Sample records for estimate groundwater flow

  1. Estimation of Groundwater Flow Parameters Using Least Squares

    E-print Network

    in a groundwater aquifer is estimation of the subsurface physical pa­ rameters, particularly the hydraulic conductivity. Wells are expensive to drill, and the cost of time, equipment and manpower to make accurate ; (1) hj @\\Omega = g where K is the hydraulic conductivity, h is the hydraulic head, g represents

  2. Estimating groundwater recharge through unsaturated flow modelling: Sensitivity to boundary conditions and vertical discretization

    NASA Astrophysics Data System (ADS)

    Carrera-Hernández, J. J.; Smerdon, B. D.; Mendoza, C. A.

    2012-07-01

    SummaryUnsaturated flow modelling is increasingly being used to estimate potential groundwater recharge. A review of previous studies found that unit-gradient and fixed water table lower boundary conditions have been applied to models of both constant and variable vertical grid spacing (discretization). In order to provide a general guidance, this work studies the effect of both discretization and boundary conditions on simulation times and estimated fluxes at the water table, using one-dimensional models of 2, 4, 6, and 12 m comprised of sand, sandy loam, loamy sand, and loam. The study uses climatological data from the Boreal Plain of northern Alberta, Canada. Because of the long-term average water deficit and the thick unconsolidated glacial deposits, unsaturated flow is expected to be vertical, both downward and upward, and inter-annual changes in water storage will be important. Long-term simulations (1919-2007) that comprised both wet and dry cycles, reveal that when a variable vertical discretization at both the top and bottom of the columns (varying from 0.1 to 10 cm) is utilized, a balance between simulation accuracy and running time can be achieved. It is also found that whenever the unsaturated flow modelling approach is used to estimate potential groundwater recharge, a fixed-head lower boundary condition should be selected because it also allows upward flux from the water table during dry periods, a situation that prevails on both sub-humid and semi-arid areas, where accurate groundwater recharge estimates are needed the most. However, it should be kept in mind that the use of a fixed water table is a simple representation of the regional water table, which in reality interacts with the regional groundwater flow and surface water bodies (e.g., lakes and wetlands).

  3. 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.

  4. Recharge sources and flow system of groundwaters in Osaka Basin, estimated from environmental isotopes and water chemistry

    NASA Astrophysics Data System (ADS)

    Nakaya, Shinji; Mitamura, Muneki; Masuda, Harue; Uesugi, Kenji; Motodate, Yusuke; Kusakabe, Minoru; Iida, Tomoyuki; Muraoka, Kohji

    Spatial distributions of stable isotopic ratios of oxygen and hydrogen, tritium concentrations, concentrations of nitrate-nitrogen and major water chemistry were investigated for the groundwaters shallower than -300m below sea level in the Osaka Basin in relation to groundwater tables, topography and hydrogeology to clarify the recharge sources and flow fields. The stable isotopic ratios of oxygen and hydrogen of groundwaters documented that groundwaters were recharged at the surrounding mountains, hills and plateaus of the Basin, and that the groundwaters transported nitric acids to -300m depth below the basin through aquifers. The flow velocities of recharge and migration through the aquifers are estimated roughly to be 2-9m/y and 0.1-1km/y in vertical and horizontal directions, respectively, in several recharge zones.

  5. 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.

  6. 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.

  7. Estimates of ground-water recharge, base flow, and stream reach gains and losses in the Willamette River basin, Oregon

    USGS Publications Warehouse

    Lee, Karl K.; Risley, John C.

    2002-01-01

    Precipitation-runoff models, base-flow-separation techniques, and stream gain-loss measurements were used to study recharge and ground-water surface-water interaction as part of a study of the ground-water resources of the Willamette River Basin. The study was a cooperative effort between the U.S. Geological Survey and the State of Oregon Water Resources Department. Precipitation-runoff models were used to estimate the water budget of 216 subbasins in the Willamette River Basin. The models were also used to compute long-term average recharge and base flow. Recharge and base-flow estimates will be used as input to a regional ground-water flow model, within the same study. Recharge and base-flow estimates were made using daily streamflow records. Recharge estimates were made at 16 streamflow-gaging-station locations and were compared to recharge estimates from the precipitation-runoff models. Base-flow separation methods were used to identify the base-flow component of streamflow at 52 currently operated and discontinued streamflow-gaging-station locations. Stream gain-loss measurements were made on the Middle Fork Willamette, Willamette, South Yamhill, Pudding, and South Santiam Rivers, and were used to identify and quantify gaining and losing stream reaches both spatially and temporally. These measurements provide further understanding of ground-water/surface-water interactions.

  8. 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.

  9. 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.

  10. Groundwater Flow Model

    NSDL National Science Digital Library

    Alex Manda

    Students will work in groups to make observations, identify aquifers, describe aquifer properties and measure hydraulic head in a physical groundwater flow model. The information collected will be used to answer questions pertaining to the groundwater flow system. The activity serves to consolidate the key concepts covered in lecture materials. These concepts include the water cycle, hydraulic head, types of aquifers, hydraulic conductivity, permeability, Darcy's Law, hydraulic gradient, porosity and groundwater contamination.

  11. Scarce water resources and scarce data: Estimating recharge for a complex 3D groundwater flow model in arid regions

    NASA Astrophysics Data System (ADS)

    Gräbe, A. C.; Guttman, J.; Rödiger, T.; Siebert, C.; Merz, R.; Kolditz, O.

    2012-12-01

    Semi-arid to arid regions are usually characterized by a scarcity of precipitation and a lack of stream flow. Especially in desert environments, groundwater is one of the most important fresh water sources and its recharge is basically controlled by two main mechanisms: the direct regional infiltration of precipitation in the mountains and interdrainage areas in the first place and secondly the flood water infiltration through ephemeral channel beds (transmission loss). Due to extensive spatio-temporal data scarcity, direct quantitative estimations of groundwater recharge are often difficult to perform, and numerical models simulating the water fluxes, have to be applied to enable a quantitative approximation of the groundwater recharge. We made an assumption about the quantity of recharge for the subsurface catchment of the western Dead Sea escarpment, which is at the same time the input for the complex groundwater flow model of the Judea Group Aquifer. This can only be suggested if the hydrogeological situation in the tectonically complex region is fully understood. A number of simplified models of the Judea Group aquifer have been formulated and employed using a two-dimensional (one horizontal layered) numerical simulation of groundwater flow (Baida et al. 1978; Goldschtoff & Shachnai, 1980; Guttman, 2000; Laronne Ben-Itzhak & Gvirtzmann, 2005). However, all previous approaches focused only on a limited area of the Judea Group aquifer. We developed a high resolution regional groundwater flow model for the entire western basin of the Dead Sea. Whereas the structural model could be defined using a large geological dataset, the challenge was to generate the groundwater flow model with only limited well data. With the help of the scientific software OpenGeoSys (OGS) the challenge was reliably solved resulting in a simulation of the hydraulic characteristics (hydraulic conductivity and hydraulic head) of the cretaceous aquifer system, which was calibrated using PEST.

  12. 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.

  13. 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.

  14. 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.

  15. Regression Method for Estimating Long-Term Mean Annual Ground-Water Recharge Rates from Base Flow in Pennsylvania

    USGS Publications Warehouse

    Risser, Dennis W.; Thompson, Ronald E.; Stuckey, Marla H.

    2008-01-01

    A method was developed for making estimates of long-term, mean annual ground-water recharge from streamflow data at 80 streamflow-gaging stations in Pennsylvania. The method relates mean annual base-flow yield derived from the streamflow data (as a proxy for recharge) to the climatic, geologic, hydrologic, and physiographic characteristics of the basins (basin characteristics) by use of a regression equation. Base-flow yield is the base flow of a stream divided by the drainage area of the basin, expressed in inches of water basinwide. Mean annual base-flow yield was computed for the period of available streamflow record at continuous streamflow-gaging stations by use of the computer program PART, which separates base flow from direct runoff on the streamflow hydrograph. Base flow provides a reasonable estimate of recharge for basins where streamflow is mostly unaffected by upstream regulation, diversion, or mining. Twenty-eight basin characteristics were included in the exploratory regression analysis as possible predictors of base-flow yield. Basin characteristics found to be statistically significant predictors of mean annual base-flow yield during 1971-2000 at the 95-percent confidence level were (1) mean annual precipitation, (2) average maximum daily temperature, (3) percentage of sand in the soil, (4) percentage of carbonate bedrock in the basin, and (5) stream channel slope. The equation for predicting recharge was developed using ordinary least-squares regression. The standard error of prediction for the equation on log-transformed data was 9.7 percent, and the coefficient of determination was 0.80. The equation can be used to predict long-term, mean annual recharge rates for ungaged basins, providing that the explanatory basin characteristics can be determined and that the underlying assumption is accepted that base-flow yield derived from PART is a reasonable estimate of ground-water recharge rates. For example, application of the equation for 370 hydrologic units in Pennsylvania predicted a range of ground-water recharge from about 6.0 to 22 inches per year. A map of the predicted recharge illustrates the general magnitude and variability of recharge throughout Pennsylvania.

  16. 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.

  17. Ground-water pumpage and artificial recharge estimates for calendar year 2000 and average annual natural recharge and interbasin flow by hydrographic area, Nevada

    USGS Publications Warehouse

    Lopes, Thomas J.; Evetts, David M.

    2004-01-01

    Nevada's reliance on ground-water resources has increased because of increased development and surface-water resources being fully appropriated. The need to accurately quantify Nevada's water resources and water use is more critical than ever to meet future demands. Estimated ground-water pumpage, artificial and natural recharge, and interbasin flow can be used to help evaluate stresses on aquifer systems. In this report, estimates of ground-water pumpage and artificial recharge during calendar year 2000 were made using data from a variety of sources, such as reported estimates and estimates made using Landsat satellite imagery. Average annual natural recharge and interbasin flow were compiled from published reports. An estimated 1,427,100 acre-feet of ground water was pumped in Nevada during calendar year 2000. This total was calculated by summing six categories of ground-water pumpage, based on water use. Total artificial recharge during 2000 was about 145,970 acre-feet. At least one estimate of natural recharge was available for 209 of the 232 hydrographic areas (HAs). Natural recharge for the 209 HAs ranges from 1,793,420 to 2,583,150 acre-feet. Estimates of interbasin flow were available for 151 HAs. The categories and their percentage of the total ground-water pumpage are irrigation and stock watering (47 percent), mining (26 percent), water systems (14 percent), geothermal production (8 percent), self-supplied domestic (4 percent), and miscellaneous (less than 1 percent). Pumpage in the top 10 HAs accounted for about 49 percent of the total ground-water pumpage. The most ground-water pumpage in an HA was due to mining in Pumpernickel Valley (HA 65), Boulder Flat (HA 61), and Lower Reese River Valley (HA 59). Pumpage by water systems in Las Vegas Valley (HA 212) and Truckee Meadows (HA 87) were the fourth and fifth highest pumpage in 2000, respectively. Irrigation and stock watering pumpage accounted for most ground-water withdrawals in the HAs with the sixth through ninth highest pumpage. Geothermal production accounted for most pumpage in the Carson Desert (HA 101). Reinjection of ground water pumped for geothermal energy production accounted for about 64 percent (93,310 acre-feet) of the total artificial recharge. The only artificial recharge by water systems was in Las Vegas Valley, where 29,790 acre-feet of water from the Colorado River was injected into the aquifer system. Artificial recharge by mining totaled 22,870 acre-feet. Net ground-water flow was estimated only for the 143 HAs with available estimates of both natural recharge and interbasin flow. Of the 143 estimates, 58 have negative net ground-water flow, indicating that ground-water storage could be depleted if pumpage continues at the same rate. The State has designated HAs where permitted ground-water rights approach or exceed the estimated average annual recharge. Ten HAs were identified that are not designated and have a net ground-water flow between -1,000 to -35,000 acre-feet. Due to uncertainties in recharge, the water budgets for these HAs may need refining to determine if ground-water storage is being depleted.

  18. Groundwater hydrology--coastal flow

    USGS Publications Warehouse

    Sanford, Ward E.

    2010-01-01

    How groundwater flow varies when long-term external conditions change is little documented. Geochemical evidence shows that sea-level rise at the end of the last glacial period led to a shift in the flow patterns of coastal groundwater beneath Florida.

  19. Data assimilation and parameter estimation via ensemble Kalman filter coupled with stochastic moment equations of transient groundwater flow

    NASA Astrophysics Data System (ADS)

    Panzeri, M.; Riva, M.; Guadagnini, A.; Neuman, S. P.

    2013-03-01

    The ensemble Kalman filter (EnKF) is a powerful tool for assimilating data in earth system models. The approach allows real time Bayesian updating of system states and parameters as new data become available. This paper focuses on EnKF data assimilation in models of groundwater flow through complex geologic media. It has become common to treat the hydraulic conductivity of such media as correlated random fields conditioned on measured conductivity (medium property) and/or hydraulic head (system state) values. This renders the conductivity nonstationary and the corresponding conditional flow equations stochastic. Solving these equations and coupling them with EnKF generally entails computationally intensive Monte Carlo (MC) simulation. We propose to circumvent the need for MC through a direct solution of approximate nonlocal (integrodifferential) equations that govern the space-time evolution of conditional ensemble means (statistical expectations) and covariances of hydraulic heads and fluxes. We illustrate and explore our approach on synthetic two-dimensional examples in which a well pumps water from a randomly heterogeneous aquifer subject to prescribed head and flux boundary conditions. Embedding the solution in EnKF provides sequential updates of conductivity and head estimates throughout the space-time domain of interest. We demonstrate the computational feasibility and accuracy of our methodology, showing that hydraulic conductivity estimates are more sensitive to early than to later head values and improve with increasing assimilation frequency at early time.

  20. 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.

  1. 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.

  2. Geomorphic aspects of groundwater flow

    Microsoft Academic Search

    Robert G. LaFleur

    1999-01-01

    The many roles that groundwater plays in landscape evolution are becoming more widely appreciated. In this overview, three\\u000a major categories of groundwater processes and resulting landforms are considered: (1) Dissolution creates various karst geometries,\\u000a mainly in carbonate rocks, in response to conditions of recharge, geologic setting, lithology, and groundwater circulation.\\u000a Denudation and cave formation rates can be estimated from kinetic

  3. 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.

  4. Groundwater flow dynamic investigation without drilling boreholes

    NASA Astrophysics Data System (ADS)

    Moustafa, Mahmoud

    2015-02-01

    The flow net map is a basic tool for groundwater flow dynamics investigation. In areas where there are no boreholes or piezometers are not available, constructing flow net map may be difficult. This work proposes a simple methodology to construct flow net map without drilling boreholes. The flow net map constructed using the proposed approach represents an expected flow net map, which can draw conceptual flow model of the site. The major benefit from constructing the expected flow net map is it gives guidance for locating new boreholes for site investigation, carrying out investigation of the groundwater flow directions and estimating recharge/discharge from the site boundary. An illustrative example for the proposed approach was presented to show how the data required to construct the expected flow net map can be collected. The constructed, expected flow net map using the proposed methodology was compared with actual flow net map constructed from measured water levels. Both maps give consistent hydrological information about the site. The suggested approach represents a simple and cheap way to carry out investigation of groundwater flow dynamics in areas where there are no boreholes are available.

  5. Challenges to estimate surface- and groundwater flow in arid regions: the Dead Sea catchment.

    PubMed

    Siebert, Christian; Rödiger, Tino; Mallast, Ulf; Gräbe, Agnes; Guttman, Joseph; Laronne, Jonathan B; Storz-Peretz, Yael; Greenman, Anat; Salameh, Elias; Al-Raggad, Marwan; Vachtman, Dina; Ben Zvi, Arie; Ionescu, Danny; Brenner, Asher; Merz, Ralf; Geyer, Stefan

    2014-07-01

    The overall aim of the this study, which was conducted within the framework of the multilateral IWRM project SUMAR, was to expand the scientific basement to quantify surface- and groundwater fluxes towards the hypersaline Dead Sea. The flux significance for the arid vicinity around the Dead Sea is decisive not only for a sustainable management in terms of water availability for future generations but also for the resilience of the unique ecosystems along its coast. Coping with different challenges interdisciplinary methods like (i) hydrogeochemical fingerprinting, (ii) satellite and airborne-based thermal remote sensing, (iii) direct measurement with gauging station in ephemeral wadis and a first multilateral gauging station at the river Jordan, (iv) hydro-bio-geochemical approach at submarine and shore springs along the Dead Sea and (v) hydro(geo)logical modelling contributed to the overall aim. As primary results, we deduce that the following: (i) Within the drainage basins of the Dead Sea, the total mean annual precipitation amounts to 300 mm a(?1) west and to 179 mm a(?1) east of the lake, respectively. (ii) The total mean annual runoff volumes from side wadis (except the Jordan River) entering the Dead Sea is approximately 58–66 × 10(6) m(3) a(?1) (western wadis: 7–15 × 10(6) m(3) a(?1); eastern wadis: 51 × 10(6) m(3) a(?1)). (iii) The modelled groundwater discharge from the upper Cretaceous aquifers in both flanks of the Dead Sea towards the lake amounts to 177 × 10(6) m(3) a(?1). (iv) An unexpected abundance of life in submarine springs exists, which in turn explains microbial moderated geo-bio-chemical processes in the Dead Sea sediments, affecting the highly variable chemical composition of on- and offshore spring waters.The results of this work show a promising enhancement of describing and modelling the Dead Sea basin as a whole. PMID:24767316

  6. Groundwater flow modeling of two-levels perched karstic leaking aquifers as a tool for estimating recharge and hydraulic parameters

    NASA Astrophysics Data System (ADS)

    Peleg, Nadav; Gvirtzman, Haim

    2010-06-01

    SummaryPerched springs in nature emerge from aquifers laying on aquitards within the unsaturated zone, some of which emerge one above the other. A finite element model was introduced, using the FEFLOW code, for simulating the groundwater flow regime in each of these aquifers, for quantifying the fraction of rain that recharges the aquifers, and for estimating the hydrogeological parameters of the aquifers and aquitards. Many of the perched springs in Israel are found in the Judea Group aquifer, a stratified carbonate rock unit, characterised by a well-developed karst system. The Batir and Jamia springs exemplifies such a system, where Batir is the upper spring discharging at the contact between Aminadav and Moza Formations, and Jamia is the lower one, discharging at the contact between Kesalon and Sorek Formations. The 25-year-long measured spring's hydrographs were used to calibrate the spring's coefficients, the hydraulic conductivities of the different layers, the karst features and the yearly amount of rain recharging the spring.

  7. 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.

  8. ESTIMATING FLOW AND FLUX OF GROUND-WATER DISCHARGE USING WATER TEMPERATURE AND VELOCITY. (R827961)

    EPA Science Inventory

    The nature of ground water discharge to a stream has important implications for nearby ground water flow, especially with respect to contaminant transport and well-head protection. Measurements of ground water discharge were accomplished in this study using (1) differences bet...

  9. Transient modeling of regional groundwater flow using parameter estimates from steady-state automatic calibration

    NASA Astrophysics Data System (ADS)

    Sonnenborg, Torben O.; Christensen, Britt S. B.; Nyegaard, Per; Henriksen, Hans Jørgen; Refsgaard, Jens Christian

    2003-03-01

    Use of automatic calibration of large physically based hydrological models running in a transient mode is severely constrained by the long simulation time. Here, the possibility of using a steady-state model, with fast model execution, as the basis for automatic calibration of the involved parameters is examined. It is tested if the parameters estimated with the steady-state model can be used for the subsequent transient modeling of the same hydrological system. The problem is analysed for the 5900 km 2 South Jutland area, being one of the 11 model areas of the National Water Resource Model of Denmark. The area is modelled using the MIKE SHE code while UCODE is used for optimization. Hydraulic head data and stream discharge data are available for calibration. It is examined how the estimated parameters are affected by the choice of (a) recharge input to the steady-state model, and (b) target data used for calibration. The reliability of the parameters is evaluated and the resulting ability of the optimized models to simulate the transient response of the system is assessed. The results show that the estimated parameters are highly sensitive to the way that the steady-state model is conceptualized. The study suggests how the steady-state model should be conceptualized in order to obtain reliable parameter estimates that produce acceptable transient model results.

  10. Estimates of tracer-based piston-flow ages of groundwater from selected sites-National Water-Quality Assessment Program, 1992-2005

    USGS Publications Warehouse

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

    2011-01-01

    This report documents selected age data interpreted from measured concentrations of environmental tracers in groundwater from 1,399 National Water-Quality Assessment (NAWQA) Program groundwater sites across the United States. The tracers of interest were chlorofluorocarbons (CFCs), sulfur hexafluoride (SF6), and tritium/helium-3 (3H/3He). Tracer data compiled for this analysis primarily were from wells representing two types of NAWQA groundwater studies - Land-Use Studies (shallow wells, usually monitoring wells, in recharge areas under dominant land-use settings) and Major-Aquifer Studies (wells, usually domestic supply wells, in principal aquifers and representing the shallow, used resource). Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) associated with Land-Use Studies also were included. Tracer samples were collected between 1992 and 2005, although two networks sampled from 2006 to 2007 were included because of network-specific needs. Tracer data from other NAWQA Program components (Flow System Studies, which are assessments of processes and trends along groundwater flow paths, and various topical studies) were not compiled herein. Tracer data from NAWQA Land-Use Studies and Major-Aquifer Studies that previously had been interpreted and published are compiled herein (as piston-flow ages), but have not been reinterpreted. Tracer data that previously had not been interpreted and published are evaluated using documented methods and compiled with aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF6), estimates of tracer-based piston-flow ages, and selected ancillary data, such as redox indicators, well construction, and major dissolved gases (N2, O2, Ar, CH4, and CO2). Tracer-based piston-flow ages documented in this report are simplistic representations of the tracer data. Tracer-based piston-flow ages are a convenient means of conceptualizing groundwater age. However, the piston-flow model is based on the potentially limiting assumptions that tracer transport is advective and that no mixing occurs. Additional uncertainties can arise from tracer degradation, sorption, contamination, or fractionation; terrigenic (natural) sources of tracers; spatially variable atmospheric tracer concentrations; and incomplete understanding of mechanisms of recharge or of the conditions under which atmospheric tracers were partitioned to recharge. The effects of some of these uncertainties are considered herein. For example, degradation, contamination, or fractionation often can be identified or inferred. However, detailed analysis of the effects of such uncertainties on the tracer-based piston-flow ages is constrained by sparse data and an absence of complementary lines of evidence, such as detailed solute transport simulations. Thus, the tracer-based piston-flow ages compiled in this report represent only an initial interpretation of the tracer data.

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

    Microsoft Academic Search

    Ronald L. Hershey; Steve Y. Acheampong

    1997-01-01

    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

  12. Modeling groundwater flow on MPPs

    SciTech Connect

    Ashby, S.F.; Falgout, R.D.; Smith, S.G.; Tompson, A.F.B.

    1993-10-01

    The numerical simulation of groundwater flow in three-dimensional heterogeneous porous media is examined. To enable detailed modeling of large contaminated sites, preconditioned iterative methods and massively parallel computing power are combined in a simulator called PARFLOW. After describing this portable and modular code, some numerical results are given, including one that demonstrates the code`s scalability.

  13. An inverse modeling approach to estimate groundwater flow and transport model parameters at a research site at Vandenberg AFB, CA

    NASA Astrophysics Data System (ADS)

    Rasa, E.; Foglia, L.; Mackay, D. M.; Ginn, T. R.; Scow, K. M.

    2009-12-01

    A numerical groundwater fate and transport model was developed for analyses of data from field experiments evaluating the impacts of ethanol on the natural attenuation of benzene, toluene, ethylbenzene, and xylenes (BTEX) and methyl tert-butyl ether (MTBE) at Vandenberg Air Force Base, Site 60. We used the U.S. Geological Survey (USGS) groundwater flow (MODFLOW2000) and transport (MT3DMS) models in conjunction with the USGS universal inverse modeling code (UCODE) to jointly determine flow and transport parameters using bromide tracer data from multiple experiments in the same location. The key flow and transport parameters include hydraulic conductivity of aquifer and aquitard layers, porosity, and transverse and longitudinal dispersivity. Aquifer and aquitard layers were assumed homogenous in this study. Therefore, the calibration parameters were not spatially variable within each layer. A total of 162 monitoring wells in seven transects perpendicular to the mean flow direction were monitored over the course of ten months, resulting in 1,766 bromide concentration data points and 149 head values used as observations for the inverse modeling. The results showed the significance of the concentration observation data in predicting the flow model parameters and indicated the sensitivity of the hydraulic conductivity of different zones in the aquifer including the excavated former contaminant zone. The model has already been used to evaluate alternative designs for further experiments on in situ bioremediation of the tert-butyl alcohol (TBA) plume remaining at the site. We describe the recent applications of the model and future work, including adding reaction submodels to the calibrated flow model.

  14. 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).

  15. Mechanisms driving groundwater flow near salt domes

    Microsoft Academic Search

    David G. Evans; Jeffrey A. Nunn; Jeffrey S. Hanor

    1991-01-01

    Groundwater flow near salt domes is complex because groundwater is subject to a variety of driving forces including the release of geopressured fluids, large lateral density gradients, and regional hydraulic head gradients. The complexity of this environment is born out by recent geochemical and geophysical observations that indicate the occurrence of upward groundwater flow near some salt domes. In order

  16. Groundwater Flow System of Unzen Volcano, Japan

    NASA Astrophysics Data System (ADS)

    Kazahaya, K.; Yasuhara, M.; Inamura, A.; Sumii, T.; Hoshizumi, H.; Kohno, T.; Ohsawa, S.; Yusa, Y.; Kitaoka, K.; Yamaguchi, K.

    2001-12-01

    Unzen volcano (peak 1486 m) is developed on the western part of Beppu-Shimabara Graben (20 km NS wide and 200 km EW long) located at Kyushu island, SW Japan. We have been studied groundwater system of the volcano using geochemical and hydrological technique in order to estimate flux of magmatic volatiles through the groundwater. We have collected over 150 sample waters from springs, rivers, and wells, and they are analyzed for major chemistry and stable isotope ratios. Over 50 pore waters were extracted from 100-1200m-deep drilled cores at the eastern flank of the volcano by a centrifugal separator. The results are summarized as follows: 1) Flow rates of springs and rivers indicate that most of the groundwater recharged at Unzen volcano flew down the slope directed to the east, which is restricted by graben structure. 2) All the groundwaters and spring waters collected inside the graben area are isotopically homogeneous, i. e., -48~-45 permil for hydrogen isotope ratio, indicating that the groundwater is well mixed during flowing. 3) In spite of the isotopic homogeneity, the groundwaters are chemically different from each other. In particular, bicarbonate concentration ranged from 20 to 180 mg/l, and it is inconsistent with the isotopic results. There are some active faults parallel to the graben, and bicarbonate anomalies are found close to the faults. Therefore, the chemical variation is likely to be made due to the addition of deep-seated CO2 ascending through the faults. 4) Linear relation between 1/DIC and carbon isotope ratio of DIC indicates that the DIC in groundwater is explained by simple mixing with two source, magmatic and organic matters. Combining the flow rate data, DIC concentrations and carbon isotope ratios, we estimated the magmatic CO2 flux as 30 t/d through the fault system. 5) Pore waters at 100-300m deep have similar isotopic composition to the present shallow groundwater and river waters, suggesting that those pore waters occupy a part of the shallowest aquifer. On the other hand, pore waters collected from the drilled core at greater than 500m show isotopic discontinuity in the vertical variation, indicating that stagnant aquifers formed at deeper levels.

  17. Modeling groundwater flow and quality

    USGS Publications Warehouse

    Konikow, Leonard F.; Glynn, Pierre D.

    2013-01-01

    In most areas, rocks in the subsurface are saturated with water at relatively shallow depths. The top of the saturated zone—the water table—typically occurs anywhere from just below land surface to hundreds of feet below the land surface. Groundwater generally fills all pore spaces below the water table and is part of a continuous dynamic flow system, in which the fluid is moving at velocities ranging from feet per millennia to feet per day (Fig. 33.1). While the water is in close contact with the surfaces of various minerals in the rock material, geochemical interactions between the water and the rock can affect the chemical quality of the water, including pH, dissolved solids composition, and trace-elements content. Thus, flowing groundwater is a major mechanism for the transport of chemicals from buried rocks to the accessible environment, as well as a major pathway from rocks to human exposure and consumption. Because the mineral composition of rocks is highly variable, as is the solubility of various minerals, the human-health effects of groundwater consumption will be highly variable.

  18. Estimating groundwater recharge using an integrated surface and groundwater modelling approach

    NASA Astrophysics Data System (ADS)

    Chiew, F. H. S.; McMahon, T. A.; O'Neill, I. C.

    1992-02-01

    This paper describes the use of an integrated surface and groundwater modelling approach to estimate regional groundwater recharge rates. The daily version of the Monash Rainfall-Runoff Model, HYDROLOG, was adapted to represent the surface hydrological processes and the finite-element groundwater model, AQUIFEM-N, used to model the groundwater flow. The integrated model was calibrated against streamflow and potentiometric head data, with recharge estimated as an output from the calibrated model. The model was applied to both the irrigated and non-irrigated areas in the northern half of the Campaspe River Basin in north-central Victoria, Australia. The integrated model utilises the important features of the surface and groundwater models. It is useful in evaluating water resource development through better management of the conjunctive use of surface and ground water, and is an important tool in any predictive recharge study.

  19. 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

  20. 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

  1. Mechanisms driving groundwater flow near salt domes

    SciTech Connect

    Evans, D.G.; Nunn, J.A.; Hanor, J.S. (Louisiana State Univ., Baton Rouge (United States))

    1991-05-01

    Groundwater flow near salt domes is complex because groundwater is subject to a variety of driving forces including the release of geopressured fluids, large lateral density gradients, and regional hydraulic head gradients. The complexity of this environment is born out by recent geochemical and geophysical observations that indicate the occurrence of upward groundwater flow near some salt domes. In order to evaluate the relative importance of different mechanisms driving groundwater flow near salt domes, the authors have developed a numerical model that couples groundwater flow, heat transport, and transport of dissolved salt, and accounts for salt diapirism. The calculations indicate that upward groundwater flow can occur as the result of thermal convection when the regional background salinity is greater than 15 weight percent, a value typical of many areas of the south Louisiana salt dome province. For lower background salinities, dissolution causes salt-laden groundwater near the dome to sink, leading to depressed isotherms. While the release of geopressured fluids is difficult to quantify, it remains a likely mechanism for driving upward groundwater flow near some salt domes.

  2. Conceptual groundwater flow models identified in triassic basins, eastern united states

    NASA Astrophysics Data System (ADS)

    Venkatakrishnan, R.; Gheorghiu, F.

    2003-04-01

    Identification of a conceptual groundwater flow model is an important step in planning appropriate groundwater investigations for the accurate delineation of contaminated sites. Development of a conceptual groundwater flow model early in the process of defining groundwater impacts can save resources and minimize the potential for erroneous interpretations resulting in potentially flawed remedial designs. This study presents typical groundwater flow models identified in several Triassic Basins that occur as half-graben along the eastern seaboard of the United States. Groundwater flow in the Triassic sedimentary rocks has local and regional components. Shallow groundwater discharges locally to nearby streams. Deeper, regional groundwater flow is toward points of regional groundwater discharge, generally higher order stream courses. The hydrogeologic regime within the basins is characterized by fractured, bedded sedimentary sequences with groundwater occuring under both unconfined, water table and confined conditions. Inherent controls on groundwater flow are a combination of the interaction of factors that include topography, stratal geometry and lithology, the distribution and intensity of fractures, presence of diabase intrusions, basalt flows, and weathering processes of the bedrock materials. The main groups of conceptual groundwater flow models identified in the Triassic Basins include: (i) structural control flow models (i.e., bedding strike, bedding dip, basalt cooling fractures, major joint sets and faults), (ii) lithologic control flow models (i.e., top of rock weathered zone, basalt flow top weathering, diabase dikes, lopolith containment), and, (iii) topographic control, and (iv) combinations of above. The identification of these distinct groundwater flow conceptual models is possible based on numerous investigations focused on environmental issues conducted in Connecticut, New Jersey, Pennsylvania, Virginia, and North Carolina. The typical conceptual groundwater flow models that are developed as a function of geologic setting can be used as a guide in developing site hydrogeologic models, to plan groundwater investigations and interpret the results, and estimate the potential spread of contaminant impacts to groundwater.

  3. 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.

  4. Groundwater Flow System of Unzen Volcano, Japan

    Microsoft Academic Search

    K. Kazahaya; M. Yasuhara; A. Inamura; T. Sumii; H. Hoshizumi; T. Kohno; S. Ohsawa; Y. Yusa; K. Kitaoka; K. Yamaguchi

    2001-01-01

    Unzen volcano (peak 1486 m) is developed on the western part of Beppu-Shimabara Graben (20 km NS wide and 200 km EW long) located at Kyushu island, SW Japan. We have been studied groundwater system of the volcano using geochemical and hydrological technique in order to estimate flux of magmatic volatiles through the groundwater. We have collected over 150 sample

  5. Patterns in groundwater chemistry resulting from groundwater flow

    Microsoft Academic Search

    Pieter J. Stuyfzand

    1999-01-01

    Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints\\u000a of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated\\u000a by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with\\u000a a specific origin), the following prograde evolution lines

  6. 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).

  7. 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.

  8. 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

  9. GROUNDWATER FLOW IN LOW-PERMEABILITY ENVIRONMENTS.

    USGS Publications Warehouse

    Neuzil, C.E.

    1986-01-01

    Certain geologic media are known to have small permeability; subsurface environments composed of these media and lacking well developed secondary permeability have groundwater flow systems with many distinctive characteristics. Moreover, groundwater flow in these environments appears to influence the evolution of certain hydrologic, geologic, and geochemical systems, may affect the accumulation of petroleum and ores, and probably has a role in the structural evolution of parts of the crust. Such environments are also important in the context of waste disposal. This review attempts to synthesize the diverse contributions of various disciplines to the problem of flow in low-permeability environments. Problems hindering analysis are enumerated together with suggested approaches to overcoming them. A common thread running through the discussion is the significance of size- and time-scale limitations of the ability to directly observe flow behavior and make significance of size- and time-scale limitations of the ability to directly observe flow behavior and make measurements of parameters.

  10. Estimating exposure to groundwater contaminants in karst areas

    NASA Astrophysics Data System (ADS)

    Butscher, C.

    2012-12-01

    Large multidisciplinary projects investigate health effects and environmental impacts of contamination. Such multidisciplinary projects challenge groundwater hydrologist because they demand estimations of human or environmental exposure to groundwater contaminants. But especially in karst regions, groundwater quality is subject to rapid changes resulting from highly dynamic flow systems with rapid groundwater recharge and contaminant transport in karst conduits. There is a strong need for tools that allow the quantification of the risk of contaminant exposure via the karst groundwater and its temporal variation depending on rainfall events and overall hydrological conditions. A fact that makes the assessment of contaminant exposure even more difficult is that many contaminants behave differently in the subsurface than the groundwater, because they do not dissolve and exist as a separate phase. Important examples are particulate contaminants, such as bacteria, and non-aqueous phase liquids (NAPLs), such as many organic compounds. Both are ubiquitous in the environment and have large potential for health impacts. It is known from bacterial contamination of karst springs that such contamination is strongly related to flow conditions. Bacteria, which are present at the land surface, in the soil, rock matrix or the conduit system, are immobile during base flow conditions. During storm events however, they become mobilized and are rapidly transported through the conduit flow system from sources to areas of potential exposure. As a result, bacteria concentrations that most times are low at a spring can show a high peak during storm flow. Conceptual models exist that suggest that the transport of NAPLs in karst aquifers is, just like bacterial contamination, related to flow conditions. Light NAPLs that reach the saturated zone float and accumulate on the water table; and dense NAPLs sink downward in the aquifer until they are trapped in pores, fractures and conduits where they remain stationary under base flow conditions. During storm flows, however, they can be dragged downstream or flushed as suspensions and emulsions. As a result, storm flow can send previously immobilized NAPLs to exposure zones in toxic pulses. An approach is presented to estimate the risk of contaminant exposure by bacteria and NAPLs via the groundwater under variable hydrological conditions (Butscher et al. 2011). The approach uses an indicator that is expressed as the Dynamic Vulnerability Index (DVI). This index is defined as the ratio of conduit to matrix flow contributions to spring discharge, and is calculated based on a numerical model simulating karst groundwater flow. The approach is illustrated at a test site in Switzerland, where calculated DVI was compared to the occurrence of fecal indicators during five storm flow events. Key words: karst hydrogeology; groundwater contamination; fecal indicators; NAPLs; numerical modeling References: Butscher, C. Auckenthaler, A., Scheidler, S., Huggenberger, P. (2011). Validation of a Numerical Indicator of Microbial Contamination for Karst Springs. Ground Water 49 (1), 66-76.

  11. 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.

  12. 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.

  13. 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.

  14. Multiphase groundwater flow near cooling plutons

    USGS Publications Warehouse

    Hayba, D.O.; Ingebritsen, S.E.

    1997-01-01

    We investigate groundwater flow near cooling plutons with a computer program that can model multiphase flow, temperatures up to 1200??C, thermal pressurization, and temperature-dependent rock properties. A series of experiments examines the effects of host-rock permeability, size and depth of pluton emplacement, single versus multiple intrusions, the influence of a caprock, and the impact of topographically driven groundwater flow. We also reproduce and evaluate some of the pioneering numerical experiments on flow around plutons. Host-rock permeability is the principal factor influencing fluid circulation and heat transfer in hydrothermal systems. The hottest and most steam-rich systems develop where permeability is of the order of 10-15 m2. Temperatures and life spans of systems decrease with increasing permeability. Conduction-dominated systems, in which permeabilities are ???10-16m2, persist longer but exhibit relatively modest increases in near-surface temperatures relative to ambient conditions. Pluton size, emplacement depth, and initial thermal conditions have less influence on hydrothermal circulation patterns but affect the extent of boiling and duration of hydrothermal systems. Topographically driven groundwater flow can significantly alter hydrothermal circulation; however, a low-permeability caprock effectively decouples the topographically and density-driven systems and stabilizes the mixing interface between them thereby defining a likely ore-forming environment.

  15. 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.

  16. 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.

  17. 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.

  18. Estimating the distribution of contemporary (<50 year old) groundwater on Earth

    NASA Astrophysics Data System (ADS)

    Befus, K. M.; Gleeson, T. P.; Luijendijk, E.; Jasechko, S.; Cardenas, M. B.

    2014-12-01

    Time-scales of groundwater dynamics can control how groundwater interacts with many Earth system processes, including weathering, the transport of solutes or contaminants, and hydrologic responses to climate change. In this study, we quantified the global volume and distribution of groundwater that has been recharged over the past 50 years, a time-scale relevant to current policy planning and intimately tied to human generations. We modelled groundwater residence time distributions with several thousand two-dimensional flow and age-as-mass transport simulations guided by global datasets of basin geometric and hydraulic properties. The models suggest that less than 15% of the groundwater on Earth to 2 km depth was recharged in the past 50 years. For most watersheds on Earth, this young groundwater is restricted to the upper 100 m of the Earth's crust. Uncertainty in our estimate stems from the simplification of two-dimensional flow and uncertainty in permeability and porosity.

  19. 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.

  20. Numerical simulation of groundwater flow on MPPs

    SciTech Connect

    Ashby, S.; Falgout, R.; Tompson, A. [Lawrence Livermore National Lab., CA (United States); Fogwell, T. [International Technology Corp., Martinez, CA (United States)

    1994-03-01

    Mathematical models are often used to aid in the design and management of engineered remediation procedures. This paper discusses the numerical simulation of groundwater flow in three-dimensional heterogeneous porous media. A portable and scalable code called PARFLOW is being developed for massively parallel computers to enable the detailed modeling of large sites. This code uses a turning bands algorithm to generate a statistically accurate subsurface realization, and preconditioned conjugate gradients to solve the linear system that yields the flow velocity field. Preliminary numerical results for the LLNL site are presented.

  1. Thermohaline convection in flowing groundwater

    NASA Astrophysics Data System (ADS)

    Rubin, Hillel; Roth, Cornel

    Geothermal activity creates destabilising temperature gradients which are significant in some aquifers. Usually, in such aquifers stabilising salinity gradients also exist. The combination of temperature and salinity distribution in the aquifer may induce various types of hydrodynamic instabilities which were identified in a previous article. The present article concerns the effect of anisotropic characteristics of the hydrodynamic dispersion on the growth of instabilities in the aquifer. Three different mechanisms may lead to instability of the flow field: (a) buoyancy forces may induce convection currents; if the difference between the convection velocity of salt, due to the hydraulic gradients, and that of heat is negligible, then this mechanism is generally most effective in planes parallel to the hydraulic velocity of the fluid (velocity due to the hydraulic gradient); (b) the difference between heat and salt effective diffusivities may lead to overstability; this mechanism is most effective in planes perpendicular to the hydraulic velocity; (c) the difference between the convection velocity of salt and that of heat may induce oscillations which are most effective in planes parallel to the hydraulic velocity. The growth of instabilities in an aquifer of unlimited length is different from their growth in an aquifer of limited length. In the latter thermohaline convection develops in planes perpendicular to the hydraulic velocity, whereas in the former it develops in planes forming an angle ? with the hydraulic gradient. The development of convection cells in the flow field is identified by numerical experiments. These experiments identify the convection cell length and the angle formed between the thermohaline convection plane and the hydraulic gradient.

  2. Using Groundwater Age and Other Isotopic Signatures to Delineate Groundwater Flow and Stratification

    Microsoft Academic Search

    Jean E. Moran; G. Bryant Hudson

    2005-01-01

    Isotopic tracers, such as stable isotopes of the water molecule and tritium, have been used in investigations of groundwater flow and transport and recharge water source for several decades. While these data can place hard constraints on groundwater flow rates, the degree of vertical flow between aquifers and across aquitards, and recharge source area(s), they are rarely used, even for

  3. 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.

  4. A conceptual framework of groundwater flow in some crystalline aquifers in Southeastern Ghana

    NASA Astrophysics Data System (ADS)

    Yidana, Sandow Mark; Ganyaglo, Samuel; Banoeng-Yakubo, Bruce; Akabzaa, Thomas

    2011-02-01

    A conceptual groundwater flow model was developed for the crystalline aquifers in southeastern part of the Eastern region, Ghana. The objective was to determine approximate levels of groundwater recharge, estimate aquifer hydraulic parameters, and then test various scenarios of groundwater extraction under the current conditions of recharge. A steady state groundwater flow model has been calibrated against measured water levels of 19 wells in the area. The resulting recharge is estimated to range from 8.97 × 10 -5 m/d to 7.14 × 10 -4 m/d resulting in a basin wide average recharge of about 9.6% of total annual precipitation, which results in a basin wide quantitative recharge of about 2.4 million m 3/d in the area. This compares to recharge estimated from the chloride mass balance of 7.6% of precipitation determined in this study. The general groundwater flow in the area has also been determined to conform to the general northeast-southwest structural grain of the country. The implication is that the general hydrogeology is controlled by post genetic structural entities imposed on the rocks to create ingresses for sufficient groundwater storage and transport. Calibrated aquifer hydraulic conductivities range between 0.99 m/d and over 19.4 m/d. There is a significant contribution of groundwater discharge to stream flow in the study area. Increasing groundwater extraction will have an effect on stream flow. This study finds that the current groundwater extraction levels represent only 0.17% of the annual recharge from precipitation, and that groundwater can sustain future increased groundwater demands from population growth and industrialization.

  5. Use of Chemical and Isotopic Tracers for Estimating Ground-Water Recharge, Flow Paths, and Residence Times in the Middle San Pedro Basin, Southeast Arizona

    NASA Astrophysics Data System (ADS)

    Adkins, C. B.; McIntosh, J.; Eastoe, C.; Dickinson, J.

