the Eastern United States (Swain and others, 1991). The study was designated the Appalachian Valley and Piedmont Regional Aquifer-System Analysis (APRASA). The APRASA team investigated ground-water resources primarily in the unglaciated part of the Valley and Ridge, the Blue Ridge, the New England, and the Piedmont Physiographic Provinces (fig. 1). For the purposes of this report, the small area in the New England Physiographic Province that is within the study area in New Jersey and Pennsylvania was considered part of the Piedmont Physiographic Province. The results of the APRASA are contained in about 50 reports and abstracts, including reports on simulation of ground-water flow in three type areas, this atlas, and chapters in Professional Paper 1422. These chapters include the summary (Chapter A), descriptions of recharge rates and surface- and ground-water relations (Chapter B), hydrogeologic terranes in the Valley and Ridge Physiographic Province (Chapter C), and ground-water geochemistry (Chapter D).The purposes of this atlas are to summarize the hydrogeology, to describe an analysis of maps and well records, and to present a classification and map of the hydrogeologic terranes of the Blue Ridge and Piedmont Physiographic Provinces within the APRASA study area. Hydrogeologic terranes are defined for this atlas as regionally mappable areas characterized by similar water-yielding properties of a grouping of selected rock types. The hydrogeologic terranes represent areas of distinct hydrologic character. The terranes are intended to help water users locate and develop adequate water supplies and to help hydrologists interpret the regional hydrogeology.Previous investigations provide maps and descriptions of the geologic units, describe the local quantity and quality of ground water within these units, and establish the statistical methods for comparing the water-yielding properties of these units. State geologic maps show the distribution of geologic units at a scale of 1:500,000 for Alabama (Osborne and others, 1989), Georgia (Lawton and others, 1976), North Carolina (Brown and Parker, 1985), and Virginia (Calver and Hobbs, 1963). State maps show geologic units at a scale of 1:250,000 for Maryland (Cleaves and others, 1968), New Jersey (Lewis and Kummel, 1912), Pennsylvania (Berg and others, 1980), South Carolina (Overstreet and Bell, 1965), Tennessee (Hardeman, 1966), and West Virginia (Cardwell and others, 1968). Quadrangle geologic maps show geologic units at a scale of 1:24,000 for parts of Delaware within the APRASA area (Woodruff and Thompson, 1972, 1975). Many reports have been published describing the groundwater resources of a county, parts of a county, multi-county areas, or river basins.The statistical methods used in this atlas are based largely on those used by Helsel and Hirsch (1992) and by Knopman (1990, p. 7-9). In her analysis of well records in the USGS Ground-Water Site Inventory (GWSI) data base, Knopman (1990) ranked factors that must be taken into account when assessing the water-yielding potential of the rocks in the Valley and Ridge, the Blue Ridge, and the Piedmont Physiographic Provinces in Pennsylvania. Readers are referred to Helsel and Hirsch (1992) and Knopman (1990) for details regarding statistical methods.

Groundwater quality in the Mojave area, California

USGS Publications Warehouse

Dawson, Barbara J. Milby; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Four groundwater basins along the Mojave River make up one of the study areas being evaluated. The Mojave study area is approximately 1,500 square miles (3,885 square kilometers) and includes four contiguous groundwater basins: Upper, Middle, and Lower Mojave River Groundwater Basins, and the El Mirage Valley (California Department of Water Resources, 2003). The Mojave study area has an arid climate, and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). Land use in the study area is approximately 82 percent (%) natural (mostly shrubland), 4% agricultural, and 14% urban. The primary crops are pasture and hay. The largest urban areas are the cities of Victorville, Hesperia, and Apple Valley (2010 populations of 116,000, 90,000 and 69,000, respectively). Groundwater in these basins is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from surrounding mountains. The primary aquifers in the Mojave study area are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in the Mojave study area are completed to depths between 200 and 600 feet (18 to 61 meters), consist of solid casing from the land surface to a depth of 130 to 420 feet (40 to 128 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the mountains to the south, mostly through the Mojave River channel. The primary sources of discharge are pumping wells and evapotranspiration.

Evaluating Micrometeorological Estimates of Groundwater Discharge from Great Basin Desert Playas

NASA Astrophysics Data System (ADS)

Jackson, T.; Halford, K. J.; Gardner, P.

2017-12-01

Groundwater availability studies in the arid southwestern United States traditionally have assumed that groundwater discharge by evapotranspiration (ETg) from desert playas is a significant component of the groundwater budget. This result occurs because desert playa ETg rates are poorly constrained by Bowen Ratio energy budget (BREB) and eddy-covariance (EC) micrometeorological measurement approaches. Best attempts by previous studies to constrain ETg from desert playas have resulted in ETg rates that are below the detection limit of micrometeorological approaches. This study uses numerical models to further constrain desert playa ETg rates that are below the detection limit of EC (0.1 mm/d) and BREB (0.3 mm/d) approaches, and to evaluate the effect of hydraulic properties and salinity-based groundwater-density contrasts on desert playa ETg rates. Numerical models simulated ETg rates from desert playas in Death Valley, California and Dixie Valley, Nevada. Results indicate that actual ETg rates from desert playas are significantly below the upper detection limits provided by the BREB- and EC-based micrometeorological measurements. Discharge from desert playas contribute less than 2 percent of total groundwater discharge from Dixie and Death Valleys, which suggests discharge from desert playas is negligible in other basins. Numerical simulation results also show that ETg from desert playas primarily is limited by differences in hydraulic properties between alluvial fan and playa sediments and, to a lesser extent, by salinity-based groundwater density contrasts.

Construction of 3-D geologic framework and textural models for Cuyama Valley groundwater basin, California

USGS Publications Warehouse

Sweetkind, Donald S.; Faunt, Claudia C.; Hanson, Randall T.

2013-01-01

Groundwater is the sole source of water supply in Cuyama Valley, a rural agricultural area in Santa Barbara County, California, in the southeasternmost part of the Coast Ranges of California. Continued groundwater withdrawals and associated water-resource management concerns have prompted an evaluation of the hydrogeology and water availability for the Cuyama Valley groundwater basin by the U.S. Geological Survey, in cooperation with the Water Agency Division of the Santa Barbara County Department of Public Works. As a part of the overall groundwater evaluation, this report documents the construction of a digital three-dimensional geologic framework model of the groundwater basin suitable for use within a numerical hydrologic-flow model. The report also includes an analysis of the spatial variability of lithology and grain size, which forms the geologic basis for estimating aquifer hydraulic properties. The geologic framework was constructed as a digital representation of the interpreted geometry and thickness of the principal stratigraphic units within the Cuyama Valley groundwater basin, which include younger alluvium, older alluvium, and the Morales Formation, and underlying consolidated bedrock. The framework model was constructed by creating gridded surfaces representing the altitude of the top of each stratigraphic unit from various input data, including lithologic and electric logs from oil and gas wells and water wells, cross sections, and geologic maps. Sediment grain-size data were analyzed in both two and three dimensions to help define textural variations in the Cuyama Valley groundwater basin and identify areas with similar geologic materials that potentially have fairly uniform hydraulic properties. Sediment grain size was used to construct three-dimensional textural models that employed simple interpolation between drill holes and two-dimensional textural models for each stratigraphic unit that incorporated spatial structure of the textural data.

Using 3D geological modelling and geochemical mixing models to characterise alluvial aquifer recharge sources in the upper Condamine River catchment, Queensland, Australia.

PubMed

Martinez, Jorge L; Raiber, Matthias; Cendón, Dioni I

2017-01-01

The influence of mountain front recharge on the water balance of alluvial valley aquifers located in upland catchments of the Condamine River basin in Queensland, Australia, is investigated through the development of an integrated hydrogeological framework. A combination of three-dimensional (3D) geological modelling, hydraulic gradient maps, multivariate statistical analyses and hydrochemical mixing calculations is proposed for the identification of hydrochemical end-members and quantification of the relative contributions of each end-member to alluvial aquifer recharge. The recognised end-members correspond to diffuse recharge and lateral groundwater inflows from three hydrostratigraphic units directly connected to the alluvial aquifer. This approach allows mapping zones of potential inter-aquifer connectivity and areas of groundwater mixing between underlying units and the alluvium. Mixing calculations using samples collected under baseflow conditions reveal that lateral contribution from a regional volcanic aquifer system represents the majority (41%) of inflows to the alluvial aquifer. Diffuse recharge contribution (35%) and inflow from two sedimentary bedrock hydrostratigraphic units (collectively 24%) comprise the remainder of major recharge sources. A detailed geochemical assessment of alluvial groundwater evolution along a selected flowpath of a representative subcatchment of the Condamine River basin confirms mixing as a key process responsible for observed spatial variations in hydrochemistry. Dissolution of basalt-related minerals and dolomite, CO 2 uptake, ion-exchange, precipitation of clay minerals, and evapotranspiration further contribute to the hydrochemical evolution of groundwater in the upland alluvial aquifer. This study highlights the benefits of undertaking an integrated approach that combines multiple independent lines of evidence. The proposed methods can be applied to investigate processes associated with inter-aquifer mixing, including groundwater contamination resulting from depressurisation of underlying geological units hydraulically connected to the shallower water reservoirs. Copyright © 2016 Elsevier B.V. All rights reserved.

Groundwater-flow budget for the lower Apalachicola-Chattahoochee-Flint River Basin in southwestern Georgia and parts of Florida and Alabama, 2008–12

USGS Publications Warehouse

Jones, L. Elliott; Painter, Jaime A.; LaFontaine, Jacob H.; Sepúlveda, Nicasio; Sifuentes, Dorothy F.

2017-12-29

As part of the National Water Census program in the Apalachicola-Chattahoochee-Flint (ACF) River Basin, the U.S. Geological Survey evaluated the groundwater budget of the lower ACF, with particular emphasis on recharge, characterizing the spatial and temporal relation between surface water and groundwater, and groundwater pumping. To evaluate the hydrologic budget of the lower ACF River Basin, a groundwater-flow model, constructed using MODFLOW-2005, was developed for the Upper Floridan aquifer and overlying semiconfining unit for 2008–12. Model input included temporally and spatially variable specified recharge, estimated using a Precipitation-Runoff Modeling System (PRMS) model for the ACF River Basin, and pumping, partly estimated on the basis of measured agricultural pumping rates in Georgia. The model was calibrated to measured groundwater levels and base flows, which were estimated using hydrograph separation.The simulated groundwater-flow budget resulted in a small net cumulative loss of groundwater in storage during the study period. The model simulated a net loss in groundwater storage for all the subbasins as conditions became substantially drier from the beginning to the end of the study period. The model is limited by its conceptualization, the data used to represent and calibrate the model, and the mathematical representation of the system; therefore, any interpretations should be considered in light of these limitations. In spite of these limitations, the model provides insight regarding water availability in the lower ACF River Basin.

Research Spotlight: Groundwater is being depleted rapidly in California's Central Valley

NASA Astrophysics Data System (ADS)

Tretkoff, Ernie

2011-03-01

Groundwater is being depleted in California's Central Valley at a rapid rate, according to data from the Gravity Recovery and Climate Experiment (GRACE) satellite. Famiglietti et al. analyzed 78 months of GRACE data covering October 2003 to March 2010 to estimate water storage changes in California's Sacramento and San Joaquin river basins. They found that the basins are losing water at a rate of about 30 millimeters per year equivalent water height, or a total of about 30 cubic kilometers over the 78-month period. Furthermore, they found that two thirds of this loss, or a total of 20 cubic kilometers for the study period, came from groundwater depletion in the Central Valley. Quantifying groundwater depletion can be challenging in many areas because of a lack of monitoring infrastructure and reporting requirements; the study shows that satellite-based monitoring can be a useful way to track groundwater volumes. The authors warn that the current rate of groundwater depletion in the Central Valley may be unsustainable and could have “potentially dire consequences for the economic and food security of the United States.” (Geophysical Research Letters, doi:10.1029/2010GL046442, 2011)

Geophysical logging of bedrock wells for geothermal gradient characterization in New Hampshire, 2013

USGS Publications Warehouse

Degnan, James R.; Barker, Gregory; Olson, Neil; Wilder, Leland

2014-01-01

Maximum groundwater temperatures at the bottom of the logs ranged from 11.2 to 15.4 degrees Celsius. Geothermal gradients were generally higher than those typically reported for other water wells in the United States. Some of the high gradients were associated with high natural gamma emissions. Groundwater flow was discernible in 4 of the 10 wells studied but only obscured the part of the geothermal gradient signal where groundwater actually flowed into, out of, or through the well. Temperature gradients varied by mapped bedrock type but can also vary by localized differences in mineralogy or rock type within the wells.

Preliminary three-dimensional geohydrologic framework of the San Antonio Creek Groundwater Basin, Santa Barbara County, California

NASA Astrophysics Data System (ADS)

Cromwell, G.; Sweetkind, D. S.; O'leary, D. R.

2017-12-01

The San Antonio Creek Groundwater Basin is a rural agricultural area that is heavily dependent on groundwater to meet local water demands. The U.S. Geological Survey (USGS) is working cooperatively with Santa Barbara County and Vandenberg Air Force Base to assess the quantity and quality of the groundwater resources within the basin. As part of this assessment, an integrated hydrologic model that will help stakeholders to effectively manage the water resources in the basin is being developed. The integrated hydrologic model includes a conceptual model of the subsurface geology consisting of stratigraphy and variations in lithology throughout the basin. The San Antonio Creek Groundwater Basin is a relatively narrow, east-west oriented valley that is structurally controlled by an eastward-plunging syncline. Basin-fill material beneath the valley floor consists of relatively coarse-grained, permeable, marine and non-marine sedimentary deposits, which are underlain by fine-grained, low-permeability, marine sedimentary rocks. To characterize the system, surficial and subsurface geohydrologic data were compiled from geologic maps, existing regional geologic models, and lithology and geophysical logs from boreholes, including two USGS multiple-well sites drilled as part of this study. Geohydrologic unit picks and lithologic variations are incorporated into a three-dimensional framework model of the basin. This basin (model) includes six geohydrologic units that follow the structure and stratigraphy of the area: 1) Bedrock - low-permeability marine sedimentary rocks; 2) Careaga Formation - fine to coarse grained near-shore sandstone; 3) Paso Robles Formation, lower portion - sandy-gravely deposits with clay and limestone; 4) Paso Robles Formation, middle portion - clayey-silty deposits; 5) Paso Robles Formation, upper portion - sandy-gravely deposits; and 6) recent Quaternary deposits. Hydrologic data show that the upper and lower portions of the Paso Robles Formation are the primary grou­ndwater-bearing units within the basin, and that the fine-grained layer within this Formation locally restricts vertical groundwater flow.

Practical performance and its efficiency of arsenic removal from groundwater using Fe-Mn binary oxide.

PubMed

Chang, Fangfang; Qu, Jiuhui; Liu, Ruiping; Zhao, Xu; Lei, Pengju

2010-01-01

A treatment unit packed by granular adsorbent of Fe-Mn binary oxide incorporated into diatomite (FMBO(1:1)-diatomite) was studied to remove arsenic from anaerobic groundwater without any pre-treatment or post-treatment. The raw anaerobic groundwater containing 35-45 microg/L of arsenic was collected from suburb of Beijing. Arsenic (III) constituted roughly 60%-80% of the total arsenic content. Approximately 7,000 bed volumes (ratio of effluent volume to adsorbent volume) treated water with arsenic concentration below 10 microg/L were produced in the operation period of four months. The regeneration of FMBO (1:1)-diatomite had been operated for 15 times. In the first stage, the regeneration process significantly improved the adsorption capacity of FMBO (1:1)-diatomite. With increased loading amount of Fe-Mn binary oxide, the adsorption capacity for arsenic decreased 20%-40%. Iron and manganese in anaerobic groundwater were oxidized and adsorptive filtrated by FMBO (1:1)-diatomite efficiently. The final concentrations of iron and manganese in effluents were nearly zero. The continued safe performance of the treatment units proved that adsorbent FMBO (1:1)-diatomite had high oxidation ability and exhibited strong adsorptive filtration.

Leaching of plutonium from a radioactive waste glass by eight groundwaters from the western United States

USGS Publications Warehouse

Rees, T.F.; Cleveland, J.M.; Nash, K.L.

1985-01-01

The leachability of a radioactive waste glass formulated to Battelle Pacific Northwest Laboratory specification 80-270 has been studied using eight actual groundwaters with a range of chemical compositions as leachants. Waters collected from the Grande Ronde Basalt (Washington State) and from alluvial deposits in the Hualapai Valley (Arizona) were the most effective at removing plutonium from this glass. Leaching was shown to be incongruent; plutonium was removed from the glass more slowly than the overall glass matrix. The results of these experiments indicate the need to study the leachability of actual waste forms using the actual projected groundwaters that are most likely to come into contact with the waste should a radioactive waste repository be breached.

Calendar Year 2007 Resource Conservation and Recovery Act Annual Monitoring Report for the U.S. Department of Energy Y-12 National Security Complex, Oak Ridge, Tennessee - RCRA Post-Closure Permit Nos. TNHW-113, TNHW-116, and TNHW-128

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elvado Environmental

2008-02-01

This report contains groundwater quality monitoring data obtained during calendar year (CY) 2007 at the following hazardous waste treatment, storage, and disposal (TSD) units located at the US Department of Energy (DOE) Y-12 National Security Complex (hereafter referenced as Y-12) in Oak Ridge, Tennessee; this S-3 Site, Oil Landfarm, Bear Creek Burial Grounds/Walk-In Pits (BCBG/WIP), Eastern S-3 Site Plume, Chestnut Ridge Security Pits (CRSP), Chestnut Ridge Sediment Disposal Baste (CRSDB), few Hollow Quarry (KHQ), and East Chestnut Ridge Waste Pile (ECRWP). Hit monitoring data were obtained in accordance with the applicable Resource Conservation and Recovery Act of 1976 (RCRA) hazardousmore » waste post-closure permit (PCP). The Tennessee Department of Environment and Conservation (TDEC) - Division of Solid Waste Management issued the PCPs to define the requirements for RCRA post-closure inspection, maintenance, and groundwater monitoring at the specified TSD units located within the Bear Creek Hydrogeologic Regime (PCP no. TNHW-116), Upper East Fork Poplar Creek Hydrogeologic Regime (PCP no. TNHW-113), and Chestnut Ridge Hydrogeologic Regime (PCP no. TNHW-128). Each PCP requires the Submittal of an annual RCRA groundwater monitoring report containing the groundwater sampling information and analytical results obtained at each applicable TSD unit during the preceding CY, along with an evaluation of groundwater low rates and directions and the analytical results for specified RCRA groundwater target compounds; this report is the RCRA annual groundwater monitoring report for CY 2007. The RCRA post-closure groundwater monitoring requirements specified in the above-referenced PCP for the Chestnut Ridge Regime replace those defined in the previous PCP (permit no. TNHW-088), which expired on September 18, 2005, but remained effective until the TDEC issued the new PCP in September 2006. The new PCP defines site-specific groundwater sampling and analysis requirements for the CRSDB, CRSP, and KHQ that differ from those established under the expired PCP, including modified suites of laboratory analytes (RCRA groundwater target compounds) for each site and annual rather than semiannual sampling frequencies for the CRSDB and KHQ. The new PCP also specifies the RCRA post-closure groundwater monitoring requirements for the ECRWP, a closed TSD unit that was not addressed in the expired PCP.« less

Spatial pattern of groundwater arsenic occurrence and association with bedrock geology in greater augusta, maine

USGS Publications Warehouse

Yang, Q.; Jung, H.B.; Culbertson, C.W.; Marvinney, R.G.; Loiselle, M.C.; Locke, D.B.; Cheek, H.; Thibodeau, H.; Zheng, Yen

2009-01-01

In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (100-101 km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed, and 31% of the sampled wells have arsenic concentrations >10 ??g/L. The probability of [As] exceeding 10 ??g/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (???40%). This probability differs significantly (p < 0.001) from those in the Silurian - Ordovician sandstone (24%), the Devonian granite (15%), and the Ordovician - Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium, and high arsenic occurrences in four cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (???1135 km2) are at risk of exposure to >10 ??g/L arsenic in groundwater. ?? 2009 American Chemical Society.

Spatial Pattern of Groundwater Arsenic Occurrence and Association with Bedrock Geology in Greater Augusta, Maine, USA

PubMed Central

Yang, Qiang; Jung, Hun Bok; Culbertson, Charles W.; Marvinney, Robert G.; Loiselle, Marc C.; Locke, Daniel B.; Cheek, Heidi; Thibodeau, Hilary; Zheng, Yan

2009-01-01

In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (100-101 km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed. 31% of the sampled wells have arsenic >10 μg/L. The probability of [As] exceeding 10 μg/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (~40%). This probability differs significantly (p<0.001) from those in the Silurian-Ordovician sandstone (24%), the Devonian granite (15%) and the Ordovician-Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium and high arsenic occurrences in 4 cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (~1135 km2) are at risk of exposure to >10 μg/L arsenic in groundwater. PMID:19475939

Spatial pattern of groundwater arsenic occurrence and association with bedrock geology in greater Augusta, Maine.

PubMed

Yang, Qiang; Jung, Hun Bok; Culbertson, Charles W; Marvinney, Robert G; Loiselle, Marc C; Locke, Daniel B; Cheek, Heidi; Thibodeau, Hilary; Zheng, Yan

2009-04-15

In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (10(0)-10(1) km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed, and 31% of the sampled wells have arsenic concentrations >10 microg/L. The probability of [As] exceeding 10 microg/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (approximately 40%). This probability differs significantly (p < 0.001) from those in the Silurian-Ordovician sandstone (24%),the Devonian granite (15%), and the Ordovician-Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium, and high arsenic occurrences in four cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (approximately 1135 km2) are at risk of exposure to >10 microg/L arsenic in groundwater.

Interactions of water quality and integrated groundwater management: exampled from the United States

USDA-ARS?s Scientific Manuscript database

Groundwater is available in many parts of the world, but the quality of the water may limit its use. Contaminants can limit the use of groundwater through concerns associated with human health, aquatic health, economic costs, or even societal perception. Given this broad range of concerns, this chap...

Modeling the Effects of Sea-Level Rise on Groundwater Levels in Coastal New Hampshire

NASA Astrophysics Data System (ADS)

Jacobs, J. M.; Knott, J. F.; Daniel, J.; Kirshen, P. H.

2017-12-01

Coastal communities with high population density and low topography are vulnerable from sea-level rise (SLR) caused by climate change. Groundwater in coastal communities will rise with sea level impacting water quality, the structural integrity of infrastructure, and natural ecosystem health. SLR-induced groundwater rise has been studied in areas of high aquifer transmissivity and in low-lying areas immediately along the coast. In this regional study, we investigate SLR-induced groundwater rise in a coastal area characterized by shallow unconsolidated deposits overlying fractured bedrock, typical of the glaciated northeast United States. MODFLOW, a numerical groundwater-flow model, is used with groundwater observations, lidar topography, surface-water hydrology, and groundwater withdrawals to investigate SLR-induced changes in groundwater levels and vadose-zone thickness in New Hampshire's Seacoast. The SLR groundwater signal is detected up to 5 km from the coast, more than 3 times farther inland than projected surface-water flooding associated with SLR. Relative groundwater rise ranges from 38 to 98% of SLR within 1 km of the shoreline and drops below 4% between 4 and 5 km from the coast. The largest magnitude of SLR-induced groundwater rise occurs in the marine and estuarine deposits and land areas with tidal water bodies on three sides. In contrast, groundwater rise is dampened near streams. Groundwater inundation caused by 2 m of SLR is projected to contribute 48% of the total land inundation area in the City of Portsmouth with consequences for built and natural resources. Freshwater wetlands are projected to expand 3% by year 2030 increasing to 25% by year 2100 coupled with water-depth increases. These results imply that underground infrastructure and natural resources in coastal communities will be impacted by rising groundwater much farther inland than previously thought when considering only surface-water flooding from SLR.

A simple method for estimating basin-scale groundwater discharge by vegetation in the basin and range province of Arizona using remote sensing information and geographic information systems

USGS Publications Warehouse

Tillman, F.D.; Callegary, J.B.; Nagler, P.L.; Glenn, E.P.

2012-01-01

Groundwater is a vital water resource in the arid to semi-arid southwestern United States. Accurate accounting of inflows to and outflows from the groundwater system is necessary to effectively manage this shared resource, including the important outflow component of groundwater discharge by vegetation. A simple method for estimating basin-scale groundwater discharge by vegetation is presented that uses remote sensing data from satellites, geographic information systems (GIS) land cover and stream location information, and a regression equation developed within the Southern Arizona study area relating the Enhanced Vegetation Index from the MODIS sensors on the Terra satellite to measured evapotranspiration. Results computed for 16-day composited satellite passes over the study area during the 2000 through 2007 time period demonstrate a sinusoidal pattern of annual groundwater discharge by vegetation with median values ranging from around 0.3 mm per day in the cooler winter months to around 1.5 mm per day during summer. Maximum estimated annual volume of groundwater discharge by vegetation was between 1.4 and 1.9 billion m3 per year with an annual average of 1.6 billion m3. A simplified accounting of the contribution of precipitation to vegetation greenness was developed whereby monthly precipitation data were subtracted from computed vegetation discharge values, resulting in estimates of minimum groundwater discharge by vegetation. Basin-scale estimates of minimum and maximum groundwater discharge by vegetation produced by this simple method are useful bounding values for groundwater budgets and groundwater flow models, and the method may be applicable to other areas with similar vegetation types.

Bacterial Community Dynamics in Dichloromethane-Contaminated Groundwater Undergoing Natural Attenuation

PubMed Central

Wright, Justin; Kirchner, Veronica; Bernard, William; Ulrich, Nikea; McLimans, Christopher; Campa, Maria F.; Hazen, Terry; Macbeth, Tamzen; Marabello, David; McDermott, Jacob; Mackelprang, Rachel; Roth, Kimberly; Lamendella, Regina

2017-01-01

The uncontrolled release of the industrial solvent methylene chloride, also known as dichloromethane (DCM), has resulted in widespread groundwater contamination in the United States. Here we investigate the role of groundwater bacterial communities in the natural attenuation of DCM at an undisclosed manufacturing site in New Jersey. This study investigates the bacterial community structure of groundwater samples differentially contaminated with DCM to better understand the biodegradation potential of these autochthonous bacterial communities. Bacterial community analysis was completed using high-throughput sequencing of the 16S rRNA gene of groundwater samples (n = 26) with DCM contamination ranging from 0.89 to 9,800,000 μg/L. Significant DCM concentration-driven shifts in overall bacterial community structure were identified between samples, including an increase in the abundance of Firmicutes within the most contaminated samples. Across all samples, a total of 6,134 unique operational taxonomic units (OTUs) were identified, with 16 taxa having strong correlations with increased DCM concentration. Putative DCM degraders such as Pseudomonas, Dehalobacterium and Desulfovibrio were present within groundwater across all levels of DCM contamination. Interestingly, each of these taxa dominated specific DCM contamination ranges respectively. Potential DCM degrading lineages yet to be cited specifically as a DCM degrading organisms, such as the Desulfosporosinus, thrived within the most heavily contaminated groundwater samples. Co-occurrence network analysis revealed aerobic and anaerobic bacterial taxa with DCM-degrading potential were present at the study site. Our 16S rRNA gene survey serves as the first in situ bacterial community assessment of contaminated groundwater harboring DCM concentrations ranging over seven orders of magnitude. Diversity analyses revealed known as well as potentially novel DCM degrading taxa within defined DCM concentration ranges, indicating niche-specific responses of these autochthonous populations. Altogether, our findings suggest that monitored natural attenuation is an appropriate remediation strategy for DCM contamination, and that high-throughput sequencing technologies are a robust method for assessing the potential role of biodegrading bacterial assemblages in the apparent reduction of DCM concentrations in environmental scenarios. PMID:29213257

Integrated hydrochemical and geophysical studies for assessment of groundwater pollution in basaltic settings in Central India.

PubMed

Pujari, Paras R; Padmakar, C; SuriNaidu, L; Vaijnath, V U; Kachawe, Bhusan; Gurunadha Rao, V V S; Labhasetwar, P K

2012-05-01

The Pithampur Industrial sectors I, II, and III, located approximately, 45 km from Indore in Central India have emerged as one of the largest industrial clusters in the region. Various types of industries ranging from automobiles to chemicals and pharmaceuticals have been set up in the region since 1990. Most of the industries have effluent treatment plants (ETP) for treating wastewater before its disposal on land and/or in water body. The present study is an attempt to assess the groundwater quality in the watersheds surrounding these industrial sectors to develop the baseline groundwater quality in order to enable the policy makers to facilitate decisions on the development of industries in this region. The industries are located in two sub-watersheds, namely, Gambhir river sub-watershed and Chambal river sub-watershed. Geologically, the study area is located in the Deccan traps of Cretaceous to Paleocene age. The different basaltic flow units underlie clayey soils varying in thickness from 2-3 m. The aquifer is mostly of unconfined nature. Samples have been collected from a network of observation wells set up in the watersheds. The water quality analysis of the groundwater samples has been carried out six times during three hydrological cycles of 2004, 2005, and 2006. The results indicate that a few observation wells in the vicinity of the industrial clusters have very high TDS concentration and exceed the Bureau of Indian Standards (BIS) guideline for TDS concentration. The contamination of groundwater has been more severe in the Gambhir watershed as compared to the Chambal watershed. The presence of the impermeable clay layers has resulted in a slow migration of contaminants from the sources. The findings reveal that there is no significant groundwater contamination in the Pithampur industrial sectors except in the vicinity of the industrial clusters, which indicates that there is good environmental space available for the expansion of industrial units in the Pithampur industrial hub.

Natural Remediation at Savannah River Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, C. M.; Van Pelt, R.

2002-02-25

Natural remediation is a general term that includes any technology or strategy that takes advantage of natural processes to remediate a contaminated media to a condition that is protective of human health and the environment. Natural remediation techniques are often passive and minimally disruptive to the environment. They are generally implemented in conjunction with traditional remedial solutions for source control (i.e., capping, stabilization, removal, soil vapor extraction, etc.). Natural remediation techniques being employed at Savannah River Site (SRS) include enhanced bio-remediation, monitored natural attenuation, and phytoremediation. Enhanced bio-remediation involves making nutrients available and conditions favorable for microbial growth. With propermore » precautions and feeding, the naturally existing microbes flourish and consume the contaminants. Case studies of enhanced bio-remediation include surface soils contaminated with PCBs and pesticides, and Volatile Organic Compound (VOC) contamination in both the vadose zone and groundwater. Monitored natural attenuation (MNA) has been selected as the preferred alternative for groundwater clean up at several SRS waste units. Successful implementation of MNA has been based on demonstration that sources have been controlled, groundwater modeling that indicates that plumes will not expand or reach surface water discharge points at levels that exceed regulatory limits, and continued monitoring. Phytoremediation is being successfully utilized at several SRS waste units. Phytoremediation involves using plants and vegetation to uptake, break down, or manage contaminants in groundwater or soils. Case studies at SRS include managing groundwater plumes of tritium and VOCs with pine trees that are native to the area. Significant decreases in tritium discharge to a site stream have been realized in one phytoremediation project. Studies of other vegetation types, methods of application, and other target contaminants are underway.« less

Groundwater-quality data for the Madera/Chowchilla–Kings shallow aquifer study unit, 2013–14: Results from the California GAMA Program

USGS Publications Warehouse

Shelton, Jennifer L.; Fram, Miranda S.

2017-02-03

Groundwater quality in the 2,390-square-mile Madera/Chowchilla–Kings Shallow Aquifer study unit was investigated by the U.S. Geological Survey from August 2013 to April 2014 as part of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Program’s Priority Basin Project. The study was designed to provide a statistically unbiased, spatially distributed assessment of untreated groundwater quality in the shallow aquifer systems of the Madera, Chowchilla, and Kings subbasins of the San Joaquin Valley groundwater basin. The shallow aquifer system corresponds to the part of the aquifer system generally used by domestic wells and is shallower than the part of the aquifer system generally used by public-supply wells. This report presents the data collected for the study and a brief preliminary description of the results.Groundwater samples were collected from 77 wells and were analyzed for organic constituents, inorganic constituents, selected isotopic and age-dating tracers, and microbial indicators. Most of the wells sampled for this study were private domestic wells. Unlike groundwater from public-supply wells, the groundwater from private domestic wells is not regulated for quality in California and is rarely analyzed for water-quality constituents. To provide context for the sampling results, however, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory benchmarks established for drinking-water quality by the U.S. Environmental Protection Agency, the State of California, and the U.S. Geological Survey.Of the 319 organic constituents assessed in this study (90 volatile organic compounds and 229 pesticides and pesticide degradates), 17 volatile organic compounds and 23 pesticides and pesticide degradates were detected in groundwater samples; concentrations of all but 2 were less than the respective benchmarks. The fumigants 1,2-dibromo-3-chloropropane (DBCP) and 1,2-dibromoethane (EDB) were detected at concentrations above their respective regulatory benchmarks in samples from a total of four wells.Most detections of inorganic constituents were at concentrations or activities less than the respective benchmark levels. Five inorganic constituents were detected in groundwater samples from one or more wells at concentrations or activities greater than their respective regulatory, health-based benchmarks: arsenic, uranium, nitrate, adjusted gross alpha particle activity, and gross beta particle activity. Four inorganic constituents were detected in samples from one or more wells at concentrations or activities greater than their respective non-regulatory, health-based benchmarks: manganese, molybdenum, vanadium, and radon-222. Three inorganic constituents were detected in groundwater samples from one or more wells at concentrations greater than their respective non-regulatory, aesthetic-based benchmarks: iron, sulfate, and total dissolved solids.Microbial indicators (Escherichia coli, total coliform, and enterococci) were analyzed for presence or absence. The presence of Escherichia coli (E. coli) was not detected; the presence of total coliform was detected in samples from 10 of the 72 grid wells for which it was analyzed, and the presence of enterococci was detected in samples from 5 of the 73 grid wells analyzed.

Human Health Impact of Fluoride in Groundwater in the Chiang Mai Basin

NASA Astrophysics Data System (ADS)

Matsui, Y.; Takizawa, S.; Wattanachira, S.; Wongrueng, A.; Ibaraki, M.

2005-12-01

Chiang Mai Basin, in Northern Thailand, is known as a fluorotic area. Groundwater of the Chiang Mai Basin has been gradually replaced by contaminated surface water since the 1980's. People have been exposed to fluoride contaminated groundwater since that time. As a result, harmful health effects on dental and skeletal growth were observed in the 90's. These include dental and skeletal fluorosis. Dental fluorosis is characterized by yellow or white spots on teeth and pitting or mottled enamel, consequently causing the teeth to look unsightly. Skeletal fluorosis leads to changes in bone structure, making them extremely weak and brittle. The most severe form of this is known as ``crippling skeletal fluorosis,'' a condition that can cause immobility, muscle wasting, and neurological problems related to spinal cord compression. This study focuses on the problematic issue of the Chiang Mai Basin's groundwater from the viewpoint of fluoride occurrence and current health impacts. Chiang Mai and Lamphun Provinces comprise the Chiang Mai Basin. Fluoride rich granites or fluorite deposits are scattered across the mountainside of the Lamphun Province. Tropical savanna climate conditions with seasonal monsoons bring more than 1,000 mm of annual precipitation, which can prompt weathering of minerals containing fluoride. The Ping River dominates the Basin, and the main eastern tributary of the Ping River runs through the Lamphun Province. The Basin has geological units composed of lower semi-consolidated Tertiary fluvial and upper unconsolidated Quaternary alluvium deposits. The main aquifers are in the upper unconsolidated unit. High fluoride concentrations tend to be observed in the aquifer located in lower part of this unconsolidated unit. We have been investigating two areas in the Basin. These two locations are similar with respect to geological and hydrological settings. However, one area in which groundwater is Ca-bicarbonate dominant has a low fluoride occurrence. Groundwater of the other area contains a high fluoride concentration and is Na-bicarbonate dominant. We will present how naturally-occurring fluoride found in this groundwater has impacted the health of a large portion of residents in the Chiang Mai Basin, and we will explain the mechanism that differentiates Ca concentration, which controls fluoride concentration in groundwater, between different areas in the Basin.

Hydrogeochemical assessment of arsenic in groundwater and its policy implication: a case study in Terai Basin, Nepal

NASA Astrophysics Data System (ADS)

Gurung, J. K.; Upreti, B. N.; Kansakar, D. R.

2007-12-01

Arsenic contamination at levels above the WHO guideline (10 ìg/l) in groundwater is a worldwide problem due to its detrimental effects on health and now known to be a problem also in the Terai Basin of Nepal, posing a serious threat to more than 10 million people. The distribution of arsenic in the basin, however, is patchy. The study emphasizes on the three different types of research into an interdisciplinary package that can be immediately useful to government agencies in Nepal trying to deal with groundwater contamination. They are: hydrogeological assessment of water sources and flow, geochemical analysis of groundwater, and assessment of practical public policy. Basic geochemical analysis gives the abundance and distribution of arsenic along with other physico-chemical parameters of groundwater, whereas, the hydrogeological assessment as an integral part of this study that assist in determining process of mobilization or attenuation of arsenic. Arsenic levels and other key parameters mainly pH, electrical conductivity, chemical oxygen demand, iron, and biological parameter as E-coli were observed at the various locations with different transmissivity values. The study suggests that the flushing rate of an aquifer plays an important role in arsenic content. High flushing rates of an aquifer lead to low levels of arsenic, however the mechanism of this process is still under study. Transmissivity the property of an aquifer that measures the rate at which ground water moves horizontally through a unit is the main factor for controlling flushing. Concentration maps overlaying the base transmissivity map reveals relation of groundwater movement and arsenic concentration. Understanding the relationship between groundwater movement and arsenic content helps planners protect uncontaminated aquifers from future contamination. Also assessment of public policy related to groundwater has identified important changes needed in the existing policy.

Mathematical numeric models for assessing the groundwater pollution from Sanitary landfills

NASA Astrophysics Data System (ADS)

Petrov, Vasil; Stoyanov, Nikolay; Sotinev, Petar

2014-05-01

Landfills are among the most common sources of pollution in ground water. Their widespread deployment, prolonged usage and the serious damage they cause to all of the elements of the environment are the reasons, which make the study of the problem particularly relevant. Most dangerous of all are the open dumps used until the middle of the twentieth century, from which large amounts of liquid emissions flowed freely (landfill infiltrate). In recent decades, the problem is solved by the construction of sanitary landfills in which they bury waste or solid residue from waste utilization plants. The bottom and the sides of the sanitary landfills are covered with a protective waterproof screen made of clay and polyethylene and the landfill infiltrate is led outside through a drainage system. This method of disposal severely limits any leakage of gas and liquid emissions into the environment and virtually eliminates the possibility of contamination. The main topic in the conducted hydrogeological study was a quantitative assessment of groundwater pollution and the environmental effects of re-landfilling of an old open dump into a new sanitary landfill, following the example of the municipal landfill of Asenovgrad, Bulgaria. The study includes: 1.A set of drilling, geophysical and hydrogeological field and laboratory studies on: -the definition and designation of the spatial limits of the main hydrogeological units; -identification of filtration parameters and migration characteristics of the main hydrogeological units; -clarifying the conditions for the sustentation and drainage of groundwater; -determininng the structure of the filtration field; -identifying and assessing the size and the extent of groundwater contamination from the old open dump . 2.Mathematical numeric models of migration and entry conditions of contaminants below the bottom of the landfill unit, with which the natural protection of the geological environment, the protective effect of the engineering barriers of the sanitary landfill, and the potential risk of contamination of the groundwater were evaluated. The migration of contaminants through the zone of aeration and the engineering barriers are modeled with 2D models, and their potential distribution in groundwater - with 3D models. The models simulate the behavior of highly mobile and less mobile contaminants by the example of chloride and ammonium ions (Cl-and NH4 +).The mechanism of mass transfer is set in its full form: convective transport, accompanied by reversible elimination (sorption), mechanical dispersion (longitudinal and transverse), molecular diffusion and dilution. The concentration of the infiltrating under the bottom of the dump unit pollutants is set to exponentially decreasing function, determined by data from the monitoring. Two-dimensional models are developed using the computer program VS2DTI - v.1.3, and three-dimensional models by Modflow and MT3D-MS.dimensional models by Modflow and MT3D-MS.

Hydrogeology of the Canal Creek area, Aberdeen Proving Ground, Maryland

USGS Publications Warehouse

Oliveros, J.P.; Vroblesky, D.A.

1989-01-01

Geologic and borehole geophysical logs made at 77 sites show that the hydrogeologic framework of the study area consists of a sequence of unconsolidated sediments typical of the Coastal Plain of Maryland. Three aquifers and two confining units were delineated within the study area. From the surface down, they are: (1) the surficial aquifer; (2) the upper confining unit; (3) the Canal Creek aquifer; (4) the lower confining unit; and (5) the lower confined aquifer. The aquifer materials range from fine sand to coarse sand and gravel. Clay lenses were commonly found interfingered with the sand, isolating parts of the aquifers. All the units are continuous throughout the study area except for the upper confining unit, which crops out within the study area but is absent in updip outcrops. The unit also is absent within a Pleistocene paleochannel, where it has been eroded. The surficial and Canal Creek aquifers are hydraulically connected where the upper confining unit is absent, and a substantial amount of groundwater may flow between the two aquifers. Currently, no pumping stresses are known to affect the aquifers within the study area. Under current conditions, downward vertical hydraulic gradients prevail at topographic highs, and upward gradients typically prevail near surface-water bodies. Regionally, the direction of groundwater flow in the confined aquifers is to the east and southeast. Significant water level fluctuations correspond with seasonal variations in rainfall, and minor daily fluctuations reflect tidal cycles. (USGS)

Ground-water recharge in the arid and semiarid southwestern United States

USGS Publications Warehouse

Stonestrom, David A.; Constantz, Jim; Ferré, Ty P.A.; Leake, Stanley A.

2007-01-01

Ground-water recharge in the arid and semiarid southwestern United States results from the complex interplay of climate, geology, and vegetation across widely ranging spatial and temporal scales. Present-day recharge tends to be narrowly focused in time and space. Widespread water-table declines accompanied agricultural development during the twentieth century, demonstrating that sustainable ground-water supplies are not guaranteed when part of the extracted resource represents paleorecharge. Climatic controls on ground-water recharge range from seasonal cycles of summer monsoonal and winter frontal storms to multimillennial cycles of glacial and interglacial periods. Precipitation patterns reflect global-scale interactions among the oceans, atmosphere, and continents. Large-scale climatic influences associated with El Niño and Pacific Decadal Oscillations strongly, but irregularly, control weather in the study area, so that year-to-year variations in precipitation and ground-water recharge are large and difficult to predict. Proxy data indicate geologically recent periods of naturally occurring multidecadal droughts unlike any in the modern instrumental record. Any anthropogenically induced climate change will likely reduce ground-water recharge through diminished snowpack at higher elevations. Future changes in El Niño and monsoonal patterns, both crucial to precipitation in the study area, are highly uncertain in current models. Current land-use modifications influence ground-water recharge through vegetation, irrigation, and impermeable area. High mountain ranges bounding the study area—the San Bernadino Mountains and Sierra Nevada to the west, and the Wasatch and southern Colorado Rocky Mountains to the east—provide external geologic controls on ground-water recharge. Internal geologic controls stem from tectonic processes that led to numerous, variably connected alluvial-filled basins, exposure of extensive Paleozoic aquifers in mountainous recharge areas, and distinct modes of recharge in the Colorado Plateau and Basin and Range subregions.The chapters in this professional paper present (first) an overview of climatic and hydrogeologic framework (chapter A), followed by a regional analysis of ground-water recharge across the entire study area (chapter B). These are followed by an overview of site-specific case studies representing different subareas of the geographically diverse arid and semiarid southwestern United States (chapter C); the case studies themselves follow in chapters D–K. The regional analysis includes detailed hydrologic modeling within the framework of a high-resolution geographic-information system (GIS). Results from the regional analysis are used to explore both the distribution of ground-water recharge for mean climatic conditions as well as the influence of two climatic patterns—the El Niño-Southern Oscillation and Pacific Decadal Oscillation—that impart a high degree of variability to the hydrologic cycle. Individual case studies employ a variety of geophysical and geochemical techniques to investigate recharge processes and relate the processes to local geologic and climatic conditions. All of the case studies made use of naturally occurring tracers to quantify recharge. Thermal and geophysical techniques that were developed in the course of the studies are presented in appendices.The quantification of ground-water recharge in arid settings is inherently difficult due to the generally low amount of recharge, its spatially and temporally spotty nature, and the absence of techniques for directly measuring fluxes entering the saturated zone from the unsaturated zone. Deep water tables in arid alluvial basins correspond to thick unsaturated zones that produce up to millennial time lags between changes in hydrologic conditions at the land surface and subsequent changes in recharge to underlying ground water. Recent advances in physical, chemical, isotopic, and modeling techniques have fostered new types of recharge assessments. Chemical and isotopic techniques include an increasing variety of environmental tracers that are useful and robust. Physically based techniques include the use of heat as a tracer and computationally intensive geophysical imaging tools for characterizing hydrologic conditions in the unsaturated zone. Modeling-based techniques include spatially distributed water-budget computations using high-resolution remotely sensed and ground-based geographic data. Application of these techniques to arid and semiarid settings in the southwestern United States reveals distinct patterns of recharge corresponding to geologic setting, climatic and vegetative history, and land use. Analysis of recharge patterns shows that large expanses of alluvial basin floors are drying out under current climatic conditions, with little to no recharge to underlying ground water. Ground-water recharge occurs mainly beneath upland catchments in which thin soils overlie permeable bedrock, ephemeral channels in which flow may average only several hours per year, and active agricultural areas. The chapters in this professional paper represent a coordinated attempt to develop a better understanding of one of the Nation's most critical yet difficult-to-quantify renewable resources.

