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Sample records for estimate groundwater flow

  1. Estimation of Groundwater Flow Parameters Using Least Squares

    E-print Network

    Estimation of Groundwater Flow Parameters Using Least Squares K.R. Bailey \\Lambda , B state flow parameters in a groundwater model. We test the approach on numerically generated data algorithm is implemented in parallel using PVM. 1 Introduction The successful modeling of groundwater flow

  2. 3PE: A Tool for Estimating Groundwater Flow Vectors

    EPA Science Inventory

    Evaluation of hydraulic gradients and the associated groundwater flow rates and directions is a fundamental aspect of hydrogeologic characterization. Many methods, ranging in complexity from simple three-point solution techniques to complex numerical models of groundwater flow, ...

  3. Estimate of recharge from radiocarbon dating of groundwater and numerical flow and transport modeling

    E-print Network

    Zhu, Chen

    Estimate of recharge from radiocarbon dating of groundwater and numerical flow and transport of radioactive waste repositories. A case study of a regional aquifer in northeastern Arizona shows the recharge. In this paper, we use 14 C dating of groundwater from the saturated zone and a linked numerical flow

  4. Radiocarbon Determinations for Estimating Groundwater Flow Velocities in Central Florida.

    PubMed

    Hanshaw, B B; Back, W; Rubin, M

    1965-04-23

    Carbon-14 activity was determined from HCO(3)(-) in samples of groundwater obtained from the principal artesian aquifer in Florida. From these data the "age" of water obtained from a series of wells, each progressively farther down gradient on the piezometric surface, was established. Relative carbon-14 ages indicated a velocity of groundwater movement of 23 feet (7 meters) per year for about 85 miles (137 kilometers) of travel. A velocity of 23 feet per year was calculated independently from Darcy's law. PMID:17842840

  5. Estimating evapotranspiration and groundwater flow from water-table fluctuations for a general wetland scenario

    USGS Publications Warehouse

    Carlson Mazur, Martha L.; Michael J. Wiley; Douglas A. Wilcox

    2015-01-01

    The use of diurnal water-table fluctuation methods to calculate evapotranspiration (ET) and groundwater flow is of increasing interest in ecohydrological studies. Most studies of this type, however, have been located in riparian wetlands of semi-arid regions where groundwater levels are consistently below topographic surface elevations and precipitation events are infrequent. Current methodologies preclude application to a wider variety of wetland systems. In this study, we extended a method for estimating sub-daily ET and groundwater flow rates from water-level fluctuations to fit highly dynamic, non-riparian wetland scenarios. Modifications included (1) varying the specific yield to account for periodic flooded conditions and (2) relating empirically derived ET to estimated potential ET for days when precipitation events masked the diurnal signal. To demonstrate the utility of this method, we estimated ET and groundwater fluxes over two growing seasons (2006–2007) in 15 wetlands within a ridge-and-swale wetland complex of the Laurentian Great Lakes under flooded and non-flooded conditions. Mean daily ET rates for the sites ranged from 4.0?mm?d?1 to 6.6?mm?d?1. Shallow groundwater discharge rates resulting from evaporative demand ranged from 2.5?mm?d?1 to 4.3?mm?d?1. This study helps to expand our understanding of the evapotranspirative demand of plants under various hydrologic and climate conditions.

  6. Water-balance and groundwater-flow estimation for an arid environment: San Diego region, California

    NASA Astrophysics Data System (ADS)

    Flint, L. E.; Flint, A. L.; Stolp, B. J.; Danskin, W. R.

    2012-03-01

    The coastal-plain aquifer that underlies the San Diego City metropolitan area in southern California is a groundwater resource. The understanding of the region-wide water balance and the recharge of water from the high elevation mountains to the east needs to be improved to quantify the subsurface inflows to the coastal plain in order to develop the groundwater as a long term resource. This study is intended to enhance the conceptual understanding of the water balance and related recharge processes in this arid environment by developing a regional model of the San Diego region and all watersheds adjacent or draining to the coastal plain, including the Tijuana River basin. This model was used to quantify the various components of the water balance, including semi-quantitative estimates of subsurface groundwater flow to the coastal plain. Other approaches relying on independent data were used to test or constrain the scoping estimates of recharge and runoff, including a reconnaissance-level groundwater model of the San Diego River basin, one of three main rivers draining to the coastal plain. Estimates of subsurface flow delivered to the coastal plain from the river basins ranged from 12.3 to 28.8 million m3 yr-1 from the San Diego River basin for the calibration period (1982-2009) to 48.8 million m3 yr-1 from all major river basins for the entire coastal plain for the long-term period 1940-2009. This range of scoping estimates represents the impact of climatic variability and realistically bounds the likely groundwater availability, while falling well within the variable estimates of regional recharge. However, the scarcity of physical and hydrologic data in this region hinders the exercise to narrow the range and reduce the uncertainty.

  7. Estimation of regional-scale groundwater flow properties in the Bengal Basin of India and Bangladesh

    USGS Publications Warehouse

    Michael, H.A.; Voss, C.I.

    2009-01-01

    Quantitative evaluation of management strategies for long-term supply of safe groundwater for drinking from the Bengal Basin aquifer (India and Bangladesh) requires estimation of the large-scale hydrogeologic properties that control flow. The Basin consists of a stratified, heterogeneous sequence of sediments with aquitards that may separate aquifers locally, but evidence does not support existence of regional confining units. Considered at a large scale, the Basin may be aptly described as a single aquifer with higher horizontal than vertical hydraulic conductivity. Though data are sparse, estimation of regional-scale aquifer properties is possible from three existing data types: hydraulic heads, 14C concentrations, and driller logs. Estimation is carried out with inverse groundwater modeling using measured heads, by model calibration using estimated water ages based on 14C, and by statistical analysis of driller logs. Similar estimates of hydraulic conductivities result from all three data types; a resulting typical value of vertical anisotropy (ratio of horizontal to vertical conductivity) is 104. The vertical anisotropy estimate is supported by simulation of flow through geostatistical fields consistent with driller log data. The high estimated value of vertical anisotropy in hydraulic conductivity indicates that even disconnected aquitards, if numerous, can strongly control the equivalent hydraulic parameters of an aquifer system. ?? US Government 2009.

  8. Groundwater Sources in a Desert Watershed (Tule Basin, Nevada) - Estimates of Recharge and Interbasin Flow from Groundwater 14C Patterns and Deviations from a Local Paleoclimate Archive

    NASA Astrophysics Data System (ADS)

    Hagedorn, B.; Bushner, G. L.

    2014-12-01

    Estimating maximum sustainable groundwater extraction rates in the hydrologically interconnected watersheds of the Deep Regional Carbonate Aquifer (DRCA) of the southwestern United States is difficult as water enters fractured aquifers via a combination of local recharge and interbasin flow. As a result, over-extraction may impact water availability on local and regional scales. In this study, a combination of geochemical data from groundwater and vein calcite samples enabled rate of local recharge and interbasin flow in the remote Tule Desert watershed in southeastern Nevada to be quantified. Groundwater 14C age gradients below the water table in 3 multi-level well clusters indicate recharge rates of 1 mm/yr to 2 mm/yr which correspond to a maximum sustainable yield of 5 x 10-4 km3/yr to 1 x 10-3 km3/yr. This is less than previous estimates derived from different methods (e.g., Cl mass balance, water budget modeling) and probably reflects uncertainties in the applied effective porosity values and increasing horizontal interbasin flow components at greater depths below the water table. The deviation of the groundwater 𝛿18O time-series pattern for the Pleistocene-Holocene transition from that of the Devils Hole vein calcite (which is considered a reliable proxy for local climate change) combined with the regional groundwater 𝛿18O gradient allows interbasin flow rates of northerly derived groundwater to be estimated. The reported rates (61.2 m/yr - 101 m/yr) are slightly higher than those derived upon Darcy's Law, but indicate hydraulic conductivity values strikingly similar to those obtained from pump tests conducted elsewhere in the DRCA province. These data may therefore provide the unique opportunity to predict basin-wide groundwater recharge (and sustainable yield) via groundwater flow model calibration based on set hydraulic gradient and conductivity parameters.

  9. Relative efficiency of four parameter-estimation methods in steady-state and transient ground-water flow models

    USGS Publications Warehouse

    Hill, M.C.

    1990-01-01

    Parameters in numerical ground-water flow models have been successfully estimated using nonlinear-optimization methods such as the modified Gauss-Newton (GN) method and conjugate-direction methods. This paper investigates the relative efficiency of GN and three conjugate-direction parameter-estimation methods on two-dimensional, steady-state and transient ground-water flow test cases. The steady-state test cases are included to compare the performance of the algorithm with published examples. The three conjugate-direction methods are the Fletcher-Reeves (FR) and quasi-Newton (QN) regression methods, and combination Fletcher-Reeves quasi-Newton (FR-QN). All three are combined with Newton's method of calculating step size. The numerical ground-water flow model is described by McDonald and Harbaugh.

  10. Estimated Ground-Water Withdrawals from the Death Valley Regional Flow System, Nevada and California, 1913-98

    USGS Publications Warehouse

    Moreo, Michael T.; Halford, Keith J.; La Camera, Richard J.; Laczniak, Randell J.

    2003-01-01

    Ground-water withdrawals from 1913 through 1998 from the Death Valley regional flow system have been compiled to support a regional, three-dimensional, transient ground-water flow model. Withdrawal locations and depths of production intervals were estimated and associated errors were reported for 9,300 wells. Withdrawals were grouped into three categories: mining, public-supply, and commercial water use; domestic water use; and irrigation water use. In this report, groupings were based on the method used to estimate pumpage. Cumulative ground-water withdrawals from 1913 through 1998 totaled 3 million acre-feet, most of which was used to irrigate alfalfa. Annual withdrawal for irrigation ranged from 80 to almost 100 percent of the total pumpage. About 75,000 acre-feet was withdrawn for irrigation in 1998. Annual irrigation withdrawals generally were estimated as the product of irrigated acreage and application rate. About 320 fields totaling 11,000 acres were identified in six hydrographic areas. Annual application rates for high water-use crops ranged from 5 feet in Penoyer Valley to 9 feet in Pahrump Valley. The uncertainty in the estimates of ground-water withdrawals was attributed primarily to the uncertainty of application rate estimates. Annual ground-water withdrawal was estimated at about 90,000 acre-feet in 1998 with an assigned uncertainty bounded by 60,000 to 130,000 acre-feet.

  11. Estimated Ground-water Withdrawals From the Death Valley Regional Flow System, Nevada and California, 1913-98

    SciTech Connect

    M.T. Moreo; K.J. Halford; R.J. LaCamera; and R.J. Laczniak

    2003-09-30

    Ground-water withdrawals from 1913 through 1998 from the Death Valley regional flow system have been compiled to support a regional,three-dimensional, transient ground-water flow model. Withdrawal locations and depths of production intervals were estimated and associated errors were reported for 9,300 wells. Withdrawals were grouped into three categories: mining, public-supply, and commercial water use; domestic water use; and irrigation water use. In this report, groupings were based on the method used to estimate pumpage. Cumulative ground-water withdrawals from 1913 through 1998 totaled 3 million acre-feet, most of which was used to irrigate alfalfa. Annual withdrawal for irrigation ranged from 80 to almost 100 percent of the total pumpage. About 75,000 acre-feet was withdrawn for irrigation in 1998. Annual irrigation withdrawals generally were estimated as the product of irrigated acreage and application rate. About 320 fields totaling 11,000 acres were identified in six hydrographic areas. Annual application rates for high water-use crops ranged from 5 feet in Penoyer Valley to 9 feet in Pahrump Valley. The uncertainty in the estimates of ground-water withdrawals was attributed primarily to the uncertainty of application rate estimates. Annual ground-water withdrawal was estimated at about 90,000 acre-feet in 1998 with an assigned uncertainty bounded by 60,000 to 130,000 acre-feet.

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

    SciTech Connect

    W.R. Belcher; P.E. Elliott; A.L. Geldon

    2001-12-31

    The Death Valley regional ground-water flow system encompasses an area of about 43,500 square kilometers in southeastern California and southern Nevada. 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.

  13. 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.

  14. Death Valley regional groundwater flow model calibration using optimal parameter estimation methods and geoscientific information systems

    USGS Publications Warehouse

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

    1996-01-01

    A three-layer Death Valley regional groundwater flow model was constructed to evaluate potential regional groundwater flow paths in the vicinity of Yucca Mountain, Nevada. Geoscientific information systems were used to characterize the complex surface and subsurface hydrogeological conditions of the area, and this characterization was used to construct likely conceptual models of the flow system. The high contrasts and abrupt contacts of the different hydrogeological units in the subsurface make zonation the logical choice for representing the hydraulic conductivity distribution. Hydraulic head and spring flow data were used to test different conceptual models by using nonlinear regression to determine parameter values that currently provide the best match between the measured and simulated heads and flows.

  15. Estimation of groundwater consumption by phreatophytes using diurnal water table fluctuations: A saturated-unsaturated flow assessment

    USGS Publications Warehouse

    Loheide, S.P., II; Butler, J.J., Jr.; Gorelick, S.M.

    2005-01-01

    Groundwater consumption by phreatophytes is a difficult-to-measure but important component of the water budget in many arid and semiarid environments. Over the past 70 years the consumptive use of groundwater by phreatophytes has been estimated using a method that analyzes diurnal trends in hydrographs from wells that are screened across the water table (White, 1932). The reliability of estimates obtained with this approach has never been rigorously evaluated using saturated-unsaturated flow simulation. We present such an evaluation for common flow geometries and a range of hydraulic properties. Results indicate that the major source of error in the White method is the uncertainty in the estimate of specific yield. Evapotranspirative consumption of groundwater will often be significantly overpredicted with the White method if the effects of drainage time and the depth to the water table on specific yield are ignored. We utilize the concept of readily available specific yield as the basis for estimation of the specific yield value appropriate for use with the White method. Guidelines are defined for estimating readily available specific yield based on sediment texture. Use of these guidelines with the White method should enable the evapotranspirative consumption of groundwater to be more accurately quantified. Copyright 2005 by the American Geophysical Union.

  16. 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.

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

    SciTech Connect

    R.J. Laczniak; J. LaRue Smith; P.E. Elliott; G.A. DeMeo; M.A. Chatigny; G.J. Roemer

    2001-12-31

    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 f or 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.

  18. Systematic Parameter Estimation of a Density-Dependent Groundwater-Flow and Solute-Transport Model

    NASA Astrophysics Data System (ADS)

    Stanko, Z.; Nishikawa, T.; Traum, J. A.

    2013-12-01

    A SEAWAT-based, flow and transport model of seawater-intrusion was developed for the Santa Barbara groundwater basin in southern California that utilizes dual-domain porosity. Model calibration can be difficult when simulating flow and transport in large-scale hydrologic systems with extensive heterogeneity. To facilitate calibration, the hydrogeologic properties in this model are based on the fraction of coarse and fine-grained sediment interpolated from drillers' logs. This approach prevents over-parameterization by assigning one set of parameters to coarse material and another set to fine material. Estimated parameters include boundary conditions (such as areal recharge and surface-water seepage), hydraulic conductivities, dispersivities, and mass-transfer rate. As a result, the model has 44 parameters that were estimated by using the parameter-estimation software PEST, which uses the Gauss-Marquardt-Levenberg algorithm, along with various features such as singular value decomposition to improve calibration efficiency. The model is calibrated by using 36 years of observed water-level and chloride-concentration measurements, as well as first-order changes in head and concentration. Prior information on hydraulic properties is also provided to PEST as additional observations. The calibration objective is to minimize the squared sum of weighted residuals. In addition, observation sensitivities are investigated to effectively calibrate the model. An iterative parameter-estimation procedure is used to dynamically calibrate steady state and transient simulation models. The resulting head and concentration states from the steady-state-model provide the initial conditions for the transient model. The transient calibration provides updated parameter values for the next steady-state simulation. This process repeats until a reasonable fit is obtained. Preliminary results from the systematic calibration process indicate that tuning PEST by using a set of synthesized observations generated from model output reduces execution times significantly. Parameter sensitivity analyses indicate that both simulated heads and chloride concentrations are sensitive to the ocean boundary conductance parameter. Conversely, simulated heads are sensitive to some parameters, such as specific fault conductances, but chloride concentrations are insensitive to the same parameters. Heads are specifically found to be insensitive to mobile domain texture but sensitive to hydraulic conductivity and specific storage. The chloride concentrations are insensitive to some hydraulic conductivity and fault parameters but sensitive to mass transfer rate and longitudinal dispersivity. Future work includes investigating the effects of parameter and texture characterization uncertainties on seawater intrusion simulations.

  19. Groundwater Flow in Mountain Watersheds

    NASA Astrophysics Data System (ADS)

    Allen, Diana; Voeckler, Hendrik; Welch, Laurie

    2014-05-01

    Mountain watersheds are unique high-relief environments that exhibit geological, landscape, climate, and other characteristics that are distinctive from other types of watersheds/basins. As such, they give rise to complex groundwater systems that circulate water over a range of spatial and temporal scales. This presentation highlights the results of two modeling studies that were conducted to investigate deep groundwater flow processes within mountain watersheds in British Columbia, Canada. The first study focuses on a headwater catchment, and demonstrates that extending the model domain into the bedrock and allowing groundwater to exit the catchment does not compromise the calibration. Deep groundwater loss is estimated at up to 6% of the annual water balance. The second study focuses on deep groundwater flow within the mountain block, which contributes to mountain front recharge. Mountain front recharge is an important source of water to valley-bottom aquifers. Mountain front recharge derives from both mountain streams, which gain water as baseflow from deeply circulating groundwater, and mountain block recharge, which is the subsurface discharge of deep groundwater from the bedrock mountain block to the valley bottom sediments. Baseflow in the mountain streams is found to be sensitive to changes in groundwater recharge across the mountain block.

  20. Estimation of groundwater use for a groundwater-flow model of the Lake Michigan Basin and adjacent areas, 1864-2005

    USGS Publications Warehouse

    Buchwald, Cheryl A.; Luukkonen, Carol L.; Rachol, Cynthia M.

    2010-01-01

    The U.S. Geological Survey, at the request of Congress, is assessing the availability and use of the Nation's water resources to help characterize how much water is available now, how water availability is changing, and how much water can be expected to be available in the future. The Great Lakes Basin Pilot project of the U.S. Geological Survey national assessment of water availability and use focused on the Great Lakes Basin and included detailed studies of the processes governing water availability in the Great Lakes Basin. One of these studies included the development of a groundwater-flow model of the Lake Michigan Basin. This report describes the compilation and estimation of the groundwater withdrawals in those areas in Wisconsin, Michigan, Indiana, and Illinois that were needed for the Lake Michigan Basin study groundwater-flow model. These data were aggregated for 12 model time intervals spanning 1864 to 2005 and were summarized by model area, model subregion, category of water use, aquifer system, aquifer type, and hydrogeologic unit model layer. The types and availability of information on groundwater withdrawals vary considerably among states because water-use programs often differ in the types of data collected and in the methods and frequency of data collection. As a consequence, the methods used to estimate and verify the data also vary. Additionally, because of the different sources of data and different terminologies applied for the purposes of this report, the water-use data published in this report may differ from water-use data presented in other reports. These data represent only a partial estimate of groundwater use in each state because estimates were compiled only for areas in Wisconsin, Michigan, Indiana, and Illinois within the Lake Michigan Basin model area. Groundwater-withdrawal data were compiled for both nearfield and farfield model areas in Wisconsin and Illinois, whereas these data were compiled primarily for the nearfield model area in Michigan and Indiana. Overall water use for the selected areas in Wisconsin, Michigan, Indiana, and Illinois was less during early time intervals than during more recent intervals, with large increases beginning around the 1960s. Total estimated groundwater withdrawals for model input range from 18.01 million gallons per day (Mgal/d) for interval 1 (1864-1900) to 1,280.25 Mgal/d for interval 12 (2001-5). Withdrawals for the public-supply category make up the majority of the withdrawals in each of the four states. In Wisconsin and Michigan, the second largest withdrawals are for the irrigation category; in Indiana and Illinois, industrial withdrawals account for the second largest withdrawal amounts. The smallest withdrawals are for miscellaneous uses in Wisconsin and irrigation uses in Indiana and Illinois. Estimated groundwater withdrawals in the Southern Lower Peninsula of Michigan, Northeastern Illinois, and the farfield model area are generally larger than in the other model subregions. Withdrawals in Michigan and Indiana are predominantly from the Quaternary aquifer system, whereas withdrawals in Illinois are predominantly from the Cambrian-Ordovician aquifer systems. Withdrawals in Wisconsin are about equal from the Quaternary and Cambrian-Ordovician aquifer systems. Estimated groundwater withdrawals in Michigan and Indiana are predominantly from the unconfined unconsolidated aquifer type. Withdrawals in Illinois are largely from the deep confined bedrock aquifer type, although they decreased considerably in more recent time intervals. Wisconsin withdrawals are about equal from unconfined unconsolidated and deep confined bedrock aquifer types. Groundwater-withdrawal estimates in Wisconsin were compiled for the 47 easternmost counties within the boundary of the Lake Michigan Basin model, of which 32 counties, though not entirely contained, are at least partly within the Lake Michigan Basin. Overall, 6,457 withdrawal locations were estima

  1. Natural Recharge Estimation and Uncertainty Analysis of an Adjudicated Groundwater Basin using a Regional-Scale Groundwater Flow and Subsidence Model

    NASA Astrophysics Data System (ADS)

    Siade, A. J.; Nishikawa, T.; Martin, P.

    2011-12-01

    The Superior Court of California recently ruled that the Antelope Valley groundwater basin is in overdraft-groundwater extractions are in excess of the "safe yield" of the groundwater basin. As defined by the Court, "safe yield is the amount of annual extractions of water from an aquifer over time equal to the amount of water needed to recharge the groundwater aquifer and maintain it in equilibrium, plus any temporary surplus." Natural recharge is an important component of total groundwater recharge in Antelope Valley; however, the exact quantity and distribution of natural recharge is uncertain with estimates ranging from 30,000 to 160,000 acre-feet per year. Weighing the evidence presented by experts, the Court determined that the "safe yield" of the adjudicated area of the basin was 110,000 acre-feet per year. Knowledge of the quantity and distribution of natural recharge is needed to evaluate whether the Court-defined "safe yield" estimate for the basin will minimize additional storage depletion, and related land subsidence, resulting from continued groundwater extraction. The objective of this study is to systematically address the uncertainty in estimates of natural recharge and related aquifer parameters using a groundwater-flow and land-subsidence model with observational data and expert knowledge. Observational data include measured water levels, land-surface deformation, and estimates of transmissivity throughout the basin. An example of expert knowledge is the distribution of artesian conditions for pre-development times. Even though a great wealth of data is available, the problem of non-uniqueness remains present throughout the calibration process. Regularization is used to systematically identify combinations of parameters that can be uniquely estimated as well as to impose expert knowledge onto the parameter identification process. Once the model was calibrated with a reasonable parameter set, the parameter null-space was identified (i.e., the combinations of parameters that cannot be estimated given the available observation data). The majority of the parameter uncertainty is represented by the parameter null-space. Uncertainty in the average annual recharge was evaluated using the null-space Monte-Carlo method. Preliminary results indicate that the total natural recharge ranges between 30,000 and 50,000 acre-ft/yr, which is significantly lower than the Court-determined "safe yield".

  2. Global scale groundwater flow model

    NASA Astrophysics Data System (ADS)

    Sutanudjaja, Edwin; de Graaf, Inge; van Beek, Ludovicus; Bierkens, Marc

    2013-04-01

    As the world's largest accessible source of freshwater, groundwater plays vital role in satisfying the basic needs of human society. It serves as a primary source of drinking water and supplies water for agricultural and industrial activities. During times of drought, groundwater sustains water flows in streams, rivers, lakes and wetlands, and thus supports ecosystem habitat and biodiversity, while its large natural storage provides a buffer against water shortages. Yet, the current generation of global scale hydrological models does not include a groundwater flow component that is a crucial part of the hydrological cycle and allows the simulation of groundwater head dynamics. In this study we present a steady-state MODFLOW (McDonald and Harbaugh, 1988) groundwater model on the global scale at 5 arc-minutes resolution. Aquifer schematization and properties of this groundwater model were developed from available global lithological model (e.g. Dürr et al., 2005; Gleeson et al., 2010; Hartmann and Moorsdorff, in press). We force the groundwtaer model with the output from the large-scale hydrological model PCR-GLOBWB (van Beek et al., 2011), specifically the long term net groundwater recharge and average surface water levels derived from routed channel discharge. We validated calculated groundwater heads and depths with available head observations, from different regions, including the North and South America and Western Europe. Our results show that it is feasible to build a relatively simple global scale groundwater model using existing information, and estimate water table depths within acceptable accuracy in many parts of the world.

  3. Ground-water system, estimation of aquifer hydraulic properties, and effects of pumping on ground-water flow in Triassic sedimentary rocks in and near Lansdale, Pennsylvania

    USGS Publications Warehouse

    Senior, Lisa A.; Goode, Daniel J.

    1999-01-01

    Ground water in Triassic-age sedimentary fractured-rock aquifers in the area of Lansdale, Pa., is used as drinking water and for industrial supply. In 1979, ground water in the Lansdale area was found to be contaminated with trichloroethylene, tetrachloroethylene, and other man-made organic compounds, and in 1989, the area was placed on the U.S. Environmental Protection Agency's (USEPA) National Priority List as the North Penn Area 6 site. To assist the USEPA in the hydrogeological assessment of the site, the U.S. Geological Survey began a study in 1995 to describe the ground-water system and to determine the effects of changes in the well pumping patterns on the direction of ground-water flow in the Lansdale area. This determination is based on hydrologic and geophysical data collected from 1995-98 and on results of the simulation of the regional ground-water-flow system by use of a numerical model.Correlation of natural-gamma logs indicate that the sedimentary rock beds strike generally northeast and dip at angles less than 30 degrees to the northwest. The ground-water system is confined or semi-confined, even at shallow depths; depth to bedrock commonly is less than 20 feet (6 meters); and depth to water commonly is about 15 to 60 feet (5 to 18 meters) below land surface. Single-well, aquifer-interval-isolation (packer) tests indicate that vertical permeability of the sedimentary rocks is low. Multiple-well aquifer tests indicate that the system is heterogeneous and that flow appears primarily in discrete zones parallel to bedding. Preferred horizontal flow along strike was not observed in the aquifer tests for wells open to the pumped interval. Water levels in wells that are open to the pumped interval, as projected along the dipping stratigraphy, are drawn down more than water levels in wells that do not intersect the pumped interval. A regional potentiometric map based on measured water levels indicates that ground water flows from Lansdale towards discharge areas in three drainages, the Wissahickon, Towamencin, and Neshaminy Creeks.Ground-water flow was simulated for different pumping patterns representing past and current conditions. The three-dimensional numerical flow model (MODFLOW) was automatically calibrated by use of a parameter estimation program (MODFLOWP). Steady-state conditions were assumed for the calibration period of 1996. Model calibration indicates that estimated recharge is 8.2 inches (208 millimeters) and the regional anisotropy ratio for the sedimentary-rock aquifer is about 11 to 1, with permeability greatest along strike. The regional anisotropy is caused by up- and down-dip termination of high-permeability bed-oriented features, which were not explicitly simulated in the regional-scale model. The calibrated flow model was used to compare flow directions and capture zones in Lansdale for conditions corresponding to relatively high pumping rates in 1994 and to lower pumping rates in 1997. Comparison of the 1994 and 1997 simulations indicates that wells pumped at the lower 1997 rates captured less ground water from known sites of contamination than wells pumped at the 1994 rates. Ground-water flow rates away from Lansdale increased as pumpage decreased in 1997.A preliminary evaluation of the relation between ground-water chemistry and conditions favorable for the degradation of chlorinated solvents was based on measurements of dissolved-oxygen concentration and other chemical constituents in water samples from 92 wells. About 18 percent of the samples contained less than or equal to 5 milligrams per liter dissolved oxygen, a concentration that indicates reducing conditions favorable for degradation of chlorinated solvents.

  4. U.S. Geological Survey groundwater toolbox, a graphical and mapping interface for analysis of hydrologic data (version 1.0): user guide for estimation of base flow, runoff, and groundwater recharge from streamflow data

    USGS Publications Warehouse

    Barlow, Paul M.; Cunningham, William L.; Zhai, Tong; Gray, Mark

    2015-01-01

    This report is a user guide for the streamflow-hydrograph analysis methods provided with version 1.0 of the U.S. Geological Survey (USGS) Groundwater Toolbox computer program. These include six hydrograph-separation methods to determine the groundwater-discharge (base-flow) and surface-runoff components of streamflow—the Base-Flow Index (BFI; Standard and Modified), HYSEP (Fixed Interval, Sliding Interval, and Local Minimum), and PART methods—and the RORA recession-curve displacement method and associated RECESS program to estimate groundwater recharge from streamflow data. The Groundwater Toolbox is a customized interface built on the nonproprietary, open source MapWindow geographic information system software. The program provides graphing, mapping, and analysis capabilities in a Microsoft Windows computing environment. In addition to the four hydrograph-analysis methods, the Groundwater Toolbox allows for the retrieval of hydrologic time-series data (streamflow, groundwater levels, and precipitation) from the USGS National Water Information System, downloading of a suite of preprocessed geographic information system coverages and meteorological data from the National Oceanic and Atmospheric Administration National Climatic Data Center, and analysis of data with several preprocessing and postprocessing utilities. With its data retrieval and analysis tools, the Groundwater Toolbox provides methods to estimate many of the components of the water budget for a hydrologic basin, including precipitation; streamflow; base flow; runoff; groundwater recharge; and total, groundwater, and near-surface evapotranspiration.

  5. Coupled Modeling of Self Potential and Groundwater Flow to Estimate Permeability Structure of the Elkhorn Fault, South Park, Colorado

    NASA Astrophysics Data System (ADS)

    Ball, L.; Jardani, A.; Revil, A.; Ge, S.; Caine, J.

    2008-12-01

    Faults are commonplace in the subsurface and can have substantial impacts on fluid flow at multiple scales. However, there are few field data on the hydraulic properties of fault zones that can be used to quantify their impact on fluid flow, particularly at well-field to regional scales. These data are lacking in part because hydrologic test data are difficult and costly to collect, their quality is highly dependent on the spatial distribution of available wells, and permeability estimates using these data may not capture the internal heterogeneity of fault zone hydraulic properties, particularly at scales larger than the hydraulic influence of the test itself. Here we explore the advantages of supplementing traditional aquifer test data with electrical geophysical data. Self-potential data were coupled with a steady-state groundwater-flow model of the Elkhorn fault, a Laramide-aged contractional fault that juxtaposes two aquifers in South Park, Colorado; a fractured granite aquifer against the upper arkosic sandstone member of the South Park Formation. This coupled modeling approach allows us to develop estimates of fault zone permeability structure and to explore the sensitivity of the self-potential method to different hydrologic scenarios at this site. Self-potential data were collected along several transects across the Elkhorn fault in the vicinity of five monitoring wells in the hanging wall and footwall. Using the geologic structure defined by co-located electrical resistivity tomography data and geologic descriptions from the wells, a two-dimensional finite- element model was developed with three major geologic components: granite hanging wall, fault zone, and sandstone footwall. In this physical domain, groundwater-flow and electrical models were coupled to examine possible permeability structures of the fault zone. Steady-state water level data from four wells were used to calibrate the groundwater-flow model. The self-potential anomaly resulting from the modeled potentiometric surface was examined and compared to measured self-potential data from across the transect. The permeability structure of the fault zone was adjusted to optimize the model fit to both the hydrological and self-potential data. Through several iterations, possible fault zone permeability structures were identified that satisfy both datasets.

  6. Kauai Groundwater Flow Model

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

    Groundwater flow model for Kauai. Data is from the following sources: Whittier, R. and A.I. El-Kadi. 2014. Human and Environmental Risk Ranking of Onsite Sewage Disposal Systems For the Hawaiian Islands of Kauai, Molokai, Maui, and Hawaii – Final. Prepared by the University of Hawaii, Dept. of Geology and Geophysics for the State of Hawaii Dept. of Health, Safe Drinking Water Branch. September 2014.; and Whittier, R.B., K. Rotzoll, S. Dhal, A.I. El-Kadi, C. Ray, G. Chen, and D. Chang. 2004. Hawaii Source Water Assessment Program Report – Volume IV – Island of Kauai Source Water Assessment Program Report. Prepared for the Hawaii Department of Health, Safe Drinking Water Branch. University of Hawaii, Water Resources Research Center. Updated 2015.

  7. Gradual Variation Analysis for Groundwater Flow

    E-print Network

    Chen, Li

    2010-01-01

    Groundwater flow in Washington DC greatly influences the surface water quality in urban areas. The current methods of flow estimation, based on Darcy's Law and the groundwater flow equation, can be described by the diffusion equation (the transient flow) and the Laplace equation (the steady-state flow). The Laplace equation is a simplification of the diffusion equation under the condition that the aquifer has a recharging boundary. The practical way of calculation is to use numerical methods to solve these equations. The most popular system is called MODFLOW, which was developed by USGS. MODFLOW is based on the finite-difference method in rectangular Cartesian coordinates. MODFLOW can be viewed as a "quasi 3D" simulation since it only deals with the vertical average (no z-direction derivative). Flow calculations between the 2D horizontal layers use the concept of leakage. In this project, we have established a mathematical model based on gradually varied functions for groundwater data volume reconstruction. T...

  8. Estimating groundwater recharge

    USGS Publications Warehouse

    Stonestrom, David A.

    2011-01-01

    Groundwater recharge is the entry of fresh water into the saturated portion of the subsurface part of the hydrologic cycle, the modifier "saturated" indicating that the pressure of the pore water is greater than atmospheric.

  9. Monitoring probe for groundwater flow

    DOEpatents

    Looney, B.B.; Ballard, S.

    1994-08-23

    A monitoring probe for detecting groundwater migration is disclosed. The monitor features a cylinder made of a permeable membrane carrying an array of electrical conductivity sensors on its outer surface. The cylinder is filled with a fluid that has a conductivity different than the groundwater. The probe is placed in the ground at an area of interest to be monitored. The fluid, typically saltwater, diffuses through the permeable membrane into the groundwater. The flow of groundwater passing around the permeable membrane walls of the cylinder carries the conductive fluid in the same general direction and distorts the conductivity field measured by the sensors. The degree of distortion from top to bottom and around the probe is precisely related to the vertical and horizontal flow rates, respectively. The electrical conductivities measured by the sensors about the outer surface of the probe are analyzed to determine the rate and direction of the groundwater flow. 4 figs.

  10. Monitoring probe for groundwater flow

    DOEpatents

    Looney, Brian B. (Aiken, SC); Ballard, Sanford (Albuquerque, NM)

    1994-01-01

    A monitoring probe for detecting groundwater migration. The monitor features a cylinder made of a permeable membrane carrying an array of electrical conductivity sensors on its outer surface. The cylinder is filled with a fluid that has a conductivity different than the groundwater. The probe is placed in the ground at an area of interest to be monitored. The fluid, typically saltwater, diffuses through the permeable membrane into the groundwater. The flow of groundwater passing around the permeable membrane walls of the cylinder carries the conductive fluid in the same general direction and distorts the conductivity field measured by the sensors. The degree of distortion from top to bottom and around the probe is precisely related to the vertical and horizontal flow rates, respectively. The electrical conductivities measured by the sensors about the outer surface of the probe are analyzed to determine the rate and direction of the groundwater flow.

  11. Using remote sensing and GIS techniques to estimate discharge and recharge. fluxes for the Death Valley regional groundwater flow system, USA

    USGS Publications Warehouse

    D'Agnese, F. A.; Faunt, C.C.; Keith, Turner A.

    1996-01-01

    The recharge and discharge components of the Death Valley regional groundwater flow system were defined by remote sensing and GIS techniques that integrated disparate data types to develop a spatially complex representation of near-surface hydrological processes. Image classification methods were applied to multispectral satellite data to produce a vegetation map. This map provided a basis for subsequent evapotranspiration and infiltration estimations. The vegetation map was combined with ancillary data in a GIS to delineate different types of wetlands, phreatophytes and wet playa areas. Existing evapotranspiration-rate estimates were then used to calculate discharge volumes for these areas. A previously used empirical method of groundwater recharge estimation was modified by GIS methods to incorporate data describing soil-moisture conditions, and a recharge potential map was produced. These discharge and recharge maps were readily converted to data arrays for numerical modelling codes. Inverse parameter estimation techniques also used these data to evaluate the reliability and sensitivity of estimated values.

  12. Evaluation of geohydrologic framework, recharge estimates and ground-water flow of the Joshua Tree area, San Bernardino County, California

    USGS Publications Warehouse

    Nishikawa, Tracy; Izbicki, John A.; Hevesi, Joseph A.; Stamos, Christina L.; Martin, Peter

    2005-01-01

    Ground water historically has been the sole source of water supply for the community of Joshua Tree in the Joshua Tree ground-water subbasin of the Morongo ground-water basin in the southern Mojave Desert. The Joshua Basin Water District (JBWD) supplies water to the community from the underlying Joshua Tree ground-water subbasin. The JBWD is concerned with the long-term sustainability of the underlying aquifer. To help meet future demands, the JBWD plans to construct production wells in the adjacent Copper Mountain ground-water subbasin. As growth continues in the desert, there may be a need to import water to supplement the available ground-water resources. In order to manage the ground-water resources and to identify future mitigating measures, a thorough understanding of the ground-water system is needed. The purpose of this study was threefold: (1) improve the understanding of the geohydrologic framework of the Joshua Tree and Copper Mountain ground-water subbasins, (2) determine the distribution and quantity of recharge using field and numerical techniques, and (3) develop a ground-water flow model that can be used to help manage the water resources of the region. The geohydrologic framework was refined by collecting and interpreting water-level and water-quality data, geologic and electric logs, and gravity data. The water-bearing deposits in the Joshua Tree and Copper Mountain ground-water subbasins are Quarternary alluvial deposits and Tertiary sedimentary and volcanic deposits. The Quarternary alluvial deposits were divided into two aquifers (referred to as the 'upper' and the 'middle' alluvial aquifers), which are about 600 feet (ft) thick, and the Tertiary sedimentary and volcanic deposits were assigned to a single aquifer (referred to as the 'lower' aquifer), which is as thick as 1,500 ft. The ground-water quality of the Joshua Tree and Copper Mountain ground-water subbasins was defined by collecting 53 ground-water samples from 15 wells (10 in the Joshua Tree ground-water subbasin and 5 in the Copper Mountain ground-water subbasin) between 1980 and 2002 and analyzing the samples for major ions, nutrients, and selected trace elements. Selected samples also were analyzed for oxygen-18, deuterium, tritium, and carbon-14. The water-quality data indicated that dissolved solids and nitrate concentrations were below regulatory limits for potable water; however, fluoride concentrations in the lower aquifer exceeded regulatory limits. Arsenic concentrations and chromium concentrations were generally below regulatory limits; however, arsenic concentrations measured in water from wells perforated in the lower aquifer exceeded regulatory limits. The carbon-14 activities ranged from 2 to 72 percent modern carbon and are consistent with uncorrected ground-water ages (time since recharge) of about 32,300 to 2,700 years before present. The oxygen-18 and deuterium composition of water sampled from the upper aquifer is similar to the volume-weighted composition of present-day winter precipitation indicating that winter precipitation was the predominant source of ground-water recharge. Field studies, conducted during water years 2001 through 2003 to determine the distribution and quantity of recharge, included installation of instrumented boreholes in selected washes and at a nearby control site. Core material and cuttings from the boreholes were analyzed for physical, chemical, and hydraulic properties. Instruments installed in the boreholes were monitored to measure changes in matric potential and temperature. Borehole data were supplemented with temperature data collected from access tubes installed at additional sites along study washes. Streambed hydraulic properties and the response of instruments to infiltration were measured using infiltrometers. Physical and geochemical data collected away from the stream channels show that direct infiltration of precipitation to depths below the root zone and subsequent gro

  13. Using remote sensing and GIS techniques to estimate discharge and recharge fluxes for the Death Valley regional groundwater flow system, USA

    USGS Publications Warehouse

    D'Agnese, F. A.; Faunt, C.C.; Turner, A.K.

    1996-01-01

    The recharge and discharge components of the Death Valley regional groundwater flow system were defined by techniques that integrated disparate data types to develop a spatially complex representation of near-surface hydrological processes. Image classification methods were applied to multispectral satellite data to produce a vegetation map. The vegetation map was combined with ancillary data in a GIS to delineate different types of wetlands, phreatophytes and wet playa areas. Existing evapotranspiration-rate estimates were used to calculate discharge volumes for these area. An empirical method of groundwater recharge estimation was modified to incorporate data describing soil-moisture conditions, and a recharge potential map was produced. These discharge and recharge maps were readily converted to data arrays for numerical modelling codes. Inverse parameter estimation techniques also used these data to evaluate the reliability and sensitivity of estimated values.The recharge and discharge components of the Death Valley regional groundwater flow system were defined by remote sensing and GIS techniques that integrated disparate data types to develop a spatially complex representation of near-surface hydrological processes. Image classification methods were applied to multispectral satellite data to produce a vegetation map. This map provided a basis for subsequent evapotranspiration and infiltration estimations. The vegetation map was combined with ancillary data in a GIS to delineate different types of wetlands, phreatophytes and wet playa areas. Existing evapotranspiration-rate estimates were then used to calculate discharge volumes for these areas. A previously used empirical method of groundwater recharge estimation was modified by GIS methods to incorporate data describing soil-moisture conditions, and a recharge potential map was produced. These discharge and recharge maps were readily converted to data arrays for numerical modelling codes. Inverse parameter estimation techniques also used these data to evaluate the reliability and sensitivity of estimated values.

  14. Death valley regional ground-water flow model calibration using optimal parameter estimation methods and geoscientific information systems

    USGS Publications Warehouse

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

    1999-01-01

    A regional-scale, steady-state, saturated-zone ground-water flow model was constructed to evaluate potential regional ground-water flow in the vicinity of Yucca Mountain, Nevada. The model was limited to three layers in an effort to evaluate the characteristics governing large-scale subsurface flow. Geoscientific information systems (GSIS) were used to characterize the complex surface and subsurface hydrogeologic conditions of the area, and this characterization was used to construct likely conceptual models of the flow system. Subsurface properties in this system vary dramatically, producing high contrasts and abrupt contacts. This characteristic, combined with the large scale of the model, make zonation the logical choice for representing the hydraulic-conductivity distribution. Different conceptual models were evaluated using sensitivity analysis and were tested by using nonlinear regression to determine parameter values that are optimal, in that they provide the best match between the measured and simulated heads and flows. The different conceptual models were judged based both on the fit achieved to measured heads and spring flows, and the plausibility of the optimal parameter values. One of the conceptual models considered appears to represent the system most realistically. Any apparent model error is probably caused by the coarse vertical and horizontal discretization.A regional-scale, steady-state, saturated-zone ground-water flow model was constructed to evaluate potential regional ground-water flow in the vicinity of Yucca Mountain, Nevada. The model was limited to three layers in an effort to evaluate the characteristics governing large-scale subsurface flow. Geoscientific information systems (GSIS) were used to characterize the complex surface and subsurface hydrogeologic conditions of the area, and this characterization was used to construct likely conceptual models of the flow system. Subsurface properties in this system vary dramatically, producing high contrasts and abrupt contacts. This characteristic, combined with the large scale of the model, make zonation the logical choice for representing the hydraulic-conductivity distribution. Different conceptual models were evaluated using sensitivity analysis and were tested by using nonlinear regression to determine parameter values that are optimal, in that they provide the best match between the measured and simulated heads and flows. The different conceptual models were judged based both on the fit achieved to measured heads and spring flows, and the plausibility of the optimal parameter values. One of the conceptual models considered appears to represent the system most realistically. Any apparent model error is probably caused by the coarse vertical and horizontal discretization.

  15. A hybrid framework for improving recharge and discharge estimation for a three-dimensional groundwater flow model.

    PubMed

    Meyer, Scott C; Lin, Yu-Feng; Roadcap, George S

    2012-01-01

    We employed the ArcGIS plug-in package PRO-GRADE (Lin et al. 2009), developed for zonation of recharge/discharge (R/D) for modeling two-dimensional aquifer systems, to develop alternative R/D zonations for an existing three-dimensional groundwater flow model of a complex hydrogeologic setting. Our process began by intersecting PRO-GRADE output with the existing model's 4-zone R/D representation to develop a model having 12 R/D zones (R12) and then calibrating the resulting model using PEST. We then revised the R12 zonation using supplementary GIS data to develop a 51-zone R/D zonation (R51). From R51, we developed a series of daughter models having 40, 30, 28, and 18 R/D zones by removing zones from R51 if calibration resulted in little change in the zone's starting R/D rate and/or if the model was insensitive to the zone's R/D rate. For these models (R40N, R30N, R28N, and R18N), we used the ArcGIS Nibble tool to rapidly and consistently reassign model cells within eliminated zones of R51 to the zone of the nearest model cell in a retained zone having the same starting value. R12, R51, R40N, R30N, R28N, and R18N are all more accurate than the original model (R4), although improvements relative to stream discharge targets exceeded improvements relative to head targets. The models also executed with better numerical stability and less mass balance discrepancy than R4. These improvements demonstrate that R/D estimation in a complex shallow three-dimensional steady-state model can be improved with PRO-GRADE estimates of R/D when guided by calibration statistics and supplemental geographic data. PMID:21797853

  16. Effects of wetlands creation on groundwater flow

    USGS Publications Warehouse

    Hensel, B.R.; Miller, M.V.

    1991-01-01

    Changes in groundwater flow were observed near four Experimental Wetland Areas (EWAs) constructed along a reach of the Des Plaines River in northeastern Illinois. These changes were observed during monthly monitoring of groundwater elevation in nested piezometers and shallow observation wells before and after the wetlands were filled with water. A numerical model was calibrated with observed data and used to estimate seepage from the wetlands into the Des Plaines River. After the wetlands became operational, groundwater levels in adjacent wells increased by about 0.5m, while water levels in wells distant from the wetlands decreased. The increase in groundwater levels near the wetlands is a result of seepage from the wetlands. Numerical predictions of seepage from the wetlands are 60-150 m3 day-1 for two wetlands situated over sand and gravel and less than 1 m3 day-1 for two wetlands situated over clayey till. The difference in seepage rates is attributed to two factors. First, the hydraulic conductivity of the sand and gravel unit is greater than that of the till, and thus there is less mounding and a greater capacity for transmitting water beneath the wetlands overlying this deposit. Secondly, the wetlands located over till are groundwater flow-through ponds, whereas the wetlands over the sand and gravel are primarily groundwater recharge areas. The model was used to estimate that seepage from the wetlands will double groundwater discharge into the Des Plaines River and a tributary relative to pre-operational discharge from the study area. Overall, the wetlands have acted as a constant head boundary, stabilizing groundwater flow patterns. ?? 1991.

  17. Natural recharge estimation and uncertainty analysis of an adjudicated groundwater basin using a regional-scale flow and subsidence model (Antelope Valley, California, USA)

    NASA Astrophysics Data System (ADS)

    Siade, Adam; Nishikawa, Tracy; Martin, Peter

    2015-09-01

    Groundwater has provided 50-90 % of the total water supply in Antelope Valley, California (USA). The associated groundwater-level declines have led the Los Angeles County Superior Court of California to recently rule that the Antelope Valley groundwater basin is in overdraft, i.e., annual pumpage exceeds annual recharge. Natural recharge consists primarily of mountain-front recharge and is an important component of the total groundwater budget in Antelope Valley. Therefore, natural recharge plays a major role in the Court's decision. The exact quantity and distribution of natural recharge is uncertain, with total estimates from previous studies ranging from 37 to 200 gigaliters per year (GL/year). In order to better understand the uncertainty associated with natural recharge and to provide a tool for groundwater management, a numerical model of groundwater flow and land subsidence was developed. The transient model was calibrated using PEST with water-level and subsidence data; prior information was incorporated through the use of Tikhonov regularization. The calibrated estimate of natural recharge was 36 GL/year, which is appreciably less than the value used by the court (74 GL/year). The effect of parameter uncertainty on the estimation of natural recharge was addressed using the Null-Space Monte Carlo method. A Pareto trade-off method was also used to portray the reasonableness of larger natural recharge rates. The reasonableness of the 74 GL/year value and the effect of uncertain pumpage rates were also evaluated. The uncertainty analyses indicate that the total natural recharge likely ranges between 34.5 and 54.3 GL/year.

  18. Natural recharge estimation and uncertainty analysis of an adjudicated groundwater basin using a regional-scale flow and subsidence model (Antelope Valley, California, USA)

    USGS Publications Warehouse

    Siade, Adam J.; Nishikawa, Tracy; Martin, Peter

    2015-01-01

    Groundwater has provided 50–90 % of the total water supply in Antelope Valley, California (USA). The associated groundwater-level declines have led the Los Angeles County Superior Court of California to recently rule that the Antelope Valley groundwater basin is in overdraft, i.e., annual pumpage exceeds annual recharge. Natural recharge consists primarily of mountain-front recharge and is an important component of the total groundwater budget in Antelope Valley. Therefore, natural recharge plays a major role in the Court’s decision. The exact quantity and distribution of natural recharge is uncertain, with total estimates from previous studies ranging from 37 to 200 gigaliters per year (GL/year). In order to better understand the uncertainty associated with natural recharge and to provide a tool for groundwater management, a numerical model of groundwater flow and land subsidence was developed. The transient model was calibrated using PEST with water-level and subsidence data; prior information was incorporated through the use of Tikhonov regularization. The calibrated estimate of natural recharge was 36 GL/year, which is appreciably less than the value used by the court (74 GL/year). The effect of parameter uncertainty on the estimation of natural recharge was addressed using the Null-Space Monte Carlo method. A Pareto trade-off method was also used to portray the reasonableness of larger natural recharge rates. The reasonableness of the 74 GL/year value and the effect of uncertain pumpage rates were also evaluated. The uncertainty analyses indicate that the total natural recharge likely ranges between 34.5 and 54.3 GL/year.

  19. Groundwater flow into Lake Michigan from Wisconsin

    USGS Publications Warehouse

    Cherkauer, D.S.; Hensel, B.R.

    1986-01-01

    Detailed hydrogeological study has been done at six sites along the Lake Michigan shoreline in Wisconsin. At each site a flux of groundwater to the lake has been calculated for both natural conditions and the existing conditions created by pumping. The values from each site have then been extrapolated to the entire portion of the total shoreline having similar hydrogeology in order to calculate a total flow of groundwater to the lake. Sensitivity analysis with a digital model was used to define limits on the similarity of hydrogeologic conditions. The net flow calculated is 580-880 m3 day-1 km-1 of shoreline, which falls within the previously published range of 110-8200 m3 day-1 km-1. Human activity may have reduced the natural flow as much as 15%. The estimated natural flow is between 7 and 11% of the surface water contribution to the lake from the study area. ?? 1986.

  20. Geothermal properties and groundwater flow estimated with a three-dimensional geological model in a late Pleistocene terrace area, central Japan

    NASA Astrophysics Data System (ADS)

    Funabiki, A.; Takemura, T.; Hamamoto, S.; Komatsu, T.

    2012-12-01

    1. Introduction The ground source heat pump (GSHP) is a highly efficient and renewable energy technology for space heating and cooling, with benefits that include energy conservation and reductions in greenhouse gas emissions. One result of the huge Tohoku-oki earthquake and tsunami and the subsequent nuclear disasters is that GSHPs are receiving more attention from the media and they are being introduced by some local governments. Heat generated by underground GSHP installation, however, can pollute the geothermal environment or change groundwater flow patterns . In this study, we estimated possible effects from the use of GSHPs in the Tokyo area with a three-dimensional (3D) geological model. 2. Geological model The Tokyo Metropolitan Area is surrounded by the Late Pleistocene terraces called the Musashino uplands. The terrace surfaces are densely populated residential areas. One of these surfaces, the Shimosueyohi surface, formed along the Tama River during the last deglacial period. The CRE-NUCHS-1 core (Funabiki et al., 2011) was obtained from this surface, and the lithology, heat transfer coefficients, and chemical characteristics of the sediments were analyzed. In this study, we used borehole log data from a 5 km2 area surrounding the CRE-NUCHS-1 core site to create a 3D geological model. In this area, the Pleistocene Kazusa Group is overlain by terrace gravels and a volcanic ash layer called the Kanto Loam. The terrace gravels occur mainly beneath the Kanda, Kitazawa, and Karasuyama rivers , which flow parallel to the Tama River, whereas away from the rivers , the Kanto Loam directly overlies the Kazusa Group sediments. 3. Geothermal disturbance and groundwater flow Using the geological model, we calculated the heat transfer coefficients and groundwater flow velocities in the sediments. Within the thick terrace gravels, which are at relatively shallow depth (8-20 m), heat transfer coefficients were high and groundwater flow was relatively fast. The amount of disturbance of the geothermal environment and groundwater flow caused by the use of GSHPs, therefore, would depend on the thickness of these gravels. Reference Funabiki, A., Nagoya, K., Kaneki, A., Uemura, K., Kurihara, M., Obara, H., Goto, A., Chiba, T., Naya, T., Ueki, T., and Takemura, T. (2011) Sedimentary facies and physical properties of the sediment core CRE-NUCHS-1 in Setagaya district, Tokyo, central Japan. Abstracts, The 118th Annual Meeting of theGeological Society of Japan. Acknowledgement This work was supported by the Core Research for Evolutional Science and Technology (CREST) program of the Japan Science and Technology Agency (JST).

  1. Groundwater flow across spatial scales: importance for climate modeling

    NASA Astrophysics Data System (ADS)

    Krakauer, Nir Y.; Li, Haibin; Fan, Ying

    2014-03-01

    Current regional and global climate models generally do not represent groundwater flow between grid cells as a component of the water budget. We estimate the magnitude of between-cell groundwater flow as a function of grid cell size by aggregating results from a numerical model of equilibrium groundwater flow run and validated globally. We find that over a broad range of cell sizes spanning that of state-of-the-art regional and global climate models, mean between-cell groundwater flow magnitudes scale with the reciprocal of grid cell length. We also derive this scaling a priori from a simple statistical model of a flow network. We offer operational definitions of ‘significant’ groundwater flow contributions to the grid cell water budget in both relative and absolute terms (between-cell flow magnitude exceeding 10% of local recharge or 10 mm y-1, respectively). Groundwater flow is a significant part of the water budget, as measured by a combined test requiring both relative and absolute significance, over 42% of the land area at 0.1° grid cell size (typical of regional and mesoscale models), decreasing to 1.5% at 1° (typical of global models). Based on these findings, we suggest that between-cell groundwater flow should be represented in regional and mesoscale climate models to ensure realistic water budgets, but will have small effects on water exchanges in current global models. As well, parameterization of subgrid moisture heterogeneity should include the effects of within-cell groundwater flow.

  2. Estimation of groundwater consumption by phreatophytes using diurnal water table fluctuations: A saturated-unsaturated flow assessment

    E-print Network

    Loheide II, Steven P.; Butler, James J. Jr.; Gorelick, Steven M.

    2005-07-27

    [1] Groundwater consumption by phreatophytes is a difficult-to-measure but important component of the water budget in many arid and semiarid environments. Over the past 70 years the consumptive use of groundwater by ...

  3. PARAMETER ESTIMATION IN PETROLEUM AND GROUNDWATER MODELING

    E-print Network

    Ewing, Richard E.

    the location and subsequent remediation of contaminants in groundwater to the optimization of productionPARAMETER ESTIMATION IN PETROLEUM AND GROUNDWATER MODELING R.E. Ewing, M.S. Pilant, J.G. Wade parameters in petroleum and groundwater models. It is not intended to be exhaustive, but rather to give

  4. Comparison of methods for estimating ground-water recharge and base flow at a small watershed underlain by fractured bedrock in the Eastern United States

    USGS Publications Warehouse

    Risser, Dennis W.; Gburek, William J.; Folmar, Gordon J.

    2005-01-01

    This study by the U.S. Geological Survey (USGS), in cooperation with the Agricultural Research Service (ARS), U.S. Department of Agriculture, compared multiple methods for estimating ground-water recharge and base flow (as a proxy for recharge) at sites in east-central Pennsylvania underlain by fractured bedrock and representative of a humid-continental climate. This study was one of several within the USGS Ground-Water Resources Program designed to provide an improved understanding of methods for estimating recharge in the eastern United States. Recharge was estimated on a monthly and annual basis using four methods?(1) unsaturated-zone drainage collected in gravity lysimeters, (2) daily water balance, (3) water-table fluctuations in wells, and (4) equations of Rorabaugh. Base flow was estimated by streamflow-hydrograph separation using the computer programs PART and HYSEP. Estimates of recharge and base flow were compared for an 8-year period (1994-2001) coinciding with operation of the gravity lysimeters at an experimental recharge site (Masser Recharge Site) and a longer 34-year period (1968-2001), for which climate and streamflow data were available on a 2.8-square-mile watershed (WE-38 watershed). Estimates of mean-annual recharge at the Masser Recharge Site and WE-38 watershed for 1994-2001 ranged from 9.9 to 14.0 inches (24 to 33 percent of precipitation). Recharge, in inches, from the various methods was: unsaturated-zone drainage, 12.2; daily water balance, 12.3; Rorabaugh equations with PULSE, 10.2, or RORA, 14.0; and water-table fluctuations, 9.9. Mean-annual base flow from streamflow-hydrograph separation ranged from 9.0 to 11.6 inches (21-28 percent of precipitation). Base flow, in inches, from the various methods was: PART, 10.7; HYSEP Local Minimum, 9.0; HYSEP Sliding Interval, 11.5; and HYSEP Fixed Interval, 11.6. Estimating recharge from multiple methods is useful, but the inherent differences of the methods must be considered when comparing results. For example, although unsaturated-zone drainage from the gravity lysimeters provided the most direct measure of potential recharge, it does not incorporate spatial variability that is contained in watershed-wide estimates of net recharge from the Rorabaugh equations or base flow from streamflow-hydrograph separation. This study showed that water-level fluctuations, in particular, should be used with caution to estimate recharge in low-storage fractured-rock aquifers because of the variability of water-level response among wells and sensitivity of recharge to small errors in estimating specific yield. To bracket the largest range of plausible recharge, results from this study indicate that recharge derived from RORA should be compared with base flow from the Local-Minimum version of HYSEP.

  5. GROUNDWATER FLOW MODELS C. P. Kumar

    E-print Network

    Kumar, C.P.

    GROUNDWATER FLOW MODELS C. P. Kumar Scientist `E1' National Institute of Hydrology Roorkee ­ 247667 (Uttaranchal) 1.0 INTRODUCTION The use of groundwater models is prevalent in the field of environmental science, groundwater models are being applied to predict the transport of contaminants for risk evaluation. In general

  6. 1 INTRODUCTION The modular finitedifference groundwater flow

    E-print Network

    Russell, Thomas F.

    1 INTRODUCTION The modular finite­difference ground­water flow model (MODFLOW) developed by the U­dimensional ground­water systems (McDonald & Harbaugh, 1988, Harbaugh & McDonald, 1996). MOC3D is a solute is optimal for advection­ dominated systems, which are typical of many field problems involving ground­water

  7. Estimates of consumptive use and ground-water return flow and the effect of rising and sustained high river stage on the method of estimation in Cibola Valley, Arizona and California, 1983 and 1984

    USGS Publications Warehouse

    Owen-Joyce, Sandra J.

    1990-01-01

    In Cibola Valley, Arizona, water is pumped from the Colorado River to irrigate crops and to maintain wildlife habitat. Unused water percolates to the water table and, as groundwater, moves downgradient into areas of phreatophytes, into a drainage ditch, out of the flood plain, and back to the river. In 1983 and 1984, groundwater return flow was negligible because in most of Cibola Valley the river lost water to the aquifer. Evapotranspiration was used as an approximation for consumptive use by vegetation. Evapotranspiration was calculated as the sum of the products of the area of vegetation types and water-use rate by vegetation type. Evapotranspiration was estimated to be 70,100 acre-ft in 1983 and 62,600 acre-ft in 1984. These estimates may be in error because of the effect of sustained inundation on the rate of water use by phreatophytes. The effects cannot be quantified and therefore adjustments to rates calculated for dry-surface conditions could not be made. The method of estimating consumptive use of water by vegetation and groundwater return flow is affected by changing conditions during years of rising and sustained high river stage caused by flood-control releases at Parker Dam. Most of the bank storage that will return to the river when the high river stage subsides did not originate as irrigation water. High river stage caused some areas to be flooded directly or raised groundwater levels above the land surface. No crops could be grown in flooded fields. The decreased depth to water and inundation with fresh water resulted in new phreatophyte growth in some areas. In some areas that were flooded, many phreatophytes died. Changes in the inundated and flooded areas throughout the years made it difficult to estimate the evaporation losses from the increased water surface. (USGS)

  8. Geomorphic aspects of groundwater flow

    NASA Astrophysics Data System (ADS)

    LaFleur, Robert G.

    The many roles that groundwater plays in landscape evolution are becoming more widely appreciated. In this overview, three major categories of groundwater processes and resulting landforms are considered: (1) Dissolution creates various karst geometries, mainly in carbonate rocks, in response to conditions of recharge, geologic setting, lithology, and groundwater circulation. Denudation and cave formation rates can be estimated from kinetic and hydraulic parameters. (2) Groundwater weathering generates regoliths of residual alteration products at weathering fronts, and subsequent exhumation exposes corestones, flared slopes, balanced rocks, domed inselbergs, and etchplains of regional importance. Groundwater relocation of dissolved salts creates duricrusts of various compositions, which become landforms. (3) Soil and rock erosion by groundwater processes include piping, seepage erosion, and sapping, important agents in slope retreat and headward gully migration. Thresholds and limits are important in many chemical and mechanical groundwater actions. A quantitative, morphometric approach to groundwater landforms and processes is exemplified by selected studies in carbonate and clastic terrains of ancient and recent origins. Résumé Les rôles variés joués par les eaux souterraines dans l'évolution des paysages deviennent nettement mieux connus. La revue faite ici prend en considération trois grandes catégories de processus liés aux eaux souterraines et les formes associées: (1) La dissolution crée des formes karstiques variées, surtout dans les roches carbonatées, en fonction des conditions d'alimentation, du cadre géologique, de la lithologie et de la circulation des eaux souterraines. Les taux d'érosion et de formation des grottes peuvent être estimés à partir de paramètres cinétiques et hydrauliques. (2) L'érosion par les eaux souterraines donne naissance à des régolites, résidus d'altération sur des fronts d'altération, et l'exhumation résultante fait apparaître des rognons, des pentes qui s'évasent, des roches en équilibre, des inselbergs et des plaines de corrosion d'extension régionale. La migration des sels dissous des eaux souterraines crée des croûtes de compositions variées, qui constituent des paysages particuliers. (3) Les processus d'érosion des sols et des roches par les eaux souterraines comprennent les phénomènes suivants: la chenalisation, l'érosion par suintement, le sapement, qui tous sont des agents notables du recul des versants et d'érosion régressive vers l'amont. Les seuils et les limites sont importants dans de nombreuses actions chimiques et mécaniques des eaux souterraines. Une approche morphométrique quantitative des formes et des processus liés aux eaux souterraines est donnée en exemple à partir d'études choisies dans les terrains carbonatés et détritiques d'origine aussi bien ancienne que récente. Resumen Las aguas subterráneas tienen una importancia fundamental en la evolución de los paisajes geomorfológicos. En este artículo se consideran tres grandes categorías de procesos ligados al agua subterránea y sus correspondientes paisajes resultantes: (1) La disolución crea distintas geometrías kársticas, fundamentalmente en rocas carbonatadas, como respuesta a las condiciones de recarga, condicionantes geológicos, litologías y al propio flujo de agua subterránea. La velocidad de denudación y formación de cavernas se puede estimar a partir de los parámetros cinéticos e hidráulicos. (2) La erosión producida por las aguas subterráneas genera regolitas de alteración residual en los frentes de erosión, con los subsiguientes afloramientos de rocas inalteradas, inselbergs, rocas oscilantes o llanuras de corrosión de carácter regional. La recolocación de las sales disueltas crea costras superficiales de diferente composición. (3) La erosión de rocas y suelos por procesos ligados al agua subterránea, como filtración y arrastre de finos da lugar a un movimiento de retroceso de taludes y barrancos. La existencia de umbrales y lím

  9. Death Valley regional groundwater flow system, Nevada and California-Hydrogeologic framework and transient groundwater flow model

    USGS Publications Warehouse

    : Belcher, Wayne R., (Edited By); Sweetkind, Donald S.

    2010-01-01

    A numerical three-dimensional (3D) transient groundwater flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the groundwater flow system and previous less extensive groundwater flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect groundwater flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley regional groundwater flow system (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the groundwater flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural groundwater discharge occurring through evapotranspiration (ET) and spring flow; the history of groundwater pumping from 1913 through 1998; groundwater recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional groundwater flow system. Groundwater flow in the Death Valley region is composed of several interconnected, complex groundwater flow systems. Groundwater flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional groundwater flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and ET are the dominant natural groundwater discharge processes. Groundwater also is withdrawn for agricultural, commercial, and domestic uses. Groundwater flow in the DVRFS was simulated using MODFLOW-2000, the U.S. Geological Survey 3D finitedifference modular groundwater flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 meters (m) on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins simulated by constant-head boundaries. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient mode

  10. Death Valley regional ground-water flow system, Nevada and California -- hydrogeologic framework and transient ground-water flow model

    USGS Publications Warehouse

    : Belcher, Wayne R., (Edited By)

    2004-01-01

    A numerical three-dimensional (3D) transient ground-water flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the ground-water flow system and previous less extensive ground-water flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect ground-water flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley Regional Ground-Water Flow System (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the ground-water flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural ground-water discharge occurring through evapotranspiration and spring flow; the history of ground-water pumping from 1913 through 1998; ground-water recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional ground-water flow system. Ground-water flow in the Death Valley region is composed of several interconnected, complex ground-water flow systems. Ground-water flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional ground-water flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and evapotranspiration (ET) are the dominant natural ground-water discharge processes. Ground water also is withdrawn for agricultural, commercial, and domestic uses. Ground-water flow in the DVRFS was simulated using MODFLOW-2000, a 3D finite-difference modular ground-water flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 m on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins, also simulated by drains. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient model gener

  11. West Maui Groundwater Flow Model

    SciTech Connect

    Nicole Lautze

    2015-01-01

    Groundwater flow model for West Maui. Data is from the following sources: Whittier, R. and A.I. El-Kadi. 2014. Human and Environmental Risk Ranking of Onsite Sewage Disposal Systems For the Hawaiian Islands of Kauai, Molokai, Maui, and Hawaii – Final. Prepared by the University of Hawaii, Dept. of Geology and Geophysics for the State of Hawaii Dept. of Health, Safe Drinking Water Branch. September 2014; and Whittier, R.B., K. Rotzoll, S. Dhal, A.I. El-Kadi, C. Ray, G. Chen, and D. Chang. 2004. Hawaii Source Water Assessment Program Report – Volume V – Island of Maui Source Water Assessment Program Report. Prepared for the Hawaii Department of Health, Safe Drinking Water Branch. University of Hawaii, Water Resources Research Center. Updated 2008.

  12. Study on the Groundwater Flow along the Seawater / Freshwater Interface

    NASA Astrophysics Data System (ADS)

    Marui, A.; Kusunose, K.

    2003-12-01

    The shape of Seawater / Freshwater Interface is effected by the groundwater flow at the coastal area, and decide the position of submarine groundwater discharge that should be existed everywhere in the world. The hydraulic gradient is too small to estimate the groundwater flow in the area, usually. On the other hand, the groundwater that discharges to the marine have to runs along this interface. And the water discharged to the marine is from the deep zone. That_fs why the water discharges to the marine (runs on the interface) might have many information of the deep zone of groundwater. The Hasunuma Beach Park located on the Kujyukuri Long Beach close to the New Tokyo Int_fl Airport is selected of the study for the groundwater flow along the Seawater / Freshwater Interface. The layered aquifer in the deposited rocks lies in the area, until over than 1000 m depth. The shape of the interface was observed by some kinds of physical sounding from the surface (e.g. specific electricity, AMT method), the logging data in the observation well (EC, T, Flow meter logging, Electric logging etc.) and water quality analysis (incl. Isotopes). And the Flow Meter measurement in the well was done, so that the actual groundwater flow was measured in the aquifer (in the crack of the aquifer, exactly). The observed groundwater flow is thought on the interface and the important element of the shape (angle and depth) of the interface, simultaneously. Two interfaces are found at the well point (200 m onshore). The shape of the interface was also confirmed from a diving work that found the submarine discharge of fresh groundwater at 320 m offshore. The distribution of pressure (hydraulic gradient) in the aquifer and the shape of the interface are made cleared by these tests. The progress expression of the Glover_fs solution was suggested by the study.