    2008-12-01

    Ground water is often the primary source of water for rapidly growing populations in the semi-arid southwestern United States. In addition, ground-water discharge to streams sustains wildlife in riparian areas. Improved understanding of the sources of ground water, recharge areas, flow paths, and water quality of basin aquifer systems is needed to assess water availability and develop effective water management policies. This study analyzes variations of major ion (Ca, Na, K, Mg, Sr, Fe, Si, Zn, F, Cl, Br, NO3, SO4) and isotope (18O, 2H, 3H, 34S, 13C, 14C) chemistry of ground water, surface waters and precipitation with in conjunction with hydrogeologic data (e.g. hydraulic head, subsurface structure, and stratigraphy) to infer recharge areas, mixing of water sources, and residence times of ground water within the middle San Pedro watershed in southeastern Arizona. The San Pedro basin is bound by crystalline and carbonate rocks of the Whetstone and Rincon Mountains on the west and by crystalline rocks of the Dragoon Mountains to the east. Differences in mineral assemblages of these mountain blocks impart distinct chemical signatures in ground waters through mineral weathering. Potentially, these differences in water chemistry can serve as chemical tracers for identifying ground-water flow paths and mixing relations. Ground-water chemistry variations suggest compartmentalization of waters into an upper and lower alluvial aquifer system comprised of permeable sands and gravels ranging in depth from ten to over one thousand feet in the basin center; the units are separated by confining units of silt and clay in the basin center. Variations include higher fluoride (up to 8 ppm) near the Dragoon Mountains, higher chloride (up to 54 ppm) near the Whetstone Mountains, and higher sulfate (up to 750 ppm) concentrations in both upper and lower sands and gravels owing to interaction with thick Permian or Neocene evaporites. Chloride is generally lower (less than 8 ppm) in the lower unit of the aquifer due to limited evaporation. The presence of high nitrates (up to 32 ppm) in the upper sands and gravels indicate modern recharge to this unit. ä18O values ranging from -6.8 to -8.9 suggest that recharge to upper unit originates mostly from summer monsoon precipitation especially along certain reaches of the San Pedro River. Oxygen isotope values between -7.2 and -11.8 indicate that recharge to lower units originates from a mixture of summer and winter precipitation and high elevation recharge. Low percent modern carbon values (8.0 to 37.8 PMC) within lower units indicate recharge within the past ~14,000 years. Detectable tritium (1.0-6.8 TU) near bounding mountain blocks and shallow units near the river indicate recharge within the past sixty years. These parameters yield a complex snapshot of groundwater variability and indicate modern recharge is occurring within high elevation areas and along stretches of the river. The lower unit's geochemical signature suggests it may be hydrologically isolated from modern recharge.

  6. 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)

  7. An improved time series approach for estimating groundwater recharge from groundwater level fluctuations

    Microsoft Academic Search

    M. O. Cuthbert

    2010-01-01

    An analytical solution to a linearized Boussinesq equation is extended to develop an expression for groundwater drainage using estimations of aquifer parameters. This is then used to develop an improved water table fluctuation (WTF) technique for estimating groundwater recharge. The resulting method extends the standard WTF technique by making it applicable, as long as aquifer properties for the area are

  8. Estimation of groundwater recharge using a GIS-based distributed water balance model in Dire Dawa, Ethiopia

    Microsoft Academic Search

    Ketema Tilahun; Broder J. Merkel

    2009-01-01

    Sustainable groundwater management requires knowledge of recharge. Recharge is also an important parameter in groundwater\\u000a flow and transport models. Spatial variation in recharge due to distributed land-us.e, soil texture, topography, groundwater\\u000a level, and hydrometeorological conditions should be accounted for in recharge estimation. However, conventional point-estimates\\u000a of recharge are not easily extrapolated or regionalized. In this study, a spatially distributed water

  9. 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.

  10. Use of a ground-water flow model with particle tracking to evaluate ground-water vulnerability, Clark County, Washington

    USGS Publications Warehouse

    Snyder, Daniel T.; Wilkinson, James M.; Orzol, Leonard L.

    1998-01-01

    A ground-water flow model was used in conjunction with a particle-tracking program to demonstrate a method of evaluating ground-water vulnerability. The study area encompassed the part of the Portland Basin located in Clark County, Washington. A new computer program was developed that interfaces the particle-tracking program with a geographic information system (GIS). The GIS was used to display and analyze the particle-tracking results and to evaluate ground-water vulnerability by identifying recharge areas and their characteristics, determining the downgradient impact of land use at recharge areas, and estimating the age of ground water. The report presents a description of the methods used and the results of the evaluation of ground-water vulnerability.

  11. Simulation of salt migrations in density dependent groundwater flow

    E-print Network

    Vuik, Kees

    of the changing climate become more and more visible; the rain falls in higher intensities, the sea level risesSimulation of salt migrations in density dependent groundwater flow E.S. van Baaren Master's Thesis and uses a finite element method for the simulation of groundwater flow in the lateral (2D) direction

  12. Thermally Induced Groundwater Flow Resulting from an Underground Nuclear Test

    SciTech Connect

    Maxwell, R.M.; Tompson, A.F.B.; Rambo, J.T.; Carle, S.F.; Pawloski, G.A.

    2000-12-16

    The authors examine the transient residual thermal signal resulting from an underground nuclear test (buried below the water table) and its potential to affect local groundwater flow and radionuclide migration in a saturated, fractured, volcanic aquifer system. Thermal profiles measured in a drillback hole between 154 days and 6.5 years after the test have been used to calibrate a non-isothermal model of fluid flow. In this process, they have estimated the magnitude and relative changes in permeability, porosity and fracture density between different portions of the disturbed and undisturbed geologic medium surrounding the test location. The relative impacts of buoyancy forces (arising from the thermal residual of the test and the background geothermal gradient) and horizontal pressure gradients on the post-test flow system are better understood. A transient particle/streamline model of contaminant transport is used to visualize streamlines and streaklines of the flow field and to examine the migration of non-reactive radionuclides. Sensitivity analyses are performed to understand the effects of local and sub-regional geologic features, and the effects of fractured zones on the movement of groundwater and thermal energy. Conclusions regarding the overall effect of the thermal regime on the residence times and fluxes of radionuclides out of the system are drawn, and implications for more complicated, reactive contaminant transport are discussed.

  13. 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.

  14. 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.

  15. An artificial neural network based groundwater flow and transport simulator

    SciTech Connect

    Krom, T.D.; Rosbjerg, D.

    1998-07-01

    Artificial neural networks are investigated as a tool for the simulation of contaminant loss and recovery in three-dimensional heterogeneous groundwater flow and contaminant transport modeling. These methods have useful applications in expert system development, knowledge base development and optimization of groundwater pollution remediation. The numerical model runs used to develop the artificial neural networks can be re-used to develop artificial neural networks to address alternative optimization problems or changed formulations of the constraints and or objective function under optimization. Artificial neural networks have been analyzed with the goal of estimating objectives which normally require the use of traditional flow and transport codes: such as contaminant recovery, contaminant loss (unrecovered) and remediation failure. The inputs to the artificial neutral networks are variable pumping withdrawal rates at fairly unconstrained 3-D locations. A forward-feed backwards error propagation artificial neural network architecture is used. The significance of the size of the training set, network architecture, and network weight optimization algorithm with respect to the estimation accuracy and objective are shown to be important. Finally, the quality of the weight optimization is studied via cross-validation techniques. This is demonstrated to be a useful method for judging training performance for strongly under-described systems.

  16. Conceptual groundwater flow models identified in triassic basins, eastern united states

    Microsoft Academic Search

    R. Venkatakrishnan; F. Gheorghiu

    2003-01-01

    Identification of a conceptual groundwater flow model is an important step in planning appropriate groundwater investigations for the accurate delineation of contaminated sites. Development of a conceptual groundwater flow model early in the process of defining groundwater impacts can save resources and minimize the potential for erroneous interpretations resulting in potentially flawed remedial designs. This study presents typical groundwater flow

  17. Development of a numerical groundwater flow model using SRTM elevations

    Microsoft Academic Search

    Kyle C. Fredrick; Matthew W. Becker; L. Shawn Matott; Ashish Daw; Karl Bandilla; Douglas M. Flewelling

    2007-01-01

    Remotely-sensed elevation data are potentially useful for constructing regional scale groundwater models, particularly in\\u000a regions where ground-based data are poor or sparse. Surface-water elevations measured by the Shuttle Radar Topography Mission\\u000a (SRTM) were used to develop a regional-groundwater flow model by assuming that frozen surface waters reflect local hydraulic\\u000a head (or groundwater potential). Drainage lakes (fed primarily by surface water)

  18. 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.

  19. Surface water seepage effects on shallow groundwater and Rio Grande flow in northern New Mexico

    NASA Astrophysics Data System (ADS)

    Fernald, A.; Helmus, A.; Ochoa, C.; Ortiz, M.; Brown, C.

    2006-12-01

    Timing, amount, and quality of upper Rio Grande flow may be importantly affected by irrigation water that seeps from canals and fields, percolates to shallow groundwater, and returns to the river along subsurface flow paths. In northern New Mexico, changing land use patterns point to potential future reductions in river water deliveries through traditional acequia irrigation canals. We assembled a suite of measurement and modeling technologies to determine the fate of irrigation water and its effects on groundwater and river water. Our 20 km-long study area is a 1 to 2 km-wide irrigated agricultural corridor in a late-Pleistocene floodplain overlain with Holocene alluvial deposits. After the onset of the irrigation season in spring, 12-16% of canal flow seeps below the earthen canal, and 25-60% of flood irrigation applications seep below the plant rooting zone. Water balance and 1-D modeling (Root Zone Water Quality Model) techniques show this seepage creates a 1-2 m rise in the shallow groundwater table, and subsurface flow paths orient towards the river. Water quality analysis shows dilution of resident shallow groundwater by irrigation seepage and interactions between river surface water and near-river groundwater. Remote sensing-based estimates of riparian forest evapotranspiration show the total riparian extraction of groundwater is small compared to groundwater return flow that originated as irrigation seepage. Hydrometric analysis indicates spring and early summer peak flows are redistributed through the irrigation seepage to groundwater pathway; the water returns to the river 6 to 10 weeks after diversion into irrigation systems, and generates up to 25% augmentation of late summer and early fall river flow. 2-D (Hydrus) modeling within the floodplain and 3-D (MODFLOW) modeling of the larger valley will integrate characterizations of hydrologic fluxes to simulate irrigation seepage effects on amount and timing of river flow.

  20. Geostatistical inversion of transient moment equations of groundwater flow

    NASA Astrophysics Data System (ADS)

    Riva, M.; Guadagnini, A.; Neuman, S. P.; Bianchi Janetti, E.; Malama, B.

    2009-04-01

    We present a methodology for conditioning estimates of hydraulic heads and fluxes and their associated uncertainty on information about transmissivity, T , and hydraulic heads, h, collected within a randomly heterogeneous aquifer under transient conditions. Our approach is based on recursive finite-element approximations of exact nonlocal first and second conditional moment equations. We present a nonlinear geostatistical inverse algorithm for transient groundwater flow that allows estimating jointly the spatial variability of log-transmissivity, Y = ln T, the underlying variogram and its parameters, and the variance-covariance of the estimates. Log-transmissivity is parameterized geostatistically based on measured values at discrete locations and unknown values at discrete "pilot points." While prior pilot point values are obtained by generalized kriging, posterior estimates at pilot points are obtained by history matching of transient mean flow against values of hydraulic head collected during a pumping test. Parameters are then projected onto a computational grid by kriging. Prior information on hydraulic properties is included in the optimization process via a suitable regularization term which is included in the objective function to be minimized. The weight of the regularization term, hydraulic and unknown variogram parameters are then estimated by maximum likelihood calibration. The main features of the methodology are explored by means of a synthetic example. As alternative flow models we consider (a) a second-order and (b) a lower-order closure of the mean transient flow equation and assess the ability of these models at capturing the parameters of the estimated log-transmissivity variogram. With the aid of formal model selection criteria we associate each mean flow model and different sets of tested variogram parameters with a weight, or posterior probability, representing their relative degrees of likelihood. Our findings suggest that the weight of the regularization term is best identified by adopting a complete second-order approximation of the mean flow model, while predictions of Y (x) and h(x, t) only marginally benefit from a second-order correction. Analysis based on posterior model weights based on the Kashyap measure, KIC, sharply identify the second-order based mean flow model as the most reliable. A unique feature of the method is its capability of providing estimates of prediction errors of hydraulic heads and fluxes, which are calculated a posteriori, upon solving corresponding moment equations. Our example shows that conditioning transient flow predictions on information of both transmissivity and hydraulic heads in general brings about a notable reduction of predictive uncertainty.

  1. Regional Groundwater Flow in the Louisville Aquifer.

    PubMed

    Tiaif, Syafrin; Serrano, Sergio E

    2015-07-01

    The unconfined alluvial aquifer at Louisville, Kentucky, is an important source of water for domestic and industrial uses. It has been the object of several modeling studies in the past, particularly via the application of classical analytical solutions, and numerical solutions (finite differences and finite elements). A new modeling procedure of the Louisville aquifer is presented based on a modification of Adomian's Decomposition Method (ADM) to handle irregularly shaped boundaries. The new approach offers the simplicity, stability, and spatial continuity of analytical solutions, in addition to the ability to handle irregular boundaries typical of numerical solutions. It reduces to the application of a simple set of algebraic equations to various segments of the aquifer. The calculated head contours appear in reasonably agreement with those of previous studies, as well as with those from measured head values from the U.S. Geological Survey field measurement program. A statistical comparison of the error standard deviation is within the same range as that reported in previous studies that used complex numerical solutions. The present methodology could be easily implemented in other aquifers when preliminary results are needed, or when scarce hydrogeologic information is available. Advantages include a simple approach for preliminary groundwater modeling; an analytic description of hydraulic heads, gradients, fluxes, and flow rates; state variables are described continuously over the spatial domain; complications from stability and numerical roundoff are minimized; there is no need for a numerical grid or the handling of large sparse matrices; there is no need to use specialized groundwater software, because all calculations may be done with standard mathematics or spreadsheet programs. Nonlinearity, the effect of higher order terms, and transient simulations could be included if desired. PMID:25070643

  2. Analytical studies on transient groundwater flow induced by land reclamation

    E-print Network

    Jiao, Jiu Jimmy

    Analytical studies on transient groundwater flow induced by land reclamation Litang Hu,1 Jiu Jimmy materials into the sea. Land reclamation may have a significant effect on groundwater regimes, especially when the reclamation is at large scale. Analytical studies on the impact of land reclamation on steady

  3. Comparison of wetland evapotranspiration estimates using diurnal groundwater fluctuations and measurements of a groundwater lysimeter

    NASA Astrophysics Data System (ADS)

    Fahle, Marcus; Dietrich, Ottfried; Lischeid, Gunnar

    2013-04-01

    Sound water management in wetlands requires knowledge of on-going processes and estimates of the water balance components. Specifically evapotranspiration is of crucial importance, as it is often the main water extracting quantity. To avoid elaborate and expensive equipment, which is often required for estimating actual values, potential evapotranspiration is frequently used, which can be easily derived from standard meteorological measurements. However, the potential values may under- or overestimate actual evapotranspiration significantly. A cheap and easy-to-use method for estimating actual values in shallow groundwater environments relies on diurnal groundwater fluctuation. Basically the 24 hours groundwater level decline, considering in some way the prevalent groundwater recovery, is multiplied by the readily available specific yield. Various varieties of this approach have been employed for that purpose, above all differing in their assumptions on groundwater recovery, i.e. lateral or vertical in- or outflow. The objective of our study is therefore to compare these different methods. For this purpose we use data of a weighable groundwater lysimeter situated at a ditch drained grassland site in the Spreewald wetland in Northeastern Germany. The groundwater level in the lysimeter was adjusted to a reference gauge and simulated the conditions of the surrounding area. Hence the lysimeter reflected near natural conditions and provided measurements of all water balance components with high temporal resolution (up to 10 minute intervals). Suitable days, i.e. with a pronounced diurnal fluctuation, of the vegetation periods 2011 and 2012 are chosen and used to prove common assumptions about groundwater recharge, e.g. if the values remain constant during the day or if diurnal variations resulting from gradient changes exist. Finally, based on the lysimeter measurements, the evapotranspiration estimates gained from different approaches that employ diurnal groundwater fluctuation are evaluated.

  4. GROUNDWATER FLOW AND TRANSPORT MODELING Application to Submarine Groundwater Discharge, Coastal Wetland Hydrology, and Deep Well Injection

    E-print Network

    Sukop, Mike

    GROUNDWATER FLOW AND TRANSPORT MODELING Application to Submarine Groundwater Discharge, Coastal, but is also lost to surface water drainage and potential submarine groundwater discharge. There are also to deal with issues such as submarine groundwater discharge and coastal wetland hydrology. SEAWAT also has

  5. The old and the new: the use of classical regional groundwater flow models to address problems of the future (Invited)

    NASA Astrophysics Data System (ADS)

    Cardenas, M.; Befus, K. M.; Gleeson, T. P.; Hesse, M. A.; Jiang, X.; Luijendijk, E.; Toundykov, D.; Zlotnik, V. A.

    2013-12-01

    Achieving the sustainable use of groundwater resources is guided by knowledge of not only how much is volumetrically available but also of its age or turnover time. This information can be achieved using a variety of approaches, e.g., recharge studies, groundwater age dating, and sophisticated physics-based models. Here we highlight some recent insight based on analysis of regional groundwater flow models following the classic Toth scenarios and other related simple cases of basin flows. Analytical and numerical modeling results highlight controls of key but quantifiable parameters such as basin length and depth, water table gradient, surface permeability, and permeability and porosity-depth functions on groundwater age and residence time distribution. Further, we use these results to guide the possible estimation of the availability of ';young' groundwater, i.e., that whose age is less than 50 years. Despite of or rather because of their relative simplicity, the regional flow models allow for rapid assessment of groundwater resources.

  6. 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.

  7. 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.

  8. 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.

  9. The effects of groundwater abstraction on low flows

    NASA Astrophysics Data System (ADS)

    de Graaf, I. E. M.; van Beek, L. P. H.; Wada, Y.; Bierkens, M. F. P.

    2012-04-01

    In regions with frequent water stress and large aquifer systems, groundwater often constitutes an essential source of water. If groundwater abstraction exceeds groundwater recharge over a long time and over large areas persistent groundwater depletion can occur. The resulting lowering of groundwater levels can have negative effects on agricultural productivity but also on natural streamflow and associated wetlands and ecosystems, in particular during low-flow events when the groundwater contribution through baseflow is relatively large. In this study we focus on the effects of global groundwater abstraction on low-flow magnitude, frequency and duration for the major rivers of the world for the period 1960-2000. As a basis, we use the large-scale hydrological model PCR-GLOBWB that calculates all major water balance terms on a daily time step at a 0.5ox0.5o resolution. Currently, PCR-GLOBWB represents groundwater and the associated baseflow by means of a linear reservoir that is parameterized using global lithological data and drainage density. It simulates renewable groundwater storage within each 0.5o cell. Lateral flow between cells is not considered. The specific runoff from the model is subsequently transformed into discharge by means of a kinematic wave routing scheme. In this study we perform a sensitivity analysis in which we evaluate the effects of total water demand for the period 1960-2000 (Wada et al., 2011: doi:10.5194/hess-15-3785-2011). This demand is preferentially met by renewable groundwater storage, secondly by surface water. Any remainder is assumed to stem from non- renewable (i.e. fossil) groundwater resources. Thus, groundwater abstractions act as a direct sink of (renewable) groundwater storage, whereas surface water abstractions act as a direct sink of streamflow. The resulting response is non-trivial as abstractions are variably taken from both groundwater and surface water, where return-flows contribute to a single source: return flow from irrigation demand contributes to groundwater, that from industrial and domenstic demands to surface water. Moreover, groundwater abstractions may lead tot increased capture which we parameterized by including additional recharge through the riverbed when groundwater abstraction is large than the instantaneous baseflow. Model results are compared with observed river discharges of GRDC. The effect of groundwater abstraction on low flows is evaluated by analyzing the difference in simulated discharge between a transient run with increasing abstraction rates over 1960-2000 and a reference run with fixed abstractions rates forced to 1960. Results show that the effects on discharges of both groundwater and surface water abstractions are evident at the global scale, particularly on the magnitude and duration of low flows. Results also show that including return flows is important, particularly in intensively irrigated areas where the magnitude of low-flows generally increased due to water abstractions.

  10. An evaluation of GRACE groundwater estimates over East Africa

    NASA Astrophysics Data System (ADS)

    Nanteza, J.; Thomas, B. F.; de Linage, C.; Famiglietti, J. S.

    2013-12-01

    The East African (EA) region, comprised of five countries (Uganda, Kenya, Tanzania, Rwanda and Burundi), is among those regions characterized as vulnerable to water stress. The region's freshwater resources, both surface and groundwater, are impacted due to increased pressure from changes in climate and human activities. Better management approaches are required to ensure that these pressures do not significantly impact water availability and accessibility. However, the lack of adequate ground-based observation networks to monitor freshwater resources - especially groundwater (the major source of freshwater in EA), limits effective management of the available water resources. In this study, we explore the potential of using remotely sensed data to monitor freshwater resources over EA. The study uses data from the Gravity Recovery and Climate Experiment (GRACE) satellite to estimate groundwater storage variations over EA during the last decade. The satellite's performance in accurately observing changes in groundwater storage is examined by evaluating the GRACE groundwater estimates against spatially interpolated in-situ groundwater observations using goodness of fit criteria including linear regression coefficient, coefficient of determination and root mean square errors. The results demonstrate that GRACE performs well in observing the behavior of groundwater storage. These results can be useful in improving land surface model simulations - a basis for better decision making in water resources management in the region.

  11. Quantitative dye-tracing of karst ground-water flow

    USGS Publications Warehouse

    Smoot, James; Mull, Donald; Liebermann, Timothy

    1989-01-01

    Analysis of the results of repeat quantitative dye traces between a sinkhole and a spring used for public water supply were used to describe predictive relations between discharge, mean travel time, apparent ground-water flow velocity and solute transport characteristics. Normalized peak concentration, mean travel time, and standard deviation of travel times were used to produce a dimensionless, composite type curve that was used to produce a dimensionless, composite type curve that was used to simulate solute transport characteristics for selected discharges. Using this curve and previously developed statistical relations, a water manager can estimate the arrival time, peak concentration, and persistence of a soluble contaminant at a supply spring or well based on discharge and the quantity of spilled contaminant.

  12. Thermal effects of compaction-driven groundwater flow from overthrust belts

    Microsoft Academic Search

    David Deming; Jeffrey A. Nunn; David G. Evans

    1990-01-01

    The thermal consequences of compaction-driven groundwater flow resulting from overthrusting are studied with a two-dimensional numerical model. The model represents a foreland basin 5 km deep and 400 km wide and is used to estimate quantitatively the magnitude, direction, and thermal consequences of fluid expulsion. Model simulations in which the permeability structure is homogeneous lead to maximum Darcy velocities of

  13. Cost-effective network design for groundwater flow monitoring

    NASA Astrophysics Data System (ADS)

    Andricevic, R.

    1990-03-01

    The extensive use of groundwater resources has increased the need for developing cost-effective monitoring networks to provide an indication of the degree to which the subsurface environment has been affected by human activities. This study presents a cost-effective approach to the design of groundwater flow monitoring networks. The groundwater network design is formulated with two problem formats: maximizing the statistical monitoring power for specified budget constraint and minimizing monitoring cost for statistical power requirement. The statistical monitoring power constraint is introduced with an information reliability threshold value. A branch and bound technique is employed to select the optimal solution from a discrete set of possible network alternatives. The method is tested to the design of groundwater flow monitoring problem in the Pomona County, California.

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

    SciTech Connect

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

    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.

  15. 155: Numerical Models of Groundwater Flow and Transport

    E-print Network

    Sorek, Shaul

    155: Numerical Models of Groundwater Flow and Transport EKKEHARD HOLZBECHER1 AND SHAUL SOREK2 1 Humboldt Universit¨at, Inst. of Freshwater Ecology (IGB), Berlin, Germany 2 Ben Gurion University to numerical modeling of flow and transport problems and to software tools that are currently in use

  16. 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.

  17. 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.

  18. Simulation of Groundwater Flow in the Coastal Plain Aquifer System of Virginia

    USGS Publications Warehouse

    Heywood, Charles E.; Pope, Jason P.

    2009-01-01

    The groundwater model documented in this report simulates the transient evolution of water levels in the aquifers and confining units of the Virginia Coastal Plain and adjacent portions of Maryland and North Carolina since 1890. Groundwater withdrawals have lowered water levels in Virginia Coastal Plain aquifers and have resulted in drawdown in the Potomac aquifer exceeding 200 feet in some areas. The discovery of the Chesapeake Bay impact crater and a revised conceptualization of the Potomac aquifer are two major changes to the hydrogeologic framework that have been incorporated into the groundwater model. The spatial scale of the model was selected on the basis of the primary function of the model of assessing the regional water-level responses of the confined aquifers beneath the Coastal Plain. The local horizontal groundwater flow through the surficial aquifer is not intended to be accurately simulated. Representation of recharge, evapotranspiration, and interaction with surface-water features, such as major rivers, lakes, the Chesapeake Bay, and the Atlantic Ocean, enable simulation of shallow flow-system details that influence locations of recharge to and discharge from the deeper confined flow system. The increased density of groundwater associated with the transition from fresh to salty groundwater near the Atlantic Ocean affects regional groundwater flow and was simulated with the Variable Density Flow Process of SEAWAT (a U.S. Geological Survey program for simulation of three-dimensional variable-density groundwater flow and transport). The groundwater density distribution was generated by a separate 108,000-year simulation of Pleistocene freshwater flushing around the Chesapeake Bay impact crater during transient sea-level changes. Specified-flux boundaries simulate increasing groundwater underflow out of the model domain into Maryland and minor underflow from the Piedmont Province into the model domain. Reported withdrawals accounted for approximately 75 percent of the total groundwater withdrawn from Coastal Plain aquifers during the year 2000. Unreported self-supplied withdrawals were simulated in the groundwater model by specifying their probable locations, magnitudes, and aquifer assignments on the basis of a separate study of domestic-well characteristics in Virginia. The groundwater flow model was calibrated to 7,183 historic water-level observations from 497 observation wells with the parameter-estimation codes UCODE-2005 and PEST. Most water-level observations were from the Potomac aquifer system, which permitted a more complex spatial distribution of simulated hydraulic conductivity within the Potomac aquifer than was possible for other aquifers. Zone, function, and pilot-point approaches were used to distribute assigned hydraulic properties within the aquifer system. The good fit (root mean square error = 3.6 feet) of simulated to observed water levels and reasonableness of the estimated parameter values indicate the model is a good representation of the physical groundwater flow system. The magnitudes and temporal and spatial distributions of residuals indicate no appreciable model bias. The model is intended to be useful for predicting changes in regional groundwater levels in the confined aquifer system in response to future pumping. Because the transient release of water stored in low-permeability confining units is simulated, drawdowns resulting from simulated pumping stresses may change substantially through time before reaching steady state. Consequently, transient simulations of water levels at different future times will be more accurate than a steady-state simulation for evaluating probable future aquifer-system responses to proposed pumping.

  19. A Complementary Modeling Framework to Quantify and Reduce Groundwater Flow Model Uncertainty

    NASA Astrophysics Data System (ADS)

    Valocchi, A. J.; Demissie, Y. K.

    2008-12-01

    Although modern inverse techniques are powerful tools for parameter estimation, results of calibrated groundwater models are nevertheless subject to uncertainty since it is not possible to account for all the natural subsurface complexity. We present a complementary modeling framework in which error-correcting data-driven models are used to handle the bias and uncertainties arising mainly from ignored or misrepresented processes in the physically-based groundwater model. We use MODFLOW as the groundwater flow model and PEST for automatic calibration. The uncertainty of the combined MODFLOW and data-driven models is quantified using First Order Second Moment (FOSM) and bootstrap methods. For both methods, we consider the propagation of uncertainty due to the estimation variance of both the MODFLOW and data-driven models parameters. However, since the data-driven model uses the estimated MODFLOW heads as an input, its predictive variance also incorporates the effect of input data uncertainty. The prediction uncertainties are presented as approximate 95 percent confidence and prediction intervals or quantiles of the underlying distribution of prediction errors. The methods are applied to a case study of transient groundwater flow in the Spokane Valley aquifer that has been previously addressed using a calibrated MODFLOW model. The results are compared with those of more common uncertainty estimation techniques, such as Generalized Likelihood Uncertainty Estimation (GLUE) and Bayesian Model Averaging (BMA). We compare the performance and efficiency of the methods, and discuss some of the challenges related to their practical application.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Implementation and influence of heterogeneous riverbed hydraulic conductivity in groundwater flow models

    NASA Astrophysics Data System (ADS)

    Ghysels, Gert; Huysmans, Marijke

    2015-04-01

    Characterization of groundwater-surface water exchange fluxes is important for assessing riparian ecology, determining quantity and quality of pumped groundwater close to rivers, modeling groundwater flow, predicting flood peaks and low flows, and river water quality. The exchange fluxes between river and aquifer are strongly influenced by the hydraulic conductivity of the riverbed which can vary several orders of magnitude and shows a strong spatial variation. Direct measurement of riverbed hydraulic conductivity is cumbersome and therefore often indirect data such as temperature data or calibration of groundwater models are used to constrain riverbed hydraulic conductivity. In these approaches, the riverbed is usually represented as a homogeneous geological structure and the spatial variation of riverbed hydraulic conductivity is thus neglected. However, neglecting this spatial variation can lead to systematic underestimation of net river-aquifer exchange fluxes and may have important implications for the estimation of peak mass flows, for the hydrochemistry of streambed sediments, nutrient cycling and biogeochemical gradients. The MODFLOW software is the most wide-spread package used for groundwater modelling. In MODFLOW rivers are usually modelled using the River-package. However, in this package no distinction can be made between horizontal and vertical riverbed hydraulic conductivity and the riverbed cannot be subdivided into layers with different hydraulic characteristics. Riverbed sediments are strongly layered and thus another approach is advised. Different ways of introducing heterogeneous riverbeds in MODFLOW groundwater flow models are explored and compared. The influence of heterogeneous riverbeds on groundwater-surface water exchange fluxes is analyzed for two case studies: the Aa River in the Nete catchment and a stretch of the Dijle River near the nature reserve 'de Doode Bemde' (Belgium). For both cases fine-scale distributed local groundwater flow models are available. Heterogeneous riverbeds are introduced in these models and riverbed hydraulic conductivity is modeled based on different stochastic simulation techniques. Several scenarios are explored based on variogram parameters of streambed hydraulic conductivity found in literature. Main goal is to quantify the effect of riverbed heterogeneity on river-aquifer exchange fluxes. This study will determine whether neglecting or simplifying this heterogeneity can lead to significant under- or overestimation of exchange fluxes between river and groundwater. As outcome some guidelines on how to incorporate heterogeneous riverbeds in groundwater flow models will result.

  5. An improved time series approach for estimating groundwater recharge from groundwater level fluctuations

    NASA Astrophysics Data System (ADS)

    Cuthbert, M. O.

    2010-09-01

    An analytical solution to a linearized Boussinesq equation is extended to develop an expression for groundwater drainage using estimations of aquifer parameters. This is then used to develop an improved water table fluctuation (WTF) technique for estimating groundwater recharge. The resulting method extends the standard WTF technique by making it applicable, as long as aquifer properties for the area are relatively well known, in areas with smoothly varying water tables and is not reliant on precipitation data. The method is validated against numerical simulations and a case study from a catchment where recharge is "known" a priori using other means. The approach may also be inverted to provide initial estimates of aquifer parameters in areas where recharge can be reliably estimated by other methods.

  6. Headers will be added later Deriving groundwater estimates in Australia

    E-print Network

    Tregoning, Paul

    sources and future directions in estimating groundwater variations using satellite gravity missions twin satellites in tandem orbit at an altitude of ~450 km, separated by ~200 km (Tapley et al., 2004). The raw observations of the mission include GPS observations (to enable the orbit of the satellites

  7. Simulation of Ground-Water Flow and Effects of Ground-Water Irrigation on Base Flow in the Elkhorn and Loup River Basins, Nebraska

    USGS Publications Warehouse

    Peterson, Steven M.; Stanton, Jennifer S.; Saunders, Amanda T.; Bradley, Jesse R.

    2008-01-01

    Irrigated agriculture is vital to the livelihood of communities in the Elkhorn and Loup River Basins in Nebraska, and ground water is used to irrigate most of the cropland. Concerns about the sustainability of ground-water and surface-water resources have prompted State and regional agencies to evaluate the cumulative effects of ground-water irrigation in this area. To facilitate understanding of the effects of ground-water irrigation, a numerical computer model was developed to simulate ground-water flow and assess the effects of ground-water irrigation (including ground-water withdrawals, hereinafter referred to as pumpage, and enhanced recharge) on stream base flow. The study area covers approximately 30,800 square miles, and includes the Elkhorn River Basin upstream from Norfolk, Nebraska, and the Loup River Basin upstream from Columbus, Nebraska. The water-table aquifer consists of Quaternary-age sands and gravels and Tertiary-age silts, sands, and gravels. The simulation was constructed using one layer with 2-mile by 2-mile cell size. Simulations were constructed to represent the ground-water system before 1940 and from 1940 through 2005, and to simulate hypothetical conditions from 2006 through 2045 or 2055. The first simulation represents steady-state conditions of the system before anthropogenic effects, and then simulates the effects of early surface-water development activities and recharge of water leaking from canals during 1895 to 1940. The first simulation ends at 1940 because before that time, very little pumpage for irrigation occurred, but after that time it became increasingly commonplace. The pre-1940 simulation was calibrated against measured water levels and estimated long-term base flow, and the 1940 through 2005 simulation was calibrated against measured water-level changes and estimated long-term base flow. The calibrated 1940 through 2005 simulation was used as the basis for analyzing hypothetical scenarios to evaluate the effects of ground-water irrigation on stream base flow for 1940 through 2005 and for 2006 through 2045. Simulated base flows were compared for scenarios that alternately did or did not include a representation of the effects of ground-water irrigation. The difference between simulated base flows for the two scenarios represents the predicted effects of ground-water irrigation on base flow. Comparison of base flows between simulations with ground-water irrigation and no ground-water irrigation indicated that ground-water irrigation has cumulatively reduced streamflows from 1940 through 2005 by 888,000 acre-feet in the Elkhorn River Basin and by 2,273,000 acre-feet in the Loup River Basin. Generally, predicted cumulative effects of ground-water irrigation on base flow were 5 to 10 times larger from 2006 through 2045 than from 1940 through 2005, and were 7,678,000 acre-feet for the Elkhorn River Basin and 14,784,000 acre-feet for the Loup River Basin. The calibrated simulation also was used to estimate base-flow depletion as a percentage of pumping volumes for a 50-year future time period, because base-flow depletion percentages are used to guide the placement of management boundaries in Nebraska. Mapped results of the base-flow depletion analysis conducted for most of the interior of the study area indicated that pumpage of one additional theoretical well simulated for a future 50-year period generally would result in more than 80 percent depletion when it was located close to the stream, except in areas where depletion was partly offset by reduced ground-water discharge to evapotranspiration in wetland areas. In many areas, depletion for the 50-year future period composed greater than 10 percent of the pumped water volume for theoretical wells placed less than 7 or 8 miles from the stream, though considerable variations existed because of the heterogeneity of the natural system represented in the simulation. For a few streams, predicted future simulated base flows dec

  8. Complex groundwater flow systems as traveling agent models.

    PubMed

    López Corona, Oliver; 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

  9. 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

  10. 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.

  11. Comparison of local- to regional-scale estimates of ground-water recharge in Minnesota, USA

    NASA Astrophysics Data System (ADS)

    Delin, Geoffrey N.; Healy, Richard W.; Lorenz, David L.; Nimmo, John R.

    2007-02-01

    SummaryRegional ground-water recharge estimates for Minnesota were compared to estimates made on the basis of four local- and basin-scale methods. Three local-scale methods (unsaturated-zone water balance, water-table fluctuations (WTF) using three approaches, and age dating of ground water) yielded point estimates of recharge that represent spatial scales from about 1 to about 1000 m 2. A fourth method (RORA, a basin-scale analysis of streamflow records using a recession-curve-displacement technique) yielded recharge estimates at a scale of 10-1000s of km 2. The RORA basin-scale recharge estimates were regionalized to estimate recharge for the entire State of Minnesota on the basis of a regional regression recharge (RRR) model that also incorporated soil and climate data. Recharge rates estimated by the RRR model compared favorably to the local and basin-scale recharge estimates. RRR estimates at study locations were about 41% less on average than the unsaturated-zone water-balance estimates, ranged from 44% greater to 12% less than estimates that were based on the three WTF approaches, were about 4% less than the age dating of ground-water estimates, and were about 5% greater than the RORA estimates. Of the methods used in this study, the WTF method is the simplest and easiest to apply. Recharge estimates made on the basis of the UZWB method were inconsistent with the results from the other methods. Recharge estimates using the RRR model could be a good source of input for regional ground-water flow models; RRR model results currently are being applied for this purpose in USGS studies elsewhere.

  12. EXPERIMENTAL ANALYSIS OF GROUNDWATER FLOW THROUGH A LANDSLIDE SLIP SURFACE USING NATURAL AND ARTIFICIAL WATER

    E-print Network

    Paris-Sud XI, Université de

    of slip surfaces induces a heterogeneity, where mechanical and hydrogeological properties are modified. Groundwater flows are characterized, using hydro-geochemical methods. The surface deformation is recordedEXPERIMENTAL ANALYSIS OF GROUNDWATER FLOW THROUGH A LANDSLIDE SLIP SURFACE USING NATURAL

  13. Geohydrology, simulation of regional groundwater flow, and assessment of watermanagement strategies, Twentynine Palms area, California

    USGS Publications Warehouse

    Li, Zhen; Martin, Peter

    2011-01-01

    The Marine Corps Air Ground Combat Center (MCAGCC) Twentynine Palms, California, overlies the Surprise Spring, Deadman, Mesquite, and Mainside subbasins of the Morongo groundwater basin in the southern Mojave Desert. Historically, the MCAGCC has relied on groundwater pumped from the Surprise Spring subbasin to provide all of its potable water supply. Groundwater pumpage in the Surprise Spring subbasin has caused groundwater levels in the subbasin to decline by as much as 190 feet (ft) from 1953 through 2007. Groundwater from the other subbasins contains relatively high concentrations of fluoride, arsenic, and (or) dissolved solids, making it unsuitable for potable uses without treatment. The potable groundwater supply in Surprise Spring subbasin is diminishing because of pumping-induced overdraft and because of more restrictive Federal drinking-water standards on arsenic concentrations. The U.S. Geological Survey, in cooperation with the MCAGCC, completed this study to better understand groundwater resources in the area and to help establish a long-term strategy for regional water-resource development. The Surprise Spring, Deadman, Mesquite, and Mainside subbasins are filled with sedimentary deposits of Tertiary age, alluvial fan deposits of Quaternary-Tertiary age, and younger alluvial and playa deposits of Quaternary age. Combined, this sedimentary sequence reaches a maximum thickness of more than 16,000 ft in the Deadman and Mesquite subbasins. The sedimentary deposits of Tertiary age yield a small amount of water to wells, and this water commonly contains high concentrations of fluoride, arsenic, and dissolved solids. The alluvial fan deposits form the principal water-bearing unit in the study area and have a combined thickness of 250 to more than 1,000 ft. The younger alluvial and playa deposits are unsaturated throughout most of the study area. Lithologic and downhole geophysical logs were used to divide the Quaternary/ Tertiary alluvial fan deposits into two aquifers (referred to as the upper and the middle aquifers) and the Tertiary sedimentary deposits into a single aquifer (referred to as the lower aquifer). In general, wells perforated in the upper aquifer yield more water than wells perforated in the middle and lower aquifers. The study area is dominated by extensive faulting and moderate to intense folding that has displaced or deformed the pre-Tertiary basement complex as well as the overlying Tertiary and Quaternary deposits. Many of these faults act as barriers to the lateral movement of groundwater flow and form many of the boundaries of the groundwater subbasins. The principal recharge to the study area is groundwater underflow across the western and southern boundaries that originates as runoff in the surrounding mountains. Groundwater discharges naturally from the study area as spring flow, as groundwater underflow to downstream basins, and as water vapor to the atmosphere by transpiration of phreatophytes and direct evaporation from moist soil. The annual volume of water that naturally recharged to or discharged from the groundwater flow system in the study area during predevelopment conditions was estimated to be 1,010 acre-feet per year (acre-ft/yr). About 90 percent of this recharge originated as runoff from the Little San Bernardino and the Pinto Mountains to the south, and the remainder originated as runoff from the San Bernardino Mountains to the west. Evapotranspiration by phreatophytes near Mesquite Lake (dry) was the primary form of predevelopment groundwater discharge. From 1953 through 2007, approximately 139,400 acre-feet (acre-ft) of groundwater was pumped by the MCAGCC from the Surprise Spring subbasin. A regional-scale numerical groundwater flow model was developed using MODFLOW-2000 for the Surprise Spring, Deadman, Mesquite, and Mainside subbasins. The aquifer system was simulated by using three model layers representing the upper, middle, and lower aquifers. Measured groundwater levels

  14. Modeling groundwater flow by lattice Boltzmann method in curvilinear coordinates

    NASA Astrophysics Data System (ADS)

    Budinski, Ljubomir; Fabian, Julius; Stipic, Matija

    2015-07-01

    In order to promote the use of the lattice Boltzmann method (LBM) for the simulation of isotropic groundwater flow in a confined aquifer with arbitrary geometry, Poisson's equation was transformed into a curvilinear coordinate system. With the metric function between the physical and the computational domain established, Poisson's equation written in Cartesian coordinates was transformed in curvilinear coordinates. Following, the appropriate equilibrium function for the D2Q9 square lattice has been defined. The resulting curvilinear formulation of the LBM for groundwater flow is capable of modeling flow in domains of complex geometry with the opportunity of local refining/coarsening of the computational mesh corresponding to the complexity of the flow pattern and the required accuracy. Since the proposed form of the LBM uses the transformed equation of flow implemented in the equilibrium function, finding a solution does not require supplementary procedures along the curvilinear boundaries, nor in the zones requiring mesh density adjustments. Thus, the basic concept of the LBM is completely maintained. The improvement of the proposed LBM over the previously published classical methods is completely verified by three examples with analytical solutions. The results demonstrate the advantages of the proposed curvilinear LBM in modeling groundwater flow in complex flow domains.

  15. 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 of algal blooms and red tides. An attempt was made to first quantify the submarine groundwater discharge

  16. Identification of groundwater flow paths in complex aquifer systems

    NASA Astrophysics Data System (ADS)

    Lamouroux, Christian; Hani, Azzedine

    2006-09-01

    A methodology was developed and applied to the Tindouf (southwestern Algeria) and the Annaba-Bouteldja aquifers (northeastern Algeria) in order to understand better the hydrogeology of the complex aquifers despite the scarcity of the available data. Graphical representation of deuterium versus oxygen-18 and principal components analysis (PCA) are statistical techniques used to combine various disciplinary data in order to identify chemical and isotopic groups, which are in turn used to define groundwater flow paths. The results of this study agree with the generally accepted hydrogeological conceptual model of the aquifers. In addition, we obtained new results using the PCA method: (1) a description of the complex flow system by grouping various qualitative and quantitative parameters; (2) the definition and characterization of the main groundwater flow paths from their sources to the discharge zones. These flow paths are defined by their water categories, which are represented by salinity and origin of groundwater. This approach is useful for analysing aquifers despite the lack of important database and may also be helpful for studying other complex groundwater basins.

  17. 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.

  18. A preliminary assessment of the effects of groundwater flow on closed-loop ground source heat pump systems

    SciTech Connect

    Chiasson, A.D.; Rees, S.J.; Spitler, J.D.

    2000-07-01

    A preliminary study has been made of the effects of groundwater flow on the heat transfer characteristics of vertical closed-loop heat exchangers and the ability of current design and in-situ thermal conductivity measurement techniques to deal with these effects. It is shown that an initial assessment of the significance of groundwater flow can be made by examining the Peclet number of the flow. A finite-element numerical groundwater flow and heat transfer model has been used to simulate the effects of groundwater flow on a single closed-loop heat exchanger in various geologic materials. These simulations show that advection of heat by groundwater flow significantly enhances heat transfer in geologic materials with high hydraulic conductivity, such as sands, gravels, and rocks exhibiting fractures and solution channels. Simulation data were also used to derive effective thermal conductivities with an in-situ thermal conductivity estimation procedure. These data were used to design borehole fields of different depths for a small commercial building. The performance of these borehole field designs was investigated by simulating each borehole field using the pre-calculated building loads over a ten-year period. Results of these simulations, in terms of the minimum and peak loop temperatures, were used to examine the ability of current design methods to produce workable and efficient designs under a range of groundwater flow conditions.

  19. Estimating the Value of Groundwater in Irrigation

    Microsoft Academic Search

    Nicholas Brozovic; Shahnila Islam

    2010-01-01

    In recent years there has been increasing regulation of agricultural water use in order to reduce transboundary and environmental water conflicts. Effective policy analysis needs to have tools to estimate correctly the value of irrigation water. Irrigating land increases crop yields and this higher profitability should be capitalized into the sales price of the land. For irrigation that depends on

  20. Interbasin groundwater flow and groundwater interaction with surface water in a lowland rainforest, Costa Rica: A review

    Microsoft Academic Search

    David P. Genereux; Michael Jordan

    2006-01-01

    This paper reviews work related to interbasin groundwater flow (naturally occurring groundwater flow beneath watershed topographic divides) into lowland rainforest watersheds at La Selva Biological Station in Costa Rica. Chemical mixing calculations (based on dissolved chloride) have shown that up to half the water in some streams and up to 84% of the water in some riparian seeps and wells

  1. Arsenic and Antimony in Groundwater Flow Systems: A Comparative Study

    Microsoft Academic Search

    Stephanie S. Willis; Shama E. Haque; Karen H. Johannesson

    Arsenic (As) and antimony (Sb) concentrations and speciation were determined along flow paths in three groundwater flow systems,\\u000a the Carrizo Sand aquifer in southeastern Texas, the Upper Floridan aquifer in south-central Florida, and the Aquia aquifer\\u000a of coastal Maryland, and subsequently compared and contrasted. Previously reported hydrogeochemical parameters for all three\\u000a aquifer were used to demonstrate how changes in oxidation–reduction

  2. 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

  3. 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.