Ground-Water Flow Model for the Spokane Valley-Rathdrum Prairie Aquifer, Spokane County, Washington, and Bonner and Kootenai Counties, Idaho

USGS Publications Warehouse

Hsieh, Paul A.; Barber, Michael E.; Contor, Bryce A.; Hossain, Md. Akram; Johnson, Gary S.; Jones, Joseph L.; Wylie, Allan H.

2007-01-01

This report presents a computer model of ground-water flow in the Spokane Valley-Rathdrum Prairie (SVRP) aquifer in Spokane County, Washington, and Bonner and Kootenai Counties, Idaho. The aquifer is the sole source of drinking water for more than 500,000 residents in the area. In response to the concerns about the impacts of increased ground-water withdrawals resulting from recent and projected urban growth, a comprehensive study was initiated by the Idaho Department of Water Resources, the Washington Department of Ecology, and the U.S. Geological Survey to improve the understanding of ground-water flow in the aquifer and of the interaction between ground water and surface water. The ground-water flow model presented in this report is one component of this comprehensive study. The primary purpose of the model is to serve as a tool for analyzing aquifer inflows and outflows, simulating the effects of future changes in ground-water withdrawals from the aquifer, and evaluating aquifer management strategies. The scale of the model and the level of detail are intended for analysis of aquifer-wide water-supply issues. The SVRP aquifer model was developed by the Modeling Team formed within the comprehensive study. The Modeling Team consisted of staff and personnel working under contract with the Idaho Department of Water Resources, personnel working under contract with the Washington Department of Ecology, and staff of the U.S. Geological Survey. To arrive at a final model that has the endorsement of all team members, decisions on modeling approach, methodology, assumptions, and interpretations were reached by consensus. The ground-water flow model MODFLOW-2000 was used to simulate ground-water flow in the SVPR aquifer. The finite-difference model grid consists of 172 rows, 256 columns, and 3 layers. Ground-water flow was simulated from September 1990 through September 2005 using 181 stress periods of 1 month each. The areal extent of the model encompasses an area of approximately 326 square miles. For the most part, the model extent coincides with the 2005 revised extent of the Spokane Valley-Rathdrum Prairie aquifer as defined in a previous report. However, the model excludes Spirit and Hoodoo Valleys because of uncertainties about the ground-water flow directions in those valleys and the degree of hydraulic connection between the valleys and northern Rathdrum Prairie. The SVRP aquifer is considered to be a single hydrogeologic unit except in Hillyard Trough and the Little Spokane River Arm. In those areas, a continuous clay layer divides the aquifer into an upper, unconfined unit and a lower, confined unit. The model includes all known components of inflows to and outflows from the aquifer. Inflows to the SVRP aquifer include (1) recharge from precipitation, (2) inflows from tributary basins and adjacent uplands, (3) subsurface seepage and surface overflows from lakes that border the aquifer, (4) flow from losing segments of the Spokane River to the aquifer, (5) return percolation from irrigation, and (6) effluent from septic systems. Outflows from the SVRP aquifer include (1) ground-water withdrawals from wells, (2) flow from the aquifer to gaining segments of the Spokane River, (3) aquifer discharge to the Little Spokane River, and (4) subsurface outflow from the lower unit at the western limit of the model area near Long Lake. These inflow and outflow components are represented in the model by using MODFLOW-2000 packages. The parameter-estimation program PEST was used to calibrate the SVRP aquifer model. PEST implements a nonlinear least-squares regression method to estimate model parameters so that the differences between measured and simulated quantities are minimized with respect to an optimal criterion. Calibration data include 1,573 measurements of water levels and 313 measurements of streamflow gains and losses along segments of the Spokane and Little Spokane Rivers. Model parameters estimated during calib

Superfund record of decision (EPA Region 3): US Defense General Supply Center, Operable Unit 9, Chesterfield County, VA, September 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-09-01

The decision document presents the selected interim remedial action for Operable Unit 9 (OU9) at the Defense General Supply Center (DGSC) in Chesterfield County, Virginia near Richmond. OU9 pertains to groundwater beneath Area 50, the Open Storage Area (OSA), and the Naitonal Guard Area (NGA). This operable unit is the third of nine operable units that are currently being addressed at the DGSC. OU9 addresses interim treatment and containment of groundwater in the upper and lower aquifers beneath Area 50, the OSA, and the NGA.

Water-quality assessment of part of the Upper Mississippi River basin, Minnesota and Wisconsin, environmental setting and study design

USGS Publications Warehouse

Stark, J.R.; Andrews, W.J.; Fallon, J.D.; Fong, A.L.; Goldstein, R.M.; Hanson, P.E.; Kroening, S.E.; Lee, K.E.

1996-01-01

Environmental stratification consists of dividing the study unit into subareas with homogeneous characteristics to assess natural and anthropogenic factors affecting water quality. The assessment of water quality in streams and in aquifers is based on the sampling design that compares water quality within homogeneous subareas defined by subbasins or aquifer boundaries. The study unit is stratified at four levels for the surface-water component: glacial deposit composition, surficial geology, general land use and land cover, and secondary land use. Ground-water studies emphasize shallow ground water where quality is most likely influenced by overlying land use and land cover. Stratification for ground-water sampling is superimposed on the distribution of shallow aquifers. For each aquifer and surface-water basin this stratification forms the basis for the proposed sampling design used in the Upper Mississippi River Basin National Water-Quality Assessment.

Structure, outcrop, and subcrop of the bedrock aquifers along the western margin of the Denver Basin, Colorado

USGS Publications Warehouse

Robson, Stanley G.; Van Slyke, George D.; Graham, Glenn

1998-01-01

Severe and prolonged droughts between 1961 and 1988, combined with increased demands for freshwater supplies in the United States, have resulted in a critical need to assess the potential for development of ground- and surface-water supplies. Rapid industrial growth and urban expansion have caused existing freshwater supplies to be used at or near maximum capacity. Begun in 1978, the Regional Aquifer-System Analysis (RASA) Program of the U.S. Geological Survey (USGS) is a systematic effort to study a number of the Nation's most important aquifer systems, which, in aggregate, underlie much of the country and represent an important component of the Nation's total water supply. The broad objective for each of the 28 studies in the program is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system.In 1988, as part of the RASA Program, the USGS began a 6-year study of the ground-water resources of parts of 11 States in the Eastern United States (Swain and others, 1991). The study was designated the Appalachian Valley and Piedmont Regional Aquifer-System Analysis (APRASA). The APRASA team investigated ground-water resources primarily in the unglaciated part of the Valley and Ridge, the Blue Ridge, the New England, and the Piedmont Physiographic Provinces (fig. 1). For the purposes of this report, the small area in the New England Physiographic Province that is within the study area in New Jersey and Pennsylvania was considered part of the Piedmont Physiographic Province. The results of the APRASA are contained in about 50 reports and abstracts, including reports on simulation of ground-water flow in three type areas, this atlas, and chapters in Professional Paper 1422. These chapters include the summary (Chapter A), descriptions of recharge rates and surface- and ground-water relations (Chapter B), hydrogeologic terranes in the Valley and Ridge Physiographic Province (Chapter C), and ground-water geochemistry (Chapter D).The purposes of this atlas are to summarize the hydrogeology, to describe an analysis of maps and well records, and to present a classification and map of the hydrogeologic terranes of the Blue Ridge and Piedmont Physiographic Provinces within the APRASA study area. Hydrogeologic terranes are defined for this atlas as regionally mappable areas characterized by similar water-yielding properties of a grouping of selected rock types. The hydrogeologic terranes represent areas of distinct hydrologic character. The terranes are intended to help water users locate and develop adequate water supplies and to help hydrologists interpret the regional hydrogeology.Previous investigations provide maps and descriptions of the geologic units, describe the local quantity and quality of ground water within these units, and establish the statistical methods for comparing the water-yielding propertics of these units. State geologic maps show the distribution of geologic units at a scale of 1:500,000 for Alabama (Osborne and others, 1989), Georgia (Lawton and others, 1976), North Carolina (Brown and Parker, 1985), and Virginia (Calver and Hobbs, 1963). State maps show geologic units at a scale of 1:250,000 for Maryland (Cleaves and others, 1968), New Jersey (Lewis and Kummel, 1912), Pennsylvania (Berg and others, 1980), South Carolina (Overstreet and Bell, 1965), Tennessee (Hardeman, 1966), and West Virginia (Cardwell and others, 1968). Quadrangle geologic maps show geologic units at a scale of 1:24,000 for parts of Delaware within the APRASA area (Woodruff and Thompson, 1972, 1975). Many reports have been published describing the groundwater resources of a county, parts of a county, multi-county areas, or river basins.The statistical methods used in this atlas are based largely on those used by Helsel and Hirsch (1992) and by Knopman (1990, p. 7-9). In her analysis of well records in the USGS Ground-Water Site Inventory (GWSI) data base, Knopman (1990) ranked factors that must be taken into account when assessing the water-yielding potential of the rocks in the Valley and Ridge, the Blue Ridge, and the Piedmont Physiographic Provinces in Pennsylvania. Readers are referred to Helsel and Hirsch (1992) and Knopman (1990) for details regarding statistical methods.

The influence of fish ponds and salinization on groundwater quality in the multi-layer coastal aquifer system in Israel

NASA Astrophysics Data System (ADS)

Tal, A.; Weinstein, Y.; Yechieli, Y.; Borisover, M.

2017-08-01

This study focuses on the impact of surface reservoirs (fish ponds) on a multi aquifer coastal system, and the relation between the aquifer and the sea. The study was conducted in an Israeli Mediterranean coastal aquifer, which includes a sandy phreatic unit and two confined calcareous sandstone units. The geological description is based on 52 wells, from which 33 samples were collected for stable isotope analysis and 25 samples for organic and inorganic parameters. Hydraulic head and chemical measurements suggest that there is an hydraulic connection between the fish ponds above the aquifer and the phreatic unit, whereas the connection with the confined units is very limited. The phreatic unit is characterized by a low concentration of oxygen and high concentrations of ammonium and phosphate, while the confined units are characterized by higher oxygen and much lower ammonium and phosphate concentrations. Organic matter fluorescence was found to be a tool to distinguish the contribution of the pond waters, whereby a pond water signature (characterized by proteinaceous (tryptophan-like) and typical humic-matter fluorescence) was found in the phreatic aquifer. The phreatic unit is also isotopically enriched, similar to pond waters, with δ18O of -1‰ and δD of -4.6‰, indicating enhanced evaporation of the pond water before infiltration, whereas there is a depleted isotopic composition in the confined units (δ18O = -4.3‰, δD = -20.4‰), which are also OM-poor. The Phreeqc model was used for quantitative calculation of the effect of pond losses on the different units. The Dissolved Inorganic Nitrogen (DIN) in the upper unit increases downstream from the ponds toward the sea, probably due to organic matter degradation, suggesting contribution of DIN from shallow groundwater flow to the sea. 87Sr/86Sr and Mg/Ca in the brackish and saline groundwater of the lower confined units increase toward seawater value, suggesting that the salinization process in the region is connected to seawater intrusion and not to old brine from the underlying Cretaceous aquitard.

Geospatial data to support analysis of water-quality conditions in basin-fill aquifers in the southwestern United States

USGS Publications Warehouse

McKinney, Tim S.; Anning, David W.

2009-01-01

The Southwest Principal Aquifers study area consists of most of California and Nevada and parts of Utah, Arizona, New Mexico, and Colorado; it is about 409,000 square miles. The Basin-fill aquifers extend through about 201,000 square miles of the study area and are the primary source of water for cities and agricultural communities in basins in the arid and semiarid southwestern United States (Southwest). The demand on limited ground-water resources in areas in the southwestern United States has increased significantly. This increased demand underscores the importance of understanding factors that affect the water quality in basin-fill aquifers in the region, which are being studied through the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program. As a part of this study, spatial datasets of natural and anthropogenic factors that may affect ground-water quality of the basin-fill aquifers in the southwestern United States were developed. These data include physical characteristics of the region, such as geology, elevation, and precipitation, as well as anthropogenic factors, including population, land use, and water use. Spatial statistics for the alluvial basins in the Southwest have been calculated using the datasets. This information provides a foundation for the development of conceptual and statistical models that relate natural and anthropogenic factors to ground-water quality across the Southwest. A geographic information system (GIS) was used to determine and illustrate the spatial distribution of these basin-fill variables across the region. One hundred-meter resolution raster data layers that represent the spatial characteristics of the basins' boundaries, drainage areas, population densities, land use, and water use were developed for the entire Southwest.

Comparative study of urban development and groundwater condition in coastal areas of Buenos Aires, Argentina

NASA Astrophysics Data System (ADS)

Rodrigues Capítulo, Leandro; Carretero, Silvina C.; Kruse, Eduardo E.

2017-08-01

The geomorphological evolution of a sand-dune barrier in Buenos Aires, Argentina, is analyzed as a factor regulating the fresh groundwater reserves available. The impact of geomorphological evolution and the consequences for the social and economic development of two coastal areas are assessed. This is one of the most important tourist destinations in the country; for study purposes, it was divided into a northern sector and a southern sector. In the southern sector, the exploitable groundwater is associated with the Holocene and upper Pleistocene geomorphological evolution, which generated three interrelated aquifer units, constituting a system whose useful thickness reaches at least 45 m. In contrast, the northern sector is restricted to two Holocene aquifer units, whose total thickness is on the order of 12 m. The morphological characteristics and the occurrence of the largest fresh groundwater reserves in the southern sector are indicators of better conditions for economic growth, which is mainly reflected on the expansion of real estate ventures. The relationships of transmissivity vs area of real estate ventures (Arev), and total water consumption vs Arev, are indicators for the sustainable management of the water resources. The approach chosen may be used by decision makers in other regions to assess the feasibility of future tourism projects on the basis of the availability of water resources associated with geomorphological features.

Organizing groundwater regimes and response thresholds by soils: A framework for understanding runoff generation in a headwater catchment

Treesearch

John P. Gannon; Scott W. Bailey; Kevin J. McGuire

2014-01-01

A network of shallow groundwater wells in a headwater catchment at the Hubbard Brook Experimental Forest in New Hampshire, U.S. was used to investigate the hydrologic behavior of five distinct soil morphological units. The soil morphological units were hypothesized to be indicative of distinct water table regimes. Water table fluctuations in the wells were...

The economics of optimal urban groundwater management in southwestern USA

NASA Astrophysics Data System (ADS)

Hansen, Jason K.

2012-08-01

Groundwater serves as the primary water source for approximately 80% of public water systems in the United States, and for many more as a secondary source. Traditionally management relies on groundwater to meet rising demand by increasing supply, but climate uncertainty and population growth require more judicious management to achieve efficiency and sustainability. Over-pumping leads to groundwater overdraft and jeopardizes the ability of future users to depend on the resource. Optimal urban groundwater pumping can play a role in solving this conundrum. This paper investigates to what extent and under what circumstances controlled pumping improves social welfare. It considers management in a hydro-economic framework and finds the optimal pumping path and the optimal price path. These allow for the identification of the social benefit of controlled pumping, and the scarcity rent, which is one tool to sustainably manage groundwater resources. The model is numerically illustrated with a case study from Albuquerque, New Mexico (USA). The Albuquerque results indicate that, in the presence of strong demand growth, controlled pumping improves social welfare by 22%, extends use of the resource, and provides planners with a mechanism to advance the economic sustainability of groundwater.

Ground-water management under the appropriation doctrine. Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ralston, D.; Bruhl, E.J.

The purpose of the research is to better understand the characteristics of ground-water management under the prior-appropriation doctrine in the western United States. The general objective is to summarize the legal and administrative controls on ground-water use in eight western states and to compare the impacts of these controls on ground water systems.

Groundwater quality in the glacial aquifer system, United States

USGS Publications Warehouse

Stackelberg, Paul E.

2017-12-07

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The glacial aquifer system constitutes one of the important areas being evaluated.

Hydrogeology of the Hawaiian islands

USGS Publications Warehouse

Gingerich, Stephen B.; Oki, Delwyn S.; Cabrera, Maria del Carmen; Lambán, Luis Javier; Valverde, Margarida

2011-01-01

Volcanic-rock aquifers are the most extensive and productive aquifers in the Hawaiian Islands. These aquifers contain different types of groundwater systems depending on the geologic setting in which they occur. The most common groundwater systems include coastal freshwater-lens systems in the dike-free flanks of the volcanoes and dike-impounded systems within the dike-intruded areas of the volcanoes. In some areas, a thick (hundreds of meters) freshwater lens may develop because of the presence of a coastal confining unit, or caprock, that impedes the discharge of groundwater from the volcanic-rock aquifer, or because the permeability of the volcanic rocks forming the aquifer is low. In other areas with low groundwater-recharge rates and that lack a caprock, the freshwater lens may be thin or brackish water may exist immediately below the water table. Dike-impounded groundwater systems commonly have high water levels (hundreds of meters above sea level) and contribute to the base flow of streams where the water table intersects the stream. Recent numerical modeling studies have enhanced the conceptual understanding of groundwater systems in the Hawaiian Islands.

Microorganisms as tracers in groundwater injection and recovery experiments: A review

USGS Publications Warehouse

Harvey, R.W.

1997-01-01

Modern day injection and recovery techniques designed to examine the transport behavior of microorganisms in groundwater have evolved from experiments conducted in the late 1800s, in which bacteria that form red or yellow pigments were used to trace flow paths through karst and fractured- rock aquifers. A number of subsequent groundwater hydrology studies employed bacteriophage that can be injected into aquifers at very high concentrations (e g., 1013 phage ml-1) and monitored through many log units of dilution to follow groundwater flow paths for great distances, particularly in karst terrain. Starting in the 1930s, microbial indicators of fecal contamination (particularly coliform bacteria and their coliphages) were employed as tracers to determine potential migration of pathogens in groundwater. Several injection and recovery experiments performed in the 1990s employed indigenous groundwater microorganisms (both cultured and uncultured) that are better able to survive under in situ conditions. Better methods for labeling native bacteria (e.g by stable isotope labeling or inserting genetic markers; such as the ability to cause ice nucleation) are being developed that will not compromise the organisms' viability during the experimental time course.

Conceptual model of the Great Basin carbonate and alluvial aquifer system

USGS Publications Warehouse

Heilweil, Victor M.; Brooks, Lynette E.

2011-01-01

A conceptual model of the Great Basin carbonate and alluvial aquifer system (GBCAAS) was developed by the U.S. Geological Survey (USGS) for a regional assessment of groundwater availability as part of a national water census. The study area is an expansion of a previous USGS Regional Aquifer Systems Analysis (RASA) study conducted during the 1980s and 1990s of the carbonate-rock province of the Great Basin. The geographic extent of the study area is 110,000 mi2, predominantly in eastern Nevada and western Utah, and includes 165 hydrographic areas (HAs) and 17 regional groundwater flow systems.A three-dimensional hydrogeologic framework was constructed that defines the physical geometry and rock types through which groundwater moves. The diverse sedimentary units of the GBCAAS study area are grouped into hydrogeologic units (HGUs) that are inferred to have reasonably distinct hydrologic properties due to their physical characteristics. These HGUs are commonly disrupted by large-magnitude offset thrust, strike-slip, and normal faults, and locally affected by caldera formation. The most permeable aquifer materials within the study area include Cenozoic unconsolidated sediments and volcanic rocks, along with Mesozoic and Paleozoic carbonate rocks. The framework was built by extracting and combining information from digital elevation models, geologic maps, cross sections, drill hole logs, existing hydrogeologic frameworks, and geophysical data.

Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA

USGS Publications Warehouse

Mills, Taylor J.; Mast, M. Alisa; Thomas, Judith C.; Keith, Gabrielle L.

2016-01-01

Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic materials into the shallow groundwater and surface water systems. This study presents groundwater chemistry and solid-phase geochemical data from the Uncompahgre River Basin in Western Colorado, an irrigated alluvial landscape underlain by Se-rich Cretaceous marine shale. We analyzed Se species, major and trace elements, and stable nitrogen and oxygen isotopes of nitrate in groundwater and aquifer sediments to examine processes governing selenium release and transport in the shallow groundwater system. Groundwater Se concentrations ranged from below detection limit (< 0.5 μg L− 1) to 4070 μg L− 1, and primarily are controlled by high groundwater nitrate concentrations that maintain oxidizing conditions in the aquifer despite low dissolved oxygen concentrations. High nitrate concentrations in non-irrigated soils and nitrate isotopes indicate nitrate is largely derived from natural sources in the Mancos Shale and alluvial material. Thus, in contrast to areas that receive substantial NO3 inputs through inorganic fertilizer application, Se mitigation efforts that involve limiting NO3 application might have little impact on groundwater Se concentrations in the study area. Soluble salts are the primary source of Se to the groundwater system in the study area at-present, but they constitute a small percentage of the total Se content of core material. Sequential extraction results indicate insoluble Se is likely composed of reduced Se in recalcitrant organic matter or discrete selenide phases. Oxidation of reduced Se species that constitute the majority of the Se pool in the study area could be a potential source of Se in the future as soluble salts are progressively depleted.

Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA.

PubMed

Mills, Taylor J; Mast, M Alisa; Thomas, Judith; Keith, Gabrielle

2016-10-01

Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic materials into the shallow groundwater and surface water systems. This study presents groundwater chemistry and solid-phase geochemical data from the Uncompahgre River Basin in Western Colorado, an irrigated alluvial landscape underlain by Se-rich Cretaceous marine shale. We analyzed Se species, major and trace elements, and stable nitrogen and oxygen isotopes of nitrate in groundwater and aquifer sediments to examine processes governing selenium release and transport in the shallow groundwater system. Groundwater Se concentrations ranged from below detection limit (<0.5μgL(-1)) to 4070μgL(-1), and primarily are controlled by high groundwater nitrate concentrations that maintain oxidizing conditions in the aquifer despite low dissolved oxygen concentrations. High nitrate concentrations in non-irrigated soils and nitrate isotopes indicate nitrate is largely derived from natural sources in the Mancos Shale and alluvial material. Thus, in contrast to areas that receive substantial NO3 inputs through inorganic fertilizer application, Se mitigation efforts that involve limiting NO3 application might have little impact on groundwater Se concentrations in the study area. Soluble salts are the primary source of Se to the groundwater system in the study area at-present, but they constitute a small percentage of the total Se content of core material. Sequential extraction results indicate insoluble Se is likely composed of reduced Se in recalcitrant organic matter or discrete selenide phases. Oxidation of reduced Se species that constitute the majority of the Se pool in the study area could be a potential source of Se in the future as soluble salts are progressively depleted. Published by Elsevier B.V.

Using hydrogeologic data to evaluate geothermal potential in the eastern Great Basin

USGS Publications Warehouse

Masbruch, Melissa D.; Heilweil, Victor M.; Brooks, Lynette E.

2012-01-01

In support of a larger study to evaluate geothermal resource development of high-permeability stratigraphic units in sedimentary basins, this paper integrates groundwater and thermal data to evaluate heat and fluid flow within the eastern Great Basin. Previously published information from a hydrogeologic framework, a potentiometric-surface map, and groundwater budgets was compared to a surficial heat-flow map. Comparisons between regional groundwater flow patterns and surficial heat flow indicate a strong spatial relation between regional groundwater movement and surficial heat distribution. Combining aquifer geometry and heat-flow maps, a selected group of subareas within the eastern Great Basin are identified that have high surficial heat flow and are underlain by a sequence of thick basin-fill deposits and permeable carbonate aquifers. These regions may have potential for future geothermal resources development.

Groundwater-Quality Data in the Antelope Valley Study Unit, 2008: Results from the California GAMA Program

USGS Publications Warehouse

Schmitt, Stephen J.; Milby Dawson, Barbara J.; Belitz, Kenneth

2009-01-01

Groundwater quality in the approximately 1,600 square-mile Antelope Valley study unit (ANT) was investigated from January to April 2008 as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001, and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The study was designed to provide a spatially unbiased assessment of the quality of raw groundwater used for public water supplies within ANT, and to facilitate statistically consistent comparisons of groundwater quality throughout California. Samples were collected from 57 wells in Kern, Los Angeles, and San Bernardino Counties. Fifty-six of the wells were selected using a spatially distributed, randomized, grid-based method to provide statistical representation of the study area (grid wells), and one additional well was selected to aid in evaluation of specific water-quality issues (understanding well). The groundwater samples were analyzed for a large number of organic constituents (volatile organic compounds [VOCs], gasoline additives and degradates, pesticides and pesticide degradates, fumigants, and pharmaceutical compounds), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), and radioactive constituents (gross alpha and gross beta radioactivity, radium isotopes, and radon-222). Naturally occurring isotopes (strontium, tritium, and carbon-14, and stable isotopes of hydrogen and oxygen in water), and dissolved noble gases also were measured to help identify the sources and ages of the sampled groundwater. In total, 239 constituents and water-quality indicators (field parameters) were investigated. Quality-control samples (blanks, replicates, and samples for matrix spikes) were collected at 12 percent of the wells, and the results for these samples were used to evaluate the quality of the data for the groundwater samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a noticeable source of bias in the data for the groundwater samples. Differences between replicate samples generally were within acceptable ranges, indicating acceptably low variability. Matrix spike recoveries were within acceptable ranges for most compoundsThis study did not evaluate the quality of water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, or blended with other waters to maintain water quality. Regulatory thresholds apply to water that is served to the consumer, not to raw groundwater. However, to provide some context for the results, concentrations of constituents measured in the raw groundwater were compared with regulatory and non-regulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH) and thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. Comparisons between data collected for this study and drinking-water thresholds are for illustrative purposes only, and are not indicative of compliance or non-compliance with drinking water standards. Most constituents that were detected in groundwater samples were found at concentrations below drinking-water thresholds. Volatile organic compounds (VOCs) were detected in about one-half of the samples and pesticides detected in about one-third of the samples; all detections of these constituents were below health-based thresholds. Most detections of trace elements and nutrients in samples from ANT wells were below health-based thresholds. Exceptions include: one detection of nitrite plus nitr

Groundwater flow pattern and related environmental phenomena in complex geologic setting based on integrated model construction

NASA Astrophysics Data System (ADS)

Tóth, Ádám; Havril, Tímea; Simon, Szilvia; Galsa, Attila; Monteiro Santos, Fernando A.; Müller, Imre; Mádl-Szőnyi, Judit

2016-08-01

Groundwater flow, driven, controlled and determined by topography, geology and climate, is responsible for several natural surface manifestations and affected by anthropogenic processes. Therefore, flowing groundwater can be regarded as an environmental agent. Numerical simulation of groundwater flow could reveal the flow pattern and explain the observed features. In complex geologic framework, where the geologic-hydrogeologic knowledge is limited, the groundwater flow model could not be constructed based solely on borehole data, but geophysical information could aid the model building. The integrated model construction was presented via the case study of the Tihany Peninsula, Hungary, with the aims of understanding the background and occurrence of groundwater-related environmental phenomena, such as wetlands, surface water-groundwater interaction, slope instability, and revealing the potential effect of anthropogenic activity and climate change. The hydrogeologic model was prepared on the basis of the compiled archive geophysical database and the results of recently performed geophysical measurements complemented with geologic-hydrogeologic data. Derivation of different electrostratigraphic units, revealing fracturing and detecting tectonic elements was achieved by systematically combined electromagnetic geophysical methods. The deduced information can be used as model input for groundwater flow simulation concerning hydrostratigraphy, geometry and boundary conditions. The results of numerical modelling were interpreted on the basis of gravity-driven regional groundwater flow concept and validated by field mapping of groundwater-related phenomena. The 3D model clarified the hydraulic behaviour of the formations, revealed the subsurface hydraulic connection between groundwater and wetlands and displayed the groundwater discharge pattern, as well. The position of wetlands, their vegetation type, discharge features and induced landslides were explained as environmental imprints of groundwater. The highly vulnerable wetlands and groundwater-dependent ecosystems have to be in the focus of water management and natural conservation policy.

Application of a geographic information system in analyzing the occurrence of atrazine in groundwater of the mid-continental United States

USGS Publications Warehouse

Burkart, M.R.; Kolpin, D.W.

1993-01-01

The US Geological Survey, US Department of Agriculture, and US Environmental Protection Agency are conducting research and regional assessments in support of policy alternatives intended to protect water resources from agricultural chemical contamination. The mid-continent was selected because of the intense row crop agriculture and associated herbicide application in this region. An application of a geographic information system is demonstrated for analyzing and comparing the distribution of estimated atrazine use to the detection rate of atrazine in groundwater. Understanding the relations between atrazine use and detection in groundwater is important in policy deliberations to protect water resources. Relational analyses between measures of chemical use and detection rate by natural resource units may provide insight into critical factors controlling the processes that result in groundwater contamination from agricultural chemicals. 

Evaluating Micrometeorological Estimates of Groundwater Discharge from Great Basin Desert Playas.

PubMed

Jackson, Tracie R; Halford, Keith J; Gardner, Philip M

2018-03-06

Groundwater availability studies in the arid southwestern United States traditionally have assumed that groundwater discharge by evapotranspiration (ET g ) from desert playas is a significant component of the groundwater budget. However, desert playa ET g rates are poorly constrained by Bowen ratio energy budget (BREB) and eddy-covariance (EC) micrometeorological measurement approaches. Best attempts by previous studies to constrain ET g from desert playas have resulted in ET g rates that are within the measurement error of micrometeorological approaches. This study uses numerical models to further constrain desert playa ET g rates that are within the measurement error of BREB and EC approaches, and to evaluate the effect of hydraulic properties and salinity-based groundwater density contrasts on desert playa ET g rates. Numerical models simulated ET g rates from desert playas in Death Valley, California and Dixie Valley, Nevada. Results indicate that actual ET g rates from desert playas are significantly below the uncertainty thresholds of BREB- and EC-based micrometeorological measurements. Discharge from desert playas likely contributes less than 2% of total groundwater discharge from Dixie and Death Valleys, which suggests discharge from desert playas also is negligible in other basins. Simulation results also show that ET g from desert playas primarily is limited by differences in hydraulic properties between alluvial fan and playa sediments and, to a lesser extent, by salinity-based groundwater density contrasts. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Groundwater quality in the Valley and Ridge and Piedmont and Blue Ridge carbonate-rock aquifers, eastern United States

USGS Publications Warehouse

Lindsey, Bruce; Belitz, Kenneth

2017-01-19

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Valley and Ridge and Piedmont and Blue Ridge carbonate-rock aquifers constitute two of the important areas being evaluated. One or more inorganic constituents with human-health benchmarks were detected at high concentrations in about 15 percent of the study area and at moderate concentrations in about 17 percent. Organic constituents were not detected at high concentrations in the study area. One or more organic constituents with human-health benchmarks were detected at moderate concentrations in about 2 percent of the study area.

Estimates of residence time and related variations in quality of ground water beneath Submarine Base Bangor and vicinity, Kitsap County, Washington

USGS Publications Warehouse

Cox, S.E.

2003-01-01

Estimates of residence time of ground water beneath Submarine Base Bangor and vicinity ranged from less than 50 to 4,550 years before present, based on analysis of the environmental tracers tritium, chlorofluorocarbons (CFCs), and carbon-14 (14C), in 33 ground-water samples collected from wells tapping the ground-water system. The concentrations of multiple environmental tracers tritium, CFCs, and 14C were used to classify ground water as modern (recharged after 1953), pre-modern (recharged prior to 1953), or indeterminate. Estimates of the residence time of pre-modern ground water were based on evaluation of 14C of dissolved inorganic carbon present in ground water using geochemical mass-transfer modeling to account for the interactions of the carbon in ground water with carbon of the aquifer sediments. Ground-water samples were obtained from two extensive aquifers and from permeable interbeds within the thick confining unit separating the sampled aquifers. Estimates of ground-water residence time for all ground-water samples from the shallow aquifer were less than 45 years and were classified as modern. Estimates of the residence time of ground water in the permeable interbeds within the confining unit ranged from modern to 4,200 years and varied spatially. Near the recharge area, residence times in the permeable interbeds typically were less than 800 years, whereas near the discharge area residence times were in excess of several thousand years. In the deeper aquifers, estimates of ground-water residence times typically were several thousand years but ranged from modern to 4,550 years. These estimates of ground-water residence time based on 14C were often larger than estimates of ground-water residence time developed by particle-tracking analysis using a ground-water flow model. There were large uncertainties?on the order of 1,000-2,000 years?in the estimates based on 14C. Modern ground-water tracers found in some samples from large-capacity production wells screened in the deeper aquifer may be the result of preferential ground-water pathways or induced downward flow caused by pumping stress. Spatial variations in water quality were used to develop a conceptual model of chemical evolution of ground water. Stable isotope ratios of deuterium and oxygen-18 in the 33 ground-water samples were similar, indicating similar climatic conditions and source of precipitation recharge for all of the sampled ground water. Oxidation of organic matter and mineral dissolution increased the concentrations of dissolved inorganic carbon and common ions in downgradient ground waters. However, the largest concentrations were not found near areas of ground-water discharge, but at intermediate locations where organic carbon concentrations were greatest. Dissolved methane, derived from microbial methanogenesis, was present in some ground waters. Methanogenesis resulted in substantial alteration of the carbon isotopic composition of ground water. The NETPATH geochemical model code was used to model mass-transfers of carbon affecting the 14C estimate of ground-water residence time. Carbon sources in ground water include dispersed particulate organic matter present in the confining unit separating the two aquifers and methane present in some ground water. Carbonate minerals were not observed in the lithologic material of the ground-water system but may be present, because they have been found in the bedrock of stream drainages that contribute sediment to the study area.

Hydrogeochemical processes and impact of tanning industries on groundwater quality in Ambur, Vellore district, Tamil Nadu, India.

PubMed

Kanagaraj, G; Elango, L

2016-12-01

The present study was carried out to determine the hydrogeochemical processes and the impact of tanning industries on groundwater in Ambur, Vellore district, Tamil Nadu, India. Thirty groundwater samples were collected during pre monsoon (July 2015) and post monsoon (January 2016) from the open and shallow wells around this region and were analyzed for major ions and chromium. The major ion concentration follows the order of Na + > Ca 2+ > Mg 2+ > K + (cations) and Cl - > HCO 3 - > SO 4 2- > NO 3 - (anions) for both seasons. The high concentrations of Na + , Cl - , and Cr around the tannery regions indicate the impact of effluent discharged from tannery units. In general, the groundwater of this study area is of Na + -Cl - type, which is due to the mixing of tannery effluent and cation exchange process. Ionic ratio indicates that the silicate weathering influences the groundwater chemistry. The permissible limit of chromium in the groundwater exceeds in over 50 % of the sampling wells. The factor analysis reveals that the dominant source for ionic contents is due to tannery effluents and cation exchange processes. To overcome this situation, it is essential to improve the performance of the effluent treatment plants so as to remove the salinity of wastewater and to plan for rainfall recharge structures for improving the groundwater recharge.

Groundwater quality in the Colorado River basins, California

USGS Publications Warehouse

Dawson, Barbara J. Milby; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Four groundwater basins along the Colorado River make up one of the study areas being evaluated. The Colorado River study area is approximately 884 square miles (2,290 square kilometers) and includes the Needles, Palo Verde Mesa, Palo Verde Valley, and Yuma groundwater basins (California Department of Water Resources, 2003). The Colorado River study area has an arid climate and is part of the Sonoran Desert. Average annual rainfall is about 3 inches (8 centimeters). Land use in the study area is approximately 47 percent (%) natural (mostly shrubland), 47% agricultural, and 6% urban. The primary crops are pasture and hay. The largest urban area is the city of Blythe (2010 population of 21,000). Groundwater in these basins is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay deposited by the Colorado River or derived from surrounding mountains. The primary aquifers in the Colorado River study area are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in the Colorado River basins are completed to depths between 230 and 460 feet (70 to 140 meters), consist of solid casing from the land surface to a depth of 130 of 390 feet (39 to 119 meters), and are screened or perforated below the solid casing. The main source of recharge to the groundwater systems in the Needles, Palo Verde Mesa, and Palo Verde Valley basins is the Colorado River; in the Yuma basin, the main source of recharge is from subsurface flow from the groundwater basins to the west. Groundwater discharge is primarily to pumping wells, evapotranspiration, and, locally, to the Colorado River.

Groundwater ages from the freshwater zone of the Edwards aquifer, Uvalde County, Texas—Insights into groundwater flow and recharge

USGS Publications Warehouse

Hunt, Andrew G.; Landis, Gary P.; Faith, Jason R.

2016-02-23

Tritium–helium-3 groundwater ages of the Edwards aquifer in south-central Texas were determined as part of a long-term study of groundwater flow and recharge in the Edwards and Trinity aquifers. These ages help to define groundwater residence times and to provide constraints for calibration of groundwater flow models. A suite of 17 samples from public and private supply wells within Uvalde County were collected for active and noble gases, and for tritium–helium-3 analyses from the confined and unconfined parts of the Edwards aquifer. Samples were collected from monitoring wells at discrete depths in open boreholes as well as from integrated pumped well-head samples. The data indicate a fairly uniform groundwater flow system within an otherwise structurally complex geologic environment comprised of regionally and locally faulted rock units, igneous intrusions, and karst features within carbonate rocks. Apparent ages show moderate, downward average, linear velocities in the Uvalde area with increasing age to the east along a regional groundwater flow path. Though the apparent age data show a fairly consistent distribution across the study area, many apparent ages indicate mixing of both modern (less than 60 years) and premodern (greater than 60 years) waters. This mixing is most evident along the “bad water” line, an arbitrary delineation of 1,000 milligrams per liter dissolved solids that separates the freshwater zone of the Edwards aquifer from the downdip saline water zone. Mixing of modern and premodern waters also is indicated within the unconfined zone of the aquifer by high excess helium concentrations in young waters. Excess helium anomalies in the unconfined aquifer are consistent with possible subsurface discharge of premodern groundwater from the underlying Trinity aquifer into the younger groundwater of the Edwards aquifer.

Memorandum on ground-water investigation of four proposed stock wells in Puertocito Area, Socorro County and Canoncito Area, Bernalillo and Valencia Counties, New Mexico

USGS Publications Warehouse

Repenning, C.A.; Galloway, S.E.

1952-01-01

At the request of the Navajo Service, Office ot Indian Affairs, a groundwater iinvestigation of four proposed stock wells in the Puertocito Area, Socorro county and the Canoncito Area., Bernalillo and Valencia counties,New Mexico, was made in November, 1951 (see fig. 1). Although these areas are not on the Navajo Indian Reservation, they were included in the program of study of ground-water resources or the Navajo and Hopi Indian Reservations now being conducted by the Ground Water Branch of the United States Geological Survey. The work was financed by and was in cooperation with the Navajo Service, Office of Indian Affairs.

Shallow groundwater in the Matanuska-Susitna Valley, Alaska—Conceptualization and simulation of flow

USGS Publications Warehouse

Kikuchi, Colin P.

2013-01-01

The Matanuska-Susitna Valley is in the Upper Cook Inlet Basin and is currently undergoing rapid population growth outside of municipal water and sewer service areas. In response to concerns about the effects of increasing water use on future groundwater availability, a study was initiated between the Alaska Department of Natural Resources and the U.S. Geological Survey. The goals of the study were (1) to compile existing data and collect new data to support hydrogeologic conceptualization of the study area, and (2) to develop a groundwater flow model to simulate flow dynamics important at the regional scale. The purpose of the groundwater flow model is to provide a scientific framework for analysis of regional-scale groundwater availability. To address the first study goal, subsurface lithologic data were compiled into a database and were used to construct a regional hydrogeologic framework model describing the extent and thickness of hydrogeologic units in the Matanuska-Susitna Valley. The hydrogeologic framework model synthesizes existing maps of surficial geology and conceptual geochronologies developed in the study area with the distribution of lithologies encountered in hundreds of boreholes. The geologic modeling package Geological Surveying and Investigation in Three Dimensions (GSI3D) was used to construct the hydrogeologic framework model. In addition to characterizing the hydrogeologic framework, major groundwater-budget components were quantified using several different techniques. A land-surface model known as the Deep Percolation Model was used to estimate in-place groundwater recharge across the study area. This model incorporates data on topography, soils, vegetation, and climate. Model-simulated surface runoff was consistent with observed streamflow at U.S. Geological Survey streamgages. Groundwater withdrawals were estimated on the basis of records from major water suppliers during 2004-2010. Fluxes between groundwater and surface water were estimated during field investigations on several small streams. Regional groundwater flow patterns were characterized by synthesizing previous water-table maps with a synoptic water-level measurement conducted during 2009. Time-series water-level data were collected at groundwater and lake monitoring stations over the study period (2009–present). Comparison of historical groundwater-level records with time-series groundwater-level data collected during this study showed similar patterns in groundwater-level fluctuation in response to precipitation. Groundwater-age data collected during previous studies show that water moves quickly through the groundwater system, suggesting that the system responds quickly to changes in climate forcing. Similarly, the groundwater system quickly returns to long-term average conditions following variability due to seasonal or interannual changes in precipitation. These analyses indicate that the groundwater system is in a state of dynamic equilibrium, characterized by water-level fluctuation about a constant average state, with no long-term trends in aquifer-system storage. To address the second study goal, a steady-state groundwater flow model was developed to simulate regional groundwater flow patterns. The groundwater flow model was bounded by physically meaningful hydrologic features, and appropriate internal model boundaries were specified on the basis of conceptualization of the groundwater system resulting in a three-layer model. Calibration data included 173 water‑level measurements and 18 measurements of streamflow gains and losses along small streams. Comparison of simulated and observed heads and flows showed that the model accurately simulates important regional characteristics of the groundwater flow system. This model is therefore appropriate for studying regional-scale groundwater availability. Mismatch between model-simulated and observed hydrologic quantities is likely because of the coarse grid size of the model and seasonal transient effects. Next steps towards model refinement include the development of a transient groundwater flow model that is suitable for analysis of seasonal variability in hydraulic heads and flows. In addition, several important groundwater budget components remain poorly quantified—including groundwater outflow to the Matanuska River, Little Susitna River, and Knik Arm.

Hydrogeologic data for the Blaine aquifer and associated units in southwestern Oklahoma and northwestern Texas

USGS Publications Warehouse

Runkle, D.L.; Bergman, D.L.; Fabian, R.S.