  13. Influence of perched groundwater on base flow

    USGS Publications Warehouse

    Niswonger, R.G.; Fogg, G.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%. Copyright 2008 by the American Geophysical Union.

  14. Using groundwater levels to estimate recharge

    USGS Publications Warehouse

    Healy, R.W.; Cook, P.G.

    2002-01-01

    Accurate estimation of groundwater recharge is extremely important for proper management of groundwater systems. Many different approaches exist for estimating recharge. This paper presents a review of methods that are based on groundwater-level data. The water-table fluctuation method may be the most widely used technique for estimating recharge; it requires knowledge of specific yield and changes in water levels over time. Advantages of this approach include its simplicity and an insensitivity to the mechanism by which water moves through the unsaturated zone. Uncertainty in estimates generated by this method relate to the limited accuracy with which specific yield can be determined and to the extent to which assumptions inherent in the method are valid. Other methods that use water levels (mostly based on the Darcy equation) are also described. The theory underlying the methods is explained. Examples from the literature are used to illustrate applications of the different methods.

  15. Groundwater flow and groundwater-stream interaction in fractured and dipping sedimentary rocks

    E-print Network

    Toran, Laura

    . Introduction [2] The rate and direction of groundwater flow at a given location is driven by hydraulic gradientGroundwater flow and groundwater-stream interaction in fractured and dipping sedimentary rocks; revised 28 July 2006; accepted 7 September 2006; published 16 January 2007. [1] Groundwater flow

  16. Groundwater Flow Impacts on Thawing Permafrost Systems

    NASA Astrophysics Data System (ADS)

    Voss, C. I.; McKenzie, J. M.

    2014-12-01

    Results of numerical simulation analysis indicate that where groundwater flows in permafrost landscapes in a warming climate, advective heat transport enhances permafrost thaw rate, increasing transmissivity and the movement of warmer recharge and deep waters. Enhanced flows further increase the rate at which permafrost margins warm and thaw, resulting in positive feedback. Groundwater flow is a significant control on thaw rate and on local and regional patterns of residual permafrost in the landscape. Results indicate that residual permafrost patterns in landscapes with groundwater flow should differ from those in landscapes with little flow. As permafrost thaws from above, a deeper seasonal active zone (the shallow subsurface layer that freezes and thaws annually) develops and more through-going thawed zones (taliks) develop that connect supra- and sub-permafrost zones. The new taliks host additional groundwater flow. Despite this potential for increasing groundwater movement in warming arctic environments, most predictive models of permafrost thaw generally have considered only subsurface heat conduction, not incorporating advective heat transport. To understand these systems and feedbacks, the USGS-SUTRA numerical groundwater code, which models coupled groundwater flow and heat transport, was modified to include freeze/thaw. When temperatures are below freezing, the modeled permeability and thermal properties are dependent on ice saturation, and latent heat of ice formation is included in the energy balance. Simulations of groundwater flow and permafrost thaw were carried out across a hillslope cross section with undulating topography that is initially underlain by a continuous thick permafrost layer. Climate warming is applied with mean air-temperature increase of 0.5 °C per 100 years for 1600 years with constant temperature thereafter. This temperature evolution is superimposed on a seasonal ±10 °C variation that drives yearly freeze/thaw cycles in the shallow subsurface. Simulation results compare changes in permafrost distribution over a few thousand years of climate change due to (1) purely conductive heat transport (with essentially no groundwater flow) and (2) advective-conductive heat transport (with significant groundwater flow).

  17. CONTINUOUSTIME FINITE ELEMENT ANALYSIS OF MULTIPHASE FLOW IN GROUNDWATER HYDROLOGY

    E-print Network

    Rowell, Eric C.

    , Magne Espedal and Richard E. Ewing Abstract. A nonlinear differential system for describing an air for an air­water system in groundwater hydrology, ff = a; w [1], [11], [26]: @(OEae ff s ff ) @t +r \\Delta and phrases. mixed method, finite element, compressible flow, porous media, error estimate, air­water system

  18. Groundwater recharge rate and zone structure estimation using PSOLVER algorithm.

    PubMed

    Ayvaz, M Tamer; Elçi, Alper

    2014-01-01

    The quantification of groundwater recharge is an important but challenging task in groundwater flow modeling because recharge varies spatially and temporally. The goal of this study is to present an innovative methodology to estimate groundwater recharge rates and zone structures for regional groundwater flow models. Here, the unknown recharge field is partitioned into a number of zones using Voronoi Tessellation (VT). The identified zone structure with the recharge rates is associated through a simulation-optimization model that couples MODFLOW-2000 and the hybrid PSOLVER optimization algorithm. Applicability of this procedure is tested on a previously developed groundwater flow model of the Tahtal? Watershed. Successive zone structure solutions are obtained in an additive manner and penalty functions are used in the procedure to obtain realistic and plausible solutions. One of these functions constrains the optimization by forcing the sum of recharge rates for the grid cells that coincide with the Tahtal? Watershed area to be equal to the areal recharge rate determined in the previous modeling by a separate precipitation-runoff model. As a result, a six-zone structure is selected as the best zone structure that represents the areal recharge distribution. Comparison to results of a previous model for the same study area reveals that the proposed procedure significantly improves model performance with respect to calibration statistics. The proposed identification procedure can be thought of as an effective way to determine the recharge zone structure for groundwater flow models, in particular for situations where tangible information about groundwater recharge distribution does not exist. PMID:23746002

  19. Estimated ground-water recharge from streamflow in Fortymile Wash near Yucca Mountain, Nevada

    SciTech Connect

    Savard, C.S.

    1998-10-01

    The two purposes of this report are to qualitatively document ground-water recharge from stream-flow in Fortymile Wash during the period 1969--95 from previously unpublished ground-water levels in boreholes in Fortymile Canyon during 1982--91 and 1995, and to quantitatively estimate the long-term ground-water recharge rate from streamflow in Fortymile Wash for four reaches of Fortymile Wash (Fortymile Canyon, upper Jackass Flats, lower Jackass Flats, and Amargosa Desert). The long-term groundwater recharge rate was estimated from estimates of the volume of water available for infiltration, the volume of infiltration losses from streamflow, the ground-water recharge volume from infiltration losses, and an analysis of the different periods of data availability. The volume of water available for infiltration and ground-water recharge in the four reaches was estimated from known streamflow in ephemeral Fortymile Wash, which was measured at several gaging station locations. The volume of infiltration losses from streamflow for the four reaches was estimated from a streamflow volume loss factor applied to the estimated streamflows. the ground-water recharge volume was estimated from a linear relation between infiltration loss volume and ground-water recharge volume for each of the four reaches. Ground-water recharge rates were estimated for three different periods of data availability (1969--95, 1983--95, and 1992--95) and a long-term ground-water recharge rate estimated for each of the four reaches.

  20. Post processing of zone budgets to generate improved groundwater influx estimates associated with longwall mining.

    PubMed

    Mackie, C D

    2014-01-01

    Impacts of underground longwall mining on groundwater systems are commonly assessed using numerical groundwater flow models that are capable of forecasting changes to strata pore pressures and rates of groundwater seepage over the mine life. Groundwater ingress to a mining operation is typically estimated using zone budgets to isolate relevant parts of a model that represent specific mining areas, and to aggregate flows at nominated times within specific model stress periods. These rates can be easily misinterpreted if simplistic averaging of daily flow budgets is adopted. Such misinterpretation has significant implications for design of underground dewatering systems for a new mine site or it may lead to model calibration errors where measured mine water seepage rates are used as a primary calibration constraint. Improved estimates of groundwater ingress can be made by generating a cumulative flow history from zone budget data, then differentiating the cumulative flow history using a low order polynomial convolved through the data set. PMID:23895016

  1. Composite use of numerical groundwater flow modeling and geoinformatics techniques for monitoring Indus Basin aquifer, Pakistan.

    PubMed

    Ahmad, Zulfiqar; Ashraf, Arshad; Fryar, Alan; Akhter, Gulraiz

    2011-02-01

    The integration of the Geographic Information System (GIS) with groundwater modeling and satellite remote sensing capabilities has provided an efficient way of analyzing and monitoring groundwater behavior and its associated land conditions. A 3-dimensional finite element model (Feflow) has been used for regional groundwater flow modeling of Upper Chaj Doab in Indus Basin, Pakistan. The approach of using GIS techniques that partially fulfill the data requirements and define the parameters of existing hydrologic models was adopted. The numerical groundwater flow model is developed to configure the groundwater equipotential surface, hydraulic head gradient, and estimation of the groundwater budget of the aquifer. GIS is used for spatial database development, integration with a remote sensing, and numerical groundwater flow modeling capabilities. The thematic layers of soils, land use, hydrology, infrastructure, and climate were developed using GIS. The Arcview GIS software is used as additive tool to develop supportive data for numerical groundwater flow modeling and integration and presentation of image processing and modeling results. The groundwater flow model was calibrated to simulate future changes in piezometric heads from the period 2006 to 2020. Different scenarios were developed to study the impact of extreme climatic conditions (drought/flood) and variable groundwater abstraction on the regional groundwater system. The model results indicated a significant response in watertable due to external influential factors. The developed model provides an effective tool for evaluating better management options for monitoring future groundwater development in the study area. PMID:20213054

  2. IN SITU FLOW METERS AROUND A GROUNDWATER CIRCULATION WELL (PAPER)

    EPA Science Inventory

    The primary benefit of groundwater circulation well (GCW) technology is the development of strong vertical flows surrounding the treatment well. The extent of significant vertical flow surrounding a circulation well is difficult to establish from traditional groundwater elevation...

  3. Estimates of tracer-based piston-flow ages of groundwater from selected sites: National Water-Quality Assessment Program, 2006-2010

    USGS Publications Warehouse

    Shapiro, Stephanie D.; Plummer, L. Niel; Busenberg, Eurybiades; Widman, Peggy K.; Casile, Gerolamo C.; Wayland, Julian E.; Runkle, Donna L.

    2012-01-01

    Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: * Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings), * Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply), * Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies, and * Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies. Tracer data were evaluated using documented methods and are presented as aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), and tracer-based piston-flow ages. Selected ancillary data, such as redox data, well-construction data, and major dissolved-gas (N2, O2, Ar, CH4, and CO2) data, also are presented. Recharge temperature was inferred using climate data (approximated by mean annual air temperature plus 1°C [MAAT +1°C]) as well as major dissolved-gas data (N2-Ar-based) where available. The N2-Ar-based temperatures showed significantly more variation than the climate-based data, as well as the effects of denitrification and degassing resulting from reducing conditions. The N2-Ar-based temperatures were colder than the climate-based temperatures in networks where recharge was limited to the winter months when evapotranspiration was reduced. The tracer-based piston-flow ages compiled in this report are provided as a consistent means of reporting the tracer data. The tracer-based piston-flow ages may provide an initial interpretation of age in cases in which mixing is minimal and may aid in developing a basic conceptualization of groundwater age in an aquifer. These interpretations are based on the assumption that tracer transport is by advection only and that no mixing occurs. In addition, it is assumed that other uncertainties are minimized, including tracer degradation, sorption, contamination, or fractionation, and that terrigenic (natural) sources of tracers, and spatially variable atmospheric tracer concentrations are constrained.

  4. Sublacustrine groundwater discharge in esker aquifers; fully integrated groundwater flow modeling compared with novel field techniques

    NASA Astrophysics Data System (ADS)

    Ala-aho, Pertti; Rossi, Pekka M.; Isokangas, Elina; Kløve, Bjørn

    2015-04-01

    Groundwater (GW) discharge to surface water bodies such as streams, lakes and wetlands can greatly affect their water quantity, quality and related aquatic ecology. Therefore better understanding of GW - surface water interaction is needed in integrated management of water resources. Sublacustrine groundwater discharge (SGD) to lakes was studied in a complex unconfined Rokua esker aquifer system. SGD was studied for 12 lakes in the area to better understand water and solute inputs through lake beds and thereby the role of GW on lake water budget and solute concentrations. The locations and fluxes of SGD were simulated using a fully integrated groundwater flow model HydroGeoSphere. The used hydrological simulator allows water to flow and partition into overland and stream flow, evaporation, infiltration, and subsurface discharge into surface water features in a physically-based way, which was needed in simulating SGD of the complex aquifer system. The model was first calibrated for subsurface hydraulic conductivity in steady state using data of measured long-term average groundwater and lake levels and stream baseflow. The model performance in transient simulations was then examined against recorded hydrographs for lake and groundwater levels and stream flow. After model performance was verified, the simulated locations and fluxes of SGD were extracted from the model and compared with results from three independent field methods: airborne thermal imaging, stable isotope water balance and seepage meter measurements. Airborne thermal imaging was used to infer locations of SGD into lakes based on temperature anomalies at lakes shorelines due to discharging cold groundwater. Isotopic composition (H2 and O18) was analysed for lake water, groundwater and the data was used to estimate SGD flux into lakes. Finally, seepage meter measurements were conducted for one of the lakes to establish both locations and fluxes of SGD in detail. The simulated and field-based estimated of SGD fluxes and locations compared favourably between the used methods. General pattern of the observed SGD locations using areal thermal imaging was reproduced by the simulations. Order of magnitude in the SGD fluxes agreed between the simulations and stable isotope method, though the isotope-based estimates were consistently higher. The novelty of work was in identifying and quantifying SGD in an esker aquifer using several field based methods and a state of the art modeling approach. The results confirmed that GW is an important component of lake water balance in the area, and likely plays a significant role in solute inflow to lakes and thereby lake trophy status. The study produced new information water fluxes at groundwater and surface water interface in esker aquifers, which is needed in integrated water resource management of these complex aquifer systems.

  5. 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.

  6. Detecting influential observations in nonlinear regression modeling of groundwater flow

    USGS Publications Warehouse

    Yager, R.M.

    1998-01-01

    Nonlinear regression is used to estimate optimal parameter values in models of groundwater flow to ensure that differences between predicted and observed heads and flows do not result from nonoptimal parameter values. Parameter estimates can be affected, however, by observations that disproportionately influence the regression, such as outliers that exert undue leverage on the objective function. Certain statistics developed for linear regression can be used to detect influential observations in nonlinear regression if the models are approximately linear. This paper discusses the application of Cook's D, which measures the effect of omitting a single observation on a set of estimated parameter values, and the statistical parameter DFBETAS, which quantifies the influence of an observation on each parameter. The influence statistics were used to (1) identify the influential observations in the calibration of a three-dimensional, groundwater flow model of a fractured-rock aquifer through nonlinear regression, and (2) quantify the effect of omitting influential observations on the set of estimated parameter values. Comparison of the spatial distribution of Cook's D with plots of model sensitivity shows that influential observations correspond to areas where the model heads are most sensitive to certain parameters, and where predicted groundwater flow rates are largest. Five of the six discharge observations were identified as influential, indicating that reliable measurements of groundwater flow rates are valuable data in model calibration. DFBETAS are computed and examined for an alternative model of the aquifer system to identify a parameterization error in the model design that resulted in overestimation of the effect of anisotropy on horizontal hydraulic conductivity.

  7. Comparison of Estimated Areas Contributing Recharge to Selected Springs in North-Central Florida by Using Multiple Ground-Water Flow Models

    USGS Publications Warehouse

    Shoemaker, W. Barclay; O'Reilly, Andrew M.; Sepulveda, Nicasio; Williams, Stanley A.; Motz, Louis H.; Sun, Qing

    2004-01-01

    Areas contributing recharge to springs are defined in this report as the land-surface area wherein water entering the ground-water system at the water table eventually discharges to a spring. These areas were delineated for Blue Spring, Silver Springs, Alexander Springs, and Silver Glen Springs in north-central Florida using four regional ground-water flow models and particle tracking. As expected, different models predicted different areas contributing recharge. In general, the differences were due to different hydrologic stresses, subsurface permeability properties, and boundary conditions that were used to calibrate each model, all of which are considered to be equally feasible because each model matched its respective calibration data reasonably well. To evaluate the agreement of the models and to summarize results, areas contributing recharge to springs from each model were combined into composite areas. During 1993-98, the composite areas contributing recharge to Blue Spring, Silver Springs, Alexander Springs, and Silver Glen Springs were about 130, 730, 110, and 120 square miles, respectively. The composite areas for all springs remained about the same when using projected 2020 ground-water withdrawals.

  8. Ground-water flow directions and estimation of aquifer hydraulic properties in the lower Great Miami River Buried Valley aquifer system, Hamilton Area, Ohio

    USGS Publications Warehouse

    Sheets, Rodney A.; Bossenbroek, Karen E.

    2005-01-01

    The Great Miami River Buried Valley Aquifer System is one of the most productive sources of potable water in the Midwest, yielding as much as 3,000 gallons per minute to wells. Many water-supply wells tapping this aquifer system are purposely placed near rivers to take advantage of induced infiltration from the rivers. The City of Hamilton's North Well Field consists of 10 wells near the Great Miami River, all completed in the lower Great Miami River Buried Valley Aquifer System. A well-drilling program and a multiple-well aquifer test were done to investigate ground-water flow directions and to estimate aquifer hydraulic properties in the lower part of the Great Miami River Buried Valley Aquifer System. Descriptions of lithology from 10 well borings indicate varying amounts and thickness of clay or till, and therefore, varying levels of potential aquifer confinement. Borings also indicate that the aquifer properties can change dramatically over relatively short distances. Grain-size analyses indicate an average bulk hydraulic conductivity value of aquifer materials of 240 feet per day; the geometric mean of hydraulic conductivity values of aquifer material was 89 feet per day. Median grain sizes of aquifer material and clay units were 1.3 millimeters and 0.1 millimeters, respectively. Water levels in the Hamilton North Well Field are affected by stream stage in the Great Miami River and barometric pressure. Bank storage in response to stream stage is evident. Results from a multiple-well aquifer test at the well field indicate, as do the lithologic descriptions, that the aquifer is semiconfined in some areas and unconfined in others. Transmissivity and storage coefficient of the semiconfined part of the aquifer were 50,000 feet squared per day and 5x10-4, respectively. The average hydraulic conductivity (450 feet per day) based on the aquifer test is reasonable for glacial outwash but is higher than calculated from grain-size analyses, implying a scale effect. Although the part of the lower Great Miami River Buried Valley Aquifer System where the Hamilton North Well Field is located is semiconfined, unconfined, or locally confined and not directly connected to the Great Miami River, the discontinuity of the clay/till layers beneath the river indicates that other, deeper parts of the aquifer system may be directly connected to the Great Miami River.

  9. Effects of intraborehole flow on groundwater age distribution

    USGS Publications Warehouse

    Zinn, B.A.; Konikow, L.F.

    2007-01-01

    Environmental tracers are used to estimate groundwater ages and travel times, but the strongly heterogeneous nature of many subsurface environments can cause mixing between waters of highly disparate ages, adding additional complexity to the age-estimation process. Mixing may be exacerbated by the presence of wells because long open intervals or long screens with openings at multiple depths can transport water and solutes rapidly over a large vertical distance. The effect of intraborehole flow on groundwater age was examined numerically using direct age transport simulation coupled with the Multi-Node Well Package of MODFLOW. Ages in a homogeneous, anisotropic aquifer reached a predevelopment steady state possessing strong depth dependence. A nonpumping multi-node well was then introduced in one of three locations within the system. In all three cases, vertical transport along the well resulted in substantial changes in age distributions within the system. After a pumping well was added near the nonpumping multi-node well, ages were further perturbed by a flow reversal in the nonpumping multi-node well. Results indicated that intraborehole flow can substantially alter groundwater ages, but the effects are highly dependent on local or regional flow conditions and may change with time. ?? Springer-Verlag 2007.

  10. Groundwater Flow and Solute Movement to Drain Laterals, Western San Joaquin Valley, California: 2. Quantitative Hydrologic Assessment

    NASA Astrophysics Data System (ADS)

    Fio, John L.; Deverel, S. J.

    1991-09-01

    Groundwater flow modeling was used to quantitatively assess the hydrologic processes affecting ground water and solute movement to drain laterals. Modeling results were used to calculate the depth distribution of groundwater flowing into drain laterals at 1.8 m (drain lateral 1) and 2.7 m (drain lateral 2) below land surface. The simulations indicated that under nonirrigated conditions about 89% of the flow in drain lateral 2 was from groundwater originating from depths greater than 6 m below land surface. The deep groundwater has higher selenium concentrations than shallow groundwater. Simulation of irrigated conditions indicates that as recharge (deep percolation) increases, the proportional contribution of deep groundwater to drain lateral flow decreases. Groundwater flow paths and travel times estimated from the simulation results indicate that groundwater containing high concentrations of selenium (greater than 780 ?g L-1) probably will continue to enter drain lateral 2 for decades.

  11. Groundwater flow and solute movement to drain laterals, western San Joaquin Valley, California: 2. Quantitative hydrologic assessment

    USGS Publications Warehouse

    Fio, John L.; Deverel, S.J.

    1991-01-01

    Groundwater flow modeling was used to quantitatively assess the hydrologic processes affecting ground water and solute movement to drain laterals. Modeling results were used to calculate the depth distribution of groundwater flowing into drain laterals at 1.8 m (drain lateral 1) and 2.7 m (drain lateral 2) below land surface. The simulations indicated that under nonirrigated conditions about 89% of the flow in drain lateral 2 was from groundwater originating from depths greater than 6 m below land surface. The deep groundwater has higher selenium concentrations than shallow groundwater. Simulation of irrigated conditions indicates that as recharge (deep percolation) increases, the proportional contribution of deep groundwater to drain lateral flow decreases. Groundwater flow paths and travel times estimated from the simulation results indicate that groundwater containing high concentrations of selenium (greater than 780 ?g L?1) probably will continue to enter drain lateral 2 for decades.

  12. Analytical groundwater modeling flow and contaminant migration

    SciTech Connect

    Walton, W.C.

    1989-01-01

    This book includes four analytical microcomputer programs for simulation and graphing of uncomplicated two-dimensional groundwater flow and contaminant migration situations. Program operation, concepts, techniques, and methods are described in detail. The Basic programs feature simulations of the following features: contaminant source areas and plumes and production and injection wells, drains, and mines. A graphics subprogram displays drawdown and concentration graphs and contour maps.

  13. Pajarito Plateau Groundwater Flow and Transport Modeling Process-Level and Systems Models of Groundwater Flow and

    E-print Network

    Lu, Zhiming

    Pajarito Plateau Groundwater Flow and Transport Modeling 1 Process-Level and Systems Models of Groundwater Flow and Transport Beneath the Pajarito Plateau: Migration of High Explosives from Technical Area Groundwater Modeling Project Systems Model Vadose Zone Model Regional Aquifer Model #12;Pajarito Plateau

  14. Patterns in groundwater chemistry resulting from groundwater flow

    NASA Astrophysics Data System (ADS)

    Stuyfzand, Pieter J.

    Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic-methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15m and of adsorbed marine cations (Na+, K+, and Mg2+) as much as 2500m in the flow direction is shown to correspond with about 5000yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Résumé Les écoulements souterrains influencent les différents types hydrochimiques, parce que l'écoulement réduit le mélange par diffusion, porte les marques chimiques de changements biologiques et anthropiques dans la zone d'alimentation et lessive le système aquifère. Ces types dans leur ensemble sont surtout déterminés par des différences dans le flux d'eau météorique traversant le sous-sol. Dans les "hydrosomes" (masses d'eau d'origine déterminée), les lignes marquant une évolution prograde (séquence de faciès) se développent normalement dans la direction de l'écoulement souterrain : depuis des fluctuations fortes de la qualité de l'eau vers une absence de fluctuations, de polluées vers non polluées, d'acides vers basiques, d'oxygénées vers anoxiques et méthanogènes, depuis des échanges de base inexistants vers des échanges significatifs, de l'eau douce vers l'eau saumâtre. Ceci est montré pour une nappe d'eau douce dans une dune côtière des Pays-Bas. Dans "l'hydrosome", on montre que la disparition du carbonate de calcium par lessivage à plus de 15m et celle de cations adsorbés d'origine marine (Na+, K+ et Mg2+) à plus de 2500m vers l'aval-gradient correspond à environ 5000 ans d'écoulement, depuis que la barrière de la plage avec les dunes s'est mise en place. Les zones d'alimentation ponctuelle dans les dunes sont mises en évidence par l'eau souterraine montrant une plus faible évolution prograde de sa qualité que l'eau souterraine de la dune alentour. L'eau du Rhin utilisée pour la réalimentation artificielle dans les dunes a fourni des types hydrochimiques distincts, qui marquent l'écoulement, le mélange et les âges de l'eau souterraine. Resumen El flujo subterráneo tiene una gran importancia sobre la hidroquímica de un sistema ya que reduce la mezcla por difusión, transporta las huellas químicas y biológicas de las acciones antrópicas en la zona de recarga y drena el sistema acuífero. Las tendencias globales vienen regidas por las diferencias en el flujo de agua meteórica que atraviesa el subsuelo. En un hidrosoma individual (cuerpo de agua de un origen específico), se suele desarrollar la siguiente línea de evolución (secuencia de facies) en la dirección del flujo: de gran a nula fluctuación en la calidad del agua, de agua contaminada a no contaminada, de ácida a básica, de óxica a anóxica-metanogénica, de nulo a importante cambio de base y de agua dulce a salobre. Esto puede verse, por ejemplo, en las aguas dulces presentes en las dunas costeras de Holanda. En este hidrosoma, el lixiviado de carbonato cálcico, hasta 15m, y de cationes de adsorción marina (Na+, K+ and Mg2+), hasta 2500m en la dirección

  15. Regional groundwater flow in hard rocks.

    PubMed

    Pacheco, Fernando A L

    2015-02-15

    The territory of continental Portugal has a geologic history marked by the Hercynian orogeny, and to the north of this country the Hercynian large-scale tectonic structures are typically represented by long and deep NW-SE trending ductile shear zones and NNE-SSW trending fragile faults. These structures are elements of mineral and thermal water circuits that discharge as springs in more than one hundred locations. The purpose of this study is to investigate if these structures are also used by shallower non-mineral groundwater, integrated in a large-scale regional flow system. Using an original combination of water balance and recession flow models, it was possible to calculate catchment turnover times based solely on groundwater discharge rates and recession flow parameters. These times were then used to classify a group of 46 watersheds as closed or open basins, and among the later class to identify source and sink basins, based on innovative interpretations of relationships between turnover time and catchment area. By definition, source basins transfer groundwater to sink basins and altogether form a regional flow system. Using a Geographic Information System, it could be demonstrated the spatial association of open basins to the Hercynian ductile and fragile tectonic structures and hence to classify the basins as discharge cells of a regional flow system. Most of the studied watersheds are sub-basins of the Douro River basin, one of the largest regional catchments in the Iberian Peninsula, being located in its mouth area. Because the largest part of open basins is sink, which by definition tends to dominate in the mouth area of regional catchments, it is proposed as an extension of the studied area conceptual boundaries towards the Douro River basin headwaters, where the corresponding sources could be searched for. PMID:25460951

  16. An integrative approach to groundwater recharge estimation: Application to Jeju Island, Korea

    NASA Astrophysics Data System (ADS)

    Park, C.; Lee, J.; Koo, M.

    2008-12-01

    Groundwater resources in Jeju Island, a volcanic island located in the most southern region of Korea, are the only resources for water use. The island mainly consists of highly permeable volcanic materials and structures such as basaltic rocks and lava conduits. Water from precipitation barely resides on the surface and mostly infiltrates into the aquifers or discharges directly to the ocean. Thus, estimating groundwater recharge is critical to the water resource management in Jeju Island. The groundwater recharge was estimated using a GIS-based water balance model, WetSpass (Water and Energy Transfer between Soil, Plants and Atmosphere under quasi Steady State), and a physically-based groundwater flow model, MODFLOW. The WetSpass model estimates spatially varying groundwater recharge based on the surface dominant geo-spatial input parameters, such as soil property, land use, topography, groundwater depth, and meteorological data. The groundwater flow model estimates recharge by using the parameter estimation technique. Both models are complementary because the water balance equation and the groundwater flow equation are linked by a cell-based data process. The results indicated that the eastern and northern part of the Island showed relatively high values of recharge as compared to the western region. The results also showed that 65% of the total recharge occurred in higher elevations over than 200 m which would be a critical groundwater recharge area. The recharge estimation using coupled model provides more reliable results than the use of a single model and useful information for groundwater resource management and associated legislation.

  17. Assessment of factors influencing groundwater-level change using groundwater flow simulation, considering vertical infiltration from rice-planted and crop-rotated paddy fields in Japan

    NASA Astrophysics Data System (ADS)

    Iwasaki, Yumi; Nakamura, Kimihito; Horino, Haruhiko; Kawashima, Shigeto

    2014-12-01

    Assessing factors that influence groundwater levels such as land use and pumping strategy, is essential to adequately manage groundwater resources. A transient numerical model for groundwater flow with infiltration was developed for the Tedori River alluvial fan (140 km2), Japan. The main water input into the groundwater body in this area is irrigation water, which is significantly influenced by land use, namely paddy and upland fields. The proposed model consists of two models, a one-dimensional (1-D) unsaturated-zone water flow model (HYDRUS-1D) for estimating groundwater recharge and a 3-D groundwater flow model (MODFLOW). Numerical simulation of groundwater flow from October 1975 to November 2009 was performed to validate the model. Simulation revealed seasonal groundwater level fluctuations, affected by paddy irrigation management. However, computational accuracy was limited by the spatiotemporal data resolution of the groundwater use. Both annual groundwater levels and recharge during the irrigation periods from 1975 to 2009 showed long-term decreasing trends. With the decline in rice-planted paddy field area, groundwater recharge cumulatively decreased to 61 % of the peak in 1977. A paddy-upland crop-rotation system could decrease groundwater recharge to 73-98 % relative to no crop rotation.

  18. Groundwater Flooding: Practical Methods for the Estimation of Extreme Groundwater Levels

    NASA Astrophysics Data System (ADS)

    Bichler, A.; Fürst, J.

    2012-04-01

    Floods are in general recognized as a consequence of high flows in surface waters. Only recently awareness has been raised for potential flooding and flood risk from groundwater sources. In particular, information about high groundwater levels is relevant where basements of buildings or vulnerable installations might be affected. Also, the EU Floods Directive addresses the potential flood risk arising from groundwater sources. While the statistical analysis of extreme values is widely used in surface hydrology, there are currently only few studies that consider the specific properties of extreme groundwater levels. The main objective of this investigation is the application of at-site and regional frequency analysis in the field of hydrogeology. Extreme groundwater levels with a given return period (e.g. 100 years) are estimated with the method of L-moments and their uncertainty is quantified. Moreover, software tools are developed in order to make extreme value analysis a feasible technique for practical application by the Austrian Hydrological Service. These tools address demand for user-friendly handling as well as integration and an update of existing and readily derivable data. Lastly, the estimates are regionalized, thus information of extreme groundwater levels and accuracy of estimation can be retrieved at any point of the investigation area. The analysis is applied in four shallow, porous aquifers in Austria, with a total of more than 1000 time series records of groundwater levels, covering 10 - 50 years of observation. Firstly, local frequency analysis (LFA) is performed on a series of annual maximum peaks. The analysis of annual maxima allows for easy handling, but comes with the drawback of requiring 20-30 years of observation as minimum sample size. Due to anthropogenic impacts, natural changes of the hydrologic system, etc. this requirement cannot be met in numerous cases. Hence, the peaks over threshold (POT) approach and regional frequency analysis (RFA) is implemented. Thus, sufficiently large sample size can be derived from shorter time series either by selecting exceedances over a variable threshold (POT), or accounting for data from related observations (RFA, "trading space for time"). The results show, that at-site frequency analysis is applicable at 63% of the records, at which the peaks over threshold method yields more accurate estimates compared to the annual maxima. Regional frequency analysis can be applied at 51% of the samples and results in even further reduction of uncertainty. In the four case studies 12 - 45 % of the investigated area is susceptible to groundwater flood risk, i.e. an event with a return period of 100 years is likely to reach the terrain surface. As one of the outcomes, maps of depth to the groundwater table make it possible to identify areas prone to groundwater flooding or suitable for development at a glance.

  19. Groundwater app to determine flow direction and gradient.

    PubMed

    Morrison, Derek; Munster, Clyde

    2015-01-01

    A computational program, called the groundwater flow calculator, was created to quickly and easily determine the hydraulic gradient and direction of groundwater flow. The groundwater flow calculator automates the hand-drawn process by Ralph Heath in the U.S. Geological Survey (USGS) Water Supply Paper 2220. In addition, a mobile app was developed to allow this procedure to run on a smart phone for use in the field. PMID:24898497

  20. INCORPORATION OF GROUNDWATER FLOW INTO NUMERICAL MODELS AND DESIGN MODELS

    E-print Network

    03/10/99 1 INCORPORATION OF GROUNDWATER FLOW INTO NUMERICAL MODELS AND DESIGN MODELS Jeffrey D-coupled, ground-source heat pumps, groundwater, heat pump, heat exchanger, heat transfer, numerical models transport of heat by moving groundwater may be an important factor in reducing the necessary size of closed

  1. Simulation of salt migrations in density dependent groundwater flow

    E-print Network

    Vuik, Kees

    Simulation of salt migrations in density dependent groundwater flow E.S. van Baaren Master's Thesis for the salt migration in the groundwater underneath the polders near the coast. The problem description of this thesis is to investigate the possibilities of modelling salt migrations in density dependent groundwater

  2. A Comparison of Three Stochastic Approaches for Parameter Estimation and Prediction of Steady-State Groundwater Flow: Nonlocal Moment Equations and Monte Carlo Method Coupled with Ensemble Kalman Filter and Geostatistical Stochastic Inversion.

    NASA Astrophysics Data System (ADS)

    Morales-Casique, E.; Briseño-Ruiz, J. V.; Hernández, A. F.; Herrera, G. S.; Escolero-Fuentes, O.

    2014-12-01

    We present a comparison of three stochastic approaches for estimating log hydraulic conductivity (Y) and predicting steady-state groundwater flow. Two of the approaches are based on the data assimilation technique known as ensemble Kalman filter (EnKF) and differ in the way prior statistical moment estimates (PSME) (required to build the Kalman gain matrix) are obtained. In the first approach, the Monte Carlo method is employed to compute PSME of the variables and parameters; we denote this approach by EnKFMC. In the second approach PSME are computed through the direct solution of approximate nonlocal (integrodifferential) equations that govern the spatial conditional ensemble means (statistical expectations) and covariances of hydraulic head (h) and fluxes; we denote this approach by EnKFME. The third approach consists of geostatistical stochastic inversion of the same nonlocal moment equations; we denote this approach by IME. In addition to testing the EnKFMC and EnKFME methods in the traditional manner that estimate Y over the entire grid, we propose novel corresponding algorithms that estimate Y at a few selected locations and then interpolate over all grid elements via kriging as done in the IME method. We tested these methods to estimate Y and h in steady-state groundwater flow in a synthetic two-dimensional domain with a well pumping at a constant rate, located at the center of the domain. In addition, to evaluate the performance of the estimation methods, we generated four unconditional different realizations that served as "true" fields. The results of our numerical experiments indicate that the three methods were effective in estimating h, reaching at least 80% of predictive coverage, although both EnKF were superior to the IME method. With respect to estimating Y, the three methods reached similar accuracy in terms of the mean absolute value error. Coupling the EnKF methods with kriging to estimate Y reduces to one fourth the CPU time required for data assimilation while both estimation accuracy and uncertainty do not deteriorate significantly.

  3. Ground-water flow and solute transport at a municipal landfill site on Long Island, New York; Part 2, Simulation of ground-water flow

    USGS Publications Warehouse

    Wexler, E.J.; Maus, P.E.

    1988-01-01

    Data on the hydrogeology of a 26-sq-mi area surrounding the Brookhaven landfill site in central Suffolk County were collected as part of a hydrologic investigation of solute transport from the site. These data were used to develop a steady-state groundwater flow model of the upper glacial (water table) aquifer in the area. The model accounts for the leakage through confining units underlying the aquifer, seepage to streams, recharge from precipitation, and pumpage and redistribution of water. Refined estimates of aquifer and confining-unit properties were obtained through model calibrations. Water table altitudes generated by the calibrated model were used to determine groundwater velocities and probable flow paths in the vicinity of the site under long-term average hydrologic conditions. Groundwater velocities and probable flow paths in the study area were calculated from simulated water table altitudes generated by the calibrated flow model. Groundwater at the center of the site flows southeastward at a velocity of 1.1 ft/d. The report is the second in a three part series describing the hydrologic conditions and groundwater quality, groundwater flow, and solute transport in the vicinity of the Brookhaven landfill. (USGS)

  4. Estimated Water Flows in 2005: United States

    SciTech Connect

    Smith, C A; Belles, R D; Simon, A J

    2011-03-16

    Flow charts depicting water use in the United States have been constructed from publicly available data and estimates of water use patterns. Approximately 410,500 million gallons per day of water are managed throughout the United States for use in farming, power production, residential, commercial, and industrial applications. Water is obtained from four major resource classes: fresh surface-water, saline (ocean) surface-water, fresh groundwater and saline (brackish) groundwater. Water that is not consumed or evaporated during its use is returned to surface bodies of water. The flow patterns are represented in a compact 'visual atlas' of 52 state-level (all 50 states in addition to Puerto Rico and the Virgin Islands) and one national water flow chart representing a comprehensive systems view of national water resources, use, and disposition.

  5. Tracing seasonal groundwater contributions to stream flow using a suite of environmental isotopes

    NASA Astrophysics Data System (ADS)

    Pritchard, J. L.; Herczeg, A. L.; Lamontagne, S.

    2003-04-01

    Groundwater discharge to streams is important for delivering essential solutes to maintain ecosystem health and flow throughout dry seasons. However, managing the groundwater components of stream flow is difficult because several sources of water can contribute, including delayed drainage from bank storage and regional groundwater. In this study we assessed the potential for a variety of environmental tracers to discriminate between different sources of water to stream flow. A case study comparing Cl-, delta O-18 &delta H-2, Rn-222 and 87Sr/86Sr to investigate the spatial and temporal variability of groundwater inputs to stream flow was conducted in the Wollombi Brook Catchment (SE Australia). The objectives were to characterise the three potential sources of water to stream flow (surface water, groundwater from the near-stream sandy alluvial aquifer system, and groundwater from the regional sandstone aquifer system) and estimate their relative contributions to stream discharge at flood recession and baseflow. Surface water was sampled at various locations along the Wollombi Brook and from its tributaries during flood recession (Mar-01) and under baseflow conditions (Oct-01). Alluvial groundwater was sampled from a piezometer network and regional groundwater from deeper bores in the lower to mid-catchment biannually over two years to characterise these potential sources of water to stream flow. Chloride identified specific reaches of the catchment that were either subjected to evaporation or received regional groundwater contributions to stream flow. The water isotopes verified which of these reaches were dominated by evaporation versus groundwater contributions. They also revealed that the predominant sources of water to stream flow during flood recession were either rainfall and storm runoff or regional groundwater, and that during baseflow the predominant source of water to stream flow was alluvial groundwater. Radon showed that there was a greater proportion of groundwater contributing to stream flow in the upper part of the catchment than the lower catchment during both flood recession and baseflow. Strontium isotopes showed that regional groundwater contributed less than 10% to stream flow in all parts of the catchment under baseflow conditions.

  6. Effects of linking a soil-water-balance model with a groundwater-flow model

    USGS Publications Warehouse

    Stanton, Jennifer S.; Ryter, Derek W.; Peterson, Steven M.

    2013-01-01

    A previously published regional groundwater-flow model in north-central Nebraska was sequentially linked with the recently developed soil-water-balance (SWB) model to analyze effects to groundwater-flow model parameters and calibration results. The linked models provided a more detailed spatial and temporal distribution of simulated recharge based on hydrologic processes, improvement of simulated groundwater-level changes and base flows at specific sites in agricultural areas, and a physically based assessment of the relative magnitude of recharge for grassland, nonirrigated cropland, and irrigated cropland areas. Root-mean-squared (RMS) differences between the simulated and estimated or measured target values for the previously published model and linked models were relatively similar and did not improve for all types of calibration targets. However, without any adjustment to the SWB-generated recharge, the RMS difference between simulated and estimated base-flow target values for the groundwater-flow model was slightly smaller than for the previously published model, possibly indicating that the volume of recharge simulated by the SWB code was closer to actual hydrogeologic conditions than the previously published model provided. Groundwater-level and base-flow hydrographs showed that temporal patterns of simulated groundwater levels and base flows were more accurate for the linked models than for the previously published model at several sites, particularly in agricultural areas.

  7. Effects of linking a soil-water-balance model with a groundwater-flow model.

    PubMed

    Stanton, Jennifer S; Ryter, Derek W; Peterson, Steven M

    2013-01-01

    A previously published regional groundwater-flow model in north-central Nebraska was sequentially linked with the recently developed soil-water-balance (SWB) model to analyze effects to groundwater-flow model parameters and calibration results. The linked models provided a more detailed spatial and temporal distribution of simulated recharge based on hydrologic processes, improvement of simulated groundwater-level changes and base flows at specific sites in agricultural areas, and a physically based assessment of the relative magnitude of recharge for grassland, nonirrigated cropland, and irrigated cropland areas. Root-mean-squared (RMS) differences between the simulated and estimated or measured target values for the previously published model and linked models were relatively similar and did not improve for all types of calibration targets. However, without any adjustment to the SWB-generated recharge, the RMS difference between simulated and estimated base-flow target values for the groundwater-flow model was slightly smaller than for the previously published model, possibly indicating that the volume of recharge simulated by the SWB code was closer to actual hydrogeologic conditions than the previously published model provided. Groundwater-level and base-flow hydrographs showed that temporal patterns of simulated groundwater levels and base flows were more accurate for the linked models than for the previously published model at several sites, particularly in agricultural areas. PMID:23036222

  8. Application of chlorofluorocarbons (CFCs) to estimate the groundwater age at a headwater wetland in Ichikawa City, Chiba Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Han, Zhiwei; Tang, Changyuan; Piao, Jingqiu; Li, Xing; Cao, Yingjie; Matsumaru, Touma; Zhang, Chipeng

    2014-09-01

    To delineate the groundwater flow system in a basin, the groundwater age was estimated by analyzing chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) in a typical headwater wetland in Ichikawa, Japan. Feasibility of groundwater dating by CFCs was assessed comprehensively based on the concentrations of NO3 -, SO4 2-, Fe2+ and dissolved CH4 in the groundwater, because the CFCs would be degraded under the reduction condition available in a wetland. It was found that the CFC-11 apparent age was much older than that estimated by other CFC species. It showed that CFC-12 and CFC-113 were suitable tracers for groundwater dating because of their stability in the wetland environment. Furthermore, the mixture of groundwater with different age was discussed by CFC-12 and CFC-113 based on the binary mixing model and piston-flow model. As a result, the apparent age of groundwater in the study area is in the range of 38-48 years.

  9. Modelling Water Flow In An Alluvial Groundwater-fed Wetland

    NASA Astrophysics Data System (ADS)

    Joris, I.; Feyen, J.

    Complex hydrological interactions occur within alluvial wetlands as a result of fluxes of water to and from the river, atmospheric fluxes and groundwater interactions. The relative importance of these fluxes and their interaction are responsible for the root zone conditions, which in turn determine the potential for different types of natu- ral vegetation. In this research, field data and numerical modeling are combined to examine the water flow processes occurring in an alluvial wetland and to develop a tool to asses the sensitivity of root zone conditions to changes in hydrological bound- ary conditions. The investigated field site is a wetland along the river Dijle with a typical micro-topography with natural levees along the river and depressions further from the river. It is a highly dynamical system with ground water amplitudes ranging from 1,5 meters close to the river to 0,5 meters in the floodplain depression. Along a transect perpendicular to the river, groundwater level and soil moisture content have been monitored for a period of two years. Groundwater inflow at the site is estimated from measurements of nested piezometers, from a regional groundwater model and from recorded soil temperature profiles. Soil hydraulic parameters are measured in the laboratory on undisturbed field cores. Saturated soil moisture contents show a sys- tematic variation with distance from the river, consistent with the observed textural variation typical for alluvial plains. The SWMS-2D code for simulating water flow in two-dimensional variably saturated media is used to reconstruct pressure head and moisture content distributions along the transect. The boundary conditions of the sim- ulation domain are determined by piezometric level in the depression, river stage on the other side, the groundwater inflow from the shallow aquifer at the bottom and rainfall/evapotranspiration at the top of the domain. Scaling factors are included in the model to allow linear variations of the hydraulic curves over the domain and reflect the observed trend in the field. A MATLAB-routine is developed in order to allow in- verse optimization of the hydraulic parameters against measured groundwater levels. Results show that the model is capable of describing the groundwater dynamics fairly well and that the introduction of scaling factors results in a significant improvement of the predicted soil moisture profiles.

  10. Uncertainty in global groundwater storage estimates in a Total Groundwater Stress framework

    NASA Astrophysics Data System (ADS)

    Richey, Alexandra S.; Thomas, Brian F.; Lo, Min-Hui; Famiglietti, James S.; Swenson, Sean; Rodell, Matthew

    2015-07-01

    Groundwater is a finite resource under continuous external pressures. Current unsustainable groundwater use threatens the resilience of aquifer systems and their ability to provide a long-term water source. Groundwater storage is considered to be a factor of groundwater resilience, although the extent to which resilience can be maintained has yet to be explored in depth. In this study, we assess the limit of groundwater resilience in the world's largest groundwater systems with remote sensing observations. The Total Groundwater Stress (TGS) ratio, defined as the ratio of total storage to the groundwater depletion rate, is used to explore the timescales to depletion in the world's largest aquifer systems and associated groundwater buffer capacity. We find that the current state of knowledge of large-scale groundwater storage has uncertainty ranges across orders of magnitude that severely limit the characterization of resilience in the study aquifers. Additionally, we show that groundwater availability, traditionally defined as recharge and redefined in this study as total storage, can alter the systems that are considered to be stressed versus unstressed. We find that remote sensing observations from NASA's Gravity Recovery and Climate Experiment can assist in providing such information at the scale of a whole aquifer. For example, we demonstrate that a groundwater depletion rate in the Northwest Sahara Aquifer System of 2.69 ± 0.8 km3/yr would result in the aquifer being depleted to 90% of its total storage in as few as 50 years given an initial storage estimate of 70 km3.

  11. CONCEPTUAL FRAMEWORK FOR REGRESSION MODELING OF GROUND-WATER FLOW.

    USGS Publications Warehouse

    Cooley, Richard L.

    1985-01-01

    The author examines the uses of ground-water flow models and which classes of use require treatment of stochastic components. He then compares traditional and stochastic procedures for modeling actual (as distinguished from hypothetical) systems. Finally, he examines the conceptual basis and characteristics of the regression approach to modeling ground-water flow.

  12. New approximation for free surface flow of groundwater: capillarity correction

    E-print Network

    New approximation for free surface flow of groundwater: capillarity correction D.-S. Jeng a,*, B capillarity correction for free surface groundwater flow as modelled by the Boussinesq equation is re-order approximation. Here, a second-order capillarity correction to tide-induced watertable fluctuations in a coastal

  13. Groundwater flow system under a rapidly urbanizing coastal city as determined by hydrogeochemistry

    NASA Astrophysics Data System (ADS)

    Kagabu, Makoto; Shimada, Jun; Delinom, Robert; Tsujimura, Maki; Taniguchi, Makoto

    2011-01-01

    In the Jakarta area (Indonesia), excessive groundwater pumping due to the rapidly increasing population has caused groundwater-related problems such as brackish water contamination in coastal areas and land subsidence. In this study, we adopted multiple hydrogeochemical techniques to demonstrate the groundwater flow system in the Jakarta area. Although almost all groundwater existing in the Jakarta basin is recharged at similar elevations, the water quality and residence time demonstrates a clear difference between the shallow and deep aquifers. Due to the rapid decrease in the groundwater potential in urban areas, we found that the seawater intrusion and the shallow and deep groundwaters are mixing, a conclusion confirmed by major ions, Br -:Cl - ratios, and chlorofluorocarbon (CFC)-12 analysis. Spring water and groundwater samples collected from the southern mountainside area show younger age characteristics with high concentrations of 14C and Ca-HCO 3 type water chemistry. We estimated the residence times of these groundwaters within 45 years under piston flow conditions by tritium analysis. Also, these groundwater ages can be limited to 20-30 years with piston flow evaluated by CFCs. Moreover, due to the magnitude of the CFC-12 concentration, we can use a pseudo age indicator in this field study, because we found a positive correlation between the major type of water chemistry and the CFC-12 concentration.

  14. Using 14C and 3H to understand groundwater flow and recharge in an aquifer window

    NASA Astrophysics Data System (ADS)

    Atkinson, A. P.; Cartwright, I.; Gilfedder, B. S.; Cendón, D. I.; Unland, N. P.; Hofmann, H.

    2014-12-01

    Knowledge of groundwater residence times and recharge locations is vital to the sustainable management of groundwater resources. Here we investigate groundwater residence times and patterns of recharge in the Gellibrand Valley, southeast Australia, where outcropping aquifer sediments of the Eastern View Formation form an "aquifer window" that may receive diffuse recharge from rainfall and recharge from the Gellibrand River. To determine recharge patterns and groundwater flow paths, environmental isotopes (3H, 14C, ?13C, ?18O, ?2H) are used in conjunction with groundwater geochemistry and continuous monitoring of groundwater elevation and electrical conductivity. The water table fluctuates by 0.9 to 3.7 m annually, implying recharge rates of 90 and 372 mm yr-1. However, residence times of shallow (11 to 29 m) groundwater determined by 14C are between 100 and 10 000 years, 3H activities are negligible in most of the groundwater, and groundwater electrical conductivity remains constant over the period of study. Deeper groundwater with older 14C ages has lower ?18O values than younger, shallower groundwater, which is consistent with it being derived from greater altitudes. The combined geochemistry data indicate that local recharge from precipitation within the valley occurs through the aquifer window, however much of the groundwater in the Gellibrand Valley predominantly originates from the regional recharge zone, the Barongarook High. The Gellibrand Valley is a regional discharge zone with upward head gradients that limits local recharge to the upper 10 m of the aquifer. Additionally, the groundwater head gradients adjacent to the Gellibrand River are generally upwards, implying that it does not recharge the surrounding groundwater and has limited bank storage. 14C ages and Cl concentrations are well correlated and Cl concentrations may be used to provide a first-order estimate of groundwater residence times. Progressively lower chloride concentrations from 10 000 years BP to the present day are interpreted to indicate an increase in recharge rates on the Barongarook High.

  15. Groundwater recharge in Wisconsin--Annual estimates for 1970-99 using streamflow data

    USGS Publications Warehouse

    Gebert, Warren A.; Walker, John F.; Hunt, Randall J.

    2011-01-01

    The groundwater component of streamflow is important because it is indicative of the sustained flow of a stream during dry periods, is often of better quality, and has a smaller range of temperatures, than surface contributions to streamflow. All three of these characteristics are important to the health of aquatic life in a stream. If recharge to the aquifers is to be preserved or enhanced, it is important to understand the present partitioning of total streamflow into base flow and stormflow. Additionally, an estimate of groundwater recharge is important for understanding the flows within a groundwater system-information important for water availability/sustainability or other assessments. The U.S. Geological Survey operates numerous continuous-record streamflow-gaging stations (Hirsch and Norris, 2001), which can be used to provide estimates of average annual base flow. In addition to these continuous record sites, Gebert and others (2007) showed that having a few streamflow measurements in a basin can appreciably reduce the error in a base-flow estimate for that basin. Therefore, in addition to the continuous-record gaging stations, a substantial number of low-flow partial-record sites (6 to 15 discharge measurements) and miscellaneous-measurement sites (1 to 3 discharge measurements) that were operated during 1964-90 throughout the State were included in this work to provide additional insight into spatial distribution of annual base flow and, in turn, groundwater recharge.

  16. Groundwater flow in heterogeneous composite C. L. Winter and Daniel M. Tartakovsky

    E-print Network

    Tartakovsky, Daniel M.

    Groundwater flow in heterogeneous composite aquifers C. L. Winter and Daniel M. Tartakovsky Hydrology: Stochastic processes; 1829 Hydrology: Groundwater hydrology; 1832 Hydrology: Groundwater, upscaled, decomposition 1. Introduction [2] It has become common to quantify uncertainty in groundwater

  17. Groundwater dating for understanding nitrogen in groundwater systems - Time lag, fate, and detailed flow path ways

    NASA Astrophysics Data System (ADS)

    Morgenstern, Uwe; Hadfield, John; Stenger, Roland

    2014-05-01

    Nitrate contamination of groundwater is a problem world-wide. Nitrate from land use activities can leach out of the root zone of the crop into the deeper part of the unsaturated zone and ultimately contaminate the underlying groundwater resources. Nitrate travels with the groundwater and then discharges into surface water causing eutrophication of surface water bodies. To understand the source, fate, and future nitrogen loads to ground and surface water bodies, detailed knowledge of the groundwater flow dynamics is essential. Groundwater sampled at monitoring wells or discharges may not yet be in equilibrium with current land use intensity due to the time lag between leaching out of the root zone and arrival at the sampling location. Anoxic groundwater zones can act as nitrate sinks through microbial denitrification. However, the effect of denitrification on overall nitrate fluxes depends on the fraction of the groundwater flowing through such zones. We will show results from volcanic aquifers in the central North Island of New Zealand where age tracers clearly indicate that the groundwater discharges into large sensitive lakes like Lake Taupo and Lake Rotorua are not yet fully realising current land use intensity. The majority of the water discharging into these lakes is decades and up to over hundred years old. Therefore, increases in dairy farming over the last decades are not yet reflected in these old water discharges, but over time these increased nitrate inputs will eventually work their way through the large groundwater systems and increasing N loads to the lakes are to be expected. Anoxic zones are present in some of these aquifers, indicating some denitrification potential, however, age tracer results from nested piezo wells show young groundwater in oxic zones indicating active flow in these zones, while anoxic zones tend to have older water indicating poorer hydraulic conductivity in these zones. Consequently, to evaluate the effect of denitrification on nitrate fluxes it is insufficient to consider only the spatial distribution of oxic and anoxic zones; the flow through these zones needs to be quantified. If the majority of groundwater passes through the oxic zones rather the anoxic zones, insignificant N attenuation must be expected. Our results indicate about an order of magnitude lower vertical flow velocity and flux through anoxic zones compared to oxic zones. The age distribution of the groundwater allows identification of groundwater flow path ways, which in the Lake Taupo catchment is characterised by high piston flow, indicating groundwater flow between widely connected impermeable layers, probably paleosol layers. Groundwater dating has become an important tool for management of nitrate contamination.

  18. Groundwater-flow and land-subsidence model of Antelope Valley, California

    USGS Publications Warehouse

    Siade, Adam J.; Nishikawa, Tracy; Rewis, Diane L.; Martin, Peter; Phillips, Steven P.

    2014-01-01

    The groundwater-flow model of the basin was discretized horizontally into a grid of 130 rows and 118 columns of square cells 1 kilometer (0.621 mile) on a side, and vertically into four layers representing the upper (two layers), middle (one layer), and lower (one layer) aquifers. Faults that were thought to act as horizontal-flow barriers were simulated in the model. The model was calibrated to simulate steady-state conditions, represented by 1915 water levels and transient-state conditions during 1915–95, by using water-level and subsidence data. Initial estimates of the aquifer-system properties and stresses were obtained from a previously published numerical model of the Antelope Valley groundwater basin; estimates also were obtained from recently collected hydrologic data and from results of simulations of groundwater-flow and land-subsidence models of the Edwards Air Force Base area. Some of these initial estimates were modified during

  19. Using Springs to Study Groundwater Flow and Active Geologic Processes

    NASA Astrophysics Data System (ADS)

    Manga, Michael

    Spring water provides a unique opportunity to study a range of subsurface processes in regions with few boreholes or wells. However, because springs integrate the signal of geological and hydrological processes over large spatial areas and long periods of time, they are an indirect source of information. This review illustrates a variety of techniques and approaches that are used to interpret measurements of isotopic tracers, water chemistry, discharge, and temperature. As an example, a set of springs in the Oregon Cascades is considered. By using tracers, temperature, and discharge measurements, it is possible to determine the mean-residence time of water, infer the spatial pattern and extent of groundwater flow, estimate basin-scale hydraulic properties, calculate the regional heat flow, and quantify the rate of magmatic intrusion beneath the volcanic arc.

  20. Rapid, cost-effective estimation of groundwater age based on hydrochemistry

    NASA Astrophysics Data System (ADS)

    Beyer, M.; Morgenstern, U.; Jackson, B. M.; Daughney, C.

    2013-12-01

    In order to manage and protect groundwater resources, the complex and diverse recharge, mixing and flow processes occurring in groundwater systems need to be better understood. Groundwater age information can give valuable information on groundwater flow, recharge sources, and aquifer volumes. However current groundwater dating techniques, for example tracers such as tritium or CFCs, or hydrological models, have limitations and method specific application ranges and uncertainties. Due to this, ambiguous age interpretation is a problem. New technique(s) are essential to overcome limitations and complement existing methods. The aim of this study is to advance the use of hydrochemistry for groundwater dating. To date, hydrochemistry has only been applied sparsely to support groundwater age determination, despite its wide availability from national groundwater monitoring programs. This is due to the lack of any established distinct relationships between hydrochemistry and groundwater age. Establishing these is complex, since hydrochemistry is influenced by complex interrelationships of aquifer specific processes. Therefore underlying processes, such as mineral weathering and redox reactions, and diverse reactions, such as quartz dissolution, are not directly interpretable from hydrochemistry data. Additionally reaction kinetics (of e.g. quartz dissolution) are often aquifer specific, and field data are sparse; furthermore data gained in laboratory environments are difficult to relate back to field situations as comparative studies have found lab and field measurements can differ by orders of magnitude. We wish to establish relationships between hydrochemistry and groundwater age, to allow hydrochemical data to better inform groundwater dating through two separate approaches. Firstly relationships between groundwater age (determined by state of the art dating techniques) and single hydrochemistry parameters, such as silica concentration, can be established in a given aquifer. This relation can then be used in the same or similar aquifer to infer groundwater age from given hydrochemistry. Secondly specific reaction rates of underlying reactions, such as quartz dissolution, can be determined and used to determine specific and ';generic' reaction rates for field environments. We postulate this may in future lead to groundwater dating directly from specific hydrochemistry data in any given aquifer by using ';generic' kinetics. To illustrate these two approaches, regularly measured hydrochemistry data and estimates of groundwater age inferred from tritium, SF6 and CFC-12 within the Lower Hutt Groundwater Zone, a gravel aquifer in Wellington, New Zealand, are used. Correlations of hydrochemistry parameters and groundwater age are presented. Hierarchical Cluster and Factor Analysis are used to investigate major processes which caused the given hydrochemistry. Inverse modelling is used to identify specific underlying reactions, such as weathering of quartz. Reaction kinetics are investigated and results presented.

  1. Groundwater balance estimation in karst by using simple conceptual rainfall-runoff model

    NASA Astrophysics Data System (ADS)

    Željkovi?, Ivana; Kadi?, Ana; Deni?-Juki?, Vesna

    2014-05-01

    The objective of this work is the study of Opa?ac karst spring which geographically lies in Dalmatia (Croatia). Numerous studies have been carried out in karst aiming the investigation of groundwater regime. The karst spring hydrograph can reflect the groundwater regime and consequently the analysis is based on them. A simple conceptual rainfall-runoff model is proposed for the estimation of groundwater balance components including the influences of time invariant catchment boundaries and intercatchment flows. The proposed parameter estimation procedure merges the soil-moisture balance and the groundwater balance approaches to obtain the complete groundwater budget. The effective rainfall is calculated by using mathematical model based on soil-moisture balance equations i.e. Palmer's fluid mass balance method. The parameters of model of effective rainfall are determined by using simple conceptual rainfall-runoff model consisting of two linear reservoirs representing the fast and slow flow component of the recession. The weight coefficient between the fast and slow component is determined by using BFI (Base Flow Index) analysis of hydrograph. Recession coefficient of the slow flow component and the weight coefficient are determined from hydrograph analysis. Available data from nearby meteorological station includes on daily basis daily average discharge, the amount of precipitation, the average temperature and the humidity from 1995-2010. The average catchment area is also estimated with the average yearly runoff deficit using Turc's method and compared with the values obtained from the application of the rainfall-runoff model. Nash-Sutcliffe model efficiency coefficient for simulated hydrograph is applied to assess the predictive power of model. Calculated groundwater balance shows that the Opa?ac Spring aquifer contains a significant storage capacity. The application of series of linear reservoirs is a classical and common technique, but the proposed simple approach enables the estimation of the components of groundwater balance in karst areas.

  2. Mathematical modelling of surface water-groundwater flow and salinity interactions in the coastal zone

    NASA Astrophysics Data System (ADS)

    Spanoudaki, Katerina; Kampanis, Nikolaos A.

    2014-05-01

    Coastal areas are the most densely-populated areas in the world. Consequently water demand is high, posing great pressure on fresh water resources. Climatic change and its direct impacts on meteorological variables (e.g. precipitation) and indirect impact on sea level rise, as well as anthropogenic pressures (e.g. groundwater abstraction), are strong drivers causing groundwater salinisation and subsequently affecting coastal wetlands salinity with adverse effects on the corresponding ecosystems. Coastal zones are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes and variable-density flow conditions. Simulation of sea level rise and tidal effects on aquifer salinisation and accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands requires the use of integrated surface water-groundwater models. In the past few decades several computer codes have been developed to simulate coupled surface and groundwater flow. In these numerical models surface water flow is usually described by the 1-D Saint Venant equations (e.g. Swain and Wexler, 1996) or the 2D shallow water equations (e.g. Liang et al., 2007). Further simplified equations, such as the diffusion and kinematic wave approximations to the Saint Venant equations, are also employed for the description of 2D overland flow and 1D stream flow (e.g. Gunduz and Aral, 2005). However, for coastal bays, estuaries and wetlands it is often desirable to solve the 3D shallow water equations to simulate surface water flow. This is the case e.g. for wind-driven flows or density-stratified flows. Furthermore, most integrated models are based on the assumption of constant fluid density and therefore their applicability to coastal regions is questionable. Thus, most of the existing codes are not well-suited to represent surface water-groundwater interactions in coastal areas. To this end, the 3D integrated surface water-groundwater model IRENE (Spanoudaki et al., 2009; Spanoudaki, 2010) has been modified in order to simulate surface water-groundwater flow and salinity interactions in the coastal zone. IRENE, in its original form, couples the 3D, non-steady state Navier-Stokes equations, after Reynolds averaging and with the assumption of hydrostatic pressure distribution, to the equations describing 3D saturated groundwater flow of constant density. A semi-implicit finite difference scheme is used to solve the surface water flow equations, while a fully implicit finite difference scheme is used for the groundwater equations. Pollution interactions are simulated by coupling the advection-diffusion equation describing the fate and transport of contaminants introduced in a 3D turbulent flow field to the partial differential equation describing the fate and transport of contaminants in 3D transient groundwater flow systems. The model has been further developed to include the effects of density variations on surface water and groundwater flow, while the already built-in solute transport capabilities are used to simulate salinity interactions. Initial results show that IRENE can accurately predict surface water-groundwater flow and salinity interactions in coastal areas. Important research issues that can be investigated using IRENE include: (a) sea level rise and tidal effects on aquifer salinisation and the configuration of the saltwater wedge, (b) the effects of surface water-groundwater interaction on salinity increase of coastal wetlands and (c) the estimation of the location and magnitude of groundwater discharge to coasts. Acknowledgement The work presented in this paper has been funded by the Greek State Scholarships Foundation (IKY), Fellowships of Excellence for Postdoctoral Studies (Siemens Program), 'A simulation-optimization model for assessing the best practices for the protection of surface water and groundwater in the coastal zone', (2013 - 2015). References Gunduz, O. and Aral, M.M. (2005). River networks and groundwater flow: a simultaneous solution of a co

  3. MODFLOW-2000, The U.S. Geological Survey Modular Ground-Water Model - User Guide to Modularization Concepts and the Ground-Water Flow Process

    USGS Publications Warehouse

    Harbaugh, Arlen W.; Banta, Edward R.; Hill, Mary C.; McDonald, Michael G.

    2000-01-01

    MODFLOW is a computer program that numerically solves the three-dimensional ground-water flow equation for a porous medium by using a finite-difference method. Although MODFLOW was designed to be easily enhanced, the design was oriented toward additions to the ground-water flow equation. Frequently there is a need to solve additional equations; for example, transport equations and equations for estimating parameter values that produce the closest match between model-calculated heads and flows and measured values. This report documents a new version of MODFLOW, called MODFLOW-2000, which is designed to accommodate the solution of equations in addition to the ground-water flow equation. This report is a user's manual. It contains an overview of the old and added design concepts, documents one new package, and contains input instructions for using the model to solve the ground-water flow equation.

  4. Comparison of different estimation techniques to quantify groundwater recharge in Pirna, Germany

    NASA Astrophysics Data System (ADS)

    Ringleb, Jana; Sallwey, Jana; Stefan, Catalin

    2015-04-01

    Water scarcity in combination with groundwater exploitation is a major concern worldwide because of climate change, population growth and rising water demand. To be able to sustainably manage and protect groundwater resources, it is necessary to quantify the amount of water which leaks through the unsaturated zone and recharges the aquifer naturally. However, quantifying the spatial and temporal distribution of recharge is difficult because of soil heterogeneity and the influence of vegetation. For that reason and because field measurements of recharge are difficult to obtain, models are valuable tools to quantify recharge. Numerical models need a lot of parameters which are hard to measure and hence can only be estimated. Therefore analytical models or empirical equations which use less and / or easier obtainable parameters could estimate groundwater recharge as well as numerical models because of the underlying uncertainty in parameter estimation. Recharge estimation methods which use different model approaches and have varying complexity were compared at Pirna test field site, Germany to select suitable methods which will later be integrated into a web-based Decision Support System (DSS) developed for the sustainable management of groundwater. The complexity of the used methods covers numerical models, analytical models as well as empirical equations. Different model approaches were used to estimate groundwater recharge including amongst others a groundwater flow model, an unsaturated zone model and a watershed model. The resulting groundwater recharge estimates received from the numerical and analytical models and from empirical equations were compared to evaluate whether the methods are suitable to estimate groundwater recharge considering the complexity, data requirements and time-consumption of each method.

  5. Simulation of ground-water flow and land subsidence in the Antelope Valley ground-water basin, California

    USGS Publications Warehouse

    Leighton, David A.; Phillips, Steven P.