  4. 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

  5. A methodology for making initial estimates of groundwater recharge from groundwater vulnerability mapping

    Microsoft Academic Search

    B. D. R. Misstear; L. Brown; D. Daly

    2009-01-01

    Recharge to an aquifer can be estimated by first calculating the effective rainfall using a soil moisture budgeting technique,\\u000a and then by applying a recharge coefficient to indicate the proportion of this effective rainfall that contributes to groundwater\\u000a recharge. In the Republic of Ireland, the recharge coefficient is determined mainly by the permeability and thickness of the\\u000a superficial deposits (subsoils)

  6. Groundwater Flow Demonstration Model Activities for Grades 6-12

    NSDL National Science Digital Library

    Kitt Farrell-Poe

    This set of activities is designed to use a demonstration model available through the Uath County Cooperative Extension Services or from Project WET. They demonstrate such concepts as aquifers, groundwater flow, water table, the relationship between groundwater and surface water, recharge, and others. A glossary and standards correlations to the Utah Core Curriculum for Science are included. The physical model can be obtained through the Utah County Cooperative Extension Service, the Utah Water Resources Education Program, or for sale from Project WET (Water Education for Teachers).

  7. 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.

  8. Groundwater availability as constrained by hydrogeology and environmental flows.

    PubMed

    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. PMID:23582026

  9. Global estimates of submarine groundwater discharge using numerical modeling and geomatics

    NASA Astrophysics Data System (ADS)

    Luijendijk, E.; Gleeson, T.; Ferguson, G. A.

    2011-12-01

    Submarine groundwater discharge (SGD), the flow of fresh or saline groundwater to an ocean, may be a significant contributor to the water and chemical budgets of the world oceans. SGD consists of fresh, terrestrial groundwater driven by hydraulic gradients, the focus of this research, and re-circulated seawater driven by tidal pumping, wave set-up, convection and hydraulic gradients. We couple density-dependent analytical and numerical simulations of generic models of coastal topography and geology with geomatic data bases to resolve the rate and driving mechanisms of terrestrially-derived submarine groundwater discharge globally. Two analytical models lead to linear relationships between SGD and the key predictive parameters: hydraulic gradients, hydraulic conductivities, aquifer thickness and recharge. Average global geomatic parameters suggest global SGD ranges from 0.01% to 0.2% of global river run off which much lower than most previous estimates of global SGD. Quantifying submarine groundwater discharge is critical because SGD is a poorly constrained flux that can significantly contribute to eutrophication or water quality decline in coastal areas.

  10. 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.

  11. Groundwater Flow System in Paraná Basin: Similarities with the Deep Groundwater Flow Systems of the Amazon Region

    NASA Astrophysics Data System (ADS)

    Pimentel, E. T.; Hamza, V.

    2013-05-01

    The focus of the present work is in analysis of bottom-hole temperature data for oil wells in the Parana sedimentary basin, with the purpose of determining subsurface flows of groundwater through the deep strata. Analysis of the available data set have allowed identification of non-linear features in the subsurface temperature fields, indicative of the presence of vertical groundwater movements at a large number of sites in this basin. The results obtained have also contributed to improvements in the current understanding of up flow and down flow systems and in outlining the recharge and discharge systems, operating at depths extending up to a few thousand meters. Vertical velocities of subsurface fluid flows, calculated from model fits to observational data, are found to fall in the range of 10-9 to 10-10 m/s. However, unlike the basins in the Amazon region, where only recharge type movements have been identified, the Paraná basin is found to be characterized by the presence of both recharge and discharge zones. The available data set has allowed identification of three zones of up flows and two zones of down flows. The area extents of down flow zones are found to be quite large. The down flow zones are located relatively close to the central parts of the basin. These are also the zones identified as recharge areas of the main aquifers (Furnas, Aquidauana and Guarani) in the interior of the basin. Since the pattern of hydraulic gradient in this basin is directed from the eastern parts towards its west central parts the down flow zones cannot be considered as associated with the up flow zones indicated in the eastern parts of the basin. The large area extent of such downward groundwater movements is indicative of the presence of distributed recharge type flow systems operating in the subsurface layers of the Paraná basin.

  12. 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.

  13. Improving Radium-based Estimates of Submarine Groundwater Discharge

    NASA Astrophysics Data System (ADS)

    Hughes, A. L.; Wilson, A. M.

    2011-12-01

    Groundwater discharge is vital for the exchange of solutes between salt marshes and estuaries, and radium isotopes are frequently used as tracers of groundwater flow paths and discharge in coastal systems. Considerable spatial and temporal variability in porewater radium activity has hindered the accuracy of this tracer. In porewater, radium activity is a complex function of production by parent isotopes in and grain size of the aquifer material, individual decay rates, porewater salinity, temperature, redox- and pH-dependent adsorption and desorption, sediment Fe- and Mn-oxide/hydroxide coatings, and groundwater transport (advection and dispersion). In order to resolve the primary factors controlling porewater radium activity in an intertidal salt marsh, where high salinity and reducing conditions prevail, and sediment oxide coatings vary from winter to summer, a field and modeling study was conducted at a salt marsh island within North Inlet Salt Marsh, Georgetown, South Carolina. This site was previously developed as part of a larger study to understand the links between salt marsh groundwater dynamics and acute marsh dieback. Porewater and surface water samples were collected from November 2009 - February 2011. Shallow sediment samples were collected in winter and summer 2010, and deeper sediments were split from cores collected during site development. Measurements of water temperature, salinity, mV, and pH were taken in the field, and radium isotopes were measured via delayed-coincidence counter or gamma spectrometry. Surface-bound sediment radium activity was determined by desorption experiments. Iron and manganese oxide coatings on surface sediments were isolated through a sequential leaching process, and the leachate analyzed via ICP-AES. Finally, a 3-D groundwater flow model was developed using SUTRA, a U.S.G.S. numerical model, which was modified to account for changes in total stress resulting from tidal loading of the marsh surface and for complex boundary conditions. Model calibration was performed using observed hydraulic data collected during the salt marsh dieback study, and initial model results suggest slow (0.1 cm/day), downward flow through the marsh mud and lateral flow in the confined, sand aquifer at depth with greater flow rates (2 cm/day) near the channel edges. Preliminary porewater radium activities were 0.4, 8.1, 3.0, and 6.6 dpm/L for 223Ra, 224Ra, 226Ra and 228Ra, respectively, with dilution resulting in lower surface water activities by an order of magnitude. Mean bulk radium activities in the surface sediments were 0.9 and 1.0 dpm/g and for the deeper sediments were 1.4 and 1.6 dpm/g for 226Ra and 228Ra, respectively. Paired t-tests between winter and summer surface sediment samples indicated no significant difference in bulk radium activity (P>>0.1). Statistical tests indicate significant seasonal differences in porewater salinity, temperature, and pH (P?0.001), but no significant seasonal differences in porewater radium activity (P>0.05). These preliminary results suggest groundwater transport and generation rates within the aquifer are the primary factors controlling porewater radium activity. Final radium results will be discussed in terms of the groundwater flow model.

  14. 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...

  15. Dispersion of Magmatic Volatiles through the Groundwater Flow System in and around Iwate Volcano, NE Japan

    Microsoft Academic Search

    M. Ohwada; K. Kazahaya; J. Itoh; M. Takahashi; N. Morikawa; H. A. Takahashi; A. Inamura; A. Nakama; H. Handa; M. Yasuhara; H. Tsukamoto

    2006-01-01

    Groundwater flow system in and around volcano plays an important role as a dispersion pathway of magmatic volatiles from volcanic body. We investigated groundwater flow system based on chemical and isotopic compositions of groundwater and thermal water from variety of depth in and around Iwate volcano, NE Japan. Then we discuss spatial distribution and the amounts of dispersion of magmatic

  16. Using Visual MODFLOW to Simulate Groundwater Flow and Transport

    NSDL National Science Digital Library

    Tim Callahan

    Students are trained to use the Visual MODFLOW computer program (Waterloo Hydrogeologic, Inc.) and they learn first-hand how to apply the Dupuit Approximation to groundwater flow and transport problems in unconfined aquifers. The students apply the Dupuit Approximation (Fetter, 2001) to a case study developed from Anderson and Woessner (1992) in which they are given system dimensions, aquifer properties, and well water levels. Learning objectives include (1) prediction of groundwater flow and transport and (2) model calibration (e.g., getting the model output to match well water level data). Students also learn how to solve the equations using a computer spreadsheet program, further expanding their ability to understand and work with the equations.

  17. Groundwater flow and radionuclide decay-chain transport modelling around a proposed uranium tailings pond in India

    NASA Astrophysics Data System (ADS)

    Elango, L.; Brindha, K.; Kalpana, L.; Sunny, Faby; Nair, R. N.; Murugan, R.

    2012-06-01

    Extensive hydrogeological investigations followed by three-dimensional groundwater flow and contaminant transport modelling were carried out around a proposed uranium tailings pond at Seripalli in Andhra Pradesh, India, to estimate its radiological impact. The hydrogeological parameters and measured groundwater level were used to model the groundwater flow and contaminant transport from the uranium tailings pond using a finite-element-based model. The simulated groundwater level compares reasonably with the observed groundwater level. Subsequently, the transport of long-lived radionuclides such as 238U, 234U, 230Th and 226Ra from the proposed tailings pond was modelled. The ingrowths of progenies were also considered in the modelling. It was observed that these radionuclides move very little from the tailings pond, even at the end of 10,000 y, due to their high distribution coefficients and low groundwater velocities. These concentrations were translated into committed effective dose rates at different distances in the vicinity of the uranium tailings pond. The results indicated that the highest effective dose rate to members of the public along the groundwater flow pathway is 2.5 times lower than the drinking water guideline of 0.1 mSv/y, even after a long time period of 10,000 y.

  18. Tidal along-shore groundwater flow in a coastal aquifer

    Microsoft Academic Search

    L. Li; D. A. Barry; F. Stagnitti; J.-Y. Parlange

    1999-01-01

    Cross-shore interactions between the ocean and a coastal aquifer have been studied extensively, whereas the corresponding\\u000a along-shore case has seldom been examined. This paper presents a numerical model that simulates two-dimensional groundwater\\u000a flow averaged over the thickness of a coastal aquifer. The model is used to examine the essential features of tide-induced,\\u000a along-shore effects on an aquifer adjacent to a

  19. 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.

  20. Discriminant analysis for estimation of groundwater age from hydrochemistry and well construction: Application to New Zealand aquifers

    NASA Astrophysics Data System (ADS)

    Daughney, C.; Morgenstern, U.; van der Raaij, R.; Reeves, R.

    2009-12-01

    Determination of groundwater age is valuable for a variety of reasons covering the spectrum from fundamental scientific research to applied resource management. In New Zealand, tracer methods based on tritium, chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6) are effective for dating young groundwater because their input concentrations via recharge over the past several decades are accurately known. In this study, tritium, CFC and SF6 concentrations have been measured at over 100 groundwater monitoring sites included in the New Zealand National Groundwater Monitoring Programme, followed by interpretation of groundwater age distribution using the exponential-piston flow model. Interpreted mean residence times ranged from less than one year to more than 100 years, with the 25th, 50th (median) and 75th percentiles being approximately 10, 40 and 100 years, respectively. Classification functions derived from discriminant analysis and based on nine input variables (well depth, electrical conductivity and the concentrations of the ions Na, K, Ca, Mg, HCO3, Cl and SO4) allowed assignment of 71% of the sites to the correct of four age categories (mean residence time ten years or less, 11 to 40 years, 41 to 100 years, or more than 100 years). The discriminant analysis classification functions were more effective than regression methods for estimating groundwater age from hydrochemistry and well depth, and can thus be used to estimate the groundwater age category for any monitoring site in New Zealand.

  1. Interpretation of groundwater flow patterns through a reconstruction of the tritium precipitation record in the Cochabamba Valley, Bolivia

    NASA Astrophysics Data System (ADS)

    Stimson, Jesse; Rudolph, David; Frape, Shaun; Drimmie, Robert

    1996-05-01

    Regional behaviour of the groundwater flow system in the Cochabamba Valley, Bolivia, is evaluated through the interpretation of tritium ( 3H) distributions in groundwater samples from wells and springs. In order to interpret groundwater 3H concentrations in Cochabamba Valley, where no historical record of 3H concentrations in rainfall exists, a reconstructed 3H precipitation record is developed. The record of 3H concentrations in precipitation is fairly extensive in the Amazon Basin and this record was extrapolated to the neighbouring Cochabamba Valley. Tritium concentrations in rainfall have been observed to increase under natural conditions with increasing latitude and with increasing distance from the ocean. By considering these trends, a linear relationship for increasing 3H concentration in precipitation is developed, based on data from the Amazon Basin, that realistically predicts regional 3H distributions from the northeast Brazilian coast to Cuzco, Peru. This 3H precipitation record is then extrapolated to the Cochabamba Valley and, after correction for radiogenic decay, is used to interpret trends in groundwater 3H concentrations within the valley. The groundwater flow system in one of the principal alluvial fans, which serves as an important groundwater resource for the city, is studied in detail. Tritium concentrations drop from approximately 8-10 tritium units (TU) in the recharge area to concentrations below the detection limit of 0.8 TU further out in the valley. Groundwater velocities of approximately 0.3 to 0.9 m d -1 are estimated from distributions of groundwater 3H concentrations along the alluvial fan with the use of the reconstructed precipitation 3H record. Regional characteristics of the groundwater flow system are discussed with respect to future development and protection of the groundwater resources.

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

    NASA Astrophysics Data System (ADS)

    Hernandez-Garcia, G.

    2013-12-01

    The study area is located in the State of Guanajuato, Northwest of the city of Mexico. Leon Valley has covered with groundwater its demand of water, estimated in 20.6 cubic meters per second. The constant increase of population and economic activities in the region have a constant growth in water needs. Related extraction rate has produced an average decrease of approximately 1.0 m per year over the past two decades. This suggests that the present management of the groundwater should be checked. Management of groundwater in the study area involves the possibility of producing environmental impacts by extraction. This vital resource under stress becomes necessary studying its hydrogeological functioning to achieve scientific management of groundwater in the Valley. This research was based on the analysis and integration of existing information and the field generated by the authors. Outstanding concepts were: i) the geological structure of the area, ii) hydraulic parameters and iii) composition of deuterium-delta and delta-oxygen - 18. This information has been fully analyzed by applying a groundwater flow model (MODFLOW) and a particle tracking model (FLOWPATH): the results were similar to interpretations in terms of travel time and paths derived from isotopic data.

  3. 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.

  4. 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.

  5. 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.

  6. Effects of multiscale anisotropy on basin and hyporheic groundwater flow.

    PubMed

    Zlotnik, Vitaly A; Cardenas, M Bayani; Toundykov, Daniel

    2011-01-01

    Various subsurface flow systems exhibit a combination of small-scale to large-scale anisotropy in hydraulic conductivity (K). The large-scale anisotropy results from systematic trends (e.g., exponential decrease or increase) of K with depth. We present a general two-dimensional solution for calculation of topography-driven groundwater flow considering both small- and large-scale anisotropy in K. This solution can be applied to diverse systems with arbitrary head distribution and geometry of the water table boundary, such as basin or hyporheic flow. In a special case, this solution reduces to the well-known Tóth model of uniform isotropic basin. We introduce an integral measure of flushing intensity that quantifies flushing at different depths. Using this solution, we simulate heads and streamlines and provide analyses of flow structure in the flow domain, relevant to basin analyses or hyporheic flow. It is shown that interactions between small-scale anisotropy and large-scale anisotropy strongly control the flow structure. In the classic Tóth flow model, the flushing intensity curves exhibit quasi-exponential decrease with depth. The new measure is capable of capturing subtle changes in the flow structure. Our study shows that both small- and large-scale anisotropy characteristics have substantial effects that need to be integrated into analysis of topography-driven flow. PMID:21087251

  7. Parameter Estimation for Groundwater Models under Uncertain Irrigation Data.

    PubMed

    Demissie, Yonas; Valocchi, Albert; Cai, Ximing; Brozovic, Nicholas; Senay, Gabriel; Gebremichael, Mekonnen

    2015-07-01

    The success of modeling groundwater is strongly influenced by the accuracy of the model parameters that are used to characterize the subsurface system. However, the presence of uncertainty and possibly bias in groundwater model source/sink terms may lead to biased estimates of model parameters and model predictions when the standard regression-based inverse modeling techniques are used. This study first quantifies the levels of bias in groundwater model parameters and predictions due to the presence of errors in irrigation data. Then, a new inverse modeling technique called input uncertainty weighted least-squares (IUWLS) is presented for unbiased estimation of the parameters when pumping and other source/sink data are uncertain. The approach uses the concept of generalized least-squares method with the weight of the objective function depending on the level of pumping uncertainty and iteratively adjusted during the parameter optimization process. We have conducted both analytical and numerical experiments, using irrigation pumping data from the Republican River Basin in Nebraska, to evaluate the performance of ordinary least-squares (OLS) and IUWLS calibration methods under different levels of uncertainty of irrigation data and calibration conditions. The result from the OLS method shows the presence of statistically significant (p?estimated parameters and model predictions that persist despite calibrating the models to different calibration data and sample sizes. However, by directly accounting for the irrigation pumping uncertainties during the calibration procedures, the proposed IUWLS is able to minimize the bias effectively without adding significant computational burden to the calibration processes. PMID:25040235

  8. Hydrologic conditions in urban Miami-Dade County, Florida, and the effect of groundwater pumpage and increased sea level on canal leakage and regional groundwater flow

    USGS Publications Warehouse

    Hughes, Joseph D.; White, Jeremy T.

    2014-01-01

    The extensive and highly managed surface-water system in southeastern Florida constructed during the 20th Century has allowed for the westward expansion of urban and agricultural activities in Miami-Dade County. In urban areas of the county, the surface-water system is used to (1) control urban flooding, (2) supply recharge to production well fields, and (3) control seawater intrusion. Previous studies in Miami-Dade County have determined that on a local scale, leakage from canals adjacent to well fields can supply a large percentage (46 to 78 percent) of the total groundwater pumpage from production well fields. Canals in the urban areas also receive seepage from the Biscayne aquifer that is derived from a combination of local rainfall and groundwater flow from Water Conservation Area 3 and Everglades National Park, which are west of urban areas of Miami-Dade County. To evaluate the effects of groundwater pumpage on canal leakage and regional groundwater flow, the U.S. Geological Survey (USGS) developed and calibrated a coupled surface-water/groundwater model of the urban areas of Miami-Dade County, Florida. The model was calibrated by using observation data collected from January 1997 through December 2004. The model calibration was verified using observation data collected from January 2005 through December 2010. A 1-year warmup period (January 1996 through December 1996) was added prior to the start of the calibration period to reduce the effects of inaccurate initial conditions on model calibration. The model is designed to simulate surface-water stage and discharge in the managed canal system and dynamic canal leakage to the Biscayne aquifer as well as seepage to the canal from the aquifer. The model was developed using USGS MODFLOW–NWT with the Surface-Water Routing (SWR1) Process to simulate surface-water stage, surface-water discharge, and surface-water/groundwater interaction and the Seawater Intrusion (SWI2) Package to simulate seawater intrusion, respectively. Automated parameter estimation software (PEST) and highly parameterized inversion techniques were used to calibrate the model to observed surface-water stage, surface-water discharge, net surface-water subbasin discharge, and groundwater level data from 1997 through 2004 by modifying hydraulic conductivity, specific storage coefficients, specific yield, evapotranspiration parameters, canal roughness coefficients (Manning’s n values), and canal leakance coefficients. Tikhonov regularization was used to produce parameter distributions that provide an acceptable fit between model outputs and observation data, while simultaneously minimizing deviations from preferred values based on field measurements and expert knowledge. Analytical and simulated water budgets for the period from 1996 through 2010 indicate that most of the water discharging through the salinity control structures is derived from within the urban parts of the study area and that, on average, the canals are draining the Biscayne aquifer. Simulated groundwater discharge from the urban areas to the coast is approximately 7 percent of the total surface-water inflow to Biscayne Bay and is consistent with previous estimates of fresh groundwater discharge to Biscayne Bay. Simulated groundwater budgets indicate that groundwater pumpage in some surface-water basins ranges from 13 to 27 percent of the sum of local sources of groundwater inflow. The largest percentage of groundwater pumpage to local sources of groundwater inflow occurs in the basins that have the highest pumping rates (C–2 and C–100 Basins). The ratio of groundwater pumpage to simulated local sources of groundwater inflow is less than values calculated in previous local-scale studies. The position of the freshwater-seawater interface at the base of the Biscayne aquifer did not change notably during the simulation period (1996–2010), consistent with the similar positions of the interface in 1984, 1995, and 2011 under similar hydrologic and groundwater pumping conditions. Landward movement of the freshwater-seawater interface

  9. Statistical analysis of hydrographs and water-table fluctuation to estimate groundwater recharge

    Microsoft Academic Search

    Sang-Ki Moon; Nam C Woo; Kwang S Lee

    2004-01-01

    Using water-table monitoring data from the National Groundwater Monitoring Network in Korea, groundwater hydrographs were classified into five typical groups. Then, to estimate groundwater recharge, a modified water-table fluctuation (WTF) method was developed from the relation between the cumulative WTF and corresponding precipitation records. Applying this method to different types of hydrographs, the spatial variability of recharge in river basins

  10. A method of estimating spatio-temporally distributed groundwater recharge using integrated surface-subsurface modelling

    Microsoft Academic Search

    Il Moon Chung; Nam Won Kim; Jeongwoo Lee; Marios Sophocleous

    2010-01-01

    In general, there have been various methods of estimating groundwater recharge such as baseflow separation approaches, water budget analyses based on lumped conceptual models, and the water table fluctuation method (WTF) by using data from groundwater monitoring wells. However, groundwater recharge rates show spatial-temporal variability due to climatic conditions, land use, and hydrogeological heterogeneity, so these methods have various limitations

  11. MODIS-Aided Statewide Net Groundwater-Recharge Estimation in Nebraska

    E-print Network

    Szilagyi, Jozsef

    -function-transformed groundwater vulnerability DRASTIC-code values. Statewide mean annual net recharge became about 29 mm (i.e., 5MODIS-Aided Statewide Net Groundwater-Recharge Estimation in Nebraska by Jozsef Szilagyi1 by declining groundwater levels due to large-scale irrigation are found in the south-western region

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

    SciTech Connect

    Arnold, B.W.; Altman, S.J. [Sandia National Labs., Albuquerque, NM (United States); Robey, T.H. [Spectra Research Institute, Albuquerque, NM (United States)] [and others

    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.

  13. 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.

  14. Hydrogeology, simulated ground-water flow, and ground-water quality, Wright-Patterson Air Force Base, Ohio

    USGS Publications Warehouse

    Dumouchelle, D.H.; Schalk, C.W.; Rowe, G.L.; De Roche, J.T.

    1993-01-01

    Ground water is the primary source of water in the Wright-Patterson Air Force Base area. The aquifer consists of glacial sands and gravels that fill a buried bedrock-valley system. Consolidated rocks in the area consist of poorly permeable Ordovician shale of the Richmondian stage, in the upland areas, the Brassfield Limestone of Silurian age. The valleys are filled with glacial sediments of Wisconsinan age consisting of clay-rich tills and coarse-grained outwash deposits. Estimates of hydraulic conductivity of the shales based on results of displacement/recovery tests range from 0.0016 to 12 feet per day; estimates for the glacial sediments range from less than 1 foot per day to more than 1,000 feet per day. Ground water flow from the uplands towards the valleys and the major rivers in the region, the Great Miami and the Mad Rivers. Hydraulic-head data indicate that ground water flows between the bedrock and unconsolidated deposits. Data from a gain/loss study of the Mad River System and hydrographs from nearby wells reveal that the reach of the river next to Wright-Patterson Air Force Base is a ground-water discharge area. A steady-state, three-dimensional ground-water-flow model was developed to simulate ground-water flow in the region. The model contains three layers and encompasses about 100 square miles centered on Wright-Patterson Air Force Base. Ground water enters the modeled area primarily by river leakage and underflow at the model boundary. Ground water exits the modeled area primarily by flow through the valleys at the model boundaries and through production wells. A model sensitivity analysis involving systematic changes in values of hydrologic parameters in the model indicates that the model is most sensitive to decreases in riverbed conductance and vertical conductance between the upper two layers. The analysis also indicates that the contribution of water to the buried-valley aquifer from the bedrock that forms the valley walls is about 2 to 4 percent of the total ground-water flow in the study area. Ground waters in the vicinity of Wright-Patterson Air Force Base can be classified into two compositional groups on the basis of their chemical composition: calcium magnesium bicarbonate-type and sodium chloride-type waters. Calcium magnesium bicarbonate-type waters are found in the glacial deposits and the Brassfield Limestone, whereas the sodium chloride waters are exclusively associated with the shales. Equilibrium speciation calculations indicate that ground water of the glacial drift aquifer is in equilibrium with calcite, dolomite, and chalcedony, but is undersaturated with respect to gypsum and fluorite. Waters from the shales are slightly supersaturated with respect to calcite, dolomite, and siderite but are undersaturated with respect to chalcedony. Simple-mass balance calculations treating boron as a conservative species indicate that little (< 5 percent) or no recharge from the shales to the glacial drift aquifer takes place. Data on the stable isotopes of oxygen and hydrogen indicate a meteoric origin for all ground water beneath Wright-Patterson Air Force Base, but the data were inconclusive with respect to identification of distinct isotopic differences between water collected from the glacial drift and bedrock aquifers. Tritium concentrations used to distinguish waters having a pre-and post-1953 recharge component indicate that most water entered the glacial drift aquifer after 1953. This finding indicates that recharge from shallow to deep parts (greater than 150 feet) of the aquifer takes place over time intervals of a few years or decades. However, the fact that some deep parts of the glacial aquifer did not contain measurable tritium indicates that ground-water flow from recharge zones to these parts of the aquifer takes decades or longer.

  15. 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.

  16. 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.

  17. 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.

  18. 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)

  19. The effect of sediment thermal conductivity on vertical groundwater flux estimates

    NASA Astrophysics Data System (ADS)

    Sebok, Eva; Müller, Sascha; Engesgaard, Peter; Duque, Carlos

    2015-04-01

    The interaction between groundwater and surface water is of great importance both from ecological and water management perspective. The exchange fluxes are often estimated based on vertical temperature profiles taken from shallow sediments assuming a homogeneous standard value of sediment thermal conductivity. Here we report on a field investigation in a stream and in a fjord, where vertical profiles of sediment thermal conductivity and temperatures were measured in order to, (i) define the vertical variability in sediment thermal conductivity, (ii) quantify the effect of heterogeneity in sediment thermal conductivity on the estimated vertical groundwater fluxes. The study was carried out at field sites located in Ringkøbing fjord and Holtum stream in Western Denmark. Both locations have soft, sandy sediments with an upper organic layer at the fjord site. First 9 and 12 vertical sediment temperature profiles up to 0.5 m depth below the sediment bed were collected in the fjord and in the stream, respectively. Later sediment cores of 0.05 m diameter were removed at the location of the temperature profiles. Sediment thermal conductivity was measured in the sediment cores at 0.1 m intervals with a Decagon KD2 Pro device. A 1D flow and heat transport model (HydroGeoSphere) was set up and vertical groundwater fluxes were estimated based on the measured vertical sediment temperature profiles by coupling the model with PEST. To determine the effect of heterogeneity in sediment thermal conductivity on estimated vertical groundwater fluxes, the model was run by assigning (i) a homogeneous thermal conductivity for all sediment layers, calculated as the average sediment thermal conductivity of the profile, (ii) measured sediment thermal conductivities to the different model layers. The field survey showed that sediment thermal conductivity over a 0.5 m profile below the sediment bed is not uniform, having the largest variability in the fjord where organic sediments were also present. Using the measured sediment thermal conductivity for the different model layers instead of a homogeneous distribution did not result in a better fit between observed and simulated sediment temperature profiles. The estimated groundwater fluxes however were greatly affected by using the measured thermal conductivities resulting in changes of ± 45% in estimated vertical fluxes.

  20. Groundwater Budget Analysis of Cross Formational Flow: Hueco Bolson (Texas and Chihuahua)

    NASA Astrophysics Data System (ADS)

    Hutchison, W. R.

    2005-12-01

    Groundwater from the Hueco Bolson supplies the majority of municipal water in El Paso, Texas and Ciudad Juarez, Chihuahua, the largest international border community in the world. For over 100 years, water managers and researchers have been developing an understanding of Hueco Bolson groundwater occurrence and movement, and the interaction between surface water and groundwater. Since 2001, isotopic studies of groundwater chemistry on both sides of the border have provided valuable insights into the occurrence of groundwater and its historic movement. Numerical groundwater flow models of the area have been developed and used since the 1970s. The results of the most recent model were used to develop a detailed analysis of the groundwater inflows, outflows and storage change of the entire area and subregions of the model domain from 1903 to 2002. These detailed groundwater budgets were used to quantify temporal and spatial flow changes that resulted from groundwater pumping: induced inflow of surface water, decreased natural outflows, and storage declines. In addition, the detailed groundwater budgets were used to quantify the changes in cross formational flow between the Rio Grande Alluvium and the Hueco Bolson, as well as the changes in vertical flow within the Hueco Bolson. The groundwater budget results are consistent with the results of the isotopic analyses, providing a much needed confirmation of the overall conceptual model of the numerical model. In addition, the groundwater budgets have provided information that has been useful in further interpreting the results of the isotopic analyses.

  1. Characterizing groundwater flow in a faulted karst system using optical brighteners from septic systems as tracers

    Microsoft Academic Search

    K. E. Murray; D. R. Straud; W. W. Hammond

    2007-01-01

    This study used optical brighteners (OB) released from septic systems to show that groundwater flow direction is largely controlled\\u000a by the structural framework in a faulted karst groundwater system. Effective protection of groundwater resources requires\\u000a that groundwater systems are adequately characterized and source water protection areas (SWPA) are developed for drinking\\u000a water wells. Karst aquifers are among the most sensitive

  2. 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

  3. Estimated ground-water availability in the Delaware River basin, 1997-2000

    USGS Publications Warehouse

    Sloto, Ronald A.; Buxton, Debra E.

    2006-01-01

    Ground-water availability using a watershed-based approach was estimated for the 147 watersheds that make up the Delaware River Basin. This study, conducted by the U.S. Geological Survey in cooperation with the Delaware River Basin Commission (DRBC), supports the DRBC's Water Resources Plan for the Delaware River Basin. Different procedures were used to estimate ground-water availability for the region underlain by fractured rocks in the upper part of the basin and for surficial aquifers in the region underlain by unconsolidated sediments in the lower part of the basin. The methodology is similar to that used for the Delaware River Basin Commission's Ground-Water Protected Area in Pennsylvania. For all watersheds, ground-water availability was equated to average annual base flow. Ground-water availability for the 109 watersheds underlain by fractured rocks in Delaware, New Jersey, New York, and Pennsylvania was based on lithology and physiographic province. Lithology was generalized by grouping 183 geologic units into 14 categories on the basis of rock type and physiographic province. Twenty-three index streamflow-gaging stations were selected to represent the 14 categories. A base-flow-recurrence analysis was used to determine the average annual 2-, 5-, 10-, 25-, and 50-year-recurrence intervals for each index station. A GIS analysis used lithology and base flow at the index stations to determine the average annual base flow for the 109 watersheds. Average annual base flow for these watersheds ranged from 0.313 to 0.915 million gallons per day per square mile for the 2-year-recurrence interval to 0.150 to 0.505 million gallons per day per square mile for the 50-year-recurrence interval. Ground-water availability for watersheds underlain by unconsolidated surficial aquifers was based on predominant surficial geology and land use, which were determined from statistical tests to be the most significant controlling factors of base flow. Twenty-one index streamflow-gaging stations were selected to represent the 13 categories of predominant surficial geology and land use for the 38 Coastal Plain watersheds. A base-flow-recurrence analysis was used to determine the average annual 2-, 5-, 10-, 25-, and 50-year-recurrence intervals for each group of predominant surficial geology and land use. Average annual base flow for these watersheds ranged from 0.465 to 1.169 million gallons per day per square mile for the 2-year-recurrence interval to 0.178 to 0.670 million gallons per day per square mile for the 50-year-recurrence interval. Estimated 2-, 5-, 10-, 25-, and 50-year annual base-flow-recurrence interval values for each watershed in the Delaware River Basin are considered to be the quantity of ground water available for each watershed over a range of climatic conditions. The recurrence intervals are considered to be relative indicators of climatic difference; the 2-year-recurrence value represents wetter years, and the 50-year-recurrence value represents drier years. The remaining available ground water in each watershed was determined by subtracting current (1997-2000) ground-water withdrawals and consumptive domestic use and adding water recharged by agricultural irrigation and land application of treated-sewage effluent. Ground-water use ranged from 0 to 60.8 percent of available ground water for the 2-year-recurrence interval; it exceeded 25 percent in four watersheds and 50 percent in two watersheds. Ground-water use ranged from 0 to 75.9 percent of available ground water for the 5-year-recurrence interval; it exceeded 25 percent in five watersheds and 50 percent in three watersheds. Ground-water use ranged from 0 to 84.5 percent of available ground water for the 10-year-recurrence interval; it exceeded 25 percent in seven watersheds and 50 percent in four watersheds. Ground-water use ranged from 0 to 103 percent of available ground water for the 25-year-recurrence interval; it exceeded 25 percent in nine watersheds, 5

  4. Diffusive fractionation of 3H and 3He in groundwater and its impact on groundwater age estimates

    Microsoft Academic Search

    Eric M. LaBolle; Graham E. Fogg; Juana B. Eweis

    2006-01-01

    The use of 3H and 3He to estimate the apparent age of groundwater presumes that differences in their transport behavior have little effect on 3H-3H ages. Here we show that 3H and 3He are highly susceptible to diffusive fractionation, which can result in substantial errors in 3H-3He apparent ages of post-1950, prebomb peak groundwater. Previous analyses in homogeneous and weakly

  5. Use of remote sensing, GIS and groundwater monitoring to estimate artificial groundwater recharge in Riyadh, Saudi Arabia

    Microsoft Academic Search

    Ayman M. Alrehaili; M. Tahir Hussein

    This study aims to estimate artificial recharge of groundwater by using remote sensing technology, geographical information\\u000a systems, and groundwater surveys. This study is part of the King Fahd project for rainfall and runoff water harvesting, within\\u000a the premises of Alilb Dam in Diriyah to the west of Riyadh. Digital elevation models were obtained with the help of aerial\\u000a photography from

  6. 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)

  7. Spatial variability analysis of combining the water quality and groundwater flow model to plan groundwater and surface water management in the Pingtung plain

    NASA Astrophysics Data System (ADS)

    Chen, Ching-Fang; Chen, Jui-Sheng; Jang, Cheng-Shin

    2014-05-01

    As a result of rapid economic growth in the Pingtung Plain, the use of groundwater resources has changed dramatically. The groundwater is quite rich in the Pingtung plain and the most important water sources. During the several decades, a substantial amount of groundwater has been pumped for the drinking, irrigation and aquaculture water supplies. However, because the sustainable use concept of groundwater resources is lack, excessive pumping of groundwater causes the occurrence of serious land subsidence and sea water intrusion. Thus, the management and conservation of groundwater resources in the Pingtung plain are considerably critical. This study aims to assess the conjunct use effect of groundwater and surface water in the Pingtung plain on recharge by reducing the amount of groundwater extraction. The groundwater quality variability and groundwater flow models are combined to spatially analyze potential zones of groundwater used for multi-purpose in the Pingtung Plain. First, multivariate indicator kriging (MVIK) is used to analyze spatial variability of groundwater quality based on drinking, aquaculture and irrigation water quality standards, and probabilistically delineate suitable zones in the study area. Then, the groundwater flow model, Processing MODFLOW (PMWIN), is adopted to simulate groundwater flow. The groundwater flow model must be conducted by the calibration and verification processes, and the regional groundwater recovery is discussed when specified water rights are replaced by surface water in the Pingtung plain. Finally, the most suitable zones of reducing groundwater use are determined for multi-purpose according to combining groundwater quality and quantity. The study results can establish a sound and low-impact management plan of groundwater resources utilization for the multi-purpose groundwater use, and prevent decreasing ground water tables, and the occurrence of land subsidence and sea water intrusion in the Pingtung plain.

  8. Flow and geochemistry along shallow ground-water flowpaths in an agricultural area in southeastern Wisconsin

    USGS Publications Warehouse

    Saad, D.A.; Thorstenson, D.C.

    1998-01-01

    Water-quality and geohydrologic data were collected from 19 monitor wells and a stream in an agricultural area in southeastern Wisconsin. These sites were located along a 2,700-ft transect from a local ground-water high to the stream. The transect is approximately parallel to the horizontal direction of ground-water flow at the water table. Most of the wells were installed in unconsolidated deposits at five locations along the transect and include an upgradient well nest, a midgradient well nest, a downgradient well nest, wells in the lowland area near the stream, and wells installed in the stream bottom. The data collected from this study site were used to describe the water quality and geohydrology of the area and to explain and model the variations in water chemistry along selected ground-water flowpaths. Water samples from most wells and the stream were analyzed for major ions, nutrients, pesticides, dissolved organic carbon, aluminum, tritium, CFCs, 15N, 18O, and dissolved gases. Measurements of temperature, pH, specific conductance, and dissolved oxygen were made in the field. Concentrations of all dissolved constituents were below Wisconsin ground-water quality enforcement standards. The concentrations of both nitrate and ammonium in precipitation concentrated by evapotranspiration are roughly equal to the concentrations of either in the shallow ground waters. The nitrogen and oxygen isotope data, however, indicate that soil ammonium, ammonium fertilizer, and animal waste are possible nitrate sources. Concentrated precipitation can also supply dissolved sulfate to the shallow ground waters and may be a principal source of pesticides to the ground water. However, some input of dissolved chloride to the ground water from mineral or anthropogenic sources is necessary. X-ray diffraction analyses of samples from 2 cores show the most abundant mineral to be dolomite, with subordinate quartz, microcline, and plagioclase, and minor amounts of mica, hornblende, and chlorite. Hydraulic conductivities determined from slug tests at selected wells range from 0.006 to 55 feet per day, with most values between 0.4 and 12 feet per day. A cross-sectional ground-water flow model, representing the water-table flow system, was developed for the site and was used to identify possible ground-water flowpaths for geochemical modeling. The model was calibrated against measured water levels and was most sensitive to variation in recharge and hydraulic conductivity. The calibrated model shows that downward flow from shallow to deeper wells within a nest may occur at the upgradient and midgradient well nests, but that flow from each well nest travels beneath downgradient nests to the stream. Pathline and travel-time analysis performed on the calibrated flow-model output yielded travel times that range from 5.8 to 59 years with a recharge of 4 inches per yr. Recharge dates based on tritium and CFC concentrations range from pre-1955 to 1986 and are consistent with flowpaths and travel times in the calibrated flow model. Changes in water quality along ground-water flowpaths were evaluated using the geochemical model PHREEQC. Geochemical mole balance models of shallow ground-water formation show that the principal reaction, by an order of magnitude, is dissolution of dolomite with CO2. Concentration factors in the mole-balance models range from 1 to 11, with most values between 5 and 10, which provides independent support for the concentration factor of 8 based on recharge estimates used in the flow model. Ground water recharging at mid- and downgradient wells is oxic and contains dissolved nitrate, whereas the ground water discharging to the stream is anoxic and contains dissolved ammonium. Redox environments were defined at each well on the basis of relative concentrations of various dissolved redox-active species. Chemically permissible flowpaths inferred from the observed sequence of redox environments at well sites are consisten

  9. Estimation of groundwater recharge using a GIS-based distributed water balance model in Dire Dawa, Ethiopia

    NASA Astrophysics Data System (ADS)

    Tilahun, Ketema; Merkel, Broder J.

    2009-09-01

    Sustainable groundwater management requires knowledge of recharge. Recharge is also an important parameter in groundwater flow and transport models. Spatial variation in recharge due to distributed land-us.e, soil texture, topography, groundwater level, and hydrometeorological conditions should be accounted for in recharge estimation. However, conventional point-estimates of recharge are not easily extrapolated or regionalized. In this study, a spatially distributed water balance model WetSpass was used to simulate long-term average recharge using land-use, soil texture, topography, and hydrometeorological parameters in Dire Dawa, a semiarid region of Ethiopia. WetSpass is a physically based methodology for estimation of the long-term average spatial distribution of surface runoff, actual evapotranspiration, and groundwater recharge. The long-term temporal and spatial average annual rainfall of 626 mm was distributed as: surface runoff of 126 mm (20%), evapotranspiration of 468 mm (75%), and recharge of 28 mm (5%). This recharge corresponds to 817 l/s for the 920.12 km2 study area, which is less than the often-assumed 1,000 l/s recharge for the Dire Dawa groundwater catchment.

  10. Groundwater recharge estimation using time series models and hybrid water fluctuation method

    NASA Astrophysics Data System (ADS)

    Yoon, H.; Park, E.; Ha, K.; Kim, G.

    2013-12-01

    Predicting groundwater level fluctuations and estimating groundwater recharge are necessary for an effective management of groundwater resources. Applications of the water table fluctuation (WTF) method to groundwater recharge estimation are limited when time series data of groundwater level is discontinuous or abnormal. In the present study, we designed a method to correct abnormal data using time series models for groundwater recharge estimation. An artificial neural network and a support vector machine were employed for time series model development and the hybrid water table fluctuation method (h-WTF) considering transient fillable porosity was utilized for groundwater recharge estimation. A comparison study was conducted between three different techniques for groundwater recharge estimation: the classic WTF, h-WTF with observed data (h-WTF1), and h-WTF with corrected data (h-WTF2), using daily rainfall and groundwater level data of 5 groundwater monitoring stations in South Korea. Correlation coefficient values of observed and predicted groundwater level were as high as more than 0.8 for all the 5 stations. The result of the comparison study shows that the estimated ratio of recharge to rainfall ranges from 14.9 to 38.3% for WTF, 12.8 to 31.2% for h-WTF1, and 21.8 to 50.0% for h-WTF2 method. The estimated recharge ratios of h-WTF1 are smaller than h-WTF2 by 9.8 to 41.3%. The reason is thought to be that the effect of exogenous factors to groundwater recharge except rainfall was filtered out through the time series model in h-WTF2 method.

  11. Investigations of groundwater system and simulation of regional groundwater flow for North Penn Area 7 Superfund site, Montgomery County, Pennsylvania

    USGS Publications Warehouse

    Senior, Lisa A.; Goode, Daniel J.

    2013-01-01

    Groundwater in the vicinity of several industrial facilities in Upper Gwynedd Township and vicinity, Montgomery County, in southeast Pennsylvania has been shown to be contaminated with volatile organic compounds (VOCs), the most common of which is the solvent trichloroethylene (TCE). The 2-square-mile area was placed on the National Priorities List as the North Penn Area 7 Superfund site by the U.S. Environmental Protection Agency (USEPA) in 1989. The U.S. Geological Survey (USGS) conducted geophysical logging, aquifer testing, and water-level monitoring, and measured streamflows in and near North Penn Area 7 from fall 2000 through fall 2006 in a technical assistance study for the USEPA to develop an understanding of the hydrogeologic framework in the area as part of the USEPA Remedial Investigation. In addition, the USGS developed a groundwater-flow computer model based on the hydrogeologic framework to simulate regional groundwater flow and to estimate directions of groundwater flow and pathways of groundwater contaminants. The study area is underlain by Triassic- and Jurassic-age sandstones and shales of the Lockatong Formation and Brunswick Group in the Mesozoic Newark Basin. Regionally, these rocks strike northeast and dip to the northwest. The sequence of rocks form a fractured-sedimentary-rock aquifer that acts as a set of confined to partially confined layers of differing permeabilities. Depth to competent bedrock typically is less than 20 ft below land surface. The aquifer layers are recharged locally by precipitation and discharge locally to streams. The general configuration of the potentiometric surface in the aquifer is similar to topography, except in areas affected by pumping. The headwaters of Wissahickon Creek are nearby, and the stream flows southwest, parallel to strike, to bisect North Penn Area 7. Groundwater is pumped in the vicinity of North Penn Area 7 for industrial use, public supply, and residential supply. Results of field investigations by USGS at the site and results from other studies support, and are consistent with, a conceptual model of a layered leaky aquifer where the dip of the beds has a strong control on hydraulic connections in the groundwater system. Connections within and (or) parallel to bedding tend to be greater than across bedding. Transmissivities of aquifer intervals isolated by packers ranged over three orders of magnitude [from about 2.8 to 2,290 square feet per day (ft2/d) or 0.26 to 213 square meters per day (m2/d)], did not appear to differ much by mapped geologic unit, but showed some relation to depth being relatively smaller in the shallowest and deepest intervals (0 to 50 ft and more than 250 ft below land surface, respectively) compared to the intermediate depth intervals (50 to 250 ft below land surface) tested. Transmissivities estimated from multiple-observation well aquifer tests ranged from about 700 to 2,300 ft2/d (65 to 214 m2/d). Results of chemical analyses of water from isolated intervals or monitoring wells open to short sections of the aquifer show vertical differences in concentrations; chloride and silica concentrations generally were greater in shallow intervals than in deeper intervals. Chloride concentrations greater than 100 milligrams per liter (mg/L), combined with distinctive chloride/bromide ratios, indicate a different source of chloride in the western part of North Penn Area 7 than elsewhere in the site. Groundwater flow at a regional scale under steady-state conditions was simulated by use of a numerical model (MODFLOW-2000) for North Penn Area 7 with different layers representing saprolite/highly weathered rock near the surface and unweathered competent bedrock. The sedimentary formations that underlie the study area were modeled using dipping model layers for intermediate and deep zones of unweathered, fractured rock. Horizontal cell model size was 100 meters (m) by 100 meters (328 ft by 328 ft), and model layer thickness ranged from 6 m (19.7 ft) representing shallow weathered rock and saprolite up to 200 m (656 ft) representing deeper

  12. Estimating Natural Flows into the California's Sacramento - San Joaquin Delta

    NASA Astrophysics Data System (ADS)

    Huang, G.; Kadir, T.; Chung, F. I.