1997-01-01

This report is a compilation of hydrogeologic data collected for an areal ground-water investigation of the Blaine aquifer and associated units in southwestern Oklahoma and northwestern Texas. The study area includes parts of Greer, Harmon, and Jackson counties in Oklahoma and parts of Childress, Collingsworth, Hall, Hardeman, and Wilbarger counties in Texas. The Blaine aquifer consists of cavernous gypsum and dolomite beds. Water from the Blaine aquifer supports a local agriculture based mainly on irrigated cotton and wheat. The purpose of the study was to determine the availability, quantity, and quality of ground water from the Blaine aquifer and associated units. This report provides a reference for some of the data that was used as input into a computer ground-water flow model that simulates ground-water flow in the Blaine aquifer. The data in this report consists of: (1) Monthly or periodic water-level measurements in 134 wells; (2) daily mean water-level measurements for 11 wells equipped with water-level recorders; (3) daily total precipitation measurements from five precipitation gages; (4) low-flow stream-discharge measurements for 89 stream sites; (5) miscellaneous stream-discharge measurements at seven stream sites; (6) chemical analyses of surface water from 78 stream sites during low-flow periods; (7) chemical analyses of ground water from 41 wells; and (8) chemical analyses of runoff water collected at five sites.

Arkansas Groundwater-Quality Network

USGS Publications Warehouse

Pugh, Aaron L.; Jackson, Barry T.; Miller, Roger

2014-01-01

Arkansas is the fourth largest user of groundwater in the United States, where groundwater accounts for two-thirds of the total water use. Groundwater use in the State increased by 510 percent between 1965 and 2005 (Holland, 2007). The Arkansas Groundwater-Quality Network is a Web map interface (http://ar.water.usgs.gov/wqx) that provides rapid access to the U.S. Geological Survey’s (USGS) National Water Information System (NWIS) and the U.S. Environmental Protection Agency’s (USEPA) STOrage and RETrieval (STORET) databases of ambient water information. The interface enables users to perform simple graphical analysis and download selected water-quality data.

Ground-Water Quality Data in the Owens and Indian Wells Valleys Study Unit, 2006: Results from the California GAMA Program

USGS Publications Warehouse

Densmore, Jill N.; Fram, Miranda S.; Belitz, Kenneth

2009-01-01

Ground-water quality in the approximately 1,630 square-mile Owens and Indian Wells Valleys study unit (OWENS) was investigated in September-December 2006 as part of the Priority Basin Project of Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Project was developed in response to the Groundwater Quality Monitoring Act of 2001 and is being conducted by the U.S. Geological Survey (USGS) in collaboration with the California State Water Resources Control Board (SWRCB). The Owens and Indian Wells Valleys study was designed to provide a spatially unbiased assessment of raw ground-water quality within OWENS study unit, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 74 wells in Inyo, Kern, Mono, and San Bernardino Counties. Fifty-three of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study area (grid wells), and 21 wells were selected to evaluate changes in water chemistry in areas of interest (understanding wells). The ground-water samples were analyzed for a large number of synthetic organic constituents [volatile organic compounds (VOCs), pesticides and pesticide degradates, pharmaceutical compounds, and potential wastewater- indicator compounds], constituents of special interest [perchlorate, N-nitrosodimethylamine (NDMA), and 1,2,3- trichloropropane (1,2,3-TCP)], naturally occurring inorganic constituents [nutrients, major and minor ions, and trace elements], radioactive constituents, and microbial indicators. Naturally occurring isotopes [tritium, and carbon-14, and stable isotopes of hydrogen and oxygen in water], and dissolved noble gases also were measured to help identify the source and age of the sampled ground water. This study evaluated the quality of raw ground water in the aquifer in the OWENS study unit and did not attempt to evaluate the quality of treated water delivered to consumers. Water supplied to consumers typically is treated after withdrawal from the ground, disinfected, and blended with other waters to maintain acceptable water quality. Regulatory thresholds apply to treated water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with regulatory and non-regulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and California Department of Public Health (CDPH) and non-regulatory thresholds established for aesthetic concerns (secondary maximum contamination levels, SMCL-CA) by CDPH. VOCs and pesticides were detected in samples from less than one-third of the grid wells; all detections were below health-based thresholds, and most were less than one-one hundredth of threshold values. All detections of perchlorate and nutrients in samples from OWENS were below health-based thresholds. Most detections of trace elements in ground-water samples from OWENS wells were below health-based thresholds. In samples from the 53 grid wells, three constituents were detected at concentrations above USEPA maximum contaminant levels: arsenic in 5 samples, uranium in 4 samples, and fluoride in 1 sample. Two constituents were detected at concentrations above CDPH notification levels (boron in 9 samples and vanadium in 1 sample), and two were above USEPA lifetime health advisory levels (molybdenum in 3 samples and strontium in 1 sample). Most of the samples from OWENS wells had concentrations of major elements, TDS, and trace elements below the non-enforceable standards set for aesthetic concerns. Samples from nine grid wells had concentrations of manganese, iron, or TDS above the SMCL-CAs.

Embodied energy comparison of surface water and groundwater supply options.

PubMed

Mo, Weiwei; Zhang, Qiong; Mihelcic, James R; Hokanson, David R

2011-11-01

The embodied energy associated with water provision comprises an important part of water management, and is important when considering sustainability. In this study, an input-output based hybrid analysis integrated with structural path analysis was used to develop an embodied energy model. The model was applied to a groundwater supply system (Kalamazoo, Michigan) and a surface water supply system (Tampa, Florida). The two systems evaluated have comparable total energy embodiments based on unit water production. However, the onsite energy use of the groundwater supply system is approximately 27% greater than the surface water supply system. This was primarily due to more extensive pumping requirements. On the other hand, the groundwater system uses approximately 31% less indirect energy than the surface water system, mainly because of fewer chemicals used for treatment. The results from this and other studies were also compiled to provide a relative comparison of embodied energy for major water supply options. Copyright © 2011 Elsevier Ltd. All rights reserved.

Response of the microbial community to seasonal groundwater level fluctuations in petroleum hydrocarbon-contaminated groundwater.

PubMed

Zhou, Ai-xia; Zhang, Yu-ling; Dong, Tian-zi; Lin, Xue-yu; Su, Xiao-si

2015-07-01

The effects of seasonal groundwater level fluctuations on the contamination characteristics of total petroleum hydrocarbons (TPH) in soils, groundwater, and the microbial community were investigated at a typical petrochemical site in northern China. The measurements of groundwater and soil at different depths showed that significant TPH residue was present in the soil in this study area, especially in the vicinity of the pollution source, where TPH concentrations were up to 2600 mg kg(-1). The TPH concentration in the groundwater fluctuated seasonally, and the maximum variation was 0.8 mg L(-1). The highest TPH concentrations were detected in the silty clay layer and lied in the groundwater level fluctuation zones. The groundwater could reach previously contaminated areas in the soil, leading to higher groundwater TPH concentrations as TPH leaches into the groundwater. The coincident variation of the electron acceptors and TPH concentration with groundwater-table fluctuations affected the microbial communities in groundwater. The microbial community structure was significantly different between the wet and dry seasons. The canonical correspondence analysis (CCA) results showed that in the wet season, TPH, NO3(-), Fe(2+), TMn, S(2-), and HCO3(-) were the major factors correlating the microbial community. A significant increase in abundance of operational taxonomic unit J1 (97% similar to Dechloromonas aromatica sp.) was also observed in wet season conditions, indicating an intense denitrifying activity in the wet season environment. In the dry season, due to weak groundwater level fluctuations and low temperature of groundwater, the microbial activity was weak. But iron and sulfate-reducing were also detected in dry season at this site. As a whole, groundwater-table fluctuations would affect the distribution, transport, and biodegradation of the contaminants. These results may be valuable for the control and remediation of soil and groundwater pollution at this site and in other petrochemical-contaminated areas. Furthermore, they are probably helpful for reducing health risks to the general public from contaminated groundwater.

The Slow Moving Threat of Groundwater Salinization: Mechanisms, Costs, and Adaptation Strategies

NASA Astrophysics Data System (ADS)

Pauloo, R.; Guo, Z.; Fogg, G. E.

2016-12-01

Population growth, the Green Revolution, and climate uncertainties have accelerated overdraft in groundwater basins worldwide, which in some regions is converting these basins into closed hydrologic systems, where the dominant exits for water are evapotranspiration and pumping. Irrigated agricultural basins are particularly at risk to groundwater salinization, as naturally occurring (i.e., sodium, potassium, chloride) and anthropogenic (i.e., nitrate fertilizers) salts leach back into the water table through the root zone, while a large portion of pumped groundwater leaves the system as it is evapotranspired by crops. Decreasing water quality associated with increases in Total Dissolved Solids (TDS) has been documented in aquifers across the United States in the past half century. This study suggests that the increase in TDS in aquifers can be partially explained by closed basin hydrogeology and rock-water interactions leading to groundwater salinization. This study will present: (1) a report on historical water quality in the Tulare basin, (2) a forward simulation of salt balance in Tulare Basin based on the Department of Water Resources numerical model C2VSim, and a simple mixing model, (3) an economic analysis forecasting the cost of desalination under varying degrees of managed groundwater recharge where the basin is gradually filled, avoiding hydraulic closure.

Microbial Community in High Arsenic Shallow Groundwater Aquifers in Hetao Basin of Inner Mongolia, China

PubMed Central

Li, Ping; Wang, Yanhong; Dai, Xinyue; Zhang, Rui; Jiang, Zhou; Jiang, Dawei; Wang, Shang; Jiang, Hongchen; Wang, Yanxin; Dong, Hailiang

2015-01-01

A survey was carried out on the microbial community of 20 groundwater samples (4 low and 16 high arsenic groundwater) and 19 sediments from three boreholes (two high arsenic and one low arsenic boreholes) in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia, using the 454 pyrosequencing approach. A total of 233,704 sequence reads were obtained and classified into 12–267 operational taxonomic units (OTUs). Groundwater and sediment samples were divided into low and high arsenic groups based on measured geochemical parameters and microbial communities, by hierarchical clustering and principal coordinates analysis. Richness and diversity of the microbial communities in high arsenic sediments are higher than those in high arsenic groundwater. Microbial community structure was significantly different either between low and high arsenic samples or between groundwater and sediments. Acinetobacter, Pseudomonas, Psychrobacter and Alishewanella were the top four genera in high arsenic groundwater, while Thiobacillus, Pseudomonas, Hydrogenophaga, Enterobacteriaceae, Sulfuricurvum and Arthrobacter dominated high arsenic sediments. Archaeal sequences in high arsenic groundwater were mostly related to methanogens. Biota-environment matching and co-inertia analyses showed that arsenic, total organic carbon, SO4 2-, SO4 2-/total sulfur ratio, and Fe2+ were important environmental factors shaping the observed microbial communities. The results of this study expand our current understanding of microbial ecology in high arsenic groundwater aquifers and emphasize the potential importance of microbes in arsenic transformation in the Hetao Basin, Inner Mongolia. PMID:25970606

Microbial community in high arsenic shallow groundwater aquifers in Hetao Basin of Inner Mongolia, China.

PubMed

Li, Ping; Wang, Yanhong; Dai, Xinyue; Zhang, Rui; Jiang, Zhou; Jiang, Dawei; Wang, Shang; Jiang, Hongchen; Wang, Yanxin; Dong, Hailiang

2015-01-01

A survey was carried out on the microbial community of 20 groundwater samples (4 low and 16 high arsenic groundwater) and 19 sediments from three boreholes (two high arsenic and one low arsenic boreholes) in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia, using the 454 pyrosequencing approach. A total of 233,704 sequence reads were obtained and classified into 12-267 operational taxonomic units (OTUs). Groundwater and sediment samples were divided into low and high arsenic groups based on measured geochemical parameters and microbial communities, by hierarchical clustering and principal coordinates analysis. Richness and diversity of the microbial communities in high arsenic sediments are higher than those in high arsenic groundwater. Microbial community structure was significantly different either between low and high arsenic samples or between groundwater and sediments. Acinetobacter, Pseudomonas, Psychrobacter and Alishewanella were the top four genera in high arsenic groundwater, while Thiobacillus, Pseudomonas, Hydrogenophaga, Enterobacteriaceae, Sulfuricurvum and Arthrobacter dominated high arsenic sediments. Archaeal sequences in high arsenic groundwater were mostly related to methanogens. Biota-environment matching and co-inertia analyses showed that arsenic, total organic carbon, SO4(2-), SO4(2-)/total sulfur ratio, and Fe(2+) were important environmental factors shaping the observed microbial communities. The results of this study expand our current understanding of microbial ecology in high arsenic groundwater aquifers and emphasize the potential importance of microbes in arsenic transformation in the Hetao Basin, Inner Mongolia.

10 CFR Appendix IV to Part 960 - Types of Information for the Nomination of Sites as Suitable for Characterization

Code of Federal Regulations, 2011 CFR

2011-01-01

... with its geologic setting, in order to estimate the pre-waste-emplacement ground-water flow conditions.... • Preliminary estimates of ground-water travel times along the likely flow paths from the repository to... hydrochemical conditions of the host rock, of the surrounding geohydrologic units, and along likely ground-water...

In-situ remediation system for groundwater and soils

DOEpatents

Corey, J.C.; Kaback, D.S.; Looney, B.B.

1991-01-01

The present invention relates to a system for in-situ remediation of contaminated groundwater and soil. In particular the present invention relates to stabilizing toxic metals in groundwater and soil. The United States Government has rights in this invention pursuant to Contract No. DE-AC09-89SR18035 between the US Department of Energy and Westinghouse Savannah River Company.

Groundwater quality in the Rio Grande aquifer system, southwestern United States

USGS Publications Warehouse

Musgrove, MaryLynn; Bexfield, Laura M.

2017-12-07

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Rio Grande aquifer system constitutes one of the important areas being evaluated.

Groundwater quality in the Cambrian-Ordovician aquifer system, midwestern United States

USGS Publications Warehouse

Stackelberg, Paul E.

2017-12-07

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Cambrian-Ordovician aquifer system constitutes one of the important areas being evaluated.

The Virginia Coastal Plain Hydrogeologic Framework

USGS Publications Warehouse

McFarland, Randolph E.; Scott, Bruce T.

2006-01-01

A refined descriptive hydrogeologic framework of the Coastal Plain of eastern Virginia provides a new perspective on the regional ground-water system by incorporating recent understanding gained by discovery of the Chesapeake Bay impact crater and determination of other geological relations. The seaward-thickening wedge of extensive, eastward-dipping strata of largely unconsolidated sediments is classified into a series of 19 hydrogeologic units, based on interpretations of geophysical logs and allied descriptions and analyses from a regional network of 403 boreholes. Potomac aquifer sediments of Early Cretaceous age form the primary ground-water supply resource. The Potomac aquifer is designated as a single aquifer because the fine-grained interbeds, which are spatially highly variable and inherently discontinuous, are not sufficiently dense across a continuous expanse to act as regional barriers to ground-water flow. Part of the Potomac aquifer in the outer part of the Chesapeake Bay impact crater consists of megablock beds, which are relatively undeformed internally but are bounded by widely separated faults. The Potomac aquifer is entirely truncated across the inner part of the crater. The Potomac confining zone approximates a transition from the Potomac aquifer to overlying hydrogeologic units. New or revised designations of sediments of Late Cretaceous age that are present only south of the James River include the upper Cenomanian confining unit, the Virginia Beach aquifer and confining zone, and the Peedee aquifer and confining zone. The Virginia Beach aquifer is a locally important ground-water supply resource. Sediments of late Paleocene to early Eocene age that compose the Aquia aquifer and overlying Nanjemoy-Marlboro confining unit are truncated along the margin of the Chesapeake Bay impact crater. Sediments of late Eocene age compose three newly designated confining units within the crater, which are from bottom to top, the impact-generated Exmore clast and Exmore matrix confining units, and the Chickahominy confining unit. Piney Point aquifer sediments of early Eocene to middle Miocene age overlie most of the Chesapeake Bay impact crater and beyond, but are a locally significant ground-water supply resource only outside of the crater across the middle reaches of the Northern Neck, Middle, and York-James Peninsulas. Sediments of middle Miocene to late Miocene age that compose the Calvert confining unit and overlying Saint Marys confining unit effectively separate the underlying Piney Point aquifer and deeper aquifers from overlying shallow aquifers. Saint Marys aquifer sediments of late Miocene age separate the Calvert and Saint Marys confining units across two limited areas only. Sediments of the Yorktown-Eastover aquifer of late Miocene to late Pliocene age form the second most heavily used ground-water supply resource. The Yorktown confining zone approximates a transition to the overlying late Pliocene to Holocene sediments of the surficial aquifer, which extends across the entire land surface in the Virginia Coastal Plain and is a moderately used supply. The Yorktown-Eastover aquifer and the eastern part of the surficial aquifer are closely associated across complex and extensive hydraulic connections and jointly compose a shallow, generally semiconfined ground-water system that is hydraulically separated from the deeper system. Vertical faults extend from the basement upward through most of the hydrogeologic units but may be more widespread and ubiquitous than recognized herein, because areas of sparse boreholes do not provide adequate spatial control. Hydraulic conductivity probably is decreased locally by disruption of depositional intergranular structure by fault movement in the generally incompetent sediments. Localized fluid flow in open fractures may be unique in the Chickahominy confining unit. Some hydrogeologic units are partly to wholly truncated where displacements are large rela

Impacts of multiple stresses on water demand and supply across the southeastern United States

Treesearch

Ge Sun; Steven G. McNulty; Jennifer A. Moore Myers; Erika C. Cohen

2008-01-01

Assessment of long-term impacts of projected changes in climate, population, and land use and land cover on regional water resource is critical to the sustainable development of the southeastern United States. The objective of this study was to fully budget annual water availability for water supply (precipitation ) evapotranspiration + groundwater supply + return flow...

Remedial Investigation/Feasibility Study, Operable Unit 5, Elmendorf AFB, Anchorage, Alaska. Volume 1. Text

DTIC Science & Technology

1994-03-04

4.7a Organic Con mnats Detected in Upper Aquifer Groundwater .......... 4-46 4.7b Organic Contaminants Detected in Upper Aquifer Groundwater...OU 5 con ~tamiats and impacts on Ship Creek; "* Deftrmine fth fluenc of uppadient contminant sources on fth OU 5 "* Collect suifficient data to detemin...Post Rood, mnorh of the gdof course pro shop, and flowed into a drainage ditch parallel to Post Road. 0 All six source areas have undergone previous inv

Use of a ground-water flow model with particle tracking to evaluate ground-water vulnerability, Clark County, Washington

USGS Publications Warehouse

Snyder, D.T.; Wilkinson, J.M.; Orzol, L.L.

1996-01-01

A ground-water flow model was used in conjunction with particle tracking to evaluate ground-water vulnerability in Clark County, Washington. Using the particle-tracking program, particles were placed in every cell of the flow model (about 60,000 particles) and tracked backwards in time and space upgradient along flow paths to their recharge points. A new computer program was developed that interfaces the results from a particle-tracking program with a geographic information system (GIS). The GIS was used to display and analyze the particle-tracking results. Ground-water vulnerability was evaluated by selecting parts of the ground-water flow system and combining the results with ancillary information stored in the GIS to determine recharge areas, characteristics of recharge areas, downgradient impact of land use at recharge areas, and age of ground water. Maps of the recharge areas for each hydrogeologic unit illustrate the presence of local, intermediate, or regional ground-water flow systems and emphasize the three-dimensional nature of the ground-water flow system in Clark County. Maps of the recharge points for each hydrogeologic unit were overlaid with maps depicting aquifer sensitivity as determined by DRASTIC (a measure of the pollution potential of ground water, based on the intrinsic characteristics of the near-surface unsaturated and saturated zones) and recharge from on-site waste-disposal systems. A large number of recharge areas were identified, particularly in southern Clark County, that have a high aquifer sensitivity, coincide with areas of recharge from on-site waste-disposal systems, or both. Using the GIS, the characteristics of the recharge areas were related to the downgradient parts of the ground-water system that will eventually receive flow that has recharged through these areas. The aquifer sensitivity, as indicated by DRASTIC, of the recharge areas for downgradient parts of the flow system was mapped for each hydrogeologic unit. A number of public-supply wells in Clark County may be receiving a component of water that recharged in areas that are more conducive to contaminant entry. The aquifer sensitivity maps illustrate a critical deficiency in the DRASTIC methodology: the failure to account for the dynamics of the ground-water flow system. DRASTIC indices calculated for a particular location thus do not necessarily reflect the conditions of the ground-water resources at the recharge areas to that particular location. Each hydrogeologic unit was also mapped to highlight those areas that will eventually receive flow from recharge areas with on-site waste-disposal systems. Most public-supply wells in southern Clark County may eventually receive a component of water that was recharged from on-site waste-disposal systems.Traveltimes from particle tracking were used to estimate the minimum and maximum age of ground water within each model-grid cell. Chlorofluorocarbon (CFC)-age dating of ground water from 51 wells was used to calibrate effective porosity values used for the particle- tracking program by comparison of ground-water ages determined through the use of the CFC-age dating with those calculated by the particle- tracking program. There was a 76 percent agreement in predicting the presence of modern water in the 51 wells as determined using CFCs and calculated by the particle-tracking program. Maps showing the age of ground water were prepared for all the hydrogeologic units. Areas with the youngest ground-water ages are expected to be at greatest risk for contamination from anthropogenic sources. Comparison of these maps with maps of public- supply wells in Clark County indicates that most of these wells may withdraw ground water that is, in part, less than 100 years old, and in many instances less than 10 years old. Results of the analysis showed that a single particle-tracking analysis simulating advective transport can be used to evaluate ground-water vulnerability for any part of a ground-wate

Preliminary hydrogeologic assessment near the boundary of the Antelope Valley and El Mirage Valley groundwater basins, California

USGS Publications Warehouse

Stamos, Christina L.; Christensen, Allen H.; Langenheim, Victoria

2017-07-19

The increasing demands on groundwater for water supply in desert areas in California and the western United States have resulted in the need to better understand groundwater sources, availability, and sustainability. This is true for a 650-square-mile area that encompasses the Antelope Valley, El Mirage Valley, and Upper Mojave River Valley groundwater basins, about 50 miles northeast of Los Angeles, California, in the western part of the Mojave Desert. These basins have been adjudicated to ensure that groundwater rights are allocated according to legal judgments. In an effort to assess if the boundary between the Antelope Valley and El Mirage Valley groundwater basins could be better defined, the U.S. Geological Survey began a cooperative study in 2014 with the Mojave Water Agency to better understand the hydrogeology in the area and investigate potential controls on groundwater flow and availability, including basement topography.Recharge is sporadic and primarily from small ephemeral washes and streams that originate in the San Gabriel Mountains to the south; estimates range from about 400 to 1,940 acre-feet per year. Lateral underflow from adjacent basins has been considered minor in previous studies; underflow from the Antelope Valley to the El Mirage Valley groundwater basin has been estimated to be between 100 and 1,900 acre-feet per year. Groundwater discharge is primarily from pumping, mostly by municipal supply wells. Between October 2013 and September 2014, the municipal pumpage in the Antelope Valley and El Mirage Valley groundwater basins was reported to be about 800 and 2,080 acre-feet, respectively.This study was motivated by the results from a previously completed regional gravity study, which suggested a northeast-trending subsurface basement ridge and saddle approximately 3.5 miles west of the boundary between the Antelope Valley and El Mirage Valley groundwater basins that might influence groundwater flow. To better define potential basement structures that could affect groundwater flow between the groundwater basins in the study area, gravity data were collected using more closely spaced measurements in September 2014. Groundwater-level data was gathered and collected from March 2014 through March 2015 to determine depth to water and direction of groundwater flow. The gravity and groundwater-level data showed that the saturated thickness of the alluvium was about 2,000 feet thick to the east and about 130 feet thick above the northward-trending basement ridge near Llano, California. Although it was uncertain whether the basement ridge affects the groundwater system, a potential barrier to groundwater flow could be created if the water table fell below the altitude of the basement ridge, effectively causing the area to the west of the basement ridge to become hydraulically isolated from the area to the east. In addition, the direction of regional-groundwater flow likely will be influenced by future changes in the number and distribution of pumping wells and the thickness of the saturated alluvium from which water is withdrawn. Three-dimensional animations were created to help visualize the relation between the basins’ basement topography and the groundwater system in the area. Further studies that could help to more accurately define the basins and evaluate the groundwater-flow system include exploratory drilling of multi-depth monitoring wells; collection of depth-dependent water-quality samples; and linking together existing, but separate, groundwater-flow models from the Antelope Valley and El Mirage Valley groundwater basins into a single, calibrated groundwater-flow model.

Review: Regional groundwater flow modeling in heavily irrigated basins of selected states in the western United States

NASA Astrophysics Data System (ADS)

Rossman, Nathan R.; Zlotnik, Vitaly A.

2013-09-01

Water resources in agriculture-dominated basins of the arid western United States are stressed due to long-term impacts from pumping. A review of 88 regional groundwater-flow modeling applications from seven intensively irrigated western states (Arizona, California, Colorado, Idaho, Kansas, Nebraska and Texas) was conducted to provide hydrogeologists, modelers, water managers, and decision makers insight about past modeling studies that will aid future model development. Groundwater models were classified into three types: resource evaluation models (39 %), which quantify water budgets and act as preliminary models intended to be updated later, or constitute re-calibrations of older models; management/planning models (55 %), used to explore and identify management plans based on the response of the groundwater system to water-development or climate scenarios, sometimes under water-use constraints; and water rights models (7 %), used to make water administration decisions based on model output and to quantify water shortages incurred by water users or climate changes. Results for 27 model characteristics are summarized by state and model type, and important comparisons and contrasts are highlighted. Consideration of modeling uncertainty and the management focus toward sustainability, adaptive management and resilience are discussed, and future modeling recommendations, in light of the reviewed models and other published works, are presented.

Using geochemistry to identify the source of groundwater to Montezuma Well, a natural spring in Central Arizona, USA: Part 2

USGS Publications Warehouse

Johnson, Raymond H.; DeWitt, Ed; Wirt, Laurie; Manning, Andrew H.; Hunt, Andrew G.

2012-01-01

Montezuma Well is a unique natural spring located in a sinkhole surrounded by travertine. Montezuma Well is managed by the National Park Service, and groundwater development in the area is a potential threat to the water source for Montezuma Well. This research was undertaken to better understand the sources of groundwater to Montezuma Well. Strontium isotopes (87Sr/86Sr) indicate that groundwater in the recharge area has flowed through surficial basalts with subsequent contact with the underlying Permian aged sandstones and the deeper, karstic, Mississippian Redwall Limestone. The distinctive geochemistry in Montezuma Well and nearby Soda Springs (higher concentrations of alkalinity, As, B, Cl, and Li) is coincident with added carbon dioxide and mantle-sourced He. The geochemistry and isotopic data from Montezuma Well and Soda Springs allow for the separation of groundwater samples into four categories: (1) upgradient, (2) deep groundwater with carbon dioxide, (3) shallow Verde Formation, and (4) mixing zone. δ18O and δD values, along with noble gas recharge elevation data, indicate that the higher elevation areas to the north and east of Montezuma Well are the groundwater recharge zones for Montezuma Well and most of the groundwater in this portion of the Verde Valley. Adjusted groundwater age dating using likely 14C and δ13C sources indicate an age for Montezuma Well and Soda Springs groundwaters at 5,400–13,300 years, while shallow groundwater in the Verde Formation appears to be older (18,900). Based on water chemistry and isotopic evidence, groundwater flow to Montezuma Well is consistent with a hydrogeologic framework that indicates groundwater flow by (1) recharge in higher elevation basalts to the north and east of Montezuma Well, (2) movement through the upgradient Permian and Mississippian units, especially the Redwall Limestone, and (3) contact with a basalt dike/fracture system that provides a mechanism for groundwater to flow to the surface. While the exact nature of the groundwater flow connections is still uncertain, the available data indicate that flow to Montezuma Well may be more susceptible to future groundwater development in the Redwall Limestone than from any other geologic unit. Overall, the shallow groundwater in the surrounding Verde Formation appears to be largely disconnected from deeper groundwater flowing to Montezuma Well.

Geochemical, isotopic, and dissolved gas characteristics of groundwater in a fractured crystalline-rock aquifer, Savage Municipal Well Superfund site, Milford, New Hampshire, 2011

USGS Publications Warehouse

Harte, Philip T.

2013-01-01

Tetrachloroethylene (PCE), a volatile organic compound, was detected in groundwater from deep (more than (>) 300 feet (ft) below land surface) fractures in monitoring wells tapping a crystalline-rock aquifer beneath operable unit 1 (OU1) of the Savage Municipal Well Superfund site (Weston, Inc., 2010). Operable units define remedial areas of contaminant concern. PCE contamination within the fractured-rock aquifer has been designated as a separate operable unit, operable unit 3 (OU3; Weston, Inc., 2010). PCE contamination was previously detected in the overlying glacial sand and gravel deposits and basal till, hereafter termed the Milford-Souhegan glacial-drift (MSGD) aquifer (Harte, 2004, 2006). Operable units 1 and 2 encompass areas within the MSGD aquifer, whereas the extent of the underlying OU3 has yet to be defined. The primary original source of contamination has been identified as a former manufacturing facility—the OK Tool manufacturing facility; hence OU1 sometimes has been referred to as the OK Tool Source Area (New Hampshire Department of Environmental Services, undated). A residential neighborhood of 30 to 40 houses is located in close proximity (one-quarter of a mile) from the PCE-contaminated monitoring wells. Each house has its own water-supply well installed in similar rocks as those of the monitoring wells, as indicated by the New Hampshire State geologic map (Lyons and others, 1997). An investigation was initiated in 2010 by the U.S. Environmental Protection Agency (USEPA) region 1, and the New Hampshire Department of Environmental Services (NHDES) to assess the potential for PCE transport from known contaminant locations (monitoring wells) to the residential wells. The U.S. Geological Survey (USGS) and the NHDES entered into a cooperative agreement in 2011 to assist in the evaluation of PCE transport in the fractured-rock aquifer. Periodic sampling over the last decade by the USEPA and NHDES has yet to detect PCE in groundwater from the residential-supply wells (as of 2012). However, part of assessing the potential for PCE transport involves understanding the origin of the groundwater in the monitoring and residential wells. One of the tools in delineating the movement of groundwater to wells, particularly in complex, highly heterogeneous fractured-rock aquifers, is the understanding of the geochemical and isotopic composition of groundwater (Lipfert and Reeve, 2004; Harte and others, 2012). This report summarizes findings from analyses of geochemical, isotopic, and dissolved gas characteristics of groundwater. Samples of groundwater were collected in 2011 from monitoring wells and nearby residential-supply wells in proximity to OU1.

Evaluation of ground-water flow and hydrologic budget for Lake Five-O, a seepage lake in northwestern Florida

USGS Publications Warehouse

Grubbs, J.W.

1995-01-01

Temporal and spatial distributions of ground-water inflow to, and leakage from Lake Five-O, a softwater, seepage lake in northwestern Florida, were evaluated using hydrologic data and simulation models of the shallow ground-water system adjacent to the lake. The simulation models indicate that ground-water inflow to the lake and leakage from the lake to the ground-water system are the dominant components in the total inflow (precipitation plus ground-water inflow) and total outflow (evaporation plus leakage) budgets of Lake Five-O. Simlulated ground-water inflow and leakage were approximately 4 and 5 times larger than precipitation inputs and evaporative losses, respectively, during calendar years 1989-90. Exchanges of water between Lake Five-O and the ground-water system were consistently larger than atmospheric-lake exchanges. A consistent pattern of shallow ground-water inflow and deep leakage was also evident throughout the study period. The mean time of travel from ground-water that discharges at Lake Five-O (time from recharge at the water table to discharge at the lake) was estimated to be within a range of 3 to 6 years. Flow-path evaluations indicated that the intermediate confining unit probably has a negligible influence on the geochemistry of ground-water inflow to Lake Five-O. The hydrologic budgets and flow-path evaluations provide critical information for developing geochemical budgets for Lake Five-O and for improving the understanding of the relative importance of various processes that regulate the acid-neutralizing capacity of softwater seepage lakes in Florida.

Hydraulic characterization of volcanic rocks in Pahute Mesa using an integrated analysis of 16 multiple-well aquifer tests, Nevada National Security Site, 2009–14

USGS Publications Warehouse

Garcia, C. Amanda; Jackson, Tracie R.; Halford, Keith J.; Sweetkind, Donald S.; Damar, Nancy A.; Fenelon, Joseph M.; Reiner, Steven R.

2017-01-20

An improved understanding of groundwater flow and radionuclide migration downgradient from underground nuclear-testing areas at Pahute Mesa, Nevada National Security Site, requires accurate subsurface hydraulic characterization. To improve conceptual models of flow and transport in the complex hydrogeologic system beneath Pahute Mesa, the U.S. Geological Survey characterized bulk hydraulic properties of volcanic rocks using an integrated analysis of 16 multiple-well aquifer tests. Single-well aquifer-test analyses provided transmissivity estimates at pumped wells. Transmissivity estimates ranged from less than 1 to about 100,000 square feet per day in Pahute Mesa and the vicinity. Drawdown from multiple-well aquifer testing was estimated and distinguished from natural fluctuations in more than 200 pumping and observation wells using analytical water-level models. Drawdown was detected at distances greater than 3 miles from pumping wells and propagated across hydrostratigraphic units and major structures, indicating that neither faults nor structural blocks noticeably impede or divert groundwater flow in the study area.Consistent hydraulic properties were estimated by simultaneously interpreting drawdown from the 16 multiple-well aquifer tests with an integrated groundwater-flow model composed of 11 well-site models—1 for each aquifer test site. Hydraulic properties were distributed across volcanic rocks with the Phase II Pahute Mesa-Oasis Valley Hydrostratigraphic Framework Model. Estimated hydraulic-conductivity distributions spanned more than two orders of magnitude in hydrostratigraphic units. Overlapping hydraulic conductivity ranges among units indicated that most Phase II Hydrostratigraphic Framework Model units were not hydraulically distinct. Simulated total transmissivity ranged from 1,600 to 68,000 square feet per day for all pumping wells analyzed. High-transmissivity zones exceeding 10,000 square feet per day exist near caldera margins and extend along the northern and eastern Pahute Mesa study area and near the southwestern edge of the study area. The estimated hydraulic-property distributions and observed hydraulic connections among geologic structures improved the characterization and representation of groundwater flow at Pahute Mesa.

Ground-water levels in intermontane basins of the northern Rocky Mountains, Montana and Idaho

USGS Publications Warehouse

Briar, David W.; Lawlor, S.M.; Stone, M.A.; Parliman, D.J.; Schaefer, J.L.; Kendy, Eloise

1996-01-01

The Regional Aquifer-System Analysis (RASA) program is a series of studies by the U.S. Geological Survey (USGS) to analyze regional ground-water systems that compose a major portion of the Nation's water supply (Sun, 1986). The Northern Rocky Mountains Intermontane Basins is one of the study regions in this national program. The main objectives of the RASA studies are to (1) describe the groundwater systems as they exist today, (2) analyze the known changes that have led to the systems present condition, (3) combine results of previous studies in a regional analysis, where possible, and (4) provide means by which effects of future ground-water development can be estimated.The purpose of this study, which began in 1990, was to increase understanding of the hydrogeology of the intermontane basins of the Northern Rocky Mountains area. This report is Chapter B of a three-part series and shows the general distribution of ground-water levels in basin-fill deposits in the study area. Chapter A (Tuck and others, 1996) describes the geologic history and generalized hydrogeologic units. Chapter C (Clark and Dutton, 1996) describes the quality of ground and surface waters in the study area.Ground-water levels shown in this report were measured primarily during summer 1991 and summer 1992; however, historical water levels were used for areas where more recent data could not be obtained. The information provided allows for the evaluation of general directions of ground-water flow, identification of recharge and discharge areas, and determination of hydraulic gradients within basin-fill deposits.

Groundwater sapping processes, Western Desert, Egypt.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, W.; Arvidson, R.E.; Sultan, M.

1997-01-01

Depressions of the Western Desert of Egypt (specifically, Kharga, Farafra, and Kurkur regions) are mainly occupied by shales that are impermeable, but easily erodible by rainfall and runoff, whereas the surrounding plateaus are composed of limestones that are permeable and more resistant to fluvial erosion under semiarid to arid conditions. Scallop-shaped escarpment edges and stubby-looking channels that cut into the plateau units are suggestive of slumping of limestones by ground-water sapping at the limestone-shale interfaces, removal of slump blocks by weathering and fluvial erosion, and consequent scarp retreat. Spring-derived tufa deposits found near the limestone escarpments provide additional evidence formore » possible ground-water sapping during previous wet periods. A computer simulation model was developed to quantify the ground-water sapping processes, using a cellular automata algorithm with coupled surface runoff and ground-water flow for a permeable, resistant layer over an impermeable, friable unit. Erosion, deposition, slumping, and generation of spring-derived tufas were parametrically modeled. Simulations using geologically reasonable parameters demonstrate that relatively rapid erosion of the shales by surface runoff, ground-water sapping, and slumping of the limestones, and detailed control by hydraulic conductivity inhomogeneities associated with structures explain the depressions, escarpments, and associated landforms and deposits. Using episodic wet pulses, keyed by {delta}{sup 18}O deep-sea core record, the model produced tufa ages that are statistically consistent with the observed U/Th tufa ages. This result supports the hypothesis that northeastern African wet periods occurred during interglacial maxima. The {delta}{sup 18}O-forced model also replicates the decrease in fluvial and sapping activity over the past million years, as northeastern Africa became hyperarid. The model thus provides a promising predictive tool for studying long-term landform evolution that involves surface and subsurface processes and climatic change.« less

Transient calibration of a groundwater-flow model of Chimacum Creek Basin and vicinity, Jefferson County, Washington: a supplement to Scientific Investigations Report 2013-5160

USGS Publications Warehouse

Jones, Joseph L.; Johnson, Kenneth H.

2013-01-01

A steady-state groundwater-flow model described in Scientific Investigations Report 2013-5160, ”Numerical Simulation of the Groundwater-Flow System in Chimacum Creek Basin and Vicinity, Jefferson County, Washington” was developed to evaluate potential future impacts of growth and of water-management strategies on water resources in the Chimacum Creek Basin. This supplement to that report describes the unsuccessful attempt to perform a calibration to transient conditions on the model. The modeled area is about 64 square miles on the Olympic Peninsula in northeastern Jefferson County, Washington. The geologic setting for the model area is that of unconsolidated deposits of glacial and interglacial origin typical of the Puget Sound Lowlands. The hydrogeologic units representing aquifers are Upper Aquifer (UA, roughly corresponding to recessional outwash) and Lower Aquifer (LA, roughly corresponding to advance outwash). Recharge from precipitation is the dominant source of water to the aquifer system; discharge is primarily to marine waters below sea level and to Chimacum Creek and its tributaries. The model is comprised of a grid of 245 columns and 313 rows; cells are a uniform 200 feet per side. There are six model layers, each representing one hydrogeologic unit: (1) Upper Confining unit (UC); (2) Upper Aquifer unit (UA); (3) Middle Confining unit (MC); (4) Lower Aquifer unit (LA); (5) Lower Confining unit (LC); and (6) Bedrock unit (OE). The transient simulation period (October 1994–September 2009) was divided into 180 monthly stress periods to represent temporal variations in recharge, discharge, and storage. An attempt to calibrate the model to transient conditions was unsuccessful due to instabilities stemming from oscillations in groundwater discharge to and recharge from streamflow in Chimacum Creek. The model as calibrated to transient conditions has mean residuals and standard errors of 0.06 ft ±0.45 feet for groundwater levels and 0.48 ± 0.06 cubic feet per second for flows. Although the expected seasonal trends were observed in model results, the typical observed annual variation of groundwater levels of about 2 feet was not. Streamflow at the most downstream observation point was about three times larger than simulated streamflow. Because the transient version of the model proved inherently unstable, it was not used to simulate forecast conditions for alternate hydrologic or anthropogenic changes. Adaptation of alternate stream simulation packages, such as RIV, or newer versions of MODFLOW, such as MODFLOW-NWT, could possibly assist with achieving calibration to transient conditions.

Virtual groundwater transfers from overexploited aquifers in the United States

PubMed Central

Marston, Landon; Konar, Megan; Cai, Ximing; Troy, Tara J.

2015-01-01

The High Plains, Mississippi Embayment, and Central Valley aquifer systems within the United States are currently being overexploited for irrigation water supplies. The unsustainable use of groundwater resources in all three aquifer systems intensified from 2000 to 2008, making it imperative that we understand the consumptive processes and forces of demand that are driving their depletion. To this end, we quantify and track agricultural virtual groundwater transfers from these overexploited aquifer systems to their final destination. Specifically, we determine which US metropolitan areas, US states, and international export destinations are currently the largest consumers of these critical aquifers. We draw upon US government data on agricultural production, irrigation, and domestic food flows, as well as modeled estimates of agricultural virtual water contents to quantify domestic transfers. Additionally, we use US port-level trade data to trace international exports from these aquifers. In 2007, virtual groundwater transfers from the High Plains, Mississippi Embayment, and Central Valley aquifer systems totaled 17.93 km3, 9.18 km3, and 6.81 km3, respectively, which is comparable to the capacity of Lake Mead (35.7 km3), the largest surface reservoir in the United States. The vast majority (91%) of virtual groundwater transfers remains within the United States. Importantly, the cereals produced by these overexploited aquifers are critical to US food security (contributing 18.5% to domestic cereal supply). Notably, Japan relies upon cereals produced by these overexploited aquifers for 9.2% of its domestic cereal supply. These results highlight the need to understand the teleconnections between distant food demands and local agricultural water use. PMID:26124137

Use of induced polarization to characterize the hydrogeologic framework of the zone of surface‐water/groundwater exchange at the Hanford 300 Area, WA

USGS Publications Warehouse

Slater, Lee; Ntarlagiannis, Dimitrios; Day-Lewis, Frederick D.; Mwakanyamale, Kisa; Lane, John W.; Ward, Andy; Versteeg, Roelof J.

2010-01-01

An extensive continuous waterborne electrical imaging (CWEI) survey was conducted along the Columbia River corridor adjacent to the U.S. Department of Energy (DOE) Hanford 300 Area, WA, in order to improve the conceptual model for exchange between surface water and U‐contaminated groundwater. The primary objective was to determine spatial variability in the depth to the Hanford‐Ringold (H‐R) contact, an important lithologic boundary that limits vertical transport of groundwater along the river corridor. Resistivity and induced polarization (IP) measurements were performed along six survey lines parallel to the shore (each greater than 2.5 km in length), with a measurement recorded every 0.5–3.0 m depending on survey speed, resulting in approximately 65,000 measurements. The H‐R contact was clearly resolved in images of the normalized chargeability along the river corridor due to the large contrast in surface area (hence polarizability) of the granular material between the two lithologic units. Cross sections of the lithologic structure along the river corridor reveal a large variation in the thickness of the overlying Hanford unit (the aquifer through which contaminated groundwater discharges to the river) and clearly identify locations along the river corridor where the underlying Ringold unit is exposed to the riverbed. Knowing the distribution of the Hanford and Ringold units along the river corridor substantially improves the conceptual model for the hydrogeologic framework regulating U exchange between groundwater and Columbia River water relative to current models based on projections of data from boreholes on land into the river.

Virtual groundwater transfers from overexploited aquifers in the United States.

PubMed

Marston, Landon; Konar, Megan; Cai, Ximing; Troy, Tara J

2015-07-14

The High Plains, Mississippi Embayment, and Central Valley aquifer systems within the United States are currently being overexploited for irrigation water supplies. The unsustainable use of groundwater resources in all three aquifer systems intensified from 2000 to 2008, making it imperative that we understand the consumptive processes and forces of demand that are driving their depletion. To this end, we quantify and track agricultural virtual groundwater transfers from these overexploited aquifer systems to their final destination. Specifically, we determine which US metropolitan areas, US states, and international export destinations are currently the largest consumers of these critical aquifers. We draw upon US government data on agricultural production, irrigation, and domestic food flows, as well as modeled estimates of agricultural virtual water contents to quantify domestic transfers. Additionally, we use US port-level trade data to trace international exports from these aquifers. In 2007, virtual groundwater transfers from the High Plains, Mississippi Embayment, and Central Valley aquifer systems totaled 17.93 km(3), 9.18 km(3), and 6.81 km(3), respectively, which is comparable to the capacity of Lake Mead (35.7 km(3)), the largest surface reservoir in the United States. The vast majority (91%) of virtual groundwater transfers remains within the United States. Importantly, the cereals produced by these overexploited aquifers are critical to US food security (contributing 18.5% to domestic cereal supply). Notably, Japan relies upon cereals produced by these overexploited aquifers for 9.2% of its domestic cereal supply. These results highlight the need to understand the teleconnections between distant food demands and local agricultural water use.