    2003-01-01

    Antelope Valley, California, is a topographically closed basin in the western part of the Mojave Desert, about 50 miles northeast of Los Angeles. The Antelope Valley ground-water basin is about 940 square miles and is separated from the northern part of Antelope Valley by faults and low-lying hills. Prior to 1972, ground water provided more than 90 percent of the total water supply in the valley; since 1972, it has provided between 50 and 90 percent. Most ground-water pumping in the valley occurs in the Antelope Valley ground-water basin, which includes the rapidly growing cities of Lancaster and Palmdale. Ground-water-level declines of more than 200 feet in some parts of the ground-water basin have resulted in an increase in pumping lifts, reduced well efficiency, and land subsidence of more than 6 feet in some areas. Future urban growth and limits on the supply of imported water may continue to increase reliance on ground water. To better understand the ground-water flow system and to develop a tool to aid in effectively managing the water resources, a numerical model of ground-water flow and land subsidence in the Antelope Valley ground-water basin was developed using old and new geohydrologic information. The ground-water flow system consists of three aquifers: the upper, middle, and lower aquifers. The aquifers, which were identified on the basis of the hydrologic properties, age, and depth of the unconsolidated deposits, consist of gravel, sand, silt, and clay alluvial deposits and clay and silty clay lacustrine deposits. Prior to ground-water development in the valley, recharge was primarily the infiltration of runoff from the surrounding mountains. Ground water flowed from the recharge areas to discharge areas around the playas where it discharged either from the aquifer system as evapotranspiration or from springs. Partial barriers to horizontal ground-water flow, such as faults, have been identified in the ground-water basin. Water-level declines owing to ground-water development have eliminated the natural sources of discharge, and pumping for agricultural and urban uses have become the primary source of discharge from the ground-water system. Infiltration of return flows from agricultural irrigation has become an important source of recharge to the aquifer system. The ground-water flow model of the basin was discretized horizontally into a grid of 43 rows and 60 columns of square cells 1 mile on a side, and vertically into three layers representing the upper, middle, and lower aquifers. Faults that were thought to act as horizontal-flow barriers were simulated in the model. The model was calibrated to simulate steady-state conditions, represented by 1915 water levels and transient-state conditions during 1915-95 using water-level and subsidence data. Initial estimates of the aquifer-system properties and stresses were obtained from a previously published numerical model of the Antelope Valley ground-water basin; estimates also were obtained from recently collected hydrologic data and from results of simulations of ground-water flow and land subsidence models of the Edwards Air Force Base area. Some of these initial estimates were modified during model calibration. Ground-water pumpage for agriculture was estimated on the basis of irrigated crop acreage and crop consumptive-use data. Pumpage for public supply, which is metered, was compiled and entered into a database used for this study. Estimated annual pumpage peaked at 395,000 acre-feet (acre-ft) in 1952 and then declined because of declining agricultural production. Recharge from irrigation-return flows was estimated to be 30 percent of agricultural pumpage; the irrigation-return flows were simulated as recharge to the regional water table 10 years following application at land surface. The annual quantity of natural recharge initially was based on estimates from previous studies. During model calibration, natural recharge was reduced from the initial

  6. FULLYDISCRETE FINITE ELEMENT ANALYSIS OF MULTIPHASE FLOW IN GROUNDWATER HYDROLOGY

    E-print Network

    Ewing, Richard E.

    element method for a nonlinear differential system for describing an air­water system in groundwater, air­water system, numerical experiments AMS subject classifications. Primary 65N30, 76S05 1 the flow equations for an air­water system in groundwater hydrology, ff = a; w [3], [14], [32]: @(OEae ff

  7. Deflated CG Method for Modelling Groundwater Flow Near Faults

    E-print Network

    Vuik, Kees

    Deflated CG Method for Modelling Groundwater Flow Near Faults Interim Report L.A. Ros Delft and market parties. The institute is located in two cities: Delft and Utrecht. Since September 2007 I am Introduction 1 1.1 Subsurface, Groundwater and Faults . . . . . . . . . . . . . . . . . . . . . . 1 1

  8. Intercomparison of submarine groundwater discharge estimates from a sandy

    E-print Network

    meters, hydrogeologic estimation using Darcy's law, and tracer-based estimates using radon and radium and fresh SGD estimates is in good agreement with the radium-based SGD KEYWORDS Submarine groundwater discharge; Coastal aquifer; Thermal image; Geochemical tracers; Radium; Radon 0022-1694/$ - see front matter

  9. Locating groundwater flow in karst by acoustic emission surveys

    SciTech Connect

    Stokowski, S.J. Jr.; Clark, D.A.

    1985-01-01

    An acoustic emission survey of Newala Fm. (primarily dolomite) karst has helped to locate subsurface water flow. This survey was performed on the Rock Quarry Dome, Sevier County, Tennessee. A Dresser RS-4 recording seismograph, adjusted to provide a gain of 1000, collected acoustic emission data using Mark Products CN368 vertical geophones with 3-inch spikes. Data was collected for 5-15 second intervals. The geophones were laid out along traverses with 10, 20, or 30-ft spacing and covered with sand bags in locations of high ambient noise. Traverses were laid out: along and across lineaments known to correspond with groundwater flow in natural subsurface channels; across and along a joint-controlled sink suspected of directing groundwater flow; and across a shallow sinkhole located tangentially to the Little Pigeon River and suspected of capturing river water for the groundwater system. Acoustic emissions of channelized flowing groundwater have a characteristic erratic spiked spectral signature. These acoustic emission signatures increase in amplitude and number in the immediate vicinity of the vertical projection of channelized groundwater flow if it occurs within approximately 30 feet of the surface. If the groundwater flow occurs at greater depths the emissions may be offset from the projection of the actual flow, due to propagation of the signal along rock pinnacles or attenuation by residual soils.

  10. Improved methods for GRACE-derived groundwater storage change estimation in large-scale agroecosystems

    NASA Astrophysics Data System (ADS)

    Brena, A.; Kendall, A. D.; Hyndman, D. W.

    2013-12-01

    Large-scale agroecosystems are major providers of agricultural commodities and an important component of the world's food supply. In agroecosystems that depend mainly in groundwater, it is well known that their long-term sustainability can be at risk because of water management strategies and climatic trends. The water balance of groundwater-dependent agroecosystems such as the High Plains aquifer (HPA) are often dominated by pumping and irrigation, which enhance hydrological processes such as evapotranspiration, return flow and recharge in cropland areas. This work provides and validates new quantitative groundwater estimation methods for the HPA that combine satellite-based estimates of terrestrial water storage (GRACE), hydrological data assimilation products (NLDAS-2) and in situ measurements of groundwater levels and irrigation rates. The combined data can be used to elucidate the controls of irrigation on the water balance components of agroecosystems, such as crop evapotranspiration, soil moisture deficit and recharge. Our work covers a decade of continuous observations and model estimates from 2003 to 2013, which includes a significant drought since 2011. This study aims to: (1) test the sensitivity of groundwater storage to soil moisture and irrigation, (2) improve estimates of irrigation and soil moisture deficits (3) infer mean values of groundwater recharge across the HPA. The results show (1) significant improvements in GRACE-derived aquifer storage changes using methods that incorporate irrigation and soil moisture deficit data, (2) an acceptable correlation between the observed and estimated aquifer storage time series for the analyzed period, and (3) empirically-estimated annual rates of groundwater recharge that are consistent with previous geochemical and modeling studies. We suggest testing these correction methods in other large-scale agroecosystems with intensive groundwater pumping and irrigation rates.

  11. Permafrost thaw in a nested groundwater-flow system

    NASA Astrophysics Data System (ADS)

    McKenzie, Jeffrey M.; Voss, Clifford I.

    2013-02-01

    Groundwater flow in cold regions containing permafrost accelerates climate-warming-driven thaw and changes thaw patterns. Simulation analyses of groundwater flow and heat transport with freeze/thaw in typical cold-regions terrain with nested flow indicate that early thaw rate is particularly enhanced by flow, the time when adverse environmental impacts of climate-warming-induced permafrost loss may be severest. For the slowest climate-warming rate predicted by the Intergovernmental Panel on Climate Change (IPCC), once significant groundwater flow begins, thick permafrost layers can vanish in several hundred years, but survive over 1,000 years where flow is minimal. Large-scale thaw depends mostly on the balance of heat advection and conduction in the supra-permafrost zone. Surface-water bodies underlain by open taliks allow slow sub-permafrost flow, with lesser influence on regional thaw. Advection dominance over conduction depends on permeability and topography. Groundwater flow around permafrost and flow through permafrost impact thaw differently; the latter enhances early thaw rate. Air-temperature seasonality also increases early thaw. Hydrogeologic heterogeneity and topography strongly affect thaw rates/patterns. Permafrost controls the groundwater/surface-water-geomorphology system; hence, prediction and mitigation of impacts of thaw on ecology, chemical exports and infrastructure require improved hydrogeology/permafrost characterization and understanding.

  12. Permafrost thaw in a nested groundwater-flow system

    USGS Publications Warehouse

    McKenzie, Jeffery M.; Voss, Clifford I.

    2013-01-01

    Groundwater flow in cold regions containing permafrost accelerates climate-warming-driven thaw and changes thaw patterns. Simulation analyses of groundwater flow and heat transport with freeze/thaw in typical cold-regions terrain with nested flow indicate that early thaw rate is particularly enhanced by flow, the time when adverse environmental impacts of climate-warming-induced permafrost loss may be severest. For the slowest climate-warming rate predicted by the Intergovernmental Panel on Climate Change (IPCC), once significant groundwater flow begins, thick permafrost layers can vanish in several hundred years, but survive over 1,000 years where flow is minimal. Large-scale thaw depends mostly on the balance of heat advection and conduction in the supra-permafrost zone. Surface-water bodies underlain by open taliks allow slow sub-permafrost flow, with lesser influence on regional thaw. Advection dominance over conduction depends on permeability and topography. Groundwater flow around permafrost and flow through permafrost impact thaw differently; the latter enhances early thaw rate. Air-temperature seasonality also increases early thaw. Hydrogeologic heterogeneity and topography strongly affect thaw rates/patterns. Permafrost controls the groundwater/surface-water-geomorphology system; hence, prediction and mitigation of impacts of thaw on ecology, chemical exports and infrastructure require improved hydrogeology/permafrost characterization and understanding

  13. Groundwater flow and solute movement to drain laterals, western San Joaquin Valley, California: 1. Geochemical assessment

    USGS Publications Warehouse

    Deverel, S.J.; Fio, John L.

    1991-01-01

    A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results elucidate the process of mixing of deep and shallow groundwater (below and within 6 m from land surface) entering the drain laterals. The deep groundwater was subject to evapoconcentration prior to drainage system installation and has been displaced downward (to depths greater than 6 m) in the groundwater system. The proportions of deep and shallow groundwater entering the drain laterals was calculated from the end-member oxygen 18 compositions determined in groundwater samples. The percentage of total drain lateral flow which is deep groundwater flow is about 30% for the shallow drain lateral (1.8 m below land surface) (drain lateral 1)) and 60% for the deep drain lateral (2.7 m below land surface (drain lateral 2)). During irrigation, the percentages of deep groundwater flow decrease to 0 and 30% for the shallow and deep drain laterals, respectively. Selenium concentrations in drain lateral waters decrease during irrigation but selenium loads increase. Total estimated annual loads were 1.1 and 5.4 kg of selenium for drain laterals 1 and 2, respectively. Substantial percentages of the annual load occurred during 8 days of irrigation, 23 and 9% for drain laterals 1 and 2, respectively.

  14. Groundwater Flow and Solute Movement to Drain Laterals, Western San Joaquin Valley, California: 1. Geochemical Assessment

    NASA Astrophysics Data System (ADS)

    Deverel, S. J.; Fio, John L.

    1991-09-01

    A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results elucidate the process of mixing of deep and shallow groundwater (below and within 6 m from land surface) entering the drain laterals. The deep groundwater was subject to evapoconcentration prior to drainage system installation and has been displaced downward (to depths greater than 6 m) in the groundwater system. The proportions of deep and shallow groundwater entering the drain laterals was calculated from the end-member oxygen 18 compositions determined in groundwater samples. The percentage of total drain lateral flow which is deep groundwater flow is about 30% for the shallow drain lateral (1.8 m below land surface) (drain lateral 1)) and 60% for the deep drain lateral (2.7 m below land surface (drain lateral 2)). During irrigation, the percentages of deep groundwater flow decrease to 0 and 30% for the shallow and deep drain laterals, respectively. Selenium concentrations in drain lateral waters decrease during irrigation but selenium loads increase. Total estimated annual loads were 1.1 and 5.4 kg of selenium for drain laterals 1 and 2, respectively. Substantial percentages of the annual load occurred during 8 days of irrigation, 23 and 9% for drain laterals 1 and 2, respectively.

  15. PUMa - modelling the groundwater flow in Baltic Sedimentary Basin

    NASA Astrophysics Data System (ADS)

    Kalvane, G.; Marnica, A.; Bethers, U.

    2012-04-01

    In 2009-2012 at University of Latvia and Latvia University of Agriculture project "Establishment of interdisciplinary scientist group and modelling system for groundwater research" is implemented financed by the European Social Fund. The aim of the project is to develop groundwater research in Latvia by establishing interdisciplinary research group and modelling system covering groundwater flow in the Baltic Sedimentary Basin. Researchers from fields like geology, chemistry, mathematical modelling, physics and environmental engineering are involved in the project. The modelling system is used as a platform for addressing scientific problems such as: (1) large-scale groundwater flow in Baltic Sedimentary Basin and impact of human activities on it; (2) the evolution of groundwater flow since the last glaciation and subglacial groundwater recharge; (3) the effects of climate changes on shallow groundwater and interaction of hydrographical network and groundwater; (4) new programming approaches for groundwater modelling. Within the frame of the project most accessible geological information such as description of geological wells, geological maps and results of seismic profiling in Latvia as well as Estonia and Lithuania are collected and integrated into modelling system. For example data form more then 40 thousands wells are directly used to automatically generate the geological structure of the model. Additionally a groundwater sampling campaign is undertaken. Contents of CFC, stabile isotopes of O and H and radiocarbon are the most significant parameters of groundwater that are established in unprecedented scale for Latvia. The most important modelling results will be published in web as a data set. Project number: 2009/0212/1DP/1.1.1.2.0/09/APIA/VIAA/060. Project web-site: www.puma.lu.lv

  16. Update to the Ground-Water Withdrawals Database for the Death Valley REgional Ground-Water Flow System, Nevada and California, 1913-2003

    SciTech Connect

    Michael T. Moreo; and Leigh Justet

    2008-07-02

    Ground-water withdrawal estimates from 1913 through 2003 for the Death Valley regional ground-water flow system are compiled in an electronic database to support a regional, three-dimensional, transient ground-water flow model. This database updates a previously published database that compiled estimates of ground-water withdrawals for 1913–1998. The same methodology is used to construct each database. Primary differences between the 2 databases are an additional 5 years of ground-water withdrawal data, well locations in the updated database are restricted to Death Valley regional ground-water flow system model boundary, and application rates are from 0 to 1.5 feet per year lower than original estimates. The lower application rates result from revised estimates of crop consumptive use, which are based on updated estimates of potential evapotranspiration. In 2003, about 55,700 acre-feet of ground water was pumped in the DVRFS, of which 69 percent was used for irrigation, 13 percent for domestic, and 18 percent for public supply, commercial, and mining activities.

  17. Stable isotope and groundwater flow dynamics of agricultural irrigation recharge into groundwater resources of the Central Valley, California

    SciTech Connect

    Davisson, M.L.; Criss, R.E.

    1995-01-01

    Intensive agricultural irrigation and overdraft of groundwater in the Central Valley of California profoundly affect the regional quality and availability of shallow groundwater resources. In the natural state, the {delta}{sup 18}O values of groundwater were relatively homogeneous (mostly -7.0 {+-} 0.5{per_thousand}), reflecting local meteoric recharge that slowly (1-3m/yr) flowed toward the valley axis. Today, on the west side of the valley, the isotope distribution is dominated by high {sup 18}O enclosures formed by recharge of evaporated irrigation waters, while the east side has bands of low {sup 18}O groundwater indicating induced recharge from rivers draining the Sierra Nevada mountains. Changes in {delta}{sup 18}O values caused by the agricultural recharge strongly correlate with elevated nitrate concentrations (5 to >100 mg/L) that form pervasive, non-point source pollutants. Small, west-side cities dependent solely on groundwater resources have experienced increases of >1.0 mg/L per year of nitrate for 10-30 years. The resultant high nitrates threaten the economical use of the groundwater for domestic purposes, and have forced some well shut-downs. Furthermore, since >80% of modern recharge is now derived from agricultural irrigation, and because modern recharge rates are {approximately}10 times those of the natural state, agricultural land retirement by urbanization will severely curtail the current safe-yields and promote overdraft pumping. Such overdrafting has occurred in the Sacramento metropolitan area for {approximately}40 years, creating cones of depression {approximately}25m deep. Today, groundwater withdrawal in Sacramento is approximately matched by infiltration of low {sup 18}O water (-11.0{per_thousand}) away from the Sacramento and American Rivers, which is estimated to occur at 100-300m/year from the sharp {sup 18}O gradients in our groundwater isotope map.

  18. Multivariate analyses with end-member mixing to characterize groundwater flow: Wind Cave and associated aquifers

    USGS Publications Warehouse

    Long, Andrew J.; Valder, Joshua F.

    2011-01-01

    Principal component analysis (PCA) applied to hydrochemical data has been used with end-member mixing to characterize groundwater flow to a limited extent, but aspects of this approach are unresolved. Previous similar approaches typically have assumed that the extreme-value samples identified by PCA represent end members. The method presented herein is different from previous work in that (1) end members were not assumed to have been sampled but rather were estimated and constrained by prior knowledge; (2) end-member mixing was quantified in relation to hydrogeologic domains, which focuses model results on major hydrologic processes; (3) a method to select an appropriate number of end members using a series of cluster analyses is presented; and (4) conservative tracers were weighted preferentially in model calibration, which distributed model errors of optimized values, or residuals, more appropriately than would otherwise be the case. The latter item also provides an estimate of the relative influence of geochemical evolution along flow paths in comparison to mixing. This method was applied to groundwater in Wind Cave and the associated karst aquifer in the Black Hills of South Dakota, USA. The end-member mixing model was used to test a hypothesis that five different end-member waters are mixed in the groundwater system comprising five hydrogeologic domains. The model estimated that Wind Cave received most of its groundwater inflow from local surface recharge with an additional 33% from an upgradient aquifer. Artesian springs in the vicinity of Wind Cave primarily received water from regional groundwater flow.

  19. Estimation of submarine groundwater discharge and associated nutrient fluxes in Tolo Harbour, Hong Kong

    E-print Network

    Jiao, Jiu Jimmy

    Estimation of submarine groundwater discharge and associated nutrient fluxes in Tolo Harbour, Hong 2012 Keywords: Submarine groundwater discharge Nutrients Radium isotope Groundwater Estuary Tolo Harbour, located in the northeastern part of Hong Kong's New Territories, China, has a high frequency

  20. Groundwater storage trends in the Loess Plateau of China estimated from streamflow records

    NASA Astrophysics Data System (ADS)

    Gao, Zhaoliang; Zhang, Lu; Cheng, Lei; Zhang, Xiaoping; Cowan, Tim; Cai, Wenju; Brutsaert, Wilfried

    2015-11-01

    The catchments in the Loess Plateau in China have experienced significant land use change since the 1950s with a great number of soil conservation measures such as revegetation being implemented. Such soil conservation measures and climate variability have had considerable impacts on annual streamflow from these catchments. However, much less is known about changes in groundwater storage as the period of direct groundwater storage measurements is too short to reliably infer groundwater storage trends. For this study, annual values of groundwater storage from 38 catchments in the Loess Plateau were estimated from daily streamflow records based on groundwater flow theory. It was found that over the period of record (viz. 1955-2010), statistically significant (p < 0.1) downward trends have been identified in 20 selected catchments with an average reduction of -0.0299 mm per year, mostly located in the northern part of the Loess Plateau. Upward groundwater storage trends were observed in 10 catchments with an average increase of 0.00467 mm per year; these upward trends occurred in southern parts of the study area. Groundwater storage showed no statistically significant trends in 8 out of the 38 selected catchments. Soil conservation measures implemented in the Loess Plateau such as large-scale revegetation may have contributed to the estimated groundwater storage trends. Changes in sea surface temperature in the tropical Pacific Ocean, as indicated by shifts in climate variability modes such as El Niño-Southern Oscillation and the Pacific Decadal Oscillation, appear to have also contributed to the decreasing trends in groundwater storage in this region.

  1. 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.

  2. Estimation of groundwater velocities from Yucca Flat to the Amargosa Desert using geochemistry and environmental isotopes

    SciTech Connect

    Hershey, R.L.; Acheampong, S.Y.

    1997-06-01

    Geochemical and isotopic data from groundwater sampling locations can be used to estimate groundwater flow velocities for independent comparison to velocities calculated by other methods. The objective of this study was to calculate groundwater flow velocities using geochemistry and environmental isotopes from the southern end of Yucca Flat to the Amargosa Desert, considering mixing of different groundwater inputs from sources each and southeast of the Nevada Test Site (NTS). The approach used to accomplish the objective of this study consisted of five steps: (1) reviewing and selecting locations where carbon isotopic groundwater analyses, reliable ionic analysis, and well completion information are available; (2) calculating chemical speciation with the computer code WATEQ4F (Ball and Nordstrom, 1991) to determine the saturation state of mineral phases for each ground water location; (3) grouping wells into reasonable flowpaths and mixing scenarios from different groundwater sources; (4) using the computer code NETPATH (Plummer et al., 1991) to simulate mixing and the possible chemical reactions along the flowpath, and to calculate the changes in carbon-13/carbon-12 isotopic ratios ({delta}{sup 13}C) as a result of these reactions; and (5) using carbon-14 ({sup 14}C) data to calculate velocity.

  3. Modelling groundwater flow and transport in fractured crystalline rock

    SciTech Connect

    Gustafson, G.; Hodgkinson, D.; Stroem, A.

    1995-12-31

    Studies on the validity of commonly used approaches of modelling groundwater flow and transport in fractured crystalline rocks have been made during recent years in two research facilities in Sweden, The Stripa Mine and the Aspo Flard Rock Laboratory. In both cases predictive modelling of a suite of groundwater flow and transport experiments were made in parallel by a number of modelling groups with different approaches. The modelling was in both cases followed by peer groups, that set objectives and scrutinised the results in order to assess the validity of the models. An overall conclusion of the work is that groundwater modelling is both useful and feasible for describing groundwater movements in a fractured crystalline rock. The modelling approach to use is, however dependent on the entity being modelled. There is also a concensus that a better understanding of transport processes is necessary.

  4. Indications of regional scale groundwater flows in the Amazon Basins: Inferences from results of geothermal studies

    NASA Astrophysics Data System (ADS)

    Pimentel, Elizabeth T.; Hamza, Valiya M.

    2012-08-01

    The present work deals with determination groundwater flows in the Amazon region, based on analysis of geothermal data acquired in shallow and deep wells. The method employed is based on the model of simultaneous heat transfer by conduction and advection in permeable media. Analysis of temperature data acquired in water wells indicates down flows of groundwaters with velocities in excess of 10-7 m/s at depths less than 300 m in the Amazonas basin. Bottom-hole temperature (BHT) data sets have been used in determining characteristics of fluid movements at larger depths in the basins of Acre, Solimões, Amazonas, Marajó and Barreirinhas. The results of model simulations point to down flow of groundwaters with velocities of the order of 10-8 to 10-9 m/s, at depths of up to 4000 m. No evidence has been found for up flow typical of discharge zones. The general conclusion compatible with such results is that large-scale groundwater recharge systems operate at both shallow and deep levels in all sedimentary basins of the Amazon region. However, the basement rock formations of the Amazon region are relatively impermeable and hence extensive down flow systems through the sedimentary strata are possible only in the presence of generalized lateral movement of groundwater in the basal parts of the sedimentary basins. The direction of this lateral flow, inferred from the basement topography and geological characteristics of the region, is from west to east, following roughly the course of surface drainage system of the Amazon River, with eventual discharge into the Atlantic Ocean. The estimated flow rate at the continental margin is 3287 m3/s, with velocities of the order of 218 m/year. It is possible that dynamic changes in the fluvial systems in the western parts of South American continent have been responsible for triggering alterations in the groundwater recharge systems and deep seated lateral flows in the Amazon region.

  5. Estimation of submarine groundwater discharge to Osaka Bay, Japan by numerical simulation

    NASA Astrophysics Data System (ADS)

    Yasumoto, J.; Nakaya, S.; Mitamura, M.; Takahashi, M.; Onodera, S.; Taniguchi, M.

    2009-12-01

    Urbanization induces a rapid direct runoff and less rainwater recharge to shallow groundwater. In order to manage water resource in a basin scale, it is important to estimate local hydrological cycle depending on land use. Therefore, understanding the water flow, such as direct runoff and groundwater discharge is essential since these are important hydrological components of water resource management (Carl. E. R et al., 2003). Besides, coastal environment deterioration caused by nutrient discharge from the land area is a serious problem. Previous research made in the last decades has shown that direct groundwater discharge to coastal zone is a significant pathway of water and nutrient form land to ocean (Moore, 1996). For instance, groundwater discharge has often contained higher chronic inputs, which is from fertilizers and sewage. Therefore, groundwater discharge often makes the significant effect to coastal marine eutrophication (Taniguchi, 2002). This study focuses on the environmental rehabilitation of Osaka Bay, Japan, where eutrophication has been occurred recently. It is recognized that this problem is caused by an increase of the nutrient input, as fertilizers and wastewater, through direct runoff and groundwater discharge from the residential, industrial and agricultural areas in Osaka Bay catchment. However, groundwater discharge has not yet been quantified as the pathway of nutrients input in this area. In a present study, a simple but efficient approach is proposed in order to estimate groundwater discharge from the basin by water budget analysis. The groundwater recharge model was applied to calculate hydrological components, such as direct runoff, groundwater recharge and evapotranspiration in the basin. Water balance analysis is effective method to estimate the groundwater discharge from a river basin to sea. However, it is often difficult to estimate the exact SGD flux with water budget analysis in a large area. Therefore, it is necessary to develop a new model considering groundwater flow and saltwater intrusion (density effect). In the present study, the three dimensional fresh/salt water flow equation is applied in order to describe the processes of SGD to the sea using SEAWAT (Langevin et al., 2003). The developed model can be used to scale up the measured seepage meter values to a large catchment. The catchment water balance for a planned basin of Osaka Bay, which is located at west of Kyushu Island, Japan, is studied by the suggested method simultaneous analysis of both surface runoff and groundwater flow. In the modelling, the aquifer is divided into ten confined aquifers and an overlying phreatic aquifer separated by a semi permeable layer. The calculation area of the lower sub-confined aquifer is extended until the sea bottom to describe a SGD. The results shows that the annual river discharges and groundwater levels agree reasonably well with the observed values. The model is suitable for the scale-up estimation of SGD to the ocean or semi-closed inner bay from large scale basins.

  6. 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.

  7. Estimation of Groundwater Recharge at Pahute Mesa using the Chloride Mass-Balance Method

    SciTech Connect

    Cooper, Clay A; Hershey, Ronald L; Healey, John M; Lyles, Brad F

    2013-07-01

    Groundwater recharge on Pahute Mesa was estimated using the chloride mass-balance (CMB) method. This method relies on the conservative properties of chloride to trace its movement from the atmosphere as dry- and wet-deposition through the soil zone and ultimately to the saturated zone. Typically, the CMB method assumes no mixing of groundwater with different chloride concentrations; however, because groundwater is thought to flow into Pahute Mesa from valleys north of Pahute Mesa, groundwater flow rates (i.e., underflow) and chloride concentrations from Kawich Valley and Gold Flat were carefully considered. Precipitation was measured with bulk and tipping-bucket precipitation gauges installed for this study at six sites on Pahute Mesa. These data, along with historical precipitation amounts from gauges on Pahute Mesa and estimates from the PRISM model, were evaluated to estimate mean annual precipitation. Chloride deposition from the atmosphere was estimated by analyzing quarterly samples of wet- and dry-deposition for chloride in the bulk gauges and evaluating chloride wet-deposition amounts measured at other locations by the National Atmospheric Deposition Program. Mean chloride concentrations in groundwater were estimated using data from the UGTA Geochemistry Database, data from other reports, and data from samples collected from emplacement boreholes for this study. Calculations were conducted assuming both no underflow and underflow from Kawich Valley and Gold Flat. Model results estimate recharge to be 30 mm/yr with a standard deviation of 18 mm/yr on Pahute Mesa, for elevations >1800 m amsl. These estimates assume Pahute Mesa recharge mixes completely with underflow from Kawich Valley and Gold Flat. The model assumes that precipitation, chloride concentration in bulk deposition, underflow and its chloride concentration, have been constant over the length of time of recharge.

  8. A guide for using the transient ground-water flow model of the Death Valley regional ground-water flow system, Nevada and California

    USGS Publications Warehouse

    Blainey, Joan B.; Faunt, Claudia C.; Hill, Mary C.

    2006-01-01

    This report is a guide for executing numerical simulations with the transient ground-water flow model of the Death Valley regional ground-water flow system, Nevada and California using the U.S. Geological Survey modular finite-difference ground-water flow model, MODFLOW-2000. Model inputs, including observations of hydraulic head, discharge, and boundary flows, are summarized. Modification of the DVRFS transient ground-water model is discussed for two common uses of the Death Valley regional ground-water flow system model: predictive pumping scenarios that extend beyond the end of the model simulation period (1998), and model simulations with only steady-state conditions.

  9. A Guide for Using the Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California

    SciTech Connect

    Joan B. Blainey; Claudia C. Faunt, and Mary C. Hill

    2006-05-16

    This report is a guide for executing numerical simulations with the transient ground-water flow model of the Death Valley regional ground-water flow system, Nevada and California using the U.S. Geological Survey modular finite-difference ground-water flow model, MODFLOW-2000. Model inputs, including observations of hydraulic head, discharge, and boundary flows, are summarized. Modification of the DVRFS transient ground-water model is discussed for two common uses of the Death Valley regional ground-water flow system model: predictive pumping scenarios that extend beyond the end of the model simulation period (1998), and model simulations with only steady-state conditions.

  10. SWB-A modified Thornthwaite-Mather Soil-Water-Balance code for estimating groundwater recharge

    USGS Publications Warehouse

    Westenbroek, S.M.; Kelson, V.A.; Dripps, W.R.; Hunt, R.J.; Bradbury, K.R.

    2010-01-01

    A Soil-Water-Balance (SWB) computer code has been developed to calculate spatial and temporal variations in groundwater recharge. The SWB model calculates recharge by use of commonly available geographic information system (GIS) data layers in combination with tabular climatological data. The code is based on a modified Thornthwaite-Mather soil-water-balance approach, with components of the soil-water balance calculated at a daily timestep. Recharge calculations are made on a rectangular grid of computational elements that may be easily imported into a regional groundwater-flow model. Recharge estimates calculated by the code may be output as daily, monthly, or annual values.

  11. Incorporation of prior information on parameters into nonlinear regression groundwater flow models. l. Theory.

    USGS Publications Warehouse

    Cooley, R.L.

    1982-01-01

    Prior information on the parameters of a groundwater flow model can be used to improve parameter estimates obtained from nonlinear regression solution of a modeling problem. Two scales of prior information can be available: 1) prior information having known reliability (that is, bias and random error structure), and 2) prior information consisting of best available estimates of unknown reliability. It is shown that if both scales of prior information are available, then a combined regression analysis may be made. -from Author

  12. Flow calculations for Yucca Mountain groundwater travel time (GWTT-95)

    SciTech Connect

    Altman, S.J.; Arnold, B.W.; Barnard, R.W.; Barr, G.E.; Ho, C.K.; McKenna, S.A.; Eaton, R.R.

    1996-09-01

    In 1983, high-level radioactive waste repository performance requirements related to groundwater travel time were defined by NRC subsystem regulation 10 CFR 60.113. Although DOE is not presently attempting to demonstrate compliance with that regulation, understanding of the prevalence of fast paths in the groundwater flow system remains a critical element of any safety analyses for a potential repository system at Yucca Mountain, Nevada. Therefore, this analysis was performed to allow comparison of fast-path flow against the criteria set forth in the regulation. Models developed to describe the conditions for initiation, propagation, and sustainability of rapid groundwater movement in both the unsaturated and saturated zones will form part of the technical basis for total- system analyses to assess site viability and site licensability. One of the most significant findings is that the fastest travel times in both unsaturated and saturated zones are in the southern portion of the potential repository, so it is recommended that site characterization studies concentrate on this area. Results support the assumptions regarding the importance of an appropriate conceptual model of groundwater flow and the incorporation of heterogeneous material properties into the analyses. Groundwater travel times are sensitive to variation/uncertainty in hydrologic parameters and in infiltration flux at upper boundary of the problem domain. Simulated travel times are also sensitive to poorly constrained parameters of the interaction between flow in fractures and in the matrix.

  13. Estimation of urban-enhanced infiltration and groundwater recharge, Sierra Vista subbasin, southeast Arizona USA

    NASA Astrophysics Data System (ADS)

    Stewart, Anne M.

    This dissertation reports on the methods and results of a three-phased investigation to estimate the annual volume of ephemeral-channel-focused groundwater recharge attributable to urbanization (urban-enhanced groundwater recharge) in the Sierra Vista subwatershed of southeastern Arizona, USA. Results were used to assess a prior estimate. The first research phase focused on establishment of a study area, installation of a distributed network of runoff gages, gaging for stage, and transforming 2008 stage data into time series of volumetric discharge, using the continuous slope-area method. Stage data were collected for water years 2008 - 2011. The second research phase used 2008 distributed runoff data with NWS DOPPLER RADAR data to optimize a rainfall-runoff computational model, with the aim of identifying optimal site-specific distributed hydraulic conductivity values and model-predicted infiltration. The third research phase used the period-of-record runoff stage data to identify study-area ephemeral flow characteristics and to estimate channel-bed infiltration of flow events. Design-storm modeling was used to identify study-area predevelopment ephemeral flow characteristics, given the same storm event. The difference between infiltration volumes calculated for the two cases was attributed to urbanization. Estimated evapotranspiration was abstracted and the final result was equated with study-area-scale urban-enhanced groundwater recharge. These results were scaled up to the Sierra Vista subwatershed: the urban-enhanced contribution to groundwater recharge is estimated to range between 3270 and 3635 cubic decameters (between 2650 and 2945 acre-feet) per year for the period of study. Evapotranspirational losses were developed from estimates made elsewhere in the subwatershed. This, and other sources of uncertainty in the estimates, are discussed and quantified if possible.

  14. Controls on groundwater flow in a semiarid folded and faulted intermountain basin

    NASA Astrophysics Data System (ADS)

    Ball, Lyndsay B.; Caine, Jonathan Saul; Ge, Shemin

    2014-08-01

    The major processes controlling groundwater flow in intermountain basins are poorly understood, particularly in basins underlain by folded and faulted bedrock and under regionally realistic hydrogeologic heterogeneity. To explore the role of hydrogeologic heterogeneity and poorly constrained mountain hydrologic conditions on regional groundwater flow in contracted intermountain basins, a series of 3-D numerical groundwater flow models were developed using the South Park basin, Colorado, USA as a proxy. The models were used to identify the relative importance of different recharge processes to major aquifers, to estimate typical groundwater circulation depths, and to explore hydrogeologic communication between mountain and valley hydrogeologic landscapes. Modeling results show that mountain landscapes develop topographically controlled and predominantly local-scale to intermediate-scale flow systems. Permeability heterogeneity of the fold and fault belt and decreased topographic roughness led to permeability controlled flow systems in the valley. The structural position of major aquifers in the valley fold and fault belt was found to control the relative importance of different recharge mechanisms. Alternative mountain recharge model scenarios showed that higher mountain recharge rates led to higher mountain water table elevations and increasingly prominent local flow systems, primarily resulting in increased seepage within the mountain landscape and nonlinear increases in mountain block recharge to the valley. Valley aquifers were found to be relatively insensitive to changing mountain water tables, particularly in structurally isolated aquifers inside the fold and fault belt.

  15. Control on groundwater flow in a semiarid folded and faulted intermountain basin

    USGS Publications Warehouse

    Ball, Lyndsay B.; Caine, Jonathan S.; Ge, Shemin

    2013-01-01

    The major processes controlling groundwater flow in intermountain basins are poorly understood, particularly in basins underlain by folded and faulted bedrock and under regionally realistic hydrogeologic heterogeneity. To explore the role of hydrogeologic heterogeneity and poorly constrained mountain hydrologic conditions on regional groundwater flow in contracted intermountain basins, a series of 3-D numerical groundwater flow models were developed using the South Park basin, Colorado, USA as a proxy. The models were used to identify the relative importance of different recharge processes to major aquifers, to estimate typical groundwater circulation depths, and to explore hydrogeologic communication between mountain and valley hydrogeologic landscapes. Modeling results show that mountain landscapes develop topographically controlled and predominantly local-scale to intermediate-scale flow systems. Permeability heterogeneity of the fold and fault belt and decreased topographic roughness led to permeability controlled flow systems in the valley. The structural position of major aquifers in the valley fold and fault belt was found to control the relative importance of different recharge mechanisms. Alternative mountain recharge model scenarios showed that higher mountain recharge rates led to higher mountain water table elevations and increasingly prominent local flow systems, primarily resulting in increased seepage within the mountain landscape and nonlinear increases in mountain block recharge to the valley. Valley aquifers were found to be relatively insensitive to changing mountain water tables, particularly in structurally isolated aquifers inside the fold and fault belt.

  16. Intercomparison of Groundwater Flow Monitoring Technologies at Site OU 1, Former Fort Ord, California

    SciTech Connect

    Daley, P F; Jantos, J; Pedler, W H; Mandell, W A

    2005-09-20

    This report presents an intercomparison of three groundwater flow monitoring technologies at a 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, California. Soil and groundwater at this site became contaminated by fuels and solvents that were burned on a portion of OU 1 called the Fire Drill Area (FDA) as part of firefighter training from 1962 and 1985. Cont Contamination is believed to be restricted to the unconfined A-aquifer, where water is reached at a depth of approximately 60 to 80 feet below the ground surface; the aquifer is from 15 to 20 feet in thickness, and is bounded below by a dense clay layer, the Salinas Valley Aquitard. Soil excavation and bioremediation were initiated at the site of fire training activities in the late 1980s. Since that time a pump-and-treat operation has been operated close to the original area of contamination, and this system has been largely successful at reducing groundwater contamination in this source area. However, a trichloroethylene (TCE) groundwater plume extends approximately 3000 ft (900 m) to the northwest away from the FDA. In this report, we have augmented flow monitoring equipment permanently installed in an earlier project (Oldenburg et al., 2002) with two additional flow monitoring devices that could be deployed in existing monitoring wells, in an effort to better understand their performance in a nearly ideal, homogeneous sand aquifer, that we expected would exhibit laminar groundwater flow owing to the site's relatively simple hydrogeology. The three flow monitoring tools were the Hydrotechnics{reg_sign} In In-Situ Permeable Flow Sensor (ISPFS), the RAS Integrated Subsurface Evaluation Hydrophysical Logging tool (HPL), and the Lawrence Livermore National Laboratory Scanning Colloidal Borescope Flow Meter (SCBFM). All three devices produce groundwater flow velocity measurements, and the ISPFS and SCBFM systems also gene generate flow direction rate estimates. The ISPFS probes are permanently installed and are non-retrievable, but produce long-term records with essentially no operator intervention or maintenance. The HPL and SCBFM systems are lightweight, portable logging devices that employ recording of electrical conductivity changes in wells purged with deionized water (HPL), or imaging of colloidal particles traversing the borehole (SCBFM) as the physical basis for estimating the velocity of groundwater flow through monitoring wells. All three devices gave estimates of groundwater velocity that were in reasonable agreement. However, although the ISPFS produced groundwater azimuth data that correlated well with conventional conductivity and gradient analyses of the groundwater flow field, the SCBFM direction data were in poor agreement. Further research into the reasons for this lack of correlation would seem to be warranted, given the ease of deployment of this tool in existing conventional monitoring wells, and its good agreement with the velocity estimates of the other technologies examined.

  17. Complex groundwater flow systems as traveling agent models

    E-print Network

    López-Corona, Oliver; Escolero, Oscar; González, Tomás; Morales-Casique, Eric

    2014-01-01

    Analyzing field data from pumping tests, we show that as with many other natural phenomena, groundwater flow exhibits a complex dynamics described by 1/f power spectrum. This result is theoretically studied within an agent perspective. Using a traveling agent model, we prove that this statistical behavior emerges when the medium is complex. Some heuristic reasoning is provided to justify both spatial and dynamic complexity, as the result of the superposition of an infinite number of stochastic processes. Even more, we show that this implies that non-Kolmogorovian probability is needed for its study, and provide a set of new partial differential equations for groundwater flow.

  18. Complex groundwater flow systems as traveling agent models

    PubMed Central

    Padilla, Pablo; Escolero, Oscar; González, Tomas; Morales-Casique, Eric; Osorio-Olvera, Luis

    2014-01-01

    Analyzing field data from pumping tests, we show that as with many other natural phenomena, groundwater flow exhibits complex dynamics described by 1/f power spectrum. This result is theoretically studied within an agent perspective. Using a traveling agent model, we prove that this statistical behavior emerges when the medium is complex. Some heuristic reasoning is provided to justify both spatial and dynamic complexity, as the result of the superposition of an infinite number of stochastic processes. Even more, we show that this implies that non-Kolmogorovian probability is needed for its study, and provide a set of new partial differential equations for groundwater flow. PMID:25337455

  19. A Method to Evaluate Groundwater flow system under the Seabed

    NASA Astrophysics Data System (ADS)

    Kohara, N.; Marui, A.

    2011-12-01

    A rapid increase of population in the world causes growth of water demands, and this may result worldwide water shortage in future. Especially, in the coastal area, water resource development becomes important because the half of the world population is concentrated in this area. Recently, countermeasures to mitigate climate change are discussed. Coastal area is one of the promising places for disposal of high-level nuclear waste or carbon dioxide capture and storage. Lots of development will be conducted in the coastal areas, however there are a lot of uncertainties remaining to understand the hydrogeological environment in there. It has been said that salt water / fresh water interface is formed in the place where meteoric fresh groundwater and salt groundwater from the ocean meet, and there is a large amount of groundwater discharge on the seafloor of the end of this interface so far. Recently, there is a lot of research about this submarine groundwater discharge because of the protection of the coastal ecosystem. In addition, there is a report that fresh water under the seabed was discovered on the continental shelf away from a present coastline by tens of kilometers in many parts of the world, because recently offshore drilling technology has been improving. Classical theory about formulation of salt water / fresh water interface could not explain completely, and consideration of longterm geochemical process (e.g., sea level fluctuations) is needed to understand this mechanism. Fresh (or brackish) groundwater under the seabed have been found on the investigation related to a seabed resources exploration in the field of coal mining, oceanic engineering works such as submarine tunnels, the atomic research, and the collection investigations of the basic data in the earth science field. A lot of fresh water under the seabed is confirmed on the offshore side from a present coastline as for these cases, and it is suggested that the end position of the salt water / fresh water interface (position of the submarine groundwater discharge) may appear on the seafloor. Moreover, neither the salinity concentration nor the groundwater age depends on depth. It is thought that it is because that the groundwater forms the complex flow situation through the change in a long-term groundwater flow system. The technology to understand the coastal groundwater flow consists of remote sensing, geographical features analysis, surface of the earth investigation, geophysical exploration, drilling survey, and indoor examination and the measurement. Integration of each technology is needed to interpret groundwater flow system because the one is to catch the local groundwater flow in the time series and another one is to catch the long-term and regional groundwater flow in the general situation. The purpose of this study is to review the previous research of coastal groundwater flow, and to integrate an applicable evaluation approach to understand this mechanism. In this presentation, the review of the research and case study using numerical simulation are introduced.

  20. Assessing the groundwater fortunes of aquifers in the White Volta Basin, Ghana: An application of numerical groundwater flow modeling and isotopic studies

    NASA Astrophysics Data System (ADS)

    Oteng, F. M.; Yidana, S. M.; Alo, C. A.

    2012-12-01

    Effective development and informed management of groundwater resources represent a critical opportunity for improved rural water supply in Ghana and enhanced livelihoods particularly in the northern part of the White Volta Basin, a region already prone to a myriad of water-related infirmities. If adequately developed, the resource will form a sufficient buffer against the effects of climate change/variability and foster food security and sustainable livelihoods among the largely peasant communities in the region. This research presents the results of a preliminary assessment of the hydrogeological conditions and recharge regimes of the aquifers in the Northern parts of the White Volta Basin, Ghana. Results of estimates of groundwater recharge through the conventional isotopic and mass balance techniques are presented. Details of the groundwater flow pattern and preliminary delineation of local and regional groundwater recharge areas are presented from initial simulations of the hydrogeological system with a robust groundwater flow simulation code, MODFLOW, in the Groundwater Modeling System, GMS, version 7.1. The stream flow and evapotranspiration components of the program were activated to incorporate surface flow processes, so that the resulting model represents the conditions of the entire hydrological system. The results of this study form a platform for detailed numerical assessment of the conditions of the aquifers in the area under transient conditions of fluctuating rainfall patterns in the face of climate change/variability.

  1. The in situ permeable flow sensor: A device for measuring groundwater flow velocity

    SciTech Connect

    Ballard, S.; Barker, G.T.; Nichols, R.L.

    1994-03-01

    A new technology called the In Situ Permeable Flow Sensor has been developed at Sandia National Laboratories. These sensors use a thermal perturbation technique to directly measure the direction and magnitude of the full three dimensional groundwater flow velocity vector in unconsolidated, saturated, porous media. The velocity measured is an average value characteristic of an approximately 1 cubic meter volume of the subsurface. During a test at the Savannah River Site in South Carolina, two flow sensors were deployed in a confined aquifer in close proximity to a well which was screened over the entire vertical extent of the aquifer and the well was pumped at four different pumping rates. In this situation horizontal flow which is radially directed toward the pumping well is expected. The flow sensors measured horizontal flow which was directed toward the pumping well, within the uncertainty in the measurements. The observed magnitude of the horizontal component of the flow velocity increased linearly with pumping rate, as predicted by theoretical considerations. The measured horizontal component of the flow velocity differed from the predicted flow velocity, which was calculated with the assumptions that the hydraulic properties of the aquifer were radially homogeneous and isotropic, by less than a factor of two. Drawdown data obtained from other wells near the pumping well during the pump test indicate that the hydraulic properties of the aquifer are probably not radially homogeneous but the effect of the inhomogeneity on the flow velocity field around the pumping well was not modeled because the degree and distribution of the inhomogeneity are unknown. Grain size analysis of core samples from wells in the area were used to estimate the vertical distribution of hydraulic conductivity.

  2. Estimating natural background groundwater chemistry, Questa molybdenum mine, New Mexico

    USGS Publications Warehouse

    Verplanck, Phillip L.; Nordstrom, D Kirk; Plumlee, Geoffrey S.; Walker, Bruce M.

    2010-01-01

    This 2 1/2 day field trip will present an overview of a U.S. Geological Survey (USGS) project whose objective was to estimate pre-mining groundwater chemistry at the Questa molybdenum mine, New Mexico. Because of intense debate among stakeholders regarding pre-mining groundwater chemistry standards, the New Mexico Environment Department and Chevron Mining Inc. (formerly Molycorp) agreed that the USGS should determine pre-mining groundwater quality at the site. In 2001, the USGS began a 5-year, multidisciplinary investigation to estimate pre-mining groundwater chemistry utilizing a detailed assessment of a proximal natural analog site and applied an interdisciplinary approach to infer pre-mining conditions. The trip will include a surface tour of the Questa mine and key locations in the erosion scar areas and along the Red River. The trip will provide participants with a detailed understanding of geochemical processes that influence pre-mining environmental baselines in mineralized areas and estimation techniques for determining pre-mining baseline conditions.

  3. Approaches to the simulation of unconfined flow and perched groundwater flow in MODFLOW

    USGS Publications Warehouse

    Bedekar, Vivek; Niswonger, Richard G.; Kipp, Kenneth; Panday, Sorab; Tonkin, Matthew

    2012-01-01

    Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings.

  4. The impact of storativity on mixing in fluctuating groundwater flow

    NASA Astrophysics Data System (ADS)

    Pool, M.; Post, V.; Simmons, C. T.

    2013-12-01

    Mixing and dispersion in groundwater systems are dominated by spatial heterogeneity and temporal flow fluctuations. It has been found that fluctuations parallel to the main flow directions only mildly impact on solute dispersion and have little influence on mixing if the medium is homogeneous (de Dreuzy et al., 2007; Kinzelbach and Ackerer, 1986; Goode and Konikow, 1990). However, most these findings were obtained under the pseudo steady state assumption, that is zero storativity, which implies an instantaneous flow response to hydraulic perturbation. With non-zero storativity, fluctuations in the flow boundary conditions propagate through the aquifer with a finite speed, which leads to a more complex time-dependent flow field. This is particularly important for tidally dominated coastal aquifers where accurate quantification of mixing is essential for achieving ground-water sustainability. The strategic objective of this study is to identify the interplay between temporal fluctuations, storativity and mixing. We perform two and three-dimensional simulations of transient flow and solute transport under velocity-dependent local scale dispersion. Mixing is characterized by the spatial moments of concentration. The enhanced solute mixing is quantified by an apparent dispersion coefficient. We systematically analyze the dependence of this dispersion coefficient on fluctuation amplitude, period, as well as storativity. Most importantly, we find that solute dispersion increases consistently with storativity. This may have important implications for the understanding of mixing and reaction processes in unconfined groundwater systems. References: -de Dreuzy, J-R. ; Carrera, J. ; Dentz, M. ; Le Borgne, T. (2012) Asymptotic dispersion for two-dimensional highly heterogeneous permeability fields under temporally fluctuating flow, Water Resour. Res., 48, W01532 -Kinzelbach, W., and P. Ackerer (1986), Mode'isation de la propagation d'un contaminant dans un champ d'e'coulement transitoire, Hydroge'ologie, 2, 197-206. -Goode, D. J., and L. F. Konikow (1990), Apparent dispersion in transient groundwater flow, Water Resour. Res., 26(10), 2339-2351.

  5. MODELLING GROUNDWATER FLOW ON THE REGIONAL SCALE IN THE UPPER DANUBE CATCHMENT (GERMANY)

    E-print Network

    Cirpka, Olaf Arie

    MODELLING GROUNDWATER FLOW ON THE REGIONAL SCALE IN THE UPPER DANUBE CATCHMENT (GERMANY) Roland.barthel@iws.uni-stuttgart.de Abstract. A groundwater flow model for the Upper Danube catchment (A=77,000km2 at gauge Passau, Germany coupled models. Modelling of groundwater flow, using coupled deterministic and hydrological approaches

  6. Characterization and conceptualization of groundwater flow systems: Chapter 2

    USGS Publications Warehouse

    Plummer, L.N.; Sanford, W.E.; Glynn, P.D.

    2013-01-01

    This chapter discusses some of the fundamental concepts, data needs and approaches that aid in developing a general understanding of a groundwater system. Principles of the hydrological cycle are reviewed; the processes of recharge and discharge in aquifer systems; types of geological, hydrological and hydraulic data needed to describe the hydrogeological framework of an aquifer system; factors affecting the distribution of recharge to aquifers; and uses of groundwater chemistry, geochemical modelling, environmental tracers and age interpretations in groundwater studies. Together, these concepts and observations aid in developing a conceptualization of groundwater flow systems and provide input to the development of numerical models of a flow system. Conceptualization of the geology, hydrology, geochemistry, and hydrogeological and hydrochemical framework can be quite useful in planning, study design, guiding sampling campaigns, acquisition of new data and, ultimately, developing numerical models capable of assessing a wide variety of societal issues — for example, sustainability of groundwater resources in response to real or planned withdrawals from the system, CO2 sequestration or other waste isolation issues (such as nuclear waste disposal).

  7. Application of Integral Pumping Tests to estimate the influence of losing streams on groundwater quality

    NASA Astrophysics Data System (ADS)

    Leschik, S.; Musolff, A.; Reinstorf, F.; Strauch, G.; Schirmer, M.

    2009-05-01

    Urban streams receive effluents of wastewater treatment plants and untreated wastewater during combined sewer overflow events. In the case of losing streams substances, which originate from wastewater, can reach the groundwater and deteriorate its quality. The estimation of mass flow rates Mex from losing streams to the groundwater is important to support groundwater management strategies, but is a challenging task. Variable inflow of wastewater with time-dependent concentrations of wastewater constituents causes a variable water composition in urban streams. Heterogeneities in the structure of the streambed and the connected aquifer lead, in combination with this variable water composition, to heterogeneous concentration patterns of wastewater constituents in the vicinity of urban streams. Groundwater investigation methods based on conventional point sampling may yield unreliable results under these conditions. Integral Pumping Tests (IPT) can overcome the problem of heterogeneous concentrations in an aquifer by increasing the sampled volume. Long-time pumping (several days) and simultaneous sampling yields reliable average concentrations Cav and mass flow rates Mcp for virtual control planes perpendicular to the natural flow direction. We applied the IPT method in order to estimate Mex of a stream section in Leipzig (Germany). The investigated stream is strongly influenced by combined sewer overflow events. Four pumping wells were installed up- and downstream of the stream section and operated for a period of five days. The study was focused on four inorganic (potassium, chloride, nitrate and sulfate) and two organic (caffeine and technical-nonylphenol) wastewater constituents with different transport properties. The obtained concentration-time series were used in combination with a numerical flow model to estimate Mcp of the respective wells. The difference of the Mcp's between up- and downstream wells yields Mex of wastewater constituents that increase downstream of the stream. In order to confirm the obtained Mcp's concentrations of additional measurements in the investigated stream were compared with the concentrations in the groundwater up- and downstream of the stream section. The results revealed increased Mcp's downstream of the stream section for chloride, potassium and nitrate, whereas Mcp of sulfate was decreased. Micropollutants caffeine and technical-nonylphenol showed decreased Mcp's downstream of the stream section in 75 % of the cases. Values of Mex could only be given for chloride, potassium, nitrate and caffeine. The comparison of concentrations in the stream with those in the groundwater points to the streambed as a zone where mass accumulation and degradation processes occur. The obtained results imply that the applied method can provide reliable data about the influence of losing streams on groundwater quality.

  8. Analysis of ground-water flow along a regional flow path of the Midwestern Basins and Arches aquifer system in Ohio

    USGS Publications Warehouse

    Hanover, R.H.

    1994-01-01

    A cross-sectional analysis of ground-water flow in central-western and northwestern Ohio was done as part of the Midwestern Basins and Arches Regional Aquifer-System Analysis project. The Midwestern Basins and Arches aquifer system is composed of carbonate bedrock of Silurian and Devonian age and overlying glacial flow analysis of the Scioto and Blanchard rivers in the study area were used to describe patrems of ground-water flow, to evaluate stream-aquifer interaction, and to quantify recharge and discharge within the ground-water-flow system along a regional ground-water-flow path. The selected regional flow path begins at a regional topographic high in Logan County, Ohio, and ends in Sandusky Bay (Lake Erie), a regional topographic low. Recharge to the ground-water system along the selected regional flow path was estimated from hydrograph separation of streamflow and averaged 3.24 inches per year. Computer model simulations indicate that 84 percent of the water entering the ground-water system flows less than 5 miles from point of recharge to point of discharge and no deeper than the upper surficial aquifers. The distance and depth that ground water travels and traveltime from point of recharge to point of discharge is controlled largely by where ground water enters the flow system. Ground water entering the flow system in the vicinity of major surface- water divides generally travels further, deeper, and longer than ground water entering the flow system elsewhere along the regional flow path. Particle tracking simulations substantiate the concept that the 80-mile-long regional flow path is within a continuous ground-water basin. Estimated traveltimes for ground-water from the regional high to Sandusky Bay range from 22,000 to 40,700 years, given a range of porosities from 8 to 22 percent for the carbonate-rock aquifer.

  9. A Geostatistical Data Assimilation Approach for Estimating Groundwater Plume Distributions From

    E-print Network

    Michalak, Anna M.

    , groundwater contamination is detected by a small number of fortuitously-located groundwater wells or moni73 A Geostatistical Data Assimilation Approach for Estimating Groundwater Plume Distributions From Engineering, University of Michigan, Ann Arbor, Michigan, USA Knowledge of the distribution of groundwater

  10. Validation Analysis of the Shoal Groundwater Flow and Transport Model

    SciTech Connect

    A. Hassan; J. Chapman

    2008-11-01

    Environmental restoration at the Shoal underground nuclear test is following a process prescribed by a Federal Facility Agreement and Consent Order (FFACO) between the U.S. Department of Energy, the U.S. Department of Defense, and the State of Nevada. Characterization of the site included two stages of well drilling and testing in 1996 and 1999, and development and revision of numerical models of groundwater flow and radionuclide transport. Agreement on a contaminant boundary for the site and a corrective action plan was reached in 2006. Later that same year, three wells were installed for the purposes of model validation and site monitoring. The FFACO prescribes a five-year proof-of-concept period for demonstrating that the site groundwater model is capable of producing meaningful results with an acceptable level of uncertainty. The corrective action plan specifies a rigorous seven step validation process. The accepted groundwater model is evaluated using that process in light of the newly acquired data. The conceptual model of ground water flow for the Project Shoal Area considers groundwater flow through the fractured granite aquifer comprising the Sand Springs Range. Water enters the system by the infiltration of precipitation directly on the surface of the mountain range. Groundwater leaves the granite aquifer by flowing into alluvial deposits in the adjacent basins of Fourmile Flat and Fairview Valley. A groundwater divide is interpreted as coinciding with the western portion of the Sand Springs Range, west of the underground nuclear test, preventing flow from the test into Fourmile Flat. A very low conductivity shear zone east of the nuclear test roughly parallels the divide. The presence of these lateral boundaries, coupled with a regional discharge area to the northeast, is interpreted in the model as causing groundwater from the site to flow in a northeastward direction into Fairview Valley. Steady-state flow conditions are assumed given the absence of groundwater withdrawal activities in the area. The conceptual and numerical models were developed based upon regional hydrogeologic investigations conducted in the 1960s, site characterization investigations (including ten wells and various geophysical and geologic studies) at Shoal itself prior to and immediately after the test, and two site characterization campaigns in the 1990s for environmental restoration purposes (including eight wells and a year-long tracer test). The new wells are denoted MV-1, MV-2, and MV-3, and are located to the northnortheast of the nuclear test. The groundwater model was generally lacking data in the north-northeastern area; only HC-1 and the abandoned PM-2 wells existed in this area. The wells provide data on fracture orientation and frequency, water levels, hydraulic conductivity, and water chemistry for comparison with the groundwater model. A total of 12 real-number validation targets were available for the validation analysis, including five values of hydraulic head, three hydraulic conductivity measurements, three hydraulic gradient values, and one angle value for the lateral gradient in radians. In addition, the fracture dip and orientation data provide comparisons to the distributions used in the model and radiochemistry is available for comparison to model output. Goodness-of-fit analysis indicates that some of the model realizations correspond well with the newly acquired conductivity, head, and gradient data, while others do not. Other tests indicated that additional model realizations may be needed to test if the model input distributions need refinement to improve model performance. This approach (generating additional realizations) was not followed because it was realized that there was a temporal component to the data disconnect: the new head measurements are on the high side of the model distributions, but the heads at the original calibration locations themselves have also increased over time. This indicates that the steady-state assumption of the groundwater model is in error. To test the robustness of the model d

  11. FTWORK: A three-dimensional groundwater flow and solute transport code

    SciTech Connect

    Faust, C.R.; Sims, P.N.; Spalding, C.P.; Andersen, P.F. ); Stephenson, D.E. )

    1990-01-01

    The three-dimensional, finite-difference model, FTWORK, may be used to simulate groundwater flow and solute transport processes in fully saturated porous media. The model solves the flow and transport equations separately. Transport mechanisms considered include: advection, hydrodynamic dispersion, adsorption, and radioactive decay. This version of FTWORK also provides for parameter estimation of the steady-state flow applications. Also included in this version is a subroutine that allows linkage with a particle tracking program, GEOTRACK. 20 refs., 51 figs., 31 tabs.

  12. Bias in groundwater samples caused by wellbore flow

    USGS Publications Warehouse

    Reilly, Thomas E.; Franke, O. Lehn; Bennett, Gordon D.

    1989-01-01

    Proper design of physical installations and sampling procedures for groundwater monitoring networks is critical for the detection and analysis of possible contaminants. Monitoring networks associated with known contaminant sources sometimes include an array of monitoring wells with long well screens. The purpose of this paper is: (a) to report the results of a numerical experiment indicating that significant borehole flow can occur within long well screens installed in homogeneous aquifers with very small head differences in the aquifer (less than 0.01 feet between the top and bottom of the screen); (b) to demonstrate that contaminant monitoring wells with long screens may completely fail to fulfill their purpose in many groundwater environments.

  13. MODIS-aided statewide net groundwater-recharge estimation in Nebraska.

    PubMed

    Szilagyi, Jozsef; Jozsa, Janos

    2013-01-01

    Monthly evapotranspiration (ET) rates (2000 to 2009) across Nebraska at about 1-km resolution were obtained by linear transformations of the MODIS (MODerate resolution Imaging Spectroradiometer) daytime surface temperature values with the help of the Priestley-Taylor equation and the complementary relationship of evaporation. For positive values of the mean annual precipitation and ET differences, the mean annual net recharge was found by an additional multiplication of the power-function-transformed groundwater vulnerability DRASTIC-code values. Statewide mean annual net recharge became about 29 mm (i.e., 5% of mean annual precipitation) with the largest recharge rates (in excess of 100 mm/year) found in the eastern Sand Hills and eastern Nebraska. Areas with the largest negative net recharge rates caused by declining groundwater levels due to large-scale irrigation are found in the south-western region of the state. Error bounds of the estimated values are within 10% to 15% of the corresponding precipitation rates and the estimated net recharge rates are sensitive to errors in the precipitation and ET values. This study largely confirms earlier base-flow analysis-based statewide groundwater recharge estimates when considerations are made for differences in the recharge definitions. The current approach not only provides better spatial resolution than available earlier studies for the region but also quantifies negative net recharge rates that become especially important in numerical modeling of shallow groundwater systems. PMID:23216050

  14. Groundwater availability as constrained by hydrogeology and environmental flows

    USGS Publications Warehouse

    Watson, Katelyn A.; Mayer, Alex S.; Reeves, Howard W.

    2014-01-01

    Groundwater pumping from aquifers in hydraulic connection with nearby streams has the potential to cause adverse impacts by decreasing flows to levels below those necessary to maintain aquatic ecosystems. The recent passage of the Great Lakes-St. Lawrence River Basin Water Resources?Compact has brought attention to this issue in the Great Lakes region. In particular, the legislation requires the Great Lakes states to enact measures for limiting water withdrawals that can cause adverse ecosystem impacts. This study explores how both hydrogeologic and environmental flow limitations may constrain groundwater availability in the Great Lakes Basin. A methodology for calculating maximum allowable pumping rates is presented. Groundwater availability across the basin may be constrained by a combination of hydrogeologic yield and environmental flow limitations varying over both local and regional scales. The results are sensitive to factors such as pumping time, regional and local hydrogeology, streambed conductance, and streamflow depletion limits. Understanding how these restrictions constrain groundwater usage and which hydrogeologic characteristics and spatial variables have the most influence on potential streamflow depletions has important water resources policy and management implications.

  15. Estimation of shallow ground-water recharge in the Great Lakes basin

    USGS Publications Warehouse

    Neff, B.P.; Piggott, A.R.; Sheets, R.A.

    2006-01-01

    This report presents the results of the first known integrated study of long-term average ground-water recharge to shallow aquifers (generally less than 100 feet deep) in the United States and Canada for the Great Lakes, upper St. Lawrence, and Ottawa River Basins. The approach used was consistent throughout the study area and allows direct comparison of recharge rates in disparate parts of the study area. Estimates of recharge are based on base-flow estimates for streams throughout the Great Lakes Basin and the assumption that base flow in a given stream is equal to the amount of shallow ground-water recharge to the surrounding watershed, minus losses to evapotranspiration. Base-flow estimates were developed throughout the study area using a single model based on an empirical relation between measured base-flow characteristics at streamflow-gaging stations and the surficial-geologic materials, which consist of bedrock, coarse-textured deposits, fine-textured deposits, till, and organic matter, in the surrounding surface-water watershed. Model calibration was performed using base-flow index (BFI) estimates for 959 stations in the U.S. and Canada using a combined 28,784 years of daily streamflow record determined using the hydrograph-separation software program PART. Results are presented for watersheds represented by 8-digit hydrologic unit code (HUC, U.S.) and tertiary (Canada) watersheds. Recharge values were lowest (1.6-4.0 inches/year) in the eastern Lower Peninsula of Michigan; southwest of Green Bay, Wisconsin; in northwestern Ohio; and immediately south of the St. Lawrence River northeast of Lake Ontario. Recharge values were highest (12-16.8 inches/year) in snow shadow areas east and southeast of each Great Lake. Further studies of deep aquifer recharge and the temporal variability of recharge would be needed to gain a more complete understanding of ground-water recharge in the Great Lakes Basin.

  16. Comparison of groundwater flow model particle tracking results and isotopic data in the Leon valley, Mexico

    NASA Astrophysics Data System (ADS)

    Hernandez-Garcia, G.; Cortes, A. S.; Martínez-Reyes, J.; Perez-Quezadas, J.; Grupo de Hidrologia Isotopica

    2013-05-01

    The study area is located in the Guanajuato state, north-west of Mexico City. The Leon Valley covers with groundwater its water demand estimated in about 20.6 m3/s. The constant population increase and related economic activities in the region have a steady growth in water needs. Related abstraction rate has produced an average drawdown of about 1.0 m/year in the last two decades. It suggests that present groundwater management needs to be reviewed. The groundwater management in the study area implies a possibility that abstraction will produce environmental impacts. This vital resource under stress becomes necessary to study its hydro-geologic functioning to achieve a scientific groundwater management in the valley. This investigation was based on the analysis and integration of existing information and the one generated in the field by the authors. Highlighted concepts were: i) the geologic structure of the area, ii) the hydraulic parameters and iii) the delta-deuterium and delta-oxigen-18 composition. This information was analysed integrally by means of applying a groundwater flow model (MODFLOW) and a particle-tracking model (FLOWPATH): the results were similar to flow paths and time-of travel interpretations derived from isotopic data.

  17. Econometric Estimation of Groundwater Pumping Costs: A Simultaneous Equations Approach

    NASA Astrophysics Data System (ADS)

    Kanazawa, Mark T.

    1992-06-01

    Recent studies have attempted econometric estimation of the effect of changing groundwater costs on various dimensions of agricultural behavior. These studies assume parametric cost values, ignoring the possibility that marginal pumping costs may be endogenous to the extent of pumping activity. Under the alternative assumption of increasing marginal pumping costs, existing estimates of various elasticities may be suspect due to specification bias. This paper investigates this possibility, modeling a pumping technology based on hydrologic principles which incorporates constant pumping costs as a limiting case. The model also allows for common pool externalities when agents pump groundwater from the same aquifer. The results of the econometric analysis strongly suggest the presence of increasing marginal pumping costs for farmers in our data sample.

  18. Modeling Groundwater Flow using both Neumann and Dirichlet Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Zijl, Wouter; El-Rawy, Mustafa; Batelaan, Okke

    2013-04-01

    In groundwater flow models it is customary to use the recharge rate, obtained from measured precipitation minus run off and evapotranspiration, as the top boundary condition (a Neumann boundary condition). However, as has been emphasized by Tóth (1962; 2009), the topography of the water table offers a better boundary condition (a Dirichlet boundary condition), because it leads to the delineation of flow systems and stagnation zones. However, in practical modeling studies the recharge rates obtained when using the Dirichlet boundary condition may turn out to be unrealistically small or large. To remediate this we have developed an unconventional modeling procedure that is based on both the Neumann and the Dirichlet boundary condition on the phreatic surface. Such a model does not only calculate the heads and fluxes, but also an update of the initially perceived hydraulic conductivities, in such a way that the initially perceived conductivity model is preserved as much as possible. For given grid block conductivities, numerical groundwater models (e.g. MODFLOW) are linear in the heads. However, for given heads the numerical models are not linear in the grid block conductivities. Mohammed et al. (2009) have developed a MODFLOW-compatible numerical model that is linear in the stream functions for given grid block conductivities, while it is also linear in the grid block resistivities (inverse of conductivities) if the heads are given. Unconventional modeling is based on this bi-linearity. Assume we specify a reasonable perception of the hydraulic conductivities and determine the numerical solution with Neumann boundary conditions. The resulting fluxes are then substituted into the stream function model, together with Dirichlet boundary conditions, and the grid block resistivities can then be determined by a standard routine for solving systems of linear algebraic equations. The thus calibrated grid block conductivities do not deviate much from the initially perceived conductivity model and honor all the Dirichlet and Neumann boundary data. This so called Constrained Back Projection (CBP) has been developed by Mohammed et al. (2009) and exemplified for synthetic problems. The method is well suited to determine conductivities in ten to hundreds of zones, but solving the algebraic system for thousands to millions of grid block conductivities becomes problematic. A related idea has already been proposed in the 1980s by Wexler (Wexler et al., 1985; Yorkey and Webster, 1987; Kohn and Vogelius, 1987; Wexler, 1988; Kohn and McKenney, 1990) in the context of electric impedance tomography for geophysical and medical imaging. El-Rawy et al. (2010, 2011) has developed and validated this so-called Double Constraint Method (DCM) in the context of hydrogeology and groundwater flow, with applications to two case studies in Belgium. DCM can handle MODFLOW models with thousands to millions of grid block conductivities, but is not very suitable for zonation and is, therefore, complementary to CBP. Application of DCM under a number of different hydrogeological conditions makes the estimate of the hydraulic conductivities more accurate by using a Kalman Filter.

