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Sample records for affect groundwater flow

  1. Groundwater flow and hydrochemistry in mountain areas affected by DSGSDs

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni B.; Frattini, Paolo; Pena Reyes, Fredy; Riva, Federico

    2014-05-01

    Large slope instabilities such as DSGSD and rockslides locally affect the groundwater flow at the slope scale. These phenomena present morphostructures (scarps, counterscarps and trenches) parallel to the slope direction that control the surface water runoff, directing it transversal to the slope dip and favouring its percolation within the slope through the more conductive materials aligned with the trench . This also affects the slope hydrochemistry, locally controlling the solute transport and circulation. The upper Valtellina (Central European Alps, Northern Italy) is characterize by a high density of DSGSD phenomena, with 29 DSGSDs within an area of about 900 km2 (Crosta et al, 2013). The study area ranges from 1150 to 3500 m in altitude, and shows a clear glacial imprint, which significantly influenced the geomorphology and water distribution in the study area. In order to characterize the groundwater flow and the hydrochemistry of the area, we collected historical data analysis (4070 samples from springs, wells, lakes, rivers and public fountains), and we performed four seasonal campaigns, from summer 2012 to spring 2013, to complete a hydrologic year. During these campaigns, we measured the spring discharge, and we collected samples for chemical (anions and cations) and isotopic (tritium, deuterium and O18) analyses in more almost 40 selected spring located throughout the study area. These springs were selected because representative of main spring clusters, with a particular attention to problems related to the presence of Arsenic in high concentration. In this study, we analyze the effect of DSGSD phenomena on the aquifers of upper Valtellina through the quantitative analysis of hydro-chemical and isotopic data. We show how these phenomena affect the ground water flow also in relation to the presence of geological structures that are associated and locally reactivated by DSGSDs.

  2. Analysing Thermal Response Test Data Affected by Groundwater Flow and Surface Temperature Change

    NASA Astrophysics Data System (ADS)

    Verdoya, Massimo; Imitazione, Gianmario; Chiozzi, Paolo; Orsi, Marco; Armadillo, Egidio

    2014-05-01

    Tests that record the underground temperature variation due to a constant heat injected into a borehole (or extracted from it) by means of a carrier fluid are routinely performed to infer subsurface thermal conductivity and borehole thermal resistance, which are needed to size geothermal heat pump systems. The most popular model to analyse temperature-time curves obtained from these tests is the infinite line source (ILS). This model gives appropriate estimations of thermal parameters only if particular hydro-geological conditions are fulfilled. Several flaws can however affect data interpretation with ILS, which is based on strong assumptions like those of a purely conductive heat transfer regime in a homogeneous medium, no vertical heat flow and infinite length of the borehole. Other drawbacks can arise from the difficulty in the proper thermal insulation of the test equipment, and consequently with oscillations of the carrier fluid temperature due to surface temperature changes. In this paper, we focused on the treatment of thermal response test data when both advection and periodic changes of surface temperature occur. We used a moving line source model to simulate temperature-time signals under different hypothesis of Darcy velocity and thermal properties. A random noise was added to the signal in order to mimic high frequency disturbances, possibly caused by equipment operating conditions and/or geological variability. The subsurface thermal conductivity, the Darcy velocity and the borehole thermal resistance were inferred by minimising the root mean square error between the synthetic dataset and the theoretical model. The optimisation was carried out with the Nelder-Mead algorithm, and thermal and hydraulic properties were determined by iterative reprocessing according to a trial-and-error procedure. The inferred thermal and hydraulic parameters are well consistent with the 'a priory' values, and the presence of noise in the synthetic data does not produce

  3. Hydraulic and mechanical properties affecting ground-water flow and aquifer-system compaction, San Joaquin Valley, California

    USGS Publications Warehouse

    Sneed, Michelle

    2001-01-01

    This report summarizes hydraulic and mechanical properties affecting ground-water flow and aquifer-system compaction in the San Joaquin Valley, a broad alluviated intermontane structural trough that constitutes the southern two-thirds of the Central Valley of California. These values will be used to constrain a coupled ground-water flow and aquifer-system compaction model of the western San Joaquin Valley called WESTSIM. A main objective of the WESTSIM model is to evaluate potential future land subsidence that might occur under conditions in which deliveries of imported surface water for agricultural use are reduced and ground-water pumping is increased. Storage values generally are components of the total aquifer-system storage and include inelastic and elastic skeletal storage values of the aquifers and the aquitards that primarily govern the potential amount of land subsidence. Vertical hydraulic conductivity values generally are for discrete thicknesses of sediments, usually aquitards, that primarily govern the rate of land subsidence. The data were compiled from published sources and include results of aquifer tests, stress-strain analyses of borehole extensometer observations, laboratory consolidation tests, and calibrated models of aquifer-system compaction.