Ground-water areas and well logs, central Sevier Valley, Utah

USGS Publications Warehouse

Young, Richard A.

1960-01-01

Between September 1959 and June 1960 the United States Geological Survey and the Utah State Engineer, with financial assistance from Garfield, Millard, Piute, Sanpete, and Sevier Counties and from local water-users’ associations, cooperated in an investigation to determine the structural framework of the central Sevier Valley and to evaluate the valley’s ground-water potential. An important aspect of the study was the drilling of 22 test holes under private contract. These data and other data collected during the course of the larger ground-water investigation of which the test drilling was a part will be evaluated in a report on the geology and ground-water resources of the central Sevier Valley. The present report has been prepared to make available the logs of test holes and to describe in general terms the availability of ground water in the different areas of the valley.

Effect of interannual and interdecadal climate oscillations on groundwater in North Carolina

NASA Astrophysics Data System (ADS)

Anderson, William P.; Emanuel, Ryan E.

2008-12-01

Multi-year climate oscillations such as the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) affect precipitation and stream discharge rates in the western hemisphere. While inferences may be drawn between these hydroclimatological relationships and groundwater conditions, few studies explicitly link groundwater conditions to these cycles. Here we investigate relationships between winter ENSO, PDO, and lagging baseflow rates in the southeastern United States. We find strong correlation between winter ENSO and lagged baseflow in coastal North Carolina which, coupled with anomalies in mean baseflow, decrease with distance inland from the coast. Our results demonstrate that interannual and interdecadal climate oscillations in the Pacific Ocean have a strong effect on hydrological processes in eastern North America despite filtering by the groundwater flow process. These results have implications for water resource availability in regions where water management is complicated by population growth and climatic uncertainty.

Quantifying Groundwater Fluctuations in the Southern High Plains with GIS and Geostatistics

NASA Astrophysics Data System (ADS)

Whitehead, B.

2008-12-01

Groundwater as a dwindling non-renewable natural resource has been an important research theme in agricultural studies coupled with human-environment interaction. This research incorporated contemporary Geographic Information System (GIS) methodologies and a universal kriging interpolator (geostatistics) to develop depth to groundwater surfaces for the southern portion of the High Plains, or Ogallala, aquifer. The variations in the interpolated surfaces were used to calculate the volume of water mined from the aquifer from 1980 to 2005. The findings suggest a nearly inverse relationship to the water withdrawal scenarios derived by the United States Geological Survey (USGS) during the Regional Aquifer System Analysis (RASA) performed in the early 1980's. These results advocate further research into regional climate change, groundwater-surface water interaction, and recharge mechanisms in the region, and provide a substantial contribution to the continuing and contentious issue concerning the environmental sustainability of the High Plains.

The High Plains Aquifer, USA: Groundwater development and sustainability

USGS Publications Warehouse

Dennehy, K.F.; Litke, D.W.; McMahon, P.B.

2002-01-01

The High Plains Aquifer, located in the United States, is one of the largest freshwater aquifers in the world and is threatened by continued decline in water levels and deteriorating water quality. Understanding the physical and cultural features of this area is essential to assessing the factors that affect this groundwater resource. About 27% of the irrigated land in the United States overlies this aquifer, which yields about 30% of the nation's groundwater used for irrigation of crops including wheat, corn, sorghum, cotton and alfalfa. In addition, the aquifer provides drinking water to 82% of the 2.3 million people who live within the aquifer boundary. The High Plains Aquifer has been significantly impacted by human activities. Groundwater withdrawals from the aquifer exceed recharge in many areas, resulting in substantial declines in groundwater level. Residents once believed that the aquifer was an unlimited resource of high-quality water, but they now face the prospect that much of the water may be gone in the near future. Also, agricultural chemicals are affecting the groundwater quality. Increasing concentrations of nitrate and salinity can first impair the use of the water for public supply and then affect its suitability for irrigation. A variety of technical and institutional measures are currently being planned and implemented across the aquifer area in an attempt to sustain this groundwater resource for future generations. However, because groundwater withdrawals remain high and water quality impairments are becoming more commonplace, the sustainability of the High Plains Aquifer is uncertain.

Geohydrology of the Aucilla-Suwannee-Ochlockonee River Basin, south-central Georgia and adjacent parts of Florida

USGS Publications Warehouse

Torak, Lynn J.; Painter, Jaime A.; Peck, Michael F.

2010-01-01

Major streams and tributaries located in the Aucilla-Suwannee-Ochlockonee (ASO) River Basin of south-central Georgia and adjacent parts of Florida drain about 8,000 square miles of a layered sequence of clastic and carbonate sediments and carbonate Coastal Plain sediments consisting of the surficial aquifer system, upper semiconfining unit, Upper Floridan aquifer, and lower confining unit. Streams either flow directly on late-middle Eocene to Oligocene karst limestone or carve a dendritic drainage pattern into overlying Miocene to Holocene sand, silt, and clay, facilitating water exchange and hydraulic connection with geohydrologic units. Geologic structures operating in the ASO River Basin through time control sedimentation and influence geohydrology and water exchange between geohydrologic units and surface water. More than 300 feet (ft) of clastic sediments overlie the Upper Floridan aquifer in the Gulf Trough-Apalachicola Embayment, a broad area extending from the southwest to the northeast through the center of the basin. These clastic sediments limit hydraulic connection and water exchange between the Upper Floridan aquifer, the surficial aquifer system, and surface water. Accumulation of more than 350 ft of low-permeability sediments in the Southeast Georgia Embayment and Suwannee Strait hydraulically isolates the Upper Floridan aquifer from land-surface hydrologic processes in the Okefenokee Basin physiographic district. Burial of limestone beneath thick clastic overburden in these areas virtually eliminates karst processes, resulting in low aquifer hydraulic conductivity and storage coefficient despite an aquifer thickness of more than 900 ft. Conversely, uplift and faulting associated with regional tectonics and the northern extension of the Peninsular Arch caused thinning and erosion of clastic sediments overlying the Upper Floridan aquifer southeast of the Gulf Trough-Apalachicola Embayment near the Florida-Georgia State line. Limestone dissolution in Brooks and Lowndes Counties, Ga., create karst features that enhance water-transmitting and storage properties of the Upper Floridan aquifer, promoting groundwater recharge and water exchange between the aquifer, land surface, and surface water. Structural control of groundwater flow and hydraulic properties combine with climatic effects and increased hydrologic stress from agricultural pumpage to yield unprecedented groundwater-level decline in the northwestern and central parts of the ASO River Basin. Hydrographs from continuous-record observation wells in these regions document declining groundwater levels, indicating diminished water-resource potential of the Upper Floridan aquifer through time. More than 24 ft of groundwater-level decline occurred along the basin's northwestern boundary with the lower Apalachicola-Chattahoochee-Flint River Basin, lowering hydraulic gradients that provide the potential for groundwater flow into the ASO River Basin and southeastward across the Gulf Trough-Apalachicola Embayment region. Slow-moving groundwater across the trough-embayment region coupled with downward-vertical flow from upper to lower limestone units composing the Upper Floridan aquifer resulted in 40-50 ft of groundwater-level decline since 1969 in southeastern Colquitt County. Multi-year episodes of dry climatic conditions during the 1980s through the early 2000s contributed to seasonal and long-term groundwater-level decline by reducing recharge to the Upper Floridan aquifer and increasing hydrologic stress by agricultural pumpage. Unprecedented and continued groundwater-level decline since 1969 caused 40-50 ft of aquifer dewatering in southeastern Colquitt County that reduced aquifer transmissivity and the ability to supply groundwater to wells, resulting in depletion of the groundwater resource.

Hydrogeologic framework of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada

USGS Publications Warehouse

Thamke, Joanna N.; LeCain, Gary D.; Ryter, Derek W.; Sando, Roy; Long, Andrew J.

2014-01-01

Regionally, water in the lower Tertiary and Upper Cretaceous aquifer systems flows in a northerly or northeasterly direction from the Powder River structural basin to the Williston structural basin. Groundwater flow in the Williston structural basin generally is easterly or northeasterly. Flow in the uppermost hydrogeologic units generally is more local and controlled by topography where unglaciated in the Williston structural basin than is flow in the glaciated part and in underlying aquifers. Groundwater flow in the Powder River structural basin generally is northerly with local variations greatest in the uppermost aquifers. Groundwater is confined, and flow is regional in the underlying aquifers.

Vulnerability Assessment of Groundwater Resources by Nutrient Source Apportionment to Individual Groundwater Wells: A Case Study in North Carolina

NASA Astrophysics Data System (ADS)

Ayub, R.; Obenour, D. R.; Keyworth, A. J.; Genereux, D. P.; Mahinthakumar, K.

2016-12-01

Groundwater contamination by nutrients (nitrogen and phosphorus) is a major concern in water table aquifers that underlie agricultural areas in the mid-Atlantic Coastal Plain of the United States. High nutrient concentrations leaching into shallow groundwater can lead to human health problems and eutrophication of receiving surface waters. Liquid manure from concentrated animal feeding operations (CAFOs) stored in open-air lagoons and applied to spray fields can be a significant source of nutrients to groundwater, along with septic waste. In this study, we developed a model-based methodology for source apportionment and vulnerability assessment using sparse groundwater quality sampling measurements for Duplin County, North Carolina (NC), obtained by the NC Department of Environmental Quality (NC DEQ). This model provides information relevant to management by estimating the nutrient transport through the aquifer from different sources and addressing the uncertainty of nutrient contaminant propagation. First, the zones of influence (dependent on nutrient pathways) for individual groundwater monitoring wells were identified using a two-dimensional vertically averaged groundwater flow and transport model incorporating geologic uncertainty for the surficial aquifer system. A multiple linear regression approach is then applied to estimate the contribution weights for different nutrient source types using the nutrient measurements from monitoring wells and the potential sources within each zone of influence. Using the source contribution weights and their uncertainty, a probabilistic vulnerability assessment of the study area due to nutrient contamination is performed. Knowledge of the contribution of different nutrient sources to contamination at receptor locations (e.g., private wells, municipal wells, stream beds etc.) will be helpful in planning and implementation of appropriate mitigation measures.

Influence of permafrost distribution on groundwater flow in the context of climate-driven permafrost thaw: example from Yukon Flats Basin, Alaska, United States

USGS Publications Warehouse

Walvoord, Michelle Ann; Voss, Clifford I.; Wellman, Tristan P.

2012-01-01

Understanding the role of permafrost in controlling groundwater flow paths and fluxes is central in studies aimed at assessing potential climate change impacts on vegetation, species habitat, biogeochemical cycling, and biodiversity. Recent field studies in interior Alaska show evidence of hydrologic changes hypothesized to result from permafrost degradation. This study assesses the hydrologic control exerted by permafrost, elucidates modes of regional groundwater flow for various spatial permafrost patterns, and evaluates potential hydrologic consequences of permafrost degradation. The Yukon Flats Basin (YFB), a large (118,340 km2) subbasin within the Yukon River Basin, provides the basis for this investigation. Model simulations that represent an assumed permafrost thaw sequence reveal the following trends with decreasing permafrost coverage: (1) increased groundwater discharge to rivers, consistent with historical trends in base flow observations in the Yukon River Basin, (2) potential for increased overall groundwater flux, (3) increased spatial extent of groundwater discharge in lowlands, and (4) decreased proportion of suprapermafrost (shallow) groundwater contribution to total base flow. These trends directly affect the chemical composition and residence time of riverine exports, the state of groundwater-influenced lakes and wetlands, seasonal river-ice thickness, and stream temperatures. Presently, the YFB is coarsely mapped as spanning the continuous-discontinuous permafrost transition that model analysis shows to be a critical threshold; thus, the YFB may be on the verge of major hydrologic change should the current permafrost extent decrease. This possibility underscores the need for improved characterization of permafrost and other hydrogeologic information in the region via geophysical techniques, remote sensing, and ground-based observations.

Contaminant Attenuation and Transport Characterization of 200-DV-1 Operable Unit Sediment Samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Truex, Michael J.; Szecsody, James E.; Qafoku, Nikolla

2017-05-15

A laboratory study was conducted to quantify contaminant attenuation processes and associated contaminant transport parameters that are needed to evaluate transport of contaminants through the vadose zone to the groundwater. The laboratory study information, in conjunction with transport analyses, can be used as input to evaluate the feasibility of Monitored Natural Attenuation and other remedies for the 200-DV-1 Operable Unit at the Hanford Site.

Inter-aquifer Dynamics in and Near a Confining Unit Window in Shelby County, Tennessee, USA

NASA Astrophysics Data System (ADS)

Gentry, R. W.; McKay, L. D.; Larsen, D.; Carmichael, J. K.; Solomon, D. K.; Thonnard, N.; Anderson, J. L.

2003-12-01

An interdisplinary research team is investigating the interaction between the surficial alluvial aquifer and the deeper confined Memphis aquifer in the Memphis area, Shelby County, Tennessee. Previous research has identified a window in the clay-rich, upper Claiborne confining unit that separates the two aquifers near a closed municipal landfill in east-central Shelby County, an area undergoing rapid urbanization. For this investigation, a combination of environmental tracers (tritium/helium-3), major and trace ion geochemistry, hydraulic response testing, measurement of hydraulic gradients, and groundwater flow modeling is being used to quantify recharge of young water from the alluvial aquifer through the window to the Memphis aquifer. The research will provide results to better understand how windows were formed and how they influence recharge and water quality in otherwise confined parts of the Memphis aquifer downdip of its outcrop/subcrop area. Examination of continuous core samples and geophysical logs from wells installed for the study using Rotasonic drilling methods confirmed the existence of a sand-dominated window that may be as much as 1 km in diameter in the upper Claiborne confining unit. The upper Claiborne confining unit is 15 to 20 m thick in most of the study area and is overlain by a 10 to 12 m thick alluvial aquifer. The window is interpreted to have formed as a result of depositional and incisional processes in an Eocene-age deltaic system. Hydraulic gradients of several feet exist vertically between the alluvial and Memphis aquifers within the window, indicating downward flow. Groundwater age-dates from tritium/helium-3 analyses indicate that groundwater in the window at the depth of the base of the surrounding confining unit (approximately 30 m) has an apparent age of 19.8 years, which confirms the occurrence of downward flow. Young groundwater age dates (less than 32 years) also were obtained from wells in the Memphis aquifer at confined sites downgradient of the window, suggesting that a plume of young water is spreading outwards from the window and mixing with the older Memphis aquifer water. Preliminary inverse modeling of the site using a genetic algorithm coupled with a central finite difference flow model indicates a probable steady-state downward flux of about 12,000 m3/d through the window. Collection and analysis of additional groundwater samples are planned to examine geochemical conditions in the confining unit and in the Memphis aquifer upgradient of the window. These analyses will aid in developing a final conceptual model and in subsequent numerical modeling of mixing of the young recharge water with the older Memphis aquifer water.

MALDI-TOF MS for the Identification of Cultivable Organic-Degrading Bacteria in Contaminated Groundwater near Unconventional Natural Gas Extraction Sites.

PubMed

Santos, Inês C; Martin, Misty S; Carlton, Doug D; Amorim, Catarina L; Castro, Paula M L; Hildenbrand, Zacariah L; Schug, Kevin A

2017-08-10

Groundwater quality and quantity is of extreme importance as it is a source of drinking water in the United States. One major concern has emerged due to the possible contamination of groundwater from unconventional oil and natural gas extraction activities. Recent studies have been performed to understand if these activities are causing groundwater contamination, particularly with respect to exogenous hydrocarbons and volatile organic compounds. The impact of contaminants on microbial ecology is an area to be explored as alternatives for water treatment are necessary. In this work, we identified cultivable organic-degrading bacteria in groundwater in close proximity to unconventional natural gas extraction. Pseudomonas stutzeri and Acinetobacter haemolyticus were identified using matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF MS), which proved to be a simple, fast, and reliable method. Additionally, the potential use of the identified bacteria in water and/or wastewater bioremediation was studied by determining the ability of these microorganisms to degrade toluene and chloroform. In fact, these bacteria can be potentially applied for in situ bioremediation of contaminated water and wastewater treatment, as they were able to degrade both compounds.

MALDI-TOF MS for the Identification of Cultivable Organic-Degrading Bacteria in Contaminated Groundwater near Unconventional Natural Gas Extraction Sites

PubMed Central

Martin, Misty S.; Carlton, Doug D.; Castro, Paula M. L.; Hildenbrand, Zacariah L.; Schug, Kevin A.

2017-01-01

Groundwater quality and quantity is of extreme importance as it is a source of drinking water in the United States. One major concern has emerged due to the possible contamination of groundwater from unconventional oil and natural gas extraction activities. Recent studies have been performed to understand if these activities are causing groundwater contamination, particularly with respect to exogenous hydrocarbons and volatile organic compounds. The impact of contaminants on microbial ecology is an area to be explored as alternatives for water treatment are necessary. In this work, we identified cultivable organic-degrading bacteria in groundwater in close proximity to unconventional natural gas extraction. Pseudomonas stutzeri and Acinetobacter haemolyticus were identified using matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry (MALDI-TOF MS), which proved to be a simple, fast, and reliable method. Additionally, the potential use of the identified bacteria in water and/or wastewater bioremediation was studied by determining the ability of these microorganisms to degrade toluene and chloroform. In fact, these bacteria can be potentially applied for in situ bioremediation of contaminated water and wastewater treatment, as they were able to degrade both compounds. PMID:28796186

Simulation of groundwater conditions and streamflow depletion to evaluate water availability in a Freeport, Maine, watershed

USGS Publications Warehouse

Nielsen, Martha G.; Locke, Daniel B.

2012-01-01

In order to evaluate water availability in the State of Maine, the U.S. Geological Survey (USGS) and the Maine Geological Survey began a cooperative investigation to provide the first rigorous evaluation of watersheds deemed "at risk" because of the combination of instream flow requirements and proportionally large water withdrawals. The study area for this investigation includes the Harvey and Merrill Brook watersheds and the Freeport aquifer in the towns of Freeport, Pownal, and Yarmouth, Maine. A numerical groundwater- flow model was used to evaluate groundwater withdrawals, groundwater-surface-water interactions, and the effect of water-management practices on streamflow. The water budget illustrates the effect that groundwater withdrawals have on streamflow and the movement of water within the system. Streamflow measurements were made following standard USGS techniques, from May through September 2009 at one site in the Merrill Brook watershed and four sites in the Harvey Brook watershed. A record-extension technique was applied to estimate long-term monthly streamflows at each of the five sites. The conceptual model of the groundwater system consists of a deep, confined aquifer (the Freeport aquifer) in a buried valley that trends through the middle of the study area, covered by a discontinuous confining unit, and topped by a thin upper saturated zone that is a mixture of sandy units, till, and weathered clay. Harvey and Merrill Brooks flow southward through the study area, and receive groundwater discharge from the upper saturated zone and from the deep aquifer through previously unknown discontinuities in the confining unit. The Freeport aquifer gets most of its recharge from local seepage around the edges of the confining unit, the remainder is received as inflow from the north within the buried valley. Groundwater withdrawals from the Freeport aquifer in the study area were obtained from the local water utility and estimated for other categories. Overall, the public-supply withdrawals (105.5 million gallons per year (Mgal/yr)) were much greater than those for any other category, being almost 7 times greater than all domestic well withdrawals (15.3 Mgal/yr). Industrial withdrawals in the study area (2.0 Mgal/yr) are mostly by a company that withdraws from an aquifer at the edge of the Merrill Brook watershed. Commercial withdrawals are very small (1.0 Mgal/yr), and no irrigation or other agricultural withdrawals were identified in this study area. A three-dimensional, steady-state groundwater-flow model was developed to evaluate stream-aquifer interactions and streamflow depletion from pumping, to help refine the conceptual model, and to predict changes in streamflow resulting from changes in pumping and recharge. Groundwater levels and flow in the Freeport aquifer study area were simulated with the three-dimensional, finite-difference groundwater-flow modeling code, MODFLOW-2005. Study area hydrology was simulated with a 3-layer model, under steady-state conditions. The groundwater model was used to evaluate changes that could occur in the water budgets of three parts of the local hydrologic system (the Harvey Brook watershed, the Merrill Brook watershed, and the buried aquifer from which pumping occurs) under several different climatic and pumping scenarios. The scenarios were (1) no pumping well withdrawals; (2) current (2009) pumping, but simulated drought conditions (20-percent reduction in recharge); (3) current (2009) recharge, but a 50-percent increase in pumping well withdrawals for public supply; and (4) drought conditions and increased pumping combined. In simulated drought situations, the overall recharge to the buried valley is about 15 percent less and the total amount of streamflow in the model area is reduced by about 19 percent. Without pumping, infiltration to the buried valley aquifer around the confining unit decreased by a small amount (0.05 million gallons per day (Mgal/d)), and discharge to the streams increased by about 8 percent (0.3 Mgal/d). A 50-percent increase in pumping resulted in a simulated decrease in streamflow discharge of about 4 percent (0.14 Mgal/d). Streamflow depletion in Harvey Brook was evaluated by use of the numerical groundwater-flow model and an analytical model. The analytical model estimated negligible depletion from Harvey Brook under current (2009) pumping conditions, whereas the numerical model estimated that flow to Harvey Brook decreased 0.38 cubic feet per second (ft3/s) because of the pumping well withdrawals. A sensitivity analysis of the analytical model method showed that conducting a cursory evaluation using an analytical model of streamflow depletion using available information may result in a very wide range in results, depending on how well the hydraulic conductivity variables and aquifer geometry of the system are known, and how well the aquifer fits the assumptions of the model. Using the analytical model to evaluate the streamflow depletion with an incomplete understanding of the hydrologic system gave results that seem unlikely to reflect actual streamflow depletion in the Freeport aquifer study area. In contrast, the groundwater-flow model was a more robust method of evaluating the amount of streamflow depletion that results from withdrawals in the Freeport aquifer, and could be used to evaluate streamflow depletion in both streams. Simulations of streamflow without pumping for each measurement site were compared to the calibratedmodel streamflow (with pumping), the difference in the total being streamflow depletion. Simulations without pumping resulted in a simulated increase in the steady-state flow rate of 0.38 ft3/s in Harvey Brook and 0.01 ft3/s in Merrill Brook. This translates into a streamflow-depletion amount equal to about 8.5 percent of the steady-state base flow in Harvey Brook, and an unmeasurable amount of depletion in Merrill Brook. If pumping was increased by 50 percent and recharge reduced by 20 percent, the amount of streamflow depletion in Harvey Brook could reach 1.41 ft3/s.

Occurrence of fungicides and other pesticides in surface water, groundwater, and sediment from three targeted-use areas in the United States, 2009

USGS Publications Warehouse

Orlando, James L.; Smalling, Kelly L.; Reilly, Timothy J.; Boehlke, Adam; Meyer, Michael T.; Kuivila, Kathryn

2013-01-01

Surface-water, groundwater, and suspended- and bedsediment samples were collected in three targeted-use areas in the United States where potatoes were grown during 2009 and analyzed for an extensive suite of fungicides and other pesticides by gas chromatograph/mass spectrometry and liquid chromatography with tandem mass spectrometry. Fungicides were detected in all environmental matrices sampled during the study. The most frequently detected fungicides were azoxystrobin, boscalid, chlorothalonil, and pyraclostrobin. Other pesticides that were detected frequently included amino phosphonic acid (AMPA), atrazine, metolaclor, and the organochlorine insecticide p,p’-DDT and its degradates p,p’-DDD and p,p’-DDE. A greater number of pesticides were detected in surface water relative to the other environmental matrices sampled, and at least one pesticide was detected in 62 of the 63 surfacewater samples. The greatest numbers of pesticides and the maximum observed concentrations for most pesticides were measured in surface-water samples from Idaho. In eight surface- water samples (six from Idaho and two from Wisconsin), concentrations of bifenthrin, metolachlor, or malathion exceeded U.S. Environmental Protection Agency freshwater aquatic-life benchmarks for chronic toxicity to invertebrates. Thirteen pesticides, including seven fungicides, were detected in groundwater samples. Shallow groundwater samples collected beneath recently harvested potato fields contained more pesticides and had higher concentrations of pesticides than samples collected from other groundwater sources sampled during the study. Generally, pesticide concentrations were lower in groundwater samples than in surfacewater or sediment samples, with the exception of the fungicide boscalid, which was found to have its highest concentration in a shallow groundwater sample collected in Wisconsin. Thirteen pesticides, including four fungicides, were detected in suspended-sediment samples. The most frequently detected compounds were the fungicides boscalid, pyraclostrobin, and zoxamide, and the degradates p,p’-DDD and p,p’-DDE. Twenty pesticides, including six fungicides, were detected in bed-sediment samples. The most frequently detected compounds were pyraclostrobin, p,p’-DDT, p,p’-DDD, and p,p’-DDE.

Ground-Water Quality Data in the Coastal Los Angeles Basin Study Unit, 2006: Results from the California GAMA Program

USGS Publications Warehouse

Mathany, Timothy M.; Land, Michael; Belitz, Kenneth

2008-01-01

Ground-water quality in the approximately 860 square-mile Coastal Los Angeles Basin study unit (CLAB) was investigated from June to November of 2006 as part of the Statewide Basin Assessment Project of the Ground-Water Ambient Monitoring and Assessment (GAMA) Program. The GAMA Statewide Basin Assessment was developed in response to the Ground-Water Quality Monitoring Act of 2001, and is being conducted by the U.S. Geological Survey (USGS) in cooperation with the California State Water Resources Control Board (SWRCB). The Coastal Los Angeles Basin study was designed to provide a spatially unbiased assessment of raw ground-water quality within CLAB, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 69 wells in Los Angeles and Orange Counties. Fifty-five of the wells were selected using a spatially distributed, randomized grid-based method to provide statistical representation of the study area (?grid wells?). Fourteen additional wells were selected to evaluate changes in ground-water chemistry or to gain a greater understanding of the ground-water quality within a specific portion of the Coastal Los Angeles Basin study unit ('understanding wells'). Ground-water samples were analyzed for: a large number of synthetic organic constituents [volatile organic compounds (VOCs), gasoline oxygenates and their degradates, pesticides, polar pesticides, and pesticide degradates, pharmaceutical compounds, and potential wastewater-indicators]; constituents of special interest [perchlorate, N-nitrosodimethylamine (NDMA), 1,4-dioxane, and 1,2,3-trichloropropane (1,2,3-TCP)]; inorganic constituents that can occur naturally [nutrients, major and minor ions, and trace elements]; radioactive constituents [gross-alpha and gross-beta radiation, radium isotopes, and radon-222]; and microbial indicators. Naturally occurring isotopes [stable isotopic ratios of hydrogen and oxygen, and activities of tritium and carbon-14] and dissolved noble gases also were measured to help identify the sources and ages of the sampled ground water. Quality-control samples (blanks, replicates, and samples for matrix spikes) were collected at approximately one-fourth of the wells, and the results for these samples were used to evaluate the quality of the data for the ground-water samples. Field blanks rarely contained detectable concentrations of any constituent, suggesting that contamination was not a significant source of bias. Differences between replicate samples were within acceptable ranges, indicating acceptably low variability. Matrix spike recoveries were within acceptable ranges for most compounds. Assessment of the quality-control information resulted in applying ?V? codes to approximately 0.1 percent of the data collected for ground-water samples (meaning a constituent was detected in blanks as well as the corresponding environmental data). This study did not attempt to evaluate the quality of drinking water delivered to consumers; after withdrawal from the ground, water typically is treated, disinfected, and (or) blended with other waters to maintain acceptable drinking-water quality. Regulatory thresholds are applied to the treated drinking water that is served to the consumer, not to raw ground water. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with regulatory and non-regulatory health-based thresholds established by the U.S. Environmental Protection Agency (USEPA), California Department of Public Health (CDPH, formerly California Department of Health Services [CADHS]) and thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. Comparisons between data collected for this study and drinking-water thresholds are for illustrative purposes only, and are not indicative of compliance or non-compliance with those thresholds. VOCs were detected in alm

Supporting evaluation for the proposed plan for final remedial action for the groundwater operable unit at the chemical plant area of the Weldon Spring Site, Weldon Spring, Missouri.

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

2003-08-06

This report presents the technical information developed since the interim record of decision (IROD) was issued in September 2000 (U.S. Department of Energy [DOE] 2000). The information was incorporated into the evaluation that was performed in selecting the preferred alternative for the Chemical Plant groundwater operable unit (GWOU) of the Weldon Spring site. The contaminants of concern (COCs) in groundwater and springs are trichloroethylene (TCE), nitrate, uranium, and nitroaromatic compounds. The preferred alternative of monitored natural attenuation (MNA) coupled with institutional controls (ICs) and contingency activities is described in the ''Proposed Plan (PP) for Final Remedial Action for the Groundwatermore » Operable Unit at the Chemical Plant Area of the Weldon Spring Site, Weldon Spring, Missouri'' (DOE 2003b).« less

Groundwater quality in the Piedmont and Blue Ridge crystalline-rock aquifers, eastern United States

USGS Publications Warehouse

Lindsey, Bruce

2017-12-07

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Piedmont and Blue Ridge crystalline-rock aquifers constitute one of the important areas being evaluated.

A scientifically based nationwide assessment of groundwater quality in the United States

USGS Publications Warehouse

Alley, W.M.; Cohen, P.

1991-01-01

Beginning in 1986, the U.S. Geological Survey began an effort to develop a National Water-Quality Assessment Program. The basic premise underlying this initiative is that a better understanding of the quality of water resources across the country, both surface- and groundwater, is needed to develop effective programs and policies to meet the nation's water-quality concerns. The program will focus on water-quality conditions that are prevalent or large in scale, such as occur from nonpoint sources of pollution or from a high density of point sources. The design of the program is substantially different from the traditional approach of a diffuse national monitoring network. The major activities of the assessment program will be clustered within a set of hydrologic systems (river basins and aquifer systems), referred to as study units. In aggregate, the study units will account for a large part of the nation's water use and represent a wide range of settings across the country. Unique attributes of the program include: (1) the use of consistent study approaches, field and laboratory methods, water-quality measurements, and ancillary data measurements for all study units; (2) the development of a progressive understanding of water-quality conditions and trends in each study unit through long-term studies that rotate periods of intensive data collection and analysis with periods during which the assessment activities are less intensive; and (3) the focus of considerable effort on synthesizing results from among the study units to provide information on regional and national water-quality issues. ?? 1991 Springer-Verlag New York Inc.

Numerical simulation of groundwater flow at Puget Sound Naval Shipyard, Naval Base Kitsap, Bremerton, Washington

USGS Publications Warehouse

Jones, Joseph L.; Johnson, Kenneth H.; Frans, Lonna M.

2016-08-18

Information about groundwater-flow paths and locations where groundwater discharges at and near Puget Sound Naval Shipyard is necessary for understanding the potential migration of subsurface contaminants by groundwater at the shipyard. The design of some remediation alternatives would be aided by knowledge of whether groundwater flowing at specific locations beneath the shipyard will eventually discharge directly to Sinclair Inlet of Puget Sound, or if it will discharge to the drainage system of one of the six dry docks located in the shipyard. A 1997 numerical (finite difference) groundwater-flow model of the shipyard and surrounding area was constructed to help evaluate the potential for groundwater discharge to Puget Sound. That steady-state, multilayer numerical model with homogeneous hydraulic characteristics indicated that groundwater flowing beneath nearly all of the shipyard discharges to the dry-dock drainage systems, and only shallow groundwater flowing beneath the western end of the shipyard discharges directly to Sinclair Inlet.Updated information from a 2016 regional groundwater-flow model constructed for the greater Kitsap Peninsula was used to update the 1997 groundwater model of the Puget Sound Naval Shipyard. That information included a new interpretation of the hydrogeologic units underlying the area, as well as improved recharge estimates. Other updates to the 1997 model included finer discretization of the finite-difference model grid into more layers, rows, and columns, all with reduced dimensions. This updated Puget Sound Naval Shipyard model was calibrated to 2001–2005 measured water levels, and hydraulic characteristics of the model layers representing different hydrogeologic units were estimated with the aid of state-of-the-art parameter optimization techniques.The flow directions and discharge locations predicted by this updated model generally match the 1997 model despite refinements and other changes. In the updated model, most groundwater discharge recharged within the boundaries of the shipyard is to the dry docks; only at the western end of the shipyard does groundwater discharge directly to Puget Sound. Particle tracking for the existing long-term monitoring well network suggests that only a few wells intercept groundwater that originates as recharge within the shipyard boundary.

America's water: Agricultural water demands and the response of groundwater

NASA Astrophysics Data System (ADS)

Ho, M.; Parthasarathy, V.; Etienne, E.; Russo, T. A.; Devineni, N.; Lall, U.

2016-07-01

Agricultural, industrial, and urban water use in the conterminous United States (CONUS) is highly dependent on groundwater that is largely drawn from nonsurficial wells (>30 m). We use a Demand-Sensitive Drought Index to examine the impacts of agricultural water needs, driven by low precipitation, high agricultural water demand, or a combination of both, on the temporal variability of depth to groundwater across the CONUS. We characterize the relationship between changes in groundwater levels, agricultural water deficits relative to precipitation during the growing season, and winter precipitation. We find that declines in groundwater levels in the High Plains aquifer and around the Mississippi River Valley are driven by groundwater withdrawals used to supplement agricultural water demands. Reductions in agricultural water demands for crops do not, however, lead to immediate recovery of groundwater levels due to the demand for groundwater in other sectors in regions such as Utah, Maryland, and Texas.

Geochemical characterisation of shallow aquifer sediments of Matlab Upazila, Southeastern Bangladesh — Implications for targeting low-As aquifers

NASA Astrophysics Data System (ADS)

von Brömssen, Mattias; Häller Larsson, Sara; Bhattacharya, Prosun; Hasan, M. Aziz; Ahmed, Kazi Matin; Jakariya, M.; Sikder, Mohiuddin A.; Sracek, Ondra; Bivén, Annelie; Doušová, Barbora; Patriarca, Claudio; Thunvik, Roger; Jacks, Gunnar

2008-07-01

High arsenic (As) concentrations in groundwater pose a serious threat to the health of millions of people in Bangladesh. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilisation of As. The distribution of As is extremely heterogeneous both laterally and vertically. Groundwater abstracted from oxidised reddish sediments, in contrast to greyish reducing sediments, contains significantly lower amount of dissolved arsenic and can be a source of safe water. In order to study the sustainability of that mitigation option, this study describes the lithofacies and genesis of the sediments within 60 m depth and establishes a relationship between aqueous and solid phase geochemistry. Oxalate extractable Fe and Mn contents are higher in the reduced unit than in the oxidised unit, where Fe and Mn are present in more crystalline mineral phases. Equilibrium modelling of saturation indices suggest that the concentrations of dissolved Fe, Mn and PO43--tot in groundwater is influenced by secondary mineral phases in addition to redox processes. Simulating AsIII adsorption on hydroferric oxides using the Diffuse Layer Model and analytical data gave realistic concentrations of dissolved and adsorbed AsIII for the reducing aquifer and we speculate that the presence of high PO43--tot in combination with reductive dissolution results in the high-As groundwater. The study confirms high mobility of As in reducing aquifers with typically dark colour of sediments found in previous studies and thus validates the approach for location of wells used by local drillers based on sediment colour. A more systematic and standardised colour description and similar studies at more locations are necessary for wider application of the approach.

EFFECT OF GROUND-WATER REMEDIATION ACTIVITIES ON INDIGENOUS MICROFLORA

EPA Science Inventory

The United States Environmental Protection Agency (EPA), working with the Interagency DNAPL Consortium, completed an independent evaluation of microbial responses to ground-water remediation technology demonstrations at Launch Pad 34 at Cape Canaveral Air Station in Brevard Count...

Groundwater level response to low-frequency (interannual to multidecadal) climate variability: an overview across Portugal

NASA Astrophysics Data System (ADS)

Neves, M. L.

2017-12-01

The impact of climate variability on groundwater systems is central to the successful management and sustainability of water resources. In Portugal, strong changes in the seasonal distribution of precipitation, with a concentration of rainfall during the winter season and an increase in the frequency and intensity of droughts, in conjunction with warming, are expected to have a profound impact on water resources. Nonetheless, there is still limited knowledge on the impact of climate variability on aquifer systems across the country. The primary goal of this study is to provide a national-scale assessment of the relative contribution of climate to the temporal and spatial variance of groundwater recharge across the four main hydrogeological units in which the country is divided. Monthly hydrological data sets spanning a common 30 year period include groundwater levels from the Portuguese National System for Water Research Information and precipitation data from both meteorological stations and ERA-Interim global atmospheric reanalysis. The links between large-scale climatic patterns, precipitation, and groundwater levels are explored using singular spectral analysis, wavelet coherence and lag correlation methods. Hydrologic time-series sampling diverse geographic regions and aquifer types have common non-stationary oscillatory components, which can be associated with the leading modes of atmospheric circulation in the western north Atlantic, namely the North Atlantic (NAO) and the Eastern Atlantic (EA) oscillations. Maps of the spatial distribution of the relative contribution of each mode of variability to the total variance of the groundwater levels illustrate which atmospheric mode impacts the most a particular aquifer. The results display the links between groundwater recharge and climate teleconnections but also emphasize the distinctive types of modulation of the climate signals among the several hydrogeological units and aquifer systems under consideration. This work is supported by FCT- project UID/GEO/50019/2013 - IDL.

Quantifying Groundwater Availability in Fractured Rock Aquifers of Northern Ugandan Refugee Settlements

NASA Astrophysics Data System (ADS)

Frederiks, R.; Lowry, C.; Mutiibwa, R.; Moisy, S.; Thapa, L.; Oriba, J.

2017-12-01

In the past two years, Uganda has witnessed an influx of nearly one million refugees who have settled in the sparsely populated northwestern region of the country. This rapid population growth has created high demand for clean water resources. Water supply has been unable to keep pace with demand because the fractured rock aquifers underlying the region often produce low yielding wells. To facilitate management of groundwater resources, it is necessary to quantify the spatial distribution of groundwater. In fractured rock aquifers, there is significant spatial variability in water storage because fractures must be both connected and abundant for water to be extracted in usable quantities. Two conceptual models were evaluated to determine the groundwater storage mechanism in the fractured crystalline bedrock aquifers of northwestern Uganda where by permeability is controlled by faulting, which opens up fractures in the bedrock, or weathering, which occurs when water dissolves components of rock. In order to test these two conceptual models, geologic well logs and available hydrologic data were collected and evaluated using geostatistical and numerical groundwater models. The geostatistical analysis focused on identifying spatially distributed patterns of high and low water yield. The conceptual models were evaluated numerically using four inverse groundwater MODFLOW models based on head and estimated flux targets. The models were based on: (1) the mapped bedrock units using an equivalent porous media approach (2) bedrock units with the addition of known fault zones (3) bedrock units with predicted units of deep weathering based on surface slopes, and (4) bedrock units with discrete faults and simulated weathered zones. Predicting permeable zones is vital for water well drilling in much of East Africa and South America where there is an abundance of both fractured rock and tectonic activity. Given that the population of these developing regions is growing, the demand for sufficient clean water is likely to increase significantly in the next few decades. Thus, it is necessary to improve our ability to predict locations of permeable zones in fractured rock aquifers.

Quantifying Nitrogen Transport from Riparian Groundwater Seeps to a Headwater Stream in an Agricultural Watershed

NASA Astrophysics Data System (ADS)

Redder, B.; Buda, A. R.; Kennedy, C. D.; Folmar, G.; DeWalle, D. R.; Boyer, E. W.

2017-12-01

Headwater streams in the Northeast region of the United States typically receive more than 50% of their base flow from groundwater, either by diffuse discharge through the streambed or by localized discharge through riparian seeps. It is very difficult to separate the individual contributions of these two groundwater fluxes to streamflow. Furthermore, riparian seeps show significant variability in discharge and nutrient concentration, adding uncertainty to estimates of groundwater-based nitrogen inputs to streams. In this study, we combined stream measurements at two different scales to quantify groundwater discharge by matrix flow through the streambed and by macropore flow through the riparian zone. The study site was a 175-m stream reach located in a heavily cultivated 45-hectare watershed in east-central Pennsylvania. Differential streamflow gauging and streambed measurements of hydraulic head gradient, hydraulic conductivity, and groundwater chemistry were used to solve for the riparian groundwater flux in a reach mass balance equation. Adopting a mass balance approach, riparian groundwater fluxes ranged from 115-205 m3 d-1, transporting 2-4 kg N d-1 of nitrate from the fractured bedrock aquifer to the stream. Air-water manometer readings from short-screened piezometers installed in the shallow streambed (30 cm) indicated slightly losing head gradients between the stream and groundwater, despite substantial (36-66%) increases in stream flow along the stream reach. Preliminary chemical data for the stream, streambed, and shallow ground water suggest that the stream is partially disconnected from the underlying aquifer and that riparian groundwater seeps supply essentially all water and nitrogen to the system. These results, along with the comparison of shallow and deep aquifer water with seep chemistry, provide insight into sources of water to riparian groundwater seeps and allow us to determine the transport and fate of nitrogen in a fractured aquifer system. The use of water isotopes and hydrometric data will be used to further test the hypothesis that this is a perched system disconnected from the aquifer below.

Analysis of modern and Pleistocene hydrologic exchange between Saginaw Bay (Lake Huron) and the Saginaw Lowlands area

USGS Publications Warehouse

Hoaglund, J. R.; Kolak, J.J.; Long, D.T.; Larson, G.J.

2004-01-01

Two numerical models, one simulating present groundwater flow conditions and one simulating ice-induced hydraulic loading from the Port Huron ice advance, were used to characterize both modern and Pleistocene groundwater exchange between the Michigan Basin and near-surface water systems of Saginaw Bay (Lake Huron) and the surrounding Saginaw Lowlands area. These models were further used to constrain the origin of saline, isotopically light groundwater, and porewater from the study area. Output from the groundwater-flow model indicates that, at present conditions, head in the Marshall aquifer beneath Saginaw Bay exceeds the modern lake elevation by as much as 21 m. Despite this potential for flow, simulated groundwater discharge through the Saginaw Bay floor constitutes only 0.028 m3 s-1 (???1 cfs). Bedrock lithology appears to regulate the rate of groundwater discharge, as the portion of the Saginaw Bay floor underlain by the Michigan confining unit exhibits an order of magnitude lower flux than the portion underlain by the Saginaw aquifer. The calculated shoreline discharge of groundwater to Saginaw Bay is also relatively small (1.13 m3 s-1 or ???40 cfs) because of low gradients across the Saginaw Lowlands area and the low hydraulic conductivities of lodgement tills and glacial-lake clays surrounding the bay. In contrast to the present groundwater flow conditions, the Port Huron ice-induced hydraulic-loading model generates a groundwater-flow reversal that is localized to the region of a Pleistocene ice sheet and proglacial lake. This area of reversed vertical gradient is largely commensurate with the distribution of isotopically light groundwater presently found in the study area. Mixing scenarios, constrained by chloride concentrations and ??18O values in porewater samples, demonstrate that a mixing event involving subglacial recharge could have produced the groundwater chemistry currently observed in the Saginaw Lowlands area. The combination of models and mixing scenarios indicates that structural control is a major influence on both the present and Pleistocene flow systems.

Assessing groundwater availability in the Northern Atlantic Coastal Plain aquifer system

USGS Publications Warehouse

Masterson, John P.; Pope, Jason P.; Monti, Jack; Nardi, Mark R.