  19. 2007 Estimated International Energy Flows

    SciTech Connect

    Smith, C A; Belles, R D; Simon, A J

    2011-03-10

    An energy flow chart or 'atlas' for 136 countries has been constructed from data maintained by the International Energy Agency (IEA) and estimates of energy use patterns for the year 2007. Approximately 490 exajoules (460 quadrillion BTU) of primary energy are used in aggregate by these countries each year. While the basic structure of the energy system is consistent from country to country, patterns of resource use and consumption vary. Energy can be visualized as it flows from resources (i.e. coal, petroleum, natural gas) through transformations such as electricity generation to end uses (i.e. residential, commercial, industrial, transportation). These flow patterns are visualized in this atlas of 136 country-level energy flow charts.

  20. Estimated ground-water discharge by evapotranspiration, Ash Meadows Area, Nye County, Nevada, 1994

    SciTech Connect

    Nichols, W.D.; Laczniak, R.J.; DeMeo, G.A.; Rapp, T.R.

    1997-05-01

    Ground water discharges from the regional ground-water flow system that underlies the eastern part of the Nevada Test Site through numerous springs and seeps in the Ash Meadows National Wildlife Refuge in southern Nevada. The total spring discharge was estimated to be about 17,000 acre-feet per year by earlier studies. Previous studies estimated that about 10,500 acre-feet of this discharge was lost to evapotranspiration. The present study was undertaken to develop a more rigorous approach to estimating ground-water discharge in the Ash Meadows area. Part of the study involves detailed field investigation of evapotranspiration. Data collection began in early 1994. The results of the first year of study provide a basis for making preliminary estimates of ground-water discharge by evapotranspiration. An estimated 13,100 acre-feet of ground water was evapotranspired from about 6,800 acres of marsh and salt-grass. Additional 3,500 acre-feet may have been transpired from the open water and from about 1,460 acres of other areas of Ash Meadows in which field studies have not yet been made.

  1. A method to estimate groundwater depletion from confining layers

    USGS Publications Warehouse

    Konikow, L.F.; Neuzil, C.E.

    2007-01-01

    Although depletion of storage in low-permeability confining layers is the source of much of the groundwater produced from many confined aquifer systems, it is all too frequently overlooked or ignored. This makes effective management of groundwater resources difficult by masking how much water has been derived from storage and, in some cases, the total amount of water that has been extracted from an aquifer system. Analyzing confining layer storage is viewed as troublesome because of the additional computational burden and because the hydraulic properties of confining layers are poorly known. In this paper we propose a simplified method for computing estimates of confining layer depletion, as well as procedures for approximating confining layer hydraulic conductivity (K) and specific storage (Ss) using geologic information. The latter makes the technique useful in developing countries and other settings where minimal data are available or when scoping calculations are needed. As such, our approach may be helpful for estimating the global transfer of groundwater to surface water. A test of the method on a synthetic system suggests that the computational errors will generally be small. Larger errors will probably result from inaccuracy in confining layer property estimates, but these may be no greater than errors in more sophisticated analyses. The technique is demonstrated by application to two aquifer systems: the Dakota artesian aquifer system in South Dakota and the coastal plain aquifer system in Virginia. In both cases, depletion from confining layers was substantially larger than depletion from the aquifers.

  2. Recent Developments in Karst Groundwater Flow Measurement in Southeastern Florida,USA

    NASA Astrophysics Data System (ADS)

    Krupa, S.; Brock, J.; Gefvert, C.; Shaffer, J.; Cunningham, K.; Wacker, M.

    2008-05-01

    Groundwater seepage was first characterized in the early 1800's, when Henry Darcy determined that the flow of groundwater could be estimated from the head difference and the distance between two points. Since then, hydrogeologists have been struggling with ways to continuously measure groundwater flow in situ, and more recently have sought data in near-real time. Groundwater flow within aquifers that have relatively large head differences (several meters) are porous in nature and have low hydraulic conductivities, is linear in nature, and can be generally characterized by Darcy's solution. Prior to the research presented herein, it was assumed that aquifers within Miami-Dade County could also be characterized by Darcy's solution (with Reynolds numbers less than 10 or 20). The L-31N Canal lies on the eastern flank of Everglades National Park (ENP). In addition to conveying water to Florida Bay and Biscayne Bay, the canal's levees are intended to reduce surface-water sheet flow from ENP to eastern urban areas. In an effort to reduce groundwater seepage coming from ENP, the South Florida Water Management District (SFWMD) and the United States Army Corp of Engineers (USACE) have been tasked with evaluating the hydrogeology and the groundwater/surface-water interaction on the L-31N canal. This involved process of installation includes monitoring wells, recording automated water-level measurements, characterizing water-chemistry types and ages, and installation of instruments capable of measuring horizontal groundwater velocities and directions coming from ENP. The SFWMD initiated a cooperative agreement with the United States Geological Survey (USGS) for the geological and hydrogeological investigation and concurrently contracted the installation of borehole flowmeters in eight wells (two clusters). The USGS provided detailed core and sediment analysis, geophysical logging, in situ borehole flowmeter logging, and digital optical borehole imaging. In addition, the USGS produced a hydrogeologic cross-section using the new borehole data. The USGS delineated high-frequency cycles (HFCs) within the study area. The high-frequency cycles form the fundamental building blocks of the rocks composing the Biscayne aquifer. Vertical lithofacies successions, which have stacking patterns that reoccur, fit within the high-frequency cycles. An important observation is that a predictable vertical pattern of macroporosity and permeability commonly exists within the high-frequency cycles, thus preferential flow passageways can be constrained by the lower and upper cycle boundaries. In southeastern Florida, specific HFCs can contain relatively high hydraulic conductivities and vertical head gradients within centimeters of each other. This combination of high hydraulic conductivities (estimated at 1500 to 3000 m/d) and nearly flat water table gradients combine to convey large amounts of groundwater from ENP to the eastern urban areas, with the water ultimately discharging into Biscayne Bay. Horizontal groundwater flow velocity was measured with horizontal heat-pulse flowmeters installed in eight monitoring wells located on the western levee of the L-31N canal. Results show that flow velocity in the shallow wells (5.1 m in depth) is coupled to the surface water as measured by well water levels. A groundwater rise of about 0.5 m during the wet season of September-December 2007 led to a six-fold increase in horizontal groundwater flow rates.

  3. Estimation of methane concentrations and loads in groundwater discharge to Sugar Run, Lycoming County, Pennsylvania

    USGS Publications Warehouse

    Heilweil, Victor M.; Risser, Dennis W.; Conger, Randall W.; Grieve, Paul L.; Hynek, Scott A.

    2014-01-01

    A stream-sampling study was conducted to estimate methane concentrations and loads in groundwater discharge to a small stream in an active shale-gas development area of northeastern Pennsylvania. Grab samples collected from 15 streams in Bradford, Lycoming, Susquehanna, and Tioga Counties, Pa., during a reconnaissance survey in May and June 2013 contained dissolved methane concentrations ranging from less than the minimum reporting limit (1.0) to 68.5 micrograms per liter (µg/L). The stream-reach mass-balance method of estimating concentrations and loads of methane in groundwater discharge was applied to a 4-kilometer (km) reach of Sugar Run in Lycoming County, one of the four streams with methane concentrations greater than or equal to 5 µg/L. Three synoptic surveys of stream discharge and methane concentrations were conducted during base-flow periods in May, June, and November 2013. Stream discharge at the lower end of the reach was about 0.10, 0.04, and 0.02 cubic meters per second, respectively, and peak stream methane concentrations were about 20, 67, and 29 µg/L. In order to refine estimated amounts of groundwater discharge and locations where groundwater with methane discharges to the stream, the lower part of the study reach was targeted more precisely during the successive studies, with approximate spacing between stream sampling sites of 800 meters (m), 400 m, and 200 m, in May, June, and November, respectively. Samples collected from shallow piezometers and a seep near the location of the peak methane concentration measured in streamwater had groundwater methane concentrations of 2,300 to 4,600 µg/L. These field data, combined with one-dimensional stream-methane transport modeling, indicate groundwater methane loads of 1.8 ±0.8, 0.7 ±0.3, and 0.7 ±0.2 kilograms per day, respectively, discharging to Sugar Run. Estimated groundwater methane concentrations, based on the transport modeling, ranged from 100 to 3,200 µg/L. Although total methane load and the uncertainty in calculated loads both decreased with lower streamflow conditions and finer-resolution sampling in June and November, the higher loads during May could indicate seasonal variability in base flow. This is consistent with flowmeter measurements indicating that there was less inflow occurring at lower streamflow conditions during June and November.

  4. Heat flow and subsurface temperature as evidence for basin-scale ground-water flow, North Slope of Alaska

    USGS Publications Warehouse

    Deming, D.; Sass, J.H.; Lachenbruch, A.H.; De Rito, R. F.

    1992-01-01

    Several high-resolution temperature logs were made in each of 21 drillholes and a total of 601 thermal conductivity measurements were made on drill cuttings and cores. Near-surface heat flow (??20%) is inversely correlated with elevation and ranges from a low of 27 mW/m2 in the foothills of the Brooks Range in the south, to a high of 90 mW/m2 near the north coast. Subsurface temperatures and thermal gradients estimated from corrected BHTs are similarly much higher on the coastal plain than in the foothills province to the south. Significant east-west variation in heat flow and subsurface temperature is also observed; higher heat flow and temperature coincide with higher basement topography. The observed thermal pattern is consistent with forced convection by a topographically driven ground-water flow system. Average ground-water (Darcy) velocity in the postulated flow system is estimated to be of the order of 0.1 m/yr; the effective basin-scale permeability is estimated to be of the order of 10-14 m2. -from Authors

  5. Recharge and Lateral Groundwater Flow Boundary Conditions for the Saturated Zone Site-Scale Flow and Transport Model

    SciTech Connect

    S. James

    2004-10-06

    This analysis is designed to use existing modeling and analysis results as the basis for estimated groundwater flow rates into the saturated zone (SZ) site-scale model domains, both as recharge (infiltration) at the upper boundary (water table), and as underflow at the lateral boundaries. Specifically, this work compiles information on the recharge boundary conditions supplied to the base-case and alternate SZ site-scale flow models taken from (1) distributed recharge from the 1997 (D'Agnese et al. 1997 [DIRS 100131]) or 2001 (D'Agnese et al. 2002 [DIRS 158876]) SZ regional-scale (Death Valley Regional Flow System [DVRFS]) model; (2) recharge below the area of the 1997 (Wu et al. 1997 [DIRS 156453]) or 2003 (BSC 2004 [DIRS 169861]) unsaturated zone (UZ) site-scale flow model; and (3) focused recharge along Fortymile Wash. In addition, this analysis includes extraction of the groundwater flow rates simulated by the 1997 and 2001 DVRFS models coincident with the lateral boundaries of the SZ site-scale flow models. The fluxes from the 1997 DVRFS were used to calibrate the base-case SZ site-scale flow model. The 2001 DVRFS fluxes are used in the alternate SZ site-scale flow model.

  6. Ancient groundwater flow in the Valles Marineris on Mars inferred from

    E-print Network

    Treiman, Allan H.

    LETTERS Ancient groundwater flow in the Valles Marineris on Mars inferred from fault trace ridges e-mail: treiman@lpi.usra.edu Published online: XX Month XXXX; doi:10.1038/ngeoXXXX Groundwater of bedrock3­6 .2 Understanding groundwater flow is also important for assessing3 the possibility of past

  7. Multigrid for Higher Order Discontinuous Galerkin Finite Elements Applied to Groundwater Flow

    E-print Network

    Bastian, Peter

    Multigrid for Higher Order Discontinuous Galerkin Finite Elements Applied to Groundwater Flow Peter elements applied to the groundwater flow equation. It uses an incomplete LU decomposition on an element for diffusion problems has been formu- lated in [6]. 1.1 Notation In this paper we wish to solve the groundwater

  8. SPATIAL SCALING OF SURFACE WATER INFILTRATION AND ITS IMPLICATIONS FOR ESTIMATING GROUNDWATER RECHARGE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The GRAPHIC Project has identified priority research topics related to groundwater recharge, discharge, storage, and water quality. This presentation focuses on some physical aspects affecting spatial groundwater recharge estimation and uncertainty associated with spatial variability. Previous wor...

  9. MODOPTIM: A general optimization program for ground-water flow model calibration and ground-water management with MODFLOW

    USGS Publications Warehouse

    Halford, Keith J.

    2006-01-01

    MODOPTIM is a non-linear ground-water model calibration and management tool that simulates flow with MODFLOW-96 as a subroutine. A weighted sum-of-squares objective function defines optimal solutions for calibration and management problems. Water levels, discharges, water quality, subsidence, and pumping-lift costs are the five direct observation types that can be compared in MODOPTIM. Differences between direct observations of the same type can be compared to fit temporal changes and spatial gradients. Water levels in pumping wells, wellbore storage in the observation wells, and rotational translation of observation wells also can be compared. Negative and positive residuals can be weighted unequally so inequality constraints such as maximum chloride concentrations or minimum water levels can be incorporated in the objective function. Optimization parameters are defined with zones and parameter-weight matrices. Parameter change is estimated iteratively with a quasi-Newton algorithm and is constrained to a user-defined maximum parameter change per iteration. Parameters that are less sensitive than a user-defined threshold are not estimated. MODOPTIM facilitates testing more conceptual models by expediting calibration of each conceptual model. Examples of applying MODOPTIM to aquifer-test analysis, ground-water management, and parameter estimation problems are presented.

  10. ShowFlow: A practical interface for groundwater modeling

    SciTech Connect

    Tauxe, J.D.

    1990-12-01

    ShowFlow was created to provide a user-friendly, intuitive environment for researchers and students who use computer modeling software. What traditionally has been a workplace available only to those familiar with command-line based computer systems is now within reach of almost anyone interested in the subject of modeling. In the case of this edition of ShowFlow, the user can easily experiment with simulations using the steady state gaussian plume groundwater pollutant transport model SSGPLUME, though ShowFlow can be rewritten to provide a similar interface for any computer model. Included in this thesis is all the source code for both the ShowFlow application for Microsoft{reg sign} Windows{trademark} and the SSGPLUME model, a User's Guide, and a Developer's Guide for converting ShowFlow to run other model programs. 18 refs., 13 figs.

  11. Data Intensive Simulation and Analysis of Groundwater Flow and Transport in the Los Alamos aquifer

    NASA Astrophysics Data System (ADS)

    Mishra, P. K.; Harp, D.; Miller, T. A.; Vesselinov, V. V.

    2011-12-01

    Characterization of the groundwater flow and transport in regional aquifer systems is a challenging task. In most practical cases, there is not sufficient hydrogeologic information that can be applied to evaluate aquifer properties. In addition, the development, execution and analyses of large-scale numerical models are computational demanding requiring advanced high-performance codes and state-of-the-art computational resources. We have developed a complex 3D regional groundwater flow model of the regional aquifer beneath the Los Alamos National Laboratory (LANL) site to provide a better understanding of hydrogeologic properties, recharge sources, groundwater travel times, migration pathways for potential contaminants, and potential contaminant concentrations at water supply wells. The 3D computational grid is generated using sophisticated grid generating software, LaGriT (http://lagrit.lanl.gov). LaGriT allows the use of unstructured meshing strategies, which capture the details of complex groundwater flow of the LANL site, including wellbore geometries and hydrostratigraphy. The numerical simulation is performed using the FEHM (Finite Element Heat and Mass transfer) (http://fehm.lanl.gov) codes. Long-term groundwater level monitoring at LANL started in the mid-1940s; the monitoring data is currently collected at more than 70 regional monitoring wells providing an extensive water-level observation data set. The water-level data represent over 62 years of recorded drawdowns and recovery caused by the spatially and temporally variable pumping at six municipal water-supply wells. The water-level data is applied in the 3D flow model to inversely estimate the aquifer parameters. The model calibration, uncertainty quantification, and sensitivity analyses are performed using the code MADS (Model Analyses and Decision Support; http://ees.lanl.gov/staff/monty/codes/mads). The research utilizes high performance computational resources (multiprocessor clusters) at LANL. In this study, we present the challenges of model development, lessons learned, and insights provided by the model into the LANL aquifer.

  12. Geochemical and Isotopic Interpretations of Groundwater Flow in the Oasis Valley Flow System, Southern Nevada

    SciTech Connect

    J.M. Thomas; F.C. Benedict, Jr.; T.P. Rose; R.L. Hershey; J.B. Paces; Z.E. Peterman; I.M. Farnham; K.H. Johannesson; A.K. Singh; K.J. Stetzenbach; G.B. Hudson; J.M. Kenneally; G.F. Eaton; D.K. Smith

    2003-01-08

    This report summarizes the findings of a geochemical investigation of the Pahute Mesa-Oasis Valley groundwater flow system in southwestern Nevada. It is intended to provide geochemical data and interpretations in support of flow and contaminant transport modeling for the Western and Central Pahute Mesa Corrective Action Units.

  13. Improved Geothermal Heat Flux Estimates for East Antarctic Subglacial Basins from Groundwater Modeling and Geophysical Observations

    NASA Astrophysics Data System (ADS)

    Gooch, B. T.; Frederick, B. C.; Richter, T.; Young, D. A.; Blankenship, D. D.

    2013-12-01

    Slower moving, deep interior ice sheet behavior is largely dependent on basal ice conditions. Basal heat (from shearing friction and geothermal input) and subglacial water pressure heavily influence the dynamics of these regions. Numerical ice sheet models require accurate estimations of geothermal heat flux for calculating realistic basal melt rates and thermal structure in the ice. Current ice sheet models are poorly constrained with low-resolution satellite- or seismic-derived geothermal heat flux estimates that neglect upper crustal contributions. Higher-resolution estimates that take into account these effects while still incorporating the lower-resolution methodologies are needed to improve geothermal heat flux estimates for next-generation ice sheet models. The main contributions to these estimates come from delineations between crystalline basement rock and sedimentary basins as well as subglacial topography, with both influencing the geothermal gradient. The geothermal gradient can be heavily altered by groundwater flow in the sedimentary basins due to higher hydraulic permeability advecting heat. We present a new approach to better estimate the geothermal heat flux in the subglacial basins and mountain ranges in a region of Wilkes Land, East Antarctica. Our approach utilizes existing potential field and ice-penetrating radar data from aerogeophysical surveys to better define the upper crustal structure, including basin and range geometry. Potential field data is used to define probable 3D basin structure and sediment properties, while ice-penetrating radar is used to define subglacial bed conditions. Numerical modeling of heat flow through the upper crust with added radiogenic crystalline basement rock heat contributions is coupled to groundwater flow through the surrounding sedimentary basins to better estimate the total resulting geothermal heat flux at the ice-bed interface. These geophysical processing methods in conjunction with geothermal modeling can provide significantly improved geothermal heat flux estimates which could better constrain crucial parameters needed for ice sheet models.

  14. Mechanism and rate of denitrification in an agricultural watershed: Electron and mass balance along groundwater flow paths

    USGS Publications Warehouse

    Tesoriero, A.J.; Liebscher, H.; Cox, S.E.

    2000-01-01

    The rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer. Intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards. Both the extent and rate of denitrification varied depending on the groundwater flow path. While little or no denitrification occurred in much of the upland portions of the aquifer, a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer. In contrast, a sharp shallow redox gradient is observed adjacent to a third-order stream as aerobic groundwater enters reduced sediments. An essentially complete loss of nitrate concurrent with increases in excess N2 provide evidence that denitrification occurs as groundwater enters this zone. Electron and mass balance calculations suggest that iron sulfide (e.g., pyrite) oxidation is the primary source of electrons for denitrification. Denitrification rate estimates were based on mass balance calculations using nitrate and excess N2 coupled with groundwater travel times. Travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon-based age dates. Denitrification rates were found to vary considerably between the two areas where denitrification occurs. Denitrification rates in the deep, upland portions of the aquifer were found to range from < 0.01 to 0.14 mM of N per year; rates at the redoxcline along the shallow flow path range from 1.0 to 2.7 mM of N per year. Potential denitrification rates in groundwater adjacent to the stream may be much faster, with rates up to 140 mM per year based on an in situ experiment conducted in this zone.The rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer. Intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards. Both the extent and rate of denitrification varied depending on the groundwater flow path. While little or no denitrification occurred in much of the upland portions of the aquifer, a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer. In contrast, a sharp shallow redox gradient is observed adjacent to a third-order stream as aerobic groundwater enters reduced sediments. An essentially complete loss of nitrate concurrent with increases in excess N2 provide evidence that denitrification occurs as groundwater enters this zone. Electron and mass balance calculations suggest that iron sulfide (e.g., pyrite) oxidation is the primary source of electrons for denitrification. Denitrification rate estimates were based on mass balance calculations using nitrate and excess N2 coupled with groundwater travel times. Travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon-based age dates. Denitrification rates were found to vary considerably between the two areas where denitrification occurs. Denitrification rates in the deep, upland portions of the aquifer were found to range from <0.01 to 0.14 mM of N per year; rates at the redoxcline along the shallow flow path range from 1.0 to 2.7 mM of N per year. Potential denitrification rates in groundwater adjacent to the stream may be much faster, with rates up to 140 mM per year based on an in situ experiment conducted in this zone.

  15. Parallel Implementation of Finite Element Groundwater Flow Model

    NASA Astrophysics Data System (ADS)

    Kim, J. G.; Kim, J.

    2001-05-01

    The numerical simulation of subsurface fluid flow plays an important role in oil and water resources management industry. In reality, it is often required to incorporate the detail infomration of subsurface heterogeneities for modeling realistic flow behaviors. If a statistically accurate model is used to determine the heterogeneities of subsurface properties, several million grid cells are generated for computational domains. These fine resolution simulations require considerablely expensive computtaional cost. The linear and nonlinear solvers in the portable, extensible toolkit for scientific computation (PETSc) libarary provides robust numerical rotuines for solving such problems on parallel computers. In our first work, a two-dimensional finite-element model for modeling multiphase subsurface fluid flow was implemented on parallel computers using the PETSc routines. The preliminary result shows that considerable parallel performance (about 70 % parallel efficiency upto 32 processors) was observed on IBM SP machines. In most cases, it was observed that all of the PETSc provided Krylov subspace methods show the stable convergence behaviors in parallel processing with a model problem of 80,000 triangular finite elements. The detail results of convergence behavior and computational time of each parallel solver will be provided in this study. The work is extended for the parallel implementation of a three-dimensional finite element code for groundwater flow modeling. The major applications of the code are for modeling saturated-unsaturated groundwater flow and solute transport subject to various boundaty conditions, transport mechanisms, and highly nonlinear moisture conditions.

  16. On the mechanism of earthquake induced groundwater flow

    NASA Astrophysics Data System (ADS)

    Dudley Ward, Nicholas F.

    2015-11-01

    The Canterbury/Christchurch earthquakes and aftershocks of 2010-2011 generated groundwater level responses throughout New Zealand. However, the greater part of damage was sustained by the city of Christchurch which is built on a layered sequence of artesian aquifers. In a previous paper we analysed the earthquake induced groundwater responses. We quantified groundwater responses by fitting a simple statistical model which differentiated between immediate earthquake induced response (spike) and post-seismic change (offset). The most notable feature of this analysis was the consistency of responses between the earthquakes: deeper wells correlate with negative offset and shallower wells correlate with positive offset. In that paper we argued that this is consistent with the upwards vertical movement of water. In this paper we focus on the physical mechanisms, and consider a model that further explains and supports this hypothesis. We postulate a groundwater flow model in which storativity and aquitard permeability are modelled as time-varying shocks. We analyse the solutions for a range of non-dimensional parameters and obtain type curves that exhibit the same behaviour as the observed responses. Finally we consider data from the 2010 Mw 7.1 Darfield (Canterbury) earthquake.

  17. From groundwater baselines to numerical groundwater flow modelling for the Milan metropolitan area

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni B.; Frattini, Paolo; Peretti, Lidia; Villa, Federica; Gorla, Maurizio

    2015-04-01

    Contamination of major aquifers in highly densely populated areas is a major concern for stakeholders involved in the use and protection of groundwater resources. Sustainable groundwater withdrawal and management, and the identification of trends in groundwater contamination require a careful hydrochemical baseline characterization. This characterization is fundamental to investigate the presence and evolutionary trend of contaminants. In fact, it allows recovering and understanding: the spatial-temporal trend of contamination; the relative age of the contamination episodes; the reasons for anomalous behavior of some compounds during migration to and in the groundwater; the associations with which some contaminants can be found; the different behaviors in phreatic and semi-confined and confined aquifers. To attain such a characterization for the Milan metropolitan area (about 2,500 km2, ca 4.000.000 inhabitants, Lombardy, Italy), we carried out three main activities. (1) Collection of complete and reliable datasets concerning the geological, hydrogeological and hydrochemical (over 60,000 chemical analysis since 2003 to 2013) characteristics of the area and of the involved aquifers. This activity was very demanding because the available data are provided by different authorities (Lombardy Region, Provinces, Lombardy Environmental Agency - ARPA Lombardia, public own companies in charge of water system managements) in raw format and with different database standard, which required a large effort of manual verification and harmonization. (2) Completion of a hydrochemical characterization of the metropolitan area aquifers by classical statistical and multivariate statistical analyses, in order to define a baseline both for some major physical chemical characteristics and for the most relevant contaminants. (3) Development of a three dimensional hydrogeological model for the metropolitan area starting from the above listed datasets and existing models. This model will allow for the groundwater flow and transport modeling at the large scale and could be successively linked to some more site-specific transport multi-reactive models focused on the modeling of some specific contaminants.

  18. Quantitative analysis of fault and fracture systems and their impact on groundwater flow in Irish bedrock aquifers

    NASA Astrophysics Data System (ADS)

    Moore, John Paul; Walsh, John; Manzocchi, Tom; Hunter-Williams, Natalia; Ofterdinger, Ulrich; Ball, David

    2015-04-01

    Faults and fractures are the most important store and pathway for groundwater in Ireland's bedrock aquifers either directly as conductive flow structures or indirectly as the locus for the development of dolomitised limestone and karst. Through quantitative analysis in a range of Irish bedrock types, we have developed generic conceptual models of depth dependency, lithological control and scaling systematics for the different fault and fracture systems, linked to observed groundwater behaviour. Quantitative characterisation of the main post-Devonian fracture systems in over 70 outcrop, quarry, mine and cave locations shows that their geometry and nature varies with lithological sequence and with spatial controls, such as depth and regional variations in deformation style and intensity. The nature of fracturing and faulting directly controls aperture distribution, size and geometry, which in turn influences karst conduit geometry in limestones. Determining these attributes is, therefore, key for groundwater flow parameter estimation. We briefly describe how the most transmissive structures (NNE-NNW Variscan veins and Tertiary strike-slip faults), and the most common structures (joints) can be linked to critical groundwater parameters, such as transmissivity, storage coefficient and connectivity, at both regional and local scales. We show that for some of these fracture systems, structural parameters critical to groundwater flow (including orientation, spacing and aperture) can be used to compute ranges of hydrogeological parameters (fracture porosity and permeability), which in combination with hydraulic data (groundwater levels, volumetric flow and recharge) can be used to provide constraints on permeability anisotropy and heterogeneity at different scales.

  19. Striking effect of time variation in the estimation of groundwater age in the Wairarapa valley

    NASA Astrophysics Data System (ADS)

    Petrus, Karine; Toews, Michael; Daughney, Christopher; Cornaton, Fabien

    2014-05-01

    The Wairarapa Valley exhibits complex interactions between its rivers and shallow aquifers. With agriculture being an essential part of the region the risk of contamination and depletion of groundwater exists. In order to assist with water resource management in the region, we can do predictions with the help of numerical models. Among these predictions, the evaluation of groundwater age is critical for decision making. This project builds on work done by Greater Wellington Regional Council and will focus on the Wairarapa Valley. The aim of this study is to evaluate the age of the groundwater in the Wairarapa region. Investigations have already been done thanks to hydrochemistry. However radiometric age can be misleading in the sense that it does not consider the mixing process in the motion of groundwater particules. Therefore another approach can be considered .This latter is physic based by considering the age as a property that we transport through two main processes: advection at a macroscopic scale and diffusion at a microscopic scale. The determination of the distribution age by this approach has already been done for the Lake Rotorua but in the steady state case (cf Daughney). The unique contribution of the present study is to estimate the changes in groundwater age distribution through time within the region. Indeed transient simulations are needed to explicitly account for seasonally variable rainfall and pumping wells. This affects the simulated flow solution and then the simulated age solution. In order to solve numerically the transport of age distribution we have chosen to use the Time Marching Laplace Transform Galerkin technique which has been developed in a research code by Fabien Cornaton. The obtained results depict that temporal variations in groundwater age are present and have important implication for resource management

  20. Simulation of groundwater flow and the interaction of groundwater and surface water in the Willamette Basin and Central Willamette subbasin, Oregon

    USGS Publications Warehouse

    Herrera, Nora B.; Burns, Erick R.; Conlon, Terrence D.

    2014-01-01

    Full appropriation of tributary streamflow during summer, a growing population, and agricultural needs are increasing the demand for groundwater in the Willamette Basin. Greater groundwater use could diminish streamflow and create seasonal and long-term declines in groundwater levels. The U.S. Geological Survey (USGS) and the Oregon Water Resources Department (OWRD) cooperated in a study to develop a conceptual and quantitative understanding of the groundwater-flow system of the Willamette Basin with an emphasis on the Central Willamette subbasin. This final report from the cooperative study describes numerical models of the regional and local groundwater-flow systems and evaluates the effects of pumping on groundwater and surface?water resources. The models described in this report can be used to evaluate spatial and temporal effects of pumping on groundwater, base flow, and stream capture. The regional model covers about 6,700 square miles of the 12,000-square mile Willamette and Sandy River drainage basins in northwestern Oregon—referred to as the Willamette Basin in this report. The Willamette Basin is a topographic and structural trough that lies between the Coast Range and the Cascade Range and is divided into five sedimentary subbasins underlain and separated by basalts of the Columbia River Basalt Group (Columbia River basalt) that crop out as local uplands. From north to south, these five subbasins are the Portland subbasin, the Tualatin subbasin, the Central Willamette subbasin, the Stayton subbasin, and the Southern Willamette subbasin. Recharge in the Willamette Basin is primarily from precipitation in the uplands of the Cascade Range, Coast Range, and western Cascades areas. Groundwater moves downward and laterally through sedimentary or basalt units until it discharges locally to wells, evapotranspiration, or streams. Mean annual groundwater withdrawal for water years 1995 and 1996 was about 400 cubic feet per second; irrigation withdrawals accounted for about 80 percent of that total. The upper 180 feet of productive aquifers in the Central Willamette and Southern Willamette subbasins produced about 70 percent of the total pumped volume. In this study, the USGS constructed a three-dimensional numerical finite-difference groundwater-flow model of the Willamette Basin representing the six hydrogeologic units, defined in previous investigations, as six model layers. From youngest to oldest, and [generally] uppermost to lowermost they are the: upper sedimentary unit, Willamette silt unit, middle sedimentary unit, lower sedimentary unit, Columbia River basalt unit, and basement confining unit. The high Cascade unit is not included in the groundwater-flow model because it is not present within the model boundaries. Geographic boundaries are simulated as no-flow (no water flowing in or out of the model), except where the Columbia River is simulated as a constant hydraulic head boundary. Streams are designated as head-dependent-flux boundaries, in which the flux depends on the elevation of the stream surface. Groundwater recharge from precipitation was estimated using the Precipitation-Runoff Modeling System (PRMS), a watershed model that accounts for evapotranspiration from the unsaturated zone. Evapotranspiration from the saturated zone was not considered an important component of groundwater discharge. Well pumping was simulated as specified flux and included public supply, irrigation, and industrial pumping. Hydraulic conductivity values were estimated from previous studies through aquifer slug and permeameter tests, specific capacity data, core analysis, and modeling. Upper, middle and lower sedimentary unit horizontal hydraulic conductivity values were differentiated between the Portland subbasin and the Tualatin, Central Willamette, and Southern Willamette subbasins based on preliminary model results.

  1. Lake hydrogeophysics; Estimating areas of potential groundwater seepage using reflection seismic, ground penetrating radar and multiple electrode profiling

    NASA Astrophysics Data System (ADS)

    Looms, M. C.; Boldreel, L. O.; Kidmose, J.; Engesgaard, P.; Rasmussen, R.; Nilsson, B.

    2008-12-01

    Lake Hampen, a groundwater seepage lake located on sandy deposits, is one of the cleanest lakes in Denmark. The lake is mainly surrounded by areas with forestry. A small agricultural area has been shown to potentially discharge high concentrations of nitrate to the lake. In order to minimize future nutrient loading to Lake Hampen it is essential that the water balance components and the areas of groundwater in- and outflow are estimated correctly. Groundwater/lake water interaction estimated using seepage meters, hydraulic gradients, and stable isotope measurements give reliable point estimates of groundwater in- and out flow rates. These rates are affected by the heterogeneity in the geological sediments beneath the lake and the lake bed properties. In order to construct a hydrological model covering the entire lake, having an approx. surface area of 760.000 m2, an improved spatial coverage of the geology beneath the lake is necessary. In this study three geophysical techniques; reflection seismic, ground penetrating radar and multiple electrode profiling, are used to map the sediment types and thicknesses at the lake bottom. Areas with thick layers of gyttja or peat are expected to reduce groundwater seepage, while a sandy lake bottom will enable high rates of in- and outflow. The geophysical measurements thereby help identifying areas of potential groundwater seepage that later can be verified using more traditional point measurements.

  2. Noble gas loss may indicate groundwater flow across flow barriers in southern Nevada

    USGS Publications Warehouse

    Thomas, J.M.; Bryant, Hudson G.; Stute, M.; Clark, J.F.

    2003-01-01

    Average calculated noble gas temperatures increase from 10 to 22??C in groundwater from recharge to discharge areas in carbonate-rock aquifers of southern Nevada. Loss of noble gases from groundwater in these regional flow systems at flow barriers is the likely process that produces an increase in recharge noble gas temperatures. Emplacement of low permeability rock into high permeability aquifer rock and the presence of low permeability shear zones reduce aquifer thickness from thousands to tens of meters. At these flow barriers, which are more than 1,000 m lower than the average recharge altitude, noble gases exsolve from the groundwater by inclusion in gas bubbles formed near the barriers because of greatly reduced hydrostatic pressure. However, re-equilibration of noble gases in the groundwater with atmospheric air at the low altitude spring discharge area, at the terminus of the regional flow system, cannot be ruled out. Molecular diffusion is not an important process for removing noble gases from groundwater in the carbonate-rock aquifers because concentration gradients are small.

  3. Nested-scale discharge and groundwater level monitoring to improve predictions of flow route discharges and nitrate loads

    NASA Astrophysics Data System (ADS)

    van der Velde, Y.; Rozemeijer, J. C.; de Rooij, G. H.; van Geer, F. C.; Torfs, P. J. J. F.; de Louw, P. G. B.

    2010-10-01

    Identifying effective measures to reduce nutrient loads of headwaters in lowland catchments requires a thorough understanding of flow routes of water and nutrients. In this paper we assess the value of nested-scale discharge and groundwater level measurements for predictions of catchment-scale discharge and nitrate loads. In order to relate field-site measurements to the catchment-scale an upscaling approach is introduced that assumes that scale differences in flow route fluxes originate from differences in the relationship between groundwater storage and the spatial structure of the groundwater table. This relationship is characterized by the Groundwater Depth Distribution (GDD) curve that relates spatial variation in groundwater depths to the average groundwater depth. The GDD-curve was measured for a single field site (0.009 km2) and simple process descriptions were applied to relate the groundwater levels to flow route discharges. This parsimonious model could accurately describe observed storage, tube drain discharge, overland flow and groundwater flow simultaneously with Nash-Sutcliff coefficients exceeding 0.8. A probabilistic Monte Carlo approach was applied to upscale field-site measurements to catchment scales by inferring scale-specific GDD-curves from hydrographs of two nested catchments (0.4 and 6.5 km2). The estimated contribution of tube drain effluent (a dominant source for nitrates) decreased with increasing scale from 76-79% at the field-site to 34-61% and 25-50% for both catchment scales. These results were validated by demonstrating that a model conditioned on nested-scale measurements simulates better nitrate loads and better predictions of extreme discharges during validation periods compared to a model that was conditioned on catchment discharge only.

  4. Unsaturated-zone fast-path flow calculations for Yucca Mountain groundwater travel time analyses (GWTT-94)

    SciTech Connect

    Arnold, B.W.; Altman, S.J.; Robey, T.H.

    1995-08-01

    Evaluation of groundwater travel time (GWTT) is required as part of the investigation of the suitability of Yucca Mountain as a potential high-level nuclear-waste repository site. The Nuclear Regulatory Commission`s GWTT regulation is considered to be a measure of the intrinsic ability of the site to contain radionuclide releases from the repository. The work reported here is the first step in a program to provide an estimate of GWTT at the Yucca Mountain site in support of the DOE`s Technical Site Suitability and as a component of a license application. Preliminary estimation of the GWTT distribution in the unsaturated zone was accomplished using a numerical model of the physical processes of groundwater flow in the fractured, porous medium of the bedrock. Based on prior investigations of groundwater flow at the site, fractures are thought to provide the fastest paths for groundwater flow; conditions that lead to flow in fractures were investigated and simulated. Uncertainty in the geologic interpretation of Yucca Mountain was incorporated through the use of geostatistical simulations, while variability of hydrogeologic parameters within each unit was accounted for by the random sampling of parameter probability density functions. The composite-porosity formulation of groundwater flow was employed to simulate flow in both the matrix and fracture domains. In this conceptualization, the occurrence of locally saturated conditions within the unsaturated zone is responsible for the initiation of fast-path flow through fractures. The results of the GWTT-94 study show that heterogeneity in the hydraulic properties of the model domain is an important factor in simulating local regions of high groundwater saturation. Capillary-pressure conditions at the surface boundary influence the extent of the local saturation simulated.

  5. Numerical Modeling of Regional Groundwater Flow in a Structurally Complex Intermountain Basin: South Park, Colorado

    NASA Astrophysics Data System (ADS)

    Ball, L. B.; Caine, J. S.; Ge, S.

    2012-12-01

    A steady-state, 3-D groundwater flow model of the South Park basin was developed to explore the influence of realistically complex topography and permeability structure on the patterns of basin-wide groundwater flow and to evaluate the sensitivity of the groundwater flow system to increased variability in recharge distribution and the influence of hydrogeologically distinct fault zones. South Park is a large, semi-arid intermountain basin (3300 km2) flanked by crystalline rocks and floored with faulted and folded sedimentary rocks and volcanic deposits. Model results suggest that, while the majority (>80%) of water entering the groundwater flow system is discharged through seepage faces in steep terrain or routed to mountain streams, internal exchanges of groundwater and stream flow between the mountain and valley landscapes are an important part of the dynamics of groundwater flow in the basin. The majority of topographically driven groundwater flow is focused in the upper 300 m of the model domain and would be considered local to intermediate in "Tothian" scales. Less than 1% of groundwater flow passes below 1 km in depth, and large-scale regional circulation is a limited component of the groundwater flow system. Increasingly heterogeneous recharge distributions most heavily impacted the groundwater flow system at the local scale, while basin-wide regional flow remained relatively insensitive to the increasing variability in recharge distribution. The introduction of end-member conduit and barrier types of fault zones influenced hydraulic heads and gradients within 5-10 km of the fault location where groundwater flow directions are perpendicular to the orientation of the fault. Where groundwater flow directions are oblique or subparallel to the fault, the introduction of distinct fault zones had a negligible impact on hydraulic heads or gradients.

  6. Processing, Analysis, and General Evaluation of Well-Driller Logs for Estimating Hydrogeologic Parameters of the Glacial Sediments in a Ground-Water Flow Model of the Lake Michigan Basin

    USGS Publications Warehouse

    Arihood, Leslie D.

    2009-01-01

    In 2005, the U.S. Geological Survey began a pilot study for the National Assessment of Water Availability and Use Program to assess the availability of water and water use in the Great Lakes Basin. Part of the study involves constructing a ground-water flow model for the Lake Michigan part of the Basin. Most ground-water flow occurs in the glacial sediments above the bedrock formations; therefore, adequate representation by the model of the horizontal and vertical hydraulic conductivity of the glacial sediments is important to the accuracy of model simulations. This work processed and analyzed well records to provide the hydrogeologic parameters of horizontal and vertical hydraulic conductivity and ground-water levels for the model layers used to simulated ground-water flow in the glacial sediments. The methods used to convert (1) lithology descriptions into assumed values of horizontal and vertical hydraulic conductivity for entire model layers, (2) aquifer-test data into point values of horizontal hydraulic conductivity, and (3) static water levels into water-level calibration data are presented. A large data set of about 458,000 well driller well logs for monitoring, observation, and water wells was available from three statewide electronic data bases to characterize hydrogeologic parameters. More than 1.8 million records of lithology from the well logs were used to create a lithologic-based representation of horizontal and vertical hydraulic conductivity of the glacial sediments. Specific-capacity data from about 292,000 well logs were converted into horizontal hydraulic conductivity values to determine specific values of horizontal hydraulic conductivity and its aerial variation. About 396,000 well logs contained data on ground-water levels that were assembled into a water-level calibration data set. A lithology-based distribution of hydraulic conductivity was created by use of a computer program to convert well-log lithology descriptions into aquifer or nonaquifer categories and to calculate equivalent horizontal and vertical hydraulic conductivities (K and KZ, respectively) for each of the glacial layers of the model. The K was based on an assumed value of 100 ft/d (feet per day) for aquifer materials and 1 ft/d for nonaquifer materials, whereas the equivalent KZ was based on an assumed value of 10 ft/d for aquifer materials and 0.001 ft/d for nonaquifer materials. These values were assumed for convenience to determine a relative contrast between aquifer and nonaquifer materials. The point values of K and KZ from wells that penetrate at least 50 percent of a model layer were interpolated into a grid of values. The K distribution was based on an inverse distance weighting equation that used an exponent of 2. The KZ distribution used inverse distance weighting with an exponent of 4 to represent the abrupt change in KZ that commonly occurs between aquifer and nonaquifer materials. The values of equivalent hydraulic conductivity for aquifer sediments needed to be adjusted to actual values in the study area for the ground-water flow modeling. The specific-capacity data (discharge, drawdown, and time data) from the well logs were input to a modified version of the Theis equation to calculate specific capacity based horizontal hydraulic conductivity values (KSC). The KSC values were used as a guide for adjusting the assumed value of 100 ft/d for aquifer deposits to actual values used in the model. Water levels from well logs were processed to improve reliability of water levels for comparison to simulated water levels in a model layer during model calibration. Water levels were interpolated by kriging to determine a composite water-level surface. The difference between the kriged surface and individual water levels was used to identify outlier water levels. Examination of the well-log lithology data in map form revealed that the data were not only useful for model input, but also were useful for understanding th

  7. Evaluation of ground-water flow by particle tracking, Wright-Patterson Air Force Base, Ohio

    USGS Publications Warehouse

    Cunningham, W.L.; Sheets, R.A.; Schalk, C.W.

    1994-01-01

    The U.S. Geological Survey (USGS) and Wright-Patterson Air Force Base (WPAFB) began a Basewide Monitoring Program (BMP) in 1992. The purpose of the BMP was to establish a long-term ground-water and surface- water sampling network in order to (1) characterize current ground-water and surface-water quality; (2) describe water-quality changes as water enters, flows across, and exits Base boundaries; (3) conduct statistical analyses of water quality; and (4) estimate the effect of WPAFB on regional water quality. As part of the BMP, the USGS conducted ground-water particle-tracking analyses based on a ground-water-flow model produced during a previous USGS study. This report briefly describes the previous USGS study, the inherent assumptions of particle-tracking analyses, and information on the regional ground-water-flow field as inferred from particle pathlines. Pathlines for particles placed at the Base boundary and particles placed within identified Installation Restoration Program sites are described.

  8. Inferring shallow groundwater flow in saprolite and fractured rock using environmental tracers

    USGS Publications Warehouse

    Cook, P.G.; Solomon, D.K.; Sanford, W.E.; Busenberg, E.; Plummer, L.N.; Poreda, R.J.

    1996-01-01

    The Ridge and Valley Province of eastern Tennessee is characterized by (1) substantial topographic relief, (2) folded and highly fractured rocks of various lithologies that have low primary permeability and porosity, and (3) a shallow residuum of medium permeability and high total porosity. Conceptual models of shallow groundwater flow and solute transport in this system have been developed but are difficult to evaluate using physical characterization or short-term tracer methods due to extreme spatial variability in hydraulic properties. In this paper we describe how chlorofluorocarbon 12, 3H, and 3He were used to infer groundwater flow and solute transport in saprolite and fractured rock near Oak Ridge, Tennessee. In the shallow residuum, fracture spacings are <0.05 m, suggesting that concentrations of these tracers in fractures and in the matrix have time to diffusionally equilibrate. The relatively smooth nature of tracer concentrations with depth in the residuum is consistent with this model and quantitatively suggests recharge fluxes of 0.2 to 0.4 m yr-. In contrast, groundwater flow within the unweathered rock appears to be controlled by fractures with spacings of the order of 2 to 5 m, and diffusional equilibration of fractures and matrix has not occurred. For this reason, vertical fluid fluxes in the unweathered rock cannot be estimated from the tracer data.

  9. Estimation of yield capacity of fractured rock aquifer for multi-well groundwater heat pump system

    NASA Astrophysics Data System (ADS)

    Bak, Hyeongmin; Yeo, In Wook

    2015-04-01

    Geothermal heat pump system is classified as closed loop and open loop. Closed loop uses a refrigerant as a heat source. For the reason, when using it for a long time, there is a possibility that the refrigerant pipe is corroded. Accordingly, soil and groundwater can be contaminated. Whereas the open loop system uses a eco-friendly groundwater as a heat source. Thermal circulation of standing column well (SCW) occurs in one well. In contrast, thermal circulation of multi-well groundwater heat pump system (MGHP) occurs through fractured rock aquifer between extraction and injection wells. Therefore, temperature efficiency of MGHP appears to be better than that of SCW. However, the MGHP has problems such as the overflowing in the injection well and the clogging, which restricts the wide use of MGHP. This study aims at how to to array the extraction and injection wells for stable circulating of groundwater and at evaluating the sustainable yield capacity of groundwater circulation between the two wells. The study site is located in Chuncheon, Republic of Korea. Pumping tests were conducted to estimate transmissivity of the two wells (W3, W4). In addition, the step-circulation tests were conducted to estimate the sustainable yield capacity. Transmissivity of W3 and W4 was estimated to be 5.81 x 10^-5 m^2/s and 2.57 x 10^-5 m^2/s, respectively. Preliminary groundwater circulation tests were conducted to figure out the array of the extraction and injection wells. Circulation tests were performed for two cases: first, extraction well was set at the well with higher transmissivity and injection well set at the well with lower transmissivity, and the opposite array was set for the second case. In the first case, when flow rate was set at 70.47 m^3/day, the water level of W3 fell 0.61m and that of W4 rose 1.89m. In the second case, when flow rate was set at 67.70 m^3/day, the water level of W4 fell 2.17m and that of W3 rose 0.5m. Preliminary groundwater circulation tests indicated that the well with relatively higher transmissivity is favorable to the extraction and that with lower transmissivity is favorable to the injection. The step-circulation test was performed in all four step increments between the extraction well (W4) and the injection well (W3), which helps evaluate the sustainable yield capacity of groundwater circulation between the two wells. After the four increments, the yield capacity of sustainable groundwater circulation was estimated to be 270 m^3/day without the overflowing at injection well and sustainable drawdown at the extraction well.

  10. Estimates of riparian evapotranspiration using diurnal monitoring of groundwater regime in desert environments

    NASA Astrophysics Data System (ADS)

    Wang, P.; Pozdniakov, S. P.; Grinevsky, S.; Yu, J.

    2013-12-01

    Shallow groundwater is mainly discharged by phreatophytes in many riparian ecosystems of arid and semiarid environment, while estimation of groundwater evapotranspiration in these regions still remains a challenge for regional water resources assessment. In this study, a simple relationship between the average standard deviation of diurnal groundwater level fluctuations and the daily evapotranspiration over relatively short periods (days or weeks) was developed for estimating groundwater consumption by phreatophytes in arid/semi-arid areas. Our approach allows estimating groundwater evapotranspiration using stable statistical characteristics of diurnal groundwater fluctuation, and it is useful for analyzing large amounts of data obtained from digital groundwater level monitoring sensors. The developed methodology was applied to two phreatophyte-dominated riparian areas (Populus euphratica and Tamarix ramosissima) in a typical Gobi desert region of northwest China to demonstrate the usefulness of the technique.

  11. Estimating pumping time and ground-water withdrawals using energy- consumption data

    USGS Publications Warehouse

    Hurr, R.T.; Litke, D.W.

    1989-01-01

    Evaluation of the hydrology of an aquifer requires knowledge about the volume of groundwater in storage and also about the volume of groundwater withdrawals. Totalizer flow meters may be installed at pumping plants to measure withdrawals; however, it generally is impractical to equip all pumping plants in an area with meters. A viable alternative is the use of rate-time methods. Rate-time methods may be used at individual pumping plants to decrease the data collection necessary for determining withdrawals. At sites where pumping-time measurement devices are not installed, pumping time may be determined on the basis of energy consumption and power demand. At pumping plants where energy consumption is metered, data acquired by reading of meters is used to estimate pumping time. Care needs to be taken to read these meters correctly. At pumping plants powered by electricity, the calculations need to be modified if transformers are present. At pumping plants powered by natural gas, the effects of the pressure-correction factor need to be included in the calculations. At pumping plants powered by gasoline, diesel oil, or liquid petroleum gas, the geometry of storage tanks needs to be analyzed as part of the calculations. The relation between power demand and pumping rate at a pumping plant can be described through the use of the power-consumption coefficient. Where equipment and hydrologic conditions are stable, this coefficient can be applied to total energy consumption at a site to estimate total groundwater withdrawals. Random sampling of power consumption coefficients can be used to estimate area-wide groundwater withdrawal. (USGS)

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

    SciTech Connect

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

    1999-09-30

    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. 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. 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. Mean annual ET from the Ash Meadows area is estimated at 21,000 acre-feet. The estimates given for mean annual ground-water discharge range from 18,000 to 21,000 acre-feet. The range presented is only slightly higher than previous estimates of ground-water discharge from the Ash Meadows area based primarily on springflow measurements.

  13. Groundwater flow with energy transport and waterice phase change: Numerical simulations, benchmarks, and application to

    E-print Network

    McKenzie, Jeffrey M.

    peatlands, subsurface ice formation is an important process that can control heat transport, groundwater hydrogeological, and biological processes, including the thermal regime, groundwater flow patterns, groundwater recharge, and subterrain biological activity [1­3]. Further, given the sensitivity of arctic regions to cli

  14. Groundwater, springs, and stream flow generation in an alpine meadow of a tropical glacierized catchment

    NASA Astrophysics Data System (ADS)

    Gordon, R.; Lautz, L. K.; McKenzie, J. M.; Mark, B. G.; Chavez, D.

    2013-12-01

    Melting tropical glaciers supply approximately half of dry season stream discharge in glacierized valleys of the Cordillera Blanca, Peru. The remainder of streamflow originates as groundwater stored in alpine meadows, moraines and talus slopes. A better understanding of the dynamics of alpine groundwater, including sources and contributions to streamflow, is important for making accurate estimates of glacial inputs to the hydrologic budget, and for our ability to make predictions about future water resources as glaciers retreat. Our field study, conducted during the dry season in the Llanganuco valley, focused on a 0.5-km2 alpine meadow complex at 4400 m elevation, which includes talus slopes, terminal moraines, and a debris fan. Two glacial lakes and springs throughout the complex feed a network of stream channels that flow across the meadow (~2 km total length). We combined tracer measurements of stream and spring discharge and groundwater-surface water exchange with synoptic sampling of water isotopic and geochemical composition, in order to characterize and quantify contributions to streamflow from different geomorphic features. Surface water inputs to the stream channels totaled 58 l/s, while the stream gained an additional 57 l/s from groundwater inputs. Water chemistry is primarily controlled by flowpath type (surface/subsurface) and length, as well as bedrock lithology, while stable water isotopic composition appears to be controlled by water source (glacial lake, meadow or deep groundwater). Stream water chemistry is most similar to meadow groundwater springs, but isotopic composition suggests that the majority of stream water, which issues from springs at the meadow/fan interface, is from the same glacial source as the up-gradient lake. Groundwater sampled from piezometers in confined meadow aquifers is unique in both chemistry and isotopic composition, but does not contribute a large percentage of stream water exiting this small meadow, as quantified by discharge measurements and isotopic mixing. However, we expect that as streams flow down through extensive meadows and wetlands in many Cordillera Blanca valleys, meadow groundwater is a more significant contributor to streamflow. Results from this small, high meadow in Llanganuco will be compared to a larger and lower-elevation meadow system in the Quilcayhuanca valley.

  15. Sources and flow of north Canterbury plains groundwater, New Zealand

    NASA Astrophysics Data System (ADS)

    Taylor, C. B.; Wilson, D. D.; Brown, L. J.; Stewart, M. K.; Burden, R. J.; Brailsford, G. W.

    1989-04-01

    Geological, hydrological, isotope (tritium and 18O) and chemical (mainly nitrate and chloride concentrations) evidence is interpreted to give a mutually consistent picture of the recharge sources and flow patterns of the important groundwater resource in the deep glacial and interglacial deposits of the sector of the Canterbury Plains between the Selwyn River and Ashley River. Particular attention is paid to the confined gravel aquifers which presently provide about 300,000 m 3 daily of mainly very high-quality water for the needs of Christchurch city. The study period for tritium measurements extends over 27 years, encompassing the peak and decline of thermonuclear tritium fallout in this region. Major rivers emerging from the hill and mountain catchments to the west of the Plains are depleted in 18O relative to average low-level precipitation. Most of the groundwater is river-recharged, but some areas of significant local precipitation recharge contribution are clearly identified by 18O and chemical concentrations. The pressure distribution, tritium and chemical data reveal that the artesian ground-water underlying Christchurch ascends from deeper aquifers into the shallowest aquifer via gaps in the confining layers; much of this flow is induced by withdrawal, and the data reveal nothing about possible offshore discharge through the seaward extension of the shallowest aquifer, which is known to outcrop 40 km beyond the coast. The Christchurch aquifers are recharged by infiltration from Waimakariri River in its central Plains reaches, and the resulting flow regime is east- and southeast-directed; satisfactory water quality of the deeper Christchurch aquifers appears to be guaranteed for the future provided the river can be maintained in its present condition. Shallow groundwater, and water recharged to depth by other rivers, irrigation and local precipitation on the unconfined western areas of the Plains, are more susceptible to agricultural and other pollutants; none of this water is encountered in the deeper aquifers under Christchurch, but only in shallow aquifers and surface discharges, or else flowing to the southeast, well away from the city area.

  16. Hydrochemical and 14C constraints on groundwater recharge and interbasin flow in an arid watershed: Tule Desert, Nevada

    NASA Astrophysics Data System (ADS)

    Hagedorn, Benjamin

    2015-04-01

    Geochemical data deduced from groundwater and vein calcite were used to quantify groundwater recharge and interbasin flow rates in the Tule Desert (southeastern Nevada). 14C age gradients below the water table suggest recharge rates of 1-2 mm/yr which correspond to a sustainable yield of 5 × 10-4 km3/yr to 1 × 10-3 km3/yr. Uncertainties in the applied effective porosity value and increasing horizontal interbasin flow components at greater depths may bias these estimates low compared to those previously reported using the water budget method. The deviation of the groundwater ?18O time-series pattern for the Pleistocene-Holocene transition from that of the Devils Hole vein calcite (which is considered a proxy for local climate change) allows interbasin flow rates of northerly derived groundwater to be estimated. The constrained rates (75.0-120 m/yr) are slightly higher than those previously calculated using Darcy's Law, but translate into hydraulic conductivity values strikingly similar to those obtained from pump tests. Data further indicate that production wells located closer to the western mountainous margin will be producing mainly from locally derived mountain-system recharge whereas wells located closer to the eastern margin are more influenced by older, regionally derived carbonate groundwater.

  17. Modelling of the groundwater flow in Baltic Artesian Basin

    NASA Astrophysics Data System (ADS)

    Virbulis, J.; Sennikovs, J.; Bethers, U.

    2012-04-01

    Baltic Artesian Basin (BAB) is a multi-layered complex hydrogeological system underlying about 480'000 km2 in the territory of Latvia, Lithuania, Estonia, Poland, Russia, Belarus and the Baltic Sea. The model of the geological structure contains 42 layers including aquifers and aquitards from Cambrian up to the Quaternary deposits. The finite element method was employed for the calculation of the steady state three-dimensional groundwater flow with free surface. The horizontal and vertical hydraulic conductivities of geological materials were assumed constant in each of the layers. The Precambrian basement forms the impermeable bottom of the model. The zero water exchange is assumed through the side boundaries of BAB. Simple hydrological model is applied on the surface. The level of the lakes, rivers and the sea is fixed as constant hydraulic head in corresponding mesh points. The infiltration is set as a flux boundary condition elsewhere. Instead of extensive coupling with hydrology model, a constant mean value of 70 mm/year was assumed as an infiltration flux for the whole BAB area and this value was adjusted during the automatic calibration process. Averaged long-term water extraction was applied at the water supply wells with large debits. In total 49 wells in Lithuania (total abstraction 45000 m3/day), 161 in Latvia (184000 m3/day) and 172 in Estonia (24000 m3/day) are considered. The model was calibrated on the statistically weighted (using both spatial and temporal weighting function) borehole water level measurements applying automatic parameter optimization method L-BFGS-B for hydraulic conductivities of each layer. The steady-stade calculations were performed for the situations corresponding to undisturbed situation (1950-ies), intensive groundwater use (1980-ies) and present state situation (after 2000). The distribution of piezometric heads and principal flows inside BAB was analyzed based on the model results. The results demonstrate that generally the flow is directed from southeast to northwest, but the more shallow aquifers show strong influence by local topography. There is an intensive transient flow in Cm aquifer system and this flow is separated from upper layers by thick aquitard O-S. About 25% of the aquifers volume is under free flowing artesian conditions. Acknowledgement The present work has been funded by the European Social Fund project "Establishment of interdisciplinary scientist group and modelling system for groundwater research" (Project No. 2009/0212/1DP/1.1.1.2.0/09/APIA/VIAA/060)

  18. A preliminary analysis of the hydrogeological conditions and groundwater flow in some parts of a crystalline aquifer system: Afigya Sekyere South District, Ghana

    NASA Astrophysics Data System (ADS)

    Yidana, Sandow Mark; Essel, Stephen Kwaku; Addai, Millicent Obeng; Fynn, Obed Fiifi

    2015-04-01

    A steady state groundwater flow model was calibrated to simulate the complex groundwater flow pattern in some crystalline aquifer systems in north-central Ghana. The objective was to develop the general geometry of the groundwater system and also estimate spatial variations in the hydraulic conductivity field as part of efforts to thoroughly investigate the general hydrogeology and groundwater conditions of aquifers in the area. The calibrated model was used in a limited fashion to simulate some scenarios of groundwater development in the terrain. The results suggest the dominance of local groundwater flow systems resulting from local variabilities in the hydraulic conductivity field and the topography. Estimated horizontal hydraulic conductivities range between 1.04 m/d and 15.25 m/d, although most of the areas consist of hydraulic conductivities in the range of 1.04 m/d and 5.5 m/d. Groundwater flow is apparently controlled by discrete entities with limited spatial interconnectivities. Recharge rates estimated at calibration range between 4.3% and 13% of the annual rainfall in the terrain. The analysis suggests that under the current recharge rates, the system can sustain increasing groundwater abstraction rates by up to 50% with minimal drawdown in the hydraulic head for the entire terrain. However, with decreasing groundwater recharge as would be expected in the wake of climate change/variability in the area, increased groundwater abstraction by up to 50% can lead to drastic drawdowns by more than 25% if recharge reduces by up to 50% of the current levels. This study strongly recommend the protection of some of the local groundwater recharge areas identified in this study and the promotion of local recharge through the development of dugouts and other conduits to encourage recharge.

  19. Groundwater.

    ERIC Educational Resources Information Center

    Braids, Olin C.; Gillies, Nola P.

    1978-01-01

    Presents a literature review of groundwater quality covering publications of 1977. This review includes: (1) sources of groundwater contamination; and (2) management of groundwater. A list of 59 references is also presented. (HM)

  20. Description and Evaluation of Numerical Groundwater Flow Models for the Edwards Aquifer, South-Central Texas

    USGS Publications Warehouse

    Lindgren, Richard J.; Taylor, Charles J.; Houston, Natalie A.

    2009-01-01

    A substantial number of public water system wells in south-central Texas withdraw groundwater from the karstic, highly productive Edwards aquifer. However, the use of numerical groundwater flow models to aid in the delineation of contributing areas for public water system wells in the Edwards aquifer is problematic because of the complex hydrogeologic framework and the presence of conduit-dominated flow paths in the aquifer. The U.S. Geological Survey, in cooperation with the Texas Commission on Environmental Quality, evaluated six published numerical groundwater flow models (all deterministic) that have been developed for the Edwards aquifer San Antonio segment or Barton Springs segment, or both. This report describes the models developed and evaluates each with respect to accessibility and ease of use, range of conditions simulated, accuracy of simulations, agreement with dye-tracer tests, and limitations of the models. These models are (1) GWSIM model of the San Antonio segment, a FORTRAN computer-model code that pre-dates the development of MODFLOW; (2) MODFLOW conduit-flow model of San Antonio and Barton Springs segments; (3) MODFLOW diffuse-flow model of San Antonio and Barton Springs segments; (4) MODFLOW Groundwater Availability Modeling [GAM] model of the Barton Springs segment; (5) MODFLOW recalibrated GAM model of the Barton Springs segment; and (6) MODFLOW-DCM (dual conductivity model) conduit model of the Barton Springs segment. The GWSIM model code is not commercially available, is limited in its application to the San Antonio segment of the Edwards aquifer, and lacks the ability of MODFLOW to easily incorporate newly developed processes and packages to better simulate hydrologic processes. MODFLOW is a widely used and tested code for numerical modeling of groundwater flow, is well documented, and is in the public domain. These attributes make MODFLOW a preferred code with regard to accessibility and ease of use. The MODFLOW conduit-flow model incorporates improvements over previous models by using (1) a user-friendly interface, (2) updated computer codes (MODFLOW-96 and MODFLOW-2000), (3) a finer grid resolution, (4) less-restrictive boundary conditions, (5) an improved discretization of hydraulic conductivity, (6) more accurate estimates of pumping stresses, (7) a long transient simulation period (54 years, 1947-2000), and (8) a refined representation of high-permeability zones or conduits. All of the models except the MODFLOW-DCM conduit model have limitations resulting from the use of Darcy's law to simulate groundwater flow in a karst aquifer system where non-Darcian, turbulent flow might actually dominate. The MODFLOW-DCM conduit model is an improvement in the ability to simulate karst-like flow conditions in conjunction with porous-media-type matrix flow. However, the MODFLOW-DCM conduit model has had limited application and testing and currently (2008) lacks commercially available pre- and post-processors. The MODFLOW conduit-flow and diffuse-flow Edwards aquifer models are limited by the lack of calibration for the northern part of the Barton Springs segment (Travis County) and their reliance on the use of the calibrated hydraulic conductivity and storativity values from the calibrated Barton Springs segment GAM model. The major limitation of the Barton Springs segment GAM and recalibrated GAM models is that they were calibrated to match measured water levels and springflows for a restrictive range of hydrologic conditions, with each model having different hydraulic conductivity and storativity values appropriate to the hydrologic conditions that were simulated. The need for two different sets of hydraulic conductivity and storativity values increases the uncertainty associated with the accuracy of either set of values, illustrates the non-uniqueness of the model solution, and probably most importantly demonstrates the limitations of using a one-layer model to represent the heterogeneous hydrostratigraph

  1. Uncertainty Analysis Framework - Hanford Site-Wide Groundwater Flow and Transport Model

    SciTech Connect

    Cole, Charles R.; Bergeron, Marcel P.; Murray, Christopher J.; Thorne, Paul D.; Wurstner, Signe K.; Rogers, Phillip M.

    2001-11-09

    Pacific Northwest National Laboratory (PNNL) embarked on a new initiative to strengthen the technical defensibility of the predictions being made with a site-wide groundwater flow and transport model at the U.S. Department of Energy Hanford Site in southeastern Washington State. In FY 2000, the focus of the initiative was on the characterization of major uncertainties in the current conceptual model that would affect model predictions. The long-term goals of the initiative are the development and implementation of an uncertainty estimation methodology in future assessments and analyses using the site-wide model. This report focuses on the development and implementation of an uncertainty analysis framework.

  2. Regional heat flow variations in the northern Michigan and Lake Superior region determined using the silica heat flow estimator

    USGS Publications Warehouse

    Vugrinovich, R.

    1987-01-01

    Conventional heat flow data are sparse for northern Michigan. The groundwater silica heat flow estimator expands the database sufficiently to allow regional variations in heat flow to be examined. Heat flow shows a pattern of alternating highs and lows trending ESE across the Upper Peninsula and Lake Superior. The informal names given to these features, their characteristic heat flow and inferred causes are listed: {A table is presented} The results suggest that, for the study area, regional variations in heat flow cannot be interpreted solely in terms of regional variations of the heat generation rate of basement rocks. ?? 1987.

  3. Controls on Groundwater Flow in an Alpine Talus-Moraine Complex

    NASA Astrophysics Data System (ADS)

    Muir, D. L.; Hayashi, M.; Bentley, L. R.

    2009-05-01

    Since alpine watersheds are the headwaters of rivers acting as major sources of water, there is growing concern over water shortages in areas dependent on mountain runoff. Talus and moraine complexes, as well as fractured bedrock, are a dominant hydrologic response unit within the Lake O'Hara Research Basin (LORB) in Yoho National Park, British Columbia. In this alpine environment, previous studies have shown that groundwater plays an important hydrological role. Although little is known about groundwater storage in these media, they are likely a significant groundwater reservoir and an important control on groundwater flow. The goals of this study are to develop a conceptual model of the talus and moraine complex and the fractured bedrock. The approximately 0.3km2 Babylon drainage basin within the LORB was chosen as the study site as it contains a talus and moraine complex that drains into one gaugeable stream. The conceptual model of this basin has been developed using geophysical, hydrological and hydrogeological methods. Three Ground Penetrating Radar (GPR) and Electrical Resistivity Imaging (ERI) surveys were used to characterize the subsurface structure and water distribution within the talus and moraine complex. The bedrock surface is clearly defined in the GPR profiles and its elevation agrees with that in the ERI inversions. Highly resistive talus material is observable in the ERI results, and areas of low resistivity are found within the bedrock. Hydraulic conductivity estimates of the geologic media, calculated using tracer slug injection and baseflow recession analysis methods, fall within the ranges from gravel to fractured rock. Isotopic hydrograph separations indicate that groundwater is a significant contributor to stream discharge. Linear reservoir models show basin response times of up to 16 hours. The geophysical and hydrological evidence points toward two flow systems operating in the Babylon basin, those of flow through the fractured bedrock and flow through the talus and moraine complex. Understanding the hydrologic characteristics of alpine talus and moraine complexes and fractured bedrock is of great importance to increasing our knowledge of alpine hydrology. The results from this study will enable the estimation of hydrologic parameters of these geologic media and provide valuable information for the predictive modelling of mountain streams.

  4. Groundwater flow, quality (2007-10), and mixing in the Wind Cave National Park area, South Dakota

    USGS Publications Warehouse

    Long, Andrew J.; Ohms, Marc J.; McKaskey, Jonathan D.R.G.