    2014-12-01

    Natural flows into the California's Sacramento - San Joaquin Delta under predevelopment vegetative conditions, if and when reconstructed, can serve as a useful guide to establish minimum stream flows, restoration targets, and a basis for assessing impacts of global warming in the Bay-Delta System. Daily simulations of natural Delta flows for the period 1922-2009 were obtained using precipitation-snowmelt-runoff models for the upper watersheds that are tributaries to the California's Central Valley, and then routing the water through the Central Valley floor area using a modified version of the California Central Valley Groundwater-Surface Water Simulation Model (C2VSIM) for water years 1922 through 2009. Daily stream inflows from all major upper watersheds were simulated using 23 Soil Water Assessment Tool (SWAT) models. Historical precipitation and reference evapotranspiration data were extracted from the SIMETAW2 with the 4km gridded meteorological data. The Historical natural and riparian vegetation distributions were compiled from several pre-1900 historical vegetation maps of the Central Valley. Wetlands were dynamically simulated using interconnected lakes. Flows overtopping natural levees were simulated using flow rating curves. New estimates of potential evapotranspiration from different vegetative classes under natural conditions were also used. Sensitivity simulations demonstrate that evapotranspiration estimates, native vegetation distribution, surface-groundwater interaction parameters, extinction depth for groundwater uptake, and other physical processes play a key role in the magnitude and timing of upstream flows arriving at the Delta. Findings contradict a common misconception that the magnitude of inflows to the Delta under natural vegetative conditions is greater than those under the historical agricultural and urban land use development. The developed models also enable to study the impacts of global warming by modifying meteorological and climatic conditions that comport with the various projections. The developed set of tools also provides a more systematic, reliable and scientific means for setting the Bay-Delta flow and quality standards and examining ways to improve the health and sustainability of the ecosystem.

  13. Simulation of recharge for the Death Valley regional groundwater flow system using an integrated hydrologic model

    NASA Astrophysics Data System (ADS)

    Hevesi, J. A.; Regan, R. S.; Hill, M. C.; Heywood, C.; Kohn, M. S.

    2012-12-01

    A proof-of-concept study was conducted using the integrated hydrologic model, GSFLOW, to simulate spatially and temporally distributed recharge for the Death Valley regional groundwater flow system (DVRFS). GSFLOW is an integrated groundwater - surface water flow model that combines two modeling applications: the Precipitation-Runoff-Modeling-System (PRMS) and MODFLOW. Previous methods used to estimate recharge for the DVRFS include empirical models based on precipitation, applications of the chloride mass-balance method, and applications of a precipitation-runoff model, INFIL, which used a daily time step to simulate recharge as net infiltration through the root zone. The GSFLOW model offers several potential advantages compared to the previous methods including (1) the ability to simulate complex flow through a thick unsaturated zone (UZ), allowing for the dampening and time delay of recharge relative to the infiltration signal at the top of the UZ and also allowing for the redistribution of flow within the UZ, as enabled by the MODFLOW-NWT and UZF capabilities, (2) the simulation of rejected recharge in response to the dynamics of groundwater discharge and low permeability zones in the UZ, (3) a more explicit representation of streamflow and recharge processes in the mostly ephemeral stream channels that characterize the DVRFS, and (4) the ability to simulate complex flow paths for runoff occurring as both overland flow and shallow subsurface flow (interflow) in the soil zone using a network of cascades connecting hydrologic response units (HRUs). Simulations were done using a daily time step for water years 1980-2010. Preliminary estimates of recharge using GSFLOW indicate that the distribution of recharge is highly variable both spatially and temporally due to variability in precipitation, snowmelt, evapotranspiration, runoff, and the permeability of bedrock and alluvium underlying the root zone. Results averaged over the areas of subbasins were similar to results obtained from previous studies. However, estimates of recharge on the local scale of the HRUs indicate significant (greater than 100 percent) differences at some locations compared to results obtained using INFIL due to differences in (1) the geometry and scale of HRUs, (2) the layout of the cascading flow network and the location of stream channels, (3) the representation of the physical characteristics of the root zone, and (4) model processes controlling the simulation of evapotranspiration and the movement of water through the root zone.

  14. Saturated and subcooled hydrothermal boiling in groundwater flow channels as a source of harmonic tremor

    NASA Astrophysics Data System (ADS)

    Leet, Robert C.

    1988-05-01

    The potential of hydrothermal boiling in groundwater flow channels for generating harmonic tremor (a relatively monochromatic ground vibration associated with volcanic activity) is examined. We use simple "organ pipe" theory of normal-mode fluid vibration and fundamental energy considerations to develop a first-order analytical model of a hydrothermal-boiling source of harmonic tremor. We use this model to estimate order-of-magnitude groundwater flow channel lengths and boiling heat transfer rates required to produce harmonic tremor with dominant frequencies in the range 0.5-5 Hz and surface wave reduced displacements of up to 100 cm2. Depending on groundwater sound speed, flow channel lengths of the order of 1-1000 m are required to produce fluid vibration eigenfrequencies in the range 0.5-5 Hz. The boiling heat transfer rate required to produce tremor with a given surface wave reduced displacement depends on the tremor frequency and on whether saturated boiling or subcooled boiling is the cause of the tremor. Saturated boiling produces groundwater vibration via steam bubble growth, whereas subcooled boiling produces groundwater vibration via steam bubble collapse. We find that subcooled hydrothermal boiling is from 102 to 104 times more efficient than saturated boiling in converting boiling "thermal" power to seismic power. For example, the boiling heat transfer rates required to produce 1-Hz tremor with reduced displacements of up to 100 cm2 via subcooled boiling are generally less than a few thousand megawatts; for saturated boiling, the required boiling heat transfer rates are several orders of magnitude larger than this. The highest values of heat flow reported in the literature for volcanic crater lakes and terrestrial and ocean floor geothermal areas are of the order of 1000 MW. Taking this value as a first-order estimate of an upper limit on possible boiling heat transfer rates in volcanic hydrothermal systems, our results suggest that saturated hydrothermal boiling is capable of generating only low-amplitude harmonic tremor, with surface wave reduced displacements no higher than a few square centimeters. However, subcooled hydrothermal boiling could potentially generate high-amplitude harmonic tremor, with reduced displacements as large as several hundred square centimeters. As a specific application of our model, we evaluate the potential of hydrothermal boiling for generating harmonic tremor at recently active Mount St. Helens and Nevado Del Ruiz volcanoes. We conclude that subcooled boiling likely could have produced the tremor episodes considered at both volcanoes. Saturated boiling also could explain the Nevado Del Ruiz tremor but probably not the more powerful Mount St. Helens tremor.

  15. Determination of groundwater flow regimes in underground storage caverns using tritium and helium isotopes

    Microsoft Academic Search

    Jeonghoon Lee; Byeongju Jung; Jun-Mo Kim; Kyung-Seok Ko; Ho-Wan Chang

    2011-01-01

    Understanding groundwater flow and chemical transport is crucial for operating underground storage caverns. Groundwater flow\\u000a in the study area is mainly affected by cavern operating conditions, and groundwater chemistry in the study area is modified\\u000a by disinfection activities for removing possible biological clogging and by mixing with cement pore water. It is significant\\u000a to discern these two effects because wells

  16. 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.

  17. A new analytical method for groundwater recharge and discharge estimation

    NASA Astrophysics Data System (ADS)

    Liang, Xiuyu; Zhang, You-Kuan

    2012-07-01

    SummaryA new analytical method was proposed for groundwater recharge and discharge estimation in an unconfined aquifer. The method is based on an analytical solution to the Boussinesq equation linearized in terms of h2, where h is the water table elevation, with a time-dependent source term. The solution derived was validated with numerical simulation and was shown to be a better approximation than an existing solution to the Boussinesq equation linearized in terms of h. By calibrating against the observed water levels in a monitoring well during a period of 100 days, we shown that the method proposed in this study can be used to estimate daily recharge (R) and evapotranspiration (ET) as well as the lateral drainage. It was shown that the total R was reasonably estimated with a water-table fluctuation (WTF) method if the water table measurements away from a fixed-head boundary were used, but the total ET was overestimated and the total net recharge was underestimated because of the lack of consideration of lateral drainage and aquifer storage in the WTF method.

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

    E-print Network

    Bense, Victor

    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

  19. The Effectiveness of Electrical Resistivity Tomography In Monitoring Groundwater Flow In Fractured Rocks

    Microsoft Academic Search

    Qi You Zhou; Jun Shimada

    2002-01-01

    Groundwater flow in fractured rocks usually is highly preferential and limited to a few fractures. Traditional sampling method and monitoring using sensors installed at given positions are not enough to identify the groundwater flow in the fractured rocks. A new, noninvasive and promising method is electrical resistivity tomography (ERT). The purpose of this study is to investigate the effectiveness of

  20. Statistical analysis of hydrographs and water-table fluctuation to estimate groundwater recharge

    NASA Astrophysics Data System (ADS)

    Moon, Sang-Ki; Woo, Nam C.; Lee, Kwang S.

    2004-06-01

    Using water-table monitoring data from the National Groundwater Monitoring Network in Korea, groundwater hydrographs were classified into five typical groups. Then, to estimate groundwater recharge, a modified water-table fluctuation (WTF) method was developed from the relation between the cumulative WTF and corresponding precipitation records. Applying this method to different types of hydrographs, the spatial variability of recharge in river basins was evaluated. Each estimated recharge can be considered the maximum value, and therefore, could be used as a cut-off guideline (an upper limit) for groundwater development in river basins.

  1. Topographically driven groundwater flow and the San Andreas heat flow paradox revisited

    USGS Publications Warehouse

    Saffer, D.M.; Bekins, B.A.; Hickman, S.

    2003-01-01

    Evidence for a weak San Andreas Fault includes (1) borehole heat flow measurements that show no evidence for a frictionally generated heat flow anomaly and (2) the inferred orientation of ??1 nearly perpendicular to the fault trace. Interpretations of the stress orientation data remain controversial, at least in close proximity to the fault, leading some researchers to hypothesize that the San Andreas Fault is, in fact, strong and that its thermal signature may be removed or redistributed by topographically driven groundwater flow in areas of rugged topography, such as typify the San Andreas Fault system. To evaluate this scenario, we use a steady state, two-dimensional model of coupled heat and fluid flow within cross sections oriented perpendicular to the fault and to the primary regional topography. Our results show that existing heat flow data near Parkfield, California, do not readily discriminate between the expected thermal signature of a strong fault and that of a weak fault. In contrast, for a wide range of groundwater flow scenarios in the Mojave Desert, models that include frictional heat generation along a strong fault are inconsistent with existing heat flow data, suggesting that the San Andreas Fault at this location is indeed weak. In both areas, comparison of modeling results and heat flow data suggest that advective redistribution of heat is minimal. The robust results for the Mojave region demonstrate that topographically driven groundwater flow, at least in two dimensions, is inadequate to obscure the frictionally generated heat flow anomaly from a strong fault. However, our results do not preclude the possibility of transient advective heat transport associated with earthquakes.

  2. Estimating the dynamics of groundwater input into the coastal zone via continuous radon-222 measurements.

    PubMed

    Burnett, William C; Dulaiova, Henrieta

    2003-01-01

    Submarine groundwater discharge (SGD) into the coastal zone has received increased attention in the last few years as it is now recognized that this process represents an important pathway for material transport. Assessing these material fluxes is difficult, as there is no simple means to gauge the water flux. To meet this challenge, we have explored the use of a continuous radon monitor to measure radon concentrations in coastal zone waters over time periods from hours to days. Changes in the radon inventories over time can be converted to fluxes after one makes allowances for tidal effects, losses to the atmosphere, and mixing with offshore waters. If one assumes that advective flow of radon-enriched groundwater (pore waters) represent the main input of 222Rn in the coastal zone, the calculated radon fluxes may be converted to water fluxes by dividing by the estimated or measured 222Rn pore water activity. We have also used short-lived radium isotopes (223Ra and 224Ra) to assess mixing between near-shore and offshore waters in the manner pioneered by. During an experiment in the coastal Gulf of Mexico, we showed that the mixing loss derived from the 223Ra gradient agreed very favorably to the estimated range based on the calculated radon fluxes. This allowed an independent constraint on the mixing loss of radon-an important parameter in the mass balance approach. Groundwater discharge was also estimated independently by the radium isotopic approach and was within a factor of two of that determined by the continuous radon measurements and an automated seepage meter deployed at the same site. PMID:12860087

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

    SciTech Connect

    None

    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

  4. Estimating groundwater storage changes in the Mississippi River basin (USA) using GRACE

    Microsoft Academic Search

    Matthew Rodell; Jianli Chen; Hiroko Kato; James S. Famiglietti; Joe Nigro; Clark R. Wilson

    2007-01-01

    Based on satellite observations of Earth’s time variable gravity field from the Gravity Recovery and Climate Experiment (GRACE),\\u000a it is possible to derive variations in terrestrial water storage, which includes groundwater, soil moisture, and snow. Given\\u000a auxiliary information on the latter two, one can estimate groundwater storage variations. GRACE may be the only hope for groundwater\\u000a depletion assessments in data-poor

  5. A study of shallow groundwater flow based on groundwater level and geological structures in the Horonobe area, Hokkaido

    NASA Astrophysics Data System (ADS)

    Yokota, Hideharu; Yamamoto, Yoichi; Maekawa, Keisuke

    For assessing the safety of geological disposal of high-level radioactive waste, it is important to understand groundwater flow as a driving force of mass transport. Authors have been carrying out the surface hydrological investigation in the Horonobe area, Hokkaido. Results of groundwater-level observations, and relationship between distributions of groundwater-level and geological structures suggest that constructions of underground facilities have no effect on shallow groundwater-level fluctuations, and that water infiltrate from ground surface into shallow underground in the snow covered season, and that water infiltrate into deeper underground along faults. In the future, it is necessary to be modeling and quantitatively assess the water infiltration and recharge based on directly and/or indirectly observed data of evapotranspiration and soil moisture content by weighing lysimeter and soil moisture meter, and tensiometer.

  6. Testing Predictive Skill of Groundwater Flow and Transport Simulations

    NASA Astrophysics Data System (ADS)

    Hill, M. C.; Ye, M.; Foglia, L.; Lu, D.

    2014-12-01

    Many environmental systems evolve over decades, centuries and longer, in contrast, for example, to weather predictions, which can be compared to reality weekly, daily, and even hourly; hurricane predictions, which can be compared to reality over weeks and days; and El Nino predictions, which can be compared to reality over years. There are many methods that people suggest using to develop models of environmental systems with long-range consequences, yet rarely are these methods tested for their predictive skill in practical problems. Of interest is how to determine if there are model development methods that tend to produce such long-term predictions with greater skill than other model development methods. Here three tests of groundwater flow and transport are discussed and compared. One test uses spatially defined cross-validation to inspect predictive capability, while two tests use paired complex and simple models. Results are analyzed in the context of how increasing model complexity affects predictive skill for the problems considered.

  7. Stochastic Collocation Method for Three-dimensional Groundwater Flow

    NASA Astrophysics Data System (ADS)

    Shi, L.; Zhang, D.

    2008-12-01

    The stochastic collocation method (SCM) has recently gained extensive attention in several disciplines. The numerical implementation of SCM only requires repetitive runs of an existing deterministic solver or code as in the Monte Carlo simulation. But it is generally much more efficient than the Monte Carlo method. In this paper, the stochastic collocation method is used to efficiently qualify uncertainty of three-dimensional groundwater flow. We introduce the basic principles of common collocation methods, i.e., the tensor product collocation method (TPCM), Smolyak collocation method (SmCM), Stround-2 collocation method (StCM), and probability collocation method (PCM). Their accuracy, computational cost, and limitation are discussed. Illustrative examples reveal that the seamless combination of collocation techniques and existing simulators makes the new framework possible to efficiently handle complex stochastic problems.

  8. Estimation of groundwater recharge from water storage structures in a semi-arid climate of India

    Microsoft Academic Search

    V. N. Sharda; R. S. Kurothe; D. R. Sena; V. C. Pande; S. P. Tiwari

    2006-01-01

    Groundwater recharge from water storage structures under semi-arid conditions of western India has been estimated by employing water table fluctuation (WTF) and chloride mass balance (CMB) methods. Groundwater recharge was estimated as 7.3% and 9.7% of the annual rainfall by WTF method for the years 2003 and 2004, respectively while the two years average recharge was estimated as 7.5% using

  9. 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.

  10. 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.

  11. 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. ...

  12. Estimation of groundwater recharge to chalk and sandstone aquifers using simple soil models

    Microsoft Academic Search

    R. Ragab; J. Finch; R. Harding

    1997-01-01

    On the assumption that the water draining below the root zone is potentially available for groundwater recharge, two current UK methods for estimating annual groundwater recharge have been compared with a new soil model using data from four sites under permanent grass in the UK: two sites representative of the Chalk aquifer at Bridgest Farm (Hampshire) and Fleam Dyke (Cambridgeshire),

  13. 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.

  14. 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.

  15. The advantages, and challenges, in using multiple techniques in the estimation of surface water-groundwater fluxes.

    NASA Astrophysics Data System (ADS)

    Shanafield, M.; Cook, P. G.

    2014-12-01

    When estimating surface water-groundwater fluxes, the use of complimentary techniques helps to fill in uncertainties in any individual method, and to potentially gain a better understanding of spatial and temporal variability in a system. It can also be a way of preventing the loss of data during infrequent and unpredictable flow events. For example, much of arid Australia relies on groundwater, which is recharged by streamflow through ephemeral streams during flood events. Three recent surface water/groundwater investigations from arid Australian systems provide good examples of how using multiple field and analysis techniques can help to more fully characterize surface water-groundwater fluxes, but can also result in conflicting values over varying spatial and temporal scales. In the Pilbara region of Western Australia, combining streambed radon measurements, vertical heat transport modeling, and a tracer test helped constrain very low streambed residence times, which are on the order of minutes. Spatial and temporal variability between the methods yielded hyporheic exchange estimates between 10-4 m2 s-1 and 4.2 x 10-2 m2 s-1. In South Australia, three-dimensional heat transport modeling captured heterogeneity within 20 square meters of streambed, identifying areas of sandy soil (flux rates of up to 3 m d-1) and clay (flux rates too slow to be accurately characterized). Streamflow front modeling showed similar flux rates, but averaged over 100 m long stream segments for a 1.6 km reach. Finally, in central Australia, several methods are used to decipher whether any of the flow down a highly ephemeral river contributes to regional groundwater recharge, showing that evaporation and evapotranspiration likely accounts for all of the infiltration into the perched aquifer. Lessons learned from these examples demonstrate the influences of the spatial and temporal variability between techniques on estimated fluxes.

  16. Coupled groundwater flow and transport: 1. Verification of variable density flow and transport models

    Microsoft Academic Search

    Olaf Kolditz; Rainer Ratke; Hans-Jörg G. Diersch; Werner Zielke

    1998-01-01

    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

  17. Integrating hydrogeochemical, hydrogeological, and environmental tracer data to understand groundwater flow for a karstified aquifer system.

    PubMed

    Pavlovskiy, Igor; Selle, Benny

    2015-04-01

    For karstified aquifer systems, numerical models of groundwater flow are difficult to setup and parameterize. However, a system understanding useful for groundwater management may be obtained without applying overly complicated models. In this study, we demonstrate for a karstified carbonate aquifer in south-western Germany that a combination of methods with moderate data requirements can be used to infer flowpaths and transit times of groundwater to production wells. PMID:25178951

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

    Microsoft Academic Search

    Zulfiqar Ahmad; Arshad Ashraf; Alan Fryar; Gulraiz Akhter

    2011-01-01

    The integration of the Geographic Information System (GIS) with groundwater modeling and satellite remote sensing capabilities\\u000a has provided an efficient way of analyzing and monitoring groundwater behavior and its associated land conditions. A 3-dimensional\\u000a finite element model (Feflow) has been used for regional groundwater flow modeling of Upper Chaj Doab in Indus Basin, Pakistan.\\u000a The approach of using GIS techniques

  19. Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers.

    PubMed

    Emad Dehkordi, S; Schincariol, Robert A; Olofsson, Bo

    2015-07-01

    The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10(-7) m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings. PMID:25227154

  20. 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.

  1. Groundwater balance estimation and sustainability in the Sand?kl? Basin (Afyonkarahisar/Turkey)

    NASA Astrophysics Data System (ADS)

    Aksever, Fatma; Davraz, Ay?en; Karaguzel, Remzi

    2015-06-01

    The Sand?kl? (Afyonkarahisar) Basin is located in the southwest of Turkey and is a semi-closed basin. Groundwater is widely used for drinking, domestic and irrigation purposes in the basin. The mismanagement of groundwater resources in the basin causes negative effects including depletion of the aquifer storage and groundwater level decline. To assure sustainability of the basin, determination of groundwater budget is necessary. In this study, the water-table fluctuation (WTF) and the meteorological water budget (MWB) methods were used to estimate groundwater budget in the Sand?kl? basin (Turkey). Conceptual hydrogeological model of the basin was used for understanding the relation between budget parameters. The groundwater potential of the basin calculated with MWB method as 42.10 × 106 m3/year. In addition, it is also calculated with simplified WTF method as 38.48 × 106 m3/year.

  2. Descriptions and characterizations of water-level data and groundwater flow for the Brewster Boulevard and Castle Hayne Aquifer Systems and the Tarawa Terrace Aquifer

    USGS Publications Warehouse

    Faye, Robert E.; Jones, L. Elliott; Suárez-Soto, René J.

    2013-01-01

    This supplement of Chapter A (Supplement 3) summarizes results of analyses of groundwater-level data and describes corresponding elements of groundwater flow such as vertical hydraulic gradients useful for groundwater-flow model calibration. Field data as well as theoretical concepts indicate that potentiometric surfaces within the study area are shown to resemble to a large degree a subdued replica of surface topography. Consequently, precipitation that infiltrates to the water table flows laterally from highland to lowland areas and eventually discharges to streams such as Northeast and Wallace Creeks and New River. Vertically downward hydraulic gradients occur in highland areas resulting in the transfer of groundwater from shallow relatively unconfined aquifers to underlying confined or semi-confined aquifers. Conversely, in the vicinity of large streams such as Wallace and Frenchs Creeks, diffuse upward leakage occurs from underlying confined or semi-confined aquifers. Point water-level data indicating water-table altitudes, water-table altitudes estimated using a regression equation, and estimates of stream levels determined from a digital elevation model (DEM) and topographic maps were used to estimate a predevelopment water-table surface in the study area. Approximate flow lines along hydraulic gradients are shown on a predevelopment potentiometric surface map and extend from highland areas where potentiometric levels are greatest toward streams such as Wallace Creek and Northeast Creek. The distribution of potentiometric levels and corresponding groundwater-flow directions conform closely to related descriptions of the conceptual model.

  3. 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.

  4. 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.

  5. 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)

  6. 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.

  7. 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.

  8. Simulating the effect of climate extremes on groundwater flow through a lakebed

    USGS Publications Warehouse

    Virdi, Makhan L.; Lee, Terrie M.; Swancar, Amy; Niswonger, Richard G.

    2012-01-01

    Groundwater exchanges with lakes resulting from cyclical wet and dry climate extremes maintain lake levels in the environment in ways that are not well understood, in part because they remain difficult to simulate. To better understand the atypical groundwater interactions with lakes caused by climatic extremes, an original conceptual approach is introduced using MODFLOW-2005 and a kinematic-wave approximation to variably saturated flow that allows lake size and position in the basin to change while accurately representing the daily lake volume and three-dimensional variably saturated groundwater flow responses in the basin. Daily groundwater interactions are simulated for a calibrated lake basin in Florida over a decade that included historic wet and dry departures from the average rainfall. The divergent climate extremes subjected nearly 70% of the maximum lakebed area and 75% of the maximum shoreline perimeter to both groundwater inflow and lake leakage. About half of the lakebed area subject to flow reversals also went dry. A flow-through pattern present for 73% of the decade caused net leakage from the lake 80% of the time. Runoff from the saturated lake margin offset the groundwater deficit only about half of that time. A centripetal flow pattern present for 6% of the decade was important for maintaining the lake stage and generated 30% of all net groundwater inflow. Pumping effects superimposed on dry climate extremes induced the least frequent but most cautionary flow pattern with leakage from over 90% of the actual lakebed area.

  9. 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)

  10. Mathematical Modeling for Simulating Groundwater flow in small part of Niger Delta, Nigeria: A Case Study

    NASA Astrophysics Data System (ADS)

    Roy, S.; Ophori, D.

    2010-12-01

    The study focused on the assessment of groundwater flow from over exploitation of water table in the northern part of Niger Delta in Nigeria. Due to semi arid climate and water shortage, the effect of abstraction with respect to recharge is not well assessed and the aquifer storativity and groundwater flow pattern is not known. The local litho-stratigraphy of the area comprises of lateritic on the top soil and gravely medium to coarse sand to the subsequent layers. An area of 2053 square km has been modeled with a grid of 20 rows by 30 columns and twenty layers. Permeability distribution varies from 2.16 to 328.32 m/day. Precipitation is only source for natural recharge to the aquifer, and drawdown from the wells is only the abstraction from the aquifer. Groundwater flow modeling is studied to simulate the three dimensional groundwater flow direction. A steady state, three dimensional groundwater flows is analyzed using the U.S. Geological Survey groundwater flow model, MODFLOW that uses block-centered finite difference scheme for saturated zone. The model computations have converged after 50 iterations. Results from the modeling shows that abstraction is much more than groundwater recharge. Flow pattern of groundwater is towards the southeast potion of the study area. This places plays predominant role in recharge. Discharge area lies in the north east of the study area. The direction of the groundwater is governed by the mid topographic elevations causing the flow towards the east and west side of the study area

  11. 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.

  12. Gravity-driven groundwater flow and slope failure potential. 1. Elastic effective-stress model

    Microsoft Academic Search

    Richard M. Iverson; Mark E. Reid

    1992-01-01

    Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, the authors formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes

  13. Gravity-driven groundwater flow and slope failure potential: 1. Elastic Effective-Stress Model

    Microsoft Academic Search

    Richard M. Iverson; Mark E. Reid

    1992-01-01

    Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, we formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes do

  14. Gravity-Driven Groundwater Flow and Slope Failure Potential 1. Elastic Effective-Stress Model

    Microsoft Academic Search

    Richard M. Iverson; Mark E. Reid

    1992-01-01

    Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, we formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes do

  15. Preliminary assessment of the impacts of deep foundations and land reclamation on groundwater flow

    E-print Network

    Jiao, Jiu Jimmy

    Preliminary assessment of the impacts of deep foundations and land reclamation on groundwater flow are increasing. Land reclamation from the sea and high-rise buildings are common approaches to satis- fying in a groundwater system due to land reclamation and con- struction of building foundations in a coastal area

  16. The effect of fault relayand clay smearing on groundwater flow patterns in the Lower Rhine

    E-print Network

    Bense, Victor

    The effect of fault relayand clay smearing on groundwater flow patterns in the Lower Rhine,Vrije Universiteit Amsterdam, Amsterdam, The Netherlands ABSTRACT Faults strongly impact groundwater £ow in the unconsolidated sediments of the Lower Rhine Embayment. Hydraulic head maps show that many individual faults form

  17. PHAST Version 2--A Program for Simulating Groundwater Flow, Solute Transport, and

    E-print Network

    PHAST Version 2--A Program for Simulating Groundwater Flow, Solute Transport, and Multicomponent Geochemical Reactions Chapter 35 of Section A, Groundwater, of Book 6, Modeling Techniques 100 0 CHLORIDE, IN MILLIGRAMS PER LITER CALCIUM, IN MILLIGRAMS PER LITER ARSENIC, IN MICROGRAMS PER LITER pH 8.0 7.0 9.0 20 0 40

  18. Use of tritium and helium to define groundwater flow conditions in Everglades National Park

    E-print Network

    Swart, Peter K.

    Use of tritium and helium to define groundwater flow conditions in Everglades National Park Rene´ M 2003. [1] The concentrations of tritium (3 H) and helium isotopes (3 He and 4 He) were used as tracers: tritium, helium, groundwater, isotopes, Everglades, South Florida Citation: Price, R. M., Z. Top, J. D

  19. On the Importance of Linear vs Non-Linear Response in Estimating Base Flow Features for Ungauged Catchments in Southern Texas

    Microsoft Academic Search

    R. Anderson; V. Koren; M. Smith; D. Seo

    2003-01-01

    Various equations have been derived and applied in the study of groundwater base flows. Many studies have confirmed the applicability of a linear storage-discharge relationship in describing groundwater outflows into stream channels from adjoining aquifers. This result has been used in studies of base flow to estimate various catchment-scale, effective hydraulic parameters such as saturated hydraulic conductivity, drainable porosity, and

  20. 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.

  1. 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...

  2. Identification and estimation of groundwater inflow to a brackish coastal lagoon: Field observations and numerical steady-state modeling

    NASA Astrophysics Data System (ADS)

    Haider, K.; Duque, C.; Sonnenborg, T.; Engesgaard, P.

    2012-04-01

    Groundwater discharge to a brackish lagoon, Ringkøbing Fjord, Denmark, has been studied using a combination of hydrogeological field investigations and variable-density flow and transport modeling. Discharge is believed to occur mostly near the shoreline decreasing exponentially off-shore. The main focus has thus been on the near-shore flow processes. A conceptual model, which can help determine the dynamics controlling the interaction between the more saline lagoon water and groundwater, is being developed on the basis of different tracers. Sampling of groundwater every two months in the upper 2 m have been carried out and EC-profiles have been used to estimate changes in the width of the groundwater discharge zone. Furthermore, temperature as a tracer, and seepagemeter measurements were used to indirectly and directly estimate groundwater discharge. Field observations show that the salinity of the lagoon is highest in summer, when groundwater discharge is lowest and, vice versa, lowest when the discharge is highest (winter). This indicates that the force of saline intrusion and freshwater discharge is offset in time. The Hydrogeosphere code (HGS) was applied based on a conceptual three-layer model of hydraulic conductivity (mapped on the basis of slug tests). Steady-state modeling of the interaction between the lagoon and groundwater shows that the simulated discharge to the near-shore environment compares well with field observations (on the order of a few cm/day). Furthermore, the modeling results also are in line with the changes in the observed widths of the groundwater discharge zone. A 12 m deep EC-depth profile shows variable salinity in the top followed by increasing salinity approaching the lagoon summer salinity near the bottom of the shallow aquifer. The numerical model shows a similar trend. A sensitivity analysis on the steady-state model was conducted to observe the effects on discharge and salinity distributions by using different heterogeneity scenarios (homogeneous versus layered) and dispersion parameters. The discharge zone is affected in the near shore environment, whereas dispersion mainly impacts the location of the brackish water-freshwater interface. Transient simulations will be carried out in the future to help understand how seasonal dynamics in salinity of the lagoon and discharge affect the width of discharge zone and the salinity distribution below the lagoon bed.

  3. Groundwater

    NSDL National Science Digital Library

    Smoothstone

    This interactive Flash exercise explores groundwater and features models and animations for wet years and dry years as well as a diagram for groundwater terminology. This is a suitable overview or review for an introductory level course for high school or undergraduates.

  4. Characterization of fracture aperture for groundwater flow and transport

    NASA Astrophysics Data System (ADS)

    Sawada, A.; Sato, H.; Tetsu, K.; Sakamoto, K.

    2007-12-01

    This paper presents experiments and numerical analyses of flow and transport carried out on natural fractures and transparent replica of fractures. The purpose of this study was to improve the understanding of the role of heterogeneous aperture patterns on channelization of groundwater flow and dispersion in solute transport. The research proceeded as follows: First, a precision plane grinder was applied perpendicular to the fracture plane to characterize the aperture distribution on a natural fracture with 1 mm of increment size. Although both time and labor were intensive, this approach provided a detailed, three dimensional picture of the pattern of fracture aperture. This information was analyzed to provide quantitative measures for the fracture aperture distribution, including JRC (Joint Roughness Coefficient) and fracture contact area ratio. These parameters were used to develop numerical models with corresponding synthetic aperture patterns. The transparent fracture replica and numerical models were then used to study how transport is affected by the aperture spatial pattern. In the transparent replica, transmitted light intensity measured by a CCD camera was used to image channeling and dispersion due to the fracture aperture spatial pattern. The CCD image data was analyzed to obtain the quantitative fracture aperture and tracer concentration data according to Lambert-Beer's law. The experimental results were analyzed using the numerical models. Comparison of the numerical models to the transparent replica provided information about the nature of channeling and dispersion due to aperture spatial patterns. These results support to develop a methodology for defining representative fracture aperture of a simplified parallel fracture model for flow and transport in heterogeneous fractures for contaminant transport analysis.

  5. Simplified groundwater flow modeling: an application of Kalman filter based identification

    SciTech Connect

    Pimentel, K.D.; Candy, J.V.; Azevedo, S.G.; Doerr, T.A.

    1980-05-01

    The need exists for methods to simplify groundwater contaminant transport models. Reduced-order models are needed in risk assessments for licensing and regulating long-term nuclear waste repositories. Such models will be used in Monte Carlo simulations to generate probabilities of nuclear waste migration in aquifers at candidate repository sites in the United States. In this feasibility study we focused on groundwater flow rather than contaminant transport because the flow problem is more simple. A pump-drawdown test is modeled with a reduced-order set of ordinary differential equations obtained by differencing the partial differential equation. We determined the accuracy of the reduced model by comparing it with the analytic solution for the drawdown test. We established an accuracy requirement of 2% error at the single observation well and found that a model with only 21 states satisfied that criterion. That model was used in an extended Kalman filter with synthesized measurement data from one observation well to identify transmissivity within 1% error and storage coefficient within 10% error. We used several statistical tests to assess the performance of the estimator/identifier and found it to be satisfactory for this application.

  6. Estimating the relative contributions of human withdrawals and climate variability to changes in groundwater

    NASA Astrophysics Data System (ADS)

    Swenson, S. C.; Lawrence, D. M.

    2014-12-01

    Estimating the relative contributions of human withdrawals and climate variability to changes in groundwater is a challenging task at present. One method that has been used recently is a model-data synthesis combining GRACE total water storage estimates with simulated water storage estimates from land surface models. In this method, water storage changes due to natural climate variations simulated by a model are removed from total water storage changes observed by GRACE; the residual is then interpreted as anthropogenic groundwater change. If the modeled water storage estimate contains systematic errors, these errors will also be present in the residual groundwater estimate. For example, simulations performed with the Community Land Model (CLM; the land component of the Community Earth System Model) generally show a weak (as much as 50% smaller) seasonal cycle of water storage in semi-arid regions when compared to GRACE satellite water storage estimates. This bias propagates into GRACE-CLM anthropogenic groundwater change estimates, which then exhibit unphysical seasonal variability. The CLM bias can be traced to the parameterization of soil evaporative resistance. Incorporating a new soil resistance parameterization in CLM greatly reduces the seasonal bias with respect to GRACE. In this study, we compare the improved CLM water storage estimates to GRACE and discuss the implications for estimates of anthropogenic groundwater withdrawal, showing examples for the Middle East and Southwestern United States.

  7. 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.

  8. 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.

  9. Freshwater flow into a coastal embayment: Groundwater and surface water inputs

    SciTech Connect

    Millham, N.P. [Boston Univ., MA (United States); Howes, B.L. [Woods Hole Oceanographic Inst., MA (United States)

    1994-12-01

    Freshwater discharge to a shallow coastal embayment was measured with two upland hydrologic and three embayment physical methods for 2 yr. Parallel measurements from the five methods ranged from 3,900 ({plus_minus}630) to 9,400 ({plus_minus}3,400) m{sup 3} d{sup {minus}1}, and four of the methods showed close agreement and averaged 4,800 ({plus_minus}670) m{sup 3} d{sup {minus}1}. The most precise estimate of discharge was from a chloride balance, while the best understanding of the rate and pattern of groundwater flow was from a Darcian streamtube approach. Groundwater dominated the freshwater budget, accounting for >95% of the total annual input, and was partitioned almost equally between direct seepage to embayment waters and seepage to a stream with final discharge via surface flow. Freshwater inputs decreased rapidly toward the mouth of the estuary and >80% entered into the upper half. The lack of fixed watershed boundaries resulted in large errors in both the location and area of the topographically defined watershed when compared to a watershed defined by water-table mapping. Seasonal variations were found in both the boundaries of the watershed (8%) and in groundwater discharge (6-fold) in response to changing water-table gradients due to recharge. Hydrologic alterations of the upland through the import of water and the increased recharge from impermeable surfaces led to an apparent increase in the total freshwater discharge to the embayment of nearly 50% over {open_quotes}natural{close_quotes}levels. 48 refs., 9 figs., 7 tabs.

  10. Effects of turbulence on hydraulic heads and parameter sensitivities in preferential groundwater flow layers

    USGS Publications Warehouse

    Shoemaker, W.B.; Cunningham, K.J.; Kuniansky, E.L.; Dixon, J.

    2008-01-01

    A conduit flow process (CFP) for the Modular Finite Difference Ground-Water Flow model, MODFLOW-2005, has been created by the U.S. Geological Survey. An application of the CFP on a carbonate aquifer in southern Florida is described; this application examines (1) the potential for turbulent groundwater flow and (2) the effects of turbulent flow on hydraulic heads and parameter sensitivities. Turbulent flow components were spatially extensive in preferential groundwater flow layers, with horizontal hydraulic conductivities of about 5,000,000 m d-1, mean void diameters equal to about 3.5 cm, groundwater temperature equal to about 25??C, and critical Reynolds numbers less than or equal to 400. Turbulence either increased or decreased simulated heads from their laminar elevations. Specifically, head differences from laminar elevations ranged from about -18 to +27 cm and were explained by the magnitude of net flow to the finite difference model cell. Turbulence also affected the sensitivities of model parameters. Specifically, the composite-scaled sensitivities of horizontal hydraulic conductivities decreased by as much as 70% when turbulence was essentially removed. These hydraulic head and sensitivity differences due to turbulent groundwater flow highlight potential errors in models based on the equivalent porous media assumption, which assumes laminar flow in uniformly distributed void spaces. Copyright 2008 by the American Geophysical Union.

  11. Regional groundwater-flow model of the Redwall-Muav, Coconino, and alluvial basin aquifer systems of northern and central Arizona

    USGS Publications Warehouse

    Pool, D.R.; Blasch, Kyle W.; Callegary, James B.; Leake, Stanley A.; Graser, Leslie F.

    2011-01-01

    A numerical flow model (MODFLOW) of the groundwater flow system in the primary aquifers in northern Arizona was developed to simulate interactions between the aquifers, perennial streams, and springs for predevelopment and transient conditions during 1910 through 2005. Simulated aquifers include the Redwall-Muav, Coconino, and basin-fill aquifers. Perennial stream reaches and springs that derive base flow from the aquifers were simulated, including the Colorado River, Little Colorado River, Salt River, Verde River, and perennial reaches of tributary streams. Simulated major springs include Blue Spring, Del Rio Springs, Havasu Springs, Verde River headwater springs, several springs that discharge adjacent to major Verde River tributaries, and many springs that discharge to the Colorado River. Estimates of aquifer hydraulic properties and groundwater budgets were developed from published reports and groundwater-flow models. Spatial extents of aquifers and confining units were developed from geologic data, geophysical models, a groundwater-flow model for the Prescott Active Management Area, drill logs, geologic logs, and geophysical logs. Spatial and temporal distributions of natural recharge were developed by using a water-balance model that estimates recharge from direct infiltration. Additional natural recharge from ephemeral channel infiltration was simulated in alluvial basins. Recharge at wastewater treatment facilities and incidental recharge at agricultural fields and golf courses were also simulated. Estimates of predevelopment rates of groundwater discharge to streams, springs, and evapotranspiration by phreatophytes were derived from previous reports and on the basis of streamflow records at gages. Annual estimates of groundwater withdrawals for agriculture, municipal, industrial, and domestic uses were developed from several sources, including reported withdrawals for nonexempt wells, estimated crop requirements for agricultural wells, and estimated per capita water use for exempt wells. Accuracy of the simulated groundwater-flow system was evaluated by using observational control from water levels in wells, estimates of base flow from streamflow records, and estimates of spring discharge. Major results from the simulations include the importance of variations in recharge rates throughout the study area and recharge along ephemeral and losing stream reaches in alluvial basins. Insights about the groundwater-flow systems in individual basins include the hydrologic influence of geologic structures in some areas and that stream-aquifer interactions along the lower part of the Little Colorado River are an effective control on water level distributions throughout the Little Colorado River Plateau basin. Better information on several aspects of the groundwater flow system are needed to reduce uncertainty of the simulated system. Many areas lack documentation of the response of the groundwater system to changes in withdrawals and recharge. Data needed to define groundwater flow between vertically adjacent water-bearing units is lacking in many areas. Distributions of recharge along losing stream reaches are poorly defined. Extents of aquifers and alluvial lithologies are poorly defined in parts of the Big Chino and Verde Valley sub-basins. Aquifer storage properties are poorly defined throughout most of the study area. Little data exist to define the hydrologic importance of geologic structures such as faults and fractures. Discharge of regional groundwater flow to the Verde River is difficult to identify in the Verde Valley sub-basin because of unknown contributions from deep percolation of excess surface water irrigation.

  12. A modular three-dimensional finite-difference ground-water flow model

    Microsoft Academic Search

    M. G. McDonald; A. W. Harbaugh

    1988-01-01

    A computer program for simulating ground-water flow in three dimensions is presented. This report includes detailed explanations of physical and mathematical concepts on which the model is developed. Ground-water flow within the aquifer is simulated by using a block-centered finite-difference approach. The program is written in Fortran 77 and has a modular structure, which permits the addition of new packages

  13. Coupling Ensemble Kalman filter and groundwater flow moment equations for real time data assimilation

    NASA Astrophysics Data System (ADS)

    Panzeri, Marco; Riva, Monica; Guadagnini, Alberto; Neuman, Shlomo P.

    2013-04-01

    We consider data assimilation through ensemble Kalman filter (EnKF) in the context of groundwater flow through complex geologic media. EnKF enables one to efficiently assimilate diverse data types to characterize earth system models. The approach allows real-time Bayesian updating of system states and parameters as new data are collected. Modeling hydraulic conductivity as a correlated random field conditioned on measured conductivity and/or hydraulic head values renders the corresponding (conditional) groundwater flow equations stochastic. Solving these equations and coupling them with EnKF is typically performed within a numerical Monte Carlo (MC) simulation framework. We circumvent the need for MC through a direct solution of approximate nonlocal (integrodifferential) moment equations (MEs) that govern the space-time evolution of conditional ensemble means (statistical expectations) and covariances of hydraulic heads and fluxes. Embedding the solution of MEs in EnKF provides sequential updates of conductivity and head estimates throughout the space-time domain of interest. This is well suited for cases where real-time measurements can be used immediately to obtain a constantly up-to-date estimate of the aquifer parameters and avoids the need of assimilating all the available data in batch, where the process has to be repeated for all (previous and recent) data when new measurements become available. The methodology is illustrated through a hypothetical two-dimensional example in which a well pumps water from a randomly heterogeneous aquifer of finite extent. We analyze different scenarios, investigating the impact on the parameters estimates of (a) the number of head measurements assimilated, (b) the error variance associated with log conductivity measurements and (c) the initial hydraulic head field. We demonstrate the computational feasibility and accuracy of our methodology and show that hydraulic conductivity estimates are more sensitive to early than to later head values and improve with increasing assimilation frequency at early time. Increasing the variance of log hydraulic conductivity measurement errors by one order of magnitude brought about only a minor deterioration in the quality of corresponding parameter estimates. We test the influence of variogram model and parameters adopted to obtain the initial distributions of log hydraulic conductivity (Y ) mean and covariance on the resulting estimates of (a) hydraulic conductivity and (b) head. Our results show that assuming initial variogram sill and integral scale values different from the true ones has (in general) no adverse effect on the final estimate of Y . In contrast, adopting an incorrect variogram model caused the quality of the parameter estimates to deteriorate during the assimilation of head measurements.