2011-01-01

The U.S. Geological Survey's Groundwater Resources Program is conducting an assessment of groundwater availability throughout the United States to gain a better understanding of the status of the Nation's groundwater resources and how changes in land use, water use, and climate may affect those resources. The goal of this National assessment is to improve our ability to forecast water availability for future economic and environmental uses. Assessments will be completed for the Nation's principal aquifer systems to help characterize how much water is currently available, how water availability is changing, and how much water we can expect to have in the future (Reilly and others, 2008). The concept of groundwater availability is more than just how much water can be pumped from any given aquifer. Groundwater availability is a function of many factors, including the quantity and quality of water and the laws, regulations, economics, and environmental factors that control its use. The primary objective of the North Atlantic Coastal Plain groundwater-availability study is to identify spatial and temporal changes in the overall water budget by more fully determining the natural and human processes that control how water enters, moves through, and leaves the groundwater system. Development of tools such as numerical models can help hydrologists gain an understanding of this groundwater system, allowing forecasts to be made about the response of this system to natural and human stresses, and water quality and ecosystem health to be analyzed, throughout the region.

Application of Remote Sensing for Generation of Groundwater Prospect Map

NASA Astrophysics Data System (ADS)

Inayathulla, Masool

2016-07-01

In developing accurate hydrogeomorphological analysis, monitoring, ability to generate information in spatial and temporal domain and delineation of land features are crucial for successful analysis and prediction of groundwater resources. However, the use of RS and GIS in handling large amount of spatial data provides to gain accurate information for delineating the geological and geomorphological characteristics and allied significance, which are considered as a controlling factor for the occurrence and movement of groundwater used IRS LISS II data on 1: 50000 scale along with topographic maps in various parts of India to develop integrated groundwater potential zones. The present work is an attempt to integrate RS and GIS based analysis and methodology in groundwater potential zone identification in the Arkavathi Basin, Bangalore, study area. The information on geology, geomorphology, soil, slope, rainfall, water level and land use/land cover was gathered, in addition, GIS platform was used for the integration of various themes. The composite map generated was further classified according to the spatial variation of the groundwater potential. Five categories of groundwater potential zones namely poor, moderate to poor, moderate, good and very good were identified and delineated. The hydrogeomorphological units like valley fills and alluvial plain and are potential zones for groundwater exploration and development and valley fills associated with lineaments is highly promising area for ground water recharging. The spatial variation of the potential indicates that groundwater occurrence is controlled by geology, land use / land cover, slope and landforms.

Geophysics- and geochemistry-based assessment of the geochemical characteristics and groundwater-flow system of the U.S. part of the Mesilla Basin/Conejos-Médanos aquifer system in Doña Ana County, New Mexico, and El Paso County, Texas, 2010–12

USGS Publications Warehouse

Teeple, Andrew P.

2017-06-16

One of the largest rechargeable groundwater systems by total available volume in the Rio Grande/Río Bravo Basin (hereinafter referred to as the “Rio Grande”) region of the United States and Mexico, the Mesilla Basin/Conejos-Médanos aquifer system, supplies water for irrigation as well as for cities of El Paso, Texas; Las Cruces, New Mexico; and Ciudad Juárez, Chihuahua, Mexico. The U.S. Geological Survey in cooperation with the Bureau of Reclamation assessed the groundwater resources in the Mesilla Basin and surrounding areas in Doña Ana County, N. Mex., and El Paso County, Tex., by using a combination of geophysical and geochemical methods. The study area consists of approximately 1,400 square miles in Doña Ana County, N. Mex., and 100 square miles in El Paso County, Tex. The Mesilla Basin composes most of the study area and can be divided into three parts: the Mesilla Valley, the West Mesa, and the East Bench. The Mesilla Valley is the part of the Mesilla Basin that was incised by the Rio Grande between Selden Canyon to the north and by a narrow valley (about 4 miles wide) to the southeast near El Paso, Tex., named the Paso del Norte, which is sometimes referred to in the literature as the “El Paso Narrows.”Previously published geophysical data for the study area were compiled and these data were augmented by collecting additional geophysical and geochemical data. Geophysical resistivity measurements from previously published helicopter frequency domain electromagnetic data, previously published direct-current resistivity soundings, and newly collected (2012) time-domain electromagnetic soundings were used in the study to detect spatial changes in the electrical properties of the subsurface, which reflect changes that occur within the hydrogeology. The geochemistry of the groundwater system was evaluated by analyzing groundwater samples collected in November 2010 for physicochemical properties, major ions, trace elements, nutrients, pesticides (reported but not used in the assessment), and environmental tracers. The data obtained from these samples (with the exception of the pesticide data) were used to gain insights into processes controlling the groundwater movement through the groundwater system in the study area. Results from the geophysical and geochemical assessments facilitated the interpretation of the geochemical characteristics of the groundwater sources and geochemical groups within the groundwater system.The groundwater-flow system in the study area consists primarily of the Mesilla Basin aquifer system, which can be divided into four hydrogeologic units by using an informal classification scheme based on basin-fill stratigraphy and sedimentology with an emphasis on aquifer characteristics. The four hydrogeologic units are (1) the Rio Grande alluvium, which is the shallow aquifer of the Mesilla Basin within the confines of the Mesilla Valley, and the three hydrogeologic units that compose the Santa Fe Group: (2) the lower part of the Santa Fe Group, which is the least productive zone, (3) the middle part of the Santa Fe Group, which is the primary water-bearing hydrogeologic unit in the basin and is generally saturated, and (4) the upper part of the Santa Fe Group, which is the most productive water-bearing unit within the Santa Fe Group but is only partially saturated in the north and largely unsaturated in the south and western parts of the Mesilla Basin.The helicopter frequency domain electromagnetic survey results indicated that approximately half of the resistivity values were less than 10 ohm-meters at depths of 50 and 100 feet with a transition where the resistivity values changed from relatively high values (greater than 20 ohm-meters) to relatively low resistivity values (less than 10 ohm-meters) near Vado, New Mexico. Slightly more than 25 percent of the gridded resistivity values from the three-dimensional grid of the combined inverse modeling results of the direct-current resistivity and time-domain electromagnetic soundings were equal to or less than 10 ohm-meters with large regions of low resistivity becoming apparent in the southernmost part of the study area near the Paso Del Norte where these low resistivity features are spatially the widest at or below the top of the bedrock. These low resistivity values might represent clayey deposits, sediments composed largely of sand and gravel saturated with saline water, or both. Historical dissolved-solids-concentration data within the surface geophysical subset area of the study area were compiled and compared to the inverse modeling results of the combined direct-current resistivity and time-domain soundings; this comparison was done to strengthen the interpretation made from the combined inverse modeling results that the low resistivity features were representative of sand and gravel deposits saturated with saline water and not clayey deposits.Water-level altitudes within the Rio Grande alluvium generally decreased from north to south, with a west to east decrease in water-level altitudes near Las Cruces, New Mexico, as a result of groundwater pumping. Groundwater flow within the Santa Fe Group is more complex than the groundwater flow within the Rio Grande alluvium because of the larger lateral and vertical extent of the Santa Fe Group compared to the Rio Grande alluvium. Groundwater from the Organ Mountains flows directly south towards the Paso del Norte. Groundwater from the Robledo Mountains, the Rough and Ready Hills, and the Sleeping Lady Hills generally flows to the southeast. Groundwater flowing near the north end of the midbasin uplift generally continues east towards the Rio Grande and then flows south on the east side of the midbasin uplift. Groundwater flowing near the west side of the midbasin uplift generally continues south parallel to the faults that make up the midbasin uplift and then flows east towards the Paso del Norte when it reaches the south end of the midbasin uplift. Groundwater from the Aden Hills and the East and West Potrillo Mountains flows to the south end of the midbasin uplift and then continues east towards the Paso del Norte. Throughout most of the Mesilla Valley, the vertical hydraulic gradient was downward because the water-level altitude in the Rio Grande alluvium was higher than it was in the Santa Fe Group, but in some areas (typically in the middle and southern parts of the Mesilla Valley), the vertical hydraulic gradient was substantially reduced or even reversed to an upward hydraulic gradient.The geochemistry data indicate that there was a complex system of multiple geochemical endmembers and mixing between these endmembers with recharge to the Rio Grande alluvium and Santa Fe Group composed mostly of seepage from the Rio Grande, inflows from deeper or neighboring water systems, and mountain-front recharge. Five distinct geochemical groups were identified in the Mesilla Basin study area: (1) ancestral Rio Grande (pre-Pleistocene) geochemical group, (2) modern Rio Grande (Pleistocene to present) geochemical group, (3) mountain-front geochemical group, (4) deep groundwater upwelling geochemical group, and (5) unknown freshwater geochemical group. The ancestral Rio Grande groundwater was water that recharged into the system as seepage losses from the ancestral Rio Grande; this groundwater generally flows from north to south-southeast towards the Paso del Norte. Groundwater on the west side of the midbasin uplift generally flows south until it reaches the southern part of the study area; from the southern part of the study area, the groundwater flows east towards the Paso del Norte. Groundwater on the east side of the midbasin uplift flows south-southeast towards the Paso del Norte where it mixes with groundwater from the modern Rio Grande, uplifted areas in the west, and the deep saline source. The water type of the modern Rio Grande geochemical group ranged from calcium-sulfate water type in the northern part of the study area to sodium-chloride-sulfate water type in the southern part of the study area; from north to south there was a substantial increase in specific conductance, strontium-87/strontium-86 ratio, potassium, and the trace metals of iron and lithium, changing the water chemistry such that it became similar to the water chemistry of the deep groundwater upwelling geochemical group. From age-dating results, water in the modern Rio Grande geochemical group was recharged to the Rio Grande alluvium within the past 10 years. The mountain-front geochemical group was generally old water (apparent age was greater than 10,000 carbon-14 years before present) that was somewhat mineralized and has relatively high concentrations of fluoride and silica, which might indicate longer exposure to volcanic and siliciclastic rocks or aluminosilicate minerals. There were five different locations of recharge determined from the groundwater geochemistry within the mountain-front geochemical group, all having a slightly different geochemical signature: (1) the Rough and Ready Hills, Robledo Mountains, and the Sleeping Lady Hills, (2) the Doña Ana Mountains, (3) the Aden Hills and West Potrillo Mountains, (4) the East Potrillo Mountains, and (5) the Sierra Juárez in Mexico. The groundwater from the Rough and Ready Hills, Robledo Mountains, the Sleeping Lady Hills, and the Doña Ana Mountains generally flows toward the Rio Grande and eventually mixes together and with the modern Rio Grande groundwater. The groundwater originating from the Aden Hills and East and West Potrillo Mountains generally flows east to southeast at a slow rate and eventually mixes and continues east, where it mixes with groundwater from the ancestral Rio Grande geochemical group and with the groundwater from the Sierra Juárez. The groundwater from the Sierra Juárez flows north and then east towards the Paso del Norte where it mixes with groundwater from the uplifted areas in the west, ancestral and modern Rio Grande groundwater, and the upwelling groundwater from a deep saline source. The deep groundwater upwelling geochemical group had the highest concentrations of bicarbonate, potassium, silica, aluminum, iron, and lithium within the study area, indicating that it had been in contact with carbonate and siliciclastic rocks for a much longer period of time and at higher temperatures compared to the other geochemical groups, and was most likely ancient marine groundwater originating from the Paleozoic and Cretaceous carbonate rocks which was upwelling into the Mesilla Basin aquifer system in the southeastern part of the study area through the extensive fault systems. Direct-current resistivity and time-domain electromagnetic soundings support the interpretation of ancient marine groundwater upwelling into the Mesilla Basin aquifer system, as do the analytical results from wells, and the helicopter frequency domain electromagnetic data collected along the Rio Grande. The hydrogen-2/hydrogen-1 ratio and oxygen-18/oxygen-16 ratio isotopic results for samples in the unknown freshwater geochemical group did not plot on the Rio Grande evaporation line, indicating this group did not have a Rio Grande signature (that is, there was no isotopic evidence of a component of Rio Grande water) and it also had the lowest mineralized content of any geochemical group in the study area.

Louisiana ground-water map no. 1: potentiometric surface, 1985, and water-level changes, 1983-85, of the Chicot aquifer in southwestern Louisiana

USGS Publications Warehouse

Fendick, Robert B.; Nyman, Dale J.

1987-01-01

The Chicot aquifer is the principle source of groundwater in southwestern Louisiana and is the most extensively pumped (nearly 1 billion gallons per day) aquifer in the State. Withdrawals from the Chicot aquifer are used primarily for irrigation. Two maps show the generalized potentiometric surfaces of the upper sand unit ('200-ft ' sand in the Lake Charles area) and the ' 500-ft ' sand of the Chicot aquifer. General water level altitudes and flow directions may be inferred from these maps which were prepared in cooperation with the Louisiana Department of Transportation and Development, Office of Public Works. Previous studies of groundwater hydrology in southwestern Louisiana are included in selected references. (Lantz-PTT)

Stable isotope compositions of waters in the Great Basin, United States 3. Comparison of groundwaters with modern precipitation

USGS Publications Warehouse

Smith, G.I.; Friedman, I.; Veronda, G.; Johnson, C.A.

2002-01-01

Groundwater samples from wells and springs, scattered over most of the Great Basin province, were collected and analyzed for their isotopic makeup. They were augmented by previously published isotopic data on groundwaters from southeast California and by several hundred unpublished isotopic analyses. The ratio of 2H (deuterium, D) to 1H, in water samples from valleys in parts of California, Idaho, Nevada, Oregon, and Utah, are here compared with the winter, summer, and annual isotopic compositions of precipitation falling in or near the sampled areas. The main goal of this study was to identify basins where the groundwaters have isotopic compositions that are "lighter" (depleted in the heavier isotope, D) relative to modern winter precipitation. Where these basins do not adjoin substantially higher terrain, we consider those light groundwaters to be of Pleistocene age and thus more than 10,000 years old. Where the groundwater is 10 to 19??? lighter than local winter precipitation, we consider it to be possibly an indication of Pleistocene water; where the ??D makeup is >20??? lighter, we consider it to be probably Pleistocene water. More than 80 sites underlain by waters of possible or probable Pleistocene age were identified.

Using SWAT-MODFLOW to simulate groundwater flow and groundwater-surface water interactions in an intensively irrigated stream-aquifer system

NASA Astrophysics Data System (ADS)

Wei, X.; Bailey, R. T.

2017-12-01

Agricultural irrigated watersheds in semi-arid regions face challenges such as waterlogging, high soil salinity, reduced crop yield, and leaching of chemical species due to extreme shallow water tables resulting from long-term intensive irrigation. Hydrologic models can be used to evaluate the impact of land management practices on water yields and groundwater-surface water interactions in such regions. In this study, the newly developed SWAT-MODFLOW, a coupled surface/subsurface hydrologic model, is applied to a 950 km2 watershed in the Lower Arkansas River Valley (southeastern Colorado). The model accounts for the influence of canal diversions, irrigation applications, groundwater pumping, and earth canal seepage losses. The model provides a detailed description of surface and subsurface flow processes, thereby enabling detailed description of watershed processes such as runoff, infiltration, in-streamflow, three-dimensional groundwater flow in a heterogeneous aquifer system with sources and sinks (e.g. pumping, seepage to subsurface drains), and spatially-variable surface and groundwater exchange. The model was calibrated and tested against stream discharge from 5 stream gauges in the Arkansas River and its tributaries, groundwater levels from 70 observation wells, and evapotranspiration (ET) data estimated from satellite (ReSET) data during the 1999 to 2007 period. Since the water-use patterns within the study area are typical of many other irrigated river valleys in the United States and elsewhere, this modeling approach is transferable to other regions.

A hydrologic and archeologic study of climate change in Al Ain, United Arab Emirates

NASA Astrophysics Data System (ADS)

Jorgensen, Donald G.; Yasin al-Tikiriti, Walid

2003-01-01

Aridity trends established for Al Ain, United Arab Emirates, for the past 4500 years correlate with the trends of increased well depths and declining groundwater levels. Depth of wells found at archeologic sites at Hili near Al Ain were correlated to groundwater levels. Trends of declining groundwater levels were related to trends of increasing aridity (climate change). The increasing aridity had a pronounced affect on man's development in Al Ain area as well. For example, nonirrigation farming could not be successfully sustained at the end of the Bronze Age. This thwarted the economic development until the falaj (a water conveyance structure) was introduced in the Iron Age. The aridity trends in Al Ain correspond to contemporaneous aridity trends noted in Mesopotamia and the Dead Sea area, as well as the Middle East, Mediterranean, and northern Africa, in general. Other global climatic changes that are contemporaneous with climate change at Al Ain have been noted. The increased aridity (desertification) trends at Al Ain are contemporaneous with increased atmospheric CO 2 trends as reported by Indermuhle et al. [Nature (398) 121].

The concept of hydrologic landscapes

USGS Publications Warehouse

Winter, T.C.

2001-01-01

Hydrologic landscapes are multiples or variations of fundamental hydrologic landscape units. A fundamental hydrologic landscape unit is defined on the basis of land-surface form, geology, and climate. The basic land-surface form of a fundamental hydrologic landscape unit is an upland separated from a lowland by an intervening steeper slope. Fundamental hydrologic landscape units have a complete hydrologic system consisting of surface runoff, ground-water flow, and interaction with atmospheric water. By describing actual landscapes in terms of land-surface slope, hydraulic properties of soils and geologic framework, and the difference between precipitation and evapotranspiration, the hydrologic system of actual landscapes can be conceptualized in a uniform way. This conceptual framework can then be the foundation for design of studies and data networks, syntheses of information on local to national scales, and comparison of process research across small study units in a variety of settings. The Crow Wing River watershed in central Minnesota is used as an example of evaluating stream discharge in the context of hydrologic landscapes. Lake-research watersheds in Wisconsin, Minnesota, North Dakota, and Nebraska are used as an example of using the hydrologic-landscapes concept to evaluate the effect of ground water on the degree of mineralization and major-ion chemistry of lakes that lie within ground-water flow systems.

Superfund record of decision (EPA Region 5): Skinner Landfill, West Chester, OH, June 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-06-04

The decision document presents the selected final remedial action for the Skinner Landfill site in West Chester, Ohio. The remedy is the second and final of two operable units for this site. The first operable unit addressed immediate site concerns, through the construction of a fence around the contaminated area, and by offering an alternate supply of drinking water to the potentially affected users of groundwater. This final operable unit addresses potential future migration of site contaminants into the groundwater and will limit the potential for direct exposure of site contaminants to humans through source control measures.

Reliable groundwater levels: failures and lessons learned from modeling and monitoring studies

NASA Astrophysics Data System (ADS)

Van Lanen, Henny A. J.

2017-04-01

Adequate management of groundwater resources requires an a priori assessment of impacts of intended groundwater abstractions. Usually, groundwater flow modeling is used to simulate the influence of the planned abstraction on groundwater levels. Model performance is tested by using observed groundwater levels. Where a multi-aquifer system occurs, groundwater levels in the different aquifers have to be monitored through observation wells with filters at different depths, i.e. above the impermeable clay layer (phreatic water level) and beneath (artesian aquifer level). A reliable artesian level can only be measured if the space between the outer wall of the borehole (vertical narrow shaft) and the observation well is refilled with impermeable material at the correct depth (post-drilling phase) to prevent a vertical hydraulic connection between the artesian and phreatic aquifer. We were involved in improper refilling, which led to impossibility to monitor reliable artesian aquifer levels. At the location of the artesian observation well, a freely overflowing spring was seen, which implied water leakage from the artesian aquifer affected the artesian groundwater level. Careful checking of the monitoring sites in a study area is a prerequisite to use observations for model performance assessment. After model testing the groundwater model is forced with proposed groundwater abstractions (sites, extraction rates). The abstracted groundwater volume is compensated by a reduction of groundwater flow to the drainage network and the model simulates associated groundwater tables. The drawdown of groundwater level is calculated by comparing the simulated groundwater level with and without groundwater abstraction. In lowland areas, such as vast areas of the Netherlands, the groundwater model has to consider a variable drainage network, which means that small streams only carry water during the wet winter season, and run dry during the summer. The main streams drain groundwater throughout the whole year. We simulated groundwater levels with a steady-state groundwater flow model with and without groundwater abstraction for the wet and dry season, i.e. considering a high (all streams included) and low drainage density (only major streams), respectively. Groundwater drawdown maps for the wet and dry season were compiled. Stakeholders (farmers, ecologists) were very concerned about the large drawdowns. After a while and discussions with the Water Supply Company and stakeholders, we realised that we had calculated unrealistic large drawdowns of the phreatic groundwater level for the dry season. We learnt that by applying a steady-state model we did not take into account the large volume of groundwater, which is released from the groundwater storage. The transient groundwater model that we developed then, showed that the volume of groundwater released from the storage per unit of time is significant and that the drawdown of the phreatic groundwater level by the end of the dry period is substantially smaller than the one simulated by the steady-state model. The results of the transient groundwater flow model agreed rather well with the pumping test that lasted the whole dry season.

Selected ground-water information for the Pasco basin and adjacent areas, Washington, 1986-1989

USGS Publications Warehouse

Drost, B.W.; Schurr, K.M.; Lum, W. E.

1989-01-01

The U.S. Geological Survey, in cooperation with the United States Department of Energy, conducted a study of the Pasco basin and adjacent areas, Washington, in support of the Basalt Waste Isolation Project at the Hanford site, Washington. The purpose of the study was to develop a data set that would help define the groundwater-flow system of the Pasco Basin. This report contains the basic data, without interpretation, that were collected from the start of the project in February 1986 through January 1989. Information presented is from the U.S. Bureau of Reclamation, State of Washington Department of Ecology , US Army Corps of Engineers, Kennewick Irrigation District, and the Survey, and consists of well location and construction data, records of water levels in the wells, and aquifer designations for each well. The aquifer designation represents the geohydrologic unit to which the well is reported to be open. (USGS)

Milan Army Ammunition Plant remedial investigation report: Volume 1. Final report 89-91

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okusu, N.; Hall, H.; Orndorff, A.

1991-12-09

A Remedial Investigation at the Milan Army Ammunition Plant, TN, was conducted for the US Army Toxic and Hazardous Materials Agency, under the terms of an Interagency Agreement with the State of Tennessee and the US Environmental Protection Agency. The study focused on the CERCLA site and selected RCRA regulated units identified by previous studies as potential sources of contamination. A broad range of chemicals including metals, explosives, and other organic compounds were found in source areas and in groundwater. The results of a risk assessment indicate that unacceptable levels of human health risks potentially exist. Conceptual models of sitemore » and unit characteristics were formulated to explain major findings, and areas not contributing to the problem were identified. For many source areas, major unknowns exist regarding hydrology, extent of contamination, and current and future impacts to groundwater quality.« less

Role of different types of solid models in hydrodynamic modeling and their effects on groundwater protection processes

NASA Astrophysics Data System (ADS)

Bódi, Erika; Buday, Tamás; McIntosh, Richard William

2013-04-01

Defining extraction-modified flow patterns with hydrodynamic models is a pivotal question in preserving groundwater resources regarding both quality and quantity. Modeling is the first step in groundwater protection the main result of which is the determination of the protective area depending on the amount of extracted water. Solid models have significant effects on hydrodynamic models as they are based on the solid models. Due to the legislative regulations, on protection areas certain restrictions must be applied which has firm consequences on economic activities. In Hungarian regulations there are no clear instructions for the establishment of either geological or hydrodynamic modeling, however, modeling itself is an obligation. Choosing the modeling method is a key consideration for further numerical calculations and it is decisive regarding the shape and size of the groundwater protection area. The geometry of hydrodynamic model layers is derived from the solid model. There are different geological approaches including lithological and sequence stratigraphic classifications furthermore in the case of regional models, formation-based hydrostratigraphic units are also applicable. Lithological classification is based on assigning and mapping of lithotypes. When the geometry (e.g. tectonic characteristics) of the research area is not known, horizontal bedding is assumed the probability of which can not be assessed based on only lithology. If the geological correlation is based on sequence stratigraphic studies, the cyclicity of sediment deposition is also considered. This method is more integrated thus numerous parameters (e.g. electrofacies) are taken into consideration studying the geological conditions ensuring more reliable modeling. Layers of sequence stratigraphic models can be either lithologically homogeneous or they may include greater cycles of sediments containing therefore several lithological units. The advantage of this is that the modeling can handle pinching out lithological units and lenticular bodies easier while most hydrodynamic softwares cannot handle flow units related to such model layers. Interpretation of tectonic disturbance is similar. In Hungary groundwater is extracted mainly from Pleistocene and Pannonian aquifers sediments of which were deposited in the ancient Pannonian Lake. When the basin lost its open-marine connection eustasy had no direct effects on facies changes therefore subsidence and sediment supply became the main factors. Various basin-filling related facies developed including alluvial plain facies, different delta facies types and pelitic deep-basin facies. Creating solid models based on sequence stratigraphic methods requires more raw data and also genetic approaches, in addition more working hours hence this method is seldom used in practice. Lithology-based models can be transformed into sequence stratigraphic models by extending the data base (e.g. detecting more survey data). In environments where the obtained models differ significantly notable changes can occur in the supply directions in addition the groundwater travel-time of the two models even on equal extraction terms. Our study aims to call attention to the consequences of using different solid models for typical depositional systems of the Great Hungarian Plain and to their effects on groundwater protection.

Radon in ground water of the Lower Susqehanna and Potomac River basins

USGS Publications Warehouse

Lindsey, Bruce D.; Ator, Scott W.

1996-01-01

Ground-water samples collected from 267 wells were analyzed for radon as part of a water-quality reconnaissance of subunits of the Lower Susquehanna and Potomac River Basins conducted by the United States Geological Survey (USGS) as part of the National Water-Quality Assessment (NAWQA) program. Radon is a product of the radioactive decay of uranium. Airborne radon has been cited by the Surgeon General of the United States as the second-leading cause of lung cancer and the United States Environmental Protection Agency (USEPA) has identified ground-water supplies as possible contributing sources of indoor radon. Eighty percent of ground-water samples collected for this study were found to contain radon at activities greater than 300 pCi/L (picocuries per liter), the USEPA's proposed Maximum Contaminant Level for radon in drinking water, and 31 percent of samples contained radon at activities greater than 1,000 pCi/L. The 10 subunits where samples were collected were grouped into three classes - median ground-water radon activity less than 300 pCi/L, between 300 pCi/L and 1,000 pCi/L, and greater than 1,000 pCi/L. Subunits underlain by igneous and metamorphic rocks of the Piedmont Physiographic Province typically have the highest median ground-water radon activities (greater than 1,000 pCi/L); although there is a large variation in radon activities within most of the subunits. Lower median radon activities (between 300 pCi/L and 1,000 pCi/L) were found in ground water in subunits underlain by limestone and dolomite. Of three subunits underlain by sandstone and shale, one fell into each of the three radon-activity classes. The large variability within these subunits may be attributed to the fact that the uranium content of sandstone and shale is related to the uranium content of the sediments from which they formed.

Inventories and mobilization of unsaturated zone sulfate, fluoride, and chloride related to land use change in semiarid regions, southwestern United States and Australia

USGS Publications Warehouse

Scanlon, Bridget R.; Stonestrom, David A.; Reedy, Robert C.; Leaney, Fred W.; Gates, John; Cresswell, Richard G.

2009-01-01

Unsaturated zone salt reservoirs are potentially mobilized by increased groundwater recharge as semiarid lands are cultivated. This study explores the amounts of pore water sulfate and fluoride relative to chloride in unsaturated zone profiles, evaluates their sources, estimates mobilization due to past land use change, and assesses the impacts on groundwater quality. Inventories of water‐extractable chloride, sulfate, and fluoride were determined from borehole samples of soils and sediments collected beneath natural ecosystems (N = 4), nonirrigated (“rain‐fed”) croplands (N = 18), and irrigated croplands (N = 6) in the southwestern United States and in the Murray Basin, Australia. Natural ecosystems contain generally large sulfate inventories (7800–120,000 kg/ha) and lower fluoride inventories (630–3900 kg/ha) relative to chloride inventories (6600–41,000 kg/ha). Order‐of‐magnitude higher chloride concentrations in precipitation and generally longer accumulation times result in much larger chloride inventories in the Murray Basin than in the southwestern United States. Atmospheric deposition during the current dry interglacial climatic regime accounts for most of the measured sulfate in both U.S. and Australian regions. Fluoride inventories are greater than can be accounted for by atmospheric deposition in most cases, suggesting that fluoride may accumulate across glacial/interglacial climatic cycles. Chemical modeling indicates that fluorite controls fluoride mobility and suggests that water‐extractable fluoride may include some fluoride from mineral dissolution. Increased groundwater drainage/recharge following land use change readily mobilized chloride. Sulfate displacement fronts matched or lagged chloride fronts by up to 4 m. In contrast, fluoride mobilization was minimal in all regions. Understanding linkages between salt inventories, increased recharge, and groundwater quality is important for quantifying impacts of anthropogenic activities on groundwater quality and is required for remediating salinity problems.

Vulnerability assessment of groundwater-dependent ecosystems based on integrated groundwater flow modell construction

NASA Astrophysics Data System (ADS)

Tóth, Ádám; Simon, Szilvia; Galsa, Attila; Havril, Timea; Monteiro Santos, Fernando A.; Müller, Imre; Mádl-Szőnyi, Judit

2017-04-01

Groundwater-dependent ecosystems (GDEs) are highly influenced by the amount of groundwater, seasonal variation of precipitation and consequent water table fluctuation and also the anthropogenic activities. They can be regarded as natural surface manifestations of the flowing groundwater. The preservation of environment and biodiversity of these GDEs is an important issue worldwide, however, the water management policy and action plan could not be constructed in absense of proper hydrogeological knowledge. The concept of gravity-driven regional groundwater flow could aid the understanding of flow pattern and interpretation of environmental processes and conditions. Unless the required well data are available, the geological-hydrogeological numerical model of the study area cannot be constructed based only on borehole information. In this case, spatially continuous geophysical data can support groundwater flow model building: systematically combined geophysical methods can provide model input. Integration of lithostratigraphic, electrostratigraphic and hydrostratigraphic information could aid groundwater flow model construction: hydrostratigraphic units and their hydraulic behaviour, boundaries and geometry can be obtained. Groundwater-related natural manifestations, such as GDEs, can be explained with the help of the revealed flow pattern and field mapping of features. Integrated groundwater flow model construction for assessing the vulnerability of GDEs was presented via the case study of the geologically complex area of Tihany Peninsula, Hungary, with the aims of understanding the background and occurrence of groundwater-related environmental phenomena, surface water-groundwater interaction, and revealing the potential effect of anthropogenic activity and climate change. In spite of its important and protected status, fluid flow model of the area, which could support water management and natural protection policy, had not been constructed previously. The 3D groundwater flow model, which was based on the scarce geologic information and the electromagnetic geophysical results, could answer the subsurface hydraulic connection between GDEs. Moreover, the gravity-driven regional groundwater flow concept could help to interpret the hydraulically nested flow systems (local and intermediate). Validation of numerical simulation by natural surface conditions and phenomena was performed. Consequently, the position of wetlands, their vegetation type, discharge features and induced landslides were explained as environmental imprints of groundwater. Anthropogenic activities and climate change have great impact on groundwater. Since the GDEs are fed by local flow systems, the impact of climate change and anthropogenic activities could be notable, therefore the highly vulnerable wetlands have to be in focus of water management and natural conservation policy.

Water availability and use pilot; methods development for a regional assessment of groundwater availability, southwest alluvial basins, Arizona

USGS Publications Warehouse

Tillman, Fred D.; Cordova, Jeffrey T.; Leake, Stanley A.; Thomas, Blakemore E.; Callegary, James B.

2011-01-01

Executive Summary: Arizona is located in an arid to semiarid region in the southwestern United States and is one of the fastest growing States in the country. Population in Arizona surpassed 6.5 million people in 2008, an increase of 140 percent since 1980, when the last regional U.S. Geological Survey (USGS) groundwater study was done as part of the Regional Aquifer System Analysis (RASA) program. The alluvial basins of Arizona are part of the Basin and Range Physiographic Province and cover more than 73,000 mi2, 65 percent of the State's total land area. More than 85 percent of the State's population resides within this area, accounting for more than 95 percent of the State's groundwater use. Groundwater supplies in the area are expected to undergo further stress as an increasing population vies with the State's important agricultural sector for access to these limited resources. To provide updated information to stakeholders addressing issues surrounding limited groundwater supplies and projected increases in groundwater use, the USGS Groundwater Resources Program instituted the Southwest Alluvial Basins Groundwater Availability and Use Pilot Program to evaluate the availability of groundwater resources in the alluvial basins of Arizona. The principal products of this evaluation of groundwater resources are updated groundwater budget information for the study area and a proof-of-concept groundwater-flow model incorporating several interconnected groundwater basins. This effort builds on previous research on the assessment and mapping of groundwater conditions in the alluvial basins of Arizona, also supported by the USGS Groundwater Resources Program. Regional Groundwater Budget: The Southwest Alluvial Basins-Regional Aquifer System Analysis (SWAB-RASA) study produced semiquantitative groundwater budgets for each of the alluvial basins in the SWAB-RASA study area. The pilot program documented in this report developed new quantitative estimates of groundwater budget components using recent (2000-2007) data and methods of data analysis. Estimates of inflow components, including mountain-front recharge, incidental recharge from irrigation of agriculture, managed recharge from recharge facilities, interbasin underflow from upgradient basins, and streamflow losses, are quantified for recent time periods. Mountain-front recharge is the greatest inflow component to the groundwater system and was estimated using two methods: a basin characteristic model and new precipitation information used in a previously developed regression equation. Annual mountain-front recharge for the study area for 1940-2007 estimated by the two methods is 730,000 acre-ft for the basin characteristic model and 643,000 acre-ft for the regression equation, representing 1.5 percent and 1.3 percent of precipitation, respectively. Outflow components, including groundwater withdrawals, evapotranspiration, and interbasin flow to downgradient basins, are also presented for recent time periods. Groundwater withdrawals accounted for the largest share of the water budget, with nearly 2.4 million acre-ft per year withdrawn from the study area in recent years. Evapotranspiration from groundwater was estimated at nearly 1.3 million acre-ft per year for the study area using a newly developed method incorporating vegetation indices from satellite images and land cover information. For water-budget components with temporal variation that could be assessed from available data, estimates for intervening time periods since before development were also developed. An estimate of aquifer storage change, representing both gains to and losses from the groundwater system since before development, was derived for the most developed basins in the study area using available estimates of groundwater-level changes and storage coefficients. An overall storage loss of 74.5 million acre-ft was estimated for these basins within the study area. Demonstration

SUMMARY OF WATERBORNE ILLNESS TRANSMITTED THROUGH CONTAMINATED GROUNDWATER

EPA Science Inventory

The use of contaminated, untreated or inadequately treated groundwater was responsible for 51 percent of all waterborne outbreaks and 40 percent of all waterborne illness reported in the United States during the period 1971-82. Contaminated, untreated or inadequately disinfected ...

California GAMA Program: Ground-Water Quality Data in the Northern San Joaquin Basin Study Unit, 2005

USGS Publications Warehouse

Bennett, George L.; Belitz, Kenneth; Milby Dawson, Barbara J.

2006-01-01

Growing concern over the closure of public-supply wells because of ground-water contamination has led the State Water Board to establish the Ground-Water Ambient Monitoring and Assessment (GAMA) Program. With the aid of the U.S. Geological Survey (USGS) and Lawrence Livermore National Laboratory, the program goals are to enhance understanding and provide a current assessment of ground-water quality in areas where ground water is an important source of drinking water. The Northern San Joaquin Basin GAMA study unit covers an area of approximately 2,079 square miles (mi2) across four hydrologic study areas in the San Joaquin Valley. The four study areas are the California Department of Water Resources (CADWR) defined Tracy subbasin, the CADWR-defined Eastern San Joaquin subbasin, the CADWR-defined Cosumnes subbasin, and the sedimentologically distinct USGS-defined Uplands study area, which includes portions of both the Cosumnes and Eastern San Joaquin subbasins. Seventy ground-water samples were collected from 64 public-supply, irrigation, domestic, and monitoring wells within the Northern San Joaquin Basin GAMA study unit. Thirty-two of these samples were collected in the Eastern San Joaquin Basin study area, 17 in the Tracy Basin study area, 10 in the Cosumnes Basin study area, and 11 in the Uplands Basin study area. Of the 32 samples collected in the Eastern San Joaquin Basin, 6 were collected using a depth-dependent sampling pump. This pump allows for the collection of samples from discrete depths within the pumping well. Two wells were chosen for depth-dependent sampling and three samples were collected at varying depths within each well. Over 350 water-quality field parameters, chemical constituents, and microbial constituents were analyzed and are reported as concentrations and as detection frequencies, by compound classification as well as for individual constituents, for the Northern San Joaquin Basin study unit as a whole and for each individual study area. Results are presented in a descending order based on detection frequencies (most frequently detected compound listed first), or alphabetically when a detection frequency could not be calculated. Only certain wells were measured for all constituents and water-quality parameters. The results of all of the analyses were compared with U.S. Environmental Protection Agency (USEPA) and California Department of Health Services (CADHS) Maximum Contaminant Levels (MCLs), Secondary Maximum Contaminant Levels (SMCLs), USEPA lifetime health advisories (HA-Ls), the risk-specific dose at a cancer risk level equal to 1 in 100,000 or 10E-5 (RSD5), and CADHS notification levels (NLs). When USEPA and CADHS MCLs are the same, detection levels were compared with the USEPA standard; however, in some cases, the CADHS MCL may be lower. In those cases, the data were compared with the CADHS MCL. Constituents listed by CADHS as 'unregulated chemicals for which monitoring is required' were compared with the CADHS 'detection level for the purposes of reporting' (DLR). DLRs unlike MCLs are not health based standards. Instead, they are levels at which current laboratory detection capabilities allow eighty percent of qualified laboratories to achieve measurements within thirty percent of the true concentration. Twenty-three volatile organic compounds (VOCs) and seven gasoline oxygenates were detected in ground-water samples collected in the Northern San Joaquin Basin GAMA study unit. Additionally, 13 tentatively identified compounds were detected. VOCs were most frequently detected in the Eastern San Joaquin Basin study area and least frequently detected in samples collected in the Cosumnes Basin study area. Dichlorodifluoromethane (CFC-12), a CADHS 'unregulated chemical for which monitoring is required,' was detected in two wells at concentrations greater than the DLR. Trihalomethanes were the most frequently detected class of VOC constituents. Chloroform (trichloromethane) was the m

Ground-water flow in the New Jersey Coastal Plain

USGS Publications Warehouse

Martin, Mary

1998-01-01

Ground-water flow in 10 aquifers and 9 intervening confining units of the New Jersey Coastal Plain was simulated as part of the Regional Aquifer System Analysis. Data on aquifer and confining unit characteristics and on pumpage and water levels from 1918 through 1980 were incorporated into a multilayer finite-difference model. The report describes the conceptual hydrogeologic model of the unstressed flow systems, the methods and approach used in simulating flow, and the results of the simulations.

Eolian transport, saline lake basins, and groundwater solutes

USGS Publications Warehouse

Wood, Warren W.; Sanford, Ward E.

1995-01-01

Eolian processes associated with saline lakes are shown to be important in determining solute concentration in groundwater in arid and semiarid areas. Steady state mass balance analyses of chloride in the groundwater at Double Lakes, a saline lake basin in the southern High Plains of Texas, United States, suggest that approximately 4.5 × 105 kg of chloride is removed from the relatively small (4.7 km2) basin floor each year by deflation. This mass enters the groundwater down the wind gradient from the lake, degrading the water quality. The estimates of mass transport were independently determined by evaluation of solutes in the unsaturated zone and by solute mass balance calculations of groundwater flux. Transport of salts from the lake was confirmed over a short term (2 years) by strategically placed dust collectors. Results consistent with those at Double Lake were obtained from dune surfaces collected upwind and downwind from a sabkha near the city of Abu Dhabi in the United Arab Emirates. The eolian transport process provides an explanation of the degraded groundwater quality associated with the 30–40 saline lake basins on the southern half of the southern High Plains of Texas and New Mexico and in many other arid and semiarid areas.

Modelling of sequential groundwater treatment with zero valent iron and granular activated carbon.

PubMed

Bayer, Peter; Finkel, Michael

2005-06-01

Multiple contaminant mixtures in groundwater may not efficiently be treated by a single technology if contaminants possess rather different properties with respect to sorptivity, solubility, and degradation potential. An obvious choice is to use sequenced units of the generally accepted treatment materials zero valent iron (ZVI) and granular activated carbon (GAC). However, as the results of this modelling study suggest, the required dimensions of both reactor units may strongly differ from those expected on the grounds of a contaminant-specific design. This is revealed by performing an analysis for a broad spectrum of design alternatives through numerical experiments for selected patterns of contaminant mixtures consisting of monochlorobenzene, tetrachloroethylene, trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), and vinyl chloride (VC). It is shown that efficient treatment can be achieved only if competitive sorption effects in the GAC unit as well as the formation of intermediate products in the ZVI unit are carefully taken into account. Cost-optimal designs turned out to vary extremely depending on the prevailing conditions concerning contaminant concentrations, branching ratios, and unit costs of both reactor materials. Where VC is the critical contaminant, due to high initial concentration or extensive production as an intermediate, two options are cost-effective: an oversized ZVI unit with an oversized GAC unit or a pure GAC reactor.

Bacterial Community Dynamics in Dichloromethane-Contaminated Groundwater Undergoing Natural Attenuation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, Justin; Kirchner, Veronica; Bernard, William

The uncontrolled release of the industrial solvent methylene chloride, also known as dichloromethane (DCM), has resulted in widespread groundwater contamination in the United States. Here we investigate the role of groundwater bacterial communities in the natural attenuation of DCM at an undisclosed manufacturing site in New Jersey. Here, we investigate the bacterial community structure of groundwater samples differentially contaminated with DCM to better understand the biodegradation potential of these autochthonous bacterial communities. Bacterial community analysis was completed using high-throughput sequencing of the 16S rRNA gene of groundwater samples (n = 26) with DCM contamination ranging from 0.89 to 9,800,000 μg/L.more » Significant DCM concentration-driven shifts in overall bacterial community structure were identified between samples, including an increase in the abundance of Firmicutes within the most contaminated samples. And across all samples, a total of 6,134 unique operational taxonomic units (OTUs) were identified, with 16 taxa having strong correlations with increased DCM concentration. Putative DCM degraders such as Pseudomonas, Dehalobacterium and Desulfovibrio were present within groundwater across all levels of DCM contamination. Interestingly, each of these taxa dominated specific DCM contamination ranges respectively. Potential DCM degrading lineages yet to be cited specifically as a DCM degrading organisms, such as the Desulfosporosinus, thrived within the most heavily contaminated groundwater samples. Co-occurrence network analysis revealed aerobic and anaerobic bacterial taxa with DCM-degrading potential were present at the study site. Our 16S rRNA gene survey serves as the first in situ bacterial community assessment of contaminated groundwater harboring DCM concentrations ranging over seven orders of magnitude. Diversity analyses revealed known as well as potentially novel DCM degrading taxa within defined DCM concentration ranges, indicating niche-specific responses of these autochthonous populations. Altogether, our findings suggest that monitored natural attenuation is an appropriate remediation strategy for DCM contamination, and that high-throughput sequencing technologies are a robust method for assessing the potential role of biodegrading bacterial assemblages in the apparent reduction of DCM concentrations in environmental scenarios.« less

Bacterial Community Dynamics in Dichloromethane-Contaminated Groundwater Undergoing Natural Attenuation

DOE PAGES

Wright, Justin; Kirchner, Veronica; Bernard, William; ...