    2012-01-01

    A study of groundwater flow, quality, and mixing in relation to Wind Cave National Park in western South Dakota was conducted during 2007-11 by the U.S. Geological Survey in cooperation with the National Park Service because of water-quality concerns and to determine possible sources of groundwater contamination in the Wind Cave National Park area. A large area surrounding Wind Cave National Park was included in this study because to understand groundwater in the park, a general understanding of groundwater in the surrounding southern Black Hills is necessary. Three aquifers are of particular importance for this purpose: the Minnelusa, Madison, and Precambrian aquifers. Multivariate methods applied to hydrochemical data, consisting of principal component analysis (PCA), cluster analysis, and an end-member mixing model, were applied to characterize groundwater flow and mixing. This provided a way to assess characteristics important for groundwater quality, including the differentiation of hydrogeologic domains within the study area, sources of groundwater to these domains, and groundwater mixing within these domains. Groundwater and surface-water samples collected for this study were analyzed for common ions (calcium, magnesium, sodium, bicarbonate, chloride, silica, and sulfate), arsenic, stable isotopes of oxygen and hydrogen, specific conductance, and pH. These 12 variables were used in all multivariate methods. A total of 100 samples were collected from 60 sites from 2007 to 2010 and included stream sinks, cave drip, cave water bodies, springs, and wells. In previous approaches that combined PCA with end-member mixing, extreme-value samples identified by PCA typically were assumed to represent end members. In this study, end members were not assumed to have been sampled but rather were estimated and constrained by prior hydrologic knowledge. Also, the end-member mixing model was quantified in relation to hydrogeologic domains, which focuses model results on major hydrologic processes. Finally, conservative tracers were weighted preferentially in model calibration, which distributed model errors of optimized values, or residuals, more appropriately than would otherwise be the case The latter item also provides an estimate of the relative effect of geochemical evolution along flow paths in comparison to mixing. The end-member mixing model estimated that Wind Cave sites received 38 percent of their groundwater inflow from local surface recharge, 34 percent from the upgradient Precambrian aquifer, 26 percent from surface recharge to the west, and 2 percent from regional flow. Artesian springs primarily received water from end members assumed to represent regional groundwater flow. Groundwater samples were collected and analyzed for chlorofluorocarbons, dissolved gasses (argon, carbon dioxide, methane, nitrogen, and oxygen), and tritium at selected sites and used to estimate groundwater age. Apparent ages, or model ages, for the Madison aquifer in the study area indicate that groundwater closest to surface recharge areas is youngest, with increasing age in a downgradient direction toward deeper parts of the aquifer. Arsenic concentrations in samples collected for this study ranged from 0.28 to 37.1 micrograms per liter (?g/L) with a median value of 6.4 ?g/L, and 32 percent of these exceeded 10 ?g/L. The highest arsenic concentrations in and near the study area are approximately coincident with the outcrop of the Minnelusa Formation and likely originated from arsenic in shale layers in this formation. Sample concentrations of nitrate plus nitrite were less than 2 milligrams per liter for 92 percent of samples collected, which is not a concern for drinking-water quality. Water samples were collected in the park and analyzed for five trace metals (chromium, copper, lithium, vanadium, and zinc), the concentrations of which did not correlate with arsenic. Dye tracing indicated hydraulic connection between three water bodies in Wind Cave.

  5. Groundwater Flow Model for the R-Reactor Area Final Report

    SciTech Connect

    Harris, M.K.

    1997-11-01

    A detailed numerical groundwater flow model has been developed for the R-Area of the Savannah River Site in Aiken, South Carolina. The three-dimensional, finite-element groundwater modeling code Flow and Contaminant Transport (FACT) has been used for this study.

  6. Experimental study of turbulent unconfined groundwater flow in a single fracture

    E-print Network

    Zhan, Hongbin

    Experimental study of turbulent unconfined groundwater flow in a single fracture Jiazhong Qiana groundwater flow in a single fracture under the conditions of different surface roughness and apertures. We found that the gradient of the Reynolds number versus the average velocity in a single fracture

  7. ENVIRONMENTAL RESEARCH BRIEF : ANALYTIC ELEMENT MODELING OF GROUND-WATER FLOW AND HIGH PERFORMANCE COMPUTING

    EPA Science Inventory

    Several advances in the analytic element method have been made to enhance its performance and facilitate three-dimensional ground-water flow modeling in a regional aquifer setting. First, a new public domain modular code (ModAEM) has been developed for modeling ground-water flow ...

  8. Groundwater flow along and across structural folding: an example from the Judean Desert, Israel

    E-print Network

    Gvirtzman, Haim

    Groundwater flow along and across structural folding: an example from the Judean Desert, Israel of Jerusalem, Givat Ram Campus, Jerusalem 91904, Israel Received 25 March 2004; revised 14 January 2005 flow regime is exhibited in the thick carbonate aquifer beneath the Judean Desert, Israel. Groundwater

  9. Impact of horizontal groundwater flow and localized deforestation on the development of shallow

    E-print Network

    Beltrami, Hugo

    Impact of horizontal groundwater flow and localized deforestation on the development of shallow that develop in the shallow subsurface as a result of localized deforestation in combination with shallow horizontal groundwater flow. Model results show how a patch-wise pattern of deforestation at the surface

  10. Digital -domain embedding method for groundwater flow at the industrial waste landfill

    E-print Network

    Sakurai, Takafumi

    (22540113). #12;2 Drilling points and distribution of wastes in the landfill site The drilling surveyDigital - domain embedding method for groundwater flow at the industrial waste landfill on Teshima a numerical method to simulate the groundwater flow at the industrial waste landfill on Teshima Island

  11. DEFINITION OF GROUNDWATER FLOW IN THE WATER TABLE AQUIFER OF THE

    E-print Network

    District of Columbia, University of the

    ....................................................................................... 14 4.1. Surface Water Bodies...................................................................14 4#12;DEFINITION OF GROUNDWATER FLOW IN THE WATER TABLE AQUIFER OF THE SOUTHERN ANACOSTIA RIVER BASIN. 147 DEFINITION OF GROUNDWATER FLOW IN THE WATER TABLE AQUIFER OF THE SOUTHERN ANACOSTIA RIVER BASIN

  12. Numerical study of wave effects on groundwater flow and solute transport in a laboratory beach

    E-print Network

    Miller, Richard S.

    reserved. Keywords: Waves Groundwater flow Tracer MARUN numerical model Laboratory beach 1. Introduction In the last two decades, studies have revealed the ground- water system near the coastline is an importantNumerical study of wave effects on groundwater flow and solute transport in a laboratory beach

  13. Calibration of a large-scale groundwater flow model using GRACE data: a case study in the Qaidam Basin, China

    NASA Astrophysics Data System (ADS)

    Hu, Litang; Jiao, Jiu Jimmy

    2015-11-01

    Traditional numerical models usually use extensive observed hydraulic-head data as calibration targets. However, this calibration process is not applicable in remote areas with limited or no monitoring data. This study presents an approach to calibrate a large-scale groundwater flow model using the monthly Gravity Recovery and Climate Experiment (GRACE) satellite data, which have been available globally on a spatial grid of 1° in the geographic coordinate system since 2002. A groundwater storage anomaly isolated from the terrestrial water storage (TWS) anomaly is converted into hydraulic head at the center of the grid, which is then used as observed data to calibrate a numerical model to estimate aquifer hydraulic conductivity. The aquifer system in the remote and hyperarid Qaidam Basin, China, is used as a case study to demonstrate the applicability of this approach. A groundwater model using FEFLOW is constructed for the Qaidam Basin and the GRACE-derived groundwater storage anomaly over the period 2003-2012 is included to calibrate the model, which is done using an automatic estimation method (PEST). The calibrated model is then run to output hydraulic heads at three sites where long-term hydraulic head data are available. The reasonably good fit between the calculated and observed hydraulic heads, together with the very similar groundwater storage anomalies from the numerical model and GRACE data, demonstrate that this approach is generally applicable in regions of groundwater data scarcity.

  14. Analysis of confidence in continental-scale groundwater recharge estimates for Africa using a distributed water balance model

    NASA Astrophysics Data System (ADS)

    Mackay, Jonathan; Mansour, Majdi; Bonsor, Helen; Pachocka, Magdalena; Wang, Lei; MacDonald, Alan; Macdonald, David; Bloomfield, John

    2014-05-01

    There is a growing need for improved access to reliable water in Africa as population and food production increases. Currently approximately 300 million people do not have access to a secure source of safe drinking water. To meet these current and future demands, groundwater will need to be increasingly abstracted; groundwater is more reliable than surface water sources due to its relatively long response time to meteorological stresses and therefore is likely to be a more secure water resource in a more variable climate. Recent studies also quantified the volumes of groundwater potentially available which suggest that, if exploited, groundwater could help to meet the demand for fresh water. However, there is still considerable uncertainty as to how these resources may respond in the future due to changes in groundwater recharge and abstraction. Understanding and quantifying groundwater recharge is vital as it forms a primary indicator of the sustainability of underlying groundwater resources. Computational hydrological models provide a means to do this, but the complexity of recharge processes in Africa mean that these simulations are often highly uncertain. This study aims to evaluate our confidence in simulating groundwater recharge over Africa based on a sensitivity analysis using a distributed hydrological model developed by the British Geological Survey, ZOODRM. The model includes land surface, canopy, river, soil and groundwater components. Each component is able to exchange water and as such, forms a distributed water balance of Africa. The components have been parameterised using available spatial datasets of African vegetation, land-use, soil and hydrogeology while the remaining parameters have been estimated by calibrating the model to available river flow data. Continental-scale gridded precipitation and potential evapotranspiration datasets, based on remotely sensed and ground observations, have been used to force the model. Following calibration, the sensitivity analysis has been undertaken in two stages. For the first stage, individual parameters are perturbed from each component of the model. For the second stage, different methods for calculating groundwater recharge are introduced. Both stages aim to investigate which aspects of the model most impact on groundwater recharge and consequently how confidently we can simulate the complex recharge processes that occur in Africa using large scale hydrological models. Preliminary results from the analysis indicate the parameters that control runoff generation from the land surface and the choice of groundwater recharge calculation method both have a significant impact on groundwater recharge simulations.

  15. Submarine groundwater discharge to a small estuary estimated from radon and salinity measurements and a box model

    USGS Publications Warehouse

    Crusius, J.; Koopmans, D.; Bratton, J.F.; Charette, M.A.; Kroeger, K.D.; Henderson, P.; Ryckman, L.; Halloran, K.; Colman, J.A.

    2005-01-01

    Submarine groundwater discharge was quantified by a variety of methods in Salt Pond, adjacent to Nauset Marsh on Cape Cod, USA. Discharge estimates based on radon and salinity took advantage of the presence of the narrow channel connecting Salt Pond to Nauset Marsh, which allowed constructing whole-pond mass balances as water flowed in and out due to tidal fluctuations. A box model was used to estimate discharge separately to Salt Pond and to the channel by simulating the timing and magnitude of variations in the radon and salinity data in the channel. Discharge to the pond is estimated to be 2200??1100 m3 d-1, while discharge to the channel is estimated to be 300??150m3 d-1, for a total discharge of 2500??1250 m3 d-1 to the Salt Pond system. This translates to an average groundwater flow velocity of 3??1.5 cm d -1. Seepage meter flow estimates are broadly consistent with this figure, provided discharge is confined to shallow sediments (water depth <1 m). The radon data can be modeled assuming all groundwater fluxes to both the channel and to the pond are fresh, with no need to invoke a saline component. The absence of a saline component in the radon flux may be due to removal of radon from saline groundwater by recent advection of seawater or it may to due to the presence of impermeable sediments in the center of the pond that limit seawater recirculation. This groundwater flux estimated from the radon and salinity data is comparable to a value of 3200-4500 m3 d-1 predicted by a recent hydrologic model (Masterson, 2004; Colman and Masterson, 20041). Additional work is needed to determine if the measured rate of discharge is representative of the long-term average, and to determine the rate of groundwater discharge seaward of Salt Pond. Data also suggest a TDN flux from groundwater to Salt Pond of ???2.6 mmol m-2 d-1, a figure comparable to fluxes observed in other eutrophic settings.

  16. Effect of groundwater flow on remediation of dissolved-phase VOC contamination using air sparging.

    PubMed

    Reddy, K R; Adams, J A

    2000-02-25

    This paper presents two-dimensional laboratory experiments performed to study how groundwater flow may affect the injected air zone of influence and remedial performance, and how injected air may alter subsurface groundwater flow and contaminant migration during in situ air sparging. Tests were performed by subjecting uniform sand profiles contaminated with dissolved-phase benzene to a hydraulic gradient and two different air flow rates. The results of the tests were compared to a test subjected to a similar air flow rate but a static groundwater condition. The test results revealed that the size and shape of the zone of influence were negligibly affected by groundwater flow, and as a result, similar rates of contaminant removal were realized within the zone of influence with and without groundwater flow. The air flow, however, reduced the hydraulic conductivity within the zone of influence, reducing groundwater flow and subsequent downgradient contaminant migration. The use of a higher air flow rate further reduced the hydraulic conductivity and decreased groundwater flow and contaminant migration. Overall, this study demonstrated that air sparging may be effectively implemented to intercept and treat a migrating contaminant plume. PMID:10650188

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

    USGS Publications Warehouse

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

    2013-01-01

    The Edwards-Trinity aquifer is a vital groundwater resource for agricultural, industrial, and municipal uses in the Trans-Pecos region of west Texas. A conceptual model of the hydrogeologic framework, geochemistry, and groundwater-flow system in the 4,700 square-mile study area was developed by the U.S. Geological Survey (USGS) in cooperation with the Middle Pecos Groundwater Conservation District, Pecos County, City of Fort Stockton, Brewster County, and Pecos County Water Control and Improvement District No. 1. The model was developed to gain a better understanding of the groundwater system and to establish a scientific foundation for resource-management decisions. Data and information were collected or obtained from various sources to develop the model. Lithologic information obtained from well reports and geophysical data were used to describe the hydrostratigraphy and structural features of the groundwater system, and aquifer-test data were used to estimate aquifer hydraulic properties. Groundwater-quality data were used to evaluate groundwater-flow paths, water and rock interaction, aquifer interaction, and the mixing of water from different sources. Groundwater-level data also were used to evaluate aquifer interaction as well as to develop a potentiometric-surface map, delineate regional groundwater divides, and describe regional groundwater-flow paths. Several previous studies have been done to compile or collect physical and chemical data, describe the hydrogeologic processes, and develop conceptual and numerical groundwater-flow models of the Edwards-Trinity aquifer in the Trans-Pecos region. Documented methods were used to compile and collect groundwater, surface-water, geochemical, geophysical, and geologic information that subsequently were used to develop this conceptual model.

  18. Sensitivity Analysis for Steady State Groundwater Flow Using Adjoint Operators

    NASA Astrophysics Data System (ADS)

    Sykes, J. F.; Wilson, J. L.; Andrews, R. W.

    1985-03-01

    Adjoint sensitivity theory is currently being considered as a potential method for calculating the sensitivity of nuclear waste repository performance measures to the parameters of the system. For groundwater flow systems, performance measures of interest include piezometric heads in the vicinity of a waste site, velocities or travel time in aquifers, and mass discharge to biosphere points. The parameters include recharge-discharge rates, prescribed boundary heads or fluxes, formation thicknesses, and hydraulic conductivities. The derivative of a performance measure with respect to the system parameters is usually taken as a measure of sensitivity. To calculate sensitivities, adjoint sensitivity equations are formulated from the equations describing the primary problem. The solution of the primary problem and the adjoint sensitivity problem enables the determination of all of the required derivatives and hence related sensitivity coefficients. In this study, adjoint sensitivity theory is developed for equations of two-dimensional steady state flow in a confined aquifer. Both the primary flow equation and the adjoint sensitivity equation are solved using the Galerkin finite element method. The developed computer code is used to investigate the regional flow parameters of the Leadville Formation of the Paradox Basin in Utah. The results illustrate the sensitivity of calculated local heads to the boundary conditions. Alternatively, local velocity related performance measures are more sensitive to hydraulic conductivities.

  19. Evaluation of Parameter Uncertainty Reduction in Groundwater Flow Modeling Using Multiple Environmental Tracers

    NASA Astrophysics Data System (ADS)

    Arnold, B. W.; Gardner, P.

    2013-12-01

    Calibration of groundwater flow models for the purpose of evaluating flow and aquifer heterogeneity typically uses observations of hydraulic head in wells and appropriate boundary conditions. Environmental tracers have a wide variety of decay rates and input signals in recharge, resulting in a potentially broad source of additional information to constrain flow rates and heterogeneity. A numerical study was conducted to evaluate the reduction in uncertainty during model calibration using observations of various environmental tracers and combinations of tracers. A synthetic data set was constructed by simulating steady groundwater flow and transient tracer transport in a high-resolution, 2-D aquifer with heterogeneous permeability and porosity using the PFLOTRAN software code. Data on pressure and tracer concentration were extracted at well locations and then used as observations for automated calibration of a flow and transport model using the pilot point method and the PEST code. Optimization runs were performed to estimate parameter values of permeability at 30 pilot points in the model domain for cases using 42 observations of: 1) pressure, 2) pressure and CFC11 concentrations, 3) pressure and Ar-39 concentrations, and 4) pressure, CFC11, Ar-39, tritium, and He-3 concentrations. Results show significantly lower uncertainty, as indicated by the 95% linear confidence intervals, in permeability values at the pilot points for cases including observations of environmental tracer concentrations. The average linear uncertainty range for permeability at the pilot points using pressure observations alone is 4.6 orders of magnitude, using pressure and CFC11 concentrations is 1.6 orders of magnitude, using pressure and Ar-39 concentrations is 0.9 order of magnitude, and using pressure, CFC11, Ar-39, tritium, and He-3 concentrations is 1.0 order of magnitude. Data on Ar-39 concentrations result in the greatest parameter uncertainty reduction because its half-life of 269 years is similar to the range of transport times (hundreds to thousands of years) in the heterogeneous synthetic aquifer domain. The slightly higher uncertainty range for the case using all of the environmental tracers simultaneously is probably due to structural errors in the model introduced by the pilot point regularization scheme. It is concluded that maximum information and uncertainty reduction for constraining a groundwater flow model is obtained using an environmental tracer whose half-life is well matched to the range of transport times through the groundwater flow system. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  20. Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

    NASA Astrophysics Data System (ADS)

    Hernández-Antonio, A.; Mahlknecht, J.; Tamez-Meléndez, C.; Ramos-Leal, J.; Ramírez-Orozco, A.; Parra, R.; Ornelas-Soto, N.; Eastoe, C. J.

    2015-09-01

    Groundwater chemistry and isotopic data from 40 production wells in the Atemajac and Toluquilla valleys, located in and around the Guadalajara metropolitan area, were determined to develop a conceptual model of groundwater flow processes and mixing. Stable water isotopes (?2H, ?18O) were used to trace hydrological processes and tritium (3H) to evaluate the relative contribution of modern water in samples. Multivariate analysis including cluster analysis and principal component analysis were used to elucidate distribution patterns of constituents and factors controlling groundwater chemistry. Based on this analysis, groundwater was classified into four groups: cold groundwater, hydrothermal groundwater, polluted groundwater and mixed groundwater. Cold groundwater is characterized by low temperature, salinity, and Cl and Na concentrations and is predominantly of Na-HCO3-type. It originates as recharge at "La Primavera" caldera and is found predominantly in wells in the upper Atemajac Valley. Hydrothermal groundwater is characterized by high salinity, temperature, Cl, Na and HCO3, and the presence of minor elements such as Li, Mn and F. It is a mixed-HCO3 type found in wells from Toluquilla Valley and represents regional flow circulation through basaltic and andesitic rocks. Polluted groundwater is characterized by elevated nitrate and sulfate concentrations and is usually derived from urban water cycling and subordinately from agricultural return flow. Mixed groundwaters between cold and hydrothermal components are predominantly found in the lower Atemajac Valley. Twenty-seven groundwater samples contain at least a small fraction of modern water. The application of a multivariate mixing model allowed the mixing proportions of hydrothermal fluids, polluted waters and cold groundwater in sampled water to be evaluated. This study will help local water authorities to identify and dimension groundwater contamination, and act accordingly. It may be broadly applicable to other active volcanic systems on Earth.

  1. Groundwater Flow and Sand Body Interconnectedness in a Thick, Multiple-Aquifer System

    NASA Astrophysics Data System (ADS)

    Fogg, Graham E.

    1986-05-01

    Many so-called sandstone aquifers are actually multiple-aquifer systems consisting of discontinuous sand bodies distributed complexly in a matrix of lower-permeability silts and clays. The arrangement and Interconnectedness of these various lithofacies strongly influence spatial patterns of hydraulic conductivity (K) and, in turn, groundwater flow and mass transport. A promising technique of estimating such patterns of K involves careful analysis of both subsurface geologic and subsurface hydrologic data. In this study the three-dimensional distribution of K was estimated for a numerical flow model of part of the Wilcox aquifer system in Texas, using K data from core samples and pumping tests and more than 100 geophysical logs. The aquifer system, which is up to 320 m thick, consists of multiple, elongate sand bodies and silts and clays deposited in a fluvial environment and is similar to many other systems found in the Gulf Coast and other sedimentary basins. The resulting deterministic-conceptual flow model demonstrates the importance and methods of incorporating geologic information in groundwater models. Flow in the aquifer is shown to be controlled not so much by K of the sands as by their continuity and Interconnectedness. Much of the aquifer system consists of large zones in which the fluvial channel-fill sands are sparse and apparently disconnected, resulting in groundwater flow rates lower by a factor of 101 to 103 than in adjacent, well-interconnected belts of fluvial channel-fill sand belts. Modeling results also raise serious doubts regarding our ability to predict regional scale flow and mass transport in complex aquifers such as the Wilcox, using current technology. Though sand body Interconnectedness is critically important, it is also very difficult to estimate. One or two well-connected sands among a system of otherwise disconnected sands can completely alter a velocity field. This is particularly true if the sands are connected vertically and nonzero vertical hydraulic gradients exist. Because the model is three-dimensional, sensitivity of hydraulic head to heterogeneity or Interconnectedness is much less than normally observed in two-dimensional models, and therefore heads computed by the model give little to no indication of the location of well-interconnected zones. Thus such zones can easily go undetected, even in carefully calibrated models which yield reasonably accurate hydraulic heads. This is a significant point for modeling of solute transport.

  2. Regional groundwater flow and tritium transport modeling and risk assessment of the underground test area, Nevada Test Site, Nevada

    SciTech Connect

    1997-10-01

    The groundwater flow system of the Nevada Test Site and surrounding region was evaluated to estimate the highest potential current and near-term risk to the public and the environment from groundwater contamination downgradient of the underground nuclear testing areas. The highest, or greatest, potential risk is estimated by assuming that several unusually rapid transport pathways as well as public and environmental exposures all occur simultaneously. These conservative assumptions may cause risks to be significantly overestimated. However, such a deliberate, conservative approach ensures that public health and environmental risks are not underestimated and allows prioritization of future work to minimize potential risks. Historical underground nuclear testing activities, particularly detonations near or below the water table, have contaminated groundwater near testing locations with radioactive and nonradioactive constituents. Tritium was selected as the contaminant of primary concern for this phase of the project because it is abundant, highly mobile, and represents the most significant contributor to the potential radiation dose to humans for the short term. It was also assumed that the predicted risk to human health and the environment from tritium exposure would reasonably represent the risk from other, less mobile radionuclides within the same time frame. Other contaminants will be investigated at a later date. Existing and newly collected hydrogeologic data were compiled for a large area of southern Nevada and California, encompassing the Nevada Test Site regional groundwater flow system. These data were used to develop numerical groundwater flow and tritium transport models for use in the prediction of tritium concentrations at hypothetical human and ecological receptor locations for a 200-year time frame. A numerical, steady-state regional groundwater flow model was developed to serve as the basis for the prediction of the movement of tritium from the underground testing areas on a regional scale. The groundwater flow model was used in conjunction with a particle-tracking code to define the pathlines followed by groundwater particles originating from 415 points associated with 253 nuclear test locations. Three of the most rapid pathlines were selected for transport simulations. These pathlines are associated with three nuclear test locations, each representing one of the three largest testing areas. These testing locations are: BOURBON on Yucca Flat, HOUSTON on Central Pahute Mesa, and TYBO on Western Pahute Mesa. One-dimensional stochastic tritium transport simulations were performed for the three pathlines using the Monte Carlo method with Latin hypercube sampling. For the BOURBON and TYBO pathlines, sources of tritium from other tests located along the same pathline were included in the simulations. Sensitivity analyses were also performed on the transport model to evaluate the uncertainties associated with the geologic model, the rates of groundwater flow, the tritium source, and the transport parameters. Tritium concentration predictions were found to be mostly sensitive to the regional geology in controlling the horizontal and vertical position of transport pathways. The simulated concentrations are also sensitive to matrix diffusion, an important mechanism governing the migration of tritium in fractured carbonate and volcanic rocks. Source term concentration uncertainty is most important near the test locations and decreases in importance as the travel distance increases. The uncertainty on groundwater flow rates is as important as that on matrix diffusion at downgradient locations. The risk assessment was performed to provide conservative and bounding estimates of the potential risks to human health and the environment from tritium in groundwater. Risk models were designed by coupling scenario-specific tritium intake with tritium dose models and cancer and genetic risk estimates using the Monte Carlo method. Estimated radiation doses received by individuals from chronic exposure to tritium, and the corre

  3. Groundwater flow near the Shoal Site, Sand Springs Range, Nevada: Impact of density-driven flow

    SciTech Connect

    Chapman, J.; Mihevc, T.; McKay, A.

    1994-09-01

    The nature of flow from a highland recharge area in a mountain range in north-central Nevada to discharge areas on either side of the range is evaluated to refine a conceptual model of contaminant transport from an underground nuclear test conducted beneath the range. The test, known as the Shoal event, was conducted in 1963 in granitic rocks of the Sand Springs Range. Sparse hydraulic head measurements from the early 1960s suggest flow from the shot location to the east to Fairview Valley, while hydrochemistry supports flow to salt pans in Fourmile Flat to the west. Chemical and isotopic data collected from water samples and during well-logging arc best explained by a reflux brine system on the west side of the Sand Springs Range, rather than a typical local flow system where all flow occurs from recharge areas in the highlands to a central discharge area in a playa. Instead, dense saline water from the playa is apparently being driven toward the range by density contrasts. The data collected between the range and Fourmile Flat suggest the groundwater is a mixture of younger, fresher recharge water with older brine. Chemical contrasts between groundwater in the east and west valleys reflect the absence of re-flux water in Fairview Valley because the regional discharge area is distant and thus there is no accumulation of salts. The refluxing hydraulic system probably developed after the end of the last pluvial period and differences between the location of the groundwater divide based on hydraulic and chemical indicators could reflect movement of the divide as the groundwater system adjusts to the new reflux condition.

  4. Simulation of the shallow groundwater-flow system near the Hayward Airport, Sawyer County, Wisconsin

    USGS Publications Warehouse

    Hunt, Randall J.; Juckem, Paul F.; Dunning, Charles P.

    2010-01-01

    There are concerns that removal and trimming of vegetation during expansion of the Hayward Airport in Sawyer County, Wisconsin, could appreciably change the character of a nearby cold-water stream and its adjacent environs. In cooperation with the Wisconsin Department of Transportation, a two-dimensional, steady-state groundwater-flow model of the shallow groundwater-flow system near the Hayward Airport was refined from a regional model of the area. The parameter-estimation code PEST was used to obtain a best fit of the model to additional field data collected in February 2007 as part of this study. The additional data were collected during an extended period of low runoff and consisted of water levels and streamflows near the Hayward Airport. Refinements to the regional model included one additional hydraulic-conductivity zone for the airport area, and three additional parameters for streambed resistance in a northern tributary to the Namekagon River and in the main stem of the Namekagon River. In the refined Hayward Airport area model, the calibrated hydraulic conductivity was 11.2 feet per day, which is within the 58.2 to 7.9 feet per day range reported for the regional glacial and sandstone aquifer, and is consistent with a silty soil texture for the area. The calibrated refined model had a best fit of 8.6 days for the streambed resistance of the Namekagon River and between 0.6 and 1.6 days for the northern tributary stream. The previously reported regional groundwater-recharge rate of 10.1 inches per year was adjusted during calibration of the refined model in order to match streamflows measured during the period of extended low runoff; this resulted in an optimal groundwater-recharge rate of 7.1 inches per year during this period. The refined model was then used to simulate the capture zone of the northern tributary to the Namekagon River.

  5. Calibrating SWAT with River flows, Groundwater table, and GRACE

    NASA Astrophysics Data System (ADS)

    Qiao, L.

    2010-12-01

    Various combinations of model parameters can provide equal simulations for certain water component (like river discharge) due to compensating interactions among parameters in most hydrologic models. SWAT (Soil and Water Assessment Tool) physically simulates the movements and distributions for water, sediments and nutrients with widely varied parameters usually encountering this kind of problem. Previous SWAT applications mostly limited model calibrations on surface runoff (sometime including nutrients and sediments) and lose overall control to the whole hydrologic process consisting of ET, Surface runoff, soil water, and ground water variations. This study constrains the SWAT model in lower Missouri River Basin with surface water recharge and discharge (river flows), basin-wide water storage (Gravity Recovery and Climate Experiment (GRACE)), Groundwater table fluctuations(well logs) under a SUFI (sequential uncertainty fitting) framework. This would reduce the parameter uncertainty and provide reliable model for hydrologic studies within the basin.

  6. Multiple, distinct groundwater flow systems of a single moraine-talus feature in an alpine watershed

    NASA Astrophysics Data System (ADS)

    Roy, James W.; Hayashi, Masaki

    2009-06-01

    SummaryRecent studies suggest that talus slopes and moraines likely play an important role in groundwater flow and storage in alpine watersheds, though the subsurface processes of these unconsolidated sediment features are not fully understood. To gain insight into these groundwater systems, we investigated the spatial variability in groundwater properties and hydrological trends of a large spring and several nearby (?200 m) springs, discharging from a single moraine-talus feature in an alpine watershed in the Canadian Rockies. A key question was whether groundwater flow in these features is reasonably homogeneous. Hydrograph analyses revealed at least two different groundwater responses to precipitation and melt inputs: a rapid and likely localized response and a slower response indicating a subsurface connection to a nearby lake. There was also a large spread in groundwater composition across the large spring and between springs, including a consistent linear trend in major ion chemistry over a 20-m section of the large spring. The spatial and temporal trends in groundwater chemistry data suggests there are three groundwater components associated with this sediment feature, and that their relative contributions vary temporally, though the component associated with the lake appears dominant. The study findings suggest that unconsolidated sediment features can possess multiple, and possibly disconnected, groundwater flow paths exhibiting unique hydrological and geochemical characteristics, and cannot necessarily be treated as a single, homogeneous groundwater component when modeling the hydrology of alpine watersheds.

  7. Estimating groundwater recharge beneath irrigated farmland using environmental tracers fluoride, chloride and sulfate

    NASA Astrophysics Data System (ADS)

    Lin, Dan; Jin, Menggui; Liang, Xing; Zhan, Hongbin

    2013-11-01

    Accurate recharge estimation is essential for effective groundwater management, especially in the North China Plain, where irrigation return flow is significant to vertical recharge but brings difficulty for recharge estimation. Three environmental tracers (F-, Cl- and SO4 2-) were used to estimate vertical recharge based on the mass balance and cumulative methods. Four boreholes were dry-drilled to 5-25 m depth beneath irrigated farmland and one was drilled to 5 m beneath non-irrigated woodland; soil samples were collected in all boreholes at set depths. The results indicated that F-, Cl- and SO4 2-were suitable tracers beneath the non-irrigated woodland, yielding recharge rates of 16.9, 18.8 and 19.4 mm/year, respectively. Recharge estimation was not straightforward when taking account of crop type, irrigation and/or fertilizer use. After comparing with previous research, conclusions were drawn: Cl- was an appropriate tracer for irrigated farmland when taking account of Cl- input from irrigation and absorption by crops; recharge rates were 65.9-126.8 mm/year. However, F- was a more suitable tracer for irrigated regions where account is made of the proportion of precipitation to irrigation return flow, provided low F- concentrations can be measured reliably.

  8. Modeling Steady-State Groundwater Flow Using Microcomputer Spreadsheets.

    ERIC Educational Resources Information Center

    Ousey, John Russell, Jr.

    1986-01-01

    Describes how microcomputer spreadsheets are easily adapted for use in groundwater modeling. Presents spreadsheet set-ups and the results of five groundwater models. Suggests that this approach can provide a basis for demonstrations, laboratory exercises, and student projects. (ML)

  9. Assessment of groundwater level estimation uncertainty using sequential Gaussian simulation and Bayesian bootstrapping

    NASA Astrophysics Data System (ADS)

    Varouchakis, Emmanouil; Hristopulos, Dionissios

    2015-04-01

    Space-time geostatistical approaches can improve the reliability of dynamic groundwater level models in areas with limited spatial and temporal data. Space-time residual Kriging (STRK) is a reliable method for spatiotemporal interpolation that can incorporate auxiliary information. The method usually leads to an underestimation of the prediction uncertainty. The uncertainty of spatiotemporal models is usually estimated by determining the space-time Kriging variance or by means of cross validation analysis. For de-trended data the former is not usually applied when complex spatiotemporal trend functions are assigned. A Bayesian approach based on the bootstrap idea and sequential Gaussian simulation are employed to determine the uncertainty of the spatiotemporal model (trend and covariance) parameters. These stochastic modelling approaches produce multiple realizations, rank the prediction results on the basis of specified criteria and capture the range of the uncertainty. The correlation of the spatiotemporal residuals is modeled using a non-separable space-time variogram based on the Spartan covariance family (Hristopulos and Elogne 2007, Varouchakis and Hristopulos 2013). We apply these simulation methods to investigate the uncertainty of groundwater level variations. The available dataset consists of bi-annual (dry and wet hydrological period) groundwater level measurements in 15 monitoring locations for the time period 1981 to 2010. The space-time trend function is approximated using a physical law that governs the groundwater flow in the aquifer in the presence of pumping. The main objective of this research is to compare the performance of two simulation methods for prediction uncertainty estimation. In addition, we investigate the performance of the Spartan spatiotemporal covariance function for spatiotemporal geostatistical analysis. Hristopulos, D.T. and Elogne, S.N. 2007. Analytic properties and covariance functions for a new class of generalized Gibbs random fields. I??? Transactions on Information Theory, 53:4667-4467. Varouchakis, E.A. and Hristopulos, D.T. 2013. Improvement of groundwater level prediction in sparsely gauged basins using physical laws and local geographic features as auxiliary variables. Advances in Water Resources, 52:34-49. Research supported by the project SPARTA 1591: "Development of Space-Time Random Fields based on Local Interaction Models and Applications in the Processing of Spatiotemporal Datasets". "SPARTA" is implemented under the "ARISTEIA" Action of the operational programme Education and Lifelong Learning and is co-funded by the European Social Fund (ESF) and National Resources.

  10. Hydrogeology and Ground-Water Flow in the Opequon Creek Watershed area, Virginia and West Virginia

    USGS Publications Warehouse

    Kozar, Mark D.; Weary, David J.

    2009-01-01

    Due to increasing population and economic development in the northern Shenandoah Valley of Virginia and West Virginia, water availability has become a primary concern for water-resource managers in the region. To address these issues, the U.S. Geological Survey (USGS), in cooperation with the West Virginia Department of Health and Human Services and the West Virginia Department of Environmental Protection, developed a numerical steady-state simulation of ground-water flow for the 1,013-square-kilometer Opequon Creek watershed area. The model was based on data aggregated for several recently completed and ongoing USGS hydrogeologic investigations conducted in Jefferson, Berkeley, and Morgan Counties in West Virginia and Clarke, Frederick, and Warren Counties in Virginia. A previous detailed hydrogeologic assessment of the watershed area of Hopewell Run (tributary to the Opequon Creek), which includes the USGS Leetown Science Center in Jefferson County, West Virginia, provided key understanding of ground-water flow processes in the aquifer. The ground-water flow model developed for the Opequon Creek watershed area is a steady-state, three-layer representation of ground-water flow in the region. The primary objective of the simulation was to develop water budgets for average and drought hydrologic conditions. The simulation results can provide water managers with preliminary estimates on which water-resource decisions may be based. Results of the ground-water flow simulation of the Opequon Creek watershed area indicate that hydrogeologic concepts developed for the Hopewell Run watershed area can be extrapolated to the larger watershed model. Sensitivity analyses conducted as part of the current modeling effort and geographic information system analyses of spring location and yield reveal that thrust and cross-strike faults and low-permeability bedding, which provide structural and lithologic controls, respectively, on ground-water flow, must be incorporated into the model to develop a realistic simulation of ground-water flow in the larger Opequon Creek watershed area. In the model, recharge for average hydrologic conditions was 689 m3/d/km2 (cubic meters per day per square kilometer) over the entire Opequon Creek watershed area. Mean and median measured base flows at the streamflow-gaging station on the Opequon Creek near Martinsburg, West Virginia, were 604,384 and 349,907 m3/d (cubic meters per day), respectively. The simulated base flow of 432,834 m3/d fell between the mean and median measured stream base flows for the station. Simulated base-flow yields for subwatersheds during average conditions ranged from 0 to 2,643 m3/d/km2, and the median for the entire Opequon Creek watershed area was 557 m3/d/km2. A drought was simulated by reducing model recharge by 40 percent, a rate that approximates the recharge during the prolonged 16-month drought that affected the region from November 1998 to February 2000. Mean and median measured streamflows for the Opequon Creek watershed area at the Martinsburg, West Virginia, streamflow-gaging station during the 1999 drought were 341,098 and 216,551 m3/d, respectively. The simulated drought base flow at the station of 252,356 m3/d is within the range of flows measured during the 1999 drought. Recharge was 413 m3/d/km2 over the entire watershed during the simulated drought, and was 388 m3/d/km2 at the gaging station. Simulated base-flow yields for drought conditions ranged from 0 to 1,865 m3/d/km2 and averaged 327 m3/d/km2 over the entire Opequon Creek watershed. Water budgets developed from the simulation results indicate a substantial component of direct ground-water discharge to the Potomac River. This phenomenon had long been suspected but had not been quantified. During average conditions, approximately 564,176 m3/d of base flow discharges to the Potomac River. An additional 124,379 m3/d of ground water is also estimated to discharge directly to the Potomac River and rep

  11. RAFT: A simulator for ReActive Flow and Transport of groundwater contaminants

    SciTech Connect

    Chilakapati, A.

    1995-07-01

    This report documents the use of the simulator RAFT for the ReActive flow and Transport of groundwater contaminants. RAFT can be used as a predictive tool in the design and analysis of laboratory and field experiments or it can be used for the estimation of model/process parameters from experiments. RAFT simulates the reactive transport of groundwater contaminants in one, two-, or three-dimensions and it can model user specified source/link configurations and arbitrary injection strategies. A suite of solvers for transport, reactions and regression are employed so that a combination of numerical methods best suited for a problem can be chosen. User specified coupled equilibrium and kinetic reaction systems can be incorporated into RAFT. RAFT is integrated with a symbolic computational language MAPLE, to automate code generation for arbitrary reaction systems. RAFT is expected to be used as a simulator for engineering design for field experiments in groundwater remediation including bioremediation, reactive barriers and redox manipulation. As an integrated tool with both the predictive ability and the ability to analyze experimental data, RAFT can help in the development of remediation technologies, from laboratory to field.

  12. Streambed Temperatures and Heat Budget Estimates in Groundwater-fed Streams

    NASA Astrophysics Data System (ADS)

    Middleton, M.; Allen, D. M.; Whitfield, P. H.

    2013-12-01

    A streambed temperature monitoring network was installed in a groundwater-fed stream in the Lower Fraser Valley of British Columbia. A network of fifteen temperature loggers was installed in a short reach (<40 m) of Fishtrap Creek to characterize the spatial and temporal variability in streambed temperatures and identify potential mechanisms for localized cooling based on heat exchanges during the summer low flow period. This reach has uniform channel form and water depth, and consistent bed material. Streambed temperature data were collected hourly for the period of July 2008 through October 2012, spanning five summer low flow periods. Nearby climate, stream discharge, and groundwater monitoring stations provided the data to estimate the heat budget components. Over the five summer low flow periods, the network of dataloggers recorded a mean streambed temperature of 13.8oC, with a range of 10.2oC to 20.0oC across the streambed. In order to assess controls on streambed temperature at individual datalogger locations, the incoming heat from sources acting across the entire reach had to be removed from the observed temperature signals. The incoming heat was calculated for the air-water interface to estimate the energy flux into the reach using a heat balance. Incoming solar radiation dominates the heat balance, and evaporative heat fluxes were noticeable as small amplitude variations at a daily scale. Precipitation occurrence, or absence, was not an important component of the heat balance during the summer low flow period. Since incoming solar radiation dominates both air and water temperatures, air temperature (Ta) can be used as a proxy for streambed temperature (Ts). The actual lag time between the air and streambed temperature for this site was 30 hours; however, for the calculation of stream temperature at a daily time step, a lag of 24 hours was used. The relationship between daily streambed temperature and daily air temperature, at a lag of one day, was determined empirically for the site as Ts(t) = 5.59 + 0.48 *Ta(t-1day), where T is in degrees C. Almost 90 percent of the variance in streambed temperature can be explained by this lagged air temperature signal. Since this reach is physically uniform, the observed variability in streambed temperatures that are not explained by water temperature can be attributed to variations in groundwater flux.

  13. EVALUATING UNCERTAINTIES IN GROUND-WATER RECHARGE ESTIMATES THROUGH ADVANCED MONITORING

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Risk, as estimated by many multimedia environmental models, is highly sensitive to infiltration and ground-water recharge. This field study used high-frequency monitoring of vadose-zone water content and piezometric levels to build confidence in modeling of infiltration and ground-water recharge. ...

  14. Application of nonlinear-regression methods to a ground-water flow model of the Albuquerque Basin, New Mexico

    USGS Publications Warehouse

    Tiedeman, C.R.; Kernodle, J.M.; McAda, D.P.

    1998-01-01

    This report documents the application of nonlinear-regression methods to a numerical model of ground-water flow in the Albuquerque Basin, New Mexico. In the Albuquerque Basin, ground water is the primary source for most water uses. Ground-water withdrawal has steadily increased since the 1940's, resulting in large declines in water levels in the Albuquerque area. A ground-water flow model was developed in 1994 and revised and updated in 1995 for the purpose of managing basin ground- water resources. In the work presented here, nonlinear-regression methods were applied to a modified version of the previous flow model. Goals of this work were to use regression methods to calibrate the model with each of six different configurations of the basin subsurface and to assess and compare optimal parameter estimates, model fit, and model error among the resulting calibrations. The Albuquerque Basin is one in a series of north trending structural basins within the Rio Grande Rift, a region of Cenozoic crustal extension. Mountains, uplifts, and fault zones bound the basin, and rock units within the basin include pre-Santa Fe Group deposits, Tertiary Santa Fe Group basin fill, and post-Santa Fe Group volcanics and sediments. The Santa Fe Group is greater than 14,000 feet (ft) thick in the central part of the basin. During deposition of the Santa Fe Group, crustal extension resulted in development of north trending normal faults with vertical displacements of as much as 30,000 ft. Ground-water flow in the Albuquerque Basin occurs primarily in the Santa Fe Group and post-Santa Fe Group deposits. Water flows between the ground-water system and surface-water bodies in the inner valley of the basin, where the Rio Grande, a network of interconnected canals and drains, and Cochiti Reservoir are located. Recharge to the ground-water flow system occurs as infiltration of precipitation along mountain fronts and infiltration of stream water along tributaries to the Rio Grande; subsurface flow from adjacent regions; irrigation and septic field seepage; and leakage through the Rio Grande, canal, and Cochiti Reservoir beds. Ground water is discharged from the basin by withdrawal; evapotranspiration; subsurface flow; and flow to the Rio Grande, canals, and drains. The transient, three-dimensional numerical model of ground-water flow to which nonlinear-regression methods were applied simulates flow in the Albuquerque Basin from 1900 to March 1995. Six different basin subsurface configurations are considered in the model. These configurations are designed to test the effects of (1) varying the simulated basin thickness, (2) including a hypothesized hydrogeologic unit with large hydraulic conductivity in the western part of the basin (the west basin high-K zone), and (3) substantially lowering the simulated hydraulic conductivity of a fault in the western part of the basin (the low-K fault zone). The model with each of the subsurface configurations was calibrated using a nonlinear least- squares regression technique. The calibration data set includes 802 hydraulic-head measurements that provide broad spatial and temporal coverage of basin conditions, and one measurement of net flow from the Rio Grande and drains to the ground-water system in the Albuquerque area. Data are weighted on the basis of estimates of the standard deviations of measurement errors. The 10 to 12 parameters to which the calibration data as a whole are generally most sensitive were estimated by nonlinear regression, whereas the remaining model parameter values were specified. Results of model calibration indicate that the optimal parameter estimates as a whole are most reasonable in calibrations of the model with with configurations 3 (which contains 1,600-ft-thick basin deposits and the west basin high-K zone), 4 (which contains 5,000-ft-thick basin de

  15. Comparison of a karst groundwater model with and without discrete conduit flow

    USGS Publications Warehouse

    Saller, Stephen P.; Ronayne, Michael J.; Long, Andrew J.

    2013-01-01

    Karst aquifers exhibit a dual flow system characterized by interacting conduit and matrix domains. This study evaluated the coupled continuum pipe-flow framework for modeling karst groundwater flow in the Madison aquifer of western South Dakota (USA). Coupled conduit and matrix flow was simulated within a regional finite-difference model over a 10-year transient period. An existing equivalent porous medium (EPM) model was modified to include major conduit networks whose locations were constrained by dye-tracing data and environmental tracer analysis. Model calibration data included measured hydraulic heads at observation wells and estimates of discharge at four karst springs. Relative to the EPM model, the match to observation well hydraulic heads was substantially improved with the addition of conduits. The inclusion of conduit flow allowed for a simpler hydraulic conductivity distribution in the matrix continuum. Two of the high-conductivity zones in the EPM model, which were required to indirectly simulate the effects of conduits, were eliminated from the new model. This work demonstrates the utility of the coupled continuum pipe-flow method and illustrates how karst aquifer model parameterization is dependent on the physical processes that are simulated.

  16. Identification of groundwater parameters at Columbus, Mississippi, using a 3D inverse flow and transport model

    USGS Publications Warehouse

    Barlebo, H.C.; Rosbjerg, D.; Hill, M.C.

    1996-01-01

    An extensive amount of data including hydraulic heads, hydraulic conductivities and concentrations of several solutes from controlled injections have been collected during the MADE 1 and MADE 2 experiments at a heterogeneous site near Columbus, Mississippi. In this paper the use of three-dimensional inverse groundwater models including simultaneous estimation of flow and transport parameters is proposed to help identify the dominant characteristics at the site. Simulations show that using a hydraulic conductivity distribution obtained from 2187 borehole flowmeter tests directly in the model produces poor matches to the measured hydraulic heads and tritium concentrations. Alternatively, time averaged hydraulic head maps are used to define zones of constant hydraulic conductivity to be estimated. Preliminary simulations suggest that in the case of conservative transport many, but not all, of the major plume characteristics can be explained by large-scale heterogeneity in recharge and hydraulic conductivity.

  17. 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, Jody L.; 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.

  18. A closed-form solution for a confined flow into a tunnel during progressive drilling in a multi-layer groundwater flow system

    NASA Astrophysics Data System (ADS)

    Yang, Shaw-Yang; Yeh, Hund-Der

    2007-04-01

    A mathematical model is developed to describe the groundwater inflow into a tunnel in a multi-layer aquifer system. Based on the model, the closed-form solution is derived to estimate the groundwater flow rate entering the multi-layer tunnel during progressive drilling. The solution has an integrand not only consisting of the product and square of the Bessel functions but also having a singularity at the origin. A unified numerical approach is proposed to evaluate the solution with accuracy to five decimal places. This approach includes a singularity removal scheme, the Gaussian quadrature, and the Shanks method. For a multi-layer formation, the results obtained from the solution based on the equivalent hydraulic conductivity and the newly derived solution differ significantly. This solution is capable of estimating the maximum flow rate inside the horizontal tunnel, and thus can be used as a tool for designing the drainage tunnel system in a multi-layer formation.

  19. Applications of remote sensing, GIS, and groundwater flow modeling in evaluating groundwater resources: Two case studies; East Nile Delta, Egypt and Gold Valley, California, USA

    NASA Astrophysics Data System (ADS)

    Abdelaziz Ali Ismael, Abdulaziz Mohamed

    Quaternary aquifer, East Nile Delta, Egypt. Due to the progressive increase in the development of desert land in Egypt, the demand for efficient water resources management and accurate land cover change information is increasing. In this study, we introduce a methodology to map and monitor land cover change patterns related to agricultural development and urban expansion in the desert fringes of the Eastern Nile Delta region. Using a hybrid classification approach, we employ multitemporal Landsat TM/ETM+ images from 1984, 1990, and 2003 to produce three land cover/land use maps. Post-classification comparison of these maps was used to obtain "from-to" statistics and change detection maps. The change detection results show that agricultural development increased 14% through the study period. Land reclamation during 1990-2003 exceeded that during 1984-1990 by a factor of two, reflecting a systematic national plan for desert reclamation that went into effect. We find that the increase in urbanization (by ˜21,300 hectares) during 1990-2003 was predominantly due to encroachment into traditionally cultivated land at the fringes of urban centers. Our results accurately quantify the land cover changes and delineate their spatial patterns, demonstrating the utility of Landsat data in analyzing landscape dynamics over time. Such information is critical for making efficient and sustainable policies for resource management. A three dimensional GIS-based groundwater flow model was developed to delineate a safe future framework for groundwater development in the Quaternary aquifer north Ismaelia Canal, East Nile Delta where a progressive rise in head associated with agricultural development is reported. The calibrated transient model was used to predict the future head distribution after 20 years assuming the same landuse. Results of this run showed that the groundwater head continued to increase with maximum increase up to 2.0 m in the unconfined part of the aquifer which jeopardizes a considerable area of the agricultural land with soil salinity and water logging. Therefore, three strategies, each with three scenarios, extending between 2004 and 2024 were designed to involve different pumping stress and infiltration rates from irrigation return to control the rising water level and estimate the production potential of the aquifer during drought. Gold Valley, Death Valley, California, USA. This study evaluates the hydrogeology of Gold Valley as a typical example of intermountain basins of Death Valley area and develops a GIS-based model that reasonably estimates the precipitation infiltration rates from altitude and slope data of the catchment area. Water balance calculations of the hydrological parameters in Gold Valley, provided by Inyo County, California, indicated that the majority of recharge takes place at high altitude (>1100 m) during winter with a negligible effect of evaporation on the stable isotopic composition of groundwater. Furthermore, water balance calculations in Gold Valley were utilized in identifying the coefficients of a GIS-based model that subsequently was refined to the best fit with the calculations of the water budget. A resistivity survey conducted in Gold Valley showed that groundwater is collected in upstream compartmentalized reservoirs and suggests that groundwater flow mostly takes place through the fracture zone of the bedrock. This pattern explains the relationship between precipitational infiltration in the Gold Valley catchment area and the attachment spring flow in Willow Creek. The estimated water budget in Gold Valley and the geoelectric profiles provided from this study can be investigated into the Death Valley Regional Groundwater Flow model (DVRGWF). In addition, the GIS-based model can be efficiently applied in other intermountain basins in Death Valley or other areas of arid environment of the Western U.S. to estimate the local precipitational infiltration. Accurate estimates of flux, well defined flow systems, and locations of recharge/discharge in mountain ranges provide e

  20. 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.

  1. Characterization of Groundwater Flow Processes in the Cedar Creek Watershed and the Cedarburg Bog in Southeastern Wisconsin

    NASA Astrophysics Data System (ADS)

    Graham, J. P.; Han, W. S.; Feinstein, D.; Hart, D. J.

    2014-12-01

    The purpose of this study is to characterize the geology and groundwater flow of the bog as well as the surrounding area, notably the Cedar Creek Watershed, a HUC (Hydrologic Unit Code) 12 watershed. The watershed is approximately 330 km2, and borders the sub-continental divide separating the Mississippi River Basin from the Great Lakes Basin. The Cedar Creek watershed is composed of mostly agricultural and urban land with a significant stress of groundwater withdrawal for both irrigation and residential use. This watershed has importance due to the contribution to both the Milwaukee River and Lake Michigan, and is integral in the study of regional groundwater flow of Southeastern Wisconsin. Furthermore, the Cedarburg Bog, located in the northeast corner of the Cedar Creek Watershed preserves diverse ecology and is recognized by the U.S. Department of Interior as a National Landmark. Groundwater is the primary driver for the diverse and unique ecology that is contained within the bog. Within the Cedar Creek Watershed, well data and glacial geology maps (Mickelson and Syverson, 1997) were integrated to develop a 3-dimensional subsurface map and watershed-scale groundwater flow model using the LAK3 and the SFR2 package to simulate surface water-aquifer interactions. The model includes 10 zones of the glacial sediments and the weathered and consolidated Silurian Dolomite bedrock. The hydraulic conductivity and storage parameters were calibrated with 203 head targets using universal parameter estimation code (PEST). Then, a series of future climate scenarios, developed by the Wisconsin Initiative on Climate Change Impact, were implemented to the USGS Soil-Water-Balance Code (SWB) to identify variations in recharge. The simulated recharge scenarios were adopted to predict the response of groundwater resources in the watershed and the Cedarburg Bog. Preliminary results produced from the MODFLOW model indicate the bog is acting as a recharge zone under current recharge conditions, approximately 12.7cm/year, with regional groundwater flow from the groundwater divide to Lake Michigan and a mean residual on calibration targets of 4.32mKnowledge acquired from this investigation can be used to better inform local agencies of potential threats, as well as predict future changes within this groundwater system.

  2. Estimating residents' willingness to pay for groundwater protection in the Vietnamese Mekong Delta

    NASA Astrophysics Data System (ADS)

    Vo, Danh Thanh; Huynh, Khai Viet

    2014-11-01

    Groundwater in the Vietnamese Mekong Delta is facing the pollution and it needs to be protected. Searching literature reviews on economic valuation techniques, the contingent valuation method (CVM) has been popularly applied to estimate the economic value of water protection. This approach is based on a hypothetical scenario in which respondents are requested through questionnaires to reveal their maximum willingness to pay (WTP) for the water protection project. The study used the approach of CVM to analyze the households' motivations and their WTP for the program of groundwater protection in the Mekong Delta. The study performed that the residents in the delta were willing to pay approximately 141,730 VND (US6.74) per household a year. Groundwater could be an inferior good with the negative income effect found in the demanding for clean groundwater. Respondent's gender and groundwater-related health risk consideration were factors sensitively affecting the probability of demanding for groundwater protection.

  3. Application of Self-potential Measurements to Investigate Groundwater Flow in Saijo Plain, Western Japan

    NASA Astrophysics Data System (ADS)

    Hachani, F.; Tsujimura, M.; Tosaki, Y.; Goto, T.; Ozaki, Y.; Tokumasu, M.

    2010-12-01

    The self-potential (SP) or natural (electrical) potential method is a passive measurement of the electrical potential distribution at the ground surface. In hydrogeological applications, self-potentials are assumed to be created by an electrokinetic effect when groundwater moves through a porous medium. The artesian water, characterized by a high pressure, is one of the features capable of generating a superficial electrical potential field. We applied SP survey in the Saijo Plain of western Japan, to determine the shape and the elevation of the water table and to investigate the response of SP along with the presence or the absence of an aquiclude separating a confined to an unconfined aquifer in the Saijo Plain by comparing the SP distributions with hydrological information. SP profiling was carried out using a pair of Cu-CuSO4 electrodes in June (before the rainy season), July (after the rainy season) and October (after the rice harvest) 2009, crossing the plain from the mountainous recharge area in the south to the discharge area near the coast in the north. An inversion technique (Revil, 2004) was applied to estimate groundwater table elevation by observed SP data. We obtained a contrasting trend between the two observation campaigns (June and July). This difference can be related to the variation of water table during these two periods. Also, the distribution of water table estimated using SP values and observed one by the confined monitoring wells showed a good agreement in the eastern part of the study area, whereas there was a disagreement in the western part. These characteristics might be caused by the interaction between confined and unconfined groundwater in the eastern part of the artesian zone. The large increase of SP detected at the northern end of a profile crossing the eastern part of the artesian zone is possibly linked with an upward flow of fresh groundwater, which seems to have been induced by seawater intrusion along the coast. In order to estimate the effectiveness of SP survey, numerical calculations for SP with a program for 3D DC resistivity survey were performed based on water flow distribution and hydrogeologic parameters. Results showed a good correlation between simulated SP and observed one. Reference: Revil, A., Naudet, V., and Meunier, J.D. (2004): The hydroelectric problem of porous rocks: inversion of the position of the water table from self-potential data. Geophys. J. Int. 159, 435-444.

  4. Groundwater flow in a relatively old oceanic volcanic island: the Betancuria area, Fuerteventura Island, Canary Islands, Spain.

    PubMed

    Herrera, Christian; Custodio, Emilio

    2014-10-15

    The island of Fuerteventura is the oldest of the Canary Islands' volcanic archipelago. It is constituted by volcanic submarine and subaerial activity and intrusive Miocene events, with some residual later volcanism and Quaternary volcanic deposits that have favored groundwater recharge. The climate is arid, with an average rainfall that barely attains 60 mm/year in the coast and up to 200 mm/year in the highlands. The aquifer recharge is small but significant; it is brackish due to large airborne atmospheric salinity, between 7 and 15 gm(-2)year(-1) of chloride deposition, and high evapo-concentration in the soil. The average recharge is estimated to be less than about 5 mm/year at low altitude and up to 10 mm/year in the highlands, and up to 20 mm/year associated to recent lava fields. Hydrochemical and water isotopic studies, supported by water table data and well and borehole descriptions, contribute a preliminary conceptual model of groundwater flow and water origin in the Betancuria area, the central area of the island. In general, water from springs and shallow wells tends to be naturally brackish and of recent origin. Deep saline groundwater is found and is explained as remnants of very old marine water trapped in isolated features in the very low permeability intrusive rocks. Preliminary radiocarbon dating indicates that this deep groundwater has an apparent age of less than 5000 years BP but it is the result of mixing recent water recharge with very old deep groundwater. Most of the groundwater flow occurs through the old raised volcanic shield of submarine and subaerial formations and later Miocene subaerial basalts. Groundwater transit time through the unsaturated zone is of a few decades, which allows the consideration of long-term quasi-steady state recharge. Transit times are up to a few centuries through the saturated old volcanics and up to several millennia in the intrusive formations, where isolated pockets of very old water may exist. PMID:25108255

  5. Unsaturated Groundwater Flow Beneath Upper Mortandad Canyon, Los Alamos, New Mexico

    SciTech Connect

    Dander, D.C.

    1998-10-15

    Mortandad Canyon is a discharge site for treated industrial effluents containing radionuclides and other chemicals at Los Alamos National Laboratory, New Mexico. This study was conducted to develop an understanding of the unsaturated hydrologic behavior below the canyon floor. The main goal of this study was to evaluate the hypothetical performance of the vadose zone above the water table. Numerical simulations of unsaturated groundwater flow at the site were conducted using the Finite Element Heat and Mass Transfer (FEHM) code. A two-dimensional cross-section along the canyon's axis was used to model flow between an alluvial groundwater system and the regional aquifer approximately 300 m below. Using recharge estimated from a water budget developed in 1967, the simulations showed waters from the perched water table reaching the regional aquifer in 13.8 years, much faster than previously thought. Additionally, simulations indicate that saturation is occurring in the Guaje pumice bed an d that the Tshirege Unit 1B is near saturation. Lithologic boundaries between the eight materials play an important role in flow and solute transport within the system. Horizontal flow is shown to occur in three thin zones above capillary barriers; however, vertical flow dominates the system. Other simulations were conducted to examine the effects of changing system parameters such as varying recharge inputs, varying the distribution of recharge, and bypassing fast-path fractured basalt of uncertain extent and properties. System sensitivity was also explored by changing model parameters with respect to size and types of grids and domains, and the presence of dipping stratigraphy.

  6. Hyporheic transport and biogeochemical reactions in pool-riffle systems under varying ambient groundwater flow conditions

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Vieweg, Michael; Maier, Uli; Fleckenstein, Jan H.

    2014-05-01

    At the interface between stream water, groundwater, and the hyporheic zone (HZ), important biogeochemical processes that play a crucial role in fluvial ecology occur. Solutes that infiltrate into the HZ can react with each other and possibly also with upwelling solutes from the groundwater. In this study, we systematically evaluate how variations of gaining and losing conditions, stream discharge, and pool-riffle morphology affect aerobic respiration (AR) and denitrification (DN) in the HZ. For this purpose, a computational fluid dynamics model of stream water flow is coupled to a reactive transport model. Scenarios of variations of the solute concentration in the upwelling groundwater were conducted. Our results show that solute influx, residence time, and the size of reactive zones strongly depend on presence, magnitude, and direction of ambient groundwater flow. High magnitudes of ambient groundwater flow lower AR efficiency by up to 4 times and DN by up to 3 orders of magnitude, compared to neutral conditions. The influence of stream discharge and morphology on the efficiency of AR and DN are minor, in comparison to that of ambient groundwater flow. Different scenarios of O2 and NO3 concentrations in the upwelling groundwater reveal that DN efficiency of the HZ is highest under low upwelling magnitudes accompanied with low concentrations of O2 and NO3. Our results demonstrate how ambient groundwater flow influences solute transport, AR, and DN in the HZ. Neglecting groundwater flow in stream-groundwater interactions would lead to a significant overestimation of the efficiency of biogeochemical reactions in fluvial systems.

  7. Deflated CG Method for Modelling Groundwater Flow in a Layered Grid

    E-print Network

    Vuik, Kees

    Deflated CG Method for Modelling Groundwater Flow in a Layered Grid Master's Thesis L.A. Ros Delft and market parties. The institute is located in two cities: Delft and Utrecht. From September 2007 till July 2008 I have been working on a groundwater model for Limburg called IBRAHYM, developed by the former TNO

  8. COMSOL Modeling of Groundwater Flow and Contaminant Transport in Two-Dimensional Geometries With Heterogeneities

    E-print Network

    Gobbert, Matthias K.

    COMSOL Modeling of Groundwater Flow and Contaminant Transport in Two-Dimensional Geometries is located on the East Coast of the United States, between the Chesapeake Bay and Atlantic Ocean. Industrial% of a streams nitrogen load has been discharged from groundwater. The surficial aquifer geometry in this area

  9. A novel approach for direct estimation of fresh groundwater discharge to an estuary

    USGS Publications Warehouse

    Ganju, Neil K.

    2011-01-01

    Coastal groundwater discharge is an important source of freshwater and nutrients to coastal and estuarine systems. Directly quantifying the spatially integrated discharge of fresh groundwater over a coastline is difficult due to spatial variability and limited observational methods. In this study, I applied a novel approach to estimate net freshwater discharge from a groundwater-fed tidal creek over a spring-neap cycle, with high temporal resolution. Acoustic velocity instruments measured tidal water fluxes while other sensors measured vertical and lateral salinity to estimate cross-sectionally averaged salinity. These measurements were used in a time-dependent version of Knudsen's salt balance calculation to estimate the fresh groundwater contribution to the tidal creek. The time-series of fresh groundwater discharge shows the dependence of fresh groundwater discharge on tidal pumping, and the large difference between monthly mean discharge and instantaneous discharge over shorter timescales. The approach developed here can be implemented over timescales from days to years, in any size estuary with dominant groundwater inputs and well-defined cross-sections. The approach also directly links delivery of groundwater from the watershed with fluxes to the coastal environment. Copyright. Published in 2011 by the American Geophysical Union.

  10. Structural control of groundwater flow regimes and groundwater chemistry along the lower reaches of the Zerka River, West Jordan, using remote sensing, GIS, and field methods

    NASA Astrophysics Data System (ADS)

    Odeh, Taleb; Salameh, Elias; Schirmer, Mario; Strauch, Gerhard

    2009-10-01

    A hydrogeological study was completed within a sub-catchment of the Zerka River drainage basin, in western Jordan. The system is characterized by anticlinal bending with an axis trending SSW-NNE and plunging a few degrees in the SSW direction. The anticlinal structure diverts groundwater flow towards the SSW while the strike-slipe faults cause the groundwater to diverge where the fault is perpendicular to the groundwater flow lines, and to converge where the fault is parallel to the groundwater flow lines. A direct relationship was found between the location of springs and the type of groundwater flow with regard to the amount of discharge wherein large spring discharges are located in zones of converging groundwater flow lines. In areas where faults are not abundant, the groundwater retention time in the aquifers is long and a zonation of the electrical conductivity was detected due to mineral dissolution. By controlling groundwater flow, the anticlinal setting produces three genetic groups of groundwater flow systems: (1) alkaline-earth alkaline water which is predominately a bicarbonate-type composition, (2) alkaline-earth alkaline water which is predominately bicarbonate-sulfate, and (3) alkaline-earth alkaline water with a high alkaline component.

  11. Ground-water levels in water year 1987 and estimated ground-water pumpage in water years 1986-87, Carson Valley, Douglas County, Nevada

    USGS Publications Warehouse

    Berger, D.L.

    1990-01-01

    Groundwater levels were measured at 58 wells during water year 1987 and a summary of estimated pumpage is given for water years 1986 and 1987 in Carson Valley, Douglas County, Nevada. The data were collected to provide a record of groundwater changes over the long-term and pumpage estimates that can be incorporated into an existing groundwater model. The estimated total pumpage in water year 1986 was 10,200 acre-ft and in water year 1987 was 13,400 acre-ft. Groundwater levels exhibited seasonal fluctuations but remained relatively stable over the reporting period throughout most of the valley. (USGS)

  12. Estimation of Male Gene Flow: Use Caution.

    PubMed

    Hedrick, Philip W; Singh, Sujeet; Aspi, Jouni

    2015-01-01

    Because male gene flow cannot easily be estimated directly in many organisms, Hedrick et al. (2013) provided an approach to estimate male gene flow given estimates of diploid nuclear and female differentiation. This approach appears to work well when there is lower female than male gene flow. However, in a tiger data set there was less female differentiation observed as estimated by mitochondrial DNA than expected given the observed overall nuclear diploid differentiation. To analyze these data, we suggest an alternative approach which allows incorporation of sex-specific gene flow and sex-specific effective population size. We find that the pattern of differentiation observed in tigers was consistent with a lower male than female effective population size using this alternative approach. Further, this finding is consistent with observed data in tigers where the male effective population size was 33% that of the female effective population size. PMID:26464090

  13. Hydrogeology and simulation of ground-water flow at Arnold Air Force Base, Coffee and Franklin counties, Tennessee

    USGS Publications Warehouse

    Haugh, C.J.; Mahoney, E.N.

    1994-01-01

    The U.S. Air Force at Arnold Air Force Base (AAFB), in Coffee and Franklin Counties, Tennessee, is investigating ground-water contamination in selected areas of the base. This report documents the results of a comprehensive investigation of the regional hydrogeology of the AAFB area. Three aquifers within the Highland Rim aquifer system, the shallow aquifer, the Manchester aquifer, and the Fort Payne aquifer, have been identified in the study area. Of these, the Manchester aquifer is the primary source of water for domestic use. Drilling and water- quality data indicate that the Chattanooga Shale is an effective confining unit, isolating the Highland Rim aquifer system from the deeper, upper Central Basin aquifer system. A regional ground-water divide, approximately coinciding with the Duck River-Elk River drainage divide, underlies AAFB and runs from southwest to northeast. The general direction of most ground-water flow is to the north- west or to the northwest or to the southeast from the divide towards tributary streams that drain the area. Recharge estimates range from 4 to 11 inches per year. Digital computer modeling was used to simulate and provide a better understanding of the ground-water flow system. The model indicates that most of the ground-water flow occurs in the shallow and Manchester aquifers. The model was most sensitive to increases in hydraulic conductivity and changes in recharge rates. Particle-tracking analysis from selected sites of ground-water contamination indicates a potential for contami- nants to be transported beyond the boundary of AAFB.

  14. Hydrology and simulation of ground-water flow in Cedar Valley, Iron County, Utah

    USGS Publications Warehouse

    Brooks, Lynette E.; Mason, James L.