  14. Estimation of groundwater evaportranspiration using diurnal water table fluctuations in the Mu Us Desert, northern China

    NASA Astrophysics Data System (ADS)

    Cheng, Dong-hui; Li, Ying; Chen, Xunhong; Wang, Wen-ke; Hou, Guang-cai; Wang, Cun-liang

    2013-05-01

    Groundwater evapotranspiration (ETg) is a significant component of water balance analysis in desert areas. Estimation of ETg using diurnal water table fluctuations, i.e. the White method, is considered simple and straightforward, but it was seldom applied in desert areas. In this study, long-term and high-resolution groundwater level data were used to estimate ETg rate at two sites covered by typical desert plants Salix psammophila and Artemisia ordosica, respectively, in the Mu Us Desert in northern China. The specific yield (Sy) was derived from a drainage experiment in laboratory. The results showed that the water demand of S. psammophila could result in a weak but identifiable diurnal fluctuation of water table that was 2.35 m below the land surface, reasonable estimates of ETg could be derived from the White method, and the level of the ETg corresponded with the plant growth stages. However, the water table data from the area covered by A. ordosica did not show diurnal fluctuation during the growing season. The White method is good for the desert areas where groundwater use by other processes is negligible, and evapotranspiration is the main process for groundwater consumption. In addition, the information about diurnal water table fluctuations is useful for identification of groundwater-dependence of vegetation. A. ordosica is groundwater-independent, whereas S. psammophila is groundwater-dependent.

  15. Estimation of relative groundwater age in the granite at the Tono research site, central Japan

    NASA Astrophysics Data System (ADS)

    Iwatsuki, T.; Xu, S.; Itoh, S.; Abe, M.; Watanabe, M.

    2000-10-01

    Isotopic studies have been conducted to develop a method to estimate subsurface hydraulic conditions in the granite at the Tono research site, central Japan. The groundwaters were classified into three groups according to residence time, based on the 3H concentration: (1) modern water recharged from the surface within the last 40 years, (2) a mixture between modern water and relatively old groundwaters, and (3) relatively old groundwater which is devoid of 3H. An attempt was made to date the 3H-free groundwater using 14C. The relative groundwater age estimated by simple model, which assumes no addition of dead carbon ranges from 6500 to 14,000 years B.P. The calcite precipitations on the fracture surface are also classified into three groups, based on carbon isotope compositions: (1) precipitation from groundwater within the last 50,000 years, (2) precipitation from the solution with different ? 13C values from groundwater in the past more than 50,000 years, and (3) mixture of new calcite partly precipitated within the last 50,000 years and relatively old calcite. These data suggest the possibility that the conductive (open) fractures connected to the surface can be estimated by 14C determination in the calcite on fracture surfaces.

  16. The Depth of the Cryosphere and the Presence of Groundwater on Present-Day Mars: Revised Estimates and Implications.

    NASA Astrophysics Data System (ADS)

    Clifford, S. M.; Heggy, E.; Boisson, J.; McGovern, P.; Max, M. D.; Marsis Team

    2009-04-01

    It has been estimated that, at the time of peak outflow channel activity, ~2-3 Gya, Mars possess a planetary inventory of water equivalent to a global ocean 0.5-1 km deep (M. Carr, Icarus. 68, 187, 1986). Because this peak post-dates the period when the most efficient mechanisms of planetary water loss (impact erosion and hydrodynamic escape) are thought to be active (>4 Gya), the bulk of this water is likely to still suvive as in the PLD and in the subsurface, as ground ice and groundwater. How much groundwater survives on Mars today depends on the relative size of the planetary inventory of H2O vs. the pore volume of the cryosphere (that region of the crust where the temperature remains below freezing). If the planetary inventory exceeds what can be stored as ice within the cryosphere, then the excess will exist as a groundwater, saturating the lowermost porous regions of the crust. Previous best estimates of mean global heat flow, crustal thermal conductivity, and freezing-point depression, suggested that the nominal depth of the cryosphere varied from ~2.5 km at the equator to ~6.5 km at the poles, with the natural heteorgenity of the crust expected to give rise to significant (±50%) local variations (Clifford (JGR 98, 10973, 1993). Here we revisit these previousr estimates, examining the potential consequences and implications of our evolving understanding of crustal heat flow, thermal conductivity and the effects of groundwater composition on freezing-point depression -- as deduced from recent Mars' surface, orbital, and Earth-based investigations. We conclude that the present day cryosphere may be up to twice as deep as previously thought, raising questions about the continued survival of subpermafrost groundwater -- as a once large inventory may have been cold-trapped into the thickening cryosphere, as the planet's internal heat flow declined with time. If groundwater does continue to persist on Mars, the locations that are likely to provide the best opportunity for its detection 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). The results of MARSIS radar soundings obtained over several of these areas will be discussed.

  17. Conduit and diffuse type groundwater flow regimes in young volcanic terrain

    SciTech Connect

    Hicks, B.G. (Consulting Engineering Geologist, Ashland, OR (United States))

    1993-04-01

    The Big Butte Springs Watershed Geohydrologic Study (Medford Water Commission and Rogue River National Forest, Medford, OR, 1990) compares the movement of the groundwater supplying these major domestic springs to karstic terrain groundwater flow regimes. The similarity of groundwater velocities and the characteristics of responses to precipitation events in young volcanic groundwater systems warrants the use of conduit-like (and diffuse-like) for volcanic terrain to clearly differentiate from the karstic hydrogeologic terms turbulent solution conduit flow and diffuse darcian flow''. The conduit-like systems in young volcanic terrain includes both the clinkery, rubbly interflow zones and the high hydraulic conductivity (K) basal zones. The basal zones are interpreted to originate as follows: (1) thin lava flows onto rivers/streams yielding through-going continuous groundwater passages by steam explosion and thermal shock, and (2) lava flows cover high K river gravel sequences. The (volcanic) diffuse component originates from fracture systems, minor interflow zones or from streams which were tributary to the pre-lava flow main river system. The presentation will highlight comparisons of data from karstic and volcanic terrain and include descriptions of several world-wide high velocity and high K volcanic groundwater systems.

  18. 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.

  19. Post-Injection Migration of CO2 in Saline Aquifers subject to Groundwater Flow, Aquifer Slope, and Capillary Trapping

    NASA Astrophysics Data System (ADS)

    MacMinn, Christopher; Szulczewski, Michael; Juanes, Ruben

    2009-11-01

    We study a sharp-interface mathematical model for the post-injection migration of a plume of CO2 in a deep saline aquifer under the influence of natural groundwater flow, aquifer slope, gravity override, and capillary trapping. The model leads to a nonlinear advection-diffusion equation, where the diffusive term describes the upward spreading of the CO2 against the caprock. We find that the advective terms dominate the flow dynamics even for moderate gravity override, and we solve the model analytically in the hyperbolic limit. We use this solution to estimate the capacity of various target formations in the United States.

  20. Modelling groundwater flow of the Trifa aquifer, Morocco

    Microsoft Academic Search

    Houcyne El Idrysy; Florimond De Smedt

    2006-01-01

    Trifa is the most productive agricultural plain of north-eastern Morocco. The development of agricultural activities during the last few decades has been mainly based on imported water for irrigation. However, irrigation requirements have become so large that groundwater is used as a secondary source to supply the agricultural and domestic water needs, causing a depletion of the groundwater resources, especially

  1. Using Pre-Modeled Scenarios to Estimate Groundwater VOC Concentrations Resulting from Vadose Zone Sources

    SciTech Connect

    Oostrom, Martinus; Truex, Michael J.; Rice, Amy K.; Johnson, Christian D.; Carroll, Kenneth C.; Becker, Dave; Simon, Michelle A.

    2014-04-28

    Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. To support selection of an appropriate endpoint for the SVE remedy, an evaluation is needed to determine whether vadose zone contamination has been diminished sufficiently to protect groundwater. When vapor-phase transport is an important component of the overall contaminant fate and transport from a vadose zone source, the contaminant concentration expected in groundwater is controlled by a limited set of parameters, including specific site dimensions, vadose zone properties, and source characteristics. An approach was developed for estimating the contaminant concentration in groundwater resulting from a contaminant source in the vadose zone based on pre-modeling contaminant transport for a matrix of parameter value combinations covering a range of potential site conditions. An interpolation and scaling process are then applied to estimate groundwater impact for site-specific conditions.

  2. 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.

  3. 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

  4. Groundwater flow and water budget in the surficial and Floridan aquifer systems in east-central Florida

    USGS Publications Warehouse

    Sepulveda, Nicasio; Tiedeman, Claire R.; O'Reilly, Andrew M.; Davis, Jeffrey B.; Burger, Patrick

    2012-01-01

    A numerical transient model of the surficial and Floridan aquifer systems in east-central Florida was developed to (1) increase the understanding of water exchanges between the surficial and the Floridan aquifer systems, (2) assess the recharge rates to the surficial aquifer system from infiltration through the unsaturated zone and (3) obtain a simulation tool that could be used by water-resource managers to assess the impact of changes in groundwater withdrawals on spring flows and on the potentiometric surfaces of the hydrogeologic units composing the Floridan aquifer system. The hydrogeology of east-central Florida was evaluated and used to develop and calibrate the groundwater flow model, which simulates the regional fresh groundwater flow system. The U.S. Geological Survey three-dimensional groundwater flow model, MODFLOW-2005, was used to simulate transient groundwater flow in the surficial, intermediate, and Floridan aquifer systems from 1995 to 2006. The East-Central Florida Transient model encompasses an actively simulated area of about 9,000 square miles. Although the model includes surficial processes-rainfall, irrigation, evapotranspiration (ET), runoff, infiltration, lake water levels, and stream water levels and flows-its primary purpose is to characterize and refine the understanding of groundwater flow in the Floridan aquifer system. Model-independent estimates of the partitioning of rainfall into ET, streamflow, and aquifer recharge are provided from a water-budget analysis of the surficial aquifer system. The interaction of the groundwater flow system with the surface environment was simulated using the Green-Ampt infiltration method and the MODFLOW-2005 Unsaturated-Zone Flow, Lake, and Streamflow-Routing Packages. The model is intended to simulate the part of the groundwater system that contains freshwater. The bottom and lateral boundaries of the model were established at the estimated depths where the chloride concentration is 5,000 milligrams per liter in the Floridan aquifer system. Potential flow across the interface represented by this chloride concentration is simulated by the General Head Boundary Package. During 1995 through 2006, there were no major groundwater withdrawals near the freshwater and saline-water interface, making the general head boundary a suitable feature to estimate flow through the interface. The east-central Florida transient model was calibrated using the inverse parameter estimation code, PEST. Steady-state models for 1999 and 2003 were developed to estimate hydraulic conductivity (K) using average annual heads and spring flows as observations. The spatial variation of K was represented using zones of constant values in some layers, and pilot points in other layers. Estimated K values were within one order of magnitude of aquifer performance test data. A simulation of the final two years (2005-2006) of the 12-year model, with the K estimates from the steady-state calibration, was used to guide the estimation of specific yield and specific storage values. The final model yielded head and spring-flow residuals that met the calibration criteria for the 12-year transient simulation. The overall mean residual for heads, defining residual as simulated minus measured value, was -0.04 foot. The overall root-mean square residual for heads was less than 3.6 feet for each year in the 1995 to 2006 simulation period. The overall mean residual for spring flows was -0.3 cubic foot per second. The spatial distribution of head residuals was generally random, with some minor indications of bias. Simulated average ET over the 1995 to 2006 period was 34.47 inches per year, compared to the calculated average ET rate of 36.39 inches per year from the model-independent water-budget analysis. Simulated average net recharge to the surficial aquifer system was 3.58 inches per year, compared with the calculated average of 3.39 inches per year from the model-independent water-budget analysis. Groundwater withdrawals from the Floridan aquifer system averaged about 920 million gallons per day, which i

  5. Groundwater flow and water budget in the surficial and Floridan aquifer systems in east-central Florida

    USGS Publications Warehouse

    Sepulveda, Nicasio; Tiedeman, Claire R.; O'Reilly, Andrew M.; Davis, Jeffery B.; Burger, Patrick

    2012-01-01

    A numerical transient model of the surficial and Floridan aquifer systems in east-central Florida was developed to (1) increase the understanding of water exchanges between the surficial and the Floridan aquifer systems, (2) assess the recharge rates to the surficial aquifer system from infiltration through the unsaturated zone and (3) obtain a simulation tool that could be used by water-resource managers to assess the impact of changes in groundwater withdrawals on spring flows and on the potentiometric surfaces of the hydrogeologic units composing the Floridan aquifer system. The hydrogeology of east-central Florida was evaluated and used to develop and calibrate the groundwater flow model, which simulates the regional fresh groundwater flow system. The U.S. Geological Survey three-dimensional groundwater flow model, MODFLOW-2005, was used to simulate transient groundwater flow in the surficial, intermediate, and Floridan aquifer systems from 1995 to 2006. The east-central Florida transient model encompasses an actively simulated area of about 9,000 square miles. Although the model includes surficial processes-rainfall, irrigation, evapotranspiration, runoff, infiltration, lake water levels, and stream water levels and flows-its primary purpose is to characterize and refine the understanding of groundwater flow in the Floridan aquifer system. Model-independent estimates of the partitioning of rainfall into evapotranspiration, streamflow, and aquifer recharge are provided from a water-budget analysis of the surficial aquifer system. The interaction of the groundwater flow system with the surface environment was simulated using the Green-Ampt infiltration method and the MODFLOW-2005 Unsaturated-Zone Flow, Lake, and Streamflow-Routing Packages. The model is intended to simulate the part of the groundwater system that contains freshwater. The bottom and lateral boundaries of the model were established at the estimated depths where the chloride concentration is 5,000 milligrams per liter in the Floridan aquifer system. Potential flow across the interface represented by this chloride concentration is simulated by the General Head Boundary Package. During 1995 through 2006, there were no major groundwater withdrawals near the freshwater and saline-water interface, making the general head boundary a suitable feature to estimate flow through the interface. The east-central Florida transient model was calibrated using the inverse parameter estimation code, PEST. Steady-state models for 1999 and 2003 were developed to estimate hydraulic conductivity (K) using average annual heads and spring flows as observations. The spatial variation of K was represented using zones of constant values in some layers, and pilot points in other layers. Estimated K values were within one order of magnitude of aquifer performance test data. A simulation of the final two years (2005-2006) of the 12-year model, with the K estimates from the steady-state calibration, was used to guide the estimation of specific yield and specific storage values. The final model yielded head and spring-flow residuals that met the calibration criteria for the 12-year transient simulation. The overall mean residual for heads, defining residual as simulated minus measured value, was -0.04 foot. The overall root-mean square residual for heads was less than 3.6 feet for each year in the 1995 to 2006 simulation period. The overall mean residual for spring flows was -0.3 cubic foot per second. The spatial distribution of head residuals was generally random, with some minor indications of bias. Simulated average evapotranspiration (ET) over the 1995 to 2006 period was 34.5 inches per year, compared to the calculated average ET rate of 36.6 inches per year from the model-independent water-budget analysis. Simulated average net recharge to the surficial aquifer system was 3.6 inches per year, compared with the calculated average of 3.2 inches per year from the model-independent waterbudget analysis. Groundwater withdrawals from the Floridan aquifer system averaged about 800 milli

  6. 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.

  7. 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.

  8. Comparison of groundwater recharge estimation methods for the semi-arid Nyamandhlovu area, Zimbabwe

    Microsoft Academic Search

    Tenant Sibanda; Johannes C. Nonner; Stefan Uhlenbrook

    2009-01-01

    The Nyamandhlovu aquifer is the main water resource in the semi-arid Umguza district in Matebeleland North Province in Zimbabwe.\\u000a The rapid increase in water demand in the city of Bulawayo has prompted the need to quantify the available groundwater resources\\u000a for sustainable utilization. Groundwater recharge estimation methods and results were compared: chloride mass balance method\\u000a (19–62 mm\\/year); water-table fluctuation method

  9. Regional modeling of groundwater flow and arsenic transport in the Bengal Basin: challenges of scale and complexity (Invited)

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    Widespread arsenic poisoning is occurring in large areas of Bangladesh and West Bengal, India due to high arsenic levels in shallow groundwater, which is the primary source of irrigation and drinking water in the region. The high-arsenic groundwater exists in aquifers of the Bengal Basin, a huge sedimentary system approximately 500km x 500km wide and greater than 15km deep in places. Deeper groundwater (>150m) is nearly universally low in arsenic and a potential source of safe drinking water, but evaluation of its sustainability requires understanding of the entire, interconnected regional aquifer system. Numerical modeling of flow and arsenic transport in the basin introduces problems of scale: challenges in representing the system in enough detail to produce meaningful simulations and answer relevant questions while maintaining enough simplicity to understand controls on processes and operating within computational constraints. A regional groundwater flow and transport model of the Bengal Basin was constructed to assess the large-scale functioning of the deep groundwater flow system, the vulnerability of deep groundwater to pumping-induced migration from above, and the effect of chemical properties of sediments (sorption) on sustainability. The primary challenges include the very large spatial scale of the system, dynamic monsoonal hydrology (small temporal scale fluctuations), complex sedimentary architecture (small spatial scale heterogeneity), and a lack of reliable hydrologic and geologic data. The approach was simple. Detailed inputs were reduced to only those that affect the functioning of the deep flow system. Available data were used to estimate upscaled parameter values. Nested small-scale simulations were performed to determine the effects of the simplifications, which include treatment of the top boundary condition and transience, effects of small-scale heterogeneity, and effects of individual pumping wells. Simulation of arsenic transport at the large scale adds another element of complexity. Minimization of numerical oscillation and mass balance errors required experimentation with solvers and discretization. In the face of relatively few data in a very large-scale model, sensitivity analyses were essential. The scale of the system limits evaluation of localized behavior, but results clearly identified the primary controls on the system and effects of various pumping scenarios and sorptive properties. It was shown that limiting deep pumping to domestic supply may result in sustainable arsenic-safe water for 90% of the arsenic-affected region over a 1000 year timescale, and that sorption of arsenic onto deep, oxidized Pleistocene sediments may increase the breakthrough time in unsustainable zones by more than an order of magnitude. Thus, both hydraulic and chemical defenses indicate the potential for sustainable, managed use of deep, safe groundwater resources in the Bengal Basin.

  10. Groundwater recharge estimation from ephemeral streams. Case study: Wadi Tabalah, Saudi Arabia

    Microsoft Academic Search

    Ali U. Sorman; Mohamed J. Abdulrazzak; H. J. Morel-Seytoux

    1997-01-01

    Estimation of groundwater recharge to an unconfined aquifer is studied using analytical and numerical techniques and results are compared with field observations. There is an acute need for such estimation in water balance studies in arid climates, and the case study in this paper is for such a region. The wetting front movement in the unsaturated zone depends on antecedent

  11. Simulation of ground-water flow in the Intermediate and Floridan aquifer systems in Peninsular Florida

    USGS Publications Warehouse

    Sepulveda, Nicasio

    2002-01-01

    A numerical model of the intermediate and Floridan aquifer systems in peninsular Florida was used to (1) test and refine the conceptual understanding of the regional ground-water flow system; (2) develop a data base to support subregional ground-water flow modeling; and (3) evaluate effects of projected 2020 ground-water withdrawals on ground-water levels. The four-layer model was based on the computer code MODFLOW-96, developed by the U.S. Geological Survey. The top layer consists of specified-head cells simulating the surficial aquifer system as a source-sink layer. The second layer simulates the intermediate aquifer system in southwest Florida and the intermediate confining unit where it is present. The third and fourth layers simulate the Upper and Lower Floridan aquifers, respectively. Steady-state ground-water flow conditions were approximated for time-averaged hydrologic conditions from August 1993 through July 1994 (1993-94). This period was selected based on data from Upper Floridan a quifer wells equipped with continuous water-level recorders. The grid used for the ground-water flow model was uniform and composed of square 5,000-foot cells, with 210 columns and 300 rows.

  12. 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.

  13. Numerical simulation of ground-water flow in La Crosse County, Wisconsin, and into nearby pools of the Mississippi River

    USGS Publications Warehouse

    Hunt, Randall J.; Saad, David A.; Chapel, Dawn M.

    2003-01-01

    This report describes a two-dimensional regional screening model and two associated three-dimensional ground-water flow models that were developed to simulate the ground-water flow systems in La Crosse County, Wisconsin, and Pool 8 of the Mississippi River. Although the geographic extents of the three-dimensional models were slightly different, both were derived from the same geologic interpretation and regional screening model, and their calibrations were performed concurrently. The objectives of the La Crosse County (LCC) model were to assess the effects of recent (1990s) and potential future ground-water withdrawals and to provide a tool suitable to evaluate the effects of proposed water-management programs. The Pool 8 model objectives were to quantify the magnitude and distribution of ground-water flow into the Pool. The Wisconsin Geological and Natural History Survey and the U.S. Geological Survey developed the models cooperatively. The report describes: 1) the conceptual hydrogeologic model; 2) the methods used in simulating flow; 3) model calibration and sensitivity analysis; and 4) model results, such as simulation of predevelopment conditions and location and magnitude of ground-water discharge into Pool 8 of the Mississippi. Three aquifer units underlie the model area: 1) a shallow unconsolidated sand and gravel aquifer; 2) an upper bedrock aquifer, composed of Cambrian and Ordovician sandstone and dolomite; and 3) a lower bedrock aquifer composed of Cambrian sandstone of the Eau Claire Formation and the Mount Simon Formation. A shale layer that is part of the Eau Claire Formation forms a confining unit separating the upper and lower bedrock aquifers. This confining unit is absent in the Black River and parts of the La Crosse and Mississippi River valleys. Precambrian crystalline basement rock forms the lower base of the ground-water flow system. The U.S. Geological Survey ground-water flow model code, MODFLOW, was used to develop the La Crosse County (LCC) and Pool 8 ground-water flow models. Boundary conditions for the MODFLOW model were extracted from an analytic element screening model of the regional flow system surrounding La Crosse County. Model input was obtained from previously published and unpublished geologic and hydrologic data. Pumpages from municipal and high-capacity wells were also simulated. Model calibration included a comparison of modeled and field-measured water levels and field-measured base flows to simulated stream flows. At calibration, most measured water levels compared favorably to model-calculated water levels. Simulated streamflows at two targets were within 3 percent of estimated measured base flows. Mass balance results from the LCC and Pool 8 models indicated that 63 to 74 percent of ground water was from recharge and 19 to 26 percent was from surface-water sources. Ground-water flow out of the model was to rivers and streams (85 to 87 percent) and pumping wells (11 and 13 percent). The model demonstrates the effects of development on ground water in the study area. The maximum simulated water-level decline in the city of La Crosse metropolitan area is 9.3 feet. Simulated stream losses are similar to the amount of ground water pumped by wells. This indicates that ground water withdrawn by La Crosse County wells is water that under predevelopment conditions discharged to streams and lakes. The models provide estimates of the locations and amount of ground-water flow into Pool 8 and the southern portion of Pool 7 of the Mississippi River. Ground-water discharges into all areas of the pools, except along the eastern shore in the vicinity of the city of La Crosse and immediately downgradient from lock and dam 7 and 8. Ground-water flow into the pools is generally greatest around the perimeter with decreasing amounts away from the perimeter. An area of relatively high ground-water discharge extends out towards the center of Pool 7 from the upper reaches of the pool and may

  14. Transylvanian heat flow in the presence of topography, paleoclimate and groundwater flow

    NASA Astrophysics Data System (ADS)

    ?erban, Delia Zemira; Nielsen, Søren B.; Demetrescu, Cri?an

    2001-07-01

    The Transylvanian Depression (TD) is located in the inner part of the Carpathian orogen and shows a marked heat flux low of 30 mW m -2 in the centre, increasing to 60 mW m -2 towards the margins. It is the purpose of the paper to asses the possibility that the observed heat flux in the TD is a consequence of disturbances of the shallow geothermal gradient caused by topography, topographically driven ground water flow and climatic changes. The thermal effects of topography, topographically driven groundwater flow and paleoclimate have been investigated using two-dimensional finite element models. The results show that topography can induce a decrease in heat flux at hill crests and an increase at the bottom of valleys. Topographically driven ground water flow accentuates the effect above ˜1000 m and decreases it below. For the characteristic amplitude and wavelength of topography in Transylvania the heat flux corrections for the cumulated effect of topography and water flow are maximum 1 mW m -2, which is insignificant. Paleoclimate potentially has a large thermal effect. Temperature variations associated with the last glaciation can produce a significantly increasing gradient with depth, which is present in the majority of measured wells. Inversion of six wells confirmed that the curvature in the temperature profiles is consistent with the climatic cooling of the last glaciation. The paleoclimatic effect may induce heat flow corrections in the range 3-7 mW m -2.

  15. Flow Model Development for the Idaho National Laboratory OU 10-08 Sitewide Groundwater Model

    SciTech Connect

    Hai Huang; Swen Magnuson; Thomas Wood

    2005-09-01

    A two-dimensional (2D), steady-state groundwater flow model was developed for the Idaho National Laboratory (INL) sitewide groundwater model. A total of 224 wells inside the model domain were used to calibrate the 2D flow model. Three different calibration techniques, zonation approach, pilot point approach and coupled zonation/pilot point approach, were explored and applied during the model development. The pilot point approach allows modelers to model aquifer heterogeneities at various scales, and extract the maximum amount of data from available monitoring data, permitting the best possible representation of flow and transport at the INL.

  16. Relationships between basic soils-engineering equations and basic ground-water flow equations

    USGS Publications Warehouse

    Jorgensen, Donald G.

    1980-01-01

    The many varied though related terms developed by ground-water hydrologists and by soils engineers are useful to each discipline, but their differences in terminology hinder the use of related information in interdisciplinary studies. Equations for the Terzaghi theory of consolidation and equations for ground-water flow are identical under specific conditions. A combination of the two sets of equations relates porosity to void ratio and relates the modulus of elasticity to the coefficient of compressibility, coefficient of volume compressibility, compression index, coefficient of consolidation, specific storage, and ultimate compaction. Also, transient ground-water flow is related to coefficient of consolidation, rate of soil compaction, and hydraulic conductivity. Examples show that soils-engineering data and concepts are useful to solution of problems in ground-water hydrology.

  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. Impact of Groundwater Flow on Thermal Energy Storage and Borehole Thermal Interference

    NASA Astrophysics Data System (ADS)

    Emad Dehkordi, S.; Schincariol, Robert A.

    2013-04-01

    Borehole heat exchanger (BHE) systems are drawing increasing attention and popularity due to their potential energy efficiency and environmental sustainability, as well as their worldwide applicability. Consequently the concern for sustainable designs and proper implementation is rising too. Furthermore an improperly planned and executed system can be economically unjustifiable. To address these issues related design software and to some extent regulatory guidelines have been developed. Thermal input load function and interaction with the subsurface significantly affect thermal performance and sustainability of geothermal heat pump (GHP) systems. Of particular interest is the interaction of such systems with groundwater flow and its impacts. However the related guidelines and the design software do not seem to properly address this growing concern. Typically regulations do not distinguish between high and no groundwater flow conditions, nor do they specify a groundwater velocity threshold at which it becomes important. A further limitation is that most BHE design software used by industry assume a closed box approach discounting the heat transport in/out by the groundwater flow. To efficiently model grids of multiple BHEs, FEFLOW® 6 and the integrated BHE solution is used. Single and multiple borehole grids with U-tube heat exchanger are modeled and compared here. All boreholes are assigned equal heat extraction and flow rates; loop temperatures are then calculated over the system lifetime to compare the thermal efficiency and evaluate the thermal interference between boreholes. For the purpose of assessing the effect of groundwater flow on thermal storage as well as interference, multiple heat loads (balanced and unbalanced) are simulated. Groundwater velocity and borehole spacing are also varied to identify possible thresholds for each case. The study confirms the significance of groundwater flow in certain conditions. The results can be applied to improve the regulatory guidelines and design methods in regards with hydrogeological aspect of thermal and economical sustainability.

  19. Hydrochemistry, a tool for understanding karst groundwater flows Jacques MUDRY, Chrono-Environment laboratory

    E-print Network

    Paris-Sud XI, Université de

    Hydrochemistry, a tool for understanding karst groundwater flows Jacques MUDRY, Chrono.mudry@univ-fcomte.fr ABSTRACT Karst is a highly heterogeneous medium (i.e. properties vary from one point to another one the behavior of karst flows, both through the vadose and the saturated zones. Keywords: Cave ­ Hydrochemistry

  20. 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...

  1. Krypton-81, Helium-4 and Carbon-14 based estimation of groundwater ages in the Guarani Aquifer System: implications for the He-4 geochronometer

    NASA Astrophysics Data System (ADS)

    Aggarwal, P. K.; Chang, H. K.; Gastmans, D.; Sturchio, N. C.; Araguas, L.; Matsumoto, T.; Lu, Z.; Jiang, W.; Yokochi, R.; Mueller, P.

    2012-12-01

    Characterization of aquifer systems remains a challenge, particularly for large aquifers with limited hydrogeological information. Groundwater age is an important parameter that integrates aquifer recharge and flow dynamics and provides the ability to reliably constrain groundwater models. We have used multiple isotope tracers (C-14, He-4, and Kr-81) to estimate the age of groundwater along a 400-km transect in the north-eastern part of the Guarani Aquifer System (GAS) in Brazil. Carbon-14 measurements were made with an AMS, He-4 by mass-spectrometry, and Kr-81 by atom trap trace analysis (ATTA). Groundwater samples were collected along a groundwater flow path that runs from the outcrop area in the east to the deep confined section in the west, where the aquifer is up to about 1000 m deep. Present groundwater recharge occurs in the outcrop areas, as indicated by the presence of tritium and modern 14C. Carbon-14 activities reach values below detection limit at relatively short distances (a few km) from the outcrop. Abundance of 81Kr (half-life 229 Ka), in samples free of C-14, decreases from 0.81±0.11 (expressed as (81Kr/Kr)sample/(81Kr/Kr)air) in the east to 0.18±0.03 in the western-most sample (estimated age = 566±60 ka). Measured 4He-excess is far above that expected from in-situ production rates in sandstone aquifers and overestimates the age by several orders of magnitude. We used 81Kr ages to calibrate the 4He geochronometer which indicates a basal flux of about 2.8 x10-11 cm3STP He/cm2/a. This flux is lower than most estimates of basal flux in previous studies and will allow a wider use of 4He for groundwater dating and aquifer characterization.

  2. Three-Dimensional Numerical Simulation of Density-Dependent Groundwater Flow and Salt Transport Due to Groundwater Pumping in an Unsaturated Fractured Porous Coastal Aquifer System

    Microsoft Academic Search

    J. Kihm; J. Kim

    2009-01-01

    A series of three-dimensional numerical simulations using a generalized multidimensional hydrodynamic dispersion numerical model is performed to analyze density-dependent groundwater flow and salt transport before and during groundwater pumping in an unsaturated fractured porous coastal aquifer system, which is heterogeneous and anisotropic. The coastal aquifer system is located on the western coast of Korea and is composed of the Quaternary

  3. 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%.

  4. Groundwater

    NSDL National Science Digital Library

    Timothy Heaton

    This site contains 17 questions on the topic of groundwater, which covers aquifers and water tables. This is part of the Principles of Earth Science course at the University of South Dakota. Users submit their answers and are provided immediate feedback.

  5. 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.

  6. Fracture flow and groundwater compartmentalization in the Rollins Sandstone, Lower Mesaverde Group, Colorado, USA

    Microsoft Academic Search

    Alan L. Mayo; Wendell Koontz

    2000-01-01

    This paper presents a site-specific conceptual model of groundwater flow in fractured damage zones associated with faulting\\u000a in a package of sedimentary rocks. The model is based on the results of field and laboratory investigations. Groundwater and\\u000a methane gas inflows from fault-fracture systems in the West Elk coal mine, Colorado, USA, have occurred with increasing severity.\\u000a Inflows of 6, 160

  7. A Transient Groundwater Flow Model for Evaluating River-Aquifer Exchange

    NASA Astrophysics Data System (ADS)

    Zanini, A.; Chelli, A.; Pecoraro, R.; Celico, F.

    2014-12-01

    The study area is an industrial site (in the North of Italy) contaminated through heavy metal and chlorinated hydrocarbons. The site presents an area of about 5 km2 and a complex geology. During 2013 and 2014 the hydrogeological conceptual model was reviewed and the result was a main unconfined aquifer that presents an impervious bottom at about 30 m below ground. A small portion of the aquifer is split by a non-continuous aquitard. Below the impervious bottom, there are confined aquifers that are not polluted. The boundary conditions of the aquifer are constant head upstream (obtained from a regional piezometry) and constant head downstream that represents a lake stage. Moreover a river inside the study area, that could feed or dry the aquifer depending on its stage, manages the groundwater head levels. The study area presents more than 100 pumping wells that have the objective of realizing a hydraulic barrier and to prevent the flow of pollutants downstream. The area is monitored with about 120 monitoring wells, which are used, through a periodic sampling and monitoring, to control the pollution and to estimate the flow direction. During the last year a numerical flow model has been developed by means of MODFLOW 2000 (Harbaugh, 2000) with the aim at becoming a management tool of the hydraulic barrier. The calibration procedure, initially, was performed in steady state condition using the PEST procedure (Doherty, 2007). The goal was to reproduce the monthly observations at the monitoring wells varying the hydraulic conductivity of the main aquifer and of the aquitard. The second step of the calibration was the extension of the calibration to transient data. The period from September 1st 2013 to June 31st 2014 was reproduced. In order to avoid problem with the starting conditions only the observations collected in 2014 were used to estimate the aquifer parameters. The period September 1st 2013 to December 31st was used as warm up in order to obtain reliable starting conditions for the 2014. The result of the work was a model that allows to reproduce with high reliability the collected observations and to understand the groundwater flow direction depending on the river stage.

  8. Hydrogeology and simulation of ground-water flow at the Gettysburg Elevator Plant Superfund Site, Adams County, Pennsylvania

    USGS Publications Warehouse

    Low, Dennis J.; Goode, Daniel J.; Risser, Dennis W.

    2000-01-01

    Ground water in Triassic-age sedimentary fractured-rock aquifers in the area of Gettysburg, Pa., is used as drinking water and for industrial and commercial supply. In 1983, ground water at the Gettysburg Elevator Plant was found by the Pennsylvania Department of Environmental Resources to be contaminated with trichloroethene, 1,1,1-trichloroethane, and other synthetic organic compounds. As part of the U.S. Environmental Protection Agency?s Comprehensive Environmental Response, Compensation, and Liability Act, 1980 process, a Remedial Investigation was completed in July 1991, a method of site remediation was issued in the Record of Decision dated June 1992, and a Final Design Report was completed in May 1997. In cooperation with the U.S. Environmental Protection Agency in the hydrogeologic assessment of the site remediation, the U.S. Geological Survey began a study in 1997 to determine the effects of the onsite and offsite extraction wells on ground-water flow and contaminant migration from the Gettysburg Elevator Plant. This determination is based on hydrologic and geophysical data collected from 1991 to 1998 and on results of numerical model simulations of the local ground-water flow-system. The Gettysburg Elevator Site is underlain by red, green, gray, and black shales of the Heidlersburg Member of the Gettysburg Formation. Correlation of natural-gamma logs indicates the sedimentary rock strike about N. 23 degrees E. and dip about 23 degrees NW. Depth to bedrock onsite commonly is about 6 feet but offsite may be as deep as 40 feet. The ground-water system consists of two zones?a thin, shallow zone composed of soil, clay, and highly weathered bedrock and a thicker, nonweathered or fractured bedrock zone. The shallow zone overlies the bedrock zone and truncates the dipping beds parallel to land surface. Diabase dikes are barriers to ground-water flow in the bedrock zone. The ground-water system is generally confined or semi-confined, even at shallow depths. Depth to water can range from flowing at land surface to more than 71 feet below land surface. Potentiometric maps based on measured water levels at the Gettysburg Elevator Plant indicate ground water flows from west to east, towards Rock Creek. Multiple-well aquifer tests indicate the system is heterogeneous and flow is primarily in dipping beds that contain discrete secondary openings separated by less permeable beds. Water levels in wells open to the pumped bed, as projected along the dipping stratigraphy, are drawn down more than water levels in wells not open to the pumped bed. Ground-water flow was simulated for steady-state conditions prior to pumping and long-term average pumping conditions. The three-dimensional numerical flow model (MODFLOW) was calibrated by use of a parameter estimation program (MODFLOWP). Steady-state conditions were assumed for the calibration period of 1996. An effective areal recharge rate of 7 inches was used in model calibration. The calibrated flow model was used to evaluate the effectiveness of the current onsite and offsite extraction well system. The simulation results generally indicate that the extraction system effectively captures much of the ground-water recharge at the Gettysburg Elevator Plant and, hence, contaminated ground-water migrating from the site. Some of the extraction wells pump at low rates and have very small contributing areas. Results indicate some areal recharge onsite will move to offsite extraction wells.

  9. A method of estimating spatio-temporally distributed groundwater recharge using integrated surface-subsurface modelling

    NASA Astrophysics Data System (ADS)

    Chung, Il Moon; Kim, Nam Won; Lee, Jeongwoo; Sophocleous, Marios

    2010-05-01

    In general, there have been various methods of estimating groundwater recharge such as baseflow separation approaches, water budget analyses based on lumped conceptual models, and the water table fluctuation method (WTF) by using data from groundwater monitoring wells. However, groundwater recharge rates show spatial-temporal variability due to climatic conditions, land use, and hydrogeological heterogeneity, so these methods have various limitations in dealing with these characteristics. To overcome these limitations, we present a novel application of estimating recharge based on water balance components from the combined SWAT-MODFLOW model, which is an integrated surface-ground water model. During the process of computing recharge, the time delay is very important factor. SWAT model uses single linear reservoir storage module with an exponential decay weighting function for accounting time delay through vadose zone. However, single reservoir module has limitation on the long delay time. So we suggest a multi-reservoir storage routing module instead of single one, which represents a more realistic time delay through the vadose zone. By using this module, the parameter related to the delay time could be optimized by checking the correlation between simulated recharge and observed groundwater levels. The final step of this procedure is to compare simulated groundwater levels as well as simulated watershed runoff with observed ones. This method is applied to several watersheds in Korea for the purpose of testing the procedure for proper estimation of spatio-temporal groundwater recharge distribution. As this application procedure of estimating recharge has the advantages of the effectiveness of a watershed model as well as the accuracy of the WTF method, the estimated daily recharge rate could be thought as an improved estimate reflecting the heterogeneity of hydrogeology, climatic conditions, land use, as well as the physical behavior of water in soil layers and aquifers.

  10. 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...

  11. 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.

  12. Groundwater flow systems in turbidites of the Northern Apennines (Italy): natural discharge and high speed railway tunnel drainage

    NASA Astrophysics Data System (ADS)

    Gargini, Alessandro; Vincenzi, Valentina; Piccinini, Leonardo; Zuppi, Gian Maria; Canuti, Paolo

    2008-12-01

    Turbidites crop out extensively in the Northern Apennine mountains (Italy). The huge amounts of groundwater drained by tunnels, built for the high speed railway connection between Bologna and Florence, demonstrate the aquifer-like behaviour of these units, up to now considered as aquitards. A conceptual model of groundwater flow systems (GFS) in fractured aquifers of turbidites is proposed, taking into account both system natural state and the perturbation induced by tunnel drainage. Analysis of hydrological data (springs, streams and tunnel discharge), collected over 10 years, was integrated with analysis of hydrochemical and isotopic data and a stream-tunnel tracer test. Hydrologic recession analysis of undisturbed conditions is a key tool in studying turbiditic aquifer hydrogeology, permitting the discrimination of GFS, the estimation of recharge relative to the upstream reach portion and the identification of springs most vulnerable to tunnel drainage impacts. The groundwater budgeting analysis provides evidence that the natural aquifer discharge was stream-focused through GFS, developed downslope or connected to main extensional tectonic lineaments intersecting stream beds; now tunnels drain mainly active recharge groundwater and so cause a relevant stream baseflow deplenishment (approximately two-thirds of the natural value), possibly resulting in adverse effects on local ecosystems.

  13. Geohydrology and simulation of ground-water flow in the aquifer system near Calvert City, Kentucky

    USGS Publications Warehouse

    Starn, J.J.; Arihood, L.D.; Rose, M.F.

    1995-01-01

    The U.S. Geological Survey, in cooperation with the Kentucky Natural Resources and Environmental Protection Cabinet, constructed a two-dimensional, steady-state ground-water-flow model to estimate hydraulic properties, contributing areas to discharge boundaries, and the average linear velocity at selected locations in an aquifer system near Calvert City, Ky. Nonlinear regression was used to estimate values of model parameters and the reliability of the parameter estimates. The regression minimizes the weighted difference between observed and calculated hydraulic heads and rates of flow. The calibrated model generally was better than alternative models considered, and although adding transmissive faults in the bedrock produced a slightly better model, fault transmissivity was not estimated reliably. The average transmissivity of the aquifer was 20,000 feet squared per day. Recharge to two outcrop areas, the McNairy Formation of Cretaceous age and the alluvium of Quaternary age, were 0.00269 feet per day (11.8 inches per year) and 0.000484 feet per day (2.1 inches per year), respectively. Contributing areas to wells at the Calvert City Water Company in 1992 did not include the Calvert City Industrial Complex. Since completing the fieldwork for this study in 1992, the Calvert City Water Company discontinued use of their wells and began withdrawing water from new wells that were located 4.5 miles east-southeast of the previous location; the contributing area moved farther from the industrial complex. The extent of the alluvium contributing water to wells was limited by the overlying lacustrine deposits. The average linear ground-water velocity at the industrial complex ranged from 0.90 feet per day to 4.47 feet per day with a mean of 1.98 feet per day.

  14. Comparison of local- to regional-scale estimates of ground-water recharge in Minnesota, USA

    Microsoft Academic Search

    Geoffrey N. Delin; Richard W. Healy; David L. Lorenz; John R. Nimmo

    2007-01-01

    Regional ground-water recharge estimates for Minnesota were compared to estimates made on the basis of four local- and basin-scale methods. Three local-scale methods (unsaturated-zone water balance, water-table fluctuations (WTF) using three approaches, and age dating of ground water) yielded point estimates of recharge that represent spatial scales from about 1 to about 1000 m2. A fourth method (RORA, a basin-scale

  15. Improved understanding of groundwater flow in complex superficial deposits using three-dimensional geological-framework and groundwater models: an example from Glasgow, Scotland (UK)

    NASA Astrophysics Data System (ADS)

    Turner, R. J.; Mansour, M. M.; Dearden, R.; Ó Dochartaigh, B. É.; Hughes, A. G.

    2015-05-01

    Groundwater models are useful in improving knowledge of groundwater flow processes, both for testing existing hypotheses of how specific systems behave and predicting the response to various environmental stresses. The recent advent of highly detailed three-dimensional (3D) geological-framework models provides the most accurate representation of the subsurface. This type of modelling has been used to develop conceptual understanding of groundwater in the complex Quaternary deposits of Glasgow, Scotland (UK). Delineating the 3D geometry of the lithostratigraphical units has allowed the most detailed conceptualisation of the likely groundwater flow regime yet attempted for these superficial deposits. Recharge and groundwater flow models have been developed in order to test this conceptual understanding. Results indicate that the direction of groundwater flow is predominantly convergent through the permeable, relatively thick Quaternary deposits of the Clyde valley towards the River Clyde, which runs through Glasgow, with some indication of down-valley flow. A separate nearby system with thick and potentially permeable Quaternary deposits, the Proto-Kelvin Valley, may also be a significant conveyor of groundwater towards the River Clyde, although the absence of local data makes any conclusions conjectural. To improve the robustness of the current model there is a need for an overall increase in good quality groundwater-level data, particularly outside central Glasgow. A prototype groundwater-monitoring network for part of Glasgow is an encouraging development in this regard. This would allow the development of a time-variant groundwater model which could be used to study future modelling scenarios.

  16. 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.

  17. 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).

  18. Groundwater flow and velocity in a 500 ka pre-Illinoian till, eastern Iowa

    USGS Publications Warehouse

    Schilling, K.E.; Tassier-Surine, S.

    2006-01-01

    Few hydrology studies have investigated glacial till older than Illinoian time (> 300,000 BP) despite these older tills overlying a large portion of North America. An 8- and 6-well monitoring well nest installed into a 31 m thick pre-Illinoian till sequence near Cedar Rapids, Iowa was characterized using traditional hydrologic methods and chemical tracers. The aquitard system consists of about 9 m of fine-grained oxidized pre-Illinoian till overlying 22 m of unoxidized till and Devonian dolomite bedrock. Hydraulic conductivity ranged from 10-7 m/s in oxidized till and 10-10 m/s in unoxidized till. Hydraulic head relations indicated downward groundwater flow through the till profile with hydraulic gradients steepest near the unoxidized till/bedrock interface. Tritium and nitrate concentrations indicated recent (< 50 years old) recharge to a depth of 9-12 m below land surface. 18O and 2H results ranged between -6.2 to -7.9% and -38.0 to -50.9%, respectively, and plotted near the local Meteoric Water Line. A 1 per mil shift toward less negative 18O values with depth may suggest a climate change signal contained in the till water but more data are needed to verify this trend. Vertical groundwater velocity through the unoxidized till was estimated to range from 0.4 to 5.7 cm/year. The thickness of unoxidized pre-Illinoian till in Linn County was estimated from available records and contoured against vertical travel times to evaluate the effectiveness of pre-Illinoian till in preventing nitrate migration to underlying bedrock aquifers. ?? Springer-Verlag 2006.