2017-11-22

The uncontrolled release of the industrial solvent methylene chloride, also known as dichloromethane (DCM), has resulted in widespread groundwater contamination in the United States. Here we investigate the role of groundwater bacterial communities in the natural attenuation of DCM at an undisclosed manufacturing site in New Jersey. Here, we investigate the bacterial community structure of groundwater samples differentially contaminated with DCM to better understand the biodegradation potential of these autochthonous bacterial communities. Bacterial community analysis was completed using high-throughput sequencing of the 16S rRNA gene of groundwater samples (n = 26) with DCM contamination ranging from 0.89 to 9,800,000 μg/L.more » Significant DCM concentration-driven shifts in overall bacterial community structure were identified between samples, including an increase in the abundance of Firmicutes within the most contaminated samples. And across all samples, a total of 6,134 unique operational taxonomic units (OTUs) were identified, with 16 taxa having strong correlations with increased DCM concentration. Putative DCM degraders such as Pseudomonas, Dehalobacterium and Desulfovibrio were present within groundwater across all levels of DCM contamination. Interestingly, each of these taxa dominated specific DCM contamination ranges respectively. Potential DCM degrading lineages yet to be cited specifically as a DCM degrading organisms, such as the Desulfosporosinus, thrived within the most heavily contaminated groundwater samples. Co-occurrence network analysis revealed aerobic and anaerobic bacterial taxa with DCM-degrading potential were present at the study site. Our 16S rRNA gene survey serves as the first in situ bacterial community assessment of contaminated groundwater harboring DCM concentrations ranging over seven orders of magnitude. Diversity analyses revealed known as well as potentially novel DCM degrading taxa within defined DCM concentration ranges, indicating niche-specific responses of these autochthonous populations. Altogether, our findings suggest that monitored natural attenuation is an appropriate remediation strategy for DCM contamination, and that high-throughput sequencing technologies are a robust method for assessing the potential role of biodegrading bacterial assemblages in the apparent reduction of DCM concentrations in environmental scenarios.« less

Lithological and hydrochemical controls on distribution and speciation of uranium in groundwaters of hard-rock granitic aquifers of Madurai District, Tamil Nadu (India).

PubMed

Thivya, C; Chidambaram, S; Keesari, Tirumalesh; Prasanna, M V; Thilagavathi, R; Adithya, V S; Singaraja, C

2016-04-01

Uranium is a radioactive element normally present in hexavalent form as U(VI) in solution and elevated levels in drinking water cause health hazards. Representative groundwater samples were collected from different litho-units in this region and were analyzed for total U and major and minor ions. Results indicate that the highest U concentration (113 µg l(-1)) was found in granitic terrains of this region and about 10 % of the samples exceed the permissible limit for drinking water. Among different species of U in aqueous media, carbonate complexes [UO2(CO3)(2)(2-)] are found to be dominant. Groundwater with higher U has higher pCO2 values, indicating weathering by bicarbonate ions resulting in preferential mobilization of U in groundwater. The major minerals uraninite and coffinite were found to be supersaturated and are likely to control the distribution of U in the study area. Nature of U in groundwater, the effects of lithology on hydrochemistry and factors controlling its distribution in hard rock aquifers of Madurai district are highlighted in this paper.

Groundwater biofilm dynamics grown in situ along a nutrient gradient.

PubMed

Williamson, Wendy M; Close, Murray E; Leonard, Margaret M; Webber, Judith B; Lin, Susan

2012-01-01

This paper describes the in situ response of groundwater biofilms in an alluvial gravel aquifer system on the Canterbury Plains, New Zealand. Biofilms were developed on aquifer gravel, encased in fine mesh bags and suspended in protective columns in monitoring wells for at least 20 weeks. Four sites were selected in the same groundwater system where previous analyses indicated a gradient of increasing nitrate down the hydraulic gradient from Sites 1 to 4. Measurements during the current study classified the groundwater as oligotrophic. Biofilm responses to the nutrient gradients were assessed using bioassays, with biomass determined using protein and cellular and nucleic acid staining and biofilm activity using enzyme assays for lipid, carbohydrate, phosphate metabolism, and cell viability. In general, biofilm activity decreased as nitrate levels increased from Sites 1 to 4, with the opposite relationship for carbon and phosphorus concentrations. These results showed that the groundwater system supported biofilm growth and that the upper catchment supported efficient and productive biofilms (high ratio of activity per unit biomass). © 2012, Institute of Environmental Science & Research Ltd (ESR). Ground Water © 2012, National Ground Water Association.

Preliminary geologic framework developed for a proposed environmental monitoring study of a deep, unconventional Marcellus Shale drill site, Washington County, Pennsylvania

USGS Publications Warehouse

Stamm, Robert G.

2018-06-08

BackgroundIn the fall of 2011, the U.S. Geological Survey (USGS) was afforded an opportunity to participate in an environmental monitoring study of the potential impacts of a deep, unconventional Marcellus Shale hydraulic fracturing site. The drill site of the prospective case study is the “Range Resources MCC Partners L.P. Units 1-5H” location (also referred to as the “RR–MCC” drill site), located in Washington County, southwestern Pennsylvania. Specifically, the USGS was approached to provide a geologic framework that would (1) provide geologic parameters for the proposed area of a localized groundwater circulation model, and (2) provide potential information for the siting of both shallow and deep groundwater monitoring wells located near the drill pad and the deviated drill legs.The lead organization of the prospective case study of the RR–MCC drill site was the Groundwater and Ecosystems Restoration Division (GWERD) of the U.S. Environmental Protection Agency. Aside from the USGS, additional partners/participants were to include the Department of Energy, the Pennsylvania Geological Survey, the Pennsylvania Department of Environmental Protection, and the developer Range Resources LLC. During the initial cooperative phase, GWERD, with input from the participating agencies, drafted a Quality Assurance Project Plan (QAPP) that proposed much of the objectives, tasks, sampling and analytical procedures, and documentation of results.Later in 2012, the proposed cooperative agreement between the aforementioned partners and the associated land owners for a monitoring program at the drill site was not executed. Therefore, the prospective case study of the RR–MCC site was terminated and no installation of groundwater monitoring wells nor the collection of nearby soil, stream sediment, and surface-water samples were made.Prior to the completion of the QAPP and termination of the perspective case study the geologic framework was rapidly conducted and nearly completed. This was done for three principal reasons. First, there was an immediate need to know the distribution of the relatively undisturbed surface to near-surface bedrock geology and unconsolidated materials for the collection of baseline surface data prior to drill site development (drill pad access road, drill pad leveling) and later during monitoring associated with well drilling, well development, and well production. Second, it was necessary to know the bedrock geology to support the siting of: (1) multiple shallow groundwater monitoring wells (possibly as many as four) surrounding and located immediately adjacent to the drill pad, and (2) deep groundwater monitoring wells (possibly two) located at distance from the drill pad with one possibly being sited along one of the deviated production drill legs. Lastly, the framework geology would provide the lateral extent, thickness, lithology, and expected discontinuities of geologic units (to be parsed or grouped as hydrostratigraphic units) and regional structure trends as inputs into the groundwater model.This report provides the methodology of geologic data accumulation and aggregation, and its integration into a geographic information system (GIS) based program. The GIS program will allow multiple data to be exported in various formats (shapefiles [.shp], database files [.dbf], and Keyhole Markup Language files [.KML]) for use in surface and subsurface geologic site characterization, for sampling strategies, and for inputs for groundwater modeling.

Summary of the San Juan structural basin regional aquifer-system analysis, New Mexico, Colorado, Arizona, and Utah

USGS Publications Warehouse

Levings, G.W.; Kernodle, J.M.; Thorn, C.R.

1996-01-01

Ground-water resources are the only source of water in most of the San Juan structural basin and are mainly used for municipal, industrial, domestic, and stock purposes. Industrial use increased dramatically during the late 1970's and early 1980's because of increased exploration and development of uranium and coal resources. The San Juan structural basin is a northwest-trending, asymmetric structural depression at the eastern edge of the Colorado Plateau. The basin contains as much as 14,000 feet of sedimentary rocks overlying a Precambrian basement complex. The sedimentary rocks dip basinward from the basin margins toward the troughlike structural center, or deepest part of the basin. Rocks of Triassic age were selected as the lower boundary for the study. The basin is well defined by structural boundaries in many places with structural relief of as much as 20,000 feet reported. Faulting is prevalent in parts of the basin with displacement of several thousand feet along major faults. The regional aquifers in the basin generally are coincident with the geologic units that have been mapped. Data on the hydrologic properties of the regional aquifers are minimal. Most data were collected on those aquifers associated with uranium and coal resource production. These data are summarized in table format in the report. The regional flow system throughout most of the basin has been affected by the production of oil or gas and subsequent disposal of produced brine. To date more than 26,000 oil- or gas- test holes have been drilled in the basin, the majority penetrating no deeper than the bottom of the Cretaceous rocks. The general water chemistry of the regional aquifers is based on available data. The depositional environments are the major factor controlling the quality of water in the units. The dominant ions are generally sodium, bicarbonate, and sulfate. A detailed geochemical study of three sandstone aquifers--Morrison, Dakota, and Gallup--was undertaken in the northwestern part of the study area. Results of this study indicate that water chemistry changed in individual wells over short periods of time, not expected in a regional flow system. The chemistry of the water is affected by mixing of recharge, ion filtrate, or very dilute ancient water, and by leakage of saline water. The entire system of ground-water flow and its controlling factors has been defined as the conceptual model. A steady-state, three-dimensional ground-water flow model was constructed to simulate modern predevelopment flow in the post-Jurassic rocks of the regional flow system. In the ground-water flow model, 14 geologic units or combinations of geologic units were considered to be regional aquifers, and 5 geologic units or combinations of geologic units were considered to be regional confining units. The model simulated flow in 12 layers (hydrostratigraphic units) and used harmonic-mean vertical leakance to indirectly simulate aquifer connection across 3 other hydrostratigraphic confining units in addition to coupling the 12 units.

First status report on regional ground-water flow modeling for the Paradox Basin, Utah

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, R.W.

1984-05-01

Regional ground-water flow within the principal hydrogeologic units of the Paradox Basin is evaluated by developing a conceptual model of the flow regime in the shallow aquifers and the deep-basin brine aquifers and testing these models using a three-dimensional, finite-difference flow code. Semiquantitative sensitivity analysis (a limited parametric study) is conducted to define the system response to changes in hydrologic properties or boundary conditions. A direct method for sensitivity analysis using an adjoint form of the flow equation is applied to the conceptualized flow regime in the Leadville limestone aquifer. All steps leading to the final results and conclusions aremore » incorporated in this report. The available data utilized in this study is summarized. The specific conceptual models, defining the areal and vertical averaging of litho-logic units, aquifer properties, fluid properties, and hydrologic boundary conditions, are described in detail. Two models were evaluated in this study: a regional model encompassing the hydrogeologic units above and below the Paradox Formation/Hermosa Group and a refined scale model which incorporated only the post Paradox strata. The results are delineated by the simulated potentiometric surfaces and tables summarizing areal and vertical boundary fluxes, Darcy velocities at specific points, and ground-water travel paths. Results from the adjoint sensitivity analysis include importance functions and sensitivity coefficients, using heads or the average Darcy velocities to represent system response. The reported work is the first stage of an ongoing evaluation of the Gibson Dome area within the Paradox Basin as a potential repository for high-level radioactive wastes.« less

Numerical Analysis of Ground-Water Flow and Salinity in the Ewa Area, Oahu, Hawaii

USGS Publications Warehouse

Oki, Delwyn S.; Souza, William R.; Bolke, Edward I.; Bauer, Glenn R.

1996-01-01

The coastal plain in the Ewa area of southwestern Oahu, Hawaii, is part of a larger, nearly continuous sedimentary coastal plain along Oahu's southern coast. The coastal sediments are collectively known as caprock because they impede the free discharge of ground water from the underlying volcanic aquifers. The caprock is a layered sedimentary system consisting of interbedded marine and terrestrial sediments of both high and low permeability. Before sugarcane cultivation ended in late 1994, shallow ground water from the upper limestone unit, which is about 60 to 200 feet thick, was used primarily for irrigation of sugarcane. A cross-sectional ground-water flow and transport model was used to evaluate the hydrogeologic controls on the regional flow system in the Ewa area. Controls considered were: (1) overall caprock hydraulic conductivity, (2) stratigraphic variations of hydraulic conductivity in the caprock, and (3) recharge. In addition, the effects of a marina excavation were evaluated. Within the caprock, variations in hydraulic conductivity, caused by caprock stratigraphy or discontinuities of the stratigraphic units, are a major control on the direction of ground-water flow and the distribution of water levels and salinity. Model results also show that a reduction of recharge will result in increased salinity throughout the caprock with the greatest change in the upper limestone layer. In addition, the model indicates that excavation of an ocean marina will lower water levels in the upper limestone layer. Results of cross-sectional modeling confirm the general ground-water flow pattern that would be expected in the layered sedimentary system in the Ewa caprock. Ground-water flow is: (1) predominantly upward in the low-permeability sedimentary units, and (2) predominantly horizontal in the high-permeability sedimentary units.

Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley

USGS Publications Warehouse

Scanlon, Bridget R.; Faunt, Claudia; Longuevergne, Laurent; Reedy, Robert C.; Alley, William M.; McGuire, Virginia L.; McMahon, Peter B.

2012-01-01

Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion occurring in 4% of the High Plains land area. Extrapolation of the current depletion rate suggests that 35% of the southern High Plains will be unable to support irrigation within the next 30 y. Reducing irrigation withdrawals could extend the lifespan of the aquifer but would not result in sustainable management of this fossil groundwater. The Central Valley is a more dynamic, engineered system, with north/south diversions of surface water since the 1950s contributing to ∼7× higher recharge. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion since the 1960s, totaling 80 km3, occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess surface water in aquifers by up to 3 km3 shows promise for coping with droughts and improving sustainability of groundwater resources in the Central Valley.

Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley

USGS Publications Warehouse

Scanlon, Bridget R.; Faunt, Claudia C.; Longuevergne, Laurent; Reedy, Robert C.; Alley, William M.; McGuire, Virginia L.; McMahon, Peter B.

2012-01-01

Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ~50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion occurring in 4% of the High Plains land area. Extrapolation of the current depletion rate suggests that 35% of the southern High Plains will be unable to support irrigation within the next 30 y. Reducing irrigation withdrawals could extend the lifespan of the aquifer but would not result in sustainable management of this fossil groundwater. The Central Valley is a more dynamic, engineered system, with north/south diversions of surface water since the 1950s contributing to ~7× higher recharge. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion since the 1960s, totaling 80 km3, occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess surface water in aquifers by up to 3 km3 shows promise for coping with droughts and improving sustainability of groundwater resources in the Central Valley.

Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley

PubMed Central

Scanlon, Bridget R.; Faunt, Claudia C.; Longuevergne, Laurent; Reedy, Robert C.; Alley, William M.; McGuire, Virginia L.; McMahon, Peter B.

2012-01-01

Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion occurring in 4% of the High Plains land area. Extrapolation of the current depletion rate suggests that 35% of the southern High Plains will be unable to support irrigation within the next 30 y. Reducing irrigation withdrawals could extend the lifespan of the aquifer but would not result in sustainable management of this fossil groundwater. The Central Valley is a more dynamic, engineered system, with north/south diversions of surface water since the 1950s contributing to ∼7× higher recharge. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion since the 1960s, totaling 80 km3, occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess surface water in aquifers by up to 3 km3 shows promise for coping with droughts and improving sustainability of groundwater resources in the Central Valley. PMID:22645352

Shallow ground-water quality adjacent to burley tobacco fields in northeastern Tennessee and southwestern Virginia, spring 1997

USGS Publications Warehouse

Johnson, G.C.; Connell, J.F.

2001-01-01

In 1994, the U.S. Geological Survey began an assessment of the upper Tennessee River Basin as part of the National Water-Quality Assessment (NAWQA) Program. A ground-water land-use study conducted in 1996 focused on areas with burley tobacco production in northeastern Tennessee and southwestern Virginia. Land-use studies are designed to focus on specific land uses and to examine natural and human factors that affect the quality of shallow ground water underlying specific types of land use. Thirty wells were drilled in shallow regolith adjacent to and downgradient of tobacco fields in the Valley and Ridge Physiographic Province of the upper Tennessee River Basin. Ground-water samples were collected between June 4 and July 9, 1997, to coincide with the application of the majority of pesticides and fertilizers used in tobacco production. Ground-water samples were analyzed for nutrients, major ions, 79 pesticides, 7 pesticide degradation products, 86 volatile organic compounds, and dissolved organic carbon. Nutrient concentrations were lower than the levels found in similar NAWQA studies across the United States during 1993-95. Five of 30 upper Tennessee River Basin wells (16.7 percent) had nitrate levels exceeding 10 mg/L while 19 percent of agricultural land-use wells nationally and 7.9 percent in the Southeast had nitrate concentrations exceeding 10 mg/L. Median nutrient concentrations were equal to or less than national median concentrations. All pesticide concentrations in the basin were less than established drinking water standards, and pesticides were detected less frequently than average for other NAWQA study units. Atrazine was detected at 8 of 30 (27 percent) of the wells, and deethylatrazine (an atrazine degradation product) was found in 9 (30 percent) of the wells. Metalaxyl was found in 17 percent of the wells, and prometon, flumetralin, dimethomorph, 2,4,5-T, 2,4-D, dichlorprop, and silvex were detected once each (3 percent). Volatile organic compounds were detected in 27 of 30 wells. Although none of the volatile organic compound concentrations exceeded drinking water standards, the detection frequency was higher than the average for the other NAWQA study units.

Trace elements and radon in groundwater across the United States, 1992-2003

USGS Publications Warehouse

Ayotte, Joseph D.; Gronberg, Jo Ann M.; Apodaca, Lori E.

2011-01-01

Trace-element concentrations in groundwater were evaluated for samples collected between 1992 and 2003 from aquifers across the United States as part of the U.S. Geological Survey National Water-Quality Assessment Program. This study describes the first comprehensive analysis of those data by assessing occurrence (concentrations above analytical reporting levels) and by comparing concentrations to human-health benchmarks (HHBs). Data from 5,183 monitoring and drinking-water wells representing more than 40 principal and other aquifers in humid and dry regions and in various land-use settings were used in the analysis. Trace elements measured include aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Tl), uranium (U), vanadium (V), and zinc (Zn). Radon (Rn) gas also was measured and is included in the data analysis. Climate influenced the occurrence and distribution of trace elements in groundwater whereby more trace elements occurred and were found at greater concentrations in wells in drier regions of the United States than in humid regions. In particular, the concentrations of As, Ba, B, Cr, Cu, Mo, Ni, Se, Sr, U, V, and Zn were greater in the drier regions, where processes such as chemical evolution, ion complexation, evaporative concentration, and redox (oxidation-reduction) controls act to varying degrees to mobilize these elements. Al, Co, Fe, Pb, and Mn concentrations in groundwater were greater in humid regions of the United States than in dry regions, partly in response to lower groundwater pH and (or) more frequent anoxic conditions. In groundwater from humid regions, concentrations of Cu, Pb, Rn, and Zn were significantly greater in drinking-water wells than in monitoring wells. Samples from drinking-water wells in dry regions had greater concentrations of As, Ba, Pb, Li, Sr, V, and Zn, than samples from monitoring wells. In humid regions, however, concentrations of most trace elements were greater in monitoring wells than in drinking-water wells; the exceptions were Cu, Pb, Zn, and Rn. Cu, Pb, and Zn are common trace elements in pumps and pipes used in the construction of drinking-water wells, and contamination from these sources may have contributed to their concentrations. Al, Sb, Ba, B, Cr, Co, Fe, Mn, Mo, Ni, Se, Sr, and U concentrations were all greater in monitoring wells than in drinking-water wells in humid regions. Groundwater from wells in agricultural settings had greater concentrations of As, Mo, and U than groundwater from wells in urban settings, possibly owing to greater pH in the agricultural wells. Significantly greater concentrations of B, Cr, Se, Ag, Sr, and V also were found in agricultural wells in dry regions. Groundwater from dry-region urban wells had greater concentrations of Co, Fe, Pb, Li, Mn, and specific conductance than groundwater from agricultural wells. The geologic composition of aquifers and aquifer geochemistry are among the major factors affecting trace-element occurrence. Trace-element concentrations in groundwater were characterized in aquifers from eight major groups based on geologic material, including (1) unconsolidated sand and gravel; (2) glacial unconsolidated sand and gravel; (3) semiconsolidated sand; (4) sandstone; (5) sandstone and carbonate rock; (6) carbonate rock; (7) basaltic and other volcanic rock; and (8) crystalline rock. The majority of groundwater samples and the largest percentages of exceedences of HHBs were in the glacial and nonglacial unconsolidated sand and gravel aquifers; in these aquifers, As, Mn, and U are the most common trace elements exceeding HHBs. Overall, 19 percent of wells (962 of 5,097) exceeded an HHB for at least one trace element. The trace elements with HHBs included in this summary were Sb, As, Ba, Be, B, Cd, Cr,

Geospatial database of estimates of groundwater discharge to streams in the Upper Colorado River Basin

USGS Publications Warehouse

Garcia, Adriana; Masbruch, Melissa D.; Susong, David D.

2014-01-01

The U.S. Geological Survey, as part of the Department of the Interior’s WaterSMART (Sustain and Manage America’s Resources for Tomorrow) initiative, compiled published estimates of groundwater discharge to streams in the Upper Colorado River Basin as a geospatial database. For the purpose of this report, groundwater discharge to streams is the baseflow portion of streamflow that includes contributions of groundwater from various flow paths. Reported estimates of groundwater discharge were assigned as attributes to stream reaches derived from the high-resolution National Hydrography Dataset. A total of 235 estimates of groundwater discharge to streams were compiled and included in the dataset. Feature class attributes of the geospatial database include groundwater discharge (acre-feet per year), method of estimation, citation abbreviation, defined reach, and 8-digit hydrologic unit code(s). Baseflow index (BFI) estimates of groundwater discharge were calculated using an existing streamflow characteristics dataset and were included as an attribute in the geospatial database. A comparison of the BFI estimates to the compiled estimates of groundwater discharge found that the BFI estimates were greater than the reported groundwater discharge estimates.

Nevada National Security Site Groundwater Program

ScienceCinema

None

2018-01-16

From 1951 to 1992, the Unites States government conducted 828 underground nuclear tests at the Nevada National Security Site. About one-third of these tests occurred near, below or within the water table - the very top portion of the groundwater layer where rock and soil are completely saturated with water. As a result, some groundwater was contaminated. The U.S. Department of Energy (DOE) began exploring the effects of groundwater contamination in the 1970s. Though contamination from underground testing has never been detected on public land, the DOE was committed to developing an advanced, reliable monitoring network that ensures the long-term protection of the public. An intensive groundwater investigation program was launched in 1989.

Ground-Water Quality Data in the Kern County Subbasin Study Unit, 2006 - Results from the California GAMA Program

USGS Publications Warehouse

Shelton, Jennifer L.; Pimentel, Isabel; Fram, Miranda S.; Belitz, Kenneth

2008-01-01

Ground-water quality in the approximately 3,000 square-mile Kern County Subbasin study unit (KERN) was investigated from January to March, 2006, as part of the Priority Basin Assessment Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The GAMA Priority Basin Assessment project was developed in response to the Groundwater Quality Monitoring Act of 2001, and is being conducted by the California State Water Resources Control Board (SWRCB) in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory (LLNL). The Kern County Subbasin study was designed to provide a spatially unbiased assessment of raw (untreated) ground-water quality within KERN, as well as a statistically consistent basis for comparing water quality throughout California. Samples were collected from 50 wells within the San Joaquin Valley portion of Kern County. Forty-seven of the wells were selected using a randomized grid-based method to provide a statistical representation of the ground-water resources within the study unit. Three additional wells were sampled to aid in the evaluation of changes in water chemistry along regional ground-water flow paths. The ground-water samples were analyzed for a large number of man-made organic constituents (volatile organic compounds [VOCs], pesticides, and pesticide degradates), constituents of special interest (perchlorate, N-nitrosodimethylamine [NDMA], and 1,2,3-trichloropropane [1,2,3-TCP]), naturally occurring inorganic constituents (nutrients, major and minor ions, and trace elements), radioactive constituents, and microbial indicators. Naturally occurring isotopes (tritium, carbon-14, and stable isotopes of hydrogen, oxygen, nitrogen, and carbon) and dissolved noble gases also were measured to help identify the source and age of the sampled ground water. Quality-control samples (blanks, replicates, and laboratory matrix spikes) were collected and analyzed at approximately 10 percent of the wells, and the results for these samples were used to evaluate the quality of the data from the ground-water samples. Assessment of the quality-control information resulted in censoring of less than 0.4 percent of the data collected for ground-water samples. This study did not attempt to evaluate the quality of water delivered to consumers; after withdrawal from the ground, raw ground water typically is treated, disinfected, or blended with other waters to maintain acceptable water quality. Regulatory thresholds apply, not to the raw ground water, but to treated water that is served to the consumer. However, to provide some context for the results, concentrations of constituents measured in the raw ground water were compared with health-based thresholds established by the U.S. Environmental Protection Agency (USEPA) and the California Department of Public Health (CDPH), and as well as with thresholds established for aesthetic concerns (secondary maximum contaminant levels, SMCL-CA) by CDPH. VOCs and pesticides each were detected in approximately 60 percent of the grid wells, and detections of all compounds but one were below health-based thresholds. The fumigant, 1,2-dibromo-3-chloropropane (DBCP), was detected above the USEPA maximum contaminant level (MCL-US) in one sample. Detections of most inorganic constituents were also below health-based thresholds. Constituents detected above health-based thresholds include: nitrate, (MCL-US, 2 samples), arsenic (MCL-US, 2 samples), and vanadium (California notification level, NL-CA, 1 sample). All detections of radioactive constituents were below health-based thresholds, although nine samples had activities of radon-222 above the lower proposed MCL-US. Most of the samples from KERN wells had concentrations of major elements, total dissolved solids, and trace elements below the non-enforceable thresholds set for aesthetic concerns.

Nitrate in aquifers beneath agricultural systems

USGS Publications Warehouse

Burkart, M.R.; Stoner, J.D.; ,

2007-01-01

Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as in Asia, may experience the greatest impact of this practice on groundwater nitrate. ?? USDA 2007.

Groundwater quality in the Indian Wells Valley, California

USGS Publications Warehouse

Dawson, Barbara J. Milby; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Indian Wells Valley is one of the study areas being evaluated. The Indian Wells study area is approximately 600 square miles (1,554 square kilometers) and includes the Indian Wells Valley groundwater basin (California Department of Water Resources, 2003). Indian Wells Valley has an arid climate and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). The study area has internal drainage, with runoff from the surrounding mountains draining towards dry lake beds in the lower parts of the valley. Land use in the study area is approximately 97.0 percent (%) natural, 0.4% agricultural, and 2.6% urban. The primary natural land cover is shrubland. The largest urban area is the city of Ridgecrest (2010 population of 28,000). Groundwater in this basin is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from the Sierra Nevada to the west and from the other surrounding mountains. Recharge to the groundwater system is primarily runoff from the Sierra Nevada and to the west and from the other surrounding mountains. Recharge to the groundwater system is primarily runoff from the Sierra Nevada and direct infiltration from irrigation and septic systems. The primary sources of discharge are pumping wells and evapotranspiration near the dry lakebeds. The primary aquifers in the Indian Wells study area are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in Indian Wells Valley are completed to depths between 240 and 800 feet (73 to 244 meters), consist of solid casing from the land surface to a depth of 180 to 260 feet (55 to 79 meters), and are screened or perforated below the solid casing.

Prediction of groundwater flowing well zone at An-Najif Province, central Iraq using evidential belief functions model and GIS.

PubMed

Al-Abadi, Alaa M; Pradhan, Biswajeet; Shahid, Shamsuddin

2015-10-01

The objective of this study is to delineate groundwater flowing well zone potential in An-Najif Province of Iraq in a data-driven evidential belief function model developed in a geographical information system (GIS) environment. An inventory map of 68 groundwater flowing wells was prepared through field survey. Seventy percent or 43 wells were used for training the evidential belief functions model and the reset 30 % or 19 wells were used for validation of the model. Seven groundwater conditioning factors mostly derived from RS were used, namely elevation, slope angle, curvature, topographic wetness index, stream power index, lithological units, and distance to the Euphrates River in this study. The relationship between training flowing well locations and the conditioning factors were investigated using evidential belief functions technique in a GIS environment. The integrated belief values were classified into five categories using natural break classification scheme to predict spatial zoning of groundwater flowing well, namely very low (0.17-0.34), low (0.34-0.46), moderate (0.46-0.58), high (0.58-0.80), and very high (0.80-0.99). The results show that very low and low zones cover 72 % (19,282 km(2)) of the study area mostly clustered in the central part, the moderate zone concentrated in the west part covers 13 % (3481 km(2)), and the high and very high zones extended over the northern part cover 15 % (3977 km(2)) of the study area. The vast spatial extension of very low and low zones indicates that groundwater flowing wells potential in the study area is low. The performance of the evidential belief functions spatial model was validated using the receiver operating characteristic curve. A success rate of 0.95 and a prediction rate of 0.94 were estimated from the area under relative operating characteristics curves, which indicate that the developed model has excellent capability to predict groundwater flowing well zones. The produced map of groundwater flowing well zones could be used to identify new wells and manage groundwater storage in a sustainable manner.

Implementation of magnetic, gravity and resistivity data in identifying groundwater occurrences in El Qaa Plain area, Southern Sinai, Egypt

NASA Astrophysics Data System (ADS)

Selim, El Sayed; Abdel-Raouf, Osama; Mesalam, Mohamed

2016-10-01

El Qaa plain is one of the areas that have been proved to be promising as to its soil and groundwater resources in the southwestern part of Sinai. This study was carried out to study the lateral and vertical variations in the subsurface lithologic properties in El Qaa plain area and delineating the subsurface structure that affecting El Qaa plain depression. Gravity, magnetic data, fifty-one (51) vertical electrical sounding (Ves's) and Digital Elevation Model (DEM) map were used. Two-dimensional density modeling, analytical signal, tilt derivatives, Euler deconvolution techniques and interpretation of the resistivity data were applied on potential data. This study concluded that, El Qaa plain is a NE-SW depression confined by two normal faults and subdivided into five sedimentary units. Rock fragments and boulders derived to the plain from the surrounding highlands are the main components of the first surface unit that characterized by high resistivity values. This layer is overly another unit composed of gravelly sand with thickness ranging between 10 and 140 m. The third unit is composed mainly of sand with intercalations of clay with thickness ranging from 2 to 152 m. A Reefal limestone unit is a fourth unit interpreted from this study. The fifth unit is composed of clay. The water bearing formations in El Qaa Plain area are located principally in the second and the third layers. Finally, the depth to the basement surface ranges from 400 m to more than 1.5 km below sea level. Also, there are many minor structural trends interpreted from this study and affecting the El Qaa plain are striking in N-S, E-W and NE-SW directions.

Groundwater chemistry near an impoundment for produced water, Powder River Basin, Wyoming, USA

USGS Publications Warehouse

Healy, R.W.; Bartos, T.T.; Rice, C.A.; McKinley, M.P.; Smith, B.D.

2011-01-01

The Powder River Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of the large amounts of groundwater extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and water chemistry at one impoundment, Skewed Reservoir, has produced the most detailed data set for any impoundment in the Basin. Data were collected from a network of 21 observation wells and three suction lysimeters. A groundwater mound formed atop bedrock within initially unsaturated, unconsolidated deposits underlying the reservoir. Heterogeneity in physical and chemical properties of sediments resulted in complex groundwater flow paths and highly variable groundwater chemistry. Sulfate, bicarbonate, sodium, and magnesium were the dominant ions in all areas, but substantial variability existed in relative concentrations; pH varied from less than 3 to more than 9, and total dissolved solids concentrations ranged from less than 5000 to greater than 100,000 mg/L. Selenium was a useful tracer of reservoir water; selenium concentrations exceeded 300 μg/L in samples obtained from 18 of the 24 sampling points. Groundwater travel time from the reservoir to a nearby alluvial aquifer (a linear distance of 177 m) was calculated at 474 days on the basis of selenium concentrations. The produced water is not the primary source of solutes in the groundwater. Naturally occurring salts and minerals within the unsaturated zone, dissolved and mobilized by infiltrating impoundment water, account for most of the solute mass in groundwater. Gypsum dissolution, cation-exchange, and pyrite oxidation appear to be important reactions. The complex geochemistry and groundwater flow paths at the study site underscore the difficulty in assessing effects of surface impoundments on water resources within the Powder River Basin.

Groundwater quality in the Antelope Valley, California

USGS Publications Warehouse

Dawson, Barbara J. Milby; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Antelope Valley is one of the study areas being evaluated. The Antelope study area is approximately 1,600 square miles (4,144 square kilometers) and includes the Antelope Valley groundwater basin (California Department of Water Resources, 2003). Antelope Valley has an arid climate and is part of the Mojave Desert. Average annual rainfall is about 6 inches (15 centimeters). The study area has internal drainage, with runoff from the surrounding mountains draining towards dry lakebeds in the lower parts of the valley. Land use in the study area is approximately 68 percent (%) natural (mostly shrubland and grassland), 24% agricultural, and 8% urban. The primary crops are pasture and hay. The largest urban areas are the cities of Palmdale and Lancaster (2010 populations of 152,000 and 156,000, respectively). Groundwater in this basin is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from surrounding mountains. The primary aquifers in Antelope Valley are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in Antelope Valley are completed to depths between 360 and 700 feet (110 to 213 meters), consist of solid casing from the land surface to a depth of 180 to 350 feet (55 to 107 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the surrounding mountains, and by direct infiltration of irrigation and sewer and septic systems. The primary sources of discharge are pumping wells and evapotranspiration near the dry lakebeds.

Groundwater quality in Coachella Valley, California

USGS Publications Warehouse

Dawson, Barbara J. Milby; Belitz, Kenneth

2012-01-01

Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and increases public access to groundwater-quality information. Coachella Valley is one of the study areas being evaluated. The Coachella study area is approximately 820 square miles (2,124 square kilometers) and includes the Coachella Valley groundwater basin (California Department of Water Resources, 2003). Coachella Valley has an arid climate, with average annual rainfall of about 6 inches (15 centimeters). The runoff from the surrounding mountains drains to rivers that flow east and south out of the study area to the Salton Sea. Land use in the study area is approximately 67 percent (%) natural, 21% agricultural, and 12% urban. The primary natural land cover is shrubland. The largest urban areas are the cities of Indio and Palm Springs (2010 populations of 76,000 and 44,000, respectively). Groundwater in this basin is used for public and domestic water supply and for irrigation. The main water-bearing units are gravel, sand, silt, and clay derived from surrounding mountains. The primary aquifers in Coachella Valley are defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health database. Public-supply wells in Coachella Valley are completed to depths between 490 and 900 feet (149 to 274 meters), consist of solid casing from the land surface to a depth of 260 to 510 feet (79 to 155 meters), and are screened or perforated below the solid casing. Recharge to the groundwater system is primarily runoff from the surrounding mountains, and by direct infiltration of irrigation. The primary sources of discharge are pumping wells, evapotranspiration, and underflow to the Salton Sea and Imperial Valley areas.

Simulating nitrate response functions in watersheds: Case studies in the United States and New Zealand

NASA Astrophysics Data System (ADS)

Gusyev, Maksym; Abrams, Daniel; Morgenstern, Uwe; Stewart, Michael

2016-04-01

Non-point sources of nitrate contamination are a common concern in different parts of the world and are difficult to characterize. Due to the solubility of nitrate, it easily enters groundwater and may take years or decades to completely flush to a stream. During this time, it may undergo denitrification, in particular if dissolved oxygen levels are low, requiring a representation of spatially distributed nitrate input as well as detailed hydrogeology. In this presentation, nitrate response functions are generated with four different methodologies that are listed in the order of decreasing degrees of freedom: groundwater flow and chemical transport (MODFLOW/MT3D), groundwater flow with solute particle tracing (MODFLOW/MODPATH), cross-sectional groundwater flow model (MODFLOW), and lumped parameter models (LPMs). We tested these approaches in selected watersheds in the Eastern and Midwestern United States as well as New Zealand and found similar nitrate results in all cases despite different model complexities. It is noted that only the fully three dimensional MODFLOW models with MT3D or MODPATH could account for detailed patterns of land use and nitrate applications; the cross-sectional models and lumped parameter models could only do so approximately. Denitrification at depth could also be explicitly accounted for in all four approaches, although this was not a major factor in any of the watersheds investigated.

Ground-Water Flow, 2004-07, and Water Quality, 1992-2007, in McBaine Bottoms, Columbia, Missouri

USGS Publications Warehouse

Smith, Brenda Joyce; Richards, Joseph M.

2008-01-01

The U.S. Geological Survey, in cooperation with the city of Columbia, Missouri, and the Missouri Department of Conservation, collected ground-water quality data, surface-water quality data, and water-level data in McBaine Bottoms, southwest of Columbia. McBaine Bottoms, adjacent to the Missouri River, is the location of the municipal-supply well field for the city of Columbia, the city of Columbia wastewater-treatment wetlands, and the Missouri Department of Conservation Eagle Bluffs Conservation Area. This report describes the ground-water flow and water quality of McBaine Bottoms and provides information to better understand the interaction between treated effluent from the wetlands used on the Eagle Bluffs Conservation Area and the water in the alluvial aquifer that is pumped from the city of Columbia municipal-supply well field. Changes in major chemical constituent concentrations have been detected at several sampling sites between pre- and post-effluent application data. Analysis of post-effluent data indicates substantial changes in calcium, potassium, sodium, chloride, and sulfate concentrations in ground water. These changes became apparent shortly after the beginning of the operation of the wastewater-treatment wetland in 1994 and the formation of the Eagle Bluffs Conservation Area, which uses the treated effluent as a water source for the management of migratory water fowl. The changes have continued throughout the 15 years of sample collection. The concentrations of these major chemical constituents are on the mixing continuum between pre-effluent ground water as one end member and the treated wastewater effluent as the other end member. For monitoring wells that had changes in major chemical constituent concentrations, the relative percentage of treated effluent in the ground water, assuming chloride is conservative, ranged from 6 to 88 percent. Twenty-two monitoring wells throughout McBaine Bottoms have been affected by effluent based on chloride concentrations larger than 40 milligrams per liter. The chloride concentration of ground water in the alluvial aquifer reflects several sources, including precipitation, water from the Missouri River, water in the aquifer, and the treated effluent. Chloride concentrations from precipitation, the Missouri River, and water in the alluvial aquifer were less than 40 milligrams per liter. These monitoring wells affected by effluent are located in two general areas - adjacent to treatment wetland unit 1 and near the ground-water high on and north of the Eagle Bluffs Conservation Area. The probable source of the large chloride concentrations in well samples adjacent to treatment wetland unit 1 is leakage from the unit. The source for the large chloride concentrations in the other monitoring well samples is the effluent mixed with ground water and Missouri River water that is used to fill pools on the Eagle Bluffs Conservation Area. One monitoring well had a single sample with a chloride concentration larger than 40 milligrams per liter. That sample may have been affected by the use of road salt because of the presence of ice and snow immediately before the sample was collected. Lateral ground-water flow was dominated by the presence of a persistent ground-water high beneath the Eagle Bluffs Conservation Area and the presence of a cone of depression centered around the city of Columbia well field in the northern part of the study area. Ground-water flow was radially away from the apex of the ground-water high; west and south of the high, flow was toward the Missouri River, east of the high, flow was toward Perche Creek, and north of the high, flow was to the north toward the cone of depression around the city of Columbia well field. Another permanent feature on the water-level maps was a ground-water high beneath treatment wetland unit 1. Although the ground-water high was present throughout the study period, the subsurface expression of the high changed depending on hydrolo

Hydrologic and geochemical data collected near Skewed Reservoir, an impoundment for coal-bed natural gas produced water, Powder River Basin, Wyoming

USGS Publications Warehouse

Healy, Richard W.; Rice, Cynthia A.; Bartos, Timothy T.

2012-01-01

The Powder River Structural Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of groundwater that is extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and subsurface water and soil chemistry was conducted at one such impoundment, Skewed Reservoir. Hydrologic and geochemical data collected as part of that study are contained herein. Data include chemistry of groundwater obtained from a network of 21 monitoring wells and three suction lysimeters and chemical and physical properties of soil cores including chemistry of water/soil extracts, particle-size analyses, mineralogy, cation-exchange capacity, soil-water content, and total carbon and nitrogen content of soils.

Preliminary remedial action objectives for the Tank 16 groundwater operable unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miles, W.C. Jr.

1992-10-28

Tank 16 is a High Level Radioactive Waste tank in the H-Area Tank Farm on the Savannah River Site that was placed into service in May 1959. A leak was detected in one of the construction weld joints while the tank was being filled. Before jet evacuation of the tank waste was completed, the leak overflowed the annulus pan and an estimated 16 to 700 gallons of waste escaped to the environment (soil and groundwater) over a six hour period contaminating approximately 1,600--70,000 cubic feet of soil with up to 5000 curies of activity (principally Cs[sup 137]). The Tank 16more » bottom is constructed below the groundwater table which resulted in almost immediate contamination of that medium. Low groundwater flow rates, the ion exchange property of adjacent soils, and the distance to the nearest surface water bodies (1,500 to 8,000 feet) indicates that surface water and sediment outcrop of contaminates may be expected between 44 and 530 years (Poe et al., 1974). Remedial action objectives consist of medium-specific and operable unit specific goals for protecting human health and the environment. These objectives are specific and do not limit the range of alternatives that may be developed.A range of remedial technologies, which provides for treatment, containment, and removal requirements of contaminated media remaining at the Tank 16 groundwater operable unit, is identified and developed for each general response action.« less

Preliminary remedial action objectives for the Tank 16 groundwater operable unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miles, W.C. Jr.

1992-10-28

Tank 16 is a High Level Radioactive Waste tank in the H-Area Tank Farm on the Savannah River Site that was placed into service in May 1959. A leak was detected in one of the construction weld joints while the tank was being filled. Before jet evacuation of the tank waste was completed, the leak overflowed the annulus pan and an estimated 16 to 700 gallons of waste escaped to the environment (soil and groundwater) over a six hour period contaminating approximately 1,600--70,000 cubic feet of soil with up to 5000 curies of activity (principally Cs{sup 137}). The Tank 16more » bottom is constructed below the groundwater table which resulted in almost immediate contamination of that medium. Low groundwater flow rates, the ion exchange property of adjacent soils, and the distance to the nearest surface water bodies (1,500 to 8,000 feet) indicates that surface water and sediment outcrop of contaminates may be expected between 44 and 530 years (Poe et al., 1974). Remedial action objectives consist of medium-specific and operable unit specific goals for protecting human health and the environment. These objectives are specific and do not limit the range of alternatives that may be developed.A range of remedial technologies, which provides for treatment, containment, and removal requirements of contaminated media remaining at the Tank 16 groundwater operable unit, is identified and developed for each general response action.« less

Geology and ground-water resources of the Lawrenceville area, Georgia

USGS Publications Warehouse

Chapman, Melinda J.; Crawford, Thomas J.; Tharpe, W. Todd

1999-01-01

The population of the Atlanta Metropolitan area continues to grow at a rapid pace and the demand for water supplies steadily increases. Exploration for ground-water resources, as a supplement to surface-water supplies, is being undertaken by many city and county governments. The application of effective investigative methods to characterization of the complex igneous and metamorphic fractured bedrock aquifers of the Piedmont physiographic province is essential to the success of these ground-water exploration programs. The U.S. Geological Survey, in cooperation with the City of Lawrenceville, Ga., began a study in December 1994 to apply various investigative techniques for field characterization of fractured crystalline-bedrock aquifers near Lawrenceville. Five major lithologic units were mapped in the Lawrenceville, Ga., area as part of an ongoing study of ground-water resources-amphibolite, biotite gneiss, button schist, granite gneiss, and quartzite/aluminous schist. These units generally are thin in outcrop width, have low angles of dip (nearly 0 to 20 degrees, dip reversals occur over short distances), and exhibit some shearing characteristics. The most productive unit for ground-water resources, on the basis of subsurface data collected through 1997, is the amphibolite. Historically, two wells drilled into this unit are recognized as having possibly the highest yields in the Piedmont region of northern Georgia. The City of Lawrenceville refurbished one well at the Rhodes Jordan Wellfield in 1990, and has pumped this well at an average rate of about 230 gallons per minute since 1995. In general, the composition of water collected from the bedrock wells, regolith wells, and City Lake is similar; calcium and bicarbonate are the dominant cation and anion, respectively. Water from the regolith wells and the lake have lower concentrations of major ions than does water from the bedrock wells. Many of the ground-water samples collected from the Rhodes Jordan Wellfield during October-November 1995, and from the wellfield and three additional observation well sites during August 1996, contain volatile organic compounds. Volatile organic compounds were detected in ground-water samples collected from several bedrock and regolith wells located in urban areas. Trace concentrations of tetrachloroethylene, trichloroethylene, 1,1-dichloroethane, trichlorofluoromethane, 1,1,1-trichloroethane, and cis-1,2-dichloroethene were detected. Methyl-tert-butyl ether (MTBE)-a compound used to increase the octane level in gasoline-was detected at concentrations above expected urban background levels in bedrock wells in the Rhodes Jordan Wellfield. Concentrations of MTBE ranged from 0.6 to 12 micrograms per liter in October-November 1995, and from 0.6 to 26 micrograms per liter in August 1996. Continuous ground-water-level data suggest that the fractured crystalline-bedrock aquifer (amphibolite unit) at the Rhodes Jordan Wellfield, generally is dewatered to a depth near a productive fracture during the regular pumping cycle of 18 hours per day, 5 days on and 2 days off per week. However, when the stress on the aquifer is increased by extending the pumping period up to as much as 18 days, or by pumping longer that 18 hours per day, the aquifer exhibits an unusual condition of recovery. Areal effects of pumping have been observed at distances of as much as one mile, extending across surface-water drainage divides.