    2005-01-01

    Cedar Valley, located in the eastern part of Iron County in southwestern Utah, is experiencing rapid population growth. Cedar Valley traditionally has supported agriculture, but the growing population needs a larger share of the available water resources. Water withdrawn from the unconsolidated basin fill is the primary source for public supply and is a major source of water for irrigation. Water managers are concerned about increasing demands on the water supply and need hydrologic information to manage this limited water resource and minimize flow of water unsuitable for domestic use toward present and future public-supply sources. Surface water in the study area is derived primarily from snowmelt at higher altitudes east of the study area or from occasional large thunderstorms during the summer. Coal Creek, a perennial stream with an average annual discharge of 24,200 acre-feet per year, is the largest stream in Cedar Valley. Typically, all of the water in Coal Creek is diverted for irrigation during the summer months. All surface water is consumed within the basin by irrigated crops, evapotranspiration, or recharge to the ground-water system. Ground water in Cedar Valley generally moves from primary recharge areas along the eastern margin of the basin where Coal Creek enters, to areas of discharge or subsurface outflow. Recharge to the unconsolidated basin-fill aquifer is by seepage of unconsumed irrigation water, streams, direct precipitation on the unconsolidated basin fill, and subsurface inflow from consolidated rock and Parowan Valley and is estimated to be about 42,000 acre-feet per year. Stable-isotope data indicate that recharge is primarily from winter precipitation. The chloride mass-balance method indicates that recharge may be less than 42,000 acre-feet per year, but is considered a rough approximation because of limited chloride concentration data for precipitation and Coal Creek. Continued declining water levels indicate that recharge is not sufficient to meet demand. Water levels in many areas are at or close to historic lows. In 2000, withdrawal from wells was estimated to be 36,000 acre-feet per year. About 4,000 acre-feet per year are estimated to discharge to evapotranspiration or as subsurface outflow. Prior to large-scale ground-water development, ground-water discharge by evapotranspiration and discharge to springs was much larger. Ground water along the eastern margin of the valley between Cedar City and Enoch is unsuitable for domestic use because of high dissolved-solids and nitrate concentrations. The predominant ions of Ca and SO4 in this area indicate dissolution of gypsum in the Markagunt Plateau to the east. Data collected during this study were compared to historic data; there is no evidence to indicate deterioration in ground-water quality. The spatial distribution of ground water with high nitrate concentration does not appear to be migrating beyond its previously known extent. No single source can be identified as the cause for elevated nitrate concentrations in ground water. Low nitrogen-15 values north of Cedar City indicate a natural geologic source. Higher nitrogen-15 values toward the center of the basin and associated hydrologic data indicate probable recharge from waste-water effluent. Excess dissolved nitrogen gas and low nitrate concentrations in shallow ground water indicate that denitrification is occurring in some areas. A computer ground-water flow model was developed to simulate flow in the unconsolidated basin fill. The method of determining recharge from irrigation was changed during the calibration process to incorporate more areal and temporal variability. In general, the model accurately simulates water levels and water-level fluctuations and can be considered an adequate tool to help determine the valley-wide effects on water levels of additional ground-water withdrawals and changes in water use. The model was used to simulated water-level changes cau

  15. Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution

    NASA Astrophysics Data System (ADS)

    Long, Andrew J.; Putnam, Larry D.

    2009-10-01

    SummaryConvolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers. The framework of a quasi-transient convolution model that is applicable to two-domain flow in karst aquifers is presented. The model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon (CFC) and tritium ( 3H) data are available. We show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined. As an example, the model was applied to water from a pumped well open to the Madison aquifer in central USA with input functions of CFC-11, CFC-12, CFC-113, and 3H, and was calibrated to several samples collected during a 16-year period. A bimodal age distribution was modeled to represent quick and slow flow less than 50 years old. The effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow. Quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0-2 and 26-41 years, respectively. The fraction of long-term flow (>50 years) was estimated but was not dateable. The different tracers had different degrees of influence on parameter estimation and uncertainty assessments, where 3H was the most critical, and CFC-113 was least influential.

  16. Age-distribution estimation for karst groundwater: Issues of parameterization and complexity in inverse modeling by convolution

    USGS Publications Warehouse

    Long, A.J.; Putnam, L.D.

    2009-01-01

    Convolution modeling is useful for investigating the temporal distribution of groundwater age based on environmental tracers. The framework of a quasi-transient convolution model that is applicable to two-domain flow in karst aquifers is presented. The model was designed to provide an acceptable level of statistical confidence in parameter estimates when only chlorofluorocarbon (CFC) and tritium (3H) data are available. We show how inverse modeling and uncertainty assessment can be used to constrain model parameterization to a level warranted by available data while allowing major aspects of the flow system to be examined. As an example, the model was applied to water from a pumped well open to the Madison aquifer in central USA with input functions of CFC-11, CFC-12, CFC-113, and 3H, and was calibrated to several samples collected during a 16-year period. A bimodal age distribution was modeled to represent quick and slow flow less than 50 years old. The effects of pumping and hydraulic head on the relative volumetric fractions of these domains were found to be influential factors for transient flow. Quick flow and slow flow were estimated to be distributed mainly within the age ranges of 0-2 and 26-41 years, respectively. The fraction of long-term flow (>50 years) was estimated but was not dateable. The different tracers had different degrees of influence on parameter estimation and uncertainty assessments, where 3H was the most critical, and CFC-113 was least influential.

  17. Ground-water levels in water years 1984-86 and estimated ground-water pumpage in water years 1984-85, Carson Valley, Douglas County, Nevada

    USGS Publications Warehouse

    Berger, D.L.

    1987-01-01

    Tabulations of groundwater level measurements made during the water years 1984-86 and summaries of estimated pumpage for water years 1984 and 1985 in Carson valley, Douglas County, Nevada, are included in this report. The data are being collected to provide a record of long-term groundwater changes and pumpage estimates that can be incorporated in a groundwater model change at a later date. (USGS)

  18. Groundwater-flow modeling in the Yucatan karstic aquifer, Mexico

    NASA Astrophysics Data System (ADS)

    González-Herrera, Roger; Sánchez-y-Pinto, Ismael; Gamboa-Vargas, José

    2002-09-01

    The current conceptual model of the unconfined karstic aquifer in the Yucatan Peninsula, Mexico, is that a fresh-water lens floats above denser saline water that penetrates more than 40 km inland. The transmissivity of the aquifer is very high so the hydraulic gradient is very low, ranging from 7-10 mm/km through most of the northern part of the peninsula. The computer modeling program AQUIFER was used to investigate the regional groundwater flow in the aquifer. The karstified zone was modeled using the assumption that it acts hydraulically similar to a granular, porous medium. As part of the calibration, the following hypotheses were tested: (1) karstic features play an important role in the groundwater-flow system; (2) a ring or belt of sinkholes in the area is a manifestation of a zone of high transmissivity that facilitates the channeling of groundwater toward the Gulf of Mexico; and (3) the geologic features in the southern part of Yucatan influence the groundwater-flow system. The model shows that the Sierrita de Ticul fault, in the southwestern part of the study area, acts as a flow barrier and head values decline toward the northeast. The modeling also shows that the regional flow-system dynamics have not been altered despite the large number of pumping wells because the volume of water pumped is small compared with the volume of recharge, and the well-developed karst system of the region has a very high hydraulic conductivity. Résumé. Le modèle conceptuel classique de l'aquifère karstique libre de la péninsule du Yucatan (Mexique) consiste en une lentille d'eau douce flottant sur une eau salée plus dense qui pénètre à plus de 40 km à l'intérieur des terres. La transmissivité de l'aquifère est très élevée, en sorte que le gradient hydraulique est très faible, compris entre 7 et 10 mm/km dans la plus grande partie du nord de la péninsule. Le modèle AQUIFER a été utilisé pour explorer les écoulements souterrains régionaux dans cet aquifère. La zone karstifiée a été modélisée en posant l'hypothèse qu'il fonctionne hydrauliquement comme un milieu poreux granulaire. Au cours de la calibration, les hypothèses suivantes ont été testées: (1) les phénomènes karstiques jouent un rôle important dans le système aquifère, (2) un anneau ou une ceinture de dépressions dans la région est la manifestation d'une zone à forte transmissivité qui permet l'écoulement en conduits de l'eau souterraine en direction du Golfe du Mexique, et (3) la situation géologique dans la partie sud du Yucatan détermine les écoulements souterrains. Le modèle montre que la faille de la Sierrita de Ticul, dans la partie sud-ouest de la région étudiée, joue le rôle de barrière et que les valeurs de la piézométrie décroissent en direction du nord-est. La modélisation montre également que la dynamique du système aquifère à l'échelle régionale n'a pas été modifiée malgré le grand nombre de puits de pompage, parce que le volume pompé est faible en comparaison du volume de recharge; en outre, le réseau karstique très bien développé dans cette région possède une très forte conductivité hydraulique. Resumen. El modelo conceptual actual del acuífero cárstico no confinado de la Península de Yucatán (México) es el de un lentejón de agua dulce flotando sobre agua salada, más densa, la cual penetra más de 40 kilómetros tierra adentro. Debido a la alta conductividad hidráulica del acuífero, existe un gradiente hidráulico muy bajo cuyo rango está entre 7 y 10 milímetros por kilómetro en la porción norte de la península. Se utilizó el código AQUIFER para investigar el sistema de flujo de las aguas subterráneas a escala regional en el acuífero. La zona carstificada se modeló suponiendo que actúa hidráulicamente como un medio poroso granular. Como parte de la calibración, se probaron las siguientes hipótesis: (1) las características cársticas desempeñan un papel importante en el sistema de flujo de agua subterránea (2) un anillo o cinturón de sumideros en el área e

  19. Controls on groundwater flow in the Bengal Basin of India and Bangladesh: Regional modeling analysis

    USGS Publications Warehouse

    Michael, H.A.; Voss, C.I.

    2009-01-01

    Groundwater for domestic and irrigation purposes is produced primarily from shallow parts of the Bengal Basin aquifer system (India and Bangladesh), which contains high concentrations of dissolved arsenic (exceeding worldwide drinking water standards), though deeper groundwater is generally low in arsenic. An essential first step for determining sustainable management of the deep groundwater resource is identification of hydrogeologic controls on flow and quantification of basin-scale groundwater flow patterns. Results from groundwater modeling, in which the Bengal Basin aquifer system is represented as a single aquifer with higher horizontal than vertical hydraulic conductivity, indicate that this anisotropy is the primary hydrogeologic control on the natural flowpath lengths. Despite extremely low hydraulic gradients due to minimal topographic relief, anisotropy implies large-scale (tens to hundreds of kilometers) flow at depth. Other hydrogeologic factors, including lateral and vertical changes in hydraulic conductivity, have minor effects on overall flow patterns. However, because natural hydraulic gradients are low, the impact of pumping on groundwater flow is overwhelming; modeling indicates that pumping has substantially changed the shallow groundwater budget and flowpaths from predevelopment conditions. ?? Springer-Verlag 2009.

  20. Evolution of 3-D geologic framework modeling and its application to groundwater flow studies

    USGS Publications Warehouse

    Blome, Charles D.; Smith, David V.

    2012-01-01

    In this Fact Sheet, the authors discuss the evolution of project 3-D subsurface framework modeling, research in hydrostratigraphy and airborne geophysics, and methodologies used to link geologic and groundwater flow models.

  1. AN INTEGRATED VIEW OF GROUNDWATER FLOW CHARACTERIZATION AND MODELING IN FRACTURED GEOLOGIC MEDIA

    EPA Science Inventory

    The particular attributes of fractured geologic media pertaining to groundwater flow characterization and modeling are presented. These cover the issues of fracture network and hydraulic control of fracture geometry parameters, major and minor fractures, heterogeneity, anisotrop...

  2. Conceptual evaluation of regional ground-water flow in the carbonate-rock province of the Great Basin, Nevada, Utah, and adjacent states

    USGS Publications Warehouse

    Prudic, D.E.; Harrill, J.R.; Burbey, T.J.

    1993-01-01

    The regional groundwater flow system in the carbonate rocks of Nevada and Utah is conceptualized as shallow systems superimposed on deeper systems, which transmit water primarily through carbonate rocks. A computer model was used to simulate the two systems. The regional model includes simplifying assumptions that are probably valid for parts of the province; however, the validity of each assumption is unknown for the province as a whole. Therefore, simulation results do not perfectly replicate actual groundwater flow; instead they provide a conceptual evaluation of regional groundwater flow. The model was calibrated by adjusting transmissivity and vertical leakance until simulated water levels and simulated discharge generally agreed with known water levels, mapped areas of discharge, and estimates of discharge. Simulated flow is about 1.5 million acre-ft/yr. Most groundwater flow is simulated in the upper model layer where about 45 shallow flow regions were identified. In the lower layer, 17 deep-flow subregions were identified and grouped into 5 large regions on the basis of water-flow patterns. Simulated flow in this layer is about 28 percent of the total inflow and about half is discharged as springflow. Interbasin flow to several large springs is through thick, continuous, permeable carbonate rocks; elsewhere deep consolidated rocks are not highly transmissive, suggesting that carbonate rocks are not highly permeable everywhere or are not present everywhere. (USGS)

  3. Ground-water conditions in Las Vegas Valley, Clark County, Nevada; Part II, Hydrogeology and simulation of ground-water flow

    USGS Publications Warehouse

    Morgan, D.S.; Dettinger, M.D.

    1994-01-01

    Groundwater withdrawals in Las Vegas Valley, Nevada, primarily for municipal supplies, totaled more than 2.5 million acre-ft between 1912 and 1981, with a peak annual withdrawal rate of 88,000 acre-ft in 1968. Effects of heavy pumping are evident over large areas of the valley but are more pronounced near the major well fields. Secondary recharge from lawn irrigation and other sources is estimated to have totaled more than 340,000 acre-ft during 1972-81. Resulting rises in water-level in shallow, unconfined aquifers in the central and southeastern parts of the valley have caused: widespread water-logging of soils; increased groundwater discharge to Las Vegas Wash and its tributaries; and potential for degradation of water quality in deeper aquifers by accentuating downward vertical hydraulic potential in areas where shallow groundwater has high concentrations of dissolved solids and nitrate. A 3-dimensional groundwater flow model of the valley-fill aquifer system was constructed for use in evaluating possible groundwater management alternatives aimed at alleviating problems related to overdraft and water-logging while maximizing use of the groundwater resources. Natural recharge to the valley-fill aquifers is about 33,000 acre-ft/yr; in 1979, an estimated 44,000 acre-ft of secondary recharge infiltrated to the near-surface and developed-zone aquifers. Peak water use for lawn irrigation during summer results in rates of secondary recharge that may increase threefold from winter rates. Simulated rates of seepage to washes in the valley increased correspondingly from an average of 850 acre-ft/mo in winter to about 1,300 acre-ft/mo in the summer. Groundwater withdrawals by pumping totaled 620,000 acre-ft during 1972-81, and model results indicate that about 190,000 acre-ft of that total was derived from storage. Use of the model as a predictive tool was demonstrated by simulating the effects of using most municipal wells only during the peak-demand season of June 1 through September 20. Results of the 9-year simulation indicated that: (1) long-term rates of water-level decline near the municipal well field would be less than rates for 1972-81, but the magnitude of seasonal fluctuations would increase, and (2) total volume of water released from storage as a result of subsidence would be only 42,000 acre-feet per year, or about half the volume during 1972-81.

  4. Rapid intrusion of magma into wet rock: groundwater flow due to pore pressure increases.

    USGS Publications Warehouse

    Delaney, P.T.

    1982-01-01

    Analytical and numerical solutions are developed to simulate the pressurization, expansion, and flow of groundwater contained within saturated, intact host rocks subject to sudden heating from the planar surface of an igneous intrusion. For most rocks, water diffuses more rapidly than heat, assuring that groundwater is not heated along a constant-volume pressure path and that thermal expansion and pressurization adjacent to the intrusion drives a flow that extends well beyond the heated region. -from Author

  5. Evaluation of uncertainties due to hydrogeological modeling and groundwater flow analysis: Steady flow, transient flow, and thermal studies

    SciTech Connect

    Doughty, Christine; Karasaki, Kenzi

    2002-12-11

    Starting with regional geographic, geologic, surface and subsurface hydrologic, and geophysical data for the Tono area in Gifu, Japan, we develop an effective continuum model to simulate subsurface flow and transport in a 4 km by 6 km by 3 km thick fractured granite rock mass overlain by sedimentary layers. Individual fractures are not modeled explicitly. Rather, continuum permeability and porosity distributions are assigned stochastically, based on well-test data and fracture density measurements. Lithologic layering and one major fault, the Tsukiyoshi Fault, are assigned deterministically. We conduct three different studies: (1) the so-called base case, in which the model simulates the steady-state groundwater flow through the site, and then stream trace analysis is used to calculate travel times to the model boundary from specified release points; (2) simulations of transient flow during long term pump tests (LTPT) using the base-case model; and (3) thermal studies in which coupled heat flow and fluid flow are modeled, to examine the effects of the geothermal gradient on groundwater flow. The base-case study indicates that the choice of open or closed lateral boundaries has a strong influence on the regional groundwater flow patterns produced by the models, but no field data exist that can be used to determine which boundary conditions are more realistic. The LTPT study cannot be used to distinguish between the alternative boundary conditions, because the pumping rate is too small to produce an analyzable pressure response at the model boundaries. In contrast, the thermal study shows that the temperature distributions produced by the open and closed models differ greatly. Comparison with borehole temperature data may be used to eliminate the closed model from further consideration.

  6. Satellite-based estimates of groundwater depletion in India.

    PubMed

    Rodell, Matthew; Velicogna, Isabella; Famiglietti, James S

    2009-08-20

    Groundwater is a primary source of fresh water in many parts of the world. Some regions are becoming overly dependent on it, consuming groundwater faster than it is naturally replenished and causing water tables to decline unremittingly. Indirect evidence suggests that this is the case in northwest India, but there has been no regional assessment of the rate of groundwater depletion. Here we use terrestrial water storage-change observations from the NASA Gravity Recovery and Climate Experiment satellites and simulated soil-water variations from a data-integrating hydrological modelling system to show that groundwater is being depleted at a mean rate of 4.0 +/- 1.0 cm yr(-1) equivalent height of water (17.7 +/- 4.5 km(3) yr(-1)) over the Indian states of Rajasthan, Punjab and Haryana (including Delhi). During our study period of August 2002 to October 2008, groundwater depletion was equivalent to a net loss of 109 km(3) of water, which is double the capacity of India's largest surface-water reservoir. Annual rainfall was close to normal throughout the period and we demonstrate that the other terrestrial water storage components (soil moisture, surface waters, snow, glaciers and biomass) did not contribute significantly to the observed decline in total water levels. Although our observational record is brief, the available evidence suggests that unsustainable consumption of groundwater for irrigation and other anthropogenic uses is likely to be the cause. If measures are not taken soon to ensure sustainable groundwater usage, the consequences for the 114,000,000 residents of the region may include a reduction of agricultural output and shortages of potable water, leading to extensive socioeconomic stresses. PMID:19675570

  7. Rapid exchange effects on isotope ratios in groundwater systems: 2. Flow investigation using Sr isotope ratios

    NASA Astrophysics Data System (ADS)

    Johnson, Thomas M.; Depaolo, Donald J.

    1997-01-01

    Sr isotope ratios were measured in groundwater, whole rock digestions, and cation exchange extracts from a clay-rich groundwater system at Ernest O. Lawrence Berkeley National Laboratory and were used to constrain flow velocities and search for preferential flow paths. In the Orinda formation siltstone, 87Sr/86Sr increases strongly over tens of meters along presumed flow paths, indicating slow groundwater flow. Dissolved Sr is close to isotopic equilibrium with the exchangeable Sr in the clays, and the observed 87Sr/86Sr increase is interpreted as a cation exchange front moving slowly through the unit combined with dissolution of minerals with relatively high 87Sr/86Sr ratios. The data are inverted using a one-dimensional transport-dissolution-exchange model; the results indicate long-term average flow velocities of less than 0.2 m/yr which are consistent with 14C measurements. The data suggest a lack of strong preferential flow paths through this unit.

  8. Using MODFLOW drains to simulate groundwater flow in a karst environment

    SciTech Connect

    Quinn, J.; Tomasko, D.; Glennon, M.A.; Miller, S.F.; McGinnis, L.D.

    1998-07-01

    Modeling groundwater flow in a karst environment is both numerically challenging and highly uncertain because of potentially complex flowpaths and a lack of site-specific information. This study presents the results of MODFLOW numerical modeling in which drain cells in a finite-difference model are used as analogs for preferential flowpaths or conduits in karst environments. In this study, conduits in mixed-flow systems are simulated by assigning connected pathways of drain cells from the locations of tracer releases, sinkholes, or other karst features to outlet springs along inferred flowpaths. These paths are determined by the locations of losing stream segments, ephemeral stream beds, geophysical surveys, fracture lineaments, or other surficial characteristics, combined with the results of dye traces. The elevations of the drains at the discharge ends of the inferred flowpaths are estimated from field data and are adjusted when necessary during model calibration. To simulate flow in a free-flowing conduit, a high conductance is assigned to each drain to eliminate the need for drain-specific information that would be very difficult to obtain. Calculations were performed for a site near Hohenfels, Germany. The potentiometric surface produced by the simulations agreed well with field data. The head contours in the vicinity of the karst features behaved in a manner consistent with a flow system having both diffuse and conduit components, and the sum of the volumetric flow out of the drain cells agreed closely with spring discharges and stream flows. Because of the success of this approach, it is recommended for regional studies in which little site-specific information (e.g., location, number, size, and conductivity of fractures and conduits) is available, and general flow characteristics are desired.

  9. Soil and Groundwater Sampling

    USGS Multimedia Gallery

    Groundwater sampling setup at EAFB FAC MW14_04 Fuels Area C, Ellsworth Air Force Base, South Dakota. In fall of 2013, the U.S. Geological Survey began a study in cooperation with the U.S. Air Force, Ellsworth Air Force Base, to estimate groundwater-flow direction, select locations for permanent moni...

  10. Density-Thermal-Driven Groundwater Flow and Brine Transport Near Salt Domes

    NASA Astrophysics Data System (ADS)

    Jamshidzadeh, Z.; Tsai, F. T.; Mirbagheri, S.; Ghasemzadeh, H.

    2012-12-01

    A major environmental and economic concern in many parts of the world is progressive salinization of groundwater system. Therefore, understanding the sources and flow patterns of encroachment of saline or brine water into freshwater aquifers is necessary for groundwater resources management. Flow patterns near salt domes in deep formation is of interest in this study because of complexity of different driving forces from salt concentration, thermal, and fluid pressure gradients. Because of rock formation and relative high temperature in the vicinity of salt domes, fluid salinity is much higher than seawater and density variation in the brine waters exceeds 20% with respect to fresh water. Groundwater flow, salt transport and heat transport equations are strongly coupled. Moreover, it is necessary to include the dispersive flux of total fluid mass in the flow equation. In this study, a two-dimensional density-thermal-driven groundwater flow induced by salt mass fraction gradient and temperature gradient near a hypothetical salt dome is considered. A fully implicit finite difference method has been developed to solve three coupled governing equations. The classical Elder problems and the Henry problem were used as benchmarks to verify the numerical code for solving the coupled flow and heat equations and the coupled flow and transport equations. Then, the numerical model is applied to a hypothetical salt dome problem to simulate upward density-thermal-driven groundwater flow and brine transport.

  11. Shallow groundwater flow in unmined regions of the northern Appalachian Plateau: Part 2. Geochemical characteristics

    SciTech Connect

    Brady, K.B.C.; DiMatteo, M.R.; Rose, A.W.; Hawkins, J.W.

    1996-12-31

    Surface mines in Pennsylvania occur in the shallow (< 60 m depth) groundwater flow system and typically are located in groundwater recharge areas. Two shallow flow systems are usually present in unmined areas: an upper weathered-rock zone and a deeper unweathered-rock zone. The weathered-rock zone, although variable, is commonly 6 to 12 m thick. Groundwater in the weathered-rock flow system, as evidenced by shallow wells and cropline springs, has low dissolved solids (specific conductance < 50 {mu}S/cm). The deeper unweathered-rock flow system, as evidenced by water from wells deeper than 10 m, has higher concentrations of dissolved constituents. The differences in water quality are due to previous intensive leaching of minerals within the weathered-rock zone and to much higher flow rates in the more porous and fractured weathered zone. In particular, calcareous minerals are absent or negligible in the weathered-rock zone, but can be appreciable in the unweathered-rock zone. This distribution of calcareous minerals, groundwater contact time with rock, and flow path influence the groundwater composition and concentrations of dissolved ions. A positive relationship exists between the presence and abundance of calcareous minerals and associated groundwater alkalinity. Our observations are probably applicable to much of the Appalachian Plateau. Groundwater alkalinity can help determine the presence and distribution of calcareous minerals within coal overburden. Coal-cropline springs should not be depended upon for showing groundwater quality associated with the coal seam; they typically only reflect shallow flow through weathered rock. Deeper wells are required to determine the chemical characteristics of water in the unweathered rock zone.

  12. Estimating the Regional Flux of Nitrate and Agricultural Herbicide Compounds from Groundwater to Headwater Streams of the Northern Atlantic Coastal Plain, USA

    NASA Astrophysics Data System (ADS)

    Ator, S.; Denver, J. M.

    2011-12-01

    Agriculture is common in the Northern Atlantic Coastal Plain (NACP, including New Jersey through North Carolina), and groundwater discharge provides nitrogen (primarily in the form of nitrate) and herbicide compounds from agricultural sources along with the majority of flow to NACP streams. Poor water quality has contributed to ecological degradation of tidal streams and estuaries along much of the adjacent mid-Atlantic coast. Although statistical models have provided estimates of total instream nutrient flux in the Coastal Plain, the regional flux of nitrogen and herbicides during base flow is less well understood. We estimated the regional flux of nitrate and selected commonly used herbicide compounds from groundwater to non-tidal headwater streams of the NACP on the basis of late-winter or spring base-flow samples from 174 such streams. Sampled streams were selected using an unequal-probability random approach, and flux estimates are based on resulting population estimates rather than empirical models, which are commonly used for such estimates. Base-flow flux in the estimated 8,834 NACP non-tidal headwater streams are an estimated 21,200 kilograms per day of nitrate (as N) and 5.83, 0.565, and 20.7 kilograms per day of alachlor, atrazine, and metolachlor (including selected degradates), respectively. Base-flow flux of alachlor and metolachlor is dominated by degradates; flux of parent compounds is less than 3 percent of the total flux of parent plus degradates. Base-flow flux of nitrate and herbicides as a percentage of applications generally varies predictably with regional variations in hydrogeology. Abundant nonpoint (primarily agricultural) sources and hydrogeologic conditions, for example, contribute to particularly large base-flow flux from the Delmarva Peninsula to Chesapeake Bay. In the Delmarva Peninsula part of the Chesapeake Watershed, more than 10 percent of total nonpoint nitrogen applications is transported through groundwater to stream base flow, and base-flow nitrate flux represents 70 percent of total nitrogen flux in streams.

  13. How sampling integration scale affects estimates of coupled groundwater and nitrogen fluxes into an agricultural stream

    NASA Astrophysics Data System (ADS)

    Gilmore, T. E.; Solder, J.; Solomon, K.; Genereux, D. P.; Kimball, B. A.; Burnette, M.; Becker, S.

    2013-12-01

    Coupled fluxes of groundwater and non-point source contaminants from aquifers to streams may be estimated using streambed point (SP) measurements, seepage meter (SM) measurements, or a reach mass-balance approach (RMB), each with different spatial support scales and pros/cons. We have applied all three measurement schemes concurrently in the same stream to assess how sampling integration scale affects estimates of (1) coupled groundwater and dissolved nitrogen fluxes through a streambed and (2) the total amount of denitrification that has occurred along groundwater flowpaths. Our study site was a 2700m reach in West Bear Creek (WBC), a channelized and overall gaining stream in the agricultural Coastal Plain of North Carolina. In a July 2012 sampling campaign, groundwater fluxes through the WBC streambed were similar for the SP and RMB approaches (35 cm/day and 33 cm/day, respectively), despite very different measurement scales and different reach sizes (RMB groundwater flux is based on a 200m stream reach containing the smaller 58m SP reach). However, the RMB approach gave a lower calculated streambed nitrate flux (136 mmol m-2 d-1, versus 231 mmol m-2 d-1 for SP) for the 58m reach. The lower nitrate flux by the RMB approach is linked to a lower mean groundwater nitrate concentration estimated by RMB (361 ?M, vs. 808 ?M for SP). Unlike the SP approach, the RMB approach samples groundwater that has had significant interaction with the stream channel and thus, apparently, nitrate loss from uptake and/or denitrification. The SM approach used novel flexible streambed 'blankets' and gave lower fluxes: 10 cm/day for groundwater (due perhaps to incomplete sampling of streambed variability in this flux or other methodological issues) and 53 mmol m-2 d-1 for nitrate; it also gave an intermediate estimate of nitrate concentration in the groundwater discharge to the stream (527 ?M), likely a reflection of the intermediate amount of channel interaction (collected after passing through the hyporheic zone, but before subsequent channel interaction) for the groundwater sampled by this approach. Noble gas concentrations (Xe, Ar, Ne, Kr) are being used to model the amount of N2 derived from denitrification (N2-den) in the groundwater feeding the stream. Preliminary results from a subset of SP samples (n=9) suggest significant amounts of N2-den because measured groundwater N2 concentration is up to 75% higher than modeled N2 concentration. The three approaches offer different strengths and weaknesses appropriate for answering different questions, and in concert may provide a fuller picture of N fluxes from groundwater to surface water in areas of non-point N pollution.

  14. Microsphere estimates of blood flow: Methodological considerations

    SciTech Connect

    von Ritter, C.; Hinder, R.A.; Womack, W.; Bauerfeind, P.; Fimmel, C.J.; Kvietys, P.R.; Granger, D.N.; Blum, A.L. Louisianna State Univ. Medical Center, Shreveport Universitaire Vaudois )

    1988-02-01

    The microsphere technique is a standard method for measuring blood flow in experimental animals. Sporadic reports have appeared outlining the limitations of this method. In this study the authors have systematically assessed the effect of blood withdrawals for reference sampling, microsphere numbers, and anesthesia on blood flow estimates using radioactive microspheres in dogs. Experiments were performed on 18 conscious and 12 anesthetized dogs. Four blood flow estimates were performed over 120 min using 1 {times} 10{sup 6} microspheres each time. The effects of excessive numbers of microspheres pentobarbital sodium anesthesia, and replacement of volume loss for reference samples with dextran 70 were assessed. In both conscious and anesthetized dogs a progressive decrease in gastric mucosal blood flow and cardiac output was observed over 120 min. This was also observed in the pancreas in conscious dogs. The major factor responsible for these changes was the volume loss due to the reference sample withdrawals. Replacement of the withdrawn blood with dextran 70 led to stable blood flows to all organs. The injection of excessive numbers of microspheres did not modify hemodynamics to a greater extent than did the injection of 4 million microspheres. Anesthesia exerted no influence on blood flow other than raising coronary flow. The authors conclude that although blood flow to the gastric mucosa and the pancreas is sensitive to the minor hemodynamic changes associated with the microsphere technique, replacement of volume loss for reference samples ensures stable blood flow to all organs over a 120-min period.

  15. Geohydrology of the Central Oahu, Hawaii, Ground-Water Flow System and Numerical Simulation of the Effects of Additional Pumping

    USGS Publications Warehouse

    Oki, Delwyn S.

    1998-01-01

    A two-dimensional, finite-difference, ground-water flow model was developed for the central Oahu flow system, which is the largest and most productive ground-water flow system on the island. The model is based on the computer code SHARP which simulates both freshwater and saltwater flow. The ground-water model was developed using average pumping and recharge conditions during the 1950's, which was considered to be a steady-state period. For 1950's conditions, model results indicate that 62 percent (90.1 million gallons per day) of the discharge from the Schofield ground-water area flows southward and the remaining 38 percent (55.2 million gallons per day) of the discharge from Schofield flows northward. Although the contribution of recharge from infiltration of rainfall and irrigation water directly on top of the southern and northern Schofield ground-water dams was included in the model, the distribution of natural discharge from the Schofield ground-water area was estimated exclusive of the recharge on top of the dams. The model was used to investigate the long-term effects of pumping under future land-use conditions. Future recharge was conservatively estimated by assuming no recharge associated with agricultural activities. Future pumpage used in the model was based on the 1995-allocated rates. Model results indicate that the long-term effect of pumping at the 1995-allocated rates will be a reduction of water levels from present (1995) conditions in all ground-water areas of the central Oahu flow system. In the Schofield ground-water area, model results indicate that water levels could decline about 30 feet from the 1995 water-level altitude of about 275 feet. In the remaining ground-water areas of the central Oahu flow system, water levels may decline from less than 1 foot to as much as 12 feet relative to 1995 water levels. Model results indicate that the bottoms of several existing deep wells in northern and southern Oahu extend below the model-calculated freshwater-saltwater interface location for the future recharge and pumping conditions. Model results indicate that an additional 10 million gallons per day (beyond the 1995-allocated rates) of freshwater can potentially be developed from northern Oahu. Various distributions of pumping can be used to obtain the additional 10 million gallons per day of water. The quality of the water pumped will be dependent on site-specific factors and cannot be predicted on the basis of model results. If the additional 10 million gallons per day pumpage is restricted to the Kawailoa and Waialua areas, model results indicate that a regional drawdown (relative to the water-level distribution associated with the 1995-allocated pumping rates) of less than 0.6 foot can be maintained in these two areas. The additional pumping, however, would cause salinity increases in water pumped by existing deep wells. In addition, increases in salinity may occur at other wells in areas where the model indicates no significant problem with upconing.

  16. Groundwater Flow Field Distortion by Monitoring Wells and Passive Flux Meters.

    PubMed

    Verreydt, G; Bronders, J; Van Keer, I; Diels, L; Vanderauwera, P

    2015-11-01

    Due to differences in hydraulic conductivity and effects of well construction geometry, groundwater lateral flow through a monitoring well typically differs from groundwater flow in the surrounding aquifer. These differences must be well understood in order to apply passive measuring techniques, such as passive flux meters (PFMs) used for the measurement of groundwater and contaminant mass fluxes. To understand these differences, lab flow tank experiments were performed to evaluate the influences of the well screen, the surrounding filter pack and the presence of a PFM on the natural groundwater flux through a monitoring well. The results were compared with analytical calculations of flow field distortion based on the potential theory of Drost et al. (1968). Measured well flow field distortion factors were found to be lower than calculated flow field distortion factors, while measured PFM flow field distortion factors were comparable to the calculated ones. However, this latter is not the case for all conditions. The slotted geometry of the well screen seems to make a correct analytical calculation challenging for conditions where flow field deviation occurs, because the potential theory assumes a uniform flow field. Finally, plots of the functional relationships of the distortion of the flow field with the hydraulic conductivities of the filter screen, surrounding filter pack and corresponding radii make it possible to design well construction to optimally function during PFM applications. PMID:25565034

  17. Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge

    USGS Publications Warehouse

    Cuthbert, M.O.; Mackay, R.; Nimmo, J.R.

    2012-01-01

    Results are presented of a detailed study into the vadose zone and shallow water table hydrodynamics of a field site in Shropshire, UK. A conceptual model is developed and tested using a range of numerical models, including a modified soil moisture balance model (SMBM) for estimating groundwater recharge in the presence of both diffuse and preferential flow components. Tensiometry reveals that the loamy sand topsoil wets up via macropore flow and subsequent redistribution of moisture into the soil matrix. Recharge does not occur until near-positive pressures are achieved at the top of the sandy glaciofluvial outwash material that underlies the topsoil, about 1 m above the water table. Once this occurs, very rapid water table rises follow. This threshold behaviour is attributed to the vertical discontinuity in the macropore system due to seasonal ploughing of the topsoil, and a lower permeability plough/iron pan restricting matrix flow between the topsoil and the lower outwash deposits. Although the wetting process in the topsoil is complex, a SMBM is shown to be effective in predicting the initiation of preferential flow from the base of the topsoil into the lower outwash horizon. The rapidity of the response at the water table and a water table rise during the summer period while flow gradients in the unsaturated profile were upward suggest that preferential flow is also occurring within the outwash deposits below the topsoil. A variation of the source-responsive model proposed by Nimmo (2010) is shown to reproduce the observed water table dynamics well in the lower outwash horizon when linked to a SMBM that quantifies the potential recharge from the topsoil. The results reveal new insights into preferential flow processes in cultivated soils and provide a useful and practical approach to accounting for preferential flow in studies of groundwater recharge estimation.

  18. ADAPTATION OF THE CARTER-TRACY WATER INFLUX CALCULATION TO GROUNDWATER FLOW SIMULTATION.

    USGS Publications Warehouse

    Kipp, Kenneth L.

    1986-01-01

    The Carter-Tracy calculation for water influx is adapted to groundwater flow simulation with additional clarifying explanation not present in the original papers. The Van Everdingen and Hurst aquifer-influence functions for radial flow from an outer aquifer region are employed. This technique, based on convolution of unit-step response functions, offers a simple but approximate method for embedding an inner region of groundwater flow simulation within a much larger aquifer region where flow can be treated in an approximate fashion. The use of aquifer-influence functions in groundwater flow modeling reduces the size of the computational grid with a corresponding reduction in computer storage and execution time. The Carter-Tracy approximation to the convolution integral enables the aquifer influence function calculation to be made with an additional storage requirement of only two times the number of boundary nodes more than that required for the inner region simulation.

  19. Groundwater hydrochemical characteristics and processes along flow paths in the North China Plain

    NASA Astrophysics Data System (ADS)

    Xing, Lina; Guo, Huaming; Zhan, Yanhong

    2013-07-01

    The North China Plain is one of the biggest plains in China, where municipal, agricultural and industrial water supplies are highly dependent on groundwater resources. It is crucial to investigate water chemistry and hydrogeochemical processes related to hydrogeologic settings for sustainable utilization of groundwater resources. Two hydrochemical profiles proximately along the groundwater flow paths were selected for hydrogeochemical study. Major components and 2H and 18O isotopes were analyzed in groundwater samples from the profiles. The study area was divided into three zones, including strong runoff-alluvial/pluvial fans in the piedmont area (Zone I), slow runoff-alluvial/lacustrine plain in the central area (Zone II), and discharge-alluvial/marine plain in the coastal area (Zone III). Major components of groundwater samples showed obvious zonation patterns from Zone I to Zone III. Total dissolved solid (TDS) concentrations gradually increased, and the hydrochemical type changed from HCO3-SO4-Ca-Mg and HCO3-Cl-Ca-Mg types to HCO3-SO4-Na-Ca, SO4-Cl-Na-Ca and SO4-Cl-Na types from Zone I to Zone III. Abrupt increases in concentrations of Na+, Cl- and SO42- in deep groundwater were observed around the depression cones, which indicated that overexploitation resulted in water quality deterioration. Calcite and dolomite precipitation occurred in Zone I of deep groundwater systems and shallow groundwater systems. Cation exchange was believed to take place along the entire flow paths. Gypsum tended to dissolve in groundwater systems. The depletion in D and 18O isotopes in deep groundwater was related to the recharge from precipitation in paleo-climate conditions in glacial or interglacial periods, indicating that renewal groundwater was very limited. Efficient strategies must be taken to preserve the valued water resources for sustainable development.

  20. Satellite-based estimates of groundwater depletion Matthew Rodell1

    E-print Network

    Chen, Zhongping

    resources by population growth and economic development, the laws governing groundwater rights have and other anthropogenic uses is likely to be the cause. If measures are not taken soon to ensure sustain not changed accordingly, even in developed nations7 . Nor is ground- water depletion limited to dry climates

  1. Ramification of Channel Networks Incised by Groundwater Flow

    NASA Astrophysics Data System (ADS)

    Yi, R. S.; Seybold, H. F.; Petroff, A. P.; Devauchelle, O.; Rothman, D.

    2011-12-01

    The geometry of channel networks has been a source of fascination since at least Leonardo da Vinci's time. Yet a comprehensive understanding of ramification---the mechanism of branching by which a stream network acquires its geometric complexity---remains elusive. To investigate the mechanisms of ramification and network growth, we consider channel growth driven by groundwater flow as a model system, analogous to a medical scientist's laboratory rat. We test our theoretical predictions through analysis of a particularly compelling example found on the Florida Panhandle north of Bristol. As our ultimate goal is to understand ramification and growth dynamics of the entire network, we build a computational model based on the following growth hypothesis: Channels grow in the direction that captures the maximum water flux. When there are two such directions, tips bifurcate. The direction of growth can be determined from the expansion of the ground water field around each tip, where each coefficient in this expansion has a physical interpretation. The first coefficient in the expansion determines the ground water discharge, leading to a straight growth of the channel. The second term describes the asymmetry in the water field leading to a bending of the stream in the direction of maximal water flux. The ratio between the first and the third coefficient determines a critical distance rc over which the tip feels inhomogeneities in the ground water table. This initiates then the splitting of the tip. In order to test our growth hypothesis and to determine rc, we grow the Florida network backward. At each time step we calculate the solution of the ground water field and determine the appropriate expansion coefficients around each tip. Comparing this simulation result to the predicted values provides us with a stringent measure for rc and the significance of our growth hypothesis.

  2. Analysis of the Shallow Groundwater Flow System at Fire Island National Seashore, Suffolk County, New York

    USGS Publications Warehouse

    Schubert, Christopher E.

    2010-01-01

    Fire Island National Seashore (FIIS) occupies 42 kilometers of the barrier island for which it is named that lies off the southern shore of Suffolk County, N.Y. Freshwater in the highly permeable, sandy aquifer underlying Fire Island is bounded laterally by marine surface waters and at depth by saline groundwater. Interspersed throughout FIIS are 17 pre-existing residential communities that in summer months greatly increase in population through the arrival of summer residents and vacationers; in addition, the National Park Service (NPS) has established several facilities on the island to accommodate visitors to FIIS. The 2.2 million people estimated by the NPS to visit Fire Island annually impact groundwater quality through the release of waste-derived contaminants, such as nutrients, pathogens, and organic compounds, into the environment. Waste-contaminated groundwater can move through the aquifer and threaten the ecological health of the adjacent back-barrier estuaries to which much of the groundwater ultimately discharges. In 2004, the U.S. Geological Survey (USGS), in cooperation with the NPS, began a 3-year investigation to (1) collect groundwater levels and water-quality (nutrient) samples, (2) develop a three-dimensional model of the shallow (water-table) aquifer system and adjacent marine surface waters, and (3) calculate nitrogen loads in simulated groundwater discharges from the aquifer to back-barrier estuaries and the ocean. The hydrogeology of the shallow aquifer system was characterized from the results of exploratory drilling, geophysical surveying, water-level monitoring, and water-quality sampling. The investigation focused on four areas-the communities of Kismet and Robbins Rest, the NPS Visitor Center at Watch Hill, and the undeveloped Otis Pike Fire Island High Dune Wilderness. Thirty-five observation wells were installed within FIIS to characterize subsurface hydrogeology and establish a water-table monitoring network in the four study areas. A variable-density model of the shallow aquifer system and adjacent marine surface waters was developed to simulate groundwater flow patterns and rates. Nitrogen loads from the shallow aquifer system were calculated from representative total nitrogen (TN) concentrations and simulated groundwater discharges to back-barrier estuaries and the ocean. The model simulates groundwater directions, velocities, and discharge rates under 2005 mean annual conditions. Groundwater budgets were developed for recharge areas of similar land use that contribute freshwater to back-barrier estuaries, the ocean, and subsea-discharge zones. Total freshwater discharge from the shallow aquifer system is about 43,500 cubic meters per day (m3/d) (79.8 percent) to back-barrier estuaries and about 10,200 m3/d (18.7 percent) to the ocean; about 836 m3/d (1.5 percent) may exit the system as subsea underflow. The total contribution of fresh groundwater to shoreline discharge zones amounts to about 53,700 m3/d (98.5 percent). The median age of freshwater discharged to back-barrier estuaries and the ocean was 3.4 years, and the 95th-percentile age was 20 years. The TN concentrations and loads under 2005 mean annual conditions for areas that contribute fresh groundwater to back-barrier estuaries and the ocean were calculated for the principal land uses on Fire Island. The overall TN load from the shallow aquifer system to shoreline discharge zones is about 16,200 kilograms per year (kg/yr) (82.2 percent) to back-barrier estuaries and about 3,500 kg/yr (17.8 percent) to the ocean. The overall TN load to marine surface waters amounts to about 19,700 kg/yr-roughly 6 percent of the annual TN load from shallow groundwater entering the South Shore Estuary Reserve (SSER) from the Suffolk County mainland, which is about 345,000 kg/yr. In contrast to the TN load from shallow groundwater for the SSER watershed, which annually yields about 353 kilograms per square kilometer (kg/km2), the overall TN loa

  3. Environmental problems associated with groundwater flow system in the North China Plain

    NASA Astrophysics Data System (ADS)

    Chen, J.; Tang, C.; Sakura, Y.; Fukushima, Y.; Taniguchi, M.

    2004-12-01

    Environmental problems in the North China Plain (NCP) have arisen since 1980s, when the national economy started to recover from a long time of stagnation. Population, resource, environment and development are four factors closely integrated, and environmental problems may occur when these four factors are not well balanced. Groundwater, as itself a factor of environment and resource, plays a key role in the sustainability of a certain area. Located in the eastern part of China, the North China Plain (NCP) is a very important region of agriculture in China. The project of water transfer from the South to the North was initiated in 2002 solve the water shortage problem of the area, and great environmental impacts on water cycle and groundwater flow system are to be expected. Three environmental problems are to be discussed in a detail: nitrate pollution in the groundwater, salination, and groundwater level draw down. Many environmental problems are closely related to groundwater in terms of either flow system or resource in the North China Plain. The accumulation of salt in the unsaturated zone and regional salination may become worse under the condition of extra water transferred from the south though the groundwater level is expected to recover to some extent. Nitrate pollution pattern and nitrate transport along groundwater flow system under new condition remain to be resolved as complicated biochemical processes are involved in nitrogen cycle.

  4. Quantitative estimation of groundwater recharge ratio along the riparian of the Yellow River.

    PubMed

    Yan, Zhang; Fadong, Li; Jing, Li; Qiang, Liu; Guangshuai, Zhao

    2013-01-01

    Quantitative estimation of groundwater recharge is crucial for limited water resources management. A combination of isotopic and chemical indicators has been used to evaluate the relationship between surface water, groundwater, and rainfall around the riparian of the Yellow River in the North China Plain (NCP). The ion molar ratio of sodium to chloride in surface- and groundwater is 0.6 and 0.9, respectively, indicating cation exchange of Ca(2+) and/or Mg(2+) for Na(+) in groundwater. The ?D and ?(18)O values in rainfall varied from -64.4 to -33.4‰ and from -8.39 to -4.49‰. The groundwater samples have ?D values in the range of -68.7 to -58.0‰ and ?(18)O from -9.29 to -6.85‰. The ?(18)O and ?D in surface water varied from -8.51 to -7.23‰ and from -64.42 to -53.73‰. The average values of both ?D and ?(18)O from surface water are 3.92‰ and 0.57‰, respectively, higher compared to groundwater. Isotopic composition indicated that the groundwater in the riparian area of the Yellow River was influenced by heavy rainfall events and seepage of surface water. The mass balance was applied for the first time to estimate the amount of recharge, which is probably 6% and 94% of the rainfall and surface water, respectively. PMID:24334892

  5. Parameter estimation techniques and uncertainty in ground water flow model predictions

    SciTech Connect

    Zimmerman, D.A. ); Davis, P.A. )

    1990-01-01

    Quantification of uncertainty in predictions of nuclear waste repository performance is a requirement of Nuclear Regulatory Commission regulations governing the licensing of proposed geologic repositories for high-level radioactive waste disposal. One of the major uncertainties in these predictions is in estimating the ground-water travel time of radionuclides migrating from the repository to the accessible environment. The cause of much of this uncertainty has been attributed to a lack of knowledge about the hydrogeologic properties that control the movement of radionuclides through the aquifers. A major reason for this lack of knowledge is the paucity of data that is typically available for characterizing complex ground-water flow systems. Because of this, considerable effort has been put into developing parameter estimation techniques that infer property values in regions where no measurements exist. Currently, no single technique has been shown to be superior or even consistently conservative with respect to predictions of ground-water travel time. This work was undertaken to compare a number of parameter estimation techniques and to evaluate how differences in the parameter estimates and the estimation errors are reflected in the behavior of the flow model predictions. That is, we wished to determine to what degree uncertainties in flow model predictions may be affected simply by the choice of parameter estimation technique used. 3 refs., 2 figs.

  6. Multi-scale experimental programs for estimating groundwater recharge in hydrologically changing basins

    NASA Astrophysics Data System (ADS)

    McIntyre, Neil; Larsen, Josh; Reading, Lucy; Bulovic, Nevenka; Jarihani, Abdollah; Finch, Warren

    2015-04-01

    Groundwater recharge estimates are required to evaluate sustainable groundwater abstractions and to support groundwater impacts assessments associated with minerals and energy extraction. Increasingly, recharge estimates are also needed for regional and global scale water cycle modelling. This is especially the case in the great arid and semi-arid basins of the world due to increased water scarcity and dependence of ecosystems and livelihoods on their water supplies, and the considerable potential influence of groundwater on the hydrological cycle. Groundwater resources in the semi-arid Surat Basin of south-east Queensland, Australia, support extensive groundwater-dependent ecosystems and have historically been utilised for regional agriculture and urban water-use. Large volumes of water are currently being produced and will continue to do so as a part of coal seam gas extraction. There is considerable uncertainty about the impacts of gas extraction on water resources and the hydrological cycle, and much of this uncertainty stems from our limited knowledge about recharge processes and how to upscale them. Particular questions are about the role of storm events in controlling annual recharge, the relative contributions of local 'recharge zones' versus diffuse recharge and the translation of (relatively easily quantified) shallow drainage estimates to groundwater recharge. A multi-scale recharge research program is addressing these questions, using multiple approaches in estimating groundwater recharge, including plot and catchment scale monitoring, use of remote sensed data and simulation models. Results during the first year of the program have resulted in development of process hypotheses and experimental designs at three field sites representing key gaps in knowledge. The presentation will overview the process of designing the experimental program; how the results from these sites will be integrated with existing knowledge; and how results will be used to advance our knowledge of the changing hydrological cycle in the Surat Basin.

  7. Patterns and age distribution of ground-water flow to streams

    USGS Publications Warehouse

    Modica, E.; Reilly, T.E.; Pollock, D.W.

    1997-01-01

    Simulations of ground-water flow in a generic aquifer system were made to characterize the topology of ground-water flow in the stream subsystem and to evaluate its relation to deeper ground-water flow. The flow models are patterned after hydraulic characteristics of aquifers of the Atlantic Coastal Plain and are based on numerical solutions to three-dimensional, steady-state, unconfined flow. The models were used to evaluate the effects of aquifer horizontal-to-vertical hydraulic conductivity ratios, aquifer thickness, and areal recharge rates on flow in the stream subsystem. A particle tracker was used to determine flow paths in a stream subsystem, to establish the relation between ground-water seepage to points along a simulated stream and its source area of flow, and to determine ground-water residence time in stream subsystems. In a geometrically simple aquifer system with accretion, the source area of flow to streams resembles an elongated ellipse that tapers in the downgradient direction. Increased recharge causes an expansion of the stream subsystem. The source area of flow to the stream expands predominantly toward the stream headwaters. Baseflow gain is also increased along the reach of the stream. A thin aquifer restricts ground-water flow and causes the source area of flow to expand near stream headwaters and also shifts the start-of-flow to the drainage basin divide. Increased aquifer anisotropy causes a lateral expansion of the source area of flow to streams. Ground-water seepage to the stream channel originates both from near- and far-recharge locations. The range in the lengths of flow paths that terminate at a point on a stream increase in the downstream direction. Consequently, the age distribution of ground water that seeps into the stream is skewed progressively older with distance downstream. Base flow ia an integration of ground water with varying age and potentially different water quality, depending on the source within the drainage basin. The quantitative results presented indicate that this integration can have a wide and complex residence time range and source distribution.

  8. Investigating groundwater flow between Edwards and Trinity aquifers in central Texas.

    PubMed

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

    2014-01-01

    Understanding the nature of communication between aquifers can be challenging when using traditional physical and geochemical groundwater sampling approaches. This study uses two multiport wells completed within Edwards and Trinity aquifers in central Texas to determine the degree of groundwater inter-flow between adjacent aquifers. Potentiometric surfaces, hydraulic conductivities, and groundwater major ion concentrations and Sr isotope values were measured from multiple zones within three hydrostratigraphic units (Edwards and Upper and Middle Trinity aquifers). Physical and geochemical data from the multiport wells were combined with historical measurements of groundwater levels and geochemical compositions from the region to characterize groundwater flow and identify controls on the geochemical compositions of the Edwards and Trinity aquifers. Our results suggest that vertical groundwater flow between Edwards and Middle Trinity aquifers is likely limited by low permeability, evaporite-rich units within the Upper and Middle Trinity. Potentiometric surface levels in both aquifers vary with changes in wet vs. dry conditions, indicating that recharge to both aquifers occurs through distinct recharge areas. Geochemical compositions in the Edwards, Upper, and Middle Trinity aquifers are distinct and likely reflect groundwater interaction with different lithologies (e.g., carbonates, evaporites, and siliceous sediments) as opposed to mixing of groundwater between the aquifers. These results have implications for the management of these aquifers as they indicate that, under current conditions, pumping of either aquifer will likely not induce vertical cross-formational flow between the aquifers. Inter-flow between the Trinity and the Edwards aquifers, however, should be reevaluated as pumping patterns and hydrogeologic conditions change. PMID:24033308

  9. Digitally processed satellite data as a tool in detecting potential groundwater flow systems

    NASA Astrophysics Data System (ADS)

    Bobba, A. G.; Bukata, R. P.; Jerome, J. H.

    1992-02-01

    Recent hydrologic research provides support for the regional groundwater flow systems concept. The fundamental unit of such a concept is a vertical section in which three groundwater regions are distinguished, namely: recharge, transition, and discharge regions. Simulation of regional groundwater flow models has been devised using this concept. This paper presents an investigation into the use of digital satellite data as a tool in identifying the potential of groundwater flow system areas. Digital radiance data collected by LANDSAT over Big Creek and Big Otter Creek basins in southern Ontario, Canada, have been utilized to delineate the principal groundwater regimes according to the proximity of the water table to the surface, i.e. discharge, recharge, and transition areas. During the spring, the modulating influence of ground water on the near-surface temperature enables such a classification to be performed using only the near-infrared energy band of the satellite. Such classification is directly comparable with thermal data collected by aircraft overflights of the watersheds. During the summer months, however, the presence of phreatophytic vegetation throughout the watershed requires that the visible energy band data be used in conjunction with the near-infrared data to effect such a classification scheme. The location of such groundwater flow systems provides valuable input to the hydrological modeling, the selection of sites for solid waste disposal and non-point-source modeling.

  10. Hydrogeological and Groundwater Flow Model for C, K, L, and P Reactor Areas, Savannah River Site, Aiken, South Carolina

    SciTech Connect

    Flach, G.P.

    1999-02-24

    A regional groundwater flow model encompassing approximately 100 mi{sup 2} surrounding the C, K. L. and P reactor areas has been developed. The Reactor flow model is designed to meet the planning objectives outlined in the General Groundwater Strategy for Reactor Area Projects by providing a common framework for analyzing groundwater flow, contaminant migration and remedial alternatives within the Reactor Projects team of the Environmental Restoration Department.

  11. Climate change and groundwater ecohydrology: Simulating subsurface flow and discharge zones in Covey Hill, Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Levison, J.; Larocque, M.; Ouellet, M.; van Waterschoot, L.

    2013-12-01

    Nearly 2 billion people use groundwater and in Canada it is the potable water supply for about 30% of the population. Groundwater is also used in industrial and agricultural applications, and contributes to important hydrological habitats for various species. Limited research has been conducted to determine the potential impacts of climate change on groundwater. Local studies are crucial to better understand how, for example, increased duration and frequency of storms or drought periods may affect groundwater dependent ecosystems in order to anticipate and mitigate the impacts. Thus, the aim of this research is to explore the effects of climate change on a groundwater-surface water interacting system that supports a fragile ecosystem. This research is used to inform ecological conservation measures. The research site is the 17500 ha Covey Hill Natural Laboratory, which is located on the Quebec, Canada and New York State, USA border in the Chateauguay River watershed. At various locations within the Natural Laboratory there is continuous monitoring of groundwater levels and river flows. Covey Hill is an important recharge zone for the regional aquifer and provides habitat for endangered salamanders in discharge zones. Two hydrogeological models were constructed to represent flow at the site. First, a three-dimensional, finite difference model was developed using MODFLOW software to simulate overall groundwater flow at the research site. Second, a smaller-scale, discrete fracture, transient, three-dimensional, finite difference, integrated model was developed using HydroGeoSphere software to represent in better detail flow from bedrock springs that occur at mid-slope and provide the habitat for endangered salamanders. The models were used to: 1) observe groundwater flow under current climate conditions; 2) quantify water dynamics in response to climate change using 10 scenarios from the Canadian Regional Climate Model (for 1971-2000 and 2041-2070 time periods); and 3) simulate past hydrogeological conditions (100 years). Results show, for example, that future predicted changes in recharge may impact flow to groundwater springs and seeps inhabited by the endangered salamanders. For example, in the 2041-2070 period, some springs are predicted to flow more days per year, but the periods of flow are shifted, which could be critical for the salamander populations. Changes in recharge also induce variations in flow between the headwater peatland and the surrounding bedrock aquifer. Using the results from this study and ecological modeling that was conducted simultaneously by collaborators, measures to mitigate the impacts of climate change on the hydrology and ecology of Covey Hill were made to local water managers and conservationists. This study highlights the importance of conducting ecohydrological and climate change-based studies at various scales and using numerous scenarios to help capture uncertainty of future flows.

  12. A model of regional ground-water flow in secondary-permeability terrane ( Susquehanna River).

    USGS Publications Warehouse

    Gerhart, J.M.

    1984-01-01

    The ground-water flow system in the Lower Susquehanna River Basin in Pennsylvania and Maryland can be considered as one complex unconfined aquifer in which secondary porosity and permeability are the dominant influences on the occurrence and flow of ground water. The degree of development of secondary porosity and permeability in the various lithologies of the lower basin determines the aquifer characteristics of each lithology. Based on qualitative evidence, the use of a porous-media model was assumed to be appropriate on a regional scale and a finite-difference ground-water flow model was constructed for the lower basin. -from Author

  13. Groundwater flow behaviour during the initial development phase of an artificial catchment

    NASA Astrophysics Data System (ADS)

    Mazur, Kai; Schoenheinz, Dagmar; Biemelt, Detlef; Grünewald, Uwe

    2010-05-01

    Artificially created, spatially and structurally well defined hydrological catchments are suitable study sites for hydrological and ecosystem research. One of the largest artificial catchments named "Chicken Creek" with clearly defined boundary conditions and extended monitoring facilities was set up on a dump site from opencast mining activities in Eastern Germany. The catchment, left to undisturbed succession, enables the observation of ecosystem development from the very beginning. Precipitation as the only source of water input is the dominating driving force for the hydrological processes in the initial development phase. Due to the initial absence of vegetation or organic structures, the morphological and hydrogeological properties of the artificial catchment control the runoff and storage processes. In case of the Chicken Creek catchment, they are given by the construction design and technology. In mature natural catchments, the groundwater flow system has normally achieved a dynamic equilibrium stage. In the newly constructed artificial catchment, the groundwater body is just evolving by infiltrating and percolating precipitation which fills the pore volume of the initially unsaturated catchment body. The saturation process has started above the underlying horizontal clay layer that is acting as lower catchment boundary. The observed trend of rising groundwater table superposed by seasonal fluctuations indicates a groundwater recharge higher than the drainage. During the last four years, the filling process is extenuating and an equilibrium between groundwater recharge and drainage is establishing. Groundwater exfiltration preferentially occurs in new gully structures formed by precipitation induced erosion processes. A groundwater model is set up to simulate the groundwater dynamics during the initial phase of the catchment development. Based on the theoretical consideration of initial homogeneity and isotropy, hydrogeologically relevant structures, patterns and their effects on the groundwater system shall be introduced and their effects evaluated in comparison with the field observations. The modelling aims at the identification and description of different flow statuses, threshold behaviour and flow patterns. Observation and simulation results shall be presented.

  14. GROUNDWATER FLOW MODEL CALIBRATION USING WATER LEVEL MEASUREMENTS AT SHORT INTERVALS

    EPA Science Inventory

    Groundwater flow models are usually calibrated with respect to water level measurements collected at intervals of several months or even years. Measurements of these kinds are not sensitive to sudden or short stress conditions, such as impact from stormwater drainage flow or flas...

  15. Ground-water discharge and base-flow nitrate loads of nontidal streams, and their relation to a hydrogeomorphic classification of the Chesapeake Bay Watershed, middle Atlantic Coast

    USGS Publications Warehouse

    Bachman, L. Joseph; Lindsey, Bruce D.; Brakebill, John W.; Powars, David S.

    1998-01-01

    Existing data on base-flow and groundwater nitrate loads were compiled and analyzed to assess the significance of groundwater discharge as a source of the nitrate load to nontidal streams of the Chesapeake Bay watershed. These estimates were then related to hydrogeomorphic settings based on lithology and physiographic province to provide insight on the areal distribution of ground-water discharge. Base-flow nitrate load accounted for 26 to about 100 percent of total-flow nitrate load, with a median value of 56 percent, and it accounted for 17 to 80 percent of total-flow total-nitrogen load, with a median value of 48 percent. Hydrograph separations were conducted on continuous streamflow records from 276 gaging stations within the watershed. The values for base flow thus calculated were considered an estimate of ground-water discharge. The ratio of base flow to total flow provided an estimate of the relative importance of ground-water discharge within a basin. Base-flow nitrate loads, total-flow nitrate loads, and total-flow total-nitrogen loads were previously computed from water-quality and discharge measurements by use of a regression model. Base-flow nitrate loads were available from 78 stations, total-flow nitrate loads were available from 86 stations, and total-flow total-nitrogen loads were available for 48 stations. The percentage of base-flow nitrate load to total-flow nitrate load could be computed for 57 stations, whereas the percentage of base-flow nitrate load to totalflow total-nitrogen load could be computed for 36 stations. These loads were divided by the basin area to obtain yields, which were used to compare the nitrate discharge from basins of different sizes. The results indicate that ground-water discharge is a significant source of water and nitrate to the total streamflow and nitrate load. Base flow accounted for 16 to 92 percent of total streamflow at the 276 sampling sites, with a median value of 54 percent. It is estimated that of the 50 billion gallons of water that reaches the Chesapeake Bay each day, nearly 27 billion gallons is base flow. Generalized lithology (siliciclastic, carbonate, crystalline, and unconsolidated) was combined with physiographic province (the Appalachian Plateau, the Valley and Ridge, the Blue Ridge, the Piedmont, including the Mesozoic Lowland section, and the Coastal Plain) to delineate 11 hydrogeomorphic regions. Areal variation of base flow and base-flow nitrate yield were assessed by means of nonparametric, one-way analysis of variance on basins grouped by the dominant hydrogeomorphic region and by correlation analysis of base flow or base-flow nitrate yield with the percentage of land area of a given hydrogeomorphic region within a basin. Base flow appeared to have a significant relation to the hydrogeomorphic regions. The highest percentages of base flow were found in areas underlain by carbonate rock, crystalline rock with relatively low relief, and unconsolidated sediments. Lower percentages were found in areas underlain by siliclastic rocks and crystalline rocks with relatively high relief. The relation between base-flow nitrate yield and hydrogeomorphic region is less clear. Although there is a relation between low nitrate yields and areas underlain by highrelief siliciclastic rocks, and a relation between high yields and carbonate rocks, much of this relation can be explained by the strong association between the hydrogeomorphic units and land use. In addition, most basins are mixtures of several hydrogeomorphic regions, so the nitrate yield from a basin depends on a large number of complex interacting factors. These unclear results indicate that the sample of available data used here may not be adequate to fully assess the relation between base-flow nitrate yield and the hydrogeomorphic setting of the basin. The results appear to show, however, that ground-water discharge is an important component of the total nontidal streamflow, and that ground

  16. 1r2dinv: A finite-difference model for inverse analysis of two dimensional linear or radial groundwater flow

    USGS Publications Warehouse

    Bohling, G.C.; Butler, J.J., Jr.

    2001-01-01

    We have developed a program for inverse analysis of two-dimensional linear or radial groundwater flow problems. The program, 1r2dinv, uses standard finite difference techniques to solve the groundwater flow equation for a horizontal or vertical plane with heterogeneous properties. In radial mode, the program simulates flow to a well in a vertical plane, transforming the radial flow equation into an equivalent problem in Cartesian coordinates. The physical parameters in the model are horizontal or x-direction hydraulic conductivity, anisotropy ratio (vertical to horizontal conductivity in a vertical model, y-direction to x-direction in a horizontal model), and specific storage. The program allows the user to specify arbitrary and independent zonations of these three parameters and also to specify which zonal parameter values are known and which are unknown. The Levenberg-Marquardt algorithm is used to estimate parameters from observed head values. Particularly powerful features of the program are the ability to perform simultaneous analysis of heads from different tests and the inclusion of the wellbore in the radial mode. These capabilities allow the program to be used for analysis of suites of well tests, such as multilevel slug tests or pumping tests in a tomographic format. The combination of information from tests stressing different vertical levels in an aquifer provides the means for accurately estimating vertical variations in conductivity, a factor profoundly influencing contaminant transport in the subsurface. ?? 2001 Elsevier Science Ltd. All rights reserved.

  17. MODFLOW-2005 : the U.S. Geological Survey modular ground-water model--the ground-water flow process

    USGS Publications Warehouse

    Harbaugh, Arlen W.

    2005-01-01

    This report presents MODFLOW-2005, which is a new version of the finite-difference ground-water model commonly called MODFLOW. Ground-water flow is simulated using a block-centered finite-difference approach. Layers can be simulated as confined or unconfined. Flow associated with external stresses, such as wells, areal recharge, evapotranspiration, drains, and rivers, also can be simulated. The report includes detailed explanations of physical and mathematical concepts on which the model is based, an explanation of how those concepts are incorporated in the modular structure of the computer program, instructions for using the model, and details of the computer code. The modular structure consists of a MAIN Program and a series of highly independent subroutines. The subroutines are grouped into 'packages.' Each package deals with a specific feature of the hydrologic system that is to be simulated, such as flow from rivers or flow into drains, or with a specific method of solving the set of simultaneous equations resulting from the finite-difference method. Several solution methods are incorporated, including the Preconditioned Conjugate-Gradient method. The division of the program into packages permits the user to examine specific hydrologic features of the model independently. This also facilitates development of additional capabilities because new packages can be added to the program without modifying the existing packages. The input and output systems of the computer program also are designed to permit maximum flexibility. The program is designed to allow other capabilities, such as transport and optimization, to be incorporated, but this report is limited to describing the ground-water flow capability. The program is written in Fortran 90 and will run without modification on most computers that have a Fortran 90 compiler.

  18. Patterns and rates of ground-water flow on Long Island, New York

    USGS Publications Warehouse

    Buxton, Herbert T.; Modica, Edward

    1992-01-01

    Increased ground-water contamination from human activities on Long Island has prompted studies to define the pattern and rate of ground-water movement. A two-dimensional, fine-mesh, finite-element model consisting of 11,969 nodes and 22,880 elements was constructed to represent ground-water flow along a north-south section through central Long Island. The model represents average hydrologic conditions within a corridor approximately 15 miles wide. The model solves discrete approximations of both the potential and stream functions. The resulting flownet depicts flow paths and defines the vertical distribution of flow within the section. Ground-water flow rates decrease with depth. Sixty-two percent of the water flows no deeper than the upper glacial (water-table) aquifer, 38 percent enters the underlying Magothy aquifer, and only 3.1 percent enters the Lloyd aquifer. The limiting streamlines for flow to the Magothy and Lloyd aquifers indicate that aquifer recharge areas are narrow east-west bands through the center of the island. The recharge area of the Magothy aquifer is only 5.4 miles wide; that of the Lloyd aquifer is less than 0.5 miles. The distribution of ground-water traveltime and a flownet are calculated from model results; both are useful in the investigation of contaminant transport or the chemical evolution of ground water within the flow system. A major discontinuity in traveltime occurs across the streamline which separates the flow subsystems of the two confined aquifers. Water that reaches the Lloyd aquifer attains traveltimes as high as 10,000 years, whereas water that has not penetrated deeper than the Magothy aquifer attains traveltimes of only 2,000 years. The finite-element approach used in this study is particularly suited to ground-water systems that have complex hydrostratigraphy and cross-sectional symmetry.