  19. 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

  20. Groundwater flow velocity measurements in a sinkhole at the Weeks Island Strategic Petroleum Reserve Facility, Louisiana

    SciTech Connect

    Ballard, S. [Sandia National Labs., Albuquerque, NM (United States); Gibson, J. [SIE, Inc., Fort Worth, TX (United States). Division of Computalog USA

    1995-02-01

    In 1992, a sinkhole was discovered above a Strategic Petroleum Reserve storage facility at Weeks Island, Louisiana. The oil is stored in an old salt mine located within a salt dome. In order to assess the hydrologic significance of the sink hole, an In Situ Permeable Flow Sensor was deployed within a sand-filled conduit in the salt dome directly beneath the sinkhole. The flow sensor is a recently developed instrument which uses a thermal perturbation technique to measure the magnitude and direction of the full 3-dimensional groundwater flow velocity vector in saturated, permeable materials. The flow sensor measured substantial groundwater flow directed vertically downward into the salt dome. The data obtained with the flow sensor provided critical evidence which was instrumental in assessing the significance of the sinkhole in terms of the integrity of the oil storage facility.

  1. 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

  2. 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.

  3. 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.

  4. Simulation of vertical compaction in models of regional ground-water flow

    USGS Publications Warehouse

    Leake, S.A.

    1991-01-01

    A new computer program was developed to simulate vertical compaction in models of regional ground-water flow. The program accounts for ground-water storage changes and compaction in discontinuous interbeds or in extensive confining beds. The new program is a package for the U.S. Geological Survey modular finite-difference ground-water flow model. Several features of the program make it useful for application in shallow unconfined flow systems. Geostatic load can be treated as a function of water-table elevation, and compaction is a function of computed changes in effective stress at the center of a model layer. Thickness of compressible sediments in an unconfined model layer can vary in proportion to saturated thickness. The new package was tested by comparison with an existing model of one-dimensional compaction.

  5. First status report on regional ground-water flow modeling for the Paradox Basin, Utah

    Microsoft Academic Search

    1984-01-01

    Regional ground-water flow within the principal hydrogeologic units of the Paradox Basin is evaluated by developing a conceptual model of the flow regime in the shallow aquifers and the deep-basin brine aquifers and testing these models using a three-dimensional, finite-difference flow code. Semiquantitative sensitivity analysis (a limited parametric study) is conducted to define the system response to changes in hydrologic

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

    E-print Network

    -coupled, ground-source heat pumps, groundwater, heat pump, heat exchanger, heat transfer, numerical models-loop ground-coupled heat exchangers. Green and Perry (1961) demonstrated that the value of effective thermal on the design and performance of vertical closed-loop ground heat exchangers. Based on the investigation results

  7. 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.

  8. 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.

  9. 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.

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

    SciTech Connect

    Kwicklis, Edward Michael [Los Alamos National Laboratory; Becker, Naomi M [Los Alamos National Laboratory; Ruskauff, Gregory [NAVARRO-INTERA, LLC.; De Novio, Nicole [GOLDER AND ASSOC.; Wilborn, Bill [US DOE NNSA NSO

    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.

  11. Stochastic ground-water flow analysis FY-81 status report. Assessment of effectiveness of geologic isolation systems

    SciTech Connect

    Kincaid, C.T.; Vail, L.W.; Devary, J.L.

    1983-07-01

    Research was conducted at Pacific Northwest Laboratory to develop a research computational package for the stochastic analysis of ground-water flow. Both unsteady and steady-state analysis were examined, and a steady-state research code was developed for the study of stochastic processes. This report describes the theoretical development of both unsteady and steady analyses, and presents the preliminary studies undertaken to verify and exercise the encoded algorithm. The stochastic analysis of ground-water flow is a promising new method which can supply more comprehensive analyses of the ground-water environment. The work reported herein provided experience in the methodology while producing a research-oriented stochastic analysis capability. Single-layer aquifers of horizontal extent were selected for this effort. Kriging has been employed to describe the uncertainty in field data. The resulting stochastic parameters enter the problem physics through boundary conditions and Darcy's equation. The mean and variance of the piezometric head are estimated by the stochastic analysis.

  12. Large-time solutions for groundwater flow problems using the relationship of small p versus large t

    NASA Astrophysics Data System (ADS)

    Yeh, Hund-Der; Wang, Chih-Tse

    2007-06-01

    An approximate solution is useful if the corresponding analytical solution is complicated and difficult to accurately evaluate. In the past, the relationship of small p versus large t was commonly applied to the Laplace domain solution and could successfully obtain a large-time solution in the groundwater area. The large-time solution usually has a simpler form than the analytical solution and is much easier for estimating the transient behavior of the groundwater flow system. However, Chen and Stone (1993) pointed out that the use of this relationship might fail to yield the correct solution in calculating the wellbore flux for the constant head test problem. Later, Mathias and Zimmerman (2003) indicated that a poor result was obtained by Gerke and van Genuchten (1993) when using the relationship of small p versus large t to derive the water transfer coefficient for the dual-porosity media problem. This note is to show the detailed mathematical derivations involved in the issues that Chen and Stone (1993) and Gerke and van Genuchten (1993) addressed and to ensure that the relationship of small p versus large t is correct to obtain a large-time solution for transient groundwater flow problems.

  13. Challenging the distributed temperature sensing technique for estimating groundwater discharge to streams through controlled artificial point source experiment

    NASA Astrophysics Data System (ADS)

    Lauer, F.; Frede, H.-G.; Breuer, L.

    2012-04-01

    Spatially confined groundwater discharge can contribute significantly to stream discharge. Distributed fibre optic temperature sensing (DTS) of stream water has been successfully used to localize- and quantify groundwater discharge from this type "point sources" (PS) in small first-order streams. During periods when stream and groundwater temperatures differ PS appear as abrupt step in longitudinal stream water temperature distribution. Based on stream temperature observation up- and downstream of a point source and estimated or measured groundwater temperature the proportion of groundwater inflow to stream discharge can be quantified using simple mixing models. However so far this method has not been quantitatively verified, nor has a detailed uncertainty analysis of the method been conducted. The relative accuracy of this method is expected to decrease nonlinear with decreasing proportions of lateral inflow. Furthermore it depends on the temperature differences (?T) between groundwater and surface water and on the accuracy of temperature measurement itself. The latter could be affected by different sources of errors. For example it has been shown that a direct impact of solar radiation on fibre optic cables can lead to errors in temperature measurements in small streams due to low water depth. Considerable uncertainty might also be related to the determination of groundwater temperature through direct measurements or derived from the DTS signal. In order to directly validate the method and asses it's uncertainty we performed a set of artificial point source experiments with controlled lateral inflow rates to a natural stream. The experiments were carried out at the Vollnkirchener Bach, a small head water stream in Hessen, Germany in November and December 2011 during a low flow period. A DTS system was installed along a 1.2 km sub reach of the stream. Stream discharge was measured using a gauging flume installed directly upstream of the artificial PS. Lateral inflow was simulated using a pumping system connected to a 2 m3 water tank. Pumping rates were controlled using a magnetic inductive flowmeter and kept constant for a time period of 30 minutes to 1.5 hours depending on the simulated inflow rate. Different temperatures of lateral inflow were adjusted by heating the water in the tank (for summer experiments a cooling by ice cubes could be realized). With this setup, different proportions of lateral inflow to stream flow ranging from 2 to 20%, could be simulated for different ?T's (2-7° C) between stream- and inflowing water. Results indicate that the estimation of groundwater discharge through DTS is working properly, but that the method is very sensitive to the determination of the PS groundwater temperature. The span of adjusted ?T and inflow rates of the artificial system are currently used to perform a thorough uncertainty analysis of the DTS method and to derive thresholds for detection limits.

  14. Assessment Of A Groundwater Flow Model Of The Bangkok Basin, Thailand, Using Carbon14Based Ages And Paleohydrology

    Microsoft Academic Search

    Ward E. Sanford; Somkid Buapeng

    1996-01-01

    A study was undertaken to understand the groundwater flow conditions in the Bangkok Basin, Thailand, by comparing 14C-based and simulated groundwater ages. 14C measurements were made on about 50 water samples taken from wells throughout the basin. Simulated ages were obtained using 1) backward-pathline tracking based on the well locations, and 2) results from a three-dimensional groundwater flow model. Comparisons

  15. Age dating of shallow groundwater with chlorofluorocarbons, tritium\\/helium 3, and flow path analysis, southern New Jersey coastal plain

    Microsoft Academic Search

    Z. Szabo; D. E. Rice; L. N. Plummer; E. Busenberg; S. Drenkard; P. Schlosser

    1996-01-01

    Groundwater age dating through the combination of transient tracer methods [chlorofluorocarbons (CFCs) and tritium\\/helium 3 (3H\\/3He)] and groundwater flow path analysis is useful for investigating groundwater travel times, flow patterns, and recharge rates, as demonstrated by this study of the homogeneous shallow, unconfined Kirkwood-Cohansey aquifer system in the southern New Jersey coastal plain. Water samples for age dating were collected

  16. 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.

  17. Water resources of Borrego Valley and vicinity, San Diego County, California; Phase 2, Development of a ground-water flow model

    USGS Publications Warehouse

    Mitten, H.T.; Lines, G.C.; Berenbrock, Charles; Durbin, T.J.

    1988-01-01

    Because of the imbalance between recharge and pumpage, groundwater levels declined as much as 100 ft in some areas of Borrego Valley, California during drinking 1945-80. As an aid to analyzing the effects of pumping on the groundwater system, a three-dimensional finite-element groundwater flow model was developed. The model was calibrated for both steady-state (1945) and transient-state (1946-79) conditions. For the steady-state calibration, hydraulic conductivities of the three aquifers were varied within reasonable limits to obtain an acceptable match between measured and computed hydraulic heads. Recharge from streamflow infiltration (4,800 acre-ft/yr) was balanced by computed evapotranspiration (3,900 acre-ft/yr) and computed subsurface outflow from the model area (930 acre-ft/yr). For the transient state calibration, the volumes and distribution of net groundwater pumpage were estimated from land-use data and estimates of consumptive use for irrigated crops. The pumpage was assigned to the appropriate nodes in the model for each of seventeen 2-year time steps representing the period 1946-79. The specific yields of the three aquifers were varied within reasonable limits to obtain an acceptable match between measured and computed hydraulic heads. Groundwater pumpage input to the model was compensated by declines in both the computed evapotranspiration and the amount of groundwater in storage. (USGS)

  18. The in situ permeable flow sensor: A ground-water flow velocity meter

    SciTech Connect

    Ballard, S. [Sandia National Labs., Albuquerque, NM (United States). Geophysics Dept.

    1996-03-01

    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 ground-water 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. The sensors are permanently buried in direct contact with the formation at the point where the velocity measurement is to be made. While this deployment strategy means that the approximately $2,500 instruments are not recovered, borehole effects which can negatively influence the quality of the measurement are avoided. The sensors can be connected to a data acquisition system which can be monitored remotely, via modem and telephone connection, for extended periods of time. The technology is able to measure flow velocities in the range of 5 {times} 10{sup {minus}6} to 1 {times} 10{sup {minus}3} cm/s, depending on the thermal properties of the medium in which it is buried.

  19. Linking ground-water age and chemistry data along flow paths: Implications for trends and transformations of nitrate and pesticides

    USGS Publications Warehouse

    Tesoriero, A.J.; Saad, D.A.; Burow, K.R.; Frick, E.A.; Puckett, L.J.; Barbash, J.E.

    2007-01-01

    Tracer-based ground-water ages, along with the concentrations of pesticides, nitrogen species, and other redox-active constituents, were used to evaluate the trends and transformations of agricultural chemicals along flow paths in diverse hydrogeologic settings. A range of conditions affecting the transformation of nitrate and pesticides (e.g., thickness of unsaturated zone, redox conditions) was examined at study sites in Georgia, North Carolina, Wisconsin, and California. Deethylatrazine (DEA), a transformation product of atrazine, was typically present at concentrations higher than those of atrazine at study sites with thick unsaturated zones but not at sites with thin unsaturated zones. Furthermore, the fraction of atrazine plus DEA that was present as DEA did not increase as a function of ground-water age. These findings suggest that atrazine degradation occurs primarily in the unsaturated zone with little or no degradation in the saturated zone. Similar observations were also made for metolachlor and alachlor. The fraction of the initial nitrate concentration found as excess N2 (N2 derived from denitrification) increased with ground-water age only at the North Carolina site, where oxic conditions were generally limited to the top 5??m of saturated thickness. Historical trends in fluxes to ground water were evaluated by relating the times of recharge of ground-water samples, estimated using chlorofluorocarbon concentrations, with concentrations of the parent compound at the time of recharge, estimated by summing the molar concentrations of the parent compound and its transformation products in the age-dated sample. Using this approach, nitrate concentrations were estimated to have increased markedly from 1960 to the present at all study sites. Trends in concentrations of atrazine, metolachlor, alachlor, and their degradates were related to the timing of introduction and use of these compounds. Degradates, and to a lesser extent parent compounds, were detected in ground water dating back to the time these compounds were introduced.

  20. Thermal effects of compaction-driven groundwater flow from overthrust belts

    SciTech Connect

    Deming, D.; Nunn, J.A.; Evans, D.G. (Louisiana State Univ., Baton Rouge (United States))

    1990-05-10

    The thermal consequences of compaction-driven groundwater flow resulting from overthrusting are studied with a two-dimensional numerical model. The model represents a foreland basin 5 km deep and 400 km wide and is used to estimate quantitatively the magnitude, direction, and thermal consequences of fluid expulsion. Model simulations in which the permeability structure is homogeneous lead to maximum Darcy velocities of the order of 1 cm/yr, temperature in the foreland increases by less than 5 C. A sensitivity analysis reveals that temperature in the foreland may be increased an additional 2 C by increasing porosity, speed of thrusting, or heat flow. However, if the area underneath the thrust sheet is not effectively sealed, fluid escapes upward and thermal perturbations in the foreland are negligible. Models with basal and midlevel aquifers produce maximum Darcy velocities of the order of 4 cm/yr, but temperature in the foreland again increases by less than 5 C. Models in which hot fluids at depth are channeled directly upward through a high-permeability pathway can produce temperature perturbations as high as 50 C, over limited areas. Modeling results suggest that the expulsion of pore fluids from orogenic zones through the process of sediment compaction is likely to produce significant thermal perturbations in adjacent forelands only over areas that are spatially restricted, or spatially and temporally restricted.

  1. COMMUNITY-RANDOMIZED INTERVENTION TRIAL WITH UV DISINFECTION FOR ESTIMATING THE RISK OF PEDIATRIC ILLNESS FROM MUNICIPAL GROUNDWATER CONSUMPTION

    EPA Science Inventory

    The goal of this study is to estimate the risk of childhood febrile and gastrointestinal illnesses associated with drinking municipal water from a groundwater source. The risk estimate will be partitioned into two separate components— illness attributable to contaminated...

  2. 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)

  3. Hydrogeology of a coal-seam gas exploration area, southeastern British Columbia, Canada: Part 1. Groundwater flow systems

    NASA Astrophysics Data System (ADS)

    Harrison, S.; Molson, J.; Abercrombie, H.; Barker, J.; Rudolph, D.; Aravena, R.

    2000-12-01

    Discovery of high contents of methane gas in coals of the Mist Mountain Formation in the Elk River valley, southeastern British Columbia, Canada, has led to increased exploration activity for coal-seam gas (CSG). CSG production requires groundwater abstraction to depressurize the coal beds and to facilitate methane flow to the production wells. Groundwater abstraction will have hydrodynamic effects on the flow system, and an understanding of the groundwater flow system is needed to evaluate these effects. The purpose of this paper is to describe the groundwater flow system in the area by means of a groundwater flow model and interpretation of hydrochemical and isotopic analyses of groundwater and surface water. Groundwater flow for the Weary Creek exploration area is modeled in two vertical sections. The model domains, based on classic upland-lowland conceptual flow models, are approximately 10,000 m long and 4,000 m deep. Each consists of a fixed water-table boundary and no-flow boundaries along the traces of major faults. Steady-state groundwater flow is calibrated to hydraulic-head, streamflow, and groundwater-recharge data. Simulated steady-state velocity fields define regional and local flow components consistent with the conceptual model. The results are consistent with regional trends in ?2H, ?18O, tritium, and TDS, which define two distinct groundwater groups (A and B) and a third of intermediate composition. An active, shallow, local flow component (group A) is recharged in beds cropping out along subdued ridges; this component discharges as seeps along lower and mid-slope positions in the southern part of the study area. The waters are tritiated, relatively enriched in ?2H and ?18O, and have low TDS. A deeper regional flow component (group B), which originates at a higher altitude and which discharges to the Elk River valley bottom, is characterized by non-tritiated groundwater with relatively depleted ?2H and ?18O, and higher TDS. Groundwater contributes less than 10% of the total direct flow to the Elk River, as indicated by flow measurements and by the absence of group A and group B characteristics in the river water. Thus it is hypothesized that groundwater extraction during CSG production will have little impact on the river. The groundwater flow model developed in this work is used in a companion paper to further test this hypothesis.

  4. 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.

  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. A preliminary assessment of the effects of groundwater flow on closed-loop ground source heat pump systems

    Microsoft Academic Search

    A. D. Chiasson; S. J. Rees; J. D. Spitler

    2000-01-01

    A preliminary study has been made of the effects of groundwater flow on the heat transfer characteristics of vertical closed-loop heat exchangers and the ability of current design and in-situ thermal conductivity measurement techniques to deal with these effects. It is shown that an initial assessment of the significance of groundwater flow can be made by examining the Peclet number

  7. The conversion of grasslands to forests in Southern South America: Shifting evapotranspiration, stream flow and groundwater dynamics

    NASA Astrophysics Data System (ADS)

    Jobbagy, E. G.; Nosetto, M. D.; Pineiro, G.; Farley, K. A.; Palmer, S. M.; Jackson, R. B.

    2005-12-01

    Vegetation changes, particularly those involving transitions between tree- and grass-dominated systems, often modify evaporation as a result of plant-mediated shifts in moisture access and demand. The establishment of tree plantations (fast growing eucalypts and pines) on native grasslands is emerging as a major land-use change, particularly in the Southern Hemisphere, where cheap land and labor, public subsidies, and prospective C sequestration rewards provide converging incentives. What are the hydrological consequences of grassland afforestation? How are crucial ecosystem services such as fresh water supply and hydrological regulation being affected? We explore these questions focusing on a) evapotranspiration, b) stream flow, and c) groundwater recharge-discharge patterns across a network of paired stands and small watershed occupied by native grassland and tree plantation in Argentina and Uruguay. Radiometric information obtained from Landsat satellite images was used to estimate daily evapotranspiration in >100 tree plantations and grasslands stands in the humid plains of the Uruguay River (mean annual precipitation, MAP= 1350 mm). In spite of their lower albedo, tree plantations were 0.5 C° cooler than grasslands. Energy balance calculations suggested 80% higher evapotranspiration in afforested plots with relative differences becoming larger during dry periods. Seasonal stream flow measurements in twelve paired watershed (50-500 Ha) in the hills of Comechingones (MAP= 800 mm) and Minas (MAP= 1200 mm) showed declining water yields following afforestation. Preliminary data in Cordoba showed four-fold reductions of base flow in the dry season and two-fold reductions of peak flow after storms. A network of twenty paired grassland-plantation stands covering a broad range of sediment textures in the Pampas (MAP= 1000 mm, typical groundwater depth= 1-5 m) showed increased groundwater salinity in afforested stands (plantation:grassland salinity ratio = 1.2, 10, and 1.7 in coarse, fine, and intermediate texture sediments, respectively). Local groundwater depression of 0.1 to 1.7 m under tree plantation was widespread. Afforested stands showed diurnal water level fluctuations (0.015 to 0.08 m, night peak) on intermediate to coarse sediments but not in fine textured ones. Groundwater level and salinity shifts suggest reduced recharge in all afforested stands. Phreatophytic discharge was evident only in coarse and intermediate textured sediments. The impact of grassland afforestation on evapotranspiration, stream flow, and ground water highlights the important role of vegetation as a hydrological driver and suggests critical trade-offs between timber production or C sequestration and freshwater supply. Afforestation, however, can also play a positive role regulating floods, perhaps helping to counteract the hydrological impacts of agriculture, which tend to increase water yield.

  8. Estimation of groundwater residence time using environmental radioisotopes (C,T) in carbonate aquifers, southern Poland

    Microsoft Academic Search

    Katarzyna Samborska; Andrzej Ró?kowski; Piotr Maoszewski

    2012-01-01

    Triassic carbonate aquifers in the Upper Silesia region, affected by intense withdrawal, have been investigated by means of isotopic analyses of C, ?C, ?H, ?O and H. The isotopic examinations were carried out in the 1970s and in the early 1980s, and it was the first application of tracers to estimate age and vulnerability for the contamination of groundwater in

  9. 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...

  10. Submarine groundwater discharge to Great South Bay, NY, estimated using Ra isotopes

    Microsoft Academic Search

    Aaron J. Beck; John P. Rapaglia; J. Kirk Cochran; Henry J. Bokuniewicz; Suhui Yang

    2008-01-01

    There is increasing evidence that submarine groundwater discharge (SGD) in many areas represents a major source of dissolved chemical constituents to the coastal ocean. In Great South Bay, NY, previous studies have shown that the discharge of nutrients with SGD may cause harmful algal blooms. This study estimates SGD to Great South Bay during August 2006 by performing a mass

  11. MODFLOW-2000, the U.S. Geological Survey Modular Ground-Water Model -Documentation of the Hydrogeologic-Unit Flow (HUF) Package

    USGS Publications Warehouse

    Anderman, E.R.; Hill, M.C.

    2000-01-01

    This report documents the Hydrogeologic-Unit Flow (HUF) Package for the groundwater modeling computer program MODFLOW-2000. The HUF Package is an alternative internal flow package that allows the vertical geometry of the system hydrogeology to be defined explicitly within the model using hydrogeologic units that can be different than the definition of the model layers. The HUF Package works with all the processes of MODFLOW-2000. For the Ground-Water Flow Process, the HUF Package calculates effective hydraulic properties for the model layers based on the hydraulic properties of the hydrogeologic units, which are defined by the user using parameters. The hydraulic properties are used to calculate the conductance coefficients and other terms needed to solve the ground-water flow equation. The sensitivity of the model to the parameters defined within the HUF Package input file can be calculated using the Sensitivity Process, using observations defined with the Observation Process. Optimal values of the parameters can be estimated by using the Parameter-Estimation Process. The HUF Package is nearly identical to the Layer-Property Flow (LPF) Package, the major difference being the definition of the vertical geometry of the system hydrogeology. Use of the HUF Package is illustrated in two test cases, which also serve to verify the performance of the package by showing that the Parameter-Estimation Process produces the true parameter values when exact observations are used.

  12. 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-

  13. Integrating Address Geocoding, Land Use Regression, and Spatiotemporal Geostatistical Estimation for Groundwater Tetrachloroethylene

    PubMed Central

    Messier, Kyle P.; Akita, Yasuyuki; Serre, Marc L.

    2012-01-01

    Geographic Information Systems (GIS) based techniques are cost-effective and efficient methods used by state agencies and epidemiology researchers for estimating concentration and exposure. However, budget limitations have made statewide assessments of contamination difficult, especially in groundwater media. Many studies have implemented address geocoding, land use regression, and geostatistics independently, but this is the first to examine the benefits of integrating these GIS techniques to address the need of statewide exposure assessments. A novel framework for concentration exposure is introduced that integrates address geocoding, land use regression (LUR), below detect data modeling, and Bayesian Maximum Entropy (BME). A LUR model was developed for Tetrachloroethylene that accounts for point sources and flow direction. We then integrate the LUR model into the BME method as a mean trend while also modeling below detects data as a truncated Gaussian probability distribution function. We increase available PCE data 4.7 times from previously available databases through multistage geocoding. The LUR model shows significant influence of dry cleaners at short ranges. The integration of the LUR model as mean trend in BME results in a 7.5% decrease in cross validation mean square error compared to BME with a constant mean trend. PMID:22264162

  14. Stable and unbiased flow turbulence estimation from pulse echo ultrasound

    Microsoft Academic Search

    Yi Zheng; James F. Greenleaf

    1999-01-01

    A new method for stable and unbiased flow turbulence estimation has been developed for medical ultrasonic color flow imaging. Conventional turbulence estimates from a finite number of transmitted pulses could be biased, unreliable, and erroneous. We found that a conventional method cannot provide quantitative estimates of variance of flow velocity. We propose a new approach for flow turbulence estimation that

  15. Regional groundwater flow in mountainous terrain: Three-dimensional simulations of topographic and hydrogeologic controls

    NASA Astrophysics Data System (ADS)

    Gleeson, Tom; Manning, Andrew H.

    2008-10-01

    This study uses numerical simulations to define the salient controls on regional groundwater flow in 3-D mountainous terrain by systematically varying topographic and hydrogeologic variables. Topography for idealized multiple-basin mountainous terrain is derived from geomatic data and literature values. Water table elevation, controlled by the ratio of recharge to hydraulic conductivity, largely controls the distribution of recharged water into local, regional, and perpendicular flow systems, perpendicular flow being perpendicular to the regional topographic gradient. Both the relative (%) and absolute (m3/d) values of regional flow and perpendicular flow are examined. The relationship between regional flow and water table elevation is highly nonlinear. With lower water table elevations, relative and absolute regional flow dramatically increase and decrease, respectively, as the water table is lowered further. However, for higher water table elevations above the top of the headwater stream, changes in water table elevation have little effect on regional flow. Local flow predominates in high water table configurations, with regional and perpendicular flow <15% and <10%, respectively, of total recharge in the models tested. Both the relative and the maximum absolute regional flow are directly controlled by the degree of incision of the mountain drainage network; the elevation of mountain ridges is considerably less important. The percentage of the headwater stream with perennial streamflow is a potentially powerful indicator of regional flow in all water table configurations and may be a good indicator of the susceptibility of mountain groundwater systems to increased aridity.

  16. Fluid flow in fault zones: Analysis of the interplay of convective circulation and topographically driven groundwater flow

    Microsoft Academic Search

    Dina L. López; Leslie Smith

    1995-01-01

    High-permeability faults, acting as preferential pathways for fluid migration, are important geological structures for fluid, energy, and solute transport. This paper examines the interaction of thermally driven convective circulation in a steeply dipping fault zone and groundwater flow through the surrounding country rock that is driven by a regional topographic gradient. We consider a geometry where a fault zone with

  17. Groundwater flow systems in the great Aletsch glacier region (Valais, Switzerland)

    NASA Astrophysics Data System (ADS)

    Alpiger, Andrea; Loew, Simon

    2014-05-01

    Groundwater flow systems in Alpine areas are often complex and challenging to investigate due to special topographic and climatic conditions governing groundwater recharge and bedrock flow. Studies seeking to characterize high-alpine groundwater systems remain rare, but are of high interest, e.g. for water supply, hydropower systems, traffic tunnels or rock slope deformation and landslide hazards. The goal of this study is to better understand the current and past groundwater flow systems of the UNESCO World Heritage mountain ridge separating the great Aletsch glacier and the Rhone valley, considering climatic and glacier fluctuations during the Lateglacial and Holocene periods. This ridge is crossed by a hydropower bypass drift (Riederhornstollen) and is composed of fractured crystalline rocks overlain by various types of landslides and glacial deposits. Surface hydrology observations (fracture properties, groundwater seepage, spring lines and physico-chemical parameters) and hydropower drift inflow measurements contributed to the characterization of bedrock hydraulic conductivities and preferential groundwater pathways. Basic conceptual hydrogeological models were tested with observed drift inflows and the occurrence of springs using free-surface, variably saturated, vertical 2D groundwater flow models (using the code SEEP/W from GeoStudio 2007). Already simple two-layer models, representing profile sections orthogonal to the mountain ridge, provided useful results. Simulations show that differences in the occurrence of springs on each side of the mountain ridge are likely caused by the occurrence of glacial till (generating perched groundwater), the deep-seated sagging landslide mass, faults and asymmetric ridge topography, which together force the main groundwater flow direction to be oriented towards the Rhone valley, even from beyond the mountain ridge. Surprisingly, the most important springs (those with high discharge rates) are located at high elevations above the terraces of Riederalp and Bettmeralp in or near steeply dipping fault zones striking parallel to the ridge, suggesting locally a near-surface groundwater table. Drying up of several of these springs (at lateral distances up to 4 km) after construction of the Riederhornstollen, as well as associated large tunnel water inflows, demonstrates large scale hydraulic connections along strike of these fault zones. The catchment areas of these springs have to be located close to the ridge crest, above the terraces of Riederalp and Bettmeralp, and extend over many kilometers. This fault system thus drains significant portions of the high-altitude recharge and induces a complex 3D groundwater flow field of the Aletsch area. Variations in glacial ice extent due to different climatic conditions during the Lateglacial and Holocene periods were studied by varying the boundary condition of the great Aletsch glacier. Results have to be interpreted with care, as the glacier pressure boundary conditions were modelled like a lake. Detailed investigations of these boundary conditions have been initialized by glacier drillings equipped with melt water pressure sensors. With the simplified boundary conditions applied to the glacier bed, elevated ice surfaces during the Little Ice Age stage only slightly influence the flow field and total hydraulic head conditions on the NW side of the ridge. On the other hand, the Egesen stadial causes a fundamental change of the groundwater devide with all flow lines, even from below the Aletsch glacier, oriented towards the Rhone valley.

  18. The significance of viscosity in density-dependent flow of groundwater

    NASA Astrophysics Data System (ADS)

    Ophori, Duke U.

    1998-01-01

    Many modeling studies of variable-density groundwater flow have been performed in the last few decades. In most of these studies, fluid density is considered to vary with concentration, while the variation of viscosity with concentration is neglected. The consequences of this negligence is not completely known. The present study uses a numerical simulation approach to investigate the density-viscosity-concentration relationship during groundwater flow and solute transport through a density-stratified system. Fluid density is assumed to increase with depth from freshwater at the surface, through brackish and saline waters, to brines at the bottom half of the system. The system mimics field observations at the Atikokan Research Area (ARA) in northwestern Ontario, Canada. Hypothetical 'unit basin' models, consisting of recharge-, midline- and discharge-area regimes are employed. Simulations with the density-concentration equation of state and a constant (freshwater) viscosity in the density-stratified system causes groundwater to sink against the buoyancy forces of the system. More water is recharged into the system than necessitated by the buoyancy. The configurations and lengths of travel paths, and travel time of conservative contaminants are inaccurately predicted. Accounting for concentration in the viscosity equation causes groundwater floating in agreement with the expected buoyancy physics of the system. Overestimation of concentration-dependent density causes sinking, whereas, overestimation of viscosity results in overfloating and underestimation of groundwater recharge. Even in density-stratified fluids with salinity of seawater, recharge and through flow of water may be slightly overestimated if a concentration-dependent depsity is used along with a constant freshwater viscosity. The concentration dependence of both density and viscosity are to be analyzed carefully during groundwater flow and solute transport simulations in systems with considerable fluid density variations.

  19. 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.

  20. 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.

  1. 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.

  2. Estimation of groundwater quality trends using alternative travel-time distribution models applied to tracers of groundwater age

    NASA Astrophysics Data System (ADS)

    Green, C. T.; Jurgens, B.; Zhang, Y.; Landon, M. K.; Starn, J. J.

    2012-12-01

    The travel time distribution (TTD) from a source area to a sample location can control the evolution and magnitude of non-point source solute concentrations. Tracers of groundwater age have been used in many studies to estimate TTD's of water and solute in samples, but the relative value of different TTD modeling approaches is not well understood. In this study, the uncertainties of predictions of TTD models calibrated to tracers of groundwater age were evaluated. Four mathematical models of TTD were used, including a novel semi-analytical solution accounting for two-dimensional transport between the water table and well screen and scaling of macrodispersivity during transport, a standard one-dimensional advection-dispersion model, an exponential-piston model, and a dual-exponential-piston model. To evaluate prediction uncertainty, the TTD models were calibrated using synthetic age tracer concentrations generated using TTDs for 84 monitoring well samples and one supply well sample simulated with previously developed local-scale numerical transport models of the central-eastern San Joaquin Valley, CA. These models had multiple realizations of realistically complex geology and used particle-tracking methods to estimate transport between the water table and existing well screens. Errors in predicted TTD's and nitrate concentrations were compared among the individual TTD models and among multi-model TTD's derived using established selection criteria including equal weights averaging (EWA), Granger-Ramanathan averaging with negative and positive weights (GRAneg) or only positive weights (GRA), Akaike information criterion selection (AIC) or weights (WAIC), and Kashyap information criterion weights (WKIC). For monitoring well and supply well scenarios, the dispersion based TTD models gave marginally lower prediction errors for TTD's. For predictions of nitrate concentrations, however, errors of the four calibrated TTD models were either not significantly different (for monitoring wells) or varied depending on the amount of error assigned to tracer concentrations (for the supply well). Among the multi-model approaches, use of GRA, WAIC and WKIC all gave TTD and nitrate predictions with minimum errors. When these methods were applied to an actual dataset of multiple tracers from the surrounding region, the estimated historical trend of median nitrate in wells was similar to measured values. With the existing reaction rates and nitrogen applications, upward nitrate concentration trends are predicted to continue for decades. The modeling approach of using multiple tracers of groundwater age with multiple mathematical models of TTD's allows efficient prediction of nitrate trends at regional scales while controlling errors in predictions.

  3. 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.

  4. 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.

  5. Estimating flow through an earthen dam

    NSDL National Science Digital Library

    Kaye Savage

    Students make measurements of dam dimensions and water levels above and below a small, accessible earthen dam. They assess the soil texture in the field. They follow up by developing a simple flow net and estimating seepage rate as part of a problem set. They discuss their assumptions and the likely sources and magnitude of error.

  6. Application of the mixed hybrid finite element approximation in a groundwater flow model: Luxury or necessity?

    Microsoft Academic Search

    R. Mosé; P. Siegel; P. Ackerer; G. Chavent

    1994-01-01

    Selected groundwater flow scenarios are used in a two-way comparison between the mixed hybrid finite element method and the standard finite element method (also called the conforming finite element method). The simulations presented are performed in the bidimensional case with a triangular space discretization because of its practical interest for hydrogeologists. The basic idea of the mixed procedure is to

  7. 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...

  8. 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.

  9. 1-D, 2-D, and 3-D analytical solutions of unsaturated flow in groundwater

    Microsoft Academic Search

    Fred T. Tracy

    1995-01-01

    An excellent tool for checking numerical models of unsaturated flow in groundwater is analytical solutions. However, because of the highly nonlinear nature of the governing partial differential equation, only a limited number of analytical solutions are available. This paper first gives some simple 1-D solutions. Next, by use of a transformation, the nonlinear partial differential equation is converted to a

  10. Groundwater flow model (GWFM) development, Midnite Mine, Wellpinit, WA. Report of investigations/1996

    SciTech Connect

    Kirschner, F.E.

    1996-06-01

    The ultimate purpose of this research effort was to develop a groundwater flow model (GWFM) for the Midnite Mine that can be utilized by the contractor preparing the Environment Impact Statement (EIS) and by other interested parties. The objectives of this study were to (1) develop a shell model of the geology at the site, (2) develop the basis for a GWFM that will meet criteria described elsewhere in this RI and that can be updated with new information generated during the EIS process, and (3) present the results of two steady-state simulations of groundwater flow within the bedrock units. The current GWFM generates nonunique solutions because flow data for the bedrock units currently do not exist. However, the model provides useful results with respect to directions of flow.

  11. Tide-induced salt-fingering flow during submarine groundwater discharge

    NASA Astrophysics Data System (ADS)

    Greskowiak, Janek

    2014-09-01

    This study investigated the stability of the upper saline plume (USP) within shallow tide-affected submarine groundwater discharge (SGD) zones. In contrast to earlier studies, numerical modeling revealed a number of realistic hydrological and hydrogeological conditions where the USP becomes unstable and salt-fingering flow occurs. These conditions were reasonably well identified in a stability diagram based on two dimensionless numbers that characterize the system. If fingering flow occurs, the SGD pattern is distinctly different from that of stable flow conditions: (i) freshwater discharge zones along the beach face are manifold and change their location with time, (ii) undulating freshwater/seawater interface that is extended along the groundwater flow path, and (iii) the total tide-averaged fresh SGD rate varies considerably in an irregular pattern. This has presumably important implications on reactive transport processes in the subterranean estuary, as well as on the interpretation of field data on water and solute fluxes during SGD.

  12. Hydrogeology and simulation of ground-water flow near the Lantana Landfill, Palm Beach County, Florida

    USGS Publications Warehouse

    Russell, G.M.; Wexler, E.J.

    1993-01-01

    The Lantana landfill in Palm Beach County has a surface that is 40 to 50 feet above original ground level and consists of about 250 acres of compacted garbage and trash. Parts of the landfill are below the water table. Surface-resistivity measurements and water-quality analyses indicate that leachate-enriched ground water along the eastern perimeter of the landfill has moved about 500 feet eastward toward an adjacent lake. Concentrations of chloride and nutrients within the leachate-enriched ground water were greater than background concentrations. The surficial aquifer system in the area of the landfill consists primarily of sand of moderate permeability, from land surface to a depth of about 68 feet deep, and consists of sand interbedded with sandstone and limestone of high permeability from a depth of about 68 feet to a depth of 200 feet. The potentiometric surface in the landfill is higher than that in adjacent areas to the east, indicating ground-water movement from the landfill toward a lake to the east. Steady-state simulation of ground-water flow was made using a telescoping-grid technique where a model covering a large area is used to determine boundaries and fluxes for a finer scale model. A regional flow model encompassing a 500-square mile area in southeastern Palm Beach County was used to calculate ground-water fluxes in a 126.5-square mile subregional area. Boundary fluxes calculated by the subregional model were then used to calculate boundary fluxes for a local model of the 3.75-square mile area representing the Lantana landfill site and vicinity. Input data required for simulating ground-water flow in the study area were obtained from the regional flow models, thus, effectively coupling the models. Additional simulations were made using the local flow model to predict effects of possible remedial actions on the movement of solutes in the ground-water system. Possible remedial actions simulated included capping the landfill with an impermeable layer and pumping five leachate recovery wells. Results of the flow analysis indicate that the telescoping grid modeling approach can be used to simulate ground-water flow in small areas such as the Lantana landfill site and to simulate the effects of possible remedial actions. Water-quality data indicate the leachate-enriched ground water is divided vertically into two parts by a fine sand layer at about 40 to 50 feet below land surface. Data also indicate the extent of the leachate-enriched ground-water contamination and concentrations of constituents seem to be decreasing over time.

  13. Seasonal changes in groundwater storage estimated by absolute ground gravity and MRS surveys in West Africa

    NASA Astrophysics Data System (ADS)

    Favreau, G.; Boucher, M.; Luck, B.; Pfeffer, J.; Genthon, P.; Hinderer, J.

    2009-04-01

    Important and fast groundwater storage changes occur in tropical monsoon regions in response to seasonal rainfall and subsequent surface water redistribution. In West Africa, one main goal of the GHYRAF experiment (Gravity and Hydrology in Africa, 2008-2010) is to compare absolute gravimetric measurements with dense hydrological surveys to better estimate and model water storage changes at various time scales. Magnetic Resonance Sounding (MRS) is a non-invasive geophysical method having a signal directly related to groundwater quantity. In SW Niger, MRS surveys were performed concurrently with gravimetric (FG5) measurements for monitoring seasonal changes in groundwater storage. Water table levels were recorded on a 4-piezometers profile (~500 m) near a temporary pond (area ~2 ha) fed by sandy gullies. The volume of water drained from the pond to the phreatic aquifer was computed to be ~100,000 m3/yr. Large piezometric fluctuations (3-6 m) occurred in response to indirect recharge through the pond during the 2008 rainy season (July-Sept.), with stronger water table fluctuations recorded near the pond. Absolute gravimetric (FG5) measurements were performed at a distance of 150 m from the pond, in order to minimize the influence of 2D effects on gravimetric records. The increase in absolute gravity measured between two dates (July-Sept.) was 8.7 ± 2.6 µGal; for the same period, the measured water table rise was +3.0 m. Considering these values, a first estimate of the groundwater storage increase is 0.2 m, corresponding to a porosity filled up by the water table rise of ~7%. Repeated MRS surveys were performed at the same location for different dates (three soundings in Sept., one in Dec.). The MRS water content was 13%, with little variation in space (±3%) along the piezometric profile. In response to a 3 metres drop in the water table (Sept- Dec), there was no significant recorded change in the MRS water content and/or in the estimated MRS water table depth. MRS and absolute gravimetry are two independent methods that could be sensitive to changes in groundwater reserves. However, because MRS is integrative of the whole saturated thickness of the aquifer (here, a few tens of metres), it was shown to be comparatively less sensitive to groundwater storage fluctuations occurring at the water table. These methods provide complementary data on aquifer characteristics, MRS being useful for quantifying lateral changes in aquifer properties, whereas gravimetric measurements helped in characterizing groundwater recharge and porosity. Both methods bring pieces of information that could be used to better constrain transient groundwater modelling at site scale.

  14. Estimated Recharge Rates From Groundwater Temperatures In The Nara Basin, Japan

    NASA Astrophysics Data System (ADS)

    Taniguchi, Makoto

    1994-04-01

    Groundwater recharge rates to the sandy aquifer in the Nara basin, Japan, were determined by using a theory that describes the simultaneous transfer of heat and water in a porous medium. Seasonal changes in temperatue-depth profiles were used to estimate the recharge rates in a relatively shallow aquifer. Estimations of the recharge rates were done by fitting a dimensionless parameter to the type curves developed by Taniguchi (1993) after the amplitudes of annual variations of groundwater temperatures were measured at several depths. Annual recharge rate estimated by fitting observed temperatures to the type curves was 459 mm in the Nara basin. This value agrees well with values calculated from water-balance methods and values reported in the literature.

  15. Estimating profile soil moisture and groundwater variations using GRACE and Oklahoma Mesonet soil moisture data

    NASA Astrophysics Data System (ADS)

    Swenson, Sean; Famiglietti, James; Basara, Jeffrey; Wahr, John

    2008-01-01

    In this study we estimate a time series of regional groundwater anomalies by combining terrestrial water storage estimates from the Gravity Recovery and Climate Experiment (GRACE) satellite mission with in situ soil moisture observations from the Oklahoma Mesonet. Using supplementary data from the Department of Energy's Atmospheric Radiation Measurement (DOE ARM) network, we develop an empirical scaling factor with which to relate the soil moisture variability in the top 75 cm sampled by the Mesonet sites to the total variability in the upper 4 m of the unsaturated zone. By subtracting this estimate of the full unsaturated zone soil moisture anomalies, we arrive at a time series of groundwater anomalies, spatially averaged over a region approximately 280,000 km2 in area. Results are compared to observed well level data from a larger surrounding region, and show consistent phase and relative inter-annual variability.

  16. Geohydrological characterization, water-chemistry, and ground-water flow simulation model of the Sonoma Valley area, Sonoma County, California

    USGS Publications Warehouse

    Farrar, Christopher D.; Metzger, Loren F.; Nishikawa, Tracy; Koczot, Kathryn M.; Reichard, Eric G.; Langenheim, Victoria E.