Flow and geochemistry of groundwater beneath a back-barrier lagoon: The subterranean estuary at Chincoteague Bay, Maryland, USA

USGS Publications Warehouse

Bratton, J.F.; Böhlke, J.K.; Krantz, D.E.; Tobias, C.R.

2009-01-01

To better understand large-scale interactions between fresh and saline groundwater beneath an Atlantic coastal estuary, an offshore drilling and sampling study was performed in a large barrier-bounded lagoon, Chincoteague Bay, Maryland, USA. Groundwater that was significantly fresher than overlying bay water was found in shallow plumes up to 8??m thick extending more than 1700??m offshore. Groundwater saltier than bay surface water was found locally beneath the lagoon and the barrier island, indicating recharge by saline water concentrated by evaporation prior to infiltration. Steep salinity and nutrient gradients occur within a few meters of the sediment surface in most locations studied, with buried peats and estuarine muds acting as confining units. Groundwater ages were generally more than 50??years in both fresh and brackish waters as deep as 23??m below the bay bottom. Water chemistry and isotopic data indicate that freshened plumes beneath the estuary are mixtures of water originally recharged on land and varying amounts of estuarine surface water that circulated through the bay floor, possibly at some distance from the sampling location. Ammonium is the dominant fixed nitrogen species in saline groundwater beneath the estuary at the locations sampled. Isotopic and dissolved-gas data from one location indicate that denitrification within the subsurface flow system removed terrestrial nitrate from fresh groundwater prior to discharge along the western side of the estuary. Similar situations, with one or more shallow semi-confined flow systems where groundwater geochemistry is strongly influenced by circulation of surface estuary water through organic-rich sediments, may be common on the Atlantic margin and elsewhere.

A Transient Electromagnetic Analysis of Groundwater on the Utah-Arizona Border

NASA Astrophysics Data System (ADS)

Vander Vis, Tanya

Groundwater is often the primary water source for municipal and agricultural purposes, especially in the arid and semi-arid southwestern United States where surface water is limited. Understanding subsurface structure and groundwater flow is an essential part of managing this limited resource, however, it is often difficult and expensive to obtain extensive subsurface data. The purpose of this study was to better understand the Navajo Sandstone Aquifer in the region south of the East Fork of the Virgin River in southern Utah and north of Pipe Spring National Monument in northern Arizona. This was accomplished by using transient electromagnetics (TEM) to define the depth to the water table and to determine the location of the groundwater divide between the East Fork of the Virgin River and Pipe Spring National Monument. The Navajo Sandstone Aquifer is important regionally as it supplies water to the National Park Service (NPS), the Kaibab Paiute Tribe, and local communities, as well as, numerous springs that feed the Virgin River and Pipe Spring National Monument. A transient electromagnetic survey was conducted using an in-loop configuration and 30 receiver locations. This method was chosen because it is inexpensive relative to drilling costly wells and is highly sensitive to groundwater systems. Results from modeling the transient response show the groundwater divide 1500m south of the Utah-Arizona border. The National Park Service is interested in the location of the groundwater divide because, in Utah, Zion National Park has rights to water that flows through park boundaries and these rights extend to the groundwater system. Subsurface information from this study can be used to inform future policy decisions.

Evaluating groundwater depletion as computed by a global water model

NASA Astrophysics Data System (ADS)

Schuh, Carina; Doell, Petra; Mueller Schmied, Hannes; Portmann, Felix

2013-04-01

When groundwater abstraction occurs faster than its replenishment over a long time and in a large area, the result is an overexploitation or depletion of groundwater. The problem is aggravated in areas where a growing population relies on freshwater resources for an intensive irrigation agriculture that is meant to guarantee food security. Especially in semi-arid and arid regions, the dominant use for groundwater is irrigation, reaching more than 95% of total water use. Therefore, the hot spots for groundwater depletion are the world's major irrigation areas like the central United States, north-western India and north China. Groundwater depletion presents a major threat to securing agricultural productivity and domestic water supply in these parts of the world. Besides, the environmental consequences that accompany the abstraction of groundwater are severe. Within the scientific community there is a common understanding that high-quality data on globally existing groundwater resources are deficient. In order to allow a sustainable management of the world's available groundwater resources, especially in areas under current water stress, the quantification of groundwater depletion is of high importance. WaterGAP (Water - Global Assessment and Prognosis) is a global model of water availability and water use which can serve to estimate the impact of groundwater and surface water withdrawals on groundwater storage. The new WaterGAP version 2.2a was modified to allow for an improved analysis of groundwater storage changes in semi-arid and arid regions. Now, groundwater recharge from surface water bodies is simulated in semi-arid and arid areas. Estimation of net groundwater abstractions was modified with respect of irrigation water use efficiency for groundwater and return flow fractions. In addition, irrigation consumptive use has been set to 70% of optimal irrigation consumptive use, assuming deficit irrigation to prevail in these parts of the world. Based on time series of groundwater storage as computed by WaterGAP, the yearly groundwater depletion rates for the period 1901-2009 have been determined and compared to independent estimates (well observations and GRACE satellite data). So far, the results show that the former WaterGAP standard version overestimates groundwater storage losses considerably in all of the study regions (USA, north-western India, and North China Plain) whereas the improved WaterGAP 2.2a mimics observed groundwater depletion to a high degree.

Cellulosic biofuels from crop residue and groundwater extraction in the US Plains: the case of Nebraska.

PubMed

Sesmero, Juan P

2014-11-01

This study develops a model of crop residue (i.e. stover) supply and derived demand for irrigation water accounting for non-linear effects of soil organic matter on soil's water holding capacity. The model is calibrated for typical conditions in central Nebraska, United States, and identifies potential interactions between water and biofuel policies. The price offered for feedstock by a cost-minimizing plant facing that stover supply response is calculated. Results indicate that as biofuel production volumes increase, soil carbon depletion per unit of biofuel produced decreases. Consumption of groundwater per unit of biofuel produced first decreases and then increases (after a threshold of 363 dam(3) of biofuels per year) due to plants' increased reliance on the extensive margin for additional biomass. The analysis reveals a tension between biofuel and water policies. As biofuel production raises the economic benefits of relaxing water conservation policies (measured by the "shadow price" of water) increase. Copyright © 2014 Elsevier Ltd. All rights reserved.

Numerical simulation of groundwater flow for the Yakima River basin aquifer system, Washington

USGS Publications Warehouse

Ely, D.M.; Bachmann, M.P.; Vaccaro, J.J.

2011-01-01

Five applications (scenarios) of the model were completed to obtain a better understanding of the relation between pumpage and surface-water resources and groundwater levels. For the first three scenarios, the calibrated transient model was used to simulate conditions without: (1) pumpage from all hydrogeologic units, (2) pumpage from basalt hydrogeologic units, and (3) exempt-well pumpage. The simulation results indicated potential streamflow capture by the existing pumpage from 1960 through 2001. The quantity of streamflow capture generally was inversely related to the total quantity of pumpage eliminated in the model scenarios. For the fourth scenario, the model simulated 1994 through 2001 under existing conditions with additional pumpage estimated for pending groundwater applications. The differences between the calibrated model streamflow and this scenario indicated additional decreases in streamflow of 91 cubic feet per second in the model domain. Existing conditions representing 1994 through 2001 were projected through 2025 for the fifth scenario and indicated additional streamflow decreases of 38 cubic feet per second and groundwater-level declines.

Principal aquifers can contribute radium to sources of drinking water under certain geochemical conditions

USGS Publications Warehouse

Szabo, Zoltan; Fischer, Jeffrey M.; Hancock, Tracy Connell

2012-01-01

What are the most important factors affecting dissolved radium concentrations in principal aquifers used for drinking water in the United States? Study results reveal where radium was detected and how rock type and chemical processes control radium occurrence. Knowledge of the geochemical conditions may help water-resource managers anticipate where radium may be elevated in groundwater and minimize exposure to radium, which contributes to cancer risk. Summary of Major Findings: * Concentrations of radium in principal aquifers used for drinking water throughout the United States generally were below 5 picocuries per liter (pCi/L), the U.S. Environmental Protection Agency (USEPA) maximum contaminant level (MCL) for combined radium - radium-226 (Ra-226) plus radium-228 (Ra-228) - in public water supplies. About 3 percent of sampled wells had combined radium concentrations greater than the MCL. * Elevated concentrations of combined radium were more common in groundwater in the eastern and central United States than in other regions of the Nation. About 98 percent of the wells that contained combined radium at concentrations greater than the MCL were east of the High Plains. * The highest concentrations of combined radium were in the Mid-Continent and Ozark Plateau Cambro-Ordovician aquifer system and the Northern Atlantic Coastal Plain aquifer system. More than 20 percent of sampled wells in these aquifers had combined radium concentrations that were greater than or equal to the MCL. * Concentrations of Ra-226 correlated with those of Ra-228. Radium-226 and Ra-228 occur most frequently together in unconsolidated sand aquifers, and their presence is strongly linked to groundwater chemistry. * Three common geochemical factors are associated with the highest radium concentrations in groundwater: (1) oxygen-poor water, (2) acidic conditions (low pH), and (3) high concentrations of dissolved solids.

Probability distributions of hydraulic conductivity for the hydrogeologic units of the Death Valley regional ground-water flow system, Nevada and California

USGS Publications Warehouse

Belcher, Wayne R.; Sweetkind, Donald S.; Elliott, Peggy E.

2002-01-01

The use of geologic information such as lithology and rock properties is important to constrain conceptual and numerical hydrogeologic models. This geologic information is difficult to apply explicitly to numerical modeling and analyses because it tends to be qualitative rather than quantitative. This study uses a compilation of hydraulic-conductivity measurements to derive estimates of the probability distributions for several hydrogeologic units within the Death Valley regional ground-water flow system, a geologically and hydrologically complex region underlain by basin-fill sediments, volcanic, intrusive, sedimentary, and metamorphic rocks. Probability distributions of hydraulic conductivity for general rock types have been studied previously; however, this study provides more detailed definition of hydrogeologic units based on lithostratigraphy, lithology, alteration, and fracturing and compares the probability distributions to the aquifer test data. Results suggest that these probability distributions can be used for studies involving, for example, numerical flow modeling, recharge, evapotranspiration, and rainfall runoff. These probability distributions can be used for such studies involving the hydrogeologic units in the region, as well as for similar rock types elsewhere. Within the study area, fracturing appears to have the greatest influence on the hydraulic conductivity of carbonate bedrock hydrogeologic units. Similar to earlier studies, we find that alteration and welding in the Tertiary volcanic rocks greatly influence hydraulic conductivity. As alteration increases, hydraulic conductivity tends to decrease. Increasing degrees of welding appears to increase hydraulic conductivity because welding increases the brittleness of the volcanic rocks, thus increasing the amount of fracturing.

Chemical and isotope compositions of shallow groundwater in areas impacted by hydraulic fracturing and surface mining in the Central Appalachian Basin, Eastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeDoux, St. Thomas M.; Szynkiewicz, Anna; Faiia, Anthony M.

Here, hydraulic fracturing of shale deposits has greatly increased the productivity of the natural gas industry by allowing it to exploit previously inaccessible reservoirs. Previous research has demonstrated that this practice has the potential to contaminate shallow aquifers with methane (CH 4) from deeper formations. This study compares concentrations and isotopic compositions of CH 4 sampled from domestic groundwater wells in Letcher County, Eastern Kentucky in order to characterize its occurrence and origins in relation to both neighboring hydraulically fractured natural gas wells and surface coal mines. The studied groundwater showed concentrations of CH 4 ranging from 0.05 mg/L tomore » 10 mg/L, thus, no immediate remediation is required. The δ 13C values of CH 4 ranged from 66‰ to 16‰, and δ 2H values ranged from –286‰ to –86‰, suggesting an immature thermogenic and mixed biogenic/thermogenic origin. The occurrence of CH 4 was not correlated with proximity to hydraulically fractured natural gas wells. Generally, CH 4 occurrence corresponded with groundwater abundant in Na +, Cl –, and HCO 3 – , and with low concentrations of SO 4 –2. The CH 4 and SO 4 –2 concentrations were best predicted by the oxidation/reduction potential of the studied groundwater. CH 4 was abundant in more reducing waters, and SO 4 –2 was abundant in more oxidizing waters. Additionally, groundwater in greater proximity to surface mining was more likely to be oxidized. This, in turn, might have increased the likelihood of CH 4 oxidation in shallow groundwater.« less

Chemical and isotope compositions of shallow groundwater in areas impacted by hydraulic fracturing and surface mining in the Central Appalachian Basin, Eastern United States

DOE PAGES

LeDoux, St. Thomas M.; Szynkiewicz, Anna; Faiia, Anthony M.; ...

2016-05-17

Here, hydraulic fracturing of shale deposits has greatly increased the productivity of the natural gas industry by allowing it to exploit previously inaccessible reservoirs. Previous research has demonstrated that this practice has the potential to contaminate shallow aquifers with methane (CH 4) from deeper formations. This study compares concentrations and isotopic compositions of CH 4 sampled from domestic groundwater wells in Letcher County, Eastern Kentucky in order to characterize its occurrence and origins in relation to both neighboring hydraulically fractured natural gas wells and surface coal mines. The studied groundwater showed concentrations of CH 4 ranging from 0.05 mg/L tomore » 10 mg/L, thus, no immediate remediation is required. The δ 13C values of CH 4 ranged from 66‰ to 16‰, and δ 2H values ranged from –286‰ to –86‰, suggesting an immature thermogenic and mixed biogenic/thermogenic origin. The occurrence of CH 4 was not correlated with proximity to hydraulically fractured natural gas wells. Generally, CH 4 occurrence corresponded with groundwater abundant in Na +, Cl –, and HCO 3 – , and with low concentrations of SO 4 –2. The CH 4 and SO 4 –2 concentrations were best predicted by the oxidation/reduction potential of the studied groundwater. CH 4 was abundant in more reducing waters, and SO 4 –2 was abundant in more oxidizing waters. Additionally, groundwater in greater proximity to surface mining was more likely to be oxidized. This, in turn, might have increased the likelihood of CH 4 oxidation in shallow groundwater.« less

Assessment of groundwater quality in Kashipur Block, Purulia district, West Bengal

NASA Astrophysics Data System (ADS)

Kundu, Anindita; Nag, S. K.

2018-03-01

Hydrogeochemical investigation of groundwater resources of Kashipur Block, Purulia district, West Bengal has been carried out to assess the water quality for domestic and irrigation uses. Twenty groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, hardness, major anions (CO3 2-, HCO3 -, Cl-, SO4 2-, F-) and cations (Ca2+, Mg2+, Fe2+, Na+, K+). Study results reveal that the groundwater of the area is mostly acidic in nature. The trend amongst average ionic concentrations of cations and anions is Mg2+ > Ca2+ > Na+ > Fe2+ > K+ and Cl- > HCO3 - > CO3 2- > SO4 2- > F- respectively during the post monsoon whereas the trend for cations and anions are Mg2+ > Ca2+> Na+ > K+ > Fe and Cl- > HCO3 - > SO4 2- > F- > CO3 - in pre monsoon session, respectively. To explore the ionic toxicity of the study area, the derived parameters like sodium adsorption ratio, soluble sodium percentage, residual sodium carbonate, magnesium adsorption ratio, Kelly's ratio and permeability index were calculated. The hydro geochemical data suggest that weathering of rock forming minerals along with secondary contributions from agricultural and anthropogenic sources are mainly controlling the groundwater composition of Kashipur Block, Purulia District. According to piper diagram, water samples of most of the area of the block are fresh water and in some areas sulphate rich throughout the year. All samples are distributed to central rock dominance category. Groundwater chemistry of this block is mainly controlled by the interaction existing between the litho units and the percolating water into the subsurface domain. However, the groundwater quality and suitability of this study area can be termed as good to moderate with a few exceptions which have been encountered on a local scale.

Groundwater data network interoperability

USGS Publications Warehouse

Brodaric, Boyan; Booth, Nathaniel; Boisvert, Eric; Lucido, Jessica M.

2016-01-01

Water data networks are increasingly being integrated to answer complex scientific questions that often span large geographical areas and cross political borders. Data heterogeneity is a major obstacle that impedes interoperability within and between such networks. It is resolved here for groundwater data at five levels of interoperability, within a Spatial Data Infrastructure architecture. The result is a pair of distinct national groundwater data networks for the United States and Canada, and a combined data network in which they are interoperable. This combined data network enables, for the first time, transparent public access to harmonized groundwater data from both sides of the shared international border.

Diversity and expression of different forms of RubisCO genes in polluted groundwater under different redox conditions.

PubMed

Alfreider, Albin; Schirmer, Mario; Vogt, Carsten

2012-03-01

Groundwater polluted with methyl-tert-butyl ether (MTBE) and ammonium was investigated for chemolithoautotrophic CO(2) fixation capabilities based on detailed analyses of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large subunit genes. Samples retrieved from a groundwater conditioning unit, characterized by different redox conditions, were examined for the presence of form IA, form IC (cbbL) and form II (cbbM) RubisCO genes and transcripts obtained from DNA- and RNA-extracts. Form IA RubisCO sequences, which revealed a complex and distinct variety in different sampling stations, were expressed in the original groundwater and in samples amended with oxygen, but not in the aquifer groundwater enriched with nitrate. Form IC RubisCO genes were exclusively detected in groundwater supplied with oxygen and sequences were affiliated with cbbL genes in nitrifying bacteria. cbbM genes were not expressed in the oxygen-amended groundwater, probably due to the low CO(2) /O(2) substrate specificity of this enzyme. Most form II RubisCO transcripts were affiliated with RubisCO genes of denitrifiers, which are important residents in the groundwater supplied with nitrate. The distinct distribution pattern and diversity of RubisCO genes and transcripts obtained in this study suggest that the induction of different RubisCO enzymes is highly regulated and closely linked to the actual environmental conditions. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Analysis of Aquifer Response, Groundwater Flow, and PlumeEvolution at Site OU 1, Former Fort Ord, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, Preston D.; Oldenburg, Curtis M.; Su, Grace W.

2005-02-24

This report presents a continuation from Oldenburg et al. (2002) of analysis of the hydrogeology, In-Situ Permeable Flow Sensor (ISPFS) results, aquifer response, and changes in the trichloroethylene (TCE) groundwater plume at Operational Unit 1 (OU 1) adjacent to the former Fritzsche Army Airfield at the former Fort Ord Army Base, located on Monterey Bay in northern Monterey County. Fuels and solvents were burned on a portion of OU 1 called the Fire Drill Area (FDA) during airport fire suppression training between 1962 and 1985. This activity resulted in soil and groundwater contamination in the unconfined A-aquifer. In the latemore » 1980's, soil excavation and bioremediation were successful in remediating soil contamination at the site. Shortly thereafter, a groundwater pump, treat, and recharge system commenced operation. This system has been largely successful at remediating groundwater contamination at the head of the groundwater plume. However, a trichloroethylene (TCE) groundwater plume extends approximately 3000 ft (900 m) to the northwest away from the FDA. In the analyses presented here, we augment our prior work (Oldenburg et al., 2002) with new information including treatment-system totalizer data, recent water-level and chemistry data, and data collected from new wells to discern trends in contaminant migration and groundwater flow that may be useful for ongoing remediation efforts. Some conclusions from the prior study have been modified based on these new analyses, and these are pointed out clearly in this report.« less

Nutrients in groundwaters of the conterminous United States, 1992-1995

USGS Publications Warehouse

Nolan, B.T.; Stoner, J.D.

2000-01-01

Results of a national water quality assessment indicate that nitrate is detected in 71% of groundwater samples, more than 13 times as often as ammonia, nitrite, organic nitrogen, and orthophosphate, based on a common detection threshold of 0.2 mg/L. Shallow groundwater (typically 5 m deep or less) beneath agricultural land has the highest median nitrate concentration (3.4 mg/L), followed by shallow groundwater beneath urban land (1.6 mg/L) and deeper groundwater in major aquifers (0.48 mg/L). Nitrate exceeds the maximum contaminant level, 10 mg/L as nitrogen, in more than 15% of groundwater samples from 4 of 33 major aquifers commonly used as a source of drinking water. Nitrate concentration in groundwater is variable and depends on interactions among several factors, including nitrogen loading, soil type, aquifer permeability, recharge rate, and climate. For a given nitrogen loading, factors that generally increase nitrate concentration in groundwater include well-drained soils, fractured bedrock, and irrigation. Factors that mitigate nitrate contamination of groundwater include poorly drained soils, greater depth to groundwater, artificial drainage systems, intervening layers of unfractured bedrock, a low rate of groundwater recharge, and anaerobic conditions in aquifers.

Conceptual model and numerical simulation of the ground-water-flow system in the unconsolidated deposits of the Colville River Watershed, Stevens County, Washington

USGS Publications Warehouse

Ely, D. Matthew; Kahle, Sue C.

2004-01-01

Increased use of ground- and surface-water supplies in watersheds of Washington State in recent years has created concern that insufficient instream flows remain for fish and other uses. Issuance of new ground-water rights in the Colville River Watershed was halted by the Washington Department of Ecology due to possible hydraulic continuity of the ground and surface waters. A ground-water-flow model was developed to aid in the understanding of the ground-water system and the regional effects of ground-water development alternatives on the water resources of the Colville River Watershed. The Colville River Watershed is underlain by unconsolidated deposits of glacial and non-glacial origin. The surficial geologic units and the deposits at depth were differentiated into aquifers and confining units on the basis of areal extent and general water-bearing characteristics. Five principal hydrogeologic units are recognized in the study area and form the basis of the ground-water-flow model. A steady-state ground-water-flow model of the Colville River Watershed was developed to simulate September 2001 conditions. The simulation period represented a period of below-average precipitation. The model was calibrated using nonlinear regression to minimize the weighted differences or residuals between simulated and measured hydraulic head and stream discharge. Simulated inflow to the model area was 53,000 acre-feet per year (acre-ft/yr) from precipitation and secondary recharge, and 36,000 acre-ft/yr from stream and lake leakage. Simulated outflow from the model was primarily through discharge to streams and lakes (71,000 acre-ft/yr), ground-water outflow (9,000 acre-ft/yr), and ground-water withdrawals (9,000 acre-ft/yr). Because the period of simulation, September 2001, was extremely dry, all components of the ground-water budget are presumably less than average flow conditions. The calibrated model was used to simulate the possible effects of increased ground-water pumping. Although the steady-state model cannot be used to predict how long it would take for effects to occur, it does simulate the ultimate response to such changes relative to September 2001 (relatively dry) conditions. Steady-state simulations indicated that increased pumping would result in decreased discharge to streams and lakes and decreased ground-water outflow. The location of the simulated increased ground-water pumping determined the primary source of the water withdrawn. Simulated pumping wells in the northern end of the main Colville River valley diverted a large percentage of the pumpage from ground-water outflow. Simulated pumping wells in the southern end of the main Colville River valley diverted a large percentage of the pumpage from flow to rivers and streams. The calibrated steady-state model also was used to simulate predevelopment conditions, during which no ground-water pumping, secondary recharge, or irrigation application occurred. Cumulative streamflow in the Colville River Watershed increased by 1.1 cubic feet per second, or about 36 percent of net ground-water pumping in 2001. The model is intended to simulate the regional ground-water-flow system of the Colville River Watershed and can be used as a tool for water-resource managers to assess the ultimate regional effects of changes in stresses. The regional scale of the model, coupled with relatively sparse data, must be considered when applying the model in areas of poorly understood hydrology, or examining hydrologic conditions at a larger scale than what is appropriate.

Groundwater development stress: Global-scale indices compared to regional modeling

USGS Publications Warehouse

Alley, William; Clark, Brian R.; Ely, Matt; Faunt, Claudia

2018-01-01

The increased availability of global datasets and technologies such as global hydrologic models and the Gravity Recovery and Climate Experiment (GRACE) satellites have resulted in a growing number of global-scale assessments of water availability using simple indices of water stress. Developed initially for surface water, such indices are increasingly used to evaluate global groundwater resources. We compare indices of groundwater development stress for three major agricultural areas of the United States to information available from regional water budgets developed from detailed groundwater modeling. These comparisons illustrate the potential value of regional-scale analyses to supplement global hydrological models and GRACE analyses of groundwater depletion. Regional-scale analyses allow assessments of water stress that better account for scale effects, the dynamics of groundwater flow systems, the complexities of irrigated agricultural systems, and the laws, regulations, engineering, and socioeconomic factors that govern groundwater use. Strategic use of regional-scale models with global-scale analyses would greatly enhance knowledge of the global groundwater depletion problem.

Water levels prior to January 1, 1954 in observation wells, in Nebraska: part 1. Adams through Howard Counties

USGS Publications Warehouse

Keech, C.F.; Case, R.L.

1954-01-01

During the fall of 1945, as part of the program for the development of the resources of the Missouri River basin, the United States Geological Survey began a new series of groundwater investigation in Nebraska.  Those studies were coordinated with the already existing program of ground-water studies that was begun in 1930 by the U.S. Geological Survey in cooperation with the Conservation and Survey Division of the University of Nebraska. Most of the water-level measurements in this report were obtained and compiled as part of the Missouri Basin Development Program.

NRC evaluates groundwater programs

NASA Astrophysics Data System (ADS)

A recent report by the National Research Council (NRC) noted that about half the people of the United States depend on wells for their drinking water, but recent tests reveal widespread contamination.Responsibility for monitoring and protecting groundwater supplies lies largely with state governments. Federal funding of model projects under the Clean Water Act expired in 1983. However, the U.S. Environmental Protection Agency (EPA) has asked the NRC to identify and evaluate ten state and local groundwater protection programs and to recommend features that may be applied in other areas. A committee, organized by the Water Science and Technology Board and chaired by Jerome B. Gilbert, general manager of the East Bay Municipal Utility District of Oakland, Calif., has undertaken the study. The report is expected to be completed in March 1986.

Aeromonas isolates from human diarrheic stool and groundwater compared by pulsed-field gel electrophoresis.

PubMed

Borchardt, Mark A; Stemper, Mary E; Standridge, Jon H

2003-02-01

Gastrointestinal infections of Aeromonas species are generally considered waterborne; for this reason, Aeromonas hydrophila has been placed on the United States Environmental Protection Agency Contaminant Candidate List of emerging pathogens in drinking water. In this study, we compared pulsed-field gel electrophoresis patterns of Aeromonas isolates from stool specimens of patients with diarrhea with Aeromonas isolates from patients' drinking water. Among 2,565 diarrheic stool specimens submitted to a Wisconsin clinical reference laboratory, 17 (0.66%) tested positive for Aeromonas. Groundwater isolates of Aeromonas were obtained from private wells throughout Wisconsin and the drinking water of Aeromonas-positive patients. The analysis showed that the stool and drinking water isolates were genetically unrelated, suggesting that in this population Aeromonas gastrointestinal infections were not linked with groundwater exposures.

Aeromonas Isolates from Human Diarrheic Stool and Groundwater Compared by Pulsed-Field Gel Electrophoresis

PubMed Central

Stemper, Mary E.; Standridge, Jon H.

2003-01-01

Gastrointestinal infections of Aeromonas species are generally considered waterborne; for this reason, Aeromonas hydrophila has been placed on the United States Environmental Protection Agency Contaminant Candidate List of emerging pathogens in drinking water. In this study, we compared pulsed-field gel electrophoresis patterns of Aeromonas isolates from stool specimens of patients with diarrhea with Aeromonas isolates from patients’ drinking water. Among 2,565 diarrheic stool specimens submitted to a Wisconsin clinical reference laboratory, 17 (0.66%) tested positive for Aeromonas. Groundwater isolates of Aeromonas were obtained from private wells throughout Wisconsin and the drinking water of Aeromonas-positive patients. The analysis showed that the stool and drinking water isolates were genetically unrelated, suggesting that in this population Aeromonas gastrointestinal infections were not linked with groundwater exposures. PMID:12603994

Illinois ground-water observation network; a preliminary planning document for network design

USGS Publications Warehouse

Frost, L.R.; O'Hearn, Michael; Gibb, J.P.; Sherrill, M.G.

1984-01-01

Water-level and water-quality networks in Illinois were evaluated to determine the adequacy and completeness of available data bases. Ground-water data in present data bases are inadequate to provide information on ground-water quality and water levels in large areas of Illinois and in the major geohydrologic units underlying Illinois and surrounding areas. Data-management needs indicate that a new data base is desirable and could be developed by use of carefully selected available data and new data. Types of data needed to define ground-water quality and water levels in selected geohydrologic units were tentatively identified. They include data on concentrations of organic chemicals related to activities of man, and concentrations of inorganic chemicals which relate either to man 's activities or to the chemical composition of the source aquifer. Water-level data are needed which can be used to describe short- and long-term stresses on the ground-water resources of Illinois. Establishment of priorities for data collection has been deferred until existing hydrologic data files can be stored for usable data and until input from other local, State, and Federal agencies can be solicited and compiled. (USGS)

Review Team Focused Modeling Analysis of Radial Collector Well Operation on the Hypersaline Groundwater Plume beneath the Turkey Point Site near Homestead, Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oostrom, Martinus; Vail, Lance W.

Researchers at Pacific Northwest National Laboratory served as members of a U.S. Nuclear Regulatory Commission review team for the Florida Power & Light Company’s application for two combined construction permits and operating licenses (combined licenses or COLs) for two proposed new reactor units—Turkey Point Units 6 and 7. The review team evaluated the environmental impacts of the proposed action based on the October 29, 2014 revision of the COL application, including the Environmental Report, responses to requests for additional information, and supplemental information. As part of this effort, team members tasked with assessing the environmental effects of proposed construction andmore » operation of Units 6 and 7 at the Turkey Point site reviewed two separate modeling studies that analyzed the interaction between surface water and groundwater that would be altered by the operation of radial collector wells (RCWs) at the site. To further confirm their understanding of the groundwater hydrodynamics and to consider whether certain actions, proposed after the two earlier modeling studies were completed, would alter the earlier conclusions documented by the review team in their draft environmental impact statement (EIS; NRC 2015), a third modeling analysis was performed. The third modeling analysis is discussed in this report.« less

Using hydrochemical data and modelling to enhance the knowledge of groundwater flow and quality in an alluvial aquifer of Zagreb, Croatia.

PubMed

Marković, Tamara; Brkić, Željka; Larva, Ozren

2013-08-01

The Zagreb alluvial aquifer system is located in the southwest of the Pannonian Basin in the Sava Valley in Croatia. It is composed of Quaternary unconsolidated deposits and is highly utilised, primarily as a water supply for the more than one million inhabitants of the capital city of Croatia. To determine the origin and dynamics of the groundwater and to enhance the knowledge of groundwater flow and the interactions between the groundwater and surface water, extensive hydrogeological and hydrochemical investigations have been completed. The groundwater levels monitored in nested observation wells and the lithological profile indicate that the aquifer is a single hydrogeologic unit, but the geochemical characteristics of the aquifer indicate stratification. The weathering of carbonate and silicate minerals has an important role in groundwater chemistry, especially in the area where old meanders of the Sava River existed. Groundwater quality was observed to be better in the deeper parts of the aquifer than in the shallower parts. Furthermore, deterioration of the groundwater quality was observed in the area under the influence of the landfill. The stable isotopic composition of all sampled waters indicates meteoric origin. NETPATH-WIN was used to calculate the mixing proportions between initial waters (water from the Sava River and groundwater from "regional" flow) in the final water (groundwater sampled from observation wells). According to the results, the mixing proportions of "regional" flow and the river water depend on hydrological conditions, the duration of certain hydrological conditions and the vicinity of the Sava River. Moreover, although the aquifer system behaves as a single hydrogeologic unit from a hydraulic point of view, it still clearly demonstrates geochemical stratification, which could be a decisive factor in future utilisation strategies for the aquifer system. Copyright © 2013 Elsevier B.V. All rights reserved.

Numerical simulation of the groundwater-flow system of the Kitsap Peninsula, west-central Washington

USGS Publications Warehouse

Frans, Lonna M.; Olsen, Theresa D.

2016-05-05

A groundwater-flow model was developed to improve understanding of water resources on the Kitsap Peninsula. The Kitsap Peninsula is in the Puget Sound lowland of west-central Washington, is bounded by Puget Sound on the east and by Hood Canal on the west, and covers an area of about 575 square miles. The peninsula encompasses all of Kitsap County, Mason County north of Hood Canal, and part of Pierce County west of Puget Sound. The peninsula is surrounded by saltwater, and the hydrologic setting is similar to that of an island. The study area is underlain by a thick sequence of unconsolidated glacial and interglacial deposits that overlie sedimentary and volcanic bedrock units that crop out in the central part of the study area. Twelve hydrogeologic units consisting of aquifers, confining units, and an underlying bedrock unit form the basis of the groundwater-flow model.Groundwater flow on the Kitsap Peninsula was simulated using the groundwater-flow model, MODFLOW‑NWT. The finite difference model grid comprises 536 rows, 362 columns, and 14 layers. Each model cell has a horizontal dimension of 500 by 500 feet, and the model contains a total of 1,227,772 active cells. Groundwater flow was simulated for transient conditions. Transient conditions were simulated for January 1985–December 2012 using annual stress periods for 1985–2004 and monthly stress periods for 2005–2012. During model calibration, variables were adjusted within probable ranges to minimize differences between measured and simulated groundwater levels and stream baseflows. As calibrated to transient conditions, the model has a standard deviation for heads and flows of 47.04 feet and 2.46 cubic feet per second, respectively.Simulated inflow to the model area for the 2005–2012 period from precipitation and secondary recharge was 585,323 acre-feet per year (acre-ft/yr) (93 percent of total simulated inflow ignoring changes in storage), and simulated inflow from stream and lake leakage was 43,905 acre-ft/yr (7 percent of total simulated inflow). Simulated outflow from the model primarily was through discharge to streams, lakes, springs, seeps, and Puget Sound (594,595 acre-ft/yr; 95 percent of total simulated outflow excluding changes in storage) and through withdrawals from wells (30,761 acre-ft/yr; 5 percent of total simulated outflow excluding changes in storage).Six scenarios were formulated with input from project stakeholders and were simulated using the calibrated model to provide representative examples of how the model could be used to evaluate the effects on water levels and stream baseflows of potential changes in groundwater withdrawals, in consumptive use, and in recharge. These included simulations of a steady-state system, no-pumping and return flows, 15-percent increase in current withdrawals in all wells, 80-percent decrease in outdoor water to simulate effects of conservation efforts, 15-percent decrease in recharge from precipitation to simulate a drought, and particle tracking to determine flow paths.Changes in water-level altitudes and baseflow amounts vary depending on the stress applied to the system in these various scenarios. Reducing recharge by 15 percent between 2005 and 2012 had the largest effect, with water-level altitudes declining throughout the model domain and baseflow amounts decreasing by as much as 18 percent compared to baseline conditions. Changes in pumping volumes had a smaller effect on the model. Removing all pumping and resulting return flows caused increased water-level altitudes in many areas and increased baseflow amounts of between 1 and 3 percent.

Status of groundwater quality in the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit, 2008-2010: California GAMA Priority Basin Project

USGS Publications Warehouse

Parsons, Mary C.; Hancock, Tracy Connell; Kulongoski, Justin T.; Belitz, Kenneth

2014-01-01

Groundwater quality in the approximately 963-square-mile Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in southern California in San Bernardino, Riverside, San Diego, and Imperial Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The GAMA Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer system. The assessment is based on water-quality and ancillary data collected by the U.S. Geological Survey from 52 wells (49 grid wells and 3 understanding wells) and on water-quality data from the California Department of Public Health database. The primary aquifer system was defined by the depth intervals of the wells listed in the California Department of Public Health database for the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. This study assesses the status of the current quality of the groundwater resource by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources in the primary aquifer system of the Borrego Valley, Central Desert, and Low-Use Basins of the Mojave and Sonoran Deserts study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic constituents and special-interest constituents [perchlorate and N-nitrosodimethylamine (NDMA)] were classified as high (relative-concentration greater than 1.0), moderate (relative-concentration greater than 0.1 and less than or equal to 1.0), or low (relative-concentration less than or equal to 0.1). Relative-concentrations of inorganic constituents were classified as high (relative-concentration greater than 1.0), moderate (relative-concentration greater than 0.5 and less than or equal to 1.0), or low (relative-concentration less than or equal to 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with a high relative-concentration for a particular constituent or class of constituents; this percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentages of the primary aquifer system with moderate and low relative-concentrations, respectively, of a constituent or class of constituents. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable to each other (within 90-percent confidence intervals) in the study unit. Inorganic constituents (one or more) with health-based benchmarks were detected at high relative-concentrations in 48 percent of the primary aquifer system and at moderate relative-concentrations in 26 percent of the primary aquifer system. The high aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of fluoride (27 percent), arsenic (18 percent), molybdenum (16 percent), boron (10 percent), uranium (5.6 percent), gross alpha radioactivity (9.7 percent), and nitrate (2.7 percent). The inorganic constituents with secondary maximum contaminant levels (SMCLs) were detected at high relative-concentrations in 13 percent of the primary aquifer system and at moderate relative-concentrations in 39 percent. The high aquifer-scale proportion for SMCL constituents reflected high aquifer-scale proportions of total dissolved solids (TDS, 11 percent), manganese (2.8 percent), and chloride (2.8 percent). Organic constituents were not detected at high relative-concentrations in the primary aquifer system, and were present at moderate relative-concentrations in 5.0 percent, and at low relative-concentrations or were not detected in 95 percent of the primary aquifer system. Of the 148 organic constituents analyzed, 12 constituents were detected. Two organic constituents, chloroform and tetrachloroethene (PCE), were detected in more than 10 percent of samples, but were detected mostly at low relative-concentrations.

The Effect of modeled recharge distribution on simulated groundwater availability and capture

USGS Publications Warehouse

Tillman, Fred D.; Pool, Donald R.; Leake, Stanley A.

2015-01-01

Simulating groundwater flow in basin-fill aquifers of the semiarid southwestern United States commonly requires decisions about how to distribute aquifer recharge. Precipitation can recharge basin-fill aquifers by direct infiltration and transport through faults and fractures in the high-elevation areas, by flowing overland through high-elevation areas to infiltrate at basin-fill margins along mountain fronts, by flowing overland to infiltrate along ephemeral channels that often traverse basins in the area, or by some combination of these processes. The importance of accurately simulating recharge distributions is a current topic of discussion among hydrologists and water managers in the region, but no comparative study has been performed to analyze the effects of different recharge distributions on groundwater simulations. This study investigates the importance of the distribution of aquifer recharge in simulating regional groundwater flow in basin-fill aquifers by calibrating a groundwater-flow model to four different recharge distributions, all with the same total amount of recharge. Similarities are seen in results from steady-state models for optimized hydraulic conductivity values, fit of simulated to observed hydraulic heads, and composite scaled sensitivities of conductivity parameter zones. Transient simulations with hypothetical storage properties and pumping rates produce similar capture rates and storage change results, but differences are noted in the rate of drawdown at some well locations owing to the differences in optimized hydraulic conductivity. Depending on whether the purpose of the groundwater model is to simulate changes in groundwater levels or changes in storage and capture, the distribution of aquifer recharge may or may not be of primary importance.

Groundwater Depletion and the Sharp Increase of Seismicity in the Southern States, How GRACE Data Could Help?

NASA Astrophysics Data System (ADS)

Hong, Z.; Hasan, E.; Hong, Y.; Xia, B.; Zhong, H.

2016-12-01

This study is a contribution to how NASA's Gravity Recovery and Climate Experiment (GRACE) data may be used to track anthropogenic related change in the groundwater in the Southern Great Plains (SGP) as well recently increased seismicity in the southern states. The SGP contains one of the most important groundwater aquifers in the United States, the Ogallala groundwater aquifer, which has been exploited since 1900. Meanwhile, the recent activities of oil and gas extraction from the unconventional shall reservoir systems has led to significantly increased groundwater withdrawal and injection of wastewater. Consequently, numerous induced fracture related earthquakes have been recorded in Oklahoma and Texas between 2002 and 2016 The current paper investigates the utility of GRACE data along with the Land Water Content (LWC) information from the Global Land Data Assimilation System (GLDAS) to monitor and track the groundwater changes in three southern states of SGP (Oklahoma, Texas and New Mexico). Additionally, the paper investigates links between active seismicity and the injection of the wastewater due to the oil and gas production. Using GRACE data yields unprecedented information about the inter-annual changes in the Total Water Storage (TWS) from 2002 to 2016 over SGP. The LWC data set sums the soil moisture records with the the total canopy water storage to reveal the total land surface water content. The arithmetic difference between the TWS and LWC is the Groundwater Anomaly (GWA) for any particular region. In the current study, the GWA analysis reveals the following: (1) statistically significant drop of the GWA of about - 27 mm from 2002 to 2007 due to natural and anthropogenic causes; (2) the increased precipitation records from 2008 to 2011 over SGP leads to significant recovery in TWS and an increase in the groundwater content of about 40 mm; (3) the period from 2012 to 2015 experienced increased GWA of about - 6 mm for the period. Using the available seismicity records showed high agreement between the seismicity and the oil production locations. Additionally, the correlation between the groundwater changes and the seismic activity in the study region showed that the changes in groundwater levels are associated with regions of induced seismic activities.

A combined radio- and stable-isotopic study of a California coastal aquifer system

USGS Publications Warehouse

Swarzenski, Peter W.; Baskaran, Mark; Rosenbauer, Robert J.; Edwards, Brian D.; Land, Michael

2013-01-01

Stable and radioactive tracers were utilized in concert to characterize geochemical processes in a complex coastal groundwater system and to provide constraints on the kinetics of rock/water interactions. Groundwater samples from wells within the Dominguez Gap region of Los Angeles County, California were analyzed for a suite of major cations (Na+, K+, Mg2+, Ca2+) and anions (Cl−, SO42−), silica, alkalinity, select trace elements (Ba, B, Sr), dissolved oxygen, stable isotopes of hydrogen (δD), oxygen (δ18O), dissolved inorganic carbon (δ13CDIC), and radioactive isotopes (3H, 222Rn and 223,224,226,228Ra). In the study area, groundwater may consist of a complex mixture of native groundwater, intruded seawater, non-native injected water, and oil-field brine water. In some wells, Cl− concentrations attained seawater-like values and in conjunction with isotopically heavier δ18O values, these tracers provide information on the extent of seawater intrusion and/or mixing with oil-field brines. Groundwater 3H above 1 tritium unit (TU) was observed only in a few select wells close to the Dominguez Gap area and most other well groundwater was aged pre-1952. Based on an initial 14C value for the study site of 90 percent modern carbon (pmc), groundwater age estimates likely extend beyond 20 kyr before present and confirm deep circulation of some native groundwater through multiple aquifers. Enriched values of groundwater δ13CDIC in the absence of SO42− imply enhanced anaerobic microbial methanogenesis. While secular equilibrium was observed for 234U/238U (activity ratios ~1) in host matrices, strong isotopic fractionation in these groundwater samples can be used to obtain information of adsorption/desorption kinetics. Calculated Ra residence times are short, and the associated desorption rate constant is about three orders of magnitude slower than that of the adsorption rate constant. Combined stable- and radio-isotopic results provide unique insights into aquifer characteristics, such as geochemical cycling, rock/water interactions, and subsurface transport and mixing.