  19. Groundwater level monitoring and recharge estimation in the White Volta River basin of Ghana

    NASA Astrophysics Data System (ADS)

    Obuobie, Emmanuel; Diekkrueger, Bernd; Agyekum, William; Agodzo, Sampson

    2012-08-01

    Recharge quantification is an important pre-requisite for effectively managing groundwater resources as recharge estimates are needed to determine sustainable yields of groundwater aquifers for rational and sustainable exploitation of the resource. In this study, the water table fluctuation method has been applied in the White Volta River basin of Ghana (approx. 46,000 km2) to estimate seasonal fluctuations in groundwater levels in the basin and subsequently to estimate recharge to the groundwater for the 2006 and 2007 water years. Results show high seasonal and spatial variability in the water level, with a range of 1240-5000 mm in 2006, and 1600-6800 mm in 2007. Seasonal rainfall was found to be the main source of recharge to the aquifers in the basin as water level rise occurred only in the rainfall season. Recharge to groundwater in the White Volta basin was estimated to vary between 2.5% and 16.5% of the mean annual rainfall, with a mean recharge of 7-8%.

  20. Effects of Daily Precipitation and Evapotranspiration Patterns on Flow and VOC Transport to Groundwater along a Watershed Flow Path

    USGS Publications Warehouse

    Johnson, R.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 semiarid 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.

  1. Groundwater flow model for the General Separations Area, Savannah River Site

    SciTech Connect

    Not Available

    1992-05-15

    The Savannah River Site (SRS) is a Department of Energy (DOE) facility located near Aiken, South Carolina. Assessment of groundwater flow rates and directions, potential contaminant transport times, and concentration of potential contaminants is required to determine current and future environmental effects resulting from releases by these facilities. Proposed closure actions and/or remedial alternatives also need to be evaluated. Numerical groundwater flow and solute transport models are a means of assessing the environmental effects on the groundwater system. They provide a logical method of integrating all available data into a consistent framework for quantitative analysis. The results of groundwater models can be used directly for input to management decisions and design/construct issues or can provide input into risk assessment models for site evaluations. GeoTrans, Inc. was contracted by the Environmental Restoration Department of WSRC to develop a groundwater model of the entire General Separations Area (GSA). Of particular interest is the area surrounding the Mixed Waste Management Facility (MWMF) as shown in Figure 1.2. The model developed in this phase of the study will be used to assess groundwater flow issues for the entire GSA. The second phase of the study will address contaminant transport issues specific to the area surrounding the MWMF.

  2. Rapid intrusion of magma into wet rock: Groundwater flow due to pore pressure increases

    NASA Astrophysics Data System (ADS)

    Delaney, Paul T.

    1982-09-01

    Analytical and numerical solutions are developed to simulate the pressurization, expansion, and flow of groundwater contained within saturated, intact host rocks subject to sudden heating from the planar surface of an igneous intrusion. For most rocks, water diffuses more rapidly than heat, assuring that groundwater is not heated along a constant-volume pressure path and that thermal expansion and pressurization adjacent to the intrusion drives a flow that extends well beyond the heated region. The forcing parameter for pressurization and flow is ? ?T, where ? is a thermal expansion coefficient reflecting the overall expansion of water heated through the temperature difference ?T between the initial ambient and intrusive values. Pore pressure increases due to heating are greatest when the intrusion is emplaced rapidly and where the intrusive contact is impervious to groundwater contained in stiff, impermeable rocks with high thermal diffusivities and porosities. The maximum velocity of water flowing in pores decays with the inverse square root of time and is insensitive to hydraulic properties of the host rocks. Pressures are lessened and flow directions are reversed with the onset of hydrothermal convection. This occurs at times ranging from hours to weeks after onset of intrusion. As magma rises into near-surface rocks, steam can be generated. Solutions indicate that pressure increases and velocities are sensitive to the overall amount of expansion rather than the behavior of the water-steam transition. Both the overall thermal expansion coefficient ? and the temperature difference ?T are greater in shallow (<1 km) environments than in deep (˜5 km) ones. Thus, for rocks with similar transport properties, pressure increases due to heating are greatest in shallow environments. Although solutions can be applied to rocks with a wide variety of properties, pressure increases are calculated for compliant quartz-rich sedimentary rocks with a porosities between 1 and 20% and permeabilities between 1 darcy and 1 ?darcy, subject to temperature increases of 500 and 1000 K at depths ranging from 0.1 to 5 km in a region of hydrostatic pressures and normal geothermal gradient. Such rocks, with porosities greater than 5%, permeabilities less than a 0.1 mdarcy, and drained hydrostatic compressibilities of 10-4/MPa, undergo pressure increases greater than 10 MPa (100 bars)for conditions typical of water table depths of 2.5 km and heating to 500 K above ambient. Similar rocks, but with permeabilities less than 1 mdarcy, undergo pressure increases of 10 MPa for conditions typical of 1 km water table depth. Rocks commonly considered to be good aquifers undergo pressure increases of less than 1 MPa, primarily because of their high permeability. Although these estimates neglect the effects of fracturing and brecciation that may accompany such pressure increases, calculations indicate that pressure increases due to heating of cool groundwater can lead to failure of host rocks by a phreatic mechanism.

  3. Review: Impact of underground structures on the flow of urban groundwater

    NASA Astrophysics Data System (ADS)

    Attard, Guillaume; Winiarski, Thierry; Rossier, Yvan; Eisenlohr, Laurent

    2015-09-01

    Property economics favours the vertical development of cities but flow of groundwater can be affected by the use of underground space in them. This review article presents the state of the art regarding the impact of disturbances caused by underground structures (tunnels, basements of buildings, deep foundations, etc.) on the groundwater flow in urban aquifers. The structures built in the underground levels of urban areas are presented and organised in terms of their impact on flow: obstacle to the flow or disturbance of the groundwater budget of the flow system. These two types of disturbance are described in relation to the structure area and the urban area. The work reviewed shows, on one hand, the individual impacts of different urban underground structures, and on the other, their cumulative impacts on flow, using real case studies. Lastly, the works are placed in perspective regarding the integration of underground structures with the aim of operational management of an urban aquifer. The literature presents deterministic numerical modelling as a tool capable of contributing to this aim, in that it helps to quantify the effect of an underground infrastructure project on groundwater flow, which is crucial for decision-making processes. It can also be an operational decision-aid tool for choosing construction techniques or for formulating strategies to manage the water resource.

  4. Flow path oscillations in transient ground-water simulations of large peatland systems

    USGS Publications Warehouse

    Reeve, A.S.; Evensen, R.; Glaser, P.H.; Siegel, D.I.; Rosenberry, D.

    2006-01-01

    Transient numerical simulations of the Glacial Lake Agassiz Peatland near the Red Lakes in Northern Minnesota were constructed to evaluate observed reversals in vertical ground-water flow. Seasonal weather changes were introduced to a ground-water flow model by varying evapotranspiration and recharge over time. Vertical hydraulic reversals, driven by changes in recharge and evapotranspiration were produced in the simulated peat layer. These simulations indicate that the high specific storage associated with the peat is an important control on hydraulic reversals. Seasonally driven vertical flow is on the order of centimeters in the deep peat, suggesting that seasonal vertical advective fluxes are not significant and that ground-water flow into the deep peat likely occurs on decadal or longer time scales. Particles tracked within the ground-water flow model oscillate over time, suggesting that seasonal flow reversals will enhance vertical mixing in the peat column. The amplitude of flow path oscillations increased with increasing peat storativity, with amplitudes of about 5 cm occurring when peat specific storativity was set to about 0.05 m-1. ?? 2005 Elsevier B.V. All rights reserved.

  5. EVALUATION OF GROUNDWATER FLOW PATTERNS AROUND A DUAL-SCREENED GROUNDWATER CIRCULATION WELL

    EPA Science Inventory

    Dual-screened groundwater circulation wells (GCWs) can be used to remove contaminant mass and to mix reagents in situ. GCWs are so named because they force water in a circular pattern between injection and extraction screens. The radial extent, flux and direction of the effective...

  6. Performance evaluation of a dual-flow recharge filter for improving groundwater quality.

    PubMed

    Samuel, Manoj P; Senthilvel, S; Mathew, Abraham C

    2014-07-01

    A dual-flow multimedia stormwater filter integrated with a groundwater recharge system was developed and tested for hydraulic efficiency and pollutant removal efficiency. The influent stormwater first flows horizontally through the circular layers of planted grass and biofibers. Subsequently, the flow direction changes to a vertical direction so that water moves through layers of pebbles and sand and finally gets recharged to the deep aquifers. The media in the sequence of vegetative medium:biofiber to pebble:sand were filled in nine proportions and tested for the best performing combination. Three grass species, viz., Typha (Typha angustifolia), Vetiver (Chrysopogon zizanioides), and St. Augustine grass (Stenotaphrum secundatum), were tested as the best performing vegetative medium. The adsorption behavior of Coconut (Cocos nucifera) fiber, which was filled in the middle layer, was determined by a series of column and batch studies.The dual-flow filter showed an increasing trend in hydraulic efficiency with an increase in flowrate. The chemical removal efficiency of the recharge dual-flow filter was found to be very high in case of K+ (81.6%) and Na+ (77.55%). The pH normalizing efficiency and electrical conductivity reduction efficiency were also recorded as high. The average removal percentage of Ca2+ was moderate, while that of Mg2+ was very low. The filter proportions of 1:1 to 1:2 (plant:fiber to pebble:sand) showed a superior performance compared to all other proportions. Based on the estimated annual costs and returns, all the financial viability criteria (internal rate of return, net present value, and benefit-cost ratio) were found to be favorable and affordable to farmers in terms of investing in the developed filtration system. PMID:25112029

  7. Investigating groundwater flow paths within proglacial moraine using multiple geophysical methods

    NASA Astrophysics Data System (ADS)

    McClymont, Alastair F.; Roy, James W.; Hayashi, Masaki; Bentley, Laurence R.; Maurer, Hansruedi; Langston, Greg

    2011-03-01

    SummaryGroundwater that is stored and slowly released from alpine watersheds plays an important role in sustaining mountain rivers. Yet, little is known about how groundwater flows within typical alpine geological deposits like glacial moraine, talus, and bedrock. Within the Lake O'Hara alpine watershed of the Canadian Rockies, seasonal snowmelt and rain infiltrates into a large complex of glacial moraine and talus deposits before discharging from a series of springs within a relatively confined area of a terminal moraine deposit. In order to understand the shallow subsurface processes that govern how groundwater is routed through this area, we have undertaken a geophysical study on glacial moraine and bedrock over and around the springs. From interpretations of several seismic refraction, ground-penetrating radar (GPR), and electrical resistivity tomography (ERT) profiles, we delineate the topography of bedrock beneath moraine. Although the bedrock is generally flat under central parts of the terminal moraine, we suggest that an exposed slope of bedrock on its eastern side and a ridge of shallow bedrock imaged by ERT data underneath its western margin serves to channel deep groundwater toward the largest spring. Low-electrical-resistivity anomalies identified on ERT images within shallow parts of the moraine indicate the presence of groundwater flowing over shallow bedrock and/or ice. From coincident seismic refraction, GPR and ERT profiles, we interpret an ca. 5-m-thick deep layer of saturated moraine and fractured bedrock. Despite their relatively small storage volumes, we suggest that groundwater flowing through bedrock cracks may provide an important contribution to stream runoff during low-flow periods. The distinct deep and shallow groundwater flow paths that we interpret from geophysical data reconcile with interpretations from previous analyses of hydrograph and water chemistry data from this same area.

  8. Structural Controls on Groundwater Flow in Basement Terrains: Geophysical, Remote Sensing, and Field Investigations in Sinai

    NASA Astrophysics Data System (ADS)

    Mohamed, Lamees; Sultan, Mohamed; Ahmed, Mohamed; Zaki, Abotalib; Sauck, William; Soliman, Farouk; Yan, Eugene; Elkadiri, Racha; Abouelmagd, Abdou

    2015-09-01

    An integrated [very low frequency (VLF) electromagnetic, magnetic, remote sensing, field, and geographic information system (GIS)] study was conducted over the basement complex in southern Sinai (Feiran watershed) for a better understanding of the structural controls on the groundwater flow. The increase in satellite-based radar backscattering values following a large precipitation event (34 mm on 17-18 January 2010) was used to identify water-bearing features, here interpreted as preferred pathways for surface water infiltration. Findings include: (1) spatial analysis in a GIS environment revealed that the distribution of the water-bearing features (conductive features) corresponds to that of fractures, faults, shear zones, dike swarms, and wadi networks; (2) using VLF (43 profiles), magnetic (7 profiles) techniques, and field observations, the majority (85 %) of the investigated conductive features were determined to be preferred pathways for groundwater flow; (3) northwest-southeast- to north-south-trending conductive features that intersect the groundwater flow (southeast to northwest) at low angles capture groundwater flow, whereas northeast-southwest to east-west features that intersect the flow at high angles impound groundwater upstream and could provide potential productive well locations; and (4) similar findings are observed in central Sinai: east-west-trending dextral shear zones (Themed and Sinai Hinge Belt) impede south to north groundwater flow as evidenced by the significant drop in hydraulic head (from 467 to 248 m above mean sea level) across shear zones and by reorientation of regional flow (south-north to southwest-northeast). The adopted integrated methodologies could be readily applied to similar highly fractured basement arid terrains elsewhere.

  9. Hydrogeologic Setting and Ground-Water Flow in the Leetown Area, West Virginia

    USGS Publications Warehouse

    Kozar, Mark D.; Weary, David J.; Paybins, Katherine S.; Pierce, Herbert A.

    2007-01-01

    The Leetown Science Center is a research facility operated by the U.S. Geological Survey that occupies approximately 455-acres near Kearneysville, Jefferson County, West Virginia. Aquatic and fish research conducted at the Center requires adequate supplies of high-quality, cold ground water. Three large springs and three production wells currently (in 2006) supply water to the Center. The recent construction of a second research facility (National Center for Cool and Cold Water Aquaculture) operated by the U.S. Department of Agriculture and co-located on Center property has placed additional demands on available water resources in the area. A three-dimensional steady-state finite-difference ground-water flow model was developed to simulate ground-water flow in the Leetown area and was used to assess the availability of ground water to sustain current and anticipated future demands. The model also was developed to test a conceptual model of ground-water flow in the complex karst aquifer system in the Leetown area. Due to the complexity of the karst aquifer system, a multidisciplinary research study was required to define the hydrogeologic setting. Geologic mapping, surface- and borehole-geophysical surveys, stream base-flow surveys, and aquifer tests were conducted to provide the hydrogeologic data necessary to develop and calibrate the model. It would not have been possible to develop a numerical model of the study area without the intensive data collection and methods developments components of the larger, more comprehensive hydrogeologic investigation. Results of geologic mapping and surface-geophysical surveys verified the presence of several prominent thrust faults and identified additional faults and other complex geologic structures (including overturned anticlines and synclines) in the area. These geologic structures are known to control ground-water flow in the region. Results of this study indicate that cross-strike faults and fracture zones are major avenues of ground-water flow. Prior to this investigation, the conceptual model of ground-water flow for the region focused primarily on bedding planes and strike-parallel faults and joints as controls on ground-water flow but did not recognize the importance of cross-strike faults and fracture zones that allow ground water to flow downgradient across or through less permeable geologic formations. Results of the ground-water flow simulation indicate that current operations at the Center do not substantially affect either streamflow (less than a 5-percent reduction in annual streamflow) or ground-water levels in the Leetown area under normal climatic conditions but potentially could have greater effects on streamflow during long-term drought (reduction in streamflow of approximately 14 percent). On the basis of simulation results, ground-water withdrawals based on the anticipated need for an additional 150 to 200 gal/min (gallons per minute) of water at the Center also would not seriously affect streamflow (less than 8 to 9 percent reduction in streamflow) or ground-water levels in the area during normal climatic conditions. During drought conditions, however, the effects of current ground-water withdrawals and anticipated additional withdrawals of 150 to 200 gal/min to augment existing supplies result in moderate to substantial declines in water levels of 0.5-1.2 feet (ft) in the vicinity of the Center's springs and production wells. Streamflow was predicted to be reduced locally by approximately 21 percent. Such withdrawals during a drought or prolonged period of below normal ground-water levels would result in substantial declines in the flow of the Center's springs and likely would not be sustainable for more than a few months. The drought simulated in this model was roughly equivalent to the more than 1-year drought that affected the region from November 1998 through February 2000. The potential reduction in streamflow is a result of capture of ground water tha

  10. The fate of Nitrate under the natural groundwater flow system in a volcanic aquifer composed by pyroclastic flow

    NASA Astrophysics Data System (ADS)

    Mikami, K.; Shimada, J.; Tashiro, S.

    2008-12-01

    Nitrate in drinking water causes health problems, and causes eutrophication. Miyakonojo basin is a well- known agricultural area in Southern Kyushu, Japan and highly depends on groundwater resources for everyday use. The detailed three dimensional groundwater flow system study has been done in the basin to understand the three dimensional distribution of Nitrate-Nitrogen in the aquifer. Field water sampling was conducted between Sep. 2006 and July 2007. The result suggests that the tributary river water mainly recharges to the shallow groundwater in the eastern part of the basin. On the other hand, the summer precipitation recharges the shallow groundwater which flows from upland down toward the river in the western part of the basin. This means that the shallow groundwater flow system is primarily affected by the surface geomorphology, which is completely different between eastern and western parts of the studied basin. For nitrate concentration, the shallow groundwater shows gradual increasing tendency along the flow line in the eastern part of the basin, while the nitrate concentration decreases and the reduction product increases along the flow in the western part. Especially in the western part of the basin, the major land use are the intensive cattle farming and dry farm land using artificial fertilizer, both are the potential sources of the nitrate for the local shallow groundwater. Also geomorphologic upland of the western part of the basin works as the recharge area of the shallow groundwater, and high concentration of nitrate is supplied at these areas. To understand this site-specific nitrate reduction process in the western basin, it is important to understand the nitrate origin and nitrogen process including denitrifcation process. For this, a multi-Isotope approach of dN and dO to tracing the sources of nitrate is applied in the study area with the relation of groundwater flow system. The field sampling was done in July 2007 and Sep. 2008 to analyze inorganic water chemistry, dD and d18O stable isotopes in water andd15N and d18O in Nitrate. We intend to report this result and related discussion at the meeting.

  11. Phase II Groundwater Flow Model of Corrective Action Unit 98: Frenchman Flat, Nevada Test Site, Nye County, Nevada, Rev. No.: 0

    SciTech Connect

    John McCord

    2006-05-01

    The Phase II Frenchman Flat groundwater flow model is a key element in the ''Federal Facility Agreement and Consent Order'' (FFACO) (1996) corrective action strategy for the Underground Test Area (UGTA) Frenchman Flat corrective action unit (CAU). The objective of this integrated process is to provide an estimate of the vertical and horizontal extent of contaminant migration for each CAU to predict contaminant boundaries. A contaminant boundary is the model-predicted perimeter that defines the extent of radionuclide-contaminated groundwater from underground testing above background conditions exceeding the ''Safe Drinking Water Act'' (SDWA) standards. The contaminant boundary will be composed of both a perimeter boundary and a lower hydrostratigraphic unit (HSU) boundary. The computer model will predict the location of this boundary within 1,000 years and must do so at a 95 percent level of confidence. Additional results showing contaminant concentrations and the location of the contaminant boundary at selected times will also be presented. These times may include the verification period, the end of the five-year proof-of-concept period, as well as other times that are of specific interest. This report documents the development and implementation of the groundwater flow model for the Frenchman Flat CAU. Specific objectives of the Phase II Frenchman Flat flow model are to: (1) Incorporate pertinent information and lessons learned from the Phase I Frenchman Flat CAU models. (2) Develop a three-dimensional (3-D), mathematical flow model that incorporates the important physical features of the flow system and honors CAU-specific data and information. (3) Simulate the steady-state groundwater flow system to determine the direction and magnitude of groundwater fluxes based on calibration to Frenchman Flat hydrogeologic data. (4) Quantify the uncertainty in the direction and magnitude of groundwater flow due to uncertainty in parameter values and alternative component conceptual models (e.g., geology, boundary flux, and recharge).

  12. Depth of the Martian cryosphere: Revised estimates and implications for the existence and detection of subpermafrost groundwater

    NASA Astrophysics Data System (ADS)

    Clifford, Stephen M.; Lasue, Jeremie; Heggy, Essam; Boisson, Joséphine; McGovern, Patrick; Max, Michael D.

    2010-07-01

    The Martian cryosphere is defined as that region of the crust where the temperature remains continuously below the freezing point of water. Previous estimates of its present thickness have ranged from ˜2.3-4.7 km at the equator to ˜6.5-12.5 km at the poles. Here we revisit these calculations, review some of the assumptions on which they were based, and investigate the effects of several parameters, not previously considered, on the cryosphere’s thermal evolution and extent. These include astronomically driven climate change, the temperature-dependent thermal properties of an ice-rich crust, the potential presence of gas hydrate and perchlorate-saturated groundwater, and consideration of recent lower estimates of present-day global heat flow (which suggest a mean value roughly half that previously thought, effectively doubling the potential thickness of frozen ground). The implications of these findings for the continued survival of subpermafrost groundwater and its potential detection by the MARSIS radar sounder onboard Mars Express are then discussed. Although our estimates of the maximum potential thickness of the cryosphere have significantly increased, consideration of the likely range and spatial variability of crustal heat flow and thermal properties, in combination with the potential presence of potent freezing point depressing salts, may result in substantial local variations in cryosphere thickness. The locations that appear best suited for the detection of groundwater are those that combine low latitude (minimizing the thickness of frozen ground) and low elevation (minimizing the depth to a water table in hydrostatic equilibrium). Preliminary results from a MARSIS investigation of one such area are discussed.

  13. A coupled surface-water and ground-water flow model (MODBRANCH) for simulation of stream-aquifer interaction

    USGS Publications Warehouse

    Swain, Eric D.; Wexler, Eliezer J.

    1996-01-01

    Ground-water and surface-water flow models traditionally have been developed separately, with interaction between subsurface flow and streamflow either not simulated at all or accounted for by simple formulations. In areas with dynamic and hydraulically well-connected ground-water and surface-water systems, stream-aquifer interaction should be simulated using deterministic responses of both systems coupled at the stream-aquifer interface. Accordingly, a new coupled ground-water and surface-water model was developed by combining the U.S. Geological Survey models MODFLOW and BRANCH; the interfacing code is referred to as MODBRANCH. MODFLOW is the widely used modular three-dimensional, finite-difference ground-water model, and BRANCH is a one-dimensional numerical model commonly used to simulate unsteady flow in open- channel networks. MODFLOW was originally written with the River package, which calculates leakage between the aquifer and stream, assuming that the stream's stage remains constant during one model stress period. A simple streamflow routing model has been added to MODFLOW, but is limited to steady flow in rectangular, prismatic channels. To overcome these limitations, the BRANCH model, which simulates unsteady, nonuniform flow by solving the St. Venant equations, was restructured and incorporated into MODFLOW. Terms that describe leakage between stream and aquifer as a function of streambed conductance and differences in aquifer and stream stage were added to the continuity equation in BRANCH. Thus, leakage between the aquifer and stream can be calculated separately in each model, or leakages calculated in BRANCH can be used in MODFLOW. Total mass in the coupled models is accounted for and conserved. The BRANCH model calculates new stream stages for each time interval in a transient simulation based on upstream boundary conditions, stream properties, and initial estimates of aquifer heads. Next, aquifer heads are calculated in MODFLOW based on stream stages calculated by BRANCH, aquifer properties, and stresses. This process is repeated until convergence criteria are met for head and stage. Because time steps used in ground-water modeling can be much longer than time intervals used in surface- water simulations, provision has been made for handling multiple BRANCH time intervals within one MODFLOW time step. An option was also added to BRANCH to allow the simulation of channel drying and rewetting. Testing of the coupled model was verified by using data from previous studies; by comparing results with output from a simpler, four-point implicit, open-channel flow model linked with MODFLOW; and by comparison to field studies of L-31N canal in southern Florida.

  14. A quantitative model of ground-water flow during formation of tabular sandstone uranium deposits

    USGS Publications Warehouse

    Sanford, R.F.

    1994-01-01

    Presents a quantitative simulation of regional groundwater flow during uranium deposition in the Westwater Canyon Member and Jackpile Sandstone Member of the Upper Jurassic Morrison Formation in the San Juan basin. Topographic slope, shoreline position, and density contrasts in the lake and pore fluids controlled the directions of flow and recharge-discharge areas. The most important results for uranium ore deposit formation are that regional groundwater discharged throughout the basin, regional discharge was concentrated along the shore line or playa margin, flow was dominantly gravity driven, and compaction dewatering was negligible. A strong association is found between the tabular sandstone uranium deposits and major inferred zones of mixed local and regional groundwater discharge. -from Author

  15. A ROOT ZONE MODELLING APPROACH TO ESTIMATING GROUNDWATER RECHARGE FROM IRRIGATED AREAS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In irrigated semi-arid and arid regions, accurate knowledge of groundwater recharge is important for the sustainable management of scarce water resources. The Campo de Cartagena area of southeast Spain is a semi-arid region where irrigation return flow accounts for a substantial portion of recharge....

  16. Application of isotopes to estimate water ages in variable time scales in surface and groundwaters

    NASA Astrophysics Data System (ADS)

    Kralik, Martin

    2014-05-01

    Water-Isotopes (2H, 3H, 18O) are ideal tracers not only to determine the origin of waters in precipitation, surface water (river + lakes) as well as in groundwater close to the surface and in deep groundwater but also the mean residence time (MRT) in many applied projects as drinking water supply, hydroelectric power plants, road tunnels etc. . Their application has a long history, but must be always evaluated by a feasible hydrogeological concept and/or other isotope and geochemical tracers. In Alpine areas the retention of precipitation in form of snow and ice in the winter half year is indicated by the lowest 18O-values. The snow melt of the highest part of the recharge area is marked by the lowest 18O-values in the river water, but may not coincide with the maximum flow. Time-series of precipitation station in the mountain and on river station indicate the arrival of the peak snow-melt water in the river and in Low-land areas 4-7 month later. Tritium series indicate that MRTs of several Austrian rivers are in the range of 4 - 6 years. The seasonal input variation of in 18O in precipitation and/or river waters can be used to calculate by lumped parameter models MRT of groundwater at a certain well and compare it with lysimeter measurements and transient model simulations. The MRT of the dispersion model is in good agreement with the estimated time calculated by the numerical transport model and the vertical lysimeter measurements. The MRT of spring water was studied by several methods (3H/3He, SF6 and 85Kr) and a long time series of 3H-measurements. The gas tracers are in good agreement in the range of 6-10 year whereas the 3H-series model (dispersion model) indicate ages in the range of 18-23 years. The hydrogeological concept indicate that the precipitation infiltrates in a mountainous karst area, but the transfer into the porous aquifer in the Vienna Basin occurs either through rivers draining away in the basin or through the lateral transport from the karst area to the porous aquifer. This transfer leads to an equilibration with the atmosphere causing the age difference.

  17. Water balance-based estimation of groundwater recharge in the Lake Chad Basin

    NASA Astrophysics Data System (ADS)

    Babamaaji, R. A.; Lee, J.

    2012-12-01

    Lake Chad Basin (LCB) has experienced drastic changes of land cover and poor water management practices during the last 50 years. The successive droughts in the 1970s and 1980s resulted in the shortage of surface water and groundwater resources. This problem of drought and shortage of water has a devastating implication on the natural resources of the Basin with great consequence on food security, poverty reduction and quality of life of the inhabitants in the LCB. Therefore, understanding the change of land use and its characteristics must be a first step to find how such changes disturb the water cycle especially the groundwater in the LCB. The abundance of groundwater is affected by the climate change through the interaction with surface water, such as lakes and rivers, and vertical recharge through an infiltration process. Quantifying the impact of climate change on the groundwater resource requires not only reliable forecasting of changes in the major climatic variables, but also accurate estimation of groundwater recharge. Spatial variations in the land use/land cover, soil texture, topographic slope, and meteorological conditions should be accounted for in the recharge estimation. In this study, we employed a spatially distributed water balance model WetSpass to simulate a long-term average change of groundwater recharge in the LCB of Africa. WetSpass is a water balance-based model to estimate seasonal average spatial distribution of surface runoff, evapotranspiration, and groundwater recharge. The model is especially suitable for studying the effect of land use/land cover change on the water regime in the LCB. The present study describes the concept of the model and its application to the development of recharge map of the LCB.

  18. Analysis of multicomopnent groundwater flow in karst aquifer by CFC, tritium, tracer test and modelling, case study at Skaistkalnes vicinity, Latvia

    NASA Astrophysics Data System (ADS)

    Bikshe, Janis; Babre, Alise; Delina, Aija; Popovs, Konrads

    2014-05-01

    Groundwater in karst environments tends to have difficulties to distinguish multiple flows if several sources of water are present. Skaistkalne vicinity faces with such situation where old groundwater, fresh groundwater and inflow from river Iecava occurs. Attempts were made to distinguish groundwater residence time of multiple components of water applying CFC and tritium dating techniques supplied by tracer test and numerical model of study area. Study area covers territory between two rivers Iecava and Memele with water level difference of 7 meters and horizontal distance of 2.2 kilometres between both. Study area consists of karst affected Devonian gypsum and carbonaceous rocks covered by Quaternary low to high permeable deposits. Confined groundwater at depth of 10-25 meters where analysed by CFC's and tritium. At this depth groundwater exhibits anoxic reducing environment that has caused degradation of CFC's at similar degree in all samples. Taking it into account, mean residence time based on CFC piston flow model is 22 - 42 years and 28 - 34 years based on binary mixing model. Tritium results show signs of incensement of groundwater residence time towards discharge area. CFC combined with tritium proved increased vertical velocity in middle part between the rivers likely caused by hydrogeological window in Quaternary deposits created by karst processes. Numerical model (Delina et al. 2012) was applied and calculations yielded groundwater flow velocity rate at 0.3 - 1 m/day in area between the rivers. Investigation of CFC data resulted in possible groundwater flow rate of at a minimum of 0.2 m/day although it's not applicable to all sampled wells due to specific hydrogeological conditions. Tracer test was made between the rivers in order to distinguish main water flow paths and flow velocity. Results showed that very high permeable conduits connect rivers and karst lakes with velocity rates of 800 - 1300 m/day. Complex investigation leads to conclude that three different sources of groundwater occur characterized by different flow velocity, recharge age and chemical composition. Although CFC's has been degraded, it is possible to use the results to distinguish groundwater different components and even to estimate groundwater flow velocity because of near located recharge and discharge areas. Tritium results doesn't show considerable variations along flow path with 6 TU in average confirming conclusions based on CFC's. Tracer test approve very high groundwater velocity zones in study area that supposedly doesn't mix with groundwater in matrix. References Delina A., Babre A., Popovs K., Sennikovs J., Grinberga B. 2012. Effects of karst processes on surface water and groundwater hydrology at Skaistkalne vicinity, Latvia. - Hydrology Research, 43(4), IWA Publishing, pp. 445-459, doi:10.2166/nh.2012.123. This study is supported by ERAF project Nr. 1013/00542DP/2.1.1.1.0/13/APIA/VIAA/007

  19. An Analytical Study on Periodically Changing Flow Cells in Groundwater Basins

    NASA Astrophysics Data System (ADS)

    Jiang, X.; Zhao, K. Y.; Wang, J. Z.; Wan, L.; Wang, H.

    2014-12-01

    Current understanding on basin-scale groundwater flow is mainly based on Tóth's (1962, 1963) pioneering study, which assumed that water table is a subdued replica of topography and the annual mean water table controls the pattern of groundwater flow. In fact, water table is driven by dynamic forcing and changes with time. This study modifies the conceptual model of basin-scale groundwater flow by taking the fluctuating water-table into account. For both unit basin and complex basin, water table fluctuates throughout the basin cross-section except for at basin valleys. By the method of separation of variables, we derive the analytical solution of hydraulics head and stream function in the unit basin and the complex basin, and discuss the characteristics of the time-dependent flow cells. For the unit basin, the change in amplitude of hydraulic head fluctuation with depth is studied. For the complex basin, the time-dependent distribution of internal stagnation points is discussed. In addition, the relationship between flowing artesian zone and the fluctuating water-table is discussed. The results of the current study enhance our understanding on the transient nature of basin-scale groundwater flow.

  20. Simulation of groundwater flow at the LBNL site using TOUGH2

    SciTech Connect

    Zhou, Quanlin; Birkholzer, Jens T.; Javandel, Iraj; Jordan, Preston D.

    2003-05-12

    In the late 1980s, groundwater contamination was detected at the site of the Lawrence Berkeley National Laboratory (LBNL). A detailed investigation was conducted to locate the source and the extent of the contamination. Interim corrective measures were initiated where appropriate and required, typically directed towards removing the source of contamination, excavating contaminated soil, and limiting further spreading of contaminants. As the first step for predicting the fate of remaining contaminants, a three-dimensional transient groundwater flow model was developed for the complex hydrogeological situation. This flow model captured strong variations in thickness, slope, and hydrogeological properties of geologic units, representative of a mountainous groundwater system with accentuated morphology. The flow model accounts for strong seasonal fluctuations in the groundwater table. Other significant factors are local recharge from leaking underground storm drains and significant water re charge from steep hills located upstream. The strong heterogeneous rock properties were calibrated using the inverse simulator ITOUGH2. For validation purposes, the model was calibrated for a time period from 1994 to 1996, and then applied to a period from 1996 to 1998. Comparison of simulated and measured water levels demonstrated that the model accurately represents the complex flow situation, including the significant seasonal fluctuations in water table and flow rate. Paths of particles originating from contaminant plumes in the simulated transient flow fields were obtained to represent advective transport.

  1. Geohydrology and simulated ground-water flow in northwestern Elkhart County, Indiana

    USGS Publications Warehouse

    Arihood, L.D.; Cohen, D.A.

    1998-01-01

    In 1994, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency and the City of Elkhart, developed a ground-water model of the Elkhart, Indiana, area to determine the avail-ability and source of water at potential new well fields. The modeled area covered 190 square miles of northwestern Elkhart County and a small part of southern Michigan. Three Superfund sites and several other sites in this area are undergoing environmental cleanup. The model would be used to guide the location of well fields so that Superfund sites and environmental cleanup areas would not be within recharge areas for the well fields. The City of Elkhart obtains its water supply from two aquifers separated by a generally continuous confining unit. The upper aquifer is composed primarily of sand and gravel of glacial origin. Thickness of the upper aquifer ranges from 0 to 116 feet and averages 47 feet. The lower aquifer is composed of sand and gravel with interbedded lenses of silt and clay. Thickness of the lower aquifer ranges from 1 to 335 feet and averages 35 feet. The intervening confining unit is composed of silt and clay with interbedded sand and gravel; the confining unit ranges from 0 to 177 feet, with an average thickness of 27 feet. Flow through the aquifers is generally horizontal vertically downward from the upper aquifer, through the confining unit, and into the lower aquifer, except where flow is vertically upward at the St. Joseph River and other large streams. The hydraulic characteristics of the aquifers and confining unit were estimated by analyzing aquifer-test data from well drillers? logs and by calibration of the model. The horizontal hydraulic conductivity of the upper aquifer is 170 feet per day within about 1 mile of the St. Joseph and Elkhart Rivers and 370 feet per day at distances greater than about 1 mile. The horizontal hydraulic conductivity of the lower aquifer is 370 feet per day throughout the modeled area, with the exception of an area near the center of the modeled area where the horizontal hydraulic conductivity is 170 feet per day. Transmissivity of the lower aquifer increases generally from southwest to northeast; transmissivity values range from near 0 where the lower aquifer is absent to 57,000 square feet per day and average about 8,100 square feet per day. The vertical hydraulic conductivity of the confining unit is 0.07 feet per day; the vertical conductivity of the streambeds commonly is 1.0 foot per day and ranges from 0.05 foot per day to 50 feet per day. The areal recharge rate to the outwash deposits was determined by a base-flow separation technique to be 16 inches per year, and the areal recharge rate to the till was assumed to be 4 inches per year. A two-layer digital model was used to simulate flow in the ground-water system. The model was calibrated on the basis of historical water-use data, water-level records, and gain/loss data for streams during May and June 1979. The model was recalibrated with water-use data and water-level records from 1988. For 1979 data, 49 percent of the inflow to the model area is from precipitation and 46 percent is ground-water inflow across the model boundaries. Most of the ground-water inflow across the model boundary is from the north and east, which corresponds to high values of transmissivity?as high as 57,000 feet squared per day?in the model layers in the northern and eastern areas. Eighty-two percent of the ground-water discharge is to the streams; 5 percent of the ground-water discharge is to wells. Source areas and flow paths to the City of Elkhart public well fields are affected by the location of streams and the geology in the area. Flow to the North Well Field originates north-west of the well field, forms relatively straight flow paths, and moves southeast toward the well field and the St. Joseph River. Flow to the South Well Field begins mostly in the out-wash along Yellow Creek south of the well field, moves northward, and t

  2. Influence of groundwater extraction on river flows and the surrounding ecosystem

    NASA Astrophysics Data System (ADS)

    Belova, Anna

    2010-05-01

    Influence of groundwater extraction on river flows and the surrounding ecosystem. Change of hydro-geological conditions and the conditions of environment connected with them? One of the most adverse consequences of the large centralised operation of underground waters coastal (riverine) water fences. Such situation is predicted on the Permilovsky deposit reconnoitered for water supply of Arkhangelsk. The projected water fence was planned in a valley of the river of Vajmugi on its left coast. The predesigns spent on hydrogeodynamic of model of a deposit, show that as a result of operation of underground waters the damage to a drain of the river Vajmuga approximately equal ?????? of a water fence that leads to a considerable shallowing of the river, especially during its periods ????????????, up to a drain total disappearance on a water fence site is formed. On the average, on territories of a deposit expenses of the river concerning natural state can be reduced more than to 50 %. Reduction of a river drain will lead to considerable negative consequences in environment, including: - changes in surface runoff, reduced groundwater levels, inhibit vegetation and changes in plant communities, draining wetlands, changing soil moisture conditions, a decrease of spring runoff, damage to forestry; - earth's surface subsidence, damage to streets and roads, buildings, structures and communications, drainage wells, the development of karst processes and suffosion; - the formation of deep depressions, capturing several zones of water exchange, which could lead to mixing of water of different chemical composition and mineralization of the runoff into surface water bodies, increase the nitrogen content in groundwater; - discontinuity separating the layers and the increased vulnerability of groundwater and surface water, the action of man-made agents. The aim of this study was a preliminary study of alternative schemes of exploitation of underground water deposits, in which damage to river flow, essentially inevitable, will be minimized. The alternative scheme provides reduction of productivity of the basic water fence during the periods critical aquaticity. During these periods, for preservation of volume of water giving, the additional (compensatory) water fence is entered into operation. Settlement remoteness compensatory water fence is defined by a condition that for rather short-term period (in low flow) water fence works, its hydrodynamic influence did not reach the river and basic water fence. At the same time, during the periods high aquaticity when compensatory water fence does not work, stocks ??????????? horizon on the area of its depression should be restored completely. For use of this scheme it is necessary to define the periods of an inadmissible damage to a drain during which reduction discharge of the basic water fence both use compensatory water fence, and operational loading basic water fence and compensatory water fence during the periods of their teamwork is required. Is minimum admissible expense for the given territory should be defined after the special ecological analysis. For tentative estimations 2 variants are considered: 1) in the river of Vajmuga, in a water fence alignment, the expense not below 25 % from minimum low-flow natural size all-the-year-round should remain; 2) on a water fence site in the river the expense not below 25 % from mid-annual size should remain. For both variants the periods of reduction of productivity of the basic water fence are proved and introductions in operation of the compensatory water fence. Have been calculated values of reduction of productivity of the basic water fence, its new discharge and as discharge of the compensatory water fence. It is received that discharge of the basic water fence should be reduced to 35 and 37 % for the first and second settlement variants accordingly. The quantity of knots

  3. ANALYSIS AND REDUCTION OF LANDSAT DATA FOR USE IN A HIGH PLAINS GROUND-WATER FLOW MODEL.

    USGS Publications Warehouse

    Thelin, Gail; Gaydas, Leonard; Donovan, Walter; Mladinich, Carol

    1984-01-01

    Data obtained from 59 Landsat scenes were used to estimate the areal extent of irrigated agriculture over the High Plains region of the United States for a ground-water flow model. This model provides information on current trends in the amount and distribution of water used for irrigation. The analysis and reduction process required that each Landsat scene be ratioed, interpreted, and aggregated. Data reduction by aggregation was an efficient technique for handling the volume of data analyzed. This process bypassed problems inherent in geometrically correcting and mosaicking the data at pixel resolution and combined the individual Landsat classification into one comprehensive data set.

  4. Modelling the effect of buried valleys on groundwater flow: case study in Ventspils vicinity, Latvia

    NASA Astrophysics Data System (ADS)

    Delina, Aija; Popovs, Konrads; Bikse, Janis; Retike, Inga; Babre, Alise; Kalvane, Gunta

    2015-04-01

    Buried subglacial valleys are widely distributed in glaciated regions and they can have great influence on groundwater flow and hence on groundwater resources. The aim of this study is to evaluate the effect of the buried valleys on groundwater flow in a confined aquifer (Middle Devonian Eifelian stage Arukila aquifer, D2ar) applying numerical modelling. The study area is located at vicinity of Ventspils Town, near wellfield Ogsils where number of the buried valleys with different depth and filling material are present. Area is located close to the Baltic Sea at Piej?ra lowland Rinda plain and regional groundwater flow is towards sea. Territory is covered by thin layer of Quaternary sediments in thicknesses of 10 to 20 meters although Prequaternary sediments are exposed at some places. Buried valleys are characterized as narrow, elongated and deep formations that is be filled with various, mainly Pleistocene glacigene sediments - either till loam of different ages or sand and gravel or interbedding of both above mentioned. The filling material of the valleys influences groundwater flow in the confined aquifers which is intercepted by the valleys. It is supposed that glacial till loam filled valleys serves as a barrier to groundwater flow and as a recharge conduit when filled with sand and gravel deposits. Numerical model was built within MOSYS modelling system (Virbulis et al. 2012) using finite element method in order to investigate buried valley influence on groundwater flow in the study area. Several conceptual models were tested in numerical model depending on buried valley filling material: sand and gravel, till loam or mixture of them. Groundwater flow paths and travel times were studied. Results suggested that valley filled with glacial till is acting as barrier and it causes sharp drop of piezometric head and downward flow. Valley filled with sand and gravel have almost no effect on piezometric head distribution, however it this case buried valleys encourage groundwater recharge from shallower aquifers. Modelling results with and without valleys shows that buried valleys affect piezometric head in narrow zone around valley. Sand and gravel filled buried valleys recharges confined aquifer with relatively "new" water, thus creating high vulnerability zones in the study area. This research is supported by European Regional Development Fund project Nr.2013/0054/2DP/2.1.1.1.0/13/APIA/VIAA/007 and NRP project EVIDENnT project "Groundwater and climate scenarios" subproject "Groundwater Research". References: Virbulis, J., Timuhins, A., Klints, I., Se??ikovs, J., Bethers, U., Popovs, K. 2012. Script based MOSYS system for the generation of a three dimensional geological structure and the calculation of groundwater flow: case study of the Baltic Artesian Basin. In: Highlights of groundwater research in the Baltic Artesian Basin. University of Latvia, Riga, pp. 53-74.

  5. A groundwater flow and transport model of long-term radionuclide migration in central Frenchman flat, Nevada test site

    SciTech Connect

    Kwicklis, Edward Michael; Becker, Naomi M; Ruskauff, Gregory; De Novio, Nicole; Wilborn, Bill

    2010-11-10

    A set of groundwater flow and transport models were created for the Central Testing Area of Frenchman Flat at the former Nevada Test Site to investigate the long-term consequences of a radionuclide migration experiment that was done between 1975 and 1990. In this experiment, radionuclide migration was induced from a small nuclear test conducted below the water table by pumping a well 91 m away. After radionuclides arrived at the pumping well, the contaminated effluent was discharged to an unlined ditch leading to a playa where it was expected to evaporate. However, recent data from a well near the ditch and results from detailed models of the experiment by LLNL personnel have convincingly demonstrated that radionuclides from the ditch eventually reached the water table some 220 m below land surface. The models presented in this paper combine aspects of these detailed models with concepts of basin-scale flow to estimate the likely extent of contamination resulting from this experiment over the next 1,000 years. The models demonstrate that because regulatory limits for radionuclide concentrations are exceeded only by tritium and the half-life of tritium is relatively short (12.3 years), the maximum extent of contaminated groundwater has or will soon be reached, after which time the contaminated plume will begin to shrink because of radioactive decay. The models also show that past and future groundwater pumping from water supply wells within Frenchman Flat basin will have negligible effects on the extent of the plume.

  6. Estimating groundwater recharge on a temperate humid to semiarid volcanic island (Jeju, Korea) from water table fluctuations, Cl mass balance, apparent CFC-12 ages and 3H renewal

    NASA Astrophysics Data System (ADS)

    Hagedorn, K. B.; El-Kadi, A. I.; Mair, A.; Whittier, R.

    2010-12-01

    Groundwater table fluctuations, Chloride mass balance, apparent groundwater Chlorofluorocarbon (CFC-12) ages and tritium (3H) renewal rates were used to assess recharge on Jeju Island (Korea), where groundwater is the main source of potable water. Given the limitations of various techniques and the respective data, the methods yield highly variable results of 10 to 1,991 mm/yr, with an average of 780 mm/yr that represents about 40% of the average annual rainfall over the island. The magnitude of recharge has not changed significantly over the past 50 years as indicated by an overall agreement of estimates for recent inter-seasonal recharge from the water table fluctuation method, and the long term average values from the geochemical techniques and the detailed water budget. Heterogeneity of recharge at the catchment scale is caused by spatially and temporally variable rainfall and evapotranspiration as well as the wide range in effective porosity and specific yield values of the aquifer lithologies. A Piston Flow model with negligible dispersion and diffusion fits 3H values for most groundwater samples. This implies that the mafic to intermediate volcanics exhibit fracture-hosted groundwater flow and that rapid recharge may be occurring in zones of interconnected porosity that represent a fraction of the total porosity. Calculated recharge rates that are generally highest (>1,000 mm/yr) in southern and eastern catchments and decrease with altitude indicate a strong control of topography and rainfall. However, since high recharge may occur across broad areas, attempts to protect groundwater from surface contamination require management of the landscape as a whole, not just the uplands. Increased recharge in western catchments (i.e., Hallim and Hangyeong) has not lowered groundwater nitrate contents due to the low effective porosities of the aquifers, where older nitrate-rich water is trapped in massive lava blocks within the unsaturated zone and is slowly mixed with groundwater as the water table rises.

  7. Karst groundwater management by defining protection zones based on regional geological structures and groundwater flow fields

    NASA Astrophysics Data System (ADS)

    Hao, Yonghong; Yeh, Tian-Chyi J.; Hu, Caihong; Wang, Yanrong; Li, Xia

    2006-06-01

    In a semiarid region, the karst aquifer generally forms a large groundwater reservoir that can play an important role in regional water supply. But because of the specific physical properties of karst aquifers, they are vulnerable to pollution and anthropogenic impacts. Karst groundwater management strategies are vital. As representative of karst springs in a semiarid area, Niangziguan Springs is located in the east of Shanxi Province, China with an annual average rate of discharge of 10.34 m3/s (1956 2003) (Y. Liang, unpublished data). The Niangziguan Spring Basin covers an area of 7,394 km2 with an annual average precipitation of 535 mm (1958 2003) (Hao et al. in Carsologica Sinica 23(1):43 47, 2004). Over the past three decades, accelerated groundwater exploitation has caused water-table decline in the aquifer, reduction of the spring discharge, and deterioration of water quality. In this study, three protection zones were defined to ensure the quality and capacity of this resource. The confluence of the 11 spring systems and the discharge areas were defined as I protection zone, the recharge basin was II protection zone, and the slack water area where there is little surface recharge was the III protection zone. Management strategies for each zone were suggested and evaluated to provide a scientific foundation for sustainable utilization.

  8. A theory for modeling ground-water flow in heterogeneous media

    USGS Publications Warehouse

    Cooley, Richard L.

    2004-01-01

    Construction of a ground-water model for a field area is not a straightforward process. Data are virtually never complete or detailed enough to allow substitution into the model equations and direct computation of the results of interest. Formal model calibration through optimization, statistical, and geostatistical methods is being applied to an increasing extent to deal with this problem and provide for quantitative evaluation and uncertainty analysis of the model. However, these approaches are hampered by two pervasive problems: 1) nonlinearity of the solution of the model equations with respect to some of the model (or hydrogeologic) input variables (termed in this report system characteristics) and 2) detailed and generally unknown spatial variability (heterogeneity) of some of the system characteristics such as log hydraulic conductivity, specific storage, recharge and discharge, and boundary conditions. A theory is developed in this report to address these problems. The theory allows construction and analysis of a ground-water model of flow (and, by extension, transport) in heterogeneous media using a small number of lumped or smoothed system characteristics (termed parameters). The theory fully addresses both nonlinearity and heterogeneity in such a way that the parameters are not assumed to be effective values. The ground-water flow system is assumed to be adequately characterized by a set of spatially and temporally distributed discrete values, ?, of the system characteristics. This set contains both small-scale variability that cannot be described in a model and large-scale variability that can. The spatial and temporal variability in ? are accounted for by imagining ? to be generated by a stochastic process wherein ? is normally distributed, although normality is not essential. Because ? has too large a dimension to be estimated using the data normally available, for modeling purposes ? is replaced by a smoothed or lumped approximation y?. (where y is a spatial and temporal interpolation matrix). Set y?. has the same form as the expected value of ?, y 'line' ? , where 'line' ? is the set of drift parameters of the stochastic process; ?. is a best-fit vector to ?. A model function f(?), such as a computed hydraulic head or flux, is assumed to accurately represent an actual field quantity, but the same function written using y?., f(y?.), contains error from lumping or smoothing of ? using y?.. Thus, the replacement of ? by y?. yields nonzero mean model errors of the form E(f(?)-f(y?.)) throughout the model and covariances between model errors at points throughout the model. These nonzero means and covariances are evaluated through third and fifth-order accuracy, respectively, using Taylor series expansions. They can have a significant effect on construction and interpretation of a model that is calibrated by estimating ?.. Vector ?.. is estimated as 'hat' ? using weighted nonlinear least squares techniques to fit a set of model functions f(y'hat' ?) to a. corresponding set of observations of f(?), Y. These observations are assumed to be corrupted by zero-mean, normally distributed observation errors, although, as for ?, normality is not essential. An analytical approximation of the nonlinear least squares solution is obtained using Taylor series expansions and perturbation techniques that assume model and observation errors to be small. This solution is used to evaluate biases and other results to second-order accuracy in the errors. The correct weight matrix to use in the analysis is shown to be the inverse of the second-moment matrix E(Y-f(y?.))(Y-f(y?.))', but the weight matrix is assumed to be arbitrary in most developments. The best diagonal approximation is the inverse of the matrix of diagonal elements of E(Y-f(y?.))(Y-f(y?.))', and a method of estimating this diagonal matrix when it is unknown is developed using a special objective function to compute 'hat' ?. When considered to be an estimate of f

  9. Characterization of the subregional ground-water flow system of a potential site for a high-level nuclear waste repository

    SciTech Connect

    Czarnecki, J.B.

    1988-12-31

    A study was performed to characterize the subregional ground-water flow system that includes Yucca Mountain, Nevada, the potential site of a high-level nuclear-waste repository. The study consisted of three parts: (1) The development of a finite-element parameter-estimation model of ground-water flow, from which sensitivity analyses of model variables were performed; (2) the characterization of the geohydrology and evapotranspiration at Franklin Lake playa; and (3) the simulation of the ground-water flow system under conditions of increased recharge. Evapotranspiration at Franklin Lake playa was determined to be the most sensitive of the discharge boundary conditions in the model. On-site estimates of evapotranspiration at Franklin Lake playa, estimated as a residual of the energy-balance equation ranged from 0.1 to 0.3 centimeters per day throughout the year, with an annual average of 0.16 centimeters per day. These estimates were compared with evapotranspiration estimates using: (1) Empirical relations of meteorological data to estimate potential evapotranspiration; (2) temporal variations in soil-moisture content in the unsaturated zone; (3) estimates of evapotranspiration by phreatophytes in climatically similar Owens and Santa Ana Valleys; (4) temperature profiles for the saturated zone; (5) a saturated-zone vertical gradients; and (6) a one-dimensional finite-difference model of vertical ground-water flow from the water table to land surface. Simulations of increased recharge showed a rise in water-table altitude of about 130 meters near the primary repository area at Yucca Mountain under conditions involving a 100-percent increase in precipitation compared to modern-day conditions. Despite the water-table rise, no flooding of the potential repository would occur at its current proposed location.

  10. Finite-element simulation of ground-water flow in the vicinity of Yucca Mountain, Nevada-California

    USGS Publications Warehouse

    Czarnecki, J.B.; Waddell, R.K.

    1984-01-01

    A finite-element model of the groundwater flow system in the vicinity of Yucca Mountain at the Nevada Test Site was developed using parameter estimation techniques. The model simulated steady-state ground-water flow occurring in tuffaceous, volcanic , and carbonate rocks, and alluvial aquifers. Hydraulic gradients in the modeled area range from 0.00001 for carbonate aquifers to 0.19 for barriers in tuffaceous rocks. Three model parameters were used in estimating transmissivity in six zones. Simulated hydraulic-head values range from about 1,200 m near Timber Mountain to about 300 m near Furnace Creek Ranch. Model residuals for simulated versus measured hydraulic heads range from -28.6 to 21.4 m; most are less than +/-7 m, indicating an acceptable representation of the hydrologic system by the model. Sensitivity analyses of the model 's flux boundary condition variables were performed to assess the effect of varying boundary fluxes on the calculation of estimated model transmissivities. Varying the flux variables representing discharge at Franklin Lake and Furnace Creek Ranch has greater effect than varying other flux variables. (Author 's abstract)

  11. Occurrence of Volcanic CO2 by Groundwater Flow Systems in the Eifel Mountains, Germany

    NASA Astrophysics Data System (ADS)

    Weyer, K.; May, F.; Ellis, J. C.

    2011-12-01

    Weyer (2010) showed why and how discharge areas of regional groundwater flow systems are also discharge points of natural and stored CO2. As groundwater flow systems reach to great depth by penetrating aquitards and caprocks any successful design of on-shore geological carbon storage must regard the migration effects groundwater flow systems exert on stored CO2. Eventually all of the CO2 will be dissolved by groundwater and migrate to the discharge areas of these flow systems. By implication there will rarely be the anticipated permanent storage of CO2 in the subsurface. Instead the deep ground water flow will transport the dissolved CO2 into surface waters. A telling example of such a system is the Green River in Utah with its natural discharge points of volcanic CO2 and the artificial discharge point Crystal Geyser, a flowing abandoned well located at the bank of the Green River. The advantage of this situation is that there have been hydrogeological tools developed which allow the determination of the flow path of the groundwater flow systems and their approximate time scale to reach their groundwater discharge areas. These time spans may be as large as 50,000 to 100,000 years. In any case residence times of a thousand years and more would suffice in mitigating the atmospheric effect of CO2 discharge. The above concepts have so far not created much resonance in the scientific and practical world of geologic CO2 storage. Therefore the investigation of groundwater dynamics at areas with natural discharge of volcanic CO2 provides a test for the effect groundwater flow systems will exert on the geologic storage of CO2. The Eifel Mountains in Germany present such a natural laboratory as it contains over a hundred known Tertiary and Quaternary volcanoes. Its discharge points of water carrying CO2 are well-known as they have been used for generations for the production of carbonated mineral waters. For the western part of the Eifel-Mountains, May (2002) listed all known natural CO2 discharge points with coordinates. The high resolution digital topographical maps of the area outline the elevation of the groundwater table in these mountains as the topography controls the elevation of the groundwater table. The detailed network of rivers, creeks and lakes denotes the location of groundwater discharge areas draining into the surface waters. Büchel and Mertens (1982) provided the locations of volcanic eruption centers in the western part of the Eifel Mountains. After combining the above information in a series of small scale DEMs created with 'SURFER' it became directly obvious that all known natural CO2 discharge points are directly related to discharge areas while the occurrence of volcanic eruption centers is concentrated in the recharge areas for regional groundwater flow. Quod erat demonstrandum. Büchel, G., H. Mertes (1982). Die Eruptionszentren des Westeifeler Vulkanfeldes. Zeitschr. DGG, 131: 409-429. May, Franz (2002). Säuerlinge der Vulkaneifel und der Südeifel. Mainzer geowissen. Mitt., 31: 7-58. Weyer, K. U. (2010). Differing physical processes in off-shore and on-shore CO2 storage. Private publication based on a poster presented at GHGT-10, Amsterdam. 8 pp, July 2010.

  12. 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 ofWest 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.

  13. Slope instability in complex 3D topography promoted by convergent 3D groundwater flow

    NASA Astrophysics Data System (ADS)

    Reid, M. E.; Brien, D. L.

    2012-12-01

    Slope instability in complex topography is generally controlled by the interaction between gravitationally induced stresses, 3D strengths, and 3D pore-fluid pressure fields produced by flowing groundwater. As an example of this complexity, coastal bluffs sculpted by landsliding commonly exhibit a progression of undulating headlands and re-entrants. In this landscape, stresses differ between headlands and re-entrants and 3D groundwater flow varies from vertical rainfall infiltration to lateral groundwater flow on lower permeability layers with subsequent discharge at the curved bluff faces. In plan view, groundwater flow converges in the re-entrant regions. To investigate relative slope instability induced by undulating topography, we couple the USGS 3D limit-equilibrium slope-stability model, SCOOPS, with the USGS 3D groundwater flow model, MODFLOW. By rapidly analyzing the stability of millions of potential failures, the SCOOPS model can determine relative slope stability throughout the 3D domain underlying a digital elevation model (DEM), and it can utilize both fully 3D distributions of pore-water pressure and material strength. The two models are linked by first computing a groundwater-flow field in MODFLOW, and then computing stability in SCOOPS using the pore-pressure field derived from groundwater flow. Using these two models, our analyses of 60m high coastal bluffs in Seattle, Washington showed augmented instability in topographic re-entrants given recharge from a rainy season. Here, increased recharge led to elevated perched water tables with enhanced effects in the re-entrants owing to convergence of groundwater flow. Stability in these areas was reduced about 80% compared to equivalent dry conditions. To further isolate these effects, we examined groundwater flow and stability in hypothetical landscapes composed of uniform and equally spaced, oscillating headlands and re-entrants with differing amplitudes. The landscapes had a constant slope for both headlands and re-entrants to minimize slope effects on stability. Despite these equal slopes, our analyses, given dry conditions, illustrated that the headlands can be 5-7% less stable than the re-entrants, owing to the geometry of the 3D failure mass with the lowest stability. We then simulated groundwater flow in these landscapes; flow was caused by recharge perching on a horizontal low permeability layer with discharge at the bluff faces. By systematically varying recharge, hydraulic conductivity of the material, and conductance at the bluffs, we created different 3D pore-pressure fields. Recharge rates and hydraulic conductivities controlled the height of the water table, whereas bluff conductance influenced the gradient of the water table near the bluff face. Given elevated water tables with steep gradients, bluffs in the re-entrants became unstable where flow converged. Thus, with progressively stronger effects from water flow, overall instability evolved from relatively unstable headlands to more uniform stability to relatively unstable re-entrants. Larger re-entrants led to more 3D flow convergence and greater localized instability. One- or two-dimensional models cannot fully characterize slope instability in complex topography.

  14. Temporal scaling of hydraulic head and river base flow and its implication for groundwater recharge

    USGS Publications Warehouse

    Zhang, Y.-K.; Schilling, K.

    2004-01-01

    Spectral analyses were conducted for hourly hydraulic head (h) data observed over a 4-year period at seven monitoring wells in the Walnut Creek watershed, Iowa. The log power spectral density of the hydraulic head fluctuations versus log frequency (f) at all seven wells is shown to have a distinct slope or fractal dimension (D), indicating temporal scaling in the time series of water level fluctuations. The fractal dimension of the time series varies from well to well, and the spectrum for the average h over all seven wells has a fractal dimension of 1.46 and Hurst coefficient of 0.54. The log power spectral density of estimated base flow in the Walnut Creek and four other watersheds versus log f is shown to have two distinct slopes with a break in scaling at about 30 days. It is shown that the groundwater recharge process in a basin can be estimated from a head spectrum based on existing theoretical results. Hydraulic head in an aquifer may fluctuate as a fractal in time in response to either a white noise or fractal recharge process, depending on physical parameters (i.e., transmissivity and specific yield) of the aquifer. The recharge process at the Walnut Creek watershed is shown to have a white noise spectrum based on the observed head spectrum.

  15. Improving the worthiness of the Henry problem as a benchmark for density-dependent groundwater flow models

    E-print Network

    Clement, Prabhakar

    Improving the worthiness of the Henry problem as a benchmark for density-dependent groundwater flow), Improving the worthiness of the Henry problem as a benchmark for density- dependent groundwater flow models January 2004. [1] This study considers the worthiness of the Henry saltwater intrusion problem as a test

  16. Effects of Karst and geological structure on groundwater flow: The case of Yarqon-Taninim Aquifer, Israel

    E-print Network

    Gvirtzman, Haim

    Effects of Karst and geological structure on groundwater flow: The case of Yarqon-Taninim Aquifer T. Simmons, Associate Editor Keywords: Judea Group Aquifer FEFLOW Yarqon-Taninim Karst Messinian of the geological structure (especially folding and lithology) and the karst system on groundwater flow regime

  17. Ground-water levels and flow near the industrial excess landfill, Uniontown, Ohio

    USGS Publications Warehouse

    Bair, E.S.; Norris, S.E.

    1989-01-01

    Under an interagency contractual agreement with the Agency for Toxic Substances and Disease Registration, the U.S. Geological Survey evaluated geologic and hydrogeologic data available for the Industrial Excess Landfill (IEL) site in Uniontown, Ohio. During previous studies, ground-water contaminations was detected in observation wells installed at the site and in residential wells near the site. Water levels recorded on drillers' logs from 279 wells were used to characterize the regional ground-water flow system in the area of the IEL site. On the basis of the gross lithologic differences between the unconsolidated glacial-drift material and the indurated bedrock, and the inferred differences in their hydraulic properties, the flow system in the area of the IEL site was divided into two regional aquifers: a shallow, unconfined glacial-drift aquifer and a deeper, semiconfined bedrock aquifer. About 33 percent of the drillers' logs were from wells completed in the glacial-drift aquifer, whereas 67 percent were from wells completed in the bedrock aquifer. A composite potentiometric-surface map of the glacial drift aquifer shows that the IEL site appears to straddle a prominent ground-water ridge that trends northeast-southwest. Ground water flows radially away from this ridge, primarily to the northwest and to the southeast; as a result flow in the glacial-drift aquifer as the IEL site moves in a radial pattern away from the site in all directions. A composite, regional potentiometric-surface map of the bedrock aquifer shows a similar shows a similar elongated ground-water ridge trending northeast-southwest across the north-western corner of the IEL site; however, it does not appear that the IEL site straddles the ground-water ridge in the bedrock potentiometric surface. As a consequence of the radial-type of flow pattern in the glacial-drift aquifer at the IEL site, the direction of potential off-site movement of a contaminant at the IEL site, This radial type of flow pattern may explain the nonuniform distribution of some of the contaminants detected in observation wells and residential wells, particularly if specific contaminants were not disposed of uniformly across the site. Available data also indicate a downward flow component within the glacial-drift aquifer, as manifested by a reduction of hydraulic heads with increasing depth of wells near the site. Such downward flow is consistent with the presence of the ground-water ridge, which would serve as a local recharge area within the regional flow system. Consequently, contaminants present at the site will flow both laterally within the local flow patterns and vertically downward within the flow system.

  18. Experimental and numerical modelling of surface water-groundwater flow and pollution interactions under tidal forcing

    NASA Astrophysics Data System (ADS)

    Spanoudaki, Katerina; Bockelmann-Evans, Bettina; Schaefer, Florian; Kampanis, Nikolaos; Nanou-Giannarou, Aikaterini; Stamou, Anastasios; Falconer, Roger

    2015-04-01

    Surface water and groundwater are integral components of the hydrologic continuum and the interaction between them affects both their quantity and quality. However, surface water and groundwater are often considered as two separate systems and are analysed independently. This separation is partly due to the different time scales, which apply in surface water and groundwater flows and partly due to the difficulties in measuring and modelling their interactions (Winter et al., 1998). Coastal areas in particular are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes. Accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands, for example, requires the use of integrated surface water-groundwater models. In the past few decades a large number of mathematical models and field methods have been developed in order to quantify the interaction between groundwater and hydraulically connected surface water bodies. Field studies may provide the best data (Hughes, 1995) but are usually expensive and involve too many parameters. In addition, the interpretation of field measurements and linking with modelling tools often proves to be difficult. In contrast, experimental studies are less expensive and provide controlled data. However, experimental studies of surface water-groundwater interaction are less frequently encountered in the literature than filed studies (e.g. Ebrahimi et al., 2007; Kuan et al., 2012; Sparks et al., 2013). To this end, an experimental model has been constructed at the Hyder Hydraulics Laboratory at Cardiff University to enable measurements to be made of groundwater transport through a sand embankment between a tidal water body such as an estuary and a non-tidal water body such as a wetland. The transport behaviour of a conservative tracer was studied for a constant water level on the wetland side of the embankment, while running a continuous tide on the coastal side. The integrated surface water-groundwater numerical model IRENE (Spanoudaki et al., 2009, Spanoudaki, 2010) was also used in the study, with the numerical model predictions being compared with experimental results, which provide a valuable database for model calibration and validation. IRENE couples the 3D, non-steady state Navier-Stokes equations, after Reynolds averaging and with the assumption of hydrostatic pressure distribution, to the equations describing 3D saturated groundwater flow of constant density. The model uses the finite volume method with a cell-centered structured grid providing thus flexibility and accuracy in simulating irregular boundary geometries. A semi-implicit finite difference scheme is used to solve the surface water flow equations, while a fully implicit finite difference scheme is used for the groundwater equations. Pollution interactions are simulated by coupling the advection-diffusion equation describing the fate and transport of contaminants introduced in a 3D turbulent flow field to the partial differential equation describing the fate and transport of contaminants in 3D transient groundwater flow systems. References Ebrahimi, K., Falconer, R.A. and Lin B. (2007). Flow and solute fluxes in integrated wetland and coastal systems. Environmental Modelling and Software, 22 (9), 1337-1348. Hughes, S.A. (1995). Physical Modelling and Laboratory Techniques in Coastal Engineering. World Scientific Publishing Co. Pte. Ltd., Singapore. Kuan, W.K., Jin, G., Xin, P., Robinson, C. Gibbes, B. and Li. L. (2012). Tidal influence on seawater intrusion in unconfined coastal aquifers. Water Resources Research, 48 (2), doi:10.1029/2011WR010678. Spanoudaki, K., Stamou, A.I. and Nanou-Giannarou, A. (2009). Development and verification of a 3-D integrated surface water-groundwater model. Journal of Hydrology, 375 (3-4), 410-427. Spanoudaki, K. (2010). Integrated numerical modelling of surface water groundwater systems (in Greek). Ph.D. Thesis, National Technical University of Athens, Greece. Sparks, T. D., Bockelmann-

  19. STATISTICAL ESTIMATION AND VISUALIZATION OF GROUND-WATER CONTAMINATION DATA

    EPA Science Inventory

    This work presents methods of visualizing and animating statistical estimates of ground water and/or soil contamination over a region from observations of the contaminant for that region. The primary statistical methods used to produce the regional estimates are nonparametric re...