    2006-01-01

    The Sonoma Valley, located about 30 miles north of San Francisco, is one of several basins in Sonoma County that use a combination of ground water and water delivered from the Russian River for supply. Over the past 30 years, Sonoma Valley has experienced rapid population growth and land-use changes. In particular, there has been a significant increase in irrigated agriculture, predominantly vineyards. To provide a better understanding of the ground-water/surface-water system in Sonoma Valley, the U.S. Geological Survey compiled and evaluated existing data, collected and analyzed new data, and developed a ground-water flow model to better understand and manage the ground-water system. The new data collected include subsurface lithology, gravity measurements, groundwater levels, streamflow gains and losses, temperature, water chemistry, and stable isotopes. Sonoma Valley is drained by Sonoma Creek, which discharges into San Pablo Bay. The long-term average annual volume of precipitation in the watershed is estimated to be 269,000 acre-feet. Recharge to the ground-water system is primarily from direct precipitation and Sonoma Creek. Discharge from the ground-water system is predominantly outflow to Sonoma Creek, pumpage, and outflow to marshlands and to San Pablo Bay. Geologic units of most importance for groundwater supply are the Quaternary alluvial deposits, the Glen Ellen Formation, the Huichica Formation, and the Sonoma Volcanics. In this report, the ground-water system is divided into three depth-based geohydrologic units: upper (less than 200 feet below land surface), middle (between 200 and 500 feet), and lower (greater than 500 feet). Synoptic streamflow measurements were made along Sonoma Creek and indicate those reaches with statistically significant gains or losses. Changes in ground-water levels in wells were analyzed by comparing historical contour maps with the contour map for 2003. In addition, individual hydrographs were evaluated to assess temporal changes by region. In recent years, pumping depressions have developed southeast of Sonoma and southwest of El Verano. Water-chemistry data for samples collected from 75 wells during 2002-04 indicate that the ground-water quality in the study area generally is acceptable for potable use. The water from some wells, however, contains one or more constituents in excess of the recommended standards for drinking water. The chemical composition of water from creeks, springs, and wells sampled for major ions plot within three groups on a trilinear diagram: mixed-bicarbonate, sodium-mixed anion, and sodium-bicarbonate. An area of saline ground water in the southern part of the Sonoma Valley appears to have shifted since the late 1940s and early 1950s, expanding in one area, but receding in another. Sparse temperature data from wells southwest of the known occurrence of thermal water suggest that thermal water may be present beneath a larger part of the valley than previously thought. Thermal water contains higher concentrations of dissolved minerals than nonthermal waters because mineral solubilities generally increase with temperature. Geohydrologic Characterization, Water-Chemistry, and Ground-Water Flow Simulation Model of the Sonoma Valley Area, Sonoma County, California Oxygen-18 (d18 O) and deuterium (dD) values for water from most wells plot along the global meteoric water line, indicating that recharge primarily is derived from the direct infiltration of precipitation or the infiltration of seepage from creeks. Samples from shallow- and intermediate-depth wells located near Sonoma Creek and (or) in the vicinity of Shellville plot to the right of the global meteoric water line, indicating that these waters are partly evaporated. The d18 O and dD composition of water from sampled wells indicates that water from wells deeper than 200 feet is isotopically lighter (more negative) than water from wells less than 200 feet deep, possibly indicating that older ground wate

  17. Estimating century-long changes in groundwater storage using a one-parameter ET model

    NASA Astrophysics Data System (ADS)

    Sharma, A. N.; Walter, M. T.

    2013-12-01

    Long-term information on regional groundwater resources is important for water resources management. This information is unfortunately also scarce in most places. Even in regions with active groundwater monitoring programs, data cover only a few decades and there is considerable uncertainty about the reliability of regional extrapolations from point data. Long-term water budget analyses, thus, are often confounded by the need to estimate both the change in water storage and evapotranspiration (ET) simultaneously, i.e., the 'one equation - two unknown-variables' problem. To address this we used a simple monthly water budget approach using a combination of Gravity Recovery and Climate Experiment (GRACE) satellite data, ground-based measures of stream discharge and precipitation, and a simple ET model. This approach allowed us to estimate ET for several large basins in the U.S. over the past decade. These estimates were used to calibrate the one-parameter ET-storage model of Tuttle and Salvucci (2012, WRR W05556). Using this calibrated ET model in conjunction with precipitation and stream discharge records, we then estimated annual changes in water storage over the entire 20th century. These are corroborated against estimates made using long-term groundwater and weather datasets. It is anticipated that the method used here will be especially useful for water resources management in regions with poor or few historical data.

  18. Spreading of Three-dimensional Plumes in Two-dimensional Chaotic Flows in Groundwater

    NASA Astrophysics Data System (ADS)

    Accardo, M. P.; Neupauer, R. M.; Meiss, J. D.; Mays, D. C.

    2013-12-01

    Two-dimensional chaotic flows have been shown to promote plume spreading in aquifers. During in situ remediation of contaminated groundwater, a treatment solution can be injected into the aquifer to react with and degrade the contaminant. Inducing chaotic flow in this system has been shown to promote plume spreading and to increase the amount of contaminant mass that is degraded. While groundwater flow can often be approximated as two-dimensional in the horizontal plane, contaminant plumes are generally three-dimensional in nature. We investigate the spreading behavior of three-dimensional plumes in two-dimensional chaotic flows. We evaluate the relationship between the unstable manifolds of the chaotic flows and the stretching of the fluid interface between the treatment solution and the contaminated groundwater. Because the flow is two-dimensional, the manifolds are identical at every depth in the aquifer; however, the positions of the fluid interface relative to the manifolds changes with depth, leading to more complicated, three-dimensional structure of the fluid interface. In addition, we evaluate the relationship between the amount of stretching and the amount of degradation of the contaminant. We consider both homogeneous and heterogeneous aquifers. We demonstrate that as the degree of heterogeneity increases, the spreading of the plume and the extent of contaminant degradation also increase.

  19. 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.

  20. Tafilalet OASIS System: Water Resources Management and Investigation by GIS and Groundwater Flow Model

    NASA Astrophysics Data System (ADS)

    Bouaamlat, I.; Larabi, A.; Faouzi, M.

    2014-12-01

    The geographical location of Tafilalet oasis system (TOS) in the south of the valley of Ziz (Morocco) offers him a particular advantage on the plane of water potential. The surface water which comes from humid regions of the High Atlas and intercepted by a dam then converged through the watercourse of Ziz towards the plain of the TOS, have created the conditions for the formation of a water table relatively rich with regard to the local climatic conditions (arid climate with recurrent drought). Given the role of the water table in the economic development of the region, a hydrogeological study was conducted to understand the impact of artificial recharge and recurrent droughts on the development of the groundwater reserves of TOS. In this study, a three-dimensional model of groundwater flow was developed for the TOS, to assist the decision makers as a "management tool" in order to assess alternative schemes for development and exploitation of groundwater resources based on the variation of artificial recharge and drought. The results from this numerical investigation of the TOS aquifer shows that the commissioning of the dam to control the flows of extreme flood and good management of water releases, has avoided the losses of irrigation water and consequently the non-overexploitation of the groundwater. So that with one or two water releases per year from the dam of flow rate more than 28 million m3/year it is possible to reconstruct the volume of water abstracted by wells. The idea of lowering water table by pumping wells is not exactly true, as well the development of groundwater abstraction has not prevented the wound of water table in these last years, the pumping wells accompanied more than it triggers the lowering of water table and it is mainly the succession of dry periods causing the decreases of the piezometric level. This situation confirms the important role that groundwater plays as a "buffer" during the drought periods.

  1. Fracture Mapping with Laser Scan Technology and Discrete Fracture Network Modeling to Support Groundwater Recharge Estimates

    NASA Astrophysics Data System (ADS)

    Voeckler, H. M.; Allen, D.; Forster, C.; Sturzenegger, M.

    2006-12-01

    A Discrete Fracture Network (DFN) approach is used to estimate the hydraulic properties of fractured, low- permeability bedrock in order to assess the spatial variability of recharge for an experimental watershed in mountainous terrain of the Okanagan Valley in central British Columbia. Fracture mapping was undertaken at 30 outcrop locations using traditional scan line mapping techniques. Most of the rocks in the study area belong to the geological unit of the Shuswap Complex, a Proterozoic to Paleozoic high grade metamorphic core complex, consisting of migmatitic gneisses and pegmatites. Further east in the study area, the Okanagan Batholith is predominant, a Paleocene to Early Eocene leucogranite. The fractured aquifer appears to be associated with the 290-km long Okanagan Valley Fault Zone (OVFZ), a north-south striking ductile shear zone with a superimposed, west-dipping, low-angle detachment fault. The study area is located in the footwall of the fault about 500m east of its main trace. Our goal is to assess how spatial variations in fracture network porosity and permeability may be related to the OVFZ. Shallow dipping fractures that have the greatest persistence and apparent aperture are mostly oriented sub-parallel to the low-angle detachment fault. Near vertical fractures have higher intensity, but lower persistence and smaller apparent apertures. Fracture statistical analysis, supported by FracMan® software, is combined with finite element flow simulations (using MAFIC®) to compute apparent permeability values parallel and perpendicular to the OKFZ. We expect the results of our analyses to show that the vertical fracture networks provide key pathways for groundwater to recharge the more prevalent low-angle fracture networks that comprise the main aquifer system. For two of those 30 outcrop locations, a 3D terrestrial laser scanner (ILRIS 3D) was used to map the fracture network across the rock face. At a rate of at least 1000 points/second, the laser scanner captures millions of laser distance measurements of a rock site. The software package Split-FXTM then calculates, for each scan, the fracture orientation, spacing, persistence and roughness. Part of this study should also be a comparison of the fracture measurements and the results of adjacent DFN modeling between the traditional scan line mapping technique and the 3D laser scan technology. This study is part of a project funded by the Canadian Water Network (CWN), which aims to quantify groundwater recharge to the Okanagan valley aquifers. The Okanagan Valley is a very dry and warm region in summer, supporting intensive agricultural activities, mostly vineyards and orchards. The valley bottom water supply, used mostly for irrigation, but also partly for the rising domestic use, is derived from about 4000 wells located in those aquifers. Estimates of recharge through the fractured bedrock mountains bordering the valley are needed to quantify the volume of groundwater entering the valley bottom aquifers as Mountain Block Recharge (MBR).

  2. 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.

  3. 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.

  4. Deuterium Concentration And Flow Path Analysis As Additional Calibration Targets To Calibrate Groundwater Flow Simulation In A Coastal Wetlands System

    NASA Astrophysics Data System (ADS)

    Marimuthu, S.; Reynold, D. A.

    2005-12-01

    A conceptual model of a Coastal Wetlands system (Lake Warden wetlands system, Western Australia) has been developed using hydraulic, chemical and stable isotopic data and this has been used as the basis to develop a groundwater flow model using the finite element numerical code (FEFLOW). The model was utilised to identify the role of groundwater within the system and assist in the mitigation of the effects of the non-seasonal floods. The system to be modeled is complex in the sense that the surface water and groundwater within the wetlands system show varying salinity and isotopic composition over short distances and time frames. As a first step, the flow model was calibrated to observed groundwater levels since 2001 for both steady state and transient stresses. A particle tracking analysis was conducted to test the source areas of water discharging to the lakes within the wetlands system. The analysis was able to delineate the connectivity between the lakes in the wetland and the flow path. The isotopic analysis (deuterium concentration) of the system has identified all of the water sources that flow through the system. The continual enrichment of isotopic concentrations is quite visible along a northeast-southwest transect and the data set provides a means for calibrating a detailed transport model. The study employed a novel method to incorporate the varying deuterium concentration of the water bodies directly into a transport model and a good match between observed and simulated temporal variations along the transect indicates that the model closely simulated the dynamics of water exchange between the lakes and groundwater within the system. Utilization of deuterium as a calibration target has improved and enhanced the confidence of the overall model calibration of a complex, inter-linked system such as Lake Warden wetlands system.

  5. 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.

  6. 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.

  7. Annual drought flow and groundwater storage trends in the eastern half of the United States during the past two-third century

    NASA Astrophysics Data System (ADS)

    Brutsaert, Wilfried

    2010-03-01

    Low flow drainage from a river system, in the absence of precipitation or snowmelt, derives directly from the water stored in the upstream aquifers in the basin; therefore, observations of the trends of the annual lowest flows can serve to deduce quantitative estimates of the evolution of the basin-scale groundwater storage over the period of the streamflow record. Application of this method has allowed for the first time to determine the magnitudes of the trends in groundwater storage over the past two-third century in some 41 large prototypical basins in the United States east of the Rocky Mountains. It was found that during the period 1940-2007 groundwater storage has generally been increasing in most areas; these positive trends were especially pronounced in the Ohio and Upper Mississippi Water Resources Regions, but they were weaker in most other regions. Notable exceptions are the northern New England and especially the South Atlantic-Gulf regions, which saw prolonged declines in groundwater levels over this nearly 70-year long period. These observed long-term trends are generally in agreement with previous studies regarding trends of other components of the water cycle, such as precipitation, total runoff, and terrestrial evaporation. Over the most recent 20 years, from 1988 through 2007, except for the Ohio and the Souris-Red-Rainy regions, most regions have experienced declining average groundwater levels to varying degrees, with maximal values of the order of -0.2 mm a-1.

  8. Estimated Mean Annual Natural Ground-Water Recharge in the Conterminous United States

    USGS Publications Warehouse

    Wolock, David M.

    2003-01-01

    This 1-kilometer resolution raster (grid) dataset is an index of mean annual natural ground-water recharge. The dataset was created by multiplying a grid of base-flow index (BFI) values by a grid of mean annual runoff values derived from a 1951-80 mean annual runoff contour map. Mean annual runoff is long-term average streamflow expressed on a per-unit-area basis.

  9. Borehole Heat Exchangers: heat transfer simulation in the presence of a groundwater flow

    NASA Astrophysics Data System (ADS)

    Angelotti, A.; Alberti, L.; La Licata, I.; Antelmi, M.

    2014-04-01

    The correct design of the Borehole Heat Exchanger is crucial for the operation and the energy performance of a Ground Source Heat Pump. Most design methods and tools are based on the assumption that the ground is a solid medium where conduction is the only heat transfer mechanism. In turn in regions rich in groundwater the groundwater flow influence has to be assessed, by including the convection effects. In this paper a numerical model of a 100 m U-pipe in a saturated porous medium is presented. The model is created adopting MT3DMS coupled to MODFLOW. A Darcy flow is imposed across the medium. The typical operation of a Borehole Heat Exchanger operating both in winter and in summer is simulated for two years, under different groundwater velocities. The energy injected to and extracted from the ground is derived as a function of the Darcy velocity and compared with the purely conductive case. Temperature fields in the ground at key moments are shown and discussed. From both the energy and the aquifer temperature field points of view, the velocity ranges for respectively negligible and relevant influence of the groundwater flow are identified.

  10. Groundwater Flow and Transport Calculations Supporting the Immobilized Low-Activity Waste Disposal Facility Performance Assessment

    SciTech Connect

    Bergeron, Marcel P.; Wurstner, Signe K.

    2000-12-04

    This report summarizes the Hanford Site-Wide Groundwater Model and its application to the Immobilized Low-Activity Waste (ILAW) Disposal Facility Performance Assessment (PA). The site-wide model and supporting local-scale models are used to evaluate impacts from the transport of contaminants at a hypothetical well 100 m downgradient of the disposal facilities and to evaluate regional flow conditions and transport from the ILAW disposal facilities to the Columbia River. These models were used to well-intercept factors (WIFs) or dilution factors from a given areal flux of a hypothetical contaminant released to the unconfined aquifer from the ILAW disposal facilities for two waste-disposal options: 1) a remote-handled trench concept and 2) a concrete-vault concept. The WIF is defined as the ratio of the concentration at a well location in the aquifer to the concentration of infiltrating water entering the aquifer. These WIFs are being used in conjunction with calculations of released contaminant fluxes through the vadose zone to estimate potential impacts from radiological and hazardous chemical contaminants within the ILAW disposal facility at compliance points.

  11. Cluster-based fuzzy models for groundwater flow in the unsaturated zone

    NASA Astrophysics Data System (ADS)

    Vernieuwe, H.; Verhoest, N. E. C.; De Baets, B.; Hoeben, R.; De Troch, F. P.

    2007-04-01

    In this paper fuzzy models are used as an alternative to describe groundwater flow in the unsaturated zone. The core of these models consists of a fuzzy rule-based model of the Takagi-Sugeno type. Various fuzzy clustering algorithms are compared in the data-driven identification of these Takagi-Sugeno models. The performance of the resulting fuzzy models is evaluated on the training surface on which they were identified, and on time series measurements of water content values obtained through an experiment carried out by the non-vegetated terrain (NVT) workgroup of the European Microwave Signature Laboratory (EMSL) (see [Mancini M, Hoeben R, Troch PA. Multifrequency radar observations of bare surface soil moisture content: a laboratory experiment. Water Resour Res 1999;35(6):1827-38] and [Hoeben R, Troch PA. Assimilation of active microwave observation data for soil moisture profile estimation. Water Resour Res 2000;36(10):2805-19]). Despite higher errors at the borders of high water content values in the training surface, good results are obtained on the simulation of the time series.

  12. Fractal dimension estimation of groundwater depth series of well irrigation area in Sanjiang Plain based on continuous wavelet transform

    Microsoft Academic Search

    Dong Liu; Tianxiao Li; Qiang Fu

    2010-01-01

    In order to reveal the groundwater depth series complexity characteristic of well irrigation area in Sanjiang Plain, taking Jiansanjiang branch bureau as example, the fractal dimension estimation method of hydrological series based on continuous wavelet transform was adopted to analyze the complexity of groundwater depth series in 7 production teams of Jiansanjiang branch bureau. The results show that the wavelet

  13. Method of estimating delay time for groundwater recharge through vadose zone in the Hancheon watershed in Jeju island, South Korea

    NASA Astrophysics Data System (ADS)

    Kim, Nam Won; Na, Hanna; Chung, Il-Moon; Lee, Jeongwoo

    2014-05-01

    In this work, the delay time for groundwater recharge was estimated by comparing simulated groundwater recharge by means of SWAT(Soil and Water Assessment Tool) model and WTF(Water Table Fluctuation) method. SWAT model uses the delay time for groundwater recharge when the water from rainfall travelled through vadose zone just after getting out of soil zone bottom. Since measuring delay time is almost impossible, we had to choose the method of comparing the estimated values from modeling(SWAT) and analytic method(WTF). The test site is Hancheon watershed which has 8 groundwater measurement stations. The results show that the altitude has a linear relationship with the estimated delay time values. To validate these results, we conducted corelation analysis between transformed groundwater levels and observed ones. The results showed that computed groundwater levels have good correlation. The estimated delay time would be used for the groundwater behaviour characteristics in vadose zone. keywords: Water Table Fluctuation, vadose zone, groundwater recharge, Soil and Water Assessment Tool Acknowledgements This research was supported by the Regional Innovative Technology Project 2B from KICTTEP.

  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. 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

  16. Seasonal changes in submarine groundwater discharge to coastal salt ponds estimated using 226Ra and 228Ra as tracers

    USGS Publications Warehouse

    Hougham, A.L.; Moran, S.B.; Masterson, J.P.; Kelly, R.P.

    2008-01-01

    Submarine groundwater discharge (SGD) to coastal southern Rhode Island was estimated from measurements of the naturally-occurring radioisotopes 226Ra (t1/2 = 1600??y) and 228Ra (t1/2 = 5.75??y). Surface water and porewater samples were collected quarterly in Winnapaug, Quonochontaug, Ninigret, Green Hill, and Pt. Judith-Potter Ponds, as well as nearly monthly in the surface water of Rhode Island Sound, from January 2002 to August 2003; additional porewater samples were collected in August 2005. Surface water activities ranged from 12-83??dpm 100??L- 1 (60??dpm = 1??Bq) and 21-256??dpm 100??L- 1 for 226Ra and 228Ra, respectively. Porewater 226Ra activities ranged from 16-736??dpm 100??L- 1 (2002-2003) and 95-815??dpm 100??L- 1 (2005), while porewater 228Ra activities ranged from 23-1265??dpm 100??L- 1. Combining these data with a simple box model provided average 226Ra-based submarine groundwater fluxes ranging from 11-159??L m- 2 d- 1 and average 228Ra-derived fluxes of 15-259??L m- 2 d- 1. Seasonal changes in Ra-derived SGD were apparent in all ponds as well as between ponds, with SGD values of 30-472??L m- 2 d- 1 (Winnapaug Pond), 6-20??L m- 2 d- 1 (Quonochontaug Pond), 36-273??L m- 2 d- 1 (Ninigret Pond), 29-76??L m- 2 d- 1 (Green Hill Pond), and 19-83??L m- 2 d- 1 (Pt. Judith-Potter Pond). These Ra-derived fluxes are up to two orders of magnitude higher than results predicted by a numerical model of groundwater flow, estimates of aquifer recharge for the study period, and values published in previous Ra-based SGD studies in Rhode Island. This disparity may result from differences in the type of flow (recirculated seawater versus fresh groundwater) determined using each technique, as well as variability in porewater Ra activity. ?? 2007 Elsevier B.V. All rights reserved.

  17. Definition of boundary and initial conditions in the analysis of saturated ground-water flow systems; an introduction

    USGS Publications Warehouse

    Franke, O.L.; Reilly, T.E.; Bennett, G.D.

    1984-01-01

    Accurate definition of boundary and initial conditions is an essential part of conceptualizing and modeling ground-water flow systems. This report explains the properties of the seven most common boundary conditions encountered in ground-water systems and discusses major aspects of their application. It also discusses the significance and specification of initial conditions and evaluates some common errors in applying this concept to ground-water system models. (USGS)

  18. Ground-water monitoring at Santa Barbara, California; Phase 3, development of a three-dimensional digital ground-water flow model for storage unit I of the Santa Barbara ground-water basin

    USGS Publications Warehouse

    Martin, Peter; Berenbrock, Charles

    1986-01-01

    Water-bearing rocks within the 7 sq mi of Storage Unit I of the Santa Barbara Groundwater Basin, consist of unconsolidated deposits that range in thickness from < 300 ft along the north perimeter of the unit to > 1,000 ft near the Pacific Ocean. The groundwater system was simulated as two horizontal layers separated by a confining bed. The model boundaries coincide with mapped faults on all sides. The faults were considered no-flow boundaries except for the offshore fault that forms the south boundary. This boundary was simulated as a general-head boundary , which allows water to move into and out of the modeled area. The model was calibrated by simulating both steady-state conditions (approximated by July 1978 and February 1983 water levels) and transient-state conditions (represented by May 1978 through December 1979 water level changes). The calibrated model was then used to simulate the period from January 1980 through December 1983 in order to verify the model. Model results generally closely matched measured data throughout Storage Unit I. During the transient and verification simulations, 9,980 acre-ft of groundwater was pumped from Storage Unit I for municipal use. Results of the model indicate that 42% (4,190 acre-ft) of the water pumped from the system was withdrawn from storage, 33% (3,290 acre-ft) was derived from changes in underflow across the offshore fault, and 25% (2,500 acre-ft) was derived from decreased groundwater discharge to drains. The model simulated that municipal pumpage induced about 1,380 acre-ft of water to move across the offshore fault toward Storage Unit I. Several model simulations were used to estimate aquifer response to different municipal pumpage patterns that could be used as management alternatives. Results of the simulations indicate that spreading municipal pumpage more evenly throughout Storage Unit I, by increasing the number of wells while reducing the pumping rate at the individual wells to maintain the same total pumpage, significantly reduces the inflow of groundwater across the offshore fault. (Author 's abstract)

  19. Fluid flow and the state of stress at Mt. Hood, Oregon, inferred from microseismicity induced by groundwater recharge

    NASA Astrophysics Data System (ADS)

    Saar, M.; Manga, M.

    2003-04-01

    Pore pressure diffusion related time delays between seasonal groundwater recharge and seismicity can be used to estimate large-scale hydraulic diffusivities. Groundwater recharge rates in Volcanic Arcs such as the Oregon Cascades can be large. Here, the annual precipitation rate is about 2 m of which over 50 % infiltrates the ground mostly during snowmelt in spring. Therefore, infiltration rates of > 1 m per year can occur. Due to near-surface porosities of 5 to 10 % groundwater levels may fluctuate annually by 10 to 20 m resulting in pore fluid pressure variations of 1-2 × 10^5 Pa and more. We approximate the seasonal variations in groundwater recharge with discharge in runoff-dominated streams that show a peak discharge during snow melt in spring. Time series of daily number of earthquakes and seismic moment as well as stream discharge are interpolated by applying piecewise polynomial fits. Thus, the series can be cross correlated at equivalent frequency bands. Piecewise overlapping cross correlation coefficients are determined between stream discharge and both number of earthquakes and seismic moment. We find statistically significant correlation coefficients at a time lag of about 150 days. This time lag and a mean earthquake depth of 4.5 km are used in the solution to the pressure diffusion equation, under periodic (1 year) boundary conditions, to estimate the hydraulic diffusivity (0.3 m^2/s). Assuming a reasonable specific storage of about 5.5 × 10-6 1/m implies a hydraulic conductivity of approximately 2 × 10-6 m/s. The latter value is comparable with our results from coupled heat and groundwater flow studies that are based on bore hole temperature data at Mt. Hood. Moreover, the periodic boundary condition allows us to determine a critical fraction, P/P_0, of the applied zero-depth pore fluid pressure, P_0, that has to be reached to cause seismicity at the given mean earthquake depth (4.5 km). Here, P/P_0 ? 0.24 so that for the estimated 0.1 <= P_0 <= 0.2 MPa the critical pressure to cause hydroseismicity is approximately 0.02 <= P <= 0.05 MPa. The low value in P suggests that the state of stress in the crust near Mt. Hood is near critical for failure.

  20. Glaciation and regional ground-water flow in the Fennoscandian Shield: Site 94

    USGS Publications Warehouse

    Provost, Alden M.; Voss, Clifford I.; Neuzil, C.E.

    1998-01-01

    Results from a regional-scale ground-water flow model of the Fennoscandian shield suggest that ground-water flow is strongly affected by surface conditions associated with climatic change and glaciation. The model was used to run a series of numerical simulations of variable-density ground-water flow in a 1500-km-long and approximately 10-km-deep cross-section that passes through southern Sweden. Ground-water flow and shield brine transport in the cross-sectional model are controlled by an assumed time evolution of surface conditions over the next 140 ka. Simulations show that, under periglacial conditions, permafrost may locally or extensively impede the free recharge or discharge of ground water. Below cold-based glacial ice, no recharge or discharge of ground water occurs. Both of these conditions result in the settling of shield brine and consequent freshening of near-surface water in areas of natural discharge blocked by permafrost. The presence of warm-based ice with basal melting creates a potential for ground-water recharge rates much larger than under present, ice-free conditions. Recharging basal meltwater can reach depths of a few kilometers in a few thousand years. The vast majority of recharged water is accommodated through storage in the volume of bedrock below the local area of recharge; regional (lateral) redistribution of recharged water by subsurface flow is minor over the duration of a glacial advance (~10 ka). During glacial retreat, the weight of the ice overlying a given surface location decreases, and significant upward flow of ground water may occur below the ice sheet due to pressure release, despite the continued potential for recharge of basal meltwater. Excess meltwater must exit from below the glacier through subglacial cavities and channels. Subsurface penetration of meltwater during glacial advance and up-flow during glacial retreat are greatest if the loading efficiency of the shield rock is low. The maximum rate of ground-water discharge occurs at the receding ice margin, and some discharge occurs below incursive post-glacial seas. The simulation results suggest that vertical movement of deep shield brines induced by the next few glacial cycles should not increase the concentration of dissolved solids significantly above present-day levels. However, the concentration of dissolved solids should decrease significantly at depths of up to several kilometers during periods of glacial meltwater recharge. The meltwater may reside in the subsurface for periods exceeding 10 ka and may bring oxygenated conditions to an otherwise reducing chemical environment.

  1. Dual States Estimation of a Subsurface Flow-Transport Coupled Model using Ensemble Kalman Filtering

    NASA Astrophysics Data System (ADS)

    El Gharamti, Mohamad; Valstar, Johan; Hoteit, Ibrahim

    2014-05-01

    Modeling the spread of subsurface contaminants requires coupling a groundwater flow model with a contaminant transport model. Such coupling may provide accurate estimates of future subsurface hydrologic states if essential flow and contaminant data are assimilated in the model. Assuming perfect flow, an ensemble Kalman filter (EnKF) can be used for direct data assimilation into the transport model. This is, however, a crude assumption as flow models can be subject to many sources of uncertainty. If the flow is not accurately simulated, contaminant predictions will likely be inaccurate even after successive Kalman updates of the contaminant model with the data. The problem is better handled when both flow and contaminant states are concurrently estimated using the traditional joint state augmentation approach. In this study, we introduce a dual estimation strategy for data assimilation into a one-way coupled system by treating the flow and the contaminant models separately while intertwining a pair of distinct EnKFs, one for each model. The presented strategy only deals with the estimation of state variables but it can also be used for state and parameter estimation problems. This EnKF-based dual state-state estimation procedure presents a number of novel features: (i) it allows for simultaneous estimation of both flow and contaminant states in parallel; (ii) it provides a time consistent sequential updating scheme between the two models (first flow, then transport); (iii) it simplifies the implementation of the filtering system; and (iv) it yields more stable and accurate solutions than does the standard joint approach. We conduct synthetic experiments based on various time stepping and observation strategies to evaluate the dual EnKF approach and compare its performance with the joint state augmentation approach. Experimental results show that on average, the dual strategy could reduce the estimation error of the coupled states by 15% compared with the joint approach. Furthermore, the dual estimation is proven to be very effective computationally, recovering accurate estimates at a reasonable cost.

  2. A hydrogeological conceptual approach to study urban groundwater flow in Bucharest city, Romania

    NASA Astrophysics Data System (ADS)

    Boukhemacha, Mohamed Amine; Gogu, Constantin Radu; Serpescu, Irina; Gaitanaru, Dragos; Bica, Ioan

    2015-05-01

    Management of groundwater systems in urban areas is necessary and can be reliably performed by means of mathematical modeling combined with geospatial analysis. A conceptual approach for the study of urban hydrogeological systems is presented. The proposed approach is based on the features of Bucharest city (Romania) and can be adapted to other urban areas showing similar characteristics. It takes into account the interaction between groundwater and significant urban infrastructure elements that can be encountered in modern cities such as subway tunnels and water-supply networks, and gives special attention to the sewer system. In this respect, an adaptation of the leakage factor approach is proposed, which uses a sewer-system zoning function related to the conduits' location in the aquifer system and a sewer-conduits classification function related to their structural and/or hydraulic properties. The approach was used to elaborate a single-layered steady state groundwater flow model for a pilot zone of Bucharest city.

  3. Evaluation of methods for estimating ground-water withdrawals in western Kansas

    USGS Publications Warehouse

    Baker, Claud H., Jr.

    1979-01-01

    Individual users report ground-water withdrawals annually to the Kansas State Board of Agriculture. It is estimated that these values are 10 to 15 percent higher than actual values because most users do not possess the means for accurately determining discharge rates. Methods of estimating ground-water use in western Kansas that appear to offer the desired accuracy include (1) extrapolation from a sample of metered withdrawals, (2) calculation from precipitation and irrigated acreages of various crop types, and (3) calculation from a sample of power-coefficients. All three methods are being tested and compared with actual measured values. Newly developed electronic running-time and discharge-totaling meters are being tested that may give accurate values of total pumping time and discharge at small cost. (Kosco-USGS)

  4. Estimating Regional Groundwater Variability in Oklahoma from a Combination of in situ and Remotely Sensed Observations

    NASA Astrophysics Data System (ADS)

    Swenson, S. C.; Basara, J.; Wahr, J.; Famiglietti, J.

    2006-12-01

    Monthly gravity fields provided by the Gravity Recovery and Climate Experiment (GRACE) can be used to estimate changes in the vertically integrated water content for large regions. Using a recently developed filtering technique, we have shown good agreement between total water storage estimates obtained from GRACE and from in situ measurements in Illinois, demonstrating that GRACE can resolve the seasonal cycle of total water storage for areas as small as 200,000 km2. Another location having soil moisture measurements comparable to the spatial resolution of GRACE is the Oklahoma Mesonet, an automated observing network that provides realtime hydrometeorological observations at more than 100 stations in Oklahoma, spanning an area of roughly 180,000 km2. Beginning in the mid-1990's, soil moisture sensors at depths of 5 to 75 cm were installed at many of these sites. In this study, we use these measurements to estimate changes in storage in the unsaturated zone. By removing these soil moisture estimates from remotely sensed estimates of changes in total water storage obtained from GRACE, we can estimate changes in regional groundwater storage at the monthly to seasonal timescale. Here we present our estimates of the seasonal cycle of groundwater for Oklahoma, and discuss possible sources of disagreement.

  5. 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 gradient and a head value at a single point (as time series). A case study is included to demonstrate the application of the model in local modeling of the groundwater flow. Transient three-dimensional capture zones are delineated for a site on Prairie Island, MN. Prairie Island is located on the Mississippi River 40 miles south of the Twin Cities metropolitan area. The case study focuses on a well that has been known to contain viral DNA. The objective of the study was to assess the potential for pathogen migration toward the well.

  6. Development of one-dimensional computational fluid dynamics code 'GFLOW' for groundwater flow and contaminant transport analysis

    SciTech Connect

    Rahatgaonkar, P. S.; Datta, D.; Malhotra, P. K.; Ghadge, S. G. [Nuclear Power Corporation of India Ltd., R-2, Ent. Block, Nabhikiya Urja Bhavan, Anushakti Nagar, Mumbai - 400 094 (India)

    2012-07-01

    Prediction of groundwater movement and contaminant transport in soil is an important problem in many branches of science and engineering. This includes groundwater hydrology, environmental engineering, soil science, agricultural engineering and also nuclear engineering. Specifically, in nuclear engineering it is applicable in the design of spent fuel storage pools and waste management sites in the nuclear power plants. Ground water modeling involves the simulation of flow and contaminant transport by groundwater flow. In the context of contaminated soil and groundwater system, numerical simulations are typically used to demonstrate compliance with regulatory standard. A one-dimensional Computational Fluid Dynamics code GFLOW had been developed based on the Finite Difference Method for simulating groundwater flow and contaminant transport through saturated and unsaturated soil. The code is validated with the analytical model and the benchmarking cases available in the literature. (authors)

  7. Upper washita river experimental watersheds: reservoir, groundwater, and stream flow data.

    PubMed

    Moriasi, Daniel N; Starks, Patrick J; Guzman, Jorge A; Garbrecht, Jurgen D; Steiner, Jean L; Stoner, J Chris; Allen, Paul B; Naney, James W

    2014-07-01

    Surface and groundwater quantity and quality data are essential in many hydrologic applications and to the development of hydrologic and water quality simulation models. We describe the hydrologic data available in the Little Washita River Experimental Watershed (LWREW) of the Southern Great Plains Research Watershed (SGPRW) and Fort Cobb Reservoir Experimental Watershed (FCREW), both located in southwest Oklahoma. Specifically, we describe the flood retarding structures and corresponding stage, discharge, seepage, and consumptive use data (), stream gauges, and groundwater wells and their corresponding stream flow (; LWREW ARS 522-526 stream gauges) and groundwater level data (SGPRW groundwater levels data; LWREW groundwater data; ; ), respectively. Data collection is a collaborative effort between federal and state agencies. Stage, discharge, seepage, and consumptive use data for the Fort Cobb Reservoir are available from the Bureau of Reclamation and cover a period of 1959 to present. There are 15 stream gauges in the LWREW and six in the FCREW with varying data records. There were 479 observation wells with data in the SGPRW and 80 in the LWREW, with the latest records collected in 1992. In addition, groundwater level data are available from five real-time monitoring wells and 34 historical wells within the FCREW. These data sets have been used for several research applications. Plans for detailed groundwater data collection are underway to calibrate and validate the linked Soil and Water Assessment Tool (SWAT)-MODFLOW model. Also, plans are underway to conduct reservoir bathymetric surveys to determine the current reservoir capacity as affected by land use/land cover and overland and stream channel soil erosion. PMID:25603074

  8. A General Solution for Groundwater Flow in Estuarine Leaky Aquifer System with Considering Aquifer Anisotropy

    NASA Astrophysics Data System (ADS)

    Chen, Po-Chia; Chuang, Mo-Hsiung; Tan, Yih-Chi

    2014-05-01

    In recent years the urban and industrial developments near the coastal area are rapid and therefore the associated population grows dramatically. More and more water demand for human activities, agriculture irrigation, and aquaculture relies on heavy pumping in coastal area. The decline of groundwater table may result in the problems of seawater intrusion and/or land subsidence. Since the 1950s, numerous studies focused on the effect of tidal fluctuation on the groundwater flow in the coastal area. Many studies concentrated on the developments of one-dimensional (1D) and two-dimensional (2D) analytical solutions describing the tide-induced head fluctuations. For example, Jacob (1950) derived an analytical solution of 1D groundwater flow in a confined aquifer with a boundary condition subject to sinusoidal oscillation. Jiao and Tang (1999) derived a 1D analytical solution of a leaky confined aquifer by considered a constant groundwater head in the overlying unconfined aquifer. Jeng et al. (2002) studied the tidal propagation in a coupled unconfined and confined costal aquifer system. Sun (1997) presented a 2D solution for groundwater response to tidal loading in an estuary. Tang and Jiao (2001) derived a 2D analytical solution in a leaky confined aquifer system near open tidal water. This study aims at developing a general analytical solution describing the head fluctuations in a 2D estuarine aquifer system consisted of an unconfined aquifer, a confined aquifer, and an aquitard between them. Both the confined and unconfined aquifers are considered to be anisotropic. The predicted head fluctuations from this solution will compare with the simulation results from the MODFLOW program. In addition, the solutions mentioned above will be shown to be special cases of the present solution. Some hypothetical cases regarding the head fluctuation in costal aquifers will be made to investigate the dynamic effects of water table fluctuation, hydrogeological conditions, and characteristics of soil on the groundwater level fluctuations in the 2D estuarine leaky aquifer system.

  9. Parameter Estimation Approach in Groundwater Hydrology Using Hybrid Ant Colony System

    Microsoft Academic Search

    Shouju Li; Yingxi Liu; He Yu

    2006-01-01

    \\u000a A new approach to parameter estimation in groundwater hydrology is developed using hybrid ant colony system with simulated\\u000a annealing. Based on the information from the observed water heads and calculated water heads, an objective function for inverse\\u000a problem is proposed. The inverse problem of parameter identification is formulated as an optimization problem. Simulated annealing\\u000a has the ability of probabilistic hill-climbing

  10. Estimation of submarine groundwater discharge in Plover Cove, Tolo Harbour, Hong Kong by 222Rn

    Microsoft Academic Search

    Kiu Chung Tse; Jiu Jimmy Jiao

    2008-01-01

    Algal blooms in Tolo Harbour, Hong Kong have received much attention and submarine groundwater discharge is speculated to be a significant pathway carrying nutrients into the constricted estuary. Plover Cove, a small cove in the Harbour, was selected for SGD analysis using 222Rn budget. The volumetric SGD rates are estimated to be about 8000 m3\\/day for neap tide and about 17,000 m3\\/day

  11. Groundwater recharge estimation and regionalization: the Great Bend Prairie of central Kansas and its recharge statistics

    Microsoft Academic Search

    Marios Sophocleous

    1992-01-01

    Sophocleous, M., 1992. Groundwater recharge estimation and regionalization: the Great Bend Prairie of central Kansas and its recharge statistics. J. Hydrol., 137: 113-140. The results of a 6 year recharge st,dy in the Great Bend Prairie of t:entral Kansas are statistically analyzed to regionalize the limited number of site-specific but year-round measurements. Emphasis is placed on easily measured parameters and

  12. Estimated probability of arsenic in groundwater from bedrock aquifers in New Hampshire, 2011

    USGS Publications Warehouse

    Ayotte, Joseph D.; Cahillane, Matthew; Hayes, Laura; Robinson, Keith W.

    2012-01-01

    Probabilities of arsenic occurrence in groundwater from bedrock aquifers at concentrations of 1, 5, and 10 micrograms per liter (µg/L) were estimated during 2011 using multivariate logistic regression. These estimates were developed for use by the New Hampshire Environmental Public Health Tracking Program. About 39 percent of New Hampshire bedrock groundwater was identified as having at least a 50 percent chance of containing an arsenic concentration greater than or equal to 1 µg/L. This compares to about 7 percent of New Hampshire bedrock groundwater having at least a 50 percent chance of containing an arsenic concentration equaling or exceeding 5 µg/L and about 5 percent of the State having at least a 50 percent chance for its bedrock groundwater to contain concentrations at or above 10 µg/L. The southeastern counties of Merrimack, Strafford, Hillsborough, and Rockingham have the greatest potential for having arsenic concentrations above 5 and 10 µg/L in bedrock groundwater. Significant predictors of arsenic in groundwater from bedrock aquifers for all three thresholds analyzed included geologic, geochemical, land use, hydrologic, topographic, and demographic factors. Among the three thresholds evaluated, there were some differences in explanatory variables, but many variables were the same. More than 250 individual predictor variables were assembled for this study and tested as potential predictor variables for the models. More than 1,700 individual measurements of arsenic concentration from a combination of public and private water-supply wells served as the dependent (or predicted) variable in the models. The statewide maps generated by the probability models are not designed to predict arsenic concentration in any single well, but they are expected to provide useful information in areas of the State that currently contain little to no data on arsenic concentration. They also may aid in resource decision making, in determining potential risk for private wells, and in ecological-level analysis of disease outcomes. The approach for modeling arsenic in groundwater could also be applied to other environmental contaminants that have potential implications for human health, such as uranium, radon, fluoride, manganese, volatile organic compounds, nitrate, and bacteria.

  13. Adaptive mixed norm optical flow estimation

    NASA Astrophysics Data System (ADS)

    Estrela, Vania V.; Franz, Matthias O.; Lopes, Ricardo T.; De Araújo, A. P.

    2005-07-01

    The pel-recursive computation of 2-D optical flow has been extensively studied in computer vision to estimate motion from image sequences, but it still raises a wealth of issues, such as the treatment of outliers, motion discontinuities and occlusion. It relies on spatio-temporal brightness variations due to motion. Our proposed adaptive regularized approach deals with these issues within a common framework. It relies on the use of a data-driven technique called Mixed Norm (MN) to estimate the best motion vector for a given pixel. In our model, various types of noise can be handled, representing different sources of error. The motion vector estimation takes into consideration local image properties and it results from the minimization of a mixed norm functional with a regularization parameter depending on the kurtosis. This parameter determines the relative importance of the fourth norm and makes the functional convex. The main advantage of the developed procedure is that no knowledge of the noise distribution is necessary. Experiments indicate that this approach provides robust estimates of the optical flow.

  14. Study of environmental isotope distribution in the Aswan High Dam Lake (Egypt) for estimation of evaporation of lake water and its recharge to adjacent groundwater.

    PubMed

    Aly, A I; Froehlich, K; Nada, A; Awad, M; Hamza, M; Salem, W M

    1993-03-01

    Oxygen-18 ((18)0) and deuterium isotopes were used to estimate the evaporation from the Aswan High Dam Lake and to investigate the inter-relation between the lake water and adjacent groundwater.According to stable isotopic analysis of samples taken in 1988 and 1989, the lake can be divided into two sections. In the first section extending between Abu Simbel and a point between EI-Alaki and Krosko, a remarkable vertical gradient of (18)0 and deuterium isotopic composition was observed. The second northern sector extending to the High Dam is characterised by a lower vertical isotopic gradient. In this sector in general, higher values of (18)O and deuterium contents were found at the top and lower values at the bottom. Also a strong horizontal increase of the heavy isotope content was observed. Thus, in the northern section evaporation is of dominating influence on the isotopic composition of the lake water.With the help of an evaporation pan experiment it was possible to calibrate the evaporative isotope enrichment in the lake and to facilitate a preliminary estimate of evaporative losses of lake water. The evaporation from the lake was estimated to be about 19% of the input water flow rate.The groundwater around the lake was investigated and samples from production wells and piezometers were subjected to isotopic analysis. The results indicate that recent recharge to the groundwater aquifer is limited to wells near to the lake and up to a maximum distance of about 10 km. The contribution of recent Nile water to the groundwater in these wells was estimated to range between 23 and 70%. Beyond this distance, palaeowater was observed with highly depleted deuterium and (18)0 contents, which was also confirmed by 14c dating. The age of palaeo groundwater in this area can reach values of more than 26,000 years.Recommendations are given for efficient water management of the lake water. PMID:24198080

  15. MODFLOW-based coupled surface water routing and groundwater-flow simulation

    USGS Publications Warehouse

    Hughes, Joseph D.; Langevin, Christian D.; White, Jeremy T.

    2015-01-01

    In this paper, we present a flexible approach for simulating one- and two-dimensional routing of surface water using a numerical surface water routing (SWR) code implicitly coupled to the groundwater-flow process in MODFLOW. Surface water routing in SWR can be simulated using a diffusive-wave approximation of the Saint-Venant equations and/or a simplified level-pool approach. SWR can account for surface water flow controlled by backwater conditions caused by small water-surface gradients or surface water control structures. A number of typical surface water control structures, such as culverts, weirs, and gates, can be represented, and it is possible to implement operational rules to manage surface water stages and streamflow. The nonlinear system of surface water flow equations formulated in SWR is solved by using Newton methods and direct or iterative solvers. SWR was tested by simulating the (1) Lal axisymmetric overland flow, (2) V-catchment, and (3) modified Pinder-Sauer problems. Simulated results for these problems compare well with other published results and indicate that SWR provides accurate results for surface water-only and coupled surface water/groundwater problems. Results for an application of SWR and MODFLOW to the Snapper Creek area of Miami-Dade County, Florida, USA are also presented and demonstrate the value of coupled surface water and groundwater simulation in managed, low-relief coastal settings.

  16. Uncertainty analysis of a groundwater flow model in east-central Florida

    USGS Publications Warehouse

    Sepulveda, Nicasio; Doherty, John E.