Effects of different boundary conditions on the simulation of groundwater flow in a multi-layered coastal aquifer system (Taranto Gulf, southern Italy)

NASA Astrophysics Data System (ADS)

De Filippis, Giovanna; Foglia, Laura; Giudici, Mauro; Mehl, Steffen; Margiotta, Stefano; Negri, Sergio L.

2017-11-01

The evaluation of the accuracy or reasonableness of numerical models of groundwater flow is a complex task, due to the uncertainties in hydrodynamic properties and boundary conditions and the scarcity of good-quality field data. To assess model reliability, different calibration techniques are joined to evaluate the effects of different kinds of boundary conditions on the groundwater flow in a coastal multi-layered aquifer in southern Italy. In particular, both direct and indirect approaches for inverse modeling were joined through the calibration of one of the most uncertain parameters, namely the hydraulic conductivity of the karst deep hydrostratigraphic unit. The methodology proposed here, and applied to a real case study, confirmed that the selection of boundary conditions is among the most critical and difficult aspects of the characterization of a groundwater system for conceptual analysis or numerical simulation. The practical tests conducted in this study show that incorrect specification of boundary conditions prevents an acceptable match between the model response to the hydraulic stresses and the behavior of the natural system. Such effects have a negative impact on the applicability of numerical modeling to simulate groundwater dynamics in complex hydrogeological situations. This is particularly important for management of the aquifer system investigated in this work, which represents the only available freshwater resource of the study area, and is threatened by overexploitation and saltwater intrusion.

Groundwater chemistry and human health risk assessment in the mining region of East Singhbhum, Jharkhand, India.

PubMed

Singh, Umesh Kumar; Ramanathan, A L; Subramanian, V

2018-08-01

Groundwater chemistry of mining region of East Singhbhum district having complex contaminant sources were investigated based on heavy metals loads and other hydrochemical constituents. This study aimed to identify the degree of heavy metals exposure and their potential health risk to local population. The results of hydrochemical analysis showed that Na + , K + , and Ca 2+ ions are the dominant cations in the groundwater, while HCO 3 - , F - and Cl - ions dominate the anionic part of the groundwater. The weathering process was considered the dominant factor to determine the major ionic composition in the study area. Compositional analysis for heavy metal has identified that groundwater of the study area is contaminated by Cd, Pb and Cr elements. Source of these metals have been identified as an anthropogenic inputs from mining activities and mineral processing units. Health risk analysis of individual heavy metal for chronic daily intake (CDI) and hazard quotient (HQ) was found in the order of Cr > As > Cd > Pb which is indicating high health risk for the population. In addition, Hazard Index (HI) analysis for heavy metals was found significantly high (>1) which is considered as a threat for human population because they have the tendency to accumulate in the body and cause variety of diseases like kidney problem, dysfunction of liver and renal cortex as well as cancer. Copyright © 2018 Elsevier Ltd. All rights reserved.

Radiogenic and Stable Isotope and Hydrogeochemical Investigation of Groundwater, Pajarito Plateau and Surrounding Areas, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patrick Longmire, Michael Dale, Dale Counce, Andrew Manning, Toti Larson, Kim Granzow, Robert Gray, and Brent Newman

2007-07-15

From October 2004 through February 2006, Los Alamos National Laboratory, the New Mexico Environment Department-Department of Energy Oversight Bureau, and the United States Geological Survey conducted a hydrochemical investigation. The purpose of the investigation was to evaluate groundwater flow paths and determine groundwater ages using tritium/helium-3 and carbon-14 along with aqueous inorganic chemistry. Knowledge of groundwater age and flow paths provides a technical basis for selecting wells and springs for monitoring. Groundwater dating is also relevant to groundwater resource management, including aquifer sustainability, especially during periods of long-term drought. At Los Alamos, New Mexico, groundwater is either modern (post-1943), submodernmore » (pre-1943), or mixed (containing both pre- and post-1943 components). The regional aquifer primarily consists of submodern groundwater. Mixed-age groundwater results from initial infiltration of surface water, followed by mixing with perched alluvial and intermediate-depth groundwater and the regional aquifer. No groundwater investigation is complete without using tritium/helium-3 and carbon-14 dating methods to quantify amounts of modern, mixed, and/or submodern components present in samples. Computer models of groundwater flow and transport at Los Alamos should be calibrated to groundwater ages for perched intermediate zones and the regional aquifer determined from this investigation. Results of this study clearly demonstrate the occurrence of multiple flow paths and groundwater ages occurring within the Sierra de los Valles, beneath the Pajarito Plateau, and at the White Rock Canyon springs. Localized groundwater recharge occurs within several canyons dissecting the Pajarito Plateau. Perched intermediate-depth groundwater and the regional aquifer beneath Pueblo Canyon, Los Alamos Canyon, Sandia Canyon, Mortandad Canyon, Pajarito Canyon, and Canon de Valle contain a modern component. This modern component consists of tritium, nitrate, perchlorate, chromate, boron, uranium, and/or high explosive compounds. It is very unlikely that there is only one transport or travel time, ranging from 25 to 62 years, for these conservative chemicals migrating from surface water to the regional water table. Lengths of groundwater flow paths vary within deep saturated zones containing variable concentrations of tritium. The 4-series springs discharging within White Rock Canyon contain a modern component of groundwater, primarily tritium. Average groundwater ages for the regional aquifer beneath the Pajarito Plateau varied from 565 to 10,817 years, based on unadjusted carbon-14 measurements.« less

Hydrogeologic framework and groundwater/surface-water interactions of the upper Yakima River Basin, Kittitas County, central Washington

USGS Publications Warehouse

Gendaszek, Andrew S.; Ely, D. Matthew; Hinkle, Stephen R.; Kahle, Sue C.; Welch, Wendy B.

2014-01-01

The hydrogeology, hydrology, and geochemistry of groundwater and surface water in the upper (western) 860 square miles of the Yakima River Basin in Kittitas County, Washington, were studied to evaluate the groundwater-flow system, occurrence and availability of groundwater, and the extent of groundwater/surface-water interactions. The study area ranged in altitude from 7,960 feet in its headwaters in the Cascade Range to 1,730 feet at the confluence of the Yakima River with Swauk Creek. A west-to-east precipitation gradient exists in the basin with the western, high-altitude headwaters of the basin receiving more than 100 inches of precipitation per year and the eastern, low-altitude part of the basin receiving about 20 inches of precipitation per year. From the early 20th century onward, reservoirs in the upper part of the basin (for example, Keechelus, Kachess, and Cle Elum Lakes) have been managed to store snowmelt for irrigation in the greater Yakima River Basin. Canals transport water from these reservoirs for irrigation in the study area; additional water use is met through groundwater withdrawals from wells and surface-water withdrawals from streams and rivers. Estimated groundwater use for domestic, commercial, and irrigation purposes is reported for the study area. A complex assemblage of sedimentary, metamorphic, and igneous bedrock underlies the study area. In a structural basin in the southeastern part of the study area, the bedrock is overlain by unconsolidated sediments of glacial and alluvial origin. Rocks and sediments were grouped into six hydrogeologic units based on their lithologic and hydraulic characteristics. A map of their extent was developed from previous geologic mapping and lithostratigraphic information from drillers’ logs. Water flows through interstitial space in unconsolidated sediments, but largely flows through fractures and other sources of secondary porosity in bedrock. Generalized groundwater-flow directions within the unconfined part of the aquifers in unconsolidated sediments indicate generalized groundwater movement toward the Yakima River and its tributaries and the outlet of the study area. Groundwater movement through fractures within the bedrock aquifers is complex and varies over spatial scales depending on the architecture of the fracture-flow system and its hydraulic properties. The complexity of the fracturedbedrock groundwater-flow system is supported by a wide range of groundwater ages determined from geochemical analyses of carbon-14, sulfur hexafluoride, and tritium in groundwater. These geochemical data also indicate that the shallow groundwater system is actively flushing with young, isotopically heavy groundwater, but isotopicallylight, Pleistocene-age groundwater with a geochemicallyevolved composition occurs at depth within the fracturedbedrock aquifers of upper Kittitas County. An eastward depletion of stable isotopes in groundwater is consistent with hydrologically separate subbasins. This suggests that groundwater that recharges in one subbasin is not generally available for withdrawal or discharge into surface-water features within other subbasins. Water budget components were calculated for 11 subbasins using a watershed model and varied based on the climate, land uses, and geology of the subbasin. Synoptic streamflow measurements made in August 2011 indicate that groundwater discharges into several tributaries of the Yakima River with several losses of streamflow measured where the streams exit bedrock uplands and flow over unconsolidated sediments. Profiles of stream temperature during late summer suggest cool groundwater inflow over discrete sections of streams. This groundwater/surfacewater connection is further supported by the stable-isotope composition of stream water, which reflects the local stableisotope composition of groundwater measured at some wells and springs. Collectively, these hydrogeologic, hydrologic, and geochemical data support a framework for evaluating the potential effects of future groundwater appropriations on senior surface-water and groundwater rights and streamflows. Although total pumping rates in upper Kittitas County of about 3.5 cubic feet per second are small relative to other components of the water budget, the magnitude, timing, and location of withdrawals may have important effects on the hydrologic system. The heterogeneous and variably fractured bedrock in the study area precluded a detailed evaluation of localized effects of pumping, but several generalizations about the groundwater and surface-water systems can be made. These generalizations include evidence for the continuity between the groundwater and surface-water system apparent from synoptic streamflow measurements, stream-temperature profiles, and stable-isotope data of groundwater and surface waters.

GROUDWATER REMEDIATION AT THE 100-HR-3 OPERABLE UNIT HANFORD SITE WASHINGTON USA - 11507

DOE Office of Scientific and Technical Information (OSTI.GOV)

SMOOT JL; BIEBESHEIMER FH; ELUSKIE JA

2011-01-12

The 100-HR-3 Groundwater Operable Unit (OU) at the Hanford Site underlies three former plutonium production reactors and the associated infrastructure at the 100-D and 100-H Areas. The primary contaminant of concern at the site is hexavalent chromium; the secondary contaminants are strontium-90, technetium-99, tritium, uranium, and nitrate. The hexavalent chromium plume is the largest plume of its type in the state of Washington, covering an area of approximately 7 km{sup 2} (2.7 mi{sup 2}) with concentrations greater than 20 {micro}g/L. Concentrations range from 60,000 {micro}g/L near the former dichromate transfer station in the 100-D Area to large areas of 20more » to 100 {micro}g/L across much of the plume area. Pump-and-treat operations began in 1997 and continued into 2010 at a limited scale of approximately 200 gal/min. Remediation of groundwater has been fairly successful in reaching remedial action objectives (RAOs) of 20 {micro}g/L over a limited region at the 100-H, but less effective at 100-D. In 2000, an in situ, permeable reactive barrier was installed downgradient of the hotspot in 100-D as a second remedy. The RAOs are still being exceeded over a large portion of the area. The CH2M HILL Plateau Remediation Company was awarded the remediation contract for groundwater in 2008 and initiated a remedial process optimization study consisting of modeling and technical studies intended to enhance the remediation. As a result of the study, 1,400 gal/min of expanded treatment capacity are being implemented. These new systems are designed to meet 2012 and 2020 target milestones for protection of the Columbia River and cleanup of the groundwater plumes.« less

GENOTOXICITY STUDIES OF THREE TRIAZINE HERBICIDES III. IN VIVO STUDIES USING THE ALKALINE SINGLE CELL GEL (SCG) ASSAY

EPA Science Inventory

Abstract

Triazine herbicides are prevalent contaminants of groundwater in the agricultural regions of the United States. The literature on the genotoxicity of triazines is rife with conflicting data, though the general tendency is for most studies to report negative resul...

Work Plan for Comprehensive Groundwater Sampling - 2012 (Operable Unit 2), LCP Chemicals Site, Brunswick, GA

EPA Pesticide Factsheets

April 2012 plan to conduct a comprehensive sampling of groundwater from all wells in the site-wide monitoring well network, at the LCP Chemicals Site in Brunswick, GA. Region ID: 04 DocID: 10843427, DocDate: 04-01-2012

Regional strategies for the accelerating global problem of groundwater depletion

NASA Astrophysics Data System (ADS)

Aeschbach-Hertig, Werner; Gleeson, Tom

2012-12-01

Groundwater--the world's largest freshwater resource--is critically important for irrigated agriculture and hence for global food security. Yet depletion is widespread in large groundwater systems in both semi-arid and humid regions of the world. Excessive extraction for irrigation where groundwater is slowly renewed is the main cause of the depletion, and climate change has the potential to exacerbate the problem in some regions. Globally aggregated groundwater depletion contributes to sea-level rise, and has accelerated markedly since the mid-twentieth century. But its impacts on water resources are more obvious at the regional scale, for example in agriculturally important parts of India, China and the United States. Food production in such regions can only be made sustainable in the long term if groundwater levels are stabilized. To this end, a transformation is required in how we value, manage and characterize groundwater systems. Technical approaches--such as water diversion, artificial groundwater recharge and efficient irrigation--have failed to balance regional groundwater budgets. They need to be complemented by more comprehensive strategies that are adapted to the specific social, economic, political and environmental settings of each region.

Modeling irrigation behavior in groundwater systems

NASA Astrophysics Data System (ADS)

Foster, Timothy; Brozović, Nicholas; Butler, Adrian P.

2014-08-01

Integrated hydro-economic models have been widely applied to water management problems in regions of intensive groundwater-fed irrigation. However, policy interpretations may be limited as most existing models do not explicitly consider two important aspects of observed irrigation decision making, namely the limits on instantaneous irrigation rates imposed by well yield and the intraseasonal structure of irrigation planning. We develop a new modeling approach for determining irrigation demand that is based on observed farmer behavior and captures the impacts on production and water use of both well yield and climate. Through a case study of irrigated corn production in the Texas High Plains region of the United States we predict optimal irrigation strategies under variable levels of groundwater supply, and assess the limits of existing models for predicting land and groundwater use decisions by farmers. Our results show that irrigation behavior exhibits complex nonlinear responses to changes in groundwater availability. Declining well yields induce large reductions in the optimal size of irrigated area and irrigation use as constraints on instantaneous application rates limit the ability to maintain sufficient soil moisture to avoid negative impacts on crop yield. We demonstrate that this important behavioral response to limited groundwater availability is not captured by existing modeling approaches, which therefore may be unreliable predictors of irrigation demand, agricultural profitability, and resilience to climate change and aquifer depletion.

Groundwater and surface-water resources in the Bureau of Land Management Moab Master Leasing Plan area and adjacent areas, Grand and San Juan Counties, Utah, and Mesa and Montrose Counties, Colorado

USGS Publications Warehouse

Masbruch, Melissa D.; Shope, Christopher L.

2014-01-01

The Bureau of Land Management (BLM) Canyon Country District Office is preparing a leasing plan known as the Moab Master Leasing Plan (Moab MLP) for oil, gas, and potash mineral rights in an area encompassing 946,469 acres in southeastern Utah. The BLM has identified water resources as being potentially affected by oil, gas, and potash development and has requested that the U.S. Geological Survey prepare a summary of existing water-resources information for the Moab MLP area. This report includes a summary and synthesis of previous and ongoing investigations conducted in the Moab MLP and adjacent areas in Utah and Colorado from the early 1930s through the late 2000s.Eight principal aquifers and six confining units were identified within the study area. Permeability is a function of both the primary permeability from interstitial pore connectivity and secondary permeability created by karst features or faults and fractures. Vertical hydraulic connection generally is restricted to strongly folded and fractured zones, which are concentrated along steeply dipping monoclines and in narrow regions encompassing igneous and salt intrusive masses. Several studies have identified both an upper and lower aquifer system separated by the Pennsylvanian age Paradox Member of the Hermosa Formation evaporite, which is considered a confining unit and is present throughout large parts of the study area.Surface-water resources of the study area are dominated by the Colorado River. Several perennial and ephemeral or intermittent tributaries join the Colorado River as it flows from northeast to southwest across the study area. An annual spring snowmelt and runoff event dominates the hydrology of streams draining mountainous parts of the study area, and most perennial streams in the study area are snowmelt-dominated. A bimodal distribution is observed in hydrographs from some sites with a late-spring snowmelt-runoff peak followed by smaller peaks of shorter duration during the late summer. The large regional streams (Colorado, Green, and Dolores Rivers) integrate the regional hydrologic partitioning of a very large contributing area and, therefore, the hydrographs for these streams are much more smooth and consistent. Several streams throughout the study area are considered impaired and do not meet the standards set by the Environmental Protection Agency for specific designated-use classifications.Limited data are available to quantitatively estimate the large-scale regional groundwater budget for the study area. Previous studies have estimated groundwater budgets for areas in and adjacent to the current study area, namely Moab-Spanish Valley and parts of the Paradox Basin. Most groundwater recharge to the study area originates as infiltration of precipitation from upland areas and is further enhanced in areas covered with sandy soils or in areas where the bedrock is highly fractured. Additional groundwater recharge occurs as seepage from streams and irrigation water, and as subsurface inflow, both vertically between aquifers and as lateral movement into the study area. Groundwater discharge occurs as seepage to streams, evapotranspiration, to springs and seeps, well withdrawals; and as subsurface outflow, both vertically between aquifers and as lateral movement out of the study area across its defined boundaries. Groundwater use in the study area was determined using data from the Utah Division of Water Rights. Most wells in the study area are categorized as having multiple uses.Mean specific-conductance values for groundwater from wells and springs in the study area range from 101 to 220,000 microsiemens per centimeter at 25° C (μS/cm); most of the wells or springs have mean specific-conductance values of less than or equal to 1,000 μS/cm. Previously reported total dissolved-solids concentrations, specific conductances, and other groundwater-quality data for each of the principal aquifers indicate relative freshwater throughout the study area, except within the lower aquifer system and areas in contact with the Paradox Member of the Hermosa Formation evaporites.There is limited information on the resource availability of brines and saline groundwater in the study area. Total dissolved-solids concentrations typically are high (greater than 35,000 milligrams per liter) in groundwater from, or in contact with, the Paradox Member of the Hermosa Formation. Total dissolved-solids concentrations also are high in groundwater samples collected from the lower aquifer system. Because the Paradox Member of the Hermosa Formation is considered a barrier to vertical groundwater flow, most of the brine and saline groundwater resources are restricted to the lower aquifer system.

Geohydrology and simulated ground-water flow in an irrigated area of northwestern Indiana

USGS Publications Warehouse

Arihood, L.D.; Basch, M.E.

1994-01-01

Water for irrigation in parts of Newton and Jasper Counties and adjacent areas of northwestern Indiana is pumped mostly from the carbonate- bedrock aquifer that underlies glacial drift. To help in managing the ground-water resources of the area, a three-dimensional ground-water model was developed and tested with hydrologic data collected during 1986 and 1988. Two major aquifers and a confining unit were identified. The surficial unconfined outwash aquifer consists of sand and some gravel. Saturated thickness averages about 30 feet. Estimated values of horizontal hydraulic conductivity and storage coefficient are 350 feet per day and 0.07, respectively. The generally continuous confining unit beneath the outwash aquifer is composed predominantly of till and lacustrine silt and clay and is 0 to 125 feet thick. The carbonate-bedrock aquifer is composed of Silurian and Devonian dolomitic limestone; dolomite and has a median transmissivity of 2,000 feet squared per day. A nine-layer digital model was developed to simulate flow in the ground-water system. The mean absolute errors for simulated water levels in the bedrock aquifer ranged from 5 to 7 feet for two recent periods of irrigation. The component of the flow system that most affects water-level drawdowns in the bedrock aquifer is the confining unit which controls the rate of leakage to the bedrock aquifer. The model is most accurate in areas for which data for confining-unit thickness and bedrock water levels are available.

MODFLOW-2000, the U.S. Geological Survey Modular Ground-Water Model -Documentation of the Hydrogeologic-Unit Flow (HUF) Package

USGS Publications Warehouse

Anderman, E.R.; Hill, M.C.

2000-01-01

This report documents the Hydrogeologic-Unit Flow (HUF) Package for the groundwater modeling computer program MODFLOW-2000. The HUF Package is an alternative internal flow package that allows the vertical geometry of the system hydrogeology to be defined explicitly within the model using hydrogeologic units that can be different than the definition of the model layers. The HUF Package works with all the processes of MODFLOW-2000. For the Ground-Water Flow Process, the HUF Package calculates effective hydraulic properties for the model layers based on the hydraulic properties of the hydrogeologic units, which are defined by the user using parameters. The hydraulic properties are used to calculate the conductance coefficients and other terms needed to solve the ground-water flow equation. The sensitivity of the model to the parameters defined within the HUF Package input file can be calculated using the Sensitivity Process, using observations defined with the Observation Process. Optimal values of the parameters can be estimated by using the Parameter-Estimation Process. The HUF Package is nearly identical to the Layer-Property Flow (LPF) Package, the major difference being the definition of the vertical geometry of the system hydrogeology. Use of the HUF Package is illustrated in two test cases, which also serve to verify the performance of the package by showing that the Parameter-Estimation Process produces the true parameter values when exact observations are used.

In Situ Biological Treatment Test at Kelly Air Force Base. Volume 3. Appendices.

DTIC Science & Technology

1987-07-01

175 B-12 Results of Groundwater Acidity Monitoring. . . . . . . . 176 B-13 Results of Groundwater Alkalinity Monitoring . . . . . . 177 B- 14 ...Oichloroethylene 499 Vinyl chloride 850 1.2-cis dichloroethylene Pam jupe Table A-I. Results of 5/23/85 Groundwater Sampling (Continued) 14 aqualab inc. 9909...Sample No. : 08/134621 Matrix: NATURAL WATER Parameter Result Units CC SPECIAL SCAN 1400 ug/L Client I.D.: 14 ERG Sample No.: 08/134622 Matrix

Status of groundwater quality in the Coastal Los Angeles Basin, 2006-California GAMA Priority Basin Project

USGS Publications Warehouse

Goldrath, Dara; Fram, Miranda S.; Land, Michael; Belitz, Kenneth

2012-01-01

Groundwater quality in the approximately 860-square-mile (2,227-square-kilometer) Coastal Los Angeles Basin study unit (CLAB) was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study area is located in southern California in Los Angeles and Orange Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA CLAB study was designed to provide a spatially unbiased assessment of the quality of untreated (raw) groundwater in the primary aquifer system. The assessment is based on water-quality and ancillary data collected in 2006 by the USGS from 69 wells and on water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system was defined by the depth interval of the wells listed in the CDPH database for the CLAB study unit. The quality of groundwater in the primary aquifer system may be different from that in the shallower or deeper water-bearing zones; shallow groundwater may be more vulnerable to surficial contamination. This study assesses the status of the current quality of the groundwater resource by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources in the primary aquifer system of the CLAB study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than (>) 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to (≤) 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic and special-interest constituents [perchlorate, N-nitrosodimethylamine (NDMA), 1,2,3-trichloropropane (1,2,3-TCP), and 1,4-dioxane] were classified as "high" (relative-concentration>1.0), "moderate" (0.5status assessment for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifer system with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifer system with moderate and low relative-concentrations, respectively. Two statistical approaches-grid-based and spatially weighted-were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the CLAB study unit (within 90-percent confidence intervals). Inorganic constituents with human-health benchmarks were detected at high relative-concentrations in 5.6 percent of the primary aquifer system and moderate in 26 percent. High aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of arsenic (1.9 percent), nitrate (1.9 percent), and uranium (1.2 percent). Inorganic constituents with secondary maximum contaminant levels (SMCL) were detected at high relative-concentrations in 18 percent of the primary aquifer system and moderate in 47 percent. The constituents present at high relative-concentrations included total dissolved solids (1.9 percent), manganese (15 percent), and iron (9.4 percent). Relative-concentrations of organic constituents (one or more) were high in 3.7 percent, and moderate in 13 percent, of the primary aquifer system. The high aquifer-scale proportion of organic constituents primarily reflected high aquifer-scale proportions of solvents, including trichloroethene (TCE; 1.7 percent), perchloroethene (PCE; 1.1 percent), and carbon tetrachloride (1.0 percent). Of the 204 organic constituents analyzed, 44 constituents were detected. Eleven organic constituents had detection frequencies of greater than 10 percent: the trihalomethanes chloroform and bromodichloromethane, the solvents TCE, PCE, cis-1,2-dichloroethene, and 1,1-dichloroethene, the herbicides atrazine, simazine, prometon, and tebuthiuron, and the gasoline additive methyl tert-butyl ether (MTBE). Most detections were at low relative-concentrations. The special-interest constituent perchlorate was detected at high relative-concentrations in 0.5 percent of the primary aquifer system, and at moderate relative-concentrations in 35 percent. The special-interest constituent 1,4-dioxane was detected at high relative-concentrations, but an insufficient number of samples was analyzed to provide a representative estimate of aquifer-scale proportion.

Preliminary assessment of the occurrence and possible sources of MTBE in groundwater in the United States, 1993-1994

USGS Publications Warehouse

Squillace, P.J.; Zogorski, J.S.; Wilber, W.G.; Price, C.V.

1996-01-01

The 1990 Clean Air Act Amendments require fuel oxygenates to be added to gasoline used in some metropolitan areas to reduce atmospheric concentrations of carbon monoxide or ozone. Methyl tert-butyl ether (MTBE) is the most commonly used fuel oxygenate and is a relatively new gasoline additive. Nevertheless, out of 60 volatile organic chemicals analyzed, MTBE was the second most frequently detected chemical in samples of shallow ambient groundwater from urban areas that were collected during 1993-1994 aspart of the U.S. Geological Survey's National Water-Quality Assessment program. Samples were collected from five drinking water wells, 12 springs, and 193 monitoring wells in urban areas. No MTBE was detected in drinking water wells. At a reporting level of 0.2 ??g/L, MTBE was detected most frequently in shallow groundwater from urban areas (27% of 210 wells and springs sampled in eight areas) as compared to shallow groundwater from agricultural areas (1.3% of 549 wells sampled in 21 areas) or deeper groundwater from major aquifers (1.0% of 412 wells sampled in nine areas). Only 3% of the shallow wells sampled in urban areas had concentrations of MTBE that exceed 20 ??g/L, which is the estimated lower limit of the United States Environmental Protection Agency draft drinking water health advisory. Because MTBE is persistent and mobile in groundwater, it can move from shallow to deeper aquifers with time. In shallow urban groundwater, MTBE generally was not found with benzene, toluene, ethylbenzene, or xylene (BTEX) compounds, which commonly are associated with gasoline spills. This disassociation causes uncertainty as to the source of MTBE. Possible sources of MTBE in groundwater include point sources, such as leaking storage tanks, and non-point sources, such as recharge of precipitation and stormwater runoff.

Status of groundwater quality in the Upper Santa Ana Watershed, November 2006--March 2007--California GAMA Priority Basin Project

USGS Publications Warehouse

Kent, Robert; Belitz, Kenneth

2012-01-01

Groundwater quality in the approximately 1,000-square-mile (2,590-square-kilometer) Upper Santa Ana Watershed (USAW) study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in southern California in Riverside and San Bernardino Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The GAMA USAW study was designed to provide a spatially unbiased assessment of untreated groundwater quality within the primary aquifer systems in the study unit. The primary aquifer systems (hereinafter, primary aquifers) are defined as the perforation interval of wells listed in the California Department of Public Health (CDPH) database for the USAW study unit. The quality of groundwater in shallower or deeper water-bearing zones may differ from that in the primary aquifers; shallower groundwater may be more vulnerable to surficial contamination. The assessment is based on water-quality and ancillary data collected by the U.S. Geological Survey (USGS) from 90 wells during November 2006 through March 2007, and water-quality data from the CDPH database. The status of the current quality of the groundwater resource was assessed based on data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. The status assessment is intended to characterize the quality of groundwater resources within the primary aquifers of the USAW study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal or California regulatory or non-regulatory benchmarks for drinking-water quality. A relative-concentration greater than (>) 1.0 indicates a concentration above a benchmark, and a relative-concentration less than or equal to (≤) 1.0 indicates a concentration equal to or less than a benchmark. Organic and special-interest constituent relative-concentrations were classified as "high" (> 1.0), "moderate" (0.1 1.0), "moderate" (0.5 < relative-concentration ≤ 1.0), or "low" ( ≤ 0.5). Aquifer-scale proportion was used as the primary metric in the status assessment for evaluating regional-scale groundwater quality. Aquifer-scale proportions are defined as the percentage of the area of the primary aquifer system with concentrations above or below specified thresholds relative to regulatory or aesthetic benchmarks. High aquifer-scale proportion is defined as the percentage of the area of the primary aquifers with a relative-concentration greater than 1.0 for a particular constituent or class of constituents; percentage is based on an areal, rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifers with moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportions for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the USAW study unit (within 90-percent confidence intervals). Inorganic constituents with human-health benchmarks had relative-concentrations that were high in 32.9 percent of the primary aquifers, moderate in 29.3 percent, and low in 37.8 percent. The high aquifer-scale proportion of these inorganic constituents primarily reflected high aquifer-scale proportions of nitrate (high relative-concentration in 25.3 percent of the aquifer), although seven other inorganic constituents with human-health benchmarks also were detected at high relative-concentrations in some percentage of the aquifer: arsenic, boron, fluoride, gross alpha activity, molybdenum, uranium, and vanadium. Perchlorate, as a constituent of special interest, was evaluated separately from other inorganic constituents, and had high relative-concentrations in 11.1 percent, moderate in 53.3 percent, and low or not detected in 35.6 percent of the primary aquifers. In contrast to the inorganic constituents, relative-concentrations of organic constituents (one or more) were high in 6.7 percent, moderate in 11.1 percent, and low or not detected in 82.2 percent of the primary aquifers. Of the 237 organic and special-interest constituents analyzed for, 39 constituents were detected (21 VOCs, 13 pesticides, 3 pharmaceuticals, and 2 constituents of special interest). All of the detected VOCs had health-based benchmarks, and five of these—1,1-dichloroethene, 1,2-dibromo-3-chloropropane (DBCP), tetrachloroethene (PCE), carbon tetrachloride, and trichloroethene (TCE)—were detected in at least one sample at a concentration above a benchmark (high relative-concentration). Seven of the 13 pesticides had health-based benchmarks, and none were detected above these benchmarks (no high relative-concentrations). Pharmaceuticals do not have health-based benchmarks. Thirteen organic constituents were frequently detected (detected in at least 10 percent of samples without regard to relative-concentrations): bromodichloromethane, chloroform, cis-1,2-dichloroethene, 1,1-dichloroethene, dichlorodifluoromethane (CFC-12), methyl tert-butyl ether (MTBE), PCE, TCE, trichlorofluoromethane (CFC-11), atrazine, bromacil, diuron, and simazine.

Conceptualization of the predevelopment groundwater flow system and transient water-level responses in Yucca Flat, Nevada National Security Site, Nevada

USGS Publications Warehouse

Fenelon, Joseph M.; Sweetkind, Donald S.; Elliott, Peggy E.; Laczniak, Randell J.

2012-01-01

Contaminants introduced into the subsurface of Yucca Flat, Nevada National Security Site, by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas and into the accessible environment is greatest by groundwater transport. The primary hydrologic control on this transport is evaluated and examined through a set of contour maps developed to represent the hydraulic-head distribution within the two major aquifer systems underlying the area. Aquifers and confining units within these systems were identified and their extents delineated by merging and analyzing hydrostratigraphic framework models developed by other investigators from existing geologic information. Maps of the hydraulic-head distributions in the major aquifer systems were developed from a detailed evaluation and assessment of available water-level measurements. The maps, in conjunction with regional and detailed hydrogeologic cross sections, were used to conceptualize flow within and between aquifer systems. Aquifers and confining units are mapped and discussed in general terms as being one of two aquifer systems: alluvial-volcanic or carbonate. The carbonate aquifers are subdivided and mapped as independent regional and local aquifers, based on the continuity of their component rock. Groundwater flow directions, approximated from potentiometric contours, are indicated on the maps and sections and discussed for the alluvial-volcanic and regional carbonate aquifers. Flow in the alluvial-volcanic aquifer generally is constrained by the bounding volcanic confining unit, whereas flow in the regional carbonate aquifer is constrained by the siliceous confining unit. Hydraulic heads in the alluvial-volcanic aquifer typically range from 2,400 to 2,530 feet and commonly are elevated about 20-100 feet above heads in the underlying regional carbonate aquifer. Flow directions in the alluvial-volcanic aquifer are variable and are controlled by localized areas where small amounts of water can drain into the regional carbonate aquifer. These areas commonly are controlled by geologic structures, such as Yucca fault. Flow in the regional carbonate aquifer generally drains to the center of the basin; from there flow is to the south-southeast out of the study area toward downgradient discharge areas. Southward flow in the regional carbonate aquifer occurs in a prominent potentiometric trough that results from a faulted zone of enhanced permeability centered about Yucca fault. Vertical hydraulic gradients between the aquifer systems are downward throughout the study area; however, flow from the alluvial-volcanic aquifer into the underlying carbonate aquifer is believed to be minor because of the intervening confining unit. Transient water levels were identified and analyzed to understand hydraulic responses to stresses in Yucca Flat. Transient responses have only a minimal influence on the general predevelopment flow directions in the aquifers. The two primary anthropogenic stresses on the groundwater system since about 1950 are nuclear testing and pumping. Most of the potentiometric response in the aquifers to pumping or past nuclear testing is interim and localized. Persistent, long-lasting changes in hydraulic head caused by nuclear testing occur only in confining units where groundwater fluxes are negligible. A third stress on the groundwater system is natural recharge, which can cause minor, short- and long-term changes in water levels. Long-term hydrographs affected by natural recharge, grouped by similar trend, cluster in distinct areas of Yucca Flat and are controlled primarily by spatial differences in local recharge patterns.

The impact of on-site wastewater from high density cluster developments on groundwater quality

NASA Astrophysics Data System (ADS)

Morrissey, P. J.; Johnston, P. M.; Gill, L. W.

2015-11-01

The net impact on groundwater quality from high density clusters of unsewered housing across a range of hydro(geo)logical settings has been assessed. Four separate cluster development sites were selected, each representative of different aquifer vulnerability categories. Groundwater samples were collected on a monthly basis over a two year period for chemical and microbiological analysis from nested multi-horizon sampling boreholes upstream and downstream of the study sites. The field results showed no statistically significant difference between upstream and downstream water quality at any of the study areas, although there were higher breakthroughs in contaminants in the High and Extreme vulnerability sites linked to high intensity rainfall events; these however, could not be directly attributed to on-site effluent. Linked numerical models were then built for each site using HYDRUS 2D to simulate the attenuation of contaminants through the unsaturated zone from which the resulting hydraulic and contaminant fluxes at the water table were used as inputs into MODFLOW MT3D models to simulate the groundwater flows. The results of the simulations confirmed the field observations at each site, indicating that the existing clustered on-site wastewater discharges would only cause limited and very localised impacts on groundwater quality, with contaminant loads being quickly dispersed and diluted downstream due to the relatively high groundwater flow rates. Further simulations were then carried out using the calibrated models to assess the impact of increasing cluster densities revealing little impact at any of the study locations up to a density of 6 units/ha with the exception of the Extreme vulnerability site.

Supporting 3rd-grade students model-based explanations about groundwater: a quasi-experimental study of a curricular intervention

NASA Astrophysics Data System (ADS)

Zangori, Laura; Vo, Tina; Forbes, Cory T.; Schwarz, Christina V.

2017-07-01

Scientific modelling is a key practice in which K-12 students should engage to begin developing robust conceptual understanding of natural systems, including water. However, little past research has explored primary students' learning about groundwater, engagement in scientific modelling, and/or the ways in which teachers conceptualise and cultivate model-based science learning environments. We are engaged in a multi-year project designed to support 3rd-grade students' formulation of model-based explanations (MBE) for hydrologic phenomenon, including groundwater, through curricular and instructional support. In this quasi-experimental comparative study of five 3rd-grade classrooms, we present findings from analysis of students' MBE generated as part of experiencing a baseline curricular intervention (Year 1) and a modelling-enhanced curricular intervention (Year 2). Findings show that students experiencing the latter version of the unit made significant gains in both conceptual understanding and reasoning about groundwater, but that these gains varied by classroom. Overall, student gains from Year 1 to Year 2 were attributed to changes in two of the five classrooms in which students were provided additional instructional supports and scaffolds to enhance their MBE for groundwater. Within these two classrooms, the teachers enacted the Year 2 curriculum in unique ways that reflected their deeper understanding about the practices of modelling. Their enactments played a critical role in supporting students' MBE about groundwater. Study findings contribute to research on scientific modelling in elementary science learning environments and have important implications for teachers and curriculum developers.

Hydrogeology and hydrologic conditions of the Ozark Plateaus aquifer system

USGS Publications Warehouse

Hays, Phillip D.; Knierim, Katherine J.; Breaker, Brian K.; Westerman, Drew A.; Clark, Brian R.

2016-11-23

The hydrogeology and hydrologic characteristics of the Ozark Plateaus aquifer system were characterized as part of ongoing U.S. Geological Survey efforts to assess groundwater availability across the Nation. The need for such a study in the Ozark Plateaus physiographic province (Ozark Plateaus) is highlighted by increasing demand on groundwater resources by the 5.3 million people of the Ozark Plateaus, water-level declines in some areas, and potential impacts of climate change on groundwater availability. The subject study integrates knowledge gained through local investigation within a regional perspective to develop a regional conceptual model of groundwater flow in the Ozark Plateaus aquifer system (Ozark system), a key phase of groundwater availability assessment. The Ozark system extends across much of southern Missouri and northwestern and north-central Arkansas and smaller areas of southeastern Kansas and northeastern Oklahoma. The region is one of the major karst landscapes in the United States, and karst aquifers are predominant in the Ozark system. Groundwater flow is ultimately controlled by aquifer and confining unit lithologies and stratigraphic relations, geologic structure, karst development, and the character of surficial lithologies and regolith mantle. The regolith mantle is a defining element of Ozark Plateaus karst, affecting recharge, karst development, and vulnerability to surface-derived contaminants. Karst development is more advanced—as evidenced by larger springs, hydraulic characteristics, and higher well yields—in the Salem Plateau and in the northern part of the Springfield Plateau (generally north of the Arkansas-Missouri border) as compared with the southern part of the Springfield Plateau in Arkansas, largely due to thinner, less extensive regolith and purer carbonate lithology.Precipitation is the ultimate source of all water to the Ozark system, and the hydrologic budget for the Ozark system includes inputs from recharge, losing-stream sections, and groundwater inflows and losses of water to gaining-stream sections, groundwater withdrawals, and surface-water and groundwater outflows to neighboring systems. Groundwater recharge, estimated by a soil-water-balance model, represents about 24 percent, or 11 inches, of 43.9 inches annual precipitation. Recharge is spatially variable, being greater in the northern Springfield Plateau and Salem Plateau than in the southern Springfield Plateau (generally south of the Arkansas border) because of differences in regolith mantle extent and thickness and carbonate lithology and hydraulic properties. Increased precipitation and decreased agricultural land use during the period 1951 through 2011 increased recharge by approximately 5 percent. Although all Ozark streams have losing, neutral, and gaining sections, they are dominantly gaining and are a net sink for groundwater with nearly 90 percent of groundwater recharge returned to springs and streams. Groundwater pumping is a small but important loss of water in the Ozark system hydrologic budget; water-level declines and local cones of depression have been observed around pumping centers and strong concerns exist over potential effects on stream and spring flow.Data indicate that societal needs for freshwater resources in the Ozark Plateaus will continue to increase and will do so in the context of changing climate and hydrology. Groundwater will continue to be an important part of supporting these societal needs and also local ecosystems. The unique character and hydrogeologic variability across the Ozark system will control how the system responds to future stress. Groundwater of the Ozark system in the northern study area is more dynamic, has greater storage and larger flux, and has greater potential for further development than in the part of the study area south of the Arkansas-Missouri border. Further south in Arkansas, a line exists, roughly defined as 5 miles south of the Springfield Plateau-Boston Mountains boundary, beyond which further extensive municipal or commercial development appears unlikely under current economic and resource-need conditions. A small part of the Ozark system groundwater budget is currently drafted for use, leaving an apparently large component available for further development and use—particularly in the northern Springfield Plateau and Salem Plateau; however, the effects of increased pumping on groundwater’s role in maintaining ecosystems and ecosystem services are not quantitatively well understood, and the close relation between groundwater and surface water highlights the importance of further quantitative assessment.

Contributions of Phosphorus from Groundwater to Streams in the Piedmont, Blue Ridge, and Valley and Ridge Physiographic Provinces, Eastern United States

USGS Publications Warehouse

Denver, Judith M.; Cravotta,, Charles A.; Ator, Scott W.; Lindsey, Bruce D.

2011-01-01

Phosphorus from natural and human sources is likely to be discharged from groundwater to streams in certain geochemical environments. Water-quality data collected from 1991 through 2007 in paired networks of groundwater and streams in different hydrogeologic and land-use settings of the Piedmont, Blue Ridge, and Valley and Ridge Physiographic Provinces in the eastern United States were compiled and analyzed to evaluate the sources, fate, and transport of phosphorus. The median concentrations of phosphate in groundwater from the crystalline and siliciclastic bedrock settings (0.017 and 0.020 milligrams per liter, respectively) generally were greater than the median for the carbonate setting (less than 0.01 milligrams per liter). In contrast, the median concentrations of dissolved phosphate in stream base flow from the crystalline and siliciclastic bedrock settings (0.010 and 0.014 milligrams per liter, respectively) were less than the median concentration for base-flow samples from the carbonate setting (0.020 milligrams per liter). Concentrations of phosphorus in many of the stream base-flow and groundwater samples exceeded ecological criteria for streams in the region. Mineral dissolution was identified as the dominant source of phosphorus in the groundwater and stream base flow draining crystalline or siliciclastic bedrock in the study area. Low concentrations of dissolved phosphorus in groundwater from carbonate bedrock result from the precipitation of minerals and (or) from sorption to mineral surfaces along groundwater flow paths. Phosphorus concentrations are commonly elevated in stream base flow in areas underlain by carbonate bedrock, however, presumably derived from in-stream sources or from upland anthropogenic sources and transported along short, shallow groundwater flow paths. Dissolved phosphate concentrations in groundwater were correlated positively with concentrations of silica and sodium, and negatively with alkalinity and concentrations of calcium, magnesium, chloride, nitrate, sulfate, iron, and aluminum. These associations can result from the dissolution of alkali feldspars containing phosphorus; the precipitation of apatite; the precipitation of calcite, iron hydroxide, and aluminum hydroxide with associated sorption of phosphate ions; and the potential for release of phosphate from iron-hydroxide and other iron minerals under reducing conditions. Anthropogenic sources of phosphate such as fertilizer and manure and processes such as biological uptake, evapotranspiration, and dilution also affect phosphorus concentrations. The phosphate concentrations in surface water were not correlated with the silica concentration, but were positively correlated with concentrations of major cations and anions, including chloride and nitrate, which could indicate anthropogenic sources and effects of evapotranspiration on surface-water quality. Mixing of older, mineralized groundwater with younger, less mineralized, but contaminated groundwater was identified as a critical factor affecting the quality of stream base flow. In-stream processing of nutrients by biological processes also likely increases the phosphorus concentration in surface waters. Potential geologic contributions of phosphorus to groundwater and streams may be an important watershed-management consideration in certain hydrogeologic and geochemical environments. Geochemical controls effectively limit phosphorus transport through groundwater to streams in areas underlain by carbonate rocks; however, in crystalline and siliciclastic settings, phosphorus from mineral or human sources may be effectively transported by groundwater and contribute a substantial fraction to base-flow stream loads.