  20. Study of electrokinetic effects to quantify groundwater flow

    SciTech Connect

    Brown, S.R.; Haupt, R.W.

    1997-04-01

    An experimental study of electrokinetic effects (streaming potential) in earth materials was undertaken. The objective was to evaluate the measurement of electrokinetic effects as a method of monitoring and predicting the movement of groundwater, contaminant plumes, and other fluids in the subsurface. The laboratory experiments verified that the electrokinetic effects in earth materials are prominent, repeatable, and can be described well to first order by a pair of coupled differential equations.

  1. Laboratory studies of groundwater degassing in replicas of natural fractured rock for linear flow geometry

    SciTech Connect

    Geller, J.T.

    1998-02-01

    Laboratory experiments to simulate two-phase (gas and water) flow in fractured rock evolving from groundwater degassing were conducted in transparent replicas of natural rock fractures. These experiments extend the work by Geller et al. (1995) and Jarsjo and Geller (1996) that tests the hypothesis that groundwater degassing caused observed flow reductions in the Stripa Simulated Drift Experiment (SDE). Understanding degassing effects over a range of gas contents is needed due to the uncertainty in the gas contents of the water at the SDE. The main objectives of this study were to: (1) measure the effect of groundwater degassing on liquid flow rates for lower gas contents than the values used in Geller for linear flow geometry in the same fracture replicas of Geller; (2) provide a data set to develop a predictive model of two-phase flow in fractures for conditions of groundwater degassing; and (3) improve the certainty of experimental gas contents (this effort included modifications to the experimental system used by Geller et al. and separate gas-water equilibration tests). The Stripa site is being considered for a high-level radioactive waste repository.

  2. The effects of regional groundwater flow in the thermal regime of a basin

    SciTech Connect

    Smith, Leslie; Chapman, David S.

    1982-09-01

    Numerical solutions of the equations of fluid flow and heat transport are used to quantify the effects of groundwater flow on the subsurface thermal regime. Simulations are carried out for a vertical section through a basin with a distance of 40 km separating the regional topographic high and low. Emphasis is placed on understanding the conditions under which advective effects significantly perturb the thermal field. The transition from conduction-dominated to advection-dominated thermal regimes is sharp and depends primarily on the topographic configuration of the water table, the magnitude and spatial distribution of permeability, hydraulic anisotropy and depth of active flow. Deviations of surface heat flow from the background heat flux are a measurable effect of groundwater flow and depend on the same factors. Our results show that from zero to almost one hundred per cent of the section may have surface heat flow significantly different from background heat flow, depending upon the nature of the hydrogeologic environment. A limited spatial variability in a distributed set of heat flow measurements and/or linear temperature-depth profiles does not ensure that surface heat flow measurements are not disturbed. The results of our simulations suggest that knowledge of the complete environment of a site, including the water table configuration and subsurface flow system, combined with more closely spaced heat flow measurements may be necessary to unravel the true background heat flux in active flow regions.

  3. ESTIMATION OF GROUNDWATER POLLUTION POTENTIAL BY PESTICIDES IN MID-ATLANTIC COASTAL PLAIN WATERSHEDS

    EPA Science Inventory

    A simple GIS-based transport model to estimate the potential for groundwater pollution by pesticides has been developed within the ArcView GIS environment. The pesticide leaching analytical model, which is based on one-dimensional advective-dispersive-reactive (ADR) transport, ha...

  4. Modeling of ground-water flow in subsurface Austin Chalk and Taylor marl in Ellis County, Texas, near the superconducting super collider site

    SciTech Connect

    Mace, R.E. . Bureau of Economic Geology)

    1993-02-01

    Numerical models are useful tools for developing an understanding of ground-water flow in sparsely characterized low-permeability aquifers. Finite-difference, cross-sectional models of Cretaceous chalk and marl formations near the Superconducting Super Collider (SSC) were constructed using MODFLOW to evaluate ground-water circulation paths and travel times. Weathered and fractured zones with enhanced permeability were included to assess the effect these features had on flow paths and times. Pump tests, slug tests, packer tests, core tests, and estimates were used to define hydraulic properties for model input. The model was calibrated with water-level data from monitor wells and from wire-line piezometers near a test shaft excavated by the SSC project. A ratio of vertical-to-horizontal permeability of 0.0085 was estimated through model calibration. A chalk-to-marl permeability ratio of 18 was needed to reproduce artesian head in a well completed in chalk beneath marl. Hydraulic head distributions and ground-water flow paths reflected local, intermediate, and regional flow systems with recharge beneath upland surface-water divides and discharge in valleys. Most of the flow (99%) occurred in the weathered zone, with average residence times of 5 to 10 years. Residence time in unweathered chalk bedrock was substantially longer, at an average of 1.7 Ma. As expected, the model demonstrated that deep and rapid ground-water circulation might occur in fracture zones. Particle paths calculated using MODPATH showed that ground-water travel times from recharge areas to the SSC subsurface facilities might be 20 to 60 years where flow is through fracture zones.

  5. A comparative analysis of groundwater recharge estimates from three major methods: An analysis of subsurface recharge in the Nabogo sub-catchment of the White Volta Basin, Northern Ghana

    NASA Astrophysics Data System (ADS)

    Fynn, O. F.; Yidana, S. M.; Alo, C. A.; Mensah, F. O.

    2013-12-01

    Groundwater recharge in the Nabogo sub-catchment of the White Volta Basin is assessed using three main methods: the water table fluctuations method, baseflow recession method, and chloride mass balance approach. The objective is to quantify the relative proportions of direct vertical infiltration and percolation of rainwater in the area and subsurface flows in determining the total groundwater recharge in the basin. Groundwater resources development for commercial irrigation activities is an essential aspect of the livelihoods of communities living within the catchments of the Volta Basin. A comprehensive assessment of the recharge component of groundwater budgets in the basin is critical towards determining optimal abstraction rates in order to ensure resource sustainability and ecological integrity. This will form the basis for quantifying abstraction rates that are permissible to support large scale irrigation activities in the basin. The presence and thickness of the clay layer in the unsaturated zone serves to limit vertical infiltration of rainwater, and thus reduce vertical groundwater recharge in the area. In this study, the chloride mass balance technique, supported by the analysis of stable isotope signatures, has been used to estimate the vertical groundwater recharge and its spatial pattern of distribution in the area. The water table fluctuations technique and base flow recession method are then used to estimate total groundwater recharge in the basin. It is then possible to quantify the relative contributions of subsurface flows in the groundwater recharge in the basin. Temporal variations in groundwater recharge in the area are examined from time series of estimates from the baseflow recession technique. The results will assist in assessing the short term impacts of rainfall variability on groundwater budgets in the area.

  6. Hydrology, water quality, and simulation of ground-water flow at a taconite-tailings basin near Keewatin, Minnesota. Water Resources Investigation

    SciTech Connect

    Myette, C.F.

    1991-01-01

    The purpose of the report is to describe the hydrology of a 2.5-sq mi taconite-tailings basin near Keewatin, Minnesota. The report describes (1) the hydrogeologic setting of the basin, including a description of the tailings within the basin, (2) the surface-water discharge at the outlet of the basin and its response to rainfall on the basin, (3) the ground-water system at the tailings basin and its response to rainfall on the basin, (4) the quality of the ground water beneath the basin and in the surrounding drift, (5) the quality of surface water and sediment discharging from the basin, and (6) the results of a finite-difference-model simulation of the ground-water flow system. Model simulation of ground-water flow was limited to deposits in the tailings basin and parts of the adjacent and underlying glacial-drift aquifers. The model was developed to evaluate estimates of hydraulic properties obtained from field data and to provide a better understanding of the effects of climatic stresses on ground-water levels and ground-water flow in the basin and on discharge from the basin. It has been suggested, however, that the filling and abandonment of these basins may create long-term pollution problems resulting from sediment erosion and chemical leaching of heavy metals.

  7. A comparison of estimates of basin-scale soil-moisture evapotranspiration and estimates of riparian groundwater evapotranspiration with implications for water budgets in the Verde Valley, Central Arizona, USA

    USGS Publications Warehouse

    Tillman, Fred; Wiele, Stephen M.; Pool, Donald R.

    2015-01-01

    Population growth in the Verde Valley in Arizona has led to efforts to better understand water availability in the watershed. Evapotranspiration (ET) is a substantial component of the water budget and a critical factor in estimating groundwater recharge in the area. In this study, four estimates of ET are compared and discussed with applications to the Verde Valley. Higher potential ET (PET) rates from the soil-water balance (SWB) recharge model resulted in an average annual ET volume about 17% greater than for ET from the basin characteristics (BCM) recharge model. Annual BCM PET volume, however, was greater by about a factor of 2 or more than SWB actual ET (AET) estimates, which are used in the SWB model to estimate groundwater recharge. ET also was estimated using a method that combines MODIS-EVI remote sensing data and geospatial information and by the MODFLOW-EVT ET package as part of a regional groundwater-flow model that includes the study area. Annual ET volumes were about same for upper-bound MODIS-EVI ET for perennial streams as for the MODFLOW ET estimates, with the small differences between the two methods having minimal impact on annual or longer groundwater budgets for the study area.

  8. "A space-time ensemble Kalman filter for state and parameter estimation of groundwater transport models"

    NASA Astrophysics Data System (ADS)

    Briseño, Jessica; Herrera, Graciela S.

    2010-05-01

    Herrera (1998) proposed a method for the optimal design of groundwater quality monitoring networks that involves space and time in a combined form. The method was applied later by Herrera et al (2001) and by Herrera and Pinder (2005). To get the estimates of the contaminant concentration being analyzed, this method uses a space-time ensemble Kalman filter, based on a stochastic flow and transport model. When the method is applied, it is important that the characteristics of the stochastic model be congruent with field data, but, in general, it is laborious to manually achieve a good match between them. For this reason, the main objective of this work is to extend the space-time ensemble Kalman filter proposed by Herrera, to estimate the hydraulic conductivity, together with hydraulic head and contaminant concentration, and its application in a synthetic example. The method has three steps: 1) Given the mean and the semivariogram of the natural logarithm of hydraulic conductivity (ln K), random realizations of this parameter are obtained through two alternatives: Gaussian simulation (SGSim) and Latin Hypercube Sampling method (LHC). 2) The stochastic model is used to produce hydraulic head (h) and contaminant (C) realizations, for each one of the conductivity realizations. With these realization the mean of ln K, h and C are obtained, for h and C, the mean is calculated in space and time, and also the cross covariance matrix h-ln K-C in space and time. The covariance matrix is obtained averaging products of the ln K, h and C realizations on the estimation points and times, and the positions and times with data of the analyzed variables. The estimation points are the positions at which estimates of ln K, h or C are gathered. In an analogous way, the estimation times are those at which estimates of any of the three variables are gathered. 3) Finally the ln K, h and C estimate are obtained using the space-time ensemble Kalman filter. The realization mean for each one of the variables is used as the prior space-time estimate for the Kalman filter, and the space-time cross-covariance matrix of h-ln K-C as the prior estimate-error covariance-matrix. The synthetic example has a modeling area of 700 x 700 square meters; a triangular mesh model with 702 nodes and 1306 elements is used. A pumping well located in the central part of the study area is considered. For the contaminant transport model, a contaminant source area is present in the western part of the study area. The estimation points for hydraulic conductivity, hydraulic head and contaminant concentrations are located on a submesh of the model mesh (same location for h, ln K and c), composed by 48 nodes spread throughout the study area, with an approximately separation of 90 meters between nodes. The results analysis was done through the mean error, root mean square error, initial and final estimation maps of h, ln K and C at each time, and the initial and final variance maps of h, ln K and C. To obtain model convergence, 3000 realizations of ln K were required using SGSim, and only 1000 with LHC. The results show that for both alternatives, the Kalman filter estimates for h, ln K and C using h and C data, have errors which magnitudes decrease as data is added. HERRERA, G. S.(1998), Cost Effective Groundwater Quality Sampling Network Design. Ph. D. thesis, University of Vermont, Burlington, Vermont, 172 pp. HERRERA G., GUARNACCIA J., PINDER G. Y SIMUTA R.(2001),"Diseño de redes de monitoreo de la calidad del agua subterránea eficientes", Proceedings of the 2001 International Symposium on Environmental Hydraulics, Arizona, U.S.A. HERRERA G. S. and PINDER G.F. (2005), Space-time optimization of groundwater quality sampling networks Water Resour. Res., Vol. 41, No. 12, W12407, 10.1029/2004WR003626.

  9. Parameter estimation and prediction for groundwater contamination based on measure theory

    NASA Astrophysics Data System (ADS)

    Mattis, S. A.; Butler, T. D.; Dawson, C. N.; Estep, D.; Vesselinov, V. V.

    2015-09-01

    The problem of groundwater contamination in an aquifer is one with many uncertainties. Properly quantifying these uncertainties is essential in order to make reliable probabilistic-based predictions and decisions regarding remediation strategies. In this work, a measure-theoretic framework is employed to quantify uncertainties in a simplified groundwater contamination transport model. Given uncertain data from observation wells, the stochastic inverse problem is solved numerically to obtain a probability measure on the space of unknown model parameters characterizing groundwater flow and contaminant transport in an aquifer, as well as unknown model boundary or source terms such as the contaminant source release into the environment. This probability measure is used to make predictions of future contaminant concentrations and to analyze possible remediation techniques. The ability to identify regions of small but nonzero probability using this method is illustrated.

  10. Ground-water levels and directions of flow near the Industrial Excess Landfill, Uniontown, Ohio, March 1994

    USGS Publications Warehouse

    Dumouchelle, D.H.; Bair, E.S.

    1994-01-01

    Industrial Excess Landfill (IEL), a U.S. Environmental Protection Agency Super-fund site, is a closed landfill in northeastern Ohio. In March 1994, personnel from the U.S. Geological Survey, Ohio Environmental Protection Agency, and PRC Environmental Management, Inc., measured water levels in 149 wells in the area. Surface-water altitudes were measured in 9 piezometers associated with the gages. The data show that the regional pattern of ground-water flow generally is from east to west, but it is locally altered by ground-water mounds that reflect the hummocky terrain. At the landfill, regional flow is altered by two ground-water mounds- one in the southeastern corner of the site and one just to the north. The relatively small ground-water mound at the landfill causes ground water to flow radially away from the southeastern corner of the landfill. Ground water that flows to east and south flows toward Metzger Ditch, whereas flow to the west is consistent with the regional direction of ground-water flow. Ground-water flow northward from IEL is diverted east or west by the southerly component of flow from the larger ground-water mound north of IEL.

  11. A Proposed Non-Intrusion Method for Estimating the Specific Yield for a Regional Groundwater System

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Cheng, C.; Chang, L.; Hwang, C.; Tsai, J.; Yeh, W.

    2013-12-01

    In Taiwan, groundwater resources play an important role in the management of regional water supply. However, because the lack of proper management over the last several decades, over-pumping of groundwater occurred, which resulted in serious land subsidence in the coastal areas. To properly manage the coastal aquifers, an accurately estimation of the specific yield (Sy) for the aquifer is needed. The traditional pumping test is costly. In this paper, we present a cost-saving, non-intrusive, geophysical method for estimating Sy. The method is based on gravity measurements and uses theories derived from geophysics. Because gravity variation is a function of the mass variation of materials, the gravity measurements correlate with the mass variation of the shallow groundwater in the neighborhood of the measurements. Comparing the groundwater level variations and gravity measurements between the droughts and flooding seasons, Sy can be interpreted. The proposed method combines MODFLOW with a numerical integration procedure that calculates the gravity variations. Heterogeneous parameters (Sy) can be assigned to MODFLOW cells. An inverse procedure is then applied to interpret and identify the Sy value around the gravity station. The proposed methodology is applied to the Choshui alluvial fan, one of the most important groundwater basins in Taiwan. Three gravity measurement stations, 'GS01', 'GS02' and 'GS03', were established. The location of GS01 is in the neighborhood of a groundwater observation well where pumping test data are available. The Sy value estimated from the gravitation measurements collected from GS01 compares favorably with that obtained from the traditional pumping test. The comparison verifies the correctness and accuracy of the proposed method. We then use the gravity measurements collected from GS02 and GS03 to estimate the Sy values in the areas where there exist no pumping test data. Using the estimated values obtained from gravity measurements, the spatial distribution of the values of specific yield for the aquifer can be further refined. The proposed method is a cost-saving and accuracy alternative for the estimation of specific yield in a regional groundwater system.

  12. Modelling of seasonal dynamics of Wetland-Groundwater flow interaction in the Canadian Prairies

    NASA Astrophysics Data System (ADS)

    Ali, Melkamu; Nussbaumer, Raphaël; Ireson, Andrew; Keim, Dawn

    2015-04-01

    Wetland-shallow groundwater interaction is studied at the St. Denis National Wildlife Area in Saskatchewan, Canada, located within the northern glaciated prairies of North America. Ponds in the Canadian Prairies are intermittently connected by fill-spill processes in the spring and growing season of some wetter years. The contribution of the ponds and wetlands to groundwater is still a significant research challenge. The objective of this study is to evaluate model's ability to reproduce observed effects of groundwater-wetland interactions including seasonal pattern of shallow groundwater table, intended flow direction and to quantify the depression induced infiltration from the wetland to the surrounding uplands. The integrated surface-wetland-shallow groundwater processes and the changes in land-energy and water balances caused by the flow interaction are simulated using ParFlow-CLM at a small watershed of 1km2 containing both permanent and seasonal wetland complexes. We compare simulated water table depth with piezometers reading monitored by level loggers at the watershed. We also present the strengths and limitations of the model in reproducing observed behaviour of the groundwater table response to the spring snowmelt and summer rainfall. Simulations indicate that the shallow water table at the uphill recovers quickly after major rainfall events in early summer that generates lateral flow to the pond. In late summer, the wetland supplies water to the surrounding upland when the evapotranspiration is higher than the precipitation in which more water from the root zone is up taken by plants. Results also show that Parflow-CLM is able to reasonably simulate the water table patterns response to summer rainfall, while it is insufficient to reproduce the spring snowmelt infiltration which is the most dominant hydrological process in the Prairies.

  13. 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.

  14. Groundwater Management Policies for Maintaining Stream Flow Given Variable Climatic Conditions

    NASA Astrophysics Data System (ADS)

    Pohll, G.; Carroll, R. W.; Brozovic, N.

    2012-12-01

    Groundwater is an important resource to agriculture throughout the semi-arid United States, where farmers often supplement surface water diversions with groundwater pumping. Understanding the complex exchange over space and time between rivers and aquifers is important in developing management alternatives that are capable of preserving stream flow for habitat and increasing water deliveries downstream while minimizing lost crop production. Previous integrated hydrologic-economic models have generally assumed superposition of the impacts of groundwater pumping on the hydrologic system for analytical tractability. Although this assumption may be reasonable for some surface water-groundwater systems, in many systems the behavior diverges considerably from the linear assumption. We present analyses using an integrated hydrologic-economic model of surface water-groundwater interaction with nonlinear dynamics, developed for the Mason Valley area in Nevada. The study area has active water conflict between upstream and downstream water users, where groundwater pumping has an important impact on streamflow. The model replicates the movement of water throughout the coupled river and aquifer of the Walker River system and is used to analyze hypothetical tradeoffs between increasing streamflow at the basin outlet and meeting crop water demands for irrigation. The model is run from 1997 to 2006 to capture wet and dry climatic conditions, including a four year drought period in which groundwater pumping accounts for more than 50% of the irrigated water budget. Three alternate groundwater management policies are analyzed to compare economic performance (resulting from reductions in crop area due to reduced groundwater pumping) and hydrologic impact (in terms of increased stream discharge at the basin outlet). First, uniform pumping quotas are the simplest policy to implement and are modeled here as equal reductions in groundwater pumping for each stakeholder at a lumped field scale. Second, targeted reductions in pumping are modeled in which reductions in pumping may vary between stakeholders to account for spatial variability in expected system dynamics. Third, dynamic targeted reductions that are allowed to vary annually are modeled, allowing policy responsiveness to both variable climate and nonlinearity of system dynamics. Optimization is done to maximize the volume of stream discharge increased per area of lost crop production for given rates of reduced groundwater pumping. We explore the extent to which increased complexity in policy - which is administratively costly to implement - improves cost-effectiveness relative to simpler policies. Moreover, we consider how nonlinear feedback in system response to reduced groundwater pumping may favor certain kinds of policies over others based on mandated regulatory objectives and climatic shifts.

  15. Constraining recharge and groundwater flow processes in hard-rock aquifers in temperate maritime climate using stable isotope signatures.

    NASA Astrophysics Data System (ADS)

    Pilatova, Katarina; Ofterdinger, Ulrich

    2015-04-01

    Recharge estimates and in understanding flow process in hard rock aquifers pose significant challenges. These arise from structural complexities of the hardrock aquifers and are further complicated by variability of the superficial cover. A comparative study of three metamorphic catchments situated in the North of Ireland is presented in this study, each with contrasting geology, glaciation history and consequently superficial cover. The presented study focusses on two main strains. Firstly, due to lack of existing records, stable water isotopes in precipitation (?18O and ?2H) were monitored at the research sites and their temporal and spatial variability was examined. Secondly, flow processes and dynamics of groundwater recharge based on continuous records of stable isotopes in groundwater, collected along catchment transects from various depths, and its variability in relation to the acquired precipitation signal were studied. Each precipitation station exhibited distinct isotopic signatures, where weather effect and proximity to coastline are the main controlling factors governing the isotope signatures. Moreover, in each of the stations the isotopic signature varied seasonally and thus stable isotopes proved a useful tool for assessing the dynamics of groundwater recharge. The analysis of isotope signatures in precipitation and groundwater from various depths within the hard rock aquifers allowed to evaluate the timescale of recharge, with rapid responses varying from few days up to several months. In general, the recharge appeared continuous over the hydrological year within wetter catchments with higher annual precipitation amounts purging the hardrock aquifers throughout the year. However, within comparatively dryer catchments recharge has a more seasonal character, predominantly taking place during the winter half of the year. Spatially, the recharge is highly localised within the elevated catchment areas, where superficial deposits are scarce and the bedrock is exposed. The study also suggests preferential recharge through faults that appear as conductive features. In all the catchments concerned, the precipitation signal was strongly attenuated with increasing depth, inferring the groundwater flow is strongly compartmentalised into a more rapid flow system within the shallow transition zone (decomposed bedrock) and into a much slower system within the underlying more competent bedrock.

  16. Spring temperatures in the Sagehen Basin, Sierra Nevada, CA: implications for heat flow and groundwater circulation

    E-print Network

    Manga, Michael

    Spring temperatures in the Sagehen Basin, Sierra Nevada, CA: implications for heat flow measurements at springs in Sagehen Basin, we find that groundwater removes the equivalent of approximately 20 discharged at the springs along with hourly temperature records in springs to provide constraints

  17. Appendix H: Past and Current Groundwater Flow and Contamination beneath Shell Tank Waste Management Areas

    SciTech Connect

    Horton, Duane G.

    2008-01-17

    This is being prepared as an appendix for CH2M HILL Hanford Group, Inc. and is part of PNNL support of the RCRA Facility Investigation Report. The document contains a detailed description of groundwater flow and contamination under the Central Plateau, emphasizing the areas around the tank farms.

  18. GROUND-WATER FLOW MODELING STUDY OF THE LOVE CANAL AREA, NEW YORK

    EPA Science Inventory

    As part of the overall Love Canal monitoring effort an assessment of the ground water hydrology of the Love Canal area, New York was performed. As part of this assessment, ground-water flow models were used to aid in well siting, data analysis and reduction, and prediction of gro...

  19. Estimating preferential flow in karstic aquifers using statistical mixed models.

    PubMed

    Anaya, Angel A; Padilla, Ingrid; Macchiavelli, Raul; Vesper, Dorothy J; Meeker, John D; Alshawabkeh, Akram N

    2014-01-01

    Karst aquifers are highly productive groundwater systems often associated with conduit flow. These systems can be highly vulnerable to contamination, resulting in a high potential for contaminant exposure to humans and ecosystems. This work develops statistical models to spatially characterize flow and transport patterns in karstified limestone and determines the effect of aquifer flow rates on these patterns. A laboratory-scale Geo-HydroBed model is used to simulate flow and transport processes in a karstic limestone unit. The model consists of stainless steel tanks containing a karstified limestone block collected from a karst aquifer formation in northern Puerto Rico. Experimental work involves making a series of flow and tracer injections, while monitoring hydraulic and tracer response spatially and temporally. Statistical mixed models (SMMs) are applied to hydraulic data to determine likely pathways of preferential flow in the limestone units. The models indicate a highly heterogeneous system with dominant, flow-dependent preferential flow regions. Results indicate that regions of preferential flow tend to expand at higher groundwater flow rates, suggesting a greater volume of the system being flushed by flowing water at higher rates. Spatial and temporal distribution of tracer concentrations indicates the presence of conduit-like and diffuse flow transport in the system, supporting the notion of both combined transport mechanisms in the limestone unit. The temporal response of tracer concentrations at different locations in the model coincide with, and confirms the preferential flow distribution generated with the SMMs used in the study. PMID:23802921

  20. COMPARISON OF METHODS FOR ESTIMATING GROUND-WATER PUMPAGE FOR IRRIGATION.

    USGS Publications Warehouse

    Frenzel, Steven A.

    1985-01-01

    Ground-water pumpage for irrigation was measured at 32 sites on the eastern Snake River Plain in southern Idaho during 1983. Pumpage at these sites also was estimated by three commonly used methods, and pumpage estimates were compared to measured values to determine the accuracy of each estimate. Statistical comparisons of estimated and metered pumpage using an F-test showed that only estimates made using the instantaneous discharge method were not significantly different ( alpha equals 0. 01) from metered values. Pumpage estimates made using the power consumption method reflect variability in pumping efficiency among sites. Pumpage estimates made using the crop-consumptive use method reflect variability in water-management practices. Pumpage estimates made using the instantaneous discharge method reflect variability in discharges at each site during the irrigation season.

  1. GEOCHEMICAL AND ISOTOPIC CONSTRAINTS ON GROUND-WATER FLOW DIRECTIONS, MIXING AND RECHARGE AT YUCCA MOUNTAIN, NEVADA

    SciTech Connect

    A. Meijer; E. Kwicklis

    2000-08-17

    This analysis is governed by the Office of Civilian Radioactive Waste Management (OCRWM) Analysis and Modeling Report Development Plan entitled ''Geochemical and Isotopic Constraints on Groundwater Flow Directions, Mixing and Recharge at Yucca Mountain'' (CRWMS M&O 1999a). As stated in this Development Plan, the purpose of the work is to provide an analysis of groundwater recharge rates, flow directions and velocities, and mixing proportions of water from different source areas based on groundwater geochemical and isotopic data. The analysis of hydrochemical and isotopic data is intended to provide a basis for evaluating the hydrologic system at Yucca Mountain independently of analyses based purely on hydraulic arguments. Where more than one conceptual model for flow is possible, based on existing hydraulic data, hydrochemical and isotopic data may be useful in eliminating some of these conceptual models. This report documents the use of geochemical and isotopic data to constrain rates and directions of groundwater flow near Yucca Mountain and the timing and magnitude of recharge in the Yucca Mountain vicinity. The geochemical and isotopic data are also examined with regard to the possible dilution of groundwater recharge from Yucca Mountain by mixing with groundwater downgradient from the potential repository site. Specifically, the primary tasks of this report, as listed in the AMR Development Plan (CRWMS M&O 1999a), consist of the following: (1) Compare geochemical and isotopic data for perched and pore water in the unsaturated zone with similar data from the saturated zone to determine if local recharge is present in the regional groundwater system; (2) Determine the timing of the recharge from stable isotopes such as deuterium ({sup 2}H) and oxygen-18 ({sup 18}O), which are known to vary over time as a function of climate, and from radioisotopes such as carbon-14 ({sup 14}C) and chlorine-36 ({sup 36}Cl); (3) Determine the magnitude of recharge from relatively conservative tracers such as chloride and/or groundwater age and unsaturated-zone thickness; (4) Correct {sup 14}C ages for possible dilution of radiocarbon by calcite fracture coatings using geochemical reaction models; and (5) Establish mixing relations between waters from different source areas using relatively conservative species such as {sup 2}H and {sup 18}O or chloride and sulfate, and evaluate if inferred flow paths and mixing relations are reasonable based on chemical reactions required to reproduce the observed water chemistry. The analysis presented in this report is appropriate for the intended use described above. This analysis is not directly related to the principal factors, or other factors, for the post-closure safety case, nor is it used directly in calculations or analyses that provide estimates of the effects of potentially disruptive processes and events, as described in AP-3.15Q, Managing Technical Product Inputs.

  2. Groundwater occurrence and flow patterns in the Ishiagu mining area of southeastern Nigeria

    NASA Astrophysics Data System (ADS)

    Ezekwe, I. C.; Odubo, E.; Chima, G. N.; Onwuchekwa, I. S.

    2012-03-01

    The Ishiagu area is a water scarce region and has played host to mining activities for more than four decades. Mining-related activities have become a threat to potable water supply in the area. This paper is an attempt to show the extent of this threat and in particular, investigate the regional groundwater occurrence and flow pattern based on GPS, water well and geological data. This basinwide model can be used for further groundwater assessment, pollution control and contaminant management. Groundwater occurs between 2.4 and 9 m in the Lekwesi-Lokpaukwu area; 1.5-3.7 m in the Ndi-Ugbugbor-Ayaragu axis and 1.2-4.6 m in the Ishiagu area. Recharge areas include the Leru-Amaubiri-Lekwesi sandstone hills and the Ihetutu-Ugwuajirija mine field. While the ultimate sink of contamiants is the Ivo River system, other discharge axis is the Ishiagu-Ayaragu axis and the Ogwor Ndi-Ugbugbor zone. An unconfined and a confined (>10) circulation groundwater system was inferred, and flow model reveals that a large part of Ishiag-Ayaragu and Ndi-Ugbugbor part of the study area suffer polluted recharge from the Pb/Zn mining area. Groundwater was also subjected to hierarchical cluster analysis and the existence of 3-4 hydrological regimes, which revealed: Unpolluted recharge areas, areas affected by polluted recharge, a deep water and shallow water circulation and mine effluents.

  3. Basin-scale conceptual groundwater flow model for an unconfined and confined thick carbonate region

    NASA Astrophysics Data System (ADS)

    Mádl-Sz?nyi, Judit; Tóth, Ádám

    2015-11-01

    Application of the gravity-driven regional groundwater flow (GDRGF) concept to the hydrogeologically complex thick carbonate system of the Transdanubian Range (TR), Hungary, is justified based on the principle of hydraulic continuity. The GDRGF concept informs about basin hydraulics and groundwater as a geologic agent. It became obvious that the effect of heterogeneity and anisotropy on the flow pattern could be derived from hydraulic reactions of the aquifer system. The topography and heat as driving forces were examined by numerical simulations of flow and heat transport. Evaluation of groups of springs, in terms of related discharge phenomena and regional chloride distribution, reveals the dominance of topography-driven flow when considering flow and related chemical and temperature patterns. Moreover, heat accumulation beneath the confined part of the system also influences these patterns. The presence of cold, lukewarm and thermal springs and related wetlands, creeks, mineral precipitates, and epigenic and hypogenic caves validates the existence of GDRGF in the system. Vice versa, groups of springs reflect rock-water interaction and advective heat transport and inform about basin hydraulics. Based on these findings, a generalized conceptual GDRGF model is proposed for an unconfined and confined carbonate region. An interface was revealed close to the margin of the unconfined and confined carbonates, determined by the GDRGF and freshwater and basinal fluids involved. The application of this model provides a background to interpret manifestations of flowing groundwater in thick carbonates generally, including porosity enlargement and hydrocarbon and heat accumulation.

  4. Groundwater-flow model and effects of projected groundwater use in the Ozark Plateaus Aquifer System in the vicinity of Greene County, Missouri - 1907-2030

    USGS Publications Warehouse

    Richards, Joseph M.

    2010-01-01

    Recent and historical periods of rapid growth have increased the stress on the groundwater resources in the Ozark aquifer in the Greene County, Missouri area. Historical pumpage from the Ozark aquifer has caused a cone of depression beneath Springfield, Missouri. In an effort to ease its dependence on groundwater for supply, the city of Springfield built a pipeline in 1996 to bring water from Stockton Lake to the city. Rapid population growth in the area coupled with the expanding cone of depression raised concern about the sustainability of groundwater as a resource for future use. A groundwater-flow model was developed by the U.S. Geological Survey in cooperation with Greene County, Missouri, the U. S. Army Corps of Engineers, and the Missouri Department of Natural Resources to assess the effect that increased groundwater demand is having on the long-term availability of groundwater in and around Greene County, Missouri. Three hydrogeologic units were represented in the groundwater-flow model: the Springfield Plateau aquifer, the Ozark confining unit, and the Ozark aquifer. The Springfield Plateau aquifer is less than 350 feet thick in the model area and generally is a low yield aquifer suitable only for domestic use. The Ozark aquifer is composed of a more than 900-foot thick sequence of dolomite and sandstone in the model area and is the primary aquifer throughout most of southern Missouri. Wells open to the entire thickness of the Ozark aquifer typically yield 1,000 gallons per minute or more. Between the two aquifers is the Ozark confining unit composed of as much as 98 feet of shale and limestone. Karst features such as sinkholes, springs, caves, and losing streams are present in both aquifers, but the majority of these features occur in the Springfield Plateau aquifer. The solution-enlarged fracture and bedding plane conduits in the karst system, particularly in the Springfield Plateau aquifer, are capable of moving large quantities of groundwater through the aquifer in relatively short periods of time. Pumpage rates in the model area increased from 1,093,268 cubic feet per day in 1962 to 2,693,423 cubic feet per day in 1987 to 4,330,177 cubic feet per day in 2006. Annual precipitation ranged from 25.21 inches in 1953 to 62.45 inches in 1927 from 1915 to 2006 in the model area. Recharge to the model was calculated as 2.53 percent of the annual precipitation and was varied annually. Recharge was distributed over the model area based on land slope and was adjusted in the city limits of Springfield to account for the impervious surface. A groundwater model with annual stress periods from 1907 to 2030 was developed using a transient calibration period from 1987 to 2006 and a prediction period from 2007 to 2030 to simulate flow in the Springfield Plateau aquifer and the Ozark aquifer. For the model area of approximately 2,870 square miles, the model hydrogeologic units and hydraulic properties were discretized into 253 rows, 316 columns, and 3 layers with the layer boundaries crossing hydrogeologic unit boundaries in some areas. The horizontal cell spacing was 1,000 feet by 1,000 feet. The model was calibrated by minimizing the difference between simulated head and observed water levels and simulated and observed flows in rivers and springs. Population and the associated groundwater use were estimated for 12 communities and the unincorporated area of Greene County based on past growth. Each was analyzed individually, and a low and high annual rate of growth relative to the 2006 population was computed for each community or group. Low growth rates ranged from 0.215 percent per year in Springfield to 6.997 percent per year in Rogersville. Total growth from 2006 to 2030 at the low growth rate ranged from 5.2 percent in Springfield to 167.9 percent in Rogersville. High growth rates ranged from 0.236 percent per year in Springfield to 7.345 percent per year in Rogersville. Total growth from 2006 to 2030 at the high g

  5. Estimating the radon emanation coefficient from crystalline rocks into groundwater.

    PubMed

    Przylibski, T A

    2000-09-01

    A simple method is proposed to estimate the coefficient of radon emanation from crystalline rocks into underground waters. In these cases, the crystalline rock seems as both the source and the reservoir of the radon. The calculations are based on a formula proposed by Maché for determining the concentration of radon in underground waters. Due to the inaccuracy of estimating some parameters (e.g. porosity), the results have a significant error. The advantage of this method is its simplicity and the possibility of obtaining results in a relatively short time. The estimated values of the emanation coefficient for selected crystalline rocks of the Sudety Mountains (SW Poland) vary from 7 to 41%, and after considering the error resulting from the estimation of rock porosity, saturation and density, the values range from 5 to 60%. The highest values of emanation coefficient (41, 33 and 21%) have been obtained for rocks in areas of tectonic dislocations and the lowest ones are for rocks outside dislocation zones (9 and 7%). The calculations imply that the emanation coefficient of rocks may have a greater influence on radon concentration in underground waters than the contents of radium in the reservoir rocks. PMID:10972156

  6. Ground-water levels and flow at selected study sites in the Walnut Creek Management System Evaluation Area, Boone and Story counties, Iowa, 1991-93

    USGS Publications Warehouse

    Buchmiller, Robert

    1996-01-01

    Data collected from May 1991 through September 1993 to determine seasonal fluctuations in ground-water levels and to estimate directions of ground-water flow in the saturated zone at selected study sites at the Iowa Management Systems Evaluation Area in the Walnut Creek watershed is presented. The Walnut Creek watershed is located on glacial deposits of Wisconsin Age in central Iowa and includes about 20 square miles. The upper glacial materials that contain the water table appear to be supraglacial till rather than basal glacial tills and contain both oxidized and unoxidized zones. A total of 102 observation wells were installed at 38 well nest locations. Descriptions of the observation wells drilled, the range of water-level fluctuation, and the estimated direction of ground-water movement at each of seven study sites in the watershed are provided. Diagrams of each study site show the location of observation wells and the estimated direction of ground-water flow for a selected date. Data tables include descriptive well logs, well-construction data, and water-level measaurements made between May 1991 and September 1993.

  7. Stratabound pathways of preferred groundwater flow: An example from the Copper Ridge Dolomite in East Tennessee

    SciTech Connect

    Lee, R.; Ketelle, D.

    1987-07-14

    The Copper Ridge Dolomite of the Upper Cambrian Knox Group underlies a site at Oak Ridge, Tennessee under consideration by the Department of Energy (DOE) for a below ground waste disposal facility. The Copper Ridge was studied for DOE to understand the influence of lithology on deep groundwater flow. Three facies types are distinguished which comprise laterally continuous, 1 to 4 m thick rock units interpreted to represent upward-shallowing depositional cycles having an apparently significant effect on groundwater flow at depth. Rock core observations indicate one of the recurring facies types is characterized by thin to medium-bedded, fine-grained dolostone with planar cryptalgal laminae and thin shaley partings. Distinctive fracturing in this facies type, that may have resulted from regional structural deformation, it considered to be responsible for weathering at depth and the development of stratabound pathways of preferred groundwater flow. In addition, geophysical data suggest that one occurrence of this weathered facies type coincides with an apparent geochemical interface at depth. Geophysical data also indicate the presence of several fluid invasion horizons, traceable outside the study area, which coincide with the unweathered occurrence of this fine-grained facies type. The subcropping of recurrent zones of preferred groundwater flow at the weathered/unweathered interface may define linear traces of enhanced aquifer recharge paralleling geologic strike. Vertical projection of these zones from the weathered/unweathered rock interface to the ground surface may describe areas of enhanced infiltration. Tests to determine the role of stratigraphic controls on groundwater flow are key components of future investigations on West Chestnut Ridge. 14 refs., 13 figs.

  8. Perched groundwater-surface interactions and their consequences in stream flow generation in a semi-arid headwater catchment

    NASA Astrophysics Data System (ADS)

    Molenat, Jerome; Bouteffeha, Maroua; Raclot, Damien; Bouhlila, Rachida

    2013-04-01

    In semi-arid headwater catchment, it is usually admitted that stream flow comes predominantly from Hortonian overland flow (infiltration excess overland flow). Consequently, subsurface flow processes, and especially perched or shallow groundwater flow, have not been studied extensively. Here we made the assumption that perched groundwater flow could play a significant role in stream flow generation in semi-arid catchment. To test this assumption, we analyzed stream flow time series of a headwater catchment in the Tunisian Cap Bon region and quantified the flow fraction coming from groundwater discharge and that from overland flow. Furthermore, the dynamics of the perched groundwater was analyzed, by focusing on the different perched groundwater-surface interaction processes : diffuse and local infiltration, diffuse exfiltration, and direct groundwater discharge to the stream channel. This work is based on the 2.6 km² Kamech catchment (Tunisia), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). Results show that even though Hortonian overland flow was the main hydrological process governing the stream flow generation, groundwater discharge contribution to the stream channel annually accounted for from 10% to 20 % depending on the year. Furthermore, at some periods, rising of groundwater table to the soil surface in bottom land areas provided evidences of the occurrence of saturation excess overland flow processes during some storm events. Reference Voltz , M. and Albergel , J., 2002. OMERE : Observatoire Méditerranéen de l'Environnement Rural et de l'Eau - Impact des actions anthropiques sur les transferts de masse dans les hydrosystèmes méditerranéens ruraux. Proposition d'Observatoire de Recherche en Environnement, Ministère de la Recherche.

  9. Large Scale Groundwater Flow Model for Ho Chi Minh City and its Catchment Area, Southern Vietnam

    NASA Astrophysics Data System (ADS)

    Sigrist, M.; Tokunaga, T.; Takizawa, S.

    2005-12-01

    Ho Chi Minh City (HCMC) has become a fast growing city in recent decades and is still growing at a high pace. The water demand for more than 7 million people has increased tremendously, too. Beside surface water, groundwater is used in big amounts to satisfy the need of water. By now, more than 200,000 wells have been developed with very little control. To investigate the sustainability of the water abstraction, a model had been built for the HCMC area and its surrounding. On the catchment scale (around 24,000km2); however, many questions have remained unsolved. In this study, we first gathered and complied geological and hydrogeological information as well as data on groundwater quality to get an idea on regional groundwater flow pattern and problems related to the temporal change of the groundwater situation. Two problems have been depicted by this study. One is the construction of a water reservoir upstream of the Saigon River. This construction has probably changed the water table of the unconfined aquifer, and hence, has significantly changed the properties of soils in some areas. The other problem is the distribution of salty groundwater. Despite the distance of more than 40km from the seashore, groundwater from some wells in and around HCMC shows high concentrations of chloride. Several wells started to produce non-potable water. The chloride concentrations show a complicated and patchy distribution below HCMC, suggesting the possibility of the remnant saltwater at the time of sediment deposition. On the other hand, seawater invades along the streams far beyond HCMC during the dry season and this might be one of the possible sources of salty groundwater by vertical infiltration. A large-scale geological model was constructed and transformed into a hydrogeological model to better understand and quantify the groundwater flow system and the origin of saltwater. Based on the constructed model and numerical calculation, we discuss the influence of reservoir construction on the groundwater situation at the upstream Saigon River, and possible factors for the existence of salty groundwater underneath HCMC.

  10. Application of nonlinear least-squares regression to ground-water flow modeling, west-central Florida

    USGS Publications Warehouse

    Yobbi, D.K.

    2000-01-01

    A nonlinear least-squares regression technique for estimation of ground-water flow model parameters was applied to an existing model of the regional aquifer system underlying west-central Florida. The regression technique minimizes the differences between measured and simulated water levels. Regression statistics, including parameter sensitivities and correlations, were calculated for reported parameter values in the existing model. Optimal parameter values for selected hydrologic variables of interest are estimated by nonlinear regression. Optimal estimates of parameter values are about 140 times greater than and about 0.01 times less than reported values. Independently estimating all parameters by nonlinear regression was impossible, given the existing zonation structure and number of observations, because of parameter insensitivity and correlation. Although the model yields parameter values similar to those estimated by other methods and reproduces the measured water levels reasonably accurately, a simpler parameter structure should be considered. Some possible ways of improving model calibration are to: (1) modify the defined parameter-zonation structure by omitting and/or combining parameters to be estimated; (2) carefully eliminate observation data based on evidence that they are likely to be biased; (3) collect additional water-level data; (4) assign values to insensitive parameters, and (5) estimate the most sensitive parameters first, then, using the optimized values for these parameters, estimate the entire data set.

  11. Coupled groundwater flow and transport: 1. Verification of variable density flow and transport models

    NASA Astrophysics Data System (ADS)

    Kolditz, Olaf; Ratke, Rainer; Diersch, Hans-Jörg G.; Zielke, Werner

    This work examines variable density flow and corresponding solute transport in groundwater systems. Fluid dynamics of salty solutions with significant density variations are of increasing interest in many problems of subsurface hydrology. The mathematical model comprises a set of non-linear, coupled, partial differential equations to be solved for pressure/hydraulic head and mass fraction/concentration of the solute component. The governing equations and underlying assumptions are developed and discussed. The equation of solute mass conservation is formulated in terms of mass fraction and mass concentration. Different levels of the approximation of density variations in the mass balance equations are used for convection problems (e.g. the Boussinesq approximation and its extension, fully density approximation). The impact of these simplifications is studied by use of numerical modelling. Numerical models for nonlinear problems, such as density-driven convection, must be carefully verified in a particular series of tests. Standard benchmarks for proving variable density flow models are the Henry, Elder, and salt dome (HYDROCOIN level 1 case 5) problems. We studied these benchmarks using two finite element simulators - ROCKFLOW, which was developed at the Institute of Fluid Mechanics and Computer Applications in Civil Engineering and FEFLOW, which was developed at the Institute for Water Resources Planning and Systems Research Ltd. Although both simulators are based on the Galerkin finite element method, they differ in many approximation details such as temporal discretization (Crank-Nicolson vs predictor-corrector schemes), spatial discretization (triangular and quadrilateral elements), finite element basis functions (linear, bilinear, biquadratic), iteration schemes (Newton, Picard) and solvers (direct, iterative). The numerical analysis illustrates discretization effects and defects arising from the different levels of the density of approximation. We contribute new results for the salt dome problem, for which inconsistent findings exist in literature. Applications of the verified numerical models to more complex problems, such as thermohaline and three-dimensional convection systems, will be presented in the second part of this paper.

  12. Ground truthing groundwater-recharge estimates derived from remotely sensed evapotranspiration: a case in South Australia

    NASA Astrophysics Data System (ADS)

    Crosbie, Russell S.; Davies, Phil; Harrington, Nikki; Lamontagne, Sebastien

    2015-03-01

    Using a water balance to estimate groundwater recharge through the use of remotely sensed evapotranspiration offers a spatial and temporal density of data that other techniques cannot match. However, the estimates are uncertain and therefore ground truthing of the recharge estimates is necessary. This study, conducted in the south-east of South Australia, demonstrated that the raw water-balance estimates of recharge had a negative bias of 45 mm/yr when compared to 190 recharge estimates using the water-table fluctuation method over a 10-year period (2001-2010). As this bias was not related to the magnitude of the recharge estimated using the water-table fluctuation method, a simple offset was used to bias-correct the water-balance recharge estimates. The bias-corrected recharge estimates had a mean residual that was not significantly different from an independent set of 99 historical recharge estimates but did have a large mean absolute residual indicating a lack of precision. The value in this technique is the density of the data (250-m grid over 29,000 km2). The relationship between the water-table depth and net recharge under different vegetation types was investigated. Under pastures, there was no relationship with water-table depth, as the shallow roots do not intercept groundwater. However, under plantation forestry, there was a relationship between net recharge and water-table depth. Net recharge under plantation forestry growing on sandy soils was independent of the water table at around 6 m depth but, under heavier textured soils, the trees were using groundwater from depths of more than 20 m.

  13. Analytical solutions to non-Fickian subsurface dispersion in uniform groundwater flow

    USGS Publications Warehouse

    Zou, S.; Xia, J.; Koussis, A.D.

    1996-01-01

    Analytical solutions are obtained by the Fourier transform technique for the one-, two-, and three-dimensional transport of a conservative solute injected instantaneously in a uniform groundwater flow. These solutions account for dispersive non-linearity caused by the heterogeneity of the hydraulic properties of aquifer systems and can be used as building blocks to construct solutions by convolution (principle of superposition) for source conditions other than slug injection. The dispersivity is assumed to vary parabolically with time and is thus constant for the entire system at any given time. Two approaches for estimating time-dependent dispersion parameters are developed for two-dimensional plumes. They both require minimal field tracer test data and, therefore, represent useful tools for assessing real-world aquifer contamination sites. The first approach requires mapped plume-area measurements at two specific times after the tracer injection. The second approach requires concentration-versus-time data from two sampling wells through which the plume passes. Detailed examples and comparisons with other procedures show that the methods presented herein are sufficiently accurate and easier to use than other available methods.

  14. Application of the Colloidal Borescope to Determine a Complex Groundwater Flow Pattern

    SciTech Connect

    Narbutovskih, Susan M.; McDonald, John P.; Schalla, Ronald; Sweeney, Mark D.; M.N. Sara and L.G. Everett

    2002-10-01

    Pacific Northwest National Laboratory made in situ flow measurements in groundwater monitoring wells at the U.S. Department of Energy (DOE) Hanford Site to determine the flow direction in an aquifer with a flat water table. Given the total errors in water level elevations, flow directions based on the potentiometric surface are ambiguous at best. The colloidal borescope was used because it allows direct, real time observation of mobile colloidal particles in the open interval of a water well and thus, avoids the use of water level data. The results characterize a complex groundwater flow pattern under several buried waste storage tank farms. The aquifer, artificially high due to large volume liquid discharges to the soil column from Hanford's nuclear production era, is currently receding to original conditions. The aquifer lies in unconsolidated gravel beds overlying an impermeable basalt surface that has a plucked, flood-scoured, scabland structure. The current aquifer thickness is similar to the relief on the basalt basement. Thus the groundwater must flow around the impermeable basalt structures producing a complicated flow pattern under the waste storage unit. The original monitoring network was designed for northwest flow when the water table was held artificially high. Proper locations for new wells are dependent on our knowledge of the flow direction. The results of the colloidal borescope investigation agree with the southerly direction indicated from hydrographs, contaminant trends, other direct flow data and the general concept of a receding aquifer draining off the southern limb of a basalt anticline. Flow in the aquifer is diverted by irregular local structural highs of very low permeability basalt.

  15. On methods of estimating cosmological bulk flows

    NASA Astrophysics Data System (ADS)

    Nusser, Adi

    2016-01-01

    We explore similarities and differences between several estimators of the cosmological bulk flow, B, from the observed radial peculiar velocities of galaxies. A distinction is made between two theoretical definitions of B as a dipole moment of the velocity field weighted by a radial window function. One definition involves the three-dimensional (3D) peculiar velocity, while the other is based on its radial component alone. Different methods attempt at inferring B for either of these definitions which coincide only for the case of a velocity field which is constant in space. We focus on the Wiener Filtering (WF) and the Constrained Minimum Variance (CMV) methodologies. Both methodologies require a prior expressed in terms of the radial velocity correlation function. Hoffman et al. compute B in Top-Hat windows from a WF realization of the 3D peculiar velocity field. Feldman et al. infer B directly from the observed velocities for the second definition of B. The WF methodology could easily be adapted to the second definition, in which case it will be equivalent to the CMV with the exception of the imposed constraint. For a prior with vanishing correlations or very noisy data, CMV reproduces the standard Maximum Likelihood estimation for B of the entire sample independent of the radial weighting function. Therefore, this estimator is likely more susceptible to observational biases that could be present in measurements of distant galaxies. Finally, two additional estimators are proposed.

  16. 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.

  17. Microsatellite Development and First Population Size Estimates for the Groundwater Isopod Proasellus walteri

    PubMed Central

    Capderrey, Cécile; Kaufmann, Bernard; Jean, Pauline; Malard, Florian; Konecny-Dupré, Lara; Lefébure, Tristan; Douady, Christophe J.

    2013-01-01

    Effective population size (Ne) is one of the most important parameters in, ecology, evolutionary and conservation biology; however, few studies of Ne in surface freshwater organisms have been published to date. Even fewer studies have been carried out in groundwater organisms, although their evolution has long been considered to be particularly constrained by small Ne. In this study, we estimated the contemporary effective population size of the obligate groundwater isopod: Proaselluswalteri (Chappuis, 1948). To this end, a genomic library was enriched for microsatellite motifs and sequenced using 454 GS-FLX technology. A total of 54,593 reads were assembled in 10,346 contigs or singlets, of which 245 contained candidate microsatellite sequences with suitable priming sites. Ninety-six loci were tested for amplification, polymorphism and multiplexing properties, of which seven were finally selected for Ne estimation. Linkage disequilibrium and approximate Bayesian computation methods revealed that Ne in this small interstitial groundwater isopod could reach large sizes (> 585 individuals). Our results suggest that environmental conditions in groundwater, while often referred to as extreme, are not necessarily associated with small Ne. PMID:24086709

  18. Simulation of Ground-Water Flow in the Irwin Basin Aquifer System, Fort Irwin National Training Center, California

    USGS Publications Warehouse

    Densmore, Jill N.

    2003-01-01

    Ground-water pumping in the Irwin Basin at Fort Irwin National Training Center, California resulted in water-level declines of about 30 feet from 1941 to 1996. Since 1992, artificial recharge from wastewater-effluent infiltration and irrigation-return flow has stabilized water levels, but there is concern that future water demands associated with expansion of the base may cause a resumption of water-level declines. To address these concerns, a ground-water flow model of the Irwin Basin was developed to help better understand the aquifer system, assess the long-term availability and quality of ground water, and evaluate ground-water conditions owing to current pumping and to plan for future water needs at the base. Historical data show that ground-water-level declines in the Irwin Basin between 1941 and 1996, caused the formation of a pumping depression near the pumped wells, and that recharge from the wastewater-treatment facility and disposal area caused the formation of a recharge mound. There have been two periods of water-level recovery in the Irwin Basin since the development of ground water in this basin; these periods coincide with a period of decreased pumpage from the basin and a period of increased recharge of water imported from the Bicycle Basin beginning in 1967 and from the Langford Basin beginning in 1992. Since 1992, artificial recharge has exceeded pumpage in the Irwin Basin and has stabilized water-level declines. A two-layer ground-water flow model was developed to help better understand the aquifer system, assess the long-term availability and quality of ground water, and evaluate ground-water conditions owing to current pumping and to plan for future water needs at the base. Boundary conditions, hydraulic conductivity, altitude of the bottom of the layers, vertical conductance, storage coefficient, recharge, and discharge were determined using existing geohydrologic data. Rates and distribution of recharge and discharge were determined from existing data and estimated when unavailable. Results of predictive simulations indicate that in 50 years, if artificial recharge continues to exceed pumpage in Irwin Basin, water levels could rise as much as 65 feet beneath the pumping depression, and as much as 10 feet in the wastewater-treatment facility and disposal area. Particle-tracking simulations were used to determine the pathlines and the traveltimes of water high in dissolved solids into the main pumping area. The pathlines of particles from two areas with high dissolved-solids concentrations show that in 50 years water from these areas almost reaches the nearest pumped well.

  19. Application of a groundwater flow model for real-time well field management - lessons learned

    NASA Astrophysics Data System (ADS)

    Marti, B.; Kaiser, H.-P.; Kuhlmann, U.; Hendricks Franssen, H.-J.; Kinzelbach, W.

    2012-04-01

    The Hardhof well field, which lies in the city of Zurich, Switzerland, provides roughly 15 % of the towns drinking water demand from the Limmat valley aquifer. Groundwater and river filtrate are withdrawn in four large horizontal wells, each with a capacity of up to 48'000 m3 per day. The well field is threatened by potential pollution from leachate of a nearby land fill, possible accidents on the adjacent rail and road lines, and by diffuse pollution from former industrial sites and sewers located upstream of the well field. A line of recharge wells and basins forms a hydraulic barrier against the potentially contaminated water and increases the capacity of the well field. Currently, a genetic algorithm coupled to a 3-dimensional groundwater flow model is applied at the well field to determine optimal infiltration rates on a daily basis. This real-time control is based on particle backtracking in a quasi-stationary flow field. It estimates the origin of the water in the four horizontal wells and calculates the amount of potentially contaminated water in each well. Running the model iteratively and refining the parameters of the genetic algorithm at the end of each step yields the recommended daily infiltration rates. The current model accurately predicts the change of piezometric head due to changes in the river stage. However, during periods of large abstraction rates, the model underestimates the piezometric heads in the Hardhof area. In addition, the infiltration rates suggested by the control do not always agree with the experience of the Zurich water works (e.g. during periods with large abstraction rates) and hence the actually applied infiltration rates are sometimes chosen differently from the calculated ones. This work analyzes the performance of the model and the control during the year 2011. The computed heads of the on-line model are compared to the measured piezometric heads in over 80 measurement locations in the model area. Furthermore, differences between the computed management decisions and the actual management decisions are analyzed and suggestions for an improved management are made.

  20. Model-derived estimates of groundwater mean ages, recharge rates, effective porosities and storage in a limestone aquifer

    NASA Astrophysics Data System (ADS)

    Campana, M. E.; Mahin, D. A.

    1985-02-01

    The Edwards aquifer of south-central Texas, U.S.A., a highly fractured and faulted group of limestone formations, is the major water supply for the San Antonio area. A discrete-state compartment (DSC) model or mixing-cell model, based upon the conservation of environmental tritium within the aquifer, was used to obtain estimates of groundwater mean ages, recharge, effective porosities and storage in the Edwards aquifer in the vicinity of San Antonio, Texas. The model was calibrated and validated with the spatial and temporal (1953-1971) distributions of environmental 3H (tritium) in the groundwater. The final model consisted of 34 cells; eight of these cells represented the unconfined portion of the Edwards aquifer in the vicinity of the Balcones fault zone, an area where recharge occurs via streamflow infiltration and direct infiltration of precipitation. The model confirmed previous analyses of flow in the Edwards system: generally parallel to the Balcones fault zone with restricted flow perpendicular to this zone. Groundwater mean ages ranged from 16 to over 130 yr. The storage volume of the confined portion of the Edwards aquifer is ˜ 30.9 km 3, which corresponds to an average effective porosity of 4.8% (range: 1.9-8%). The average annual recharge to the Edwards aquifer during the period 1953-1971 was 0.614 km 3. The study demonstrated that discrete-state compartment models calibrated and validated with environmental tritium distributions can yield valuable hydrogeologic information that is difficult or expensive to obtain using traditional techniques. The approach used in the study is particularly suited to limestone aquifers, which are normally extremely difficult to analyze with traditional methods.

  1. Analysis of the shallow groundwater flow system near Connetqout Brook, Long Island, New York

    USGS Publications Warehouse

    Prince, K.R.; Reilly, T.E.; Franke, O.L.

    1989-01-01

    Streamflow on Long Island is derived principally from shallow groundwater that flows above the deeper regional flow system. The movement of shallow groundwater was studied during 1975-1982 at Connetquot Brook - an undisturbed stream in Connetquot River State Park - in south-central Long Island. The investigation encompassed: (1) field studies of streamflow, groundwater levels, and age of water as indicated by tritium concentrations, and (2) numerical simulation of the shallow flow system to evaluate the hydraulic factors that influence groundwater flow near and beneath the stream. Analysis of water-level data indicates that groundwater flow is essentially horizontal throughout the drainage basin except near and beneath the stream, where it moves upward diagonally and discharges into the streambank at three sites were 1-2 ft higher than stream stage in the and in wells driven into the streambank at three sites were 1-2 ft higher than stream stage in the first 5 ft of penetration. Increases in head, which were detected to depths of 30 ft beneath the streambed, indicate upward movement of water above that depth. Water samples from selected wells were analyzed for tritium concentration to determine the relative age of water to locate the bottom boundary of the shallow flow system. Tritium concentrations indicate that the lower boundary is from 45 to 100 ft below the water table. A two-dimensional cross-sectional flow model of the shallow flow system indicated that: (1) stream width and streambed hydraulic conductivity influence heads mostly within about 50 ft of the stream; (2) the thickness of the shallow flow system influences heads more distant from the stream but has a negligible effect near the stream; and (3) the quantity of water entering the system as recharge from precipitation influences the heads throughout the area. Field measurements of hydraulic head indicate the shallow flow system to extend to about 30 ft below the stream channel. Results of the sensitivity analysis indicate that the thickness of the shallow system has a negligible effect on head distribution beneath the stream. ?? 1989.

  2. Comparison of ground-water flow model particle-tracking results and isotopic data in the Mojave River ground-water basin, southern California, USA

    USGS Publications Warehouse

    Izbicki, J.A.; Stamos, C.L.; Nishikawa, T.; Martin, P.

    2004-01-01

    Flow-path and time-of-travel results for the Mojave River ground-water basin, southern California, calculated using the ground-water flow model MODFLOW and particle-tracking model MODPATH were similar to flow path and time-of-travel interpretations derived from delta-deuterium and carbon-14 data. Model and isotopic data both show short flow paths and young ground-water ages throughout the floodplain aquifer along most the Mojave River. Longer flow paths and older ground-water ages as great as 10,000 years before present were measured and simulated in the floodplain aquifer near the Mojave Valley. Model and isotopic data also show movement of water between the floodplain and regional aquifer and subsequent discharge of water from the river to dry lakes in some areas. It was not possible to simulate the isotopic composition of ground-water in the regional aquifer away from the front of the San Gabriel and San Bernardino Mountains - because recharge in these areas does not occur under the present-day climatic conditions used for calibration of the model.

  3. Groundwater flow and tritium migration from the SRS Old Burial Ground to Fourmile Branch

    SciTech Connect

    Flach, G.P.; Hamm, L.L.; Harris, M.K.

    1996-04-01

    The objectives of this investigation are twofold. The initial goal is to devise and demonstrate a technique for directly incorporating fine-scale lithologic data into heterogeneous hydraulic conductivity fields, for improved groundwater flow and contaminant transport model accuracy. The ultimate goal is to rigorously simulate past and future tritium migration from the SRS Old Burial Ground towards Fourmile Branch, to better understand the effects of various remediation alternatives such as no action and capping. Large-scale variability in hydraulic conductivity is usually the main influence on field-scale groundwater flow patterns and dispersive transport, following the relative locations of recharge and discharge areas. Incorporating realistic hydraulic conductivity heterogeneity into flow and transport models is paramount to accurate simulations, particularly for contaminant migration. Sediment lithologic descriptions and geophysical logs typically offer finer spatial resolution, and therefore more potential information about heterogeneity, than other site characterization data.

  4. A preliminary evaluation of regional ground-water flow in south-central Washington

    USGS Publications Warehouse

    La Sala, A. M., Jr.; Doty, G.C.; Pearson, F.J., Jr.

    1973-01-01

    The characteristics of regional ground-water flow were investigated in a 4,500-square-mile region of south-central Washington, centered on the U.S. Atomic Energy Commission Hanford Reservation. The investigation is part of the Commission's feasibility study on storing high-level radioactive waste in chambers mined in basaltic rocks at a. depth of about 3,000 feet or more below the surface. Ground-water flow., on a regional scale, occurs principally in the basalt and-in interbedded sediments of the Columbia River Group, and is controlled by topography, the structure of the basalt, and the large streams--the Columbia, Snake, and Yakima Rivers. The ground water beneath the main part of the Hanford Reservation, south and west of the Columbia River, inures southeastward from recharge areas in the uplands, including Cold Creek and Dry Creek valleys, and ultimately discharges to the Columbia River south of the reservation: East and southeast of the Columbia River, ground water flows generally southwestward and discharges to the River. The Yakima River valley contains a distinct flow system in which movement is toward the Yakima River from the topographic divides. A large southward-flowing ground-water system beneath the southern flank of the Horse Heaven Hills discharges to the Columbia River in the westward-trending reach downstream from Wallula Gap.

  5. Temporal evolution of soil moisture statistical fractal and controls by soil texture and regional groundwater flow

    NASA Astrophysics Data System (ADS)

    Ji, Xinye; Shen, Chaopeng; Riley, William J.

    2015-12-01

    Soil moisture statistical fractal is an important tool for downscaling remotely-sensed observations and has the potential to play a key role in multi-scale hydrologic modeling. The fractal was first introduced two decades ago, but relatively little is known regarding how its scaling exponents evolve in time in response to climatic forcings. Previous studies have neglected the process of moisture re-distribution due to regional groundwater flow. In this study we used a physically-based surface-subsurface processes model and numerical experiments to elucidate the patterns and controls of fractal temporal evolution in two U.S. Midwest basins. Groundwater flow was found to introduce large-scale spatial structure, thereby reducing the scaling exponents (?), which has implications for the transferability of calibrated parameters to predict ?. However, the groundwater effects depend on complex interactions with other physical controls such as soil texture and land use. The fractal scaling exponents, while in general showing a seasonal mode that correlates with mean moisture content, display hysteresis after storm events that can be divided into three phases, consistent with literature findings: (a) wetting, (b) re-organizing, and (c) dry-down. Modeling experiments clearly show that the hysteresis is attributed to soil texture, whose "patchiness" is the primary contributing factor. We generalized phenomenological rules for the impacts of rainfall, soil texture, groundwater flow, and land use on ? evolution. Grid resolution has a mild influence on the results and there is a strong correlation between predictions of ? from different resolutions. Overall, our results suggest that groundwater flow should be given more consideration in studies of the soil moisture statistical fractal, especially in regions with a shallow water table.

  6. 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

  7. Characterization of Groundwater Flow at a Mountainous Watershed, Niwot Ridge, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Evans, S. G.; Ge, S.

    2013-12-01

    We present a 3D coupled flow and solute transport hydrogeologic model for the Niwot Ridge Watershed in the Front Range of Colorado. This is the first 3D modeling attempt at detailing groundwater recharges at this site. The 7.6 km2 watershed ranges in elevation from 3241 to 4082 m and is representative of an alpine setting. Its climate is characterized by a mean annual precipitation of 1.95 m, mean annual air temperature of -2.1 °C, and extensive snow coverage six months of the year with 80% of the precipitation falling as snow. At the study site, Proterozoic metamorphic and igneous bedrock is intruded by Tertiary stocks and overlain by Quaternary deposits. In the middle of the watershed are six paternoster lakes connected by North Boulder Creek, the headwaters of the South Platte River. We use a steady state 3D finite element coupled flow and solute transport model to characterize the groundwater and solute transport systems and quantify mountain recharge under averaged long-term conditions. Field data including effective porosity, hydraulic conductivity, and solute concentration in surface water are utilized to constrain and calibrate model parameters. We conduct model sensitivity analysis to examine how uncertainties in model input parameters may influence model results. Preliminary model results indicate that regional groundwater flow is from northwest to southeast, towards North Boulder Creek. This groundwater flow pattern is consistent with field observations. The average hydraulic head gradient over the entire modeled area is approximately 0.12 m/m. Groundwater velocity varies from 1.4 x 10-6 to 1.8 x 10-3 m/s. Groundwater flow is primarily driven by a topographically influenced precipitation regime, with 7% of the total precipitation recharging into the subsurface. Groundwater contribution to baseflow of North Boulder Creek is at an average rate of 0.03 m3/s, which is on the same magnitude as observed values. Modeled discharge solute concentration (Na+) output values corroborate with observed surface water values. On the surface, solute concentration is lowest at high elevations and increases as elevation decreases, with the highest concentrations bordering lake shores within the watershed. Lithology and associated hydraulic conductivity appear to have a primary control on solute concentration, as areas with Tertiary stocks and relatively low conductivity values have lower solute concentrations in surface waters.

  8. Local Modelling of Groundwater Flow Using Analytic Element Method Three-dimensional Transient Unconfined Groundwater Flow With Partially Penetrating Wells and Ellipsoidal Inhomogeneites

    NASA Astrophysics Data System (ADS)

    Jankovic, I.; Barnes, R. J.; Soule, R.

    2001-12-01

    The analytic element method is used to model local three-dimensional flow in the vicinity of partially penetrating wells. The flow domain is bounded by an impermeable horizontal base, a phreatic surface with recharge and a cylindrical lateral boundary. The analytic element solution for this problem contains (1) a fictitious source technique to satisfy the head and the discharge conditions along the phreatic surface, (2) a fictitious source technique to satisfy specified head conditions along the cylindrical boundary, (3) a method of imaging to satisfy the no-flow condition across the impermeable base, (4) the classical analytic solution for a well and (5) spheroidal harmonics to account for the influence of the inhomogeneities in hydraulic conductivity. Temporal variations of the flow system due to time-dependent recharge and pumping are represented by combining the analytic element method with a finite difference method: analytic element method is used to represent spatial changes in head and discharge, while the finite difference method represents temporal variations. The solution provides a very detailed description of local groundwater flow with an arbitrary number of wells of any orientation and an arbitrary number of ellipsoidal inhomogeneities of any size and conductivity. These inhomogeneities may be used to model local hydrogeologic features (such as gravel packs and clay lenses) that significantly influence the flow in the vicinity of partially penetrating wells. Several options for specifying head values along the lateral domain boundary are available. These options allow for inclusion of the model into steady and transient regional groundwater models. The head values along the lateral domain boundary may be specified directly (as time series). The head values along the lateral boundary may also be assigned by specifying the water-table gradi