    2014-01-01

    A groundwater flow model for east-central Florida has been developed to help water-resource managers assess the impact of increased groundwater withdrawals from the Floridan aquifer system on heads and spring flows originating from the Upper Floridan aquifer. The model provides a probabilistic description of predictions of interest to water-resource managers, given the uncertainty associated with system heterogeneity, the large number of input parameters, and a nonunique groundwater flow solution. The uncertainty associated with these predictions can then be considered in decisions with which the model has been designed to assist. The “Null Space Monte Carlo” method is a stochastic probabilistic approach used to generate a suite of several hundred parameter field realizations, each maintaining the model in a calibrated state, and each considered to be hydrogeologically plausible. The results presented herein indicate that the model’s capacity to predict changes in heads or spring flows that originate from increased groundwater withdrawals is considerably greater than its capacity to predict the absolute magnitudes of heads or spring flows. Furthermore, the capacity of the model to make predictions that are similar in location and in type to those in the calibration dataset exceeds its capacity to make predictions of different types at different locations. The quantification of these outcomes allows defensible use of the modeling process in support of future water-resources decisions. The model allows the decision-making process to recognize the uncertainties, and the spatial/temporal variability of uncertainties that are associated with predictions of future system behavior in a complex hydrogeological context.

  17. Estimating Preferential Flow in Karstic Aquifers Using Statistical Mixed Models

    PubMed Central

    Anaya, Angel A.; Padilla, Ingrid; Macchiavelli, Raul; Vesper, Dorothy J.; Meeker, John D.; Alshawabkeh, Akram N.

    2013-01-01

    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 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 statistical mixed models used in the study. PMID:23802921

  18. 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

  19. Groundwater Lab

    NSDL National Science Digital Library

    Kim Hannula

    Students use analog models to explore the behavior of groundwater. Students calculate porosity of analog materials (cups of marbles and beads), and then observe groundwater flow using food coloring as a dye tracer. They explore the effects of pumping wells and contaminating groundwater through a leaky landfill. One portion of the model allows students to observe the behavior of an artesian aquifer.

  20. Groundwater and surface water interaction in flow-through gravel pit lakes.

    NASA Astrophysics Data System (ADS)

    Nella Mollema, Pauline; Antonellini, Marco

    2015-04-01

    Gravel pits are excavated in aquifers to fulfill the need for construction materials. Flow-through lakes form when the gravel pits are below the water table and fill with groundwater. In certain areas there are more than 60 of these lakes close together and their presence changes the drainage patterns and water- and hydrochemical budgets of a watershed. In flow-through gravel pit lakes, groundwater mixes with surface water and interacts with the atmosphere; outflow occurs only via groundwater. The lifespan of gravel pit lakes may be up to thousands of years as their depth to surface ratio is typically large and sedimentation rates are low. We have studied two gravel pit lake systems, a fluvial freshwater system in the Netherlands and a coastal brackish lake system in Italy. One Dutch gravel pit lake studied in detail is in part artificially replenished with Meuse River water for drinking water production that occurs downstream of the lake by water pumps. The Italian gravel pit lakes are fed by brackish groundwater that is a mix of freshwater from precipitation, Apennine Rivers and brackish (Holocene) Adriatic Sea water. Here, the drainage system of the low lying land enhances groundwater flow into the lake. Surface water evaporation is larger in temperate and Mediterranean climates than the actual evapotranspiration of pre-existing grassland and forests. The lakes, therefore, cause a loss of freshwater. The creation of water surfaces allows algae and other flora and fauna to develop. In general, water becomes gradually enriched in certain chemical constituents on its way through the hydrological cycle, especially as groundwater due to water-rock interactions. When groundwater ex-filtrates into gravel pit lakes, the natural flow of solutes towards the sea is interrupted. Hydrochemical analysis of ground- and surface waters, as well as chemical analysis of lake bottom sediments and stable H and O isotope data, show that gravel pit lake water is characterized (among others) by a higher pH, O2 and alkalinity and lower dissolved metal and certain trace concentrations than natural lakes and groundwater. In both settings, groundwater rich in dissolved elements (e.g. Al, As, Fe, Mn, Ni and PO43) flows into the gravel pit lakes where the pH and DO are high, which enhances the (co)precipitation of Fe, Mn and Al oxides that include trace elements. Metal concentrations in the Dutch lake's bottom sediments have increased over a 10 year period. Redox reactions caused by water table lowering and farmland fertilization upstream from the lake explain the metals mobilization and subsequent transport with groundwater towards the lakes. The gravel pit lakes, especially if there are many close together, influence so the cycle of water metals, nutrients as well as other trace elements of a watershed by incorporating them into biomass and bottom sediments or creating an environment where they can remain in concentrated solution.

  1. A simple Bayesian method to combine lithofacies data with drawdown measurements when calibrating a groundwater flow model

    NASA Astrophysics Data System (ADS)

    Komatsu, M.; Frippiat, C. C.; Sakaki, T.; Illangasekare, T. H.

    2009-12-01

    The combination of multiple types of data into model development and calibration has been receiving substantial attention by researchers, as it can sometimes allow a significant reduction in uncertainty of model predictions. In subsurface hydrology, drawdown data collected during pumping tests can be combined with other types of data, such as information on the vertical distribution of lithofacies gained when drilling boreholes or when using direct push techniques. In this study, we developed a simple Bayesian method to estimate heterogeneous distributions of soil hydraulic conductivity using both lithofacies data and observations associated with flow. The method is based on Markov chains models of transition probabilities to create three-dimensional random realizations of spatial distributions of lithofacies from lithofacies data. For each random realization, the hydraulic conductivity (K) of each lithofacies is estimated from pumping test data by inversion of a groundwater flow data. The minimum value of the objective function after application of the inversion code is used as a proxy for the likelihood of head measurements and is exploited within an accept-reject Metropolis-Hastings algorithm. Application of this algorithm allows one to determine whether the random K field created from the random realization of lithofacies under consideration and the corresponding estimated K values must be rejected or can be accepted as an estimation of the true K field. Application of the algorithm to a large number of random realizations permits the construction of a probability distribution of K fields conditioned both to lithofacies data and to drawdown data. In a Bayesian framework, the best estimate of the K field corresponds to the peak of this conditional probability distribution. The method was applied to back-estimate the spatial distribution of hydraulic conductivity of a laboratory-scale heterogeneous 3-D synthetic aquifer created in an intermediate scale test tank. The aquifer consisted of five lithofacies, corresponding to five test sands, arranged in a random pattern. Different quantities of synthetic lithofacies data under the form of fictitious borehole logs was generated from the known distribution of the five sands in the synthetic aquifer. Drawdown data were generated in three pumping tests and used to identify five K values. The pumping tests were also simulated numerically in order to provide a series of error-free synthetic hydraulic data sets. The results generally showed that the use of more lithofacies data in the construction of the lithofacies realizations led to an improvement in groundwater flow model prediction accuracy, with a convergence of the estimated K field towards the true K distribution.

  2. The hydraulic conductivity field and groundwater flow in the unconfined aquifer system of the Keta Strip, Ghana

    NASA Astrophysics Data System (ADS)

    Yidana, Sandow Mark; Chegbeleh, Larry Pax

    2013-10-01

    This study investigates the hydraulic conductivity field and the groundwater flow pattern as predicted by a calibrated steady state groundwater flow model for the Keta Strip, southeastern Ghana. The hydraulic conductivity field is an important parameter in evaluating aquifer properties in space, and in general basin-wide groundwater resources evaluation and management. This study finds that the general hydraulic conductivity of the unconsolidated unconfined aquifer system of the Keta Strip ranges between 2 m/d and 20 m/d, with an average of 15 m/d. The spatial variation in horizontal hydraulic conductivity appears to take the trend in the variations in the nature of the material in space. Calibrated groundwater recharge suggests that 6.9-34% of annual precipitation recharges the shallow aquifer system. This amount of recharge is significant and suggests high fortunes in terms of groundwater resources development for agriculture and industrial activities in the area. A spatial distribution of groundwater recharge from precipitation is presented in this study. The spatial pattern appears to take the form of the distribution in horizontal hydraulic conductivity, and suggests that the vertical hydraulic conductivity takes the same pattern of spatial variation as the horizontal hydraulic conductivity. This is consistent with observations in other areas. The resulting groundwater flow is dominated by local flow systems as the unconfined system is quite shallow. A general northeast - southwest flow pattern has been observed in the study area.

  3. Impacts of future changes on groundwater recharge and flow in highly-connected river-aquifer systems: A case study of the Spokane Valley-Rathdrum Prairie Aquifer

    NASA Astrophysics Data System (ADS)

    Nguyen, T. T.; Baxter, H.; Barber, M. E.; Hossain, A.; Orr, C. H.; Adam, J. C.

    2013-12-01

    The Spokane, Washington-Coeur d'Alene, Idaho Corridor is well-known for its Spokane Valley-Rathdrum Prairie (SVRP) Aquifer which is a sole source of drinking water for more than 500,000 people. The aquifer is highly connected to the Spokane River and responds very fast to natural and human perturbations, making it relatively vulnerable to climate and anthropogenic changes in future decades. Recent studies have indicated a decline in minimum daily flow in the Spokane River in the last 100 years, while projecting an increase in cool-season precipitation into the future. We investigated the potential impacts of these projected future climate-driven hydrologic changes on groundwater recharge and flow in the SVRP. A distributed, physically-based hydrological model, the Precipitation Runoff Modeling System (PRMS), was coupled with an existing Modular three-dimensional finite-difference ground-water model (MODFLOW) to have better estimates of recharge into the SVRP as well as the interaction of surface water and groundwater. The couple model was calibrated and validated at a daily time-step within the Model-Independent Parameter Estimation (PEST) framework using 16 years of both observed streamflow and observed well data (1990 - 2005). To assess future climate change impacts, statistically downscaled climate projections of temperature and precipitation between 2010 and 2050 from four general circulation models were used. The results from the coupled model provide insight on the interplay between snowmelt, streamflow, groundwater recharge and discharge in such a highly-connected system. Moreover, the relative sensitivities of groundwater recharge and flow with respect to changes in climate and land cover are also examined. These results can be used as good references for long term water resources management and planning in the region.

  4. Estimated Ground-Water Use in Becker, Clay, Douglas, Grant, Otter Tail, and Wilkin Counties, Minnesota, for 2030 and 2050

    USGS Publications Warehouse

    Winterstein, Thomas A.

    2007-01-01

    The U.S. Department of the Interior, Bureau of Reclamation, is studying six alternatives for delivering water to the Red River of the North Valley in North Dakota and to the cities of Breckenridge, Moorhead, and East Grand Forks, Minnesota. In order to evaluate these alternatives the Bureau of Reclamation needs estimates of ground-water use for 2030 and 2050 for six counties in Minnesota: Becker, Clay, Douglas, Grant, Otter Tail, and Wilkin Counties. The U.S. Geological Survey, in cooperation with the Bureau of Reclamation, conducted a study to estimate ground-water use in these counties for 2030 and 2050. This report (1) describes the methods used to estimate ground-water use for the years 2030 and 2050 for six Minnesota counties: Becker, Clay, Douglas, Grant, Otter Tail, and Wilkin Counties, (2) presents the estimated domestic, commercial, industrial, and irrigation ground-water use for the years 2030 and 2050 for these six counties, and (3) compares the estimated ground-water use with published estimates of recharge to three surficial aquifers: Buffalo, Otter Tail surficial, and Pelican River sand plain. Between 74 and 82 percent of the reported ground-water use in the 6 years from 2000 to 2005 was used for irrigation of major crops. The next major use of ground-water was public water supply for domestic use, between 13 and 19 percent of the reported ground-water use. Together they account for 90 to 95 percent of the appropriated ground water in the 6-year period. The total estimated 2030 ground-water use for the six counties ranges from 27,826-36,177 million gallons per year (Mgal/yr), and the total estimated 2050 ground-water use ranges from 31,313-41,746 Mgal/yr. The estimated recharge to the Buffalo aquifer, Otter Tail surficial aquifer, and Pelican River sand-plain aquifer is 3,707, 51,000, and 4,900-8,900 Mgal/yr, respectively. The range of the estimated 2050 ground-water withdrawals from the Buffalo, Otter Tail surficial, and Pelican River sand-plain aquifers is 1,234-1,776 Mgal/yr from the Buffalo aquifer, 11,728-14,820 Mgal/yr from the Otter Tail surficial aquifer, and 3,385-4,298 Mgal/yr from the Pelican River sand-plain aquifer.

  5. Global estimate of submarine groundwater discharge based on an observationally constrained radium isotope model

    NASA Astrophysics Data System (ADS)

    Kwon, Eun Young; Kim, Guebuem; Primeau, Francois; Moore, Willard S.; Cho, Hyung-Mi; DeVries, Timothy; Sarmiento, Jorge L.; Charette, Matthew A.; Cho, Yang-Ki

    2014-12-01

    Along the continental margins, rivers and submarine groundwater supply nutrients, trace elements, and radionuclides to the coastal ocean, supporting coastal ecosystems and, increasingly, causing harmful algal blooms and eutrophication. While the global magnitude of gauged riverine water discharge is well known, the magnitude of submarine groundwater discharge (SGD) is poorly constrained. Using an inverse model combined with a global compilation of 228Ra observations, we show that the SGD integrated over the Atlantic and Indo-Pacific Oceans between 60°S and 70°N is (12 ± 3) × 1013 m3 yr-1, which is 3 to 4 times greater than the freshwater fluxes into the oceans by rivers. Unlike the rivers, where more than half of the total flux is discharged into the Atlantic, about 70% of SGD flows into the Indo-Pacific Oceans. We suggest that SGD is the dominant pathway for dissolved terrestrial materials to the global ocean, and this necessitates revisions for the budgets of chemical elements including carbon.

  6. Importance of budgets for estimating the input of groundwater-derived nutrients to an eutrophic tidal river and estuary

    NASA Astrophysics Data System (ADS)

    Makings, Uriah; Santos, Isaac R.; Maher, Damien T.; Golsby-Smith, Lindsay; Eyre, Bradley D.

    2014-04-01

    Groundwater is often overlooked as a source of nutrients to estuaries and most previous groundwater-surface water exchange studies did not consider the input of dissolved organic nutrients. Here, we hypothesize that groundwater is contributing to high dissolved inorganic and organic nutrient concentrations in an eutrophic subtropical tidal river and estuary (Caboolture River, Queensland, Australia). Several spatial radon (222Rn, a natural groundwater tracer) surveys indicated that the majority of groundwater discharge occurred in the tidal river just upstream of the estuary, and that the radon hotspot did not necessarily coincide with the nutrient hotspot. A radon mass balance revealed that groundwater discharge into the tidal river was equivalent to about 50% of the gauged river flow in February 2012. Groundwater discharge apparently contributed 85% of ammonium and 35% of phosphate entering the estuary. In spite of significant correlations between radon and nitrate and dissolved organic nitrogen (DON) during spatial surveys, groundwater could account for only 7% of nitrate and 9% of DON inputs due to low groundwater concentrations and other sources (i.e., apparently a sewage treatment plant for nitrate and floodplain tributaries for DON). Because total dissolved nitrogen (TDN) was dominated by DON (69%) and nitrate (23%), the groundwater ammonium inputs were a minor source to the TDN pool within the tidal river and estuary. This study demonstrated that correlations between a groundwater tracer and nutrient concentrations do not necessarily illustrate causation. To assess how groundwater drives nutrient dynamics in estuaries, it may be important to include the tidal river (not only the estuarine salinity gradient) in field investigations, consider DON (not only ammonium and nitrate), and perform detailed budgets that include minor tributaries.

  7. Regional groundwater flow model for C, K. L. and P reactor areas, Savannah River Site, Aiken, SC

    SciTech Connect

    Flach, G.P.

    2000-02-11

    A regional groundwater flow model encompassing approximately 100 mi2 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. The model provides a quantitative understanding of groundwater flow on a regional scale within the near surface aquifers and deeper semi-confined to confined aquifers. The model incorporates historical and current field characterization data up through Spring 1999. Model preprocessing is automated so that future updates and modifications can be performed quickly and efficiently. The CKLP regional reactor model can be used to guide characterization, perform scoping analyses of contaminant transport, and serve as a common base for subsequent finer-scale transport and remedial/feasibility models for each reactor area.

  8. A scalable approach to modeling groundwater flow on massively parallel computers

    SciTech Connect

    Ashby, S.F.; Falgout, R.D.; Tompson, A.F.B.

    1995-12-01

    We describe a fully scalable approach to the simulation of groundwater flow on a hierarchy of computing platforms, ranging from workstations to massively parallel computers. Specifically, we advocate the use of scalable conceptual models in which the subsurface model is defined independently of the computational grid on which the simulation takes place. We also describe a scalable multigrid algorithm for computing the groundwater flow velocities. We axe thus able to leverage both the engineer`s time spent developing the conceptual model and the computing resources used in the numerical simulation. We have successfully employed this approach at the LLNL site, where we have run simulations ranging in size from just a few thousand spatial zones (on workstations) to more than eight million spatial zones (on the CRAY T3D)-all using the same conceptual model.

  9. Groundwater flow evaluation through backfilling materials of a surface coal mining site of Northeast Mexico

    NASA Astrophysics Data System (ADS)

    Gutierrez-Ojeda, C.; Martínez-Morales, M.; Ortíz-Flores, G.

    2013-05-01

    Surface coal mining at the Allende-Piedras Negras aquifer system requires the complete dewatering and removal of the aquifer. The aquifer contains several geologic layers of variable hydraulic conductivity. Backfilling material is composed of a mixture of permeable and impermeable layers and it was initially considered as impermeable. Exploratory drillings, pumping tests and a geophysical survey were performed in the backfilling materials and the surrounding unaltered materials in order to evaluate the natural groundwater flow modification due to the mining activities. Results of geophysical survey evidenced a saturated water table within the back filling material which was verified by exploratory drilling. Pumping tests showed that unaltered materials have a mean hydraulic conductivity of 34.5 m/day while the backfilling of 5.3 m/day. Although the mining activities reduce the hydraulic conductivity by almost an order of magnitude, it was corroborated the existence of a groundwater flow through the backfilling materials.

  10. Influence of faults on groundwater flow and transport at YuccaMountain, Nevada

    SciTech Connect

    Cohen, Andrew J.B.; Sitar, Nicholas

    1999-10-07

    Numerical simulations of groundwater flow at Yucca Mountain, Nevada are used to investigate how faults influence groundwater flow pathways and regional-scale macrodispersion. The 3-D model has a unique grid block discretization that facilitates the accurate representation of the complex geologic structure present in faulted formations. Each hydrogeologic layer is discretized into a single layer of irregular and dipping grid blocks, and faults are discretized such that they are laterally continuous and varied in displacement varies along strike. In addition, the presence of altered fault zones is explicitly modeled, as appropriate. Simulations show that upward head gradients can be readily explained by the geometry of hydrogeologic layers, the variability of layer permeabilities, and the presence of permeable fault zones or faults with displacement only, not necessarily by upwelling from a deep aquifer. Large-scale macrodispersion results from the vertical and lateral diversion of flow near the contact of high- and low-permeability layers at faults, and from upward flow within high-permeability fault zones. Conversely, large-scale channeling can occur as a result of groundwater flow into areas with minimal fault displacement. Contaminants originating at the water table can flow in a direction significantly different from that of the water table gradient, and isolated zones of contaminants can occur at the water table downgradient. By conducting both 2-D and 3-D simulations, we show that the 2-D cross-sectional models traditionally used to examine flow in faulted formations may not be appropriate. In addition, the influence of a particular type of fault cannot be generalized; depending on the location where contaminants enter the saturated zone, faults may either enhance or inhibit vertical dispersion.

  11. Simulation of the effects of ground-water withdrawals and recharge on ground-water flow in Cape Cod, Martha's Vineyard, and Nantucket Island basins, Massachusetts

    USGS Publications Warehouse

    Masterson, John P.; Barlow, Paul M.

    1994-01-01

    The effects of changing patterns of ground-water pumping and aquifer recharge on the surface-water and ground-water hydrologic systems were determined for the Cape Cod, Martha's Vineyard, and Nantucket Island Basins. Three-dimensional, transient, ground-water-flow modelS that simulate both freshwater and saltwater flow were developed for the f1ow cells of Cape Cod which currently have large-capacity public-supply wells. Only the freshwater-flow system was simulated for the Cape Cod flow cells where public-water supply demands are satisfied by small-capacity domestic wells. Two- dimensional, finite-difference, change models were developed for Martha's Vineyard and Nantucket Island to determine the projected drawdowns in response to projected in-season pumping rates for 180 days of no aquifer recharge. Results of the simulations indicate very little change in the position of the freshwater-saltwater interface from predevelopment flow conditions to projected ground-water pumping and recharge rates for Cape Cod in the year 2020. Results of change model simulations for Martha's Vineyard and Nantucket Island indicate that the greatest impact in response to projected in-season ground-water pumping occurs at the pumping centers and the magnitude of the drawdowns are minimal with respect to the total thickness of the aquifers.

  12. Prediction of Groundwater Flow and Transport Processes in an Urban Area: A Combined Approach of Field Testing and Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Popp, Andrea; Moeck, Christian; Radny, Dirk; Borer, Paul; Affolter, Annette; Epting, Jannis; Huggenberger, Peter; Auckenthaler, Adrian; Schirmer, Mario

    2015-04-01

    Drinking water supply in urban areas is challenging due to different kinds of water use and potential groundwater contamination. We investigate an area where drinking water production is close to different contaminated sites. The study site is characterized by a high complexity of the tectonic and geological setting with a gravel and a karstic aquifer. The two aquifers are partly connected, partly disconnected by an aquitard. To avoid drinking water contamination, artificial groundwater recharge with surface water into the gravel aquifer is used to create a hydraulic barrier between the contaminated sites and the water abstraction wells. Trace compounds, that were found in former times in the surface water but not nowadays, are still detected in the extracted drinking water. Different studies have been performed such as numerical modeling, intensive groundwater monitoring and investigation of drilling cores to get a differentiated overview of the distribution of the contaminants. Back-diffusion from the matrix due to changing hydraulic boundary was stated to be the reason for the actual distribution of the contaminants. In a first approach due to the lack of experimental data or evidence from field measurements, the permeabilities of the karstic aquifer were assumed as homogeneous. In our study, we seek to identify the flow and transport processes within the system including the fracture network in a combined approach of field work and 3D modeling with FEFLOW. During a field campaign we acquired water samples for the analysis of stable water isotopes as well as organic and inorganic compounds. Furthermore, tritium and helium samples were taken to estimate water ages and to determine the flow through the fracture networks. A combination of existing and recently obtained data was used to build and validate a 3D flow and transport model. The simulation of different scenarios such as the water flow for varying injection and extraction rates as well as particle transport from different sources is carried out. To investigate the effect of subsurface heterogeneity, PEST, an independent parameter estimation and uncertainty analysis software, was used. With the calibrated model we will be able to optimize the operational conditions of artificial recharge and drinking water production especially at the boundaries of the production field. Hence, we can provide guidelines for an improved water resource management.

  13. Modeling and assessment of flow and transport in the Hueco Bolson, a transboundary groundwater system: the El Paso / Cuidad Juarez case

    E-print Network

    Nwaneshiudu, Okechukwu

    2009-05-15

    threedimensional numerical groundwater flow and transport model is developed using a current Hueco Bolson groundwater availability model as its basis. The model with contaminant transport is required to access and characterize the extent of vulnerability...

  14. Tracer Tests in the Fractured Rock to Investigate Preferential Groundwater Flow

    NASA Astrophysics Data System (ADS)

    Chan, W.; Chung, L.; Lee, T.; Liu, C.; Chia, Y.; Teng, M.

    2012-12-01

    Hydraulic tests are often used to obtain hydraulic conductivity in the aquifer. Test results usually reflect the average hydraulic conductivity in the surrounding strat. However, in fractured rock, groundwater flows primarily through a few fractures. Saltwater tracer test can be used to detect the direction of groundwater flow, but it was difficult to know the hydraulic connectivity between fractures. In this study, we use a variety of field tests, including tracer test, hydraulic test, and heat-pulse flowmeter test, to locate the permeable fractures and detect the hydraulic connections between boreholes. There are eight test wells and two observation wells on field experimental site in central Taiwan. Geological survey results show that there are at least three sets of joint planes. In order to realize the location of the preferential pathway of groundwater flow, heat-pulse flowmeter measurement was adopted to identify the depth of permeable fractures. Multi-well pumping test was also performed to investigate the hydraulic connectivity between these wells. Tracer tests were then used to detect the hydraulic connectivity of permeable fractures between two wells. Injection of nano zero valent iron in one well and and collection of iron tracer with a magnet array in the other well can specifically locate the permeable fracture and determine the connectivity. Saltwater tracer test result can be used to support that of nano-iron tracer test, and verify the relationship between well water conductivity increases and rock fracture location. The results show that tracer test is a useful tool to investigate the preferential groundwater flow in the fractured rock, but it is essential to flush the mud in fractures prior to the test.

  15. POTENTIAL EFFECTS OF FAULTS ON GROUNDWATER FLOW FOR THE YUCCA FLAT BASIN, NEVADA TEST SITE, NEVADA

    NASA Astrophysics Data System (ADS)

    Dickerson, R. P.; Fryer, W.

    2009-12-01

    The permeability changes resulting from finely comminuted material in fault cores and the fractured and brecciated rock in fault damage zones allows faults to channelize groundwater flow along the plane of the fault. The efficiency of faults as permeability structures depends on fault zone width, fault offset, depth at which the fault developed, type of faulted rock, extent of secondary mineralization, and fault orientation within current stress field. Studies of faulted volcanic rocks at Yucca Mountain, Nevada, indicate that fault zone width and brecciation increase with fault offset, that faulted welded tuff is more permeable than nonwelded or bedded tuff, and that non-hydrothermal secondary mineralization commonly diminishes fracture permeability. These results are applied to the groundwater conceptual flow model for Yucca Flat (YF) on the Nevada Test Site (NTS). Yucca Flat contains Tertiary volcanic rocks similar to thoise at Yucca Mountain deposited on Paleozoic carbonate rocks whose thickness is increased by local thrust-faults. The YF basin contains north-striking normal faults and is bordered by southwest-striking strike-slip faults to the south and east. Fault permeability values derived from faulted volcanic rocks at Yucca Mountain suggests that major normal faults in Yucca Flat potentially manifest permeability values along the fault plane equal to the highest values determined for volcanic aquifers. Numerous minor faults not assigned specific permeability values are assumed to imbue the basin with a hydraulic anisotropy favoring fault-parallel flow. In this scenario groundwater flows generally from north to south in the Yucca Flat basin, even as the head gradient is primarily towards the centrally located Yucca Fault, which acts as the main subsurface drainage feature within the basin. Studies show that the regional stress field has rotated clockwise such that southwest-striking strike-slip faults are currently under tension. In this scenario these strike-slip faults potentially act to channel groundwater out of southern Yucca Flat towards the southwest and into the southern portion of the NTS.

  16. Geochemical changes along a river-groundwater infiltration flow path: Glattfelden, Switzerland

    Microsoft Academic Search

    L. A. Jacobs; M. Kuslys; H. R. von Gunten

    1988-01-01

    Seasonal changes in the river concentrations of key components (carbonate alkalinity, total inorganic carbon, Oâ, NOâ⁻, NHâ{sup +}, Ca, Mg and SiOâ), trace metals (Mn, Fe, Cu, Zn and Cd), and microbial activity are reflected in systematic changes in mass transfer along a saturated river-groundwater infiltration flow path. Organic matter degradation is the predominant process during the early stages of

  17. Paleocollapse structure as a passageway for groundwater flow and contaminant transport

    Microsoft Academic Search

    Wan Fang Zhou

    1997-01-01

    Paleocollapse structure is a rock collapse, resulting from the failure in the geological history of the bedrock overlying\\u000a karstified limestone. Depending on the present hydrogeological conditions within the area of paleocollapse and the internal\\u000a properties of these structures, they can provide a means to facilitate groundwater flow and contaminant transport. Inactive\\u000a paleocollapse structures can be reactivated by human activities such

  18. Estimation of nearshore groundwater discharge and its potential effects on a fringing coral reef.

    PubMed

    Blanco, Ariel C; Watanabe, Atsushi; Nadaoka, Kazuo; Motooka, Shunsuke; Herrera, Eugene C; Yamamoto, Takahiro

    2011-04-01

    Radon (²²²Rn) measurements were conducted in Shiraho Reef (Okinawa, Japan) to investigate nearshore submarine groundwater discharge (SGD(nearshore)) dynamics. Estimated average groundwater flux was 2-3 cm/h (maximum 7-8 cm/h). End-member radon concentration and gas transfer coefficient were identified as major factors influencing flux estimation accuracy. For the 7-km long reef, SGD(nearshore) was 0.39-0.58 m³/s, less than 30% of Todoroki River's baseflow discharge. SGD(nearshore) was spatially and temporally variable, reflecting the strong influence of subsurface geology, tidal pumping, groundwater recharge, and hydraulic gradient. SGD(nearshore) elevated nearshore nitrate concentrations (0.8-2.2 mg/l) to half of Todoroki River's baseflow NO??-N (2-4 mg/L). This increased nearshore Chl-? from 0.5-2 ?g/l compared to the typically low Chl-? (< 0.1-0.4 ?g/l) in the moat. Diatoms and cyanobacteria concentrations exhibited an increasing trend. However, the percentage contributions of diatoms and cyanobacteria significantly decreased and increased, respectively. SGD may significantly induce the proliferation of cyanobacteria in nearshore reef areas. PMID:21295316

  19. Ground-water flow and quality beneath sewage-sludge lagoons, and a comparison with the ground-water quality beneath a sludge-amended landfill, Marion County, Indiana

    USGS Publications Warehouse

    Bobay, K.E.

    1988-01-01

    The groundwater beneath eight sewage sludge lagoons, was studied to characterize the flow regime and to determine whether leachate had infiltrated into the glacio-fluvial sediments. Groundwater quality beneath the lagoons was compared with the groundwater quality beneath a landfill where sludge had been applied. The lagoons and landfills overlie outwash sand and gravel deposits separated by discontinuous clay layers. Shallow groundwater flows away from the lagoons and discharges into the White River. Deep groundwater discharges to the White River and flows southwest beneath Eagle Creek. After an accumulation of at least 2 inches of precipitation during 1 week, groundwater flow is temporarily reversed in the shallow aquifer, and all deep flow is along a relatively steep hydraulic gradient to the southwest. The groundwater is predominantly a calcium bicarbonate type, although ammonium accounts for more than 30% of the total cations in water from three wells. Concentrations of sodium, chloride, sulfate, iron, arsenic, boron, chemical oxygen demand, total dissolved solids, and methylene-blue-active substances indicate the presence of leachate in the groundwater. Concentrations of cadmium, chromium, copper, lead, mercury, nickel, selenium, and zinc were less than detection limits. The concentrations of 16 of 19 constituents or properties of groundwater beneath the lagoons are statistically different than groundwater beneath the landfill at the 0.05 level of significance. Only pH and concentrations of dissolved oxygen and bromide are higher in groundwater beneath the landfill than beneath the lagoons. (USGS)

  20. Parameter estimation for flow in heterogeneous unsaturated porous media

    NASA Astrophysics Data System (ADS)

    Erdal, Daniel; Neuweiler, Insa

    2010-05-01

    The unsaturated zone is an important part of the hydrologic cycle and in modeling of large systems it provides the important link between the land surfaces and groundwater systems. One of the problems when modeling water fluxes in the unsaturated zone is to estimate the model parameters from observations. Due to heterogeneities of the soil, these parameters depend on length scale. Furthermore, even if a perfect measurement of a soil parameter would be available, the difference in scale between measurement and model would still cause a need to upscale the measurements into effective parameters. Given certain properties of the soil structure, this study looks at how much measurement data is required to make a good estimation of the effective parameters for a flow scenario in the unsaturated zone. The estimation of local and effective parameters is done within a Bayesian framework, using a Markov Chain Monte Carlo (MCMC) sampling strategy. MCMC methods have the advantage of not only giving best estimates of parameters, but also provide the full distribution of the estimate, hence making uncertainties and eventual multimodalities easily accessible. In this study the Differential Evolution Adaptive Metropolis (DREAM) algorithm (Vrugt et al. 2008) is used. For the study, data from lab-scale drainage experiments in heterogeneous sand columns of M. Vasin (Vasin et al 2008) are used. In the experiments, the depth averaged water content in two sand columns with different heterogeneous structure was monitored during successive drainage steps using neutron radiography. We estimate the flow parameters for the columns taking successively observations into account. In particular we integrate observations of spatially averaged water content. Results will be presented and discussed on the poster. References Vasin M, Lehmann P, Kaestner A, Hassanein R, Nowak W, Helmig R, Neuweiler I. Drainage in heterogeneous sand columns with different geometric structures. Adv Water Resources 2008;31(9):1205-1220 Vrugt JA, ter Braak CJF, Clark MP, Hyman JM, Robinson BA. Treatment of input uncertainty in hydrologic modeling: Doing hydrology backward with Markov chain Monte Carlo simulation. Water Resources Research 2008;44:W00B09

  1. 3D hydro-mechanically coupled groundwater flow modelling of Pleistocene glaciation effects

    NASA Astrophysics Data System (ADS)

    Rühaak, Wolfram; Bense, Victor F.; Sass, Ingo

    2014-06-01

    Pleistocene glaciation led to temporal and spatial variations of sub-surface pore fluid pressure. In basins covered by ice sheets, fluid flow and recharge rates are strongly elevated during glaciations as compared to inter-glacial periods. Present-day hydrogeological conditions across formerly glaciated areas are likely to still reflect the impact of glaciations that ended locally more than 10 thousand years before present. 3D hydro-mechanical coupled modelling of glaciation can help to improve the management of groundwater resources in formerly glaciated basins. An open source numerical code for solving linear elasticity, which is based on the finite element method (FEM) in 3D, has been developed. By coupling this code with existing 3D flow codes it is possible to enable hydro-mechanical coupled modelling. Results of two benchmark simulations are compared to existing analytical solutions to demonstrate the performance of the newly developed code. While the result for a fluid-structure coupled case is in reasonable agreement with the analytical model, the result for a classical structure-fluid coupled benchmark showed that the analytical solution only matches the numerical result when the relevant coupling parameter (loading efficiency) is known in advance. This indicates that the applicability of widely applied approaches using an extra term in the groundwater flow equation for vertical stress to simulate hydro-mechanical coupling might have to be re-evaluated. A case study with the commercial groundwater simulator FEFLOW demonstrates the newly developed solution.

  2. Groundwater Flow Modeling Using Pmwin Model in the Wakal River Basin, Rajasthan, India

    NASA Astrophysics Data System (ADS)

    Biswas, H.; Melesse, A.; McClain, M.; Sukop, M.

    2008-05-01

    The absence of surface water resources in the driest and largest state of India, Rajasthan, has put pressure on the groundwater resources of the state. The water supply problem is exacerbated by the increasing human population, deforestation, unsustainable land-use and irrigation practices. The problem is even severe during droughts. The monsoon rainfall from June to September is the main source of the groundwater recharge in the region.To be able to exploit this natural resource in a sustainable manner with minimal impact on the environment, there is a need to evaluate the potential of the aquifer in terms of water quantity and replenishment using the tolls of groundwater modeling. A numerical model for regional ground water flow was developed using Processing Modflow for Windows (PMWIN)model for a 120 squre Km watershed in the Wakal River Basin in the Jhadol block, Udaipur District, Rajasthan. The model was calibrated for steady state conditions. Watershed boundary formed the no-flow boundaries and was set around the model except north-east part of the study area, where the boundary had been set as constant head. The modeled area consisted of a 143 columns x 177 rows with one layer which simulated an unconfined aquifer in a hard rock terrain. Hydraulic conductivity of the unconfined aquifer were determined using pump tests conducted in the field and validated from literature of studies in a similar groundwater system. Main input of the model was determined from the 3-months monsoon rainfall. Abstraction rates from open dug wells, and evapotranspiration were applied as output at different cells. A steady-state flow simulation was carried out and calibrated against July 2006 water levels. The calibration was carried out by comparing computed and observed heads at 187 wells. There was a good match between the simulated water level contours with the observed water level contours. This model can be used in the future to run transient simulations for full understanding of the groundwater flux during the dry seasons of the year. Keywords: groundwater, Numerical modeling, PMWIN, steady state flow, Wakal River Basin

  3. Three-Dimensional Numerical Simulation of Density-Dependent Groundwater Flow and Salt Transport Due to Groundwater Pumping in an Unsaturated Fractured Porous Coastal Aquifer System

    NASA Astrophysics Data System (ADS)

    Kihm, J.; Kim, J.

    2009-12-01

    A series of three-dimensional numerical simulations using a generalized multidimensional hydrodynamic dispersion numerical model is performed to analyze density-dependent groundwater flow and salt transport before and during groundwater pumping in an unsaturated fractured porous coastal aquifer system, which is heterogeneous and anisotropic. The coastal aquifer system is located on the western coast of Korea and is composed of the Quaternary alluvium (i.e., alluvial aquifer) underlain by a series of the Precambrian and Cretaceous geologic formations (i.e., bedrock aquifer), which contain numerous planar geologic structures such as bedding planes and joints (joint sets) of various orientations as well as porous rock matrices, with a major fault. The upper part of the geologic formations forms a weathered zone, which is covered by a marine sediment below the mean sea level. A steady-state numerical simulation with model calibration is performed first to obtain initial steady-state spatial distributions of density-dependent groundwater flow and salt transport in the coastal aquifer system before groundwater pumping, and its results are illustrated and analyzed and are also validated reasonably well with respect to the measured groundwater levels and the inferred seawater intrusion front lines (i.e., transition zones between fresh water and salt water). A series of transient-state numerical simulations is then performed using the above-mentioned initial steady-state spatial distributions as initial conditions to obtain spatial and temporal distributions of density-dependent groundwater flow and salt transport in the coastal aquifer system during groundwater pumping with the six different pumping rates at each of the six different potential locations for a new pumping well in the bedrock aquifer, and its results are illustrated and analyzed to suggest optimal location and pumping rate for the new pumping well using the well response function and secondary drinking water quality limit of the seawater-normalized salt concentration. The results of both steady-state and transient-state numerical simulations show that heterogeneity and anisotropy of the geologic media, especially the major fault, as well as the topography and unsaturated zone have significant effects on the spatial and temporal distributions of density-dependent groundwater flow and salt transport in the coastal aquifer system before and during groundwater pumping.

  4. Underground Test Area Subproject Phase I Data Analysis Task. Volume VI - Groundwater Flow Model Documentation Package

    SciTech Connect

    None

    1996-11-01

    Volume VI of the documentation for the Phase I Data Analysis Task performed in support of the current Regional Flow Model, Transport Model, and Risk Assessment for the Nevada Test Site Underground Test Area Subproject contains the groundwater flow model data. Because of the size and complexity of the model area, a considerable quantity of data was collected and analyzed in support of the modeling efforts. The data analysis task was consequently broken into eight subtasks, and descriptions of each subtask's activities are contained in one of the eight volumes that comprise the Phase I Data Analysis Documentation.

  5. Groundwater recharge patterns on hillslopes: exploring the role of soil depth, bedrock permeability, and lateral flow

    NASA Astrophysics Data System (ADS)

    Appels, W. M.; Graham, C. B.; McDonnell, J. J.

    2013-12-01

    The hillslope scale patterns of groundwater recharge are poorly known. On hillslopes with a thin soil mantle overlying bedrock, complex interactions of percolation of water through the soil, permeability contrasts between the soil and the underlying bedrock, and lateral redistribution of water result in large spatial variability of infiltration of water into the bedrock. Here, we combine new measurements and a new modeling approach to explore the following questions: what are the characteristics of the spatial patterns of soil depth, bedrock topography, and bedrock permeability on a hillslope?; and how do these patterns affect the spatial variability of groundwater recharge? We have put new measurements of permeability of the soil mantle and bedrock of the well-studied Panola Mountain experimental hillslope together with previously collected (sub)surface topography and soil depth data. We developed a conceptual model to explore how the recharge pattern varies during different precipitation events. With the geostatistical characteristics of the measured permeability, we generated spatial fields of bedrock permeability for the entire hillslope. We performed model simulations with these random fields and evaluated the resulting spatial distribution of groundwater recharge during individual and series of rainfall events. We found that the average amount of recharge into the bedrock was determined by the ratio between the rate of water delivery through the soil and over the soil-bedrock interface and the bedrock permeability. On the timescale of a single rainfall event, deviations from the average recharge rates were caused by soil depth and local variations of bedrock permeability. When considering a series of rainfall events, a larger fraction of the total rainfall was now delivered at lower rates to the soil-bedrock interface, resulting in a smoother groundwater recharge pattern. Higher groundwater recharge rates were found where lateral flow along the soil-bedrock interface concentrated. Not all areas of concentrated lateral flow on the hillslope featured higher groundwater recharge volumes, because run-on along the soil-bedrock interface was not uniformly generated on the hillslope. Changing the characteristic length of the spatial pattern of bedrock permeability resulted in a different positioning and extent of patches of increased groundwater recharge on the Panola hillslope.

  6. Use of Groundwater Chemistry to Evaluate Subsurface Flow at Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Coleman, N. M.; Dam, W. L.

    2001-12-01

    Yucca Mountain, Nevada is a potential site for the disposal of high-level nuclear wastes. Groundwater at the site occurs in Tertiary volcanic tuffs and in Quaternary valley fill alluvium at lower elevations in the Amargosa Desert. Groundwater seeps downward to the water table through a thick unsaturated zone (UZ), then flows south and southeasterly from Yucca Mountain toward Fortymile Wash. The wash is a highly ephemeral watercourse that drains Fortymile Canyon and Jackass Flats southward. The wash crosses Highway 95 just west of Lathrop Wells, Nevada. Water table contours in Jackass Flats show that groundwater flow strongly converges on the axis of Fortymile Wash, indicating that the same structural conditions that cause topographic lows in the area also enhance the southerly flow of groundwater. Groundwater chemistry is being used to evaluate flow conditions at local and regional scales, and to help resolve technical issues concerning UZ and saturated zone (SZ) flow conditions and dilution processes. A number of perched zones have been found beneath Yucca Mt. in five different wells (Patterson et al., 1998). The major element chemistry of perched water is distinct from pore water chemistry in the UZ and more similar to the water chemistry of the SZ. The perched water is more dilute than the UZ pore waters, with generally lower chloride concentrations. The lower chloride concentration suggests that a fraction of the perched water is recharge that moves downward from the surface through fractures, and has less interaction with the host rock than pore waters. However, only 1 of 5 wells yielded perched water with bomb-pulse levels of tritium. Deuterium and O-18 stable isotope chemistry indicates that perched water has an intermediate composition when compared to SZ groundwater. It is isotopically heavier (less negative) than SZ water beneath Yucca Mountain, but lighter than groundwater from wells along Fortymile Wash where significant recharge occurs. The heaviest deuterium values occur in wells along Fortymile Wash (wells J-13, J-12, JF-3, and UE-29a#2) and are similar to present-day mean precipitation. The highest values occur in well UE-29a#2, where the water table has risen as much as 6 m (20 ft) in response to recharge from runoff events in Fortymile Canyon (Savard, 1998). Water chemistry also shows that significant flow occurs across a major fault zone, the Solitario Canyon Fault. Wells east of the fault have higher dissolved calcium and lower pH and dissolved sodium content than those immediately to the west. Wells SD-6 and H-3 are exceptions. These wells are east of the fault zone and close to it, and their water chemistry resembles that of wells west of the fault. This shows that a significant flux of groundwater crosses the Solitario Canyon Fault from west to east under the prevailing hydraulic gradients. Water table elevations west of the fault are as much as 45 m higher than those to the east, although head differences to the north vanish as the fault displacement lessens. Finally, at a regional scale, the chemical signature of water derived from Yucca Mountain and Jackass Flats can be traced at least 10 km (6 mi) S-SW of Lathrop Wells into the central Amargosa Desert.

  7. Hydrogeologic evaluation and numerical simulation of the Death Valley regional ground-water flow system, Nevada and California

    SciTech Connect

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

    1997-12-31

    Yucca Mountain is being studied as a potential site for a high-level radioactive waste repository. In cooperation with the U.S. Department of Energy, the U.S. Geological Survey is evaluating the geologic and hydrologic characteristics of the ground-water system. The study area covers approximately 100,000 square kilometers between lat 35{degrees}N., long 115{degrees}W and lat 38{degrees}N., long 118{degrees}W and encompasses the Death Valley regional ground-water flow system. Hydrology in the region is a result of both the and climatic conditions and the complex described as dominated by interbasinal flow and may be conceptualized as having two main components: a series of relatively shallow and localized flow paths that are superimposed on deeper regional flow paths. A significant component of the regional ground-water flow is through a thick Paleozoic carbonate rock sequence. Throughout the regional flow system, ground-water flow is probably controlled by extensive and prevalent structural features that result from regional faulting and fracturing. Hydrogeologic investigations over a large and hydrogeologically complex area impose severe demands on data management. This study utilized geographic information systems and geoscientific information systems to develop, store, manipulate, and analyze regional hydrogeologic data sets describing various components of the ground-water flow system.