  4. Oahu Groundwater Flow Model

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

    Groundwater flow model for the island of Oahu. Data is from the following sources: Rotzoll, K., A.I. El-Kadi. 2007. Numerical Ground-Water Flow Simulation for Red Hill Fuel Storage Facilities, NAVFAC Pacific, Oahu, Hawaii - Prepared TEC, Inc. Water Resources Research Center, University of Hawaii, Honolulu.; Whittier, R.B., K. Rotzoll, S. Dhal, A.I. El-Kadi, C. Ray, G. Chen, and D. Chang. 2004. Hawaii Source Water Assessment Program Report – Volume VII – Island of Oahu Source Water Assessment Program Report. Prepared for the Hawaii Department of Health, Safe Drinking Water Branch. University of Hawaii, Water Resources Research Center. Updated 2008.; and Whittier, R. and A.I. El-Kadi. 2009. Human and Environmental Risk Ranking of Onsite Sewage Disposal Systems – Final. Prepared by the University of Hawaii, Dept. of Geology and Geophysics for the State of Hawaii Dept. of Health, Safe Drinking Water Branch. December 2009.

  5. 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.

  6. Kauai Groundwater Flow Model

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

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

  7. 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.

  8. 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.

  9. Monitoring probe for groundwater flow

    DOEpatents

    Looney, Brian B.; Ballard, Sanford

    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.

  10. 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.

  11. 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.

  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. Groundwater flow and transport modeling

    USGS Publications Warehouse

    Konikow, L.F.; Mercer, J.W.

    1988-01-01

    Deterministic, distributed-parameter, numerical simulation models for analyzing groundwater flow and transport problems have come to be used almost routinely during the past decade. A review of the theoretical basis and practical use of groundwater flow and solute transport models is used to illustrate the state-of-the-art. Because of errors and uncertainty in defining model parameters, models must be calibrated to obtain a best estimate of the parameters. For flow modeling, data generally are sufficient to allow calibration. For solute-transport modeling, lack of data not only limits calibration, but also causes uncertainty in process description. Where data are available, model reliability should be assessed on the basis of sensitivity tests and measures of goodness-of-fit. Some of these concepts are demonstrated by using two case histories. ?? 1988.

  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. West Maui Groundwater Flow Model

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

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

  16. Hawaii Island Groundwater Flow Model

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

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

  17. East Maui Groundwater Flow Model

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

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

  18. 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

  19. 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

  20. Permafrost thaw in a nested groundwater-flow system

    USGS Publications Warehouse

    McKenzie, Jeffery M.; Voss, Clifford I.

    2013-01-01

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

  1. Processes Controlling Temporal Changes in Agriculturally-Affected Groundwater

    NASA Astrophysics Data System (ADS)

    Burow, K. R.; Belitz, K.; Jurgens, B. C.

    2014-12-01

    The National Water Quality Assessment (NAWQA) program of the U.S. Geological Survey includes assessment of groundwater-quality changes with time. To better understand changes at a national scale, NAWQA has implemented smaller scale flow-path studies to evaluate the processes affecting these changes. Flow path studies are designed to sample groundwater of different ages. Wells are sampled for a suite of constituents, including tracers of groundwater age. In the 1990s, a 4.6 km transect of monitoring wells was installed near Fresno in the southern Central Valley of California. The region is dominated by intensive agriculture. The wells were sampled in 1994-95, 2003, and 2013 to provide data on changes in water quality and groundwater age. In 2013, the flow path was extended to a regional scale (30 km) by using existing production wells. Preliminary interpretation of the local-scale flow path indicates that nitrate concentrations in the upper 25 m of the aquifer are higher than the USEPA Maximum Contaminant Level (MCL) for drinking water and variably increase or decrease with time. At intermediate depths (25-40 m), nitrate concentrations are lower and show small to moderate increases. The legacy pesticide 1,2-dibromo-3-chloropropane (DBCP) is degrading at a half-life of about 4-6 years. DBCP is present above the MCL at intermediate depths even though it is has been banned from use for more than 30 years. Both nitrate and DBCP appear to be moving vertically downward through the aquifer. Whereas uranium concentrations are generally below the MCL in the local-scale flow path, concentrations increase along the regional transect, with concentrations nearly an order of magnitude above the MCL in some wells. Further evaluation of processes affecting these constituents (such as source, redox, and mobilization factors) will provide important insight that can be applied to other regions and will assist local water managers.

  2. Revised conceptualization of the North China Basin groundwater flow system: Groundwater age, heat and flow simulations

    NASA Astrophysics Data System (ADS)

    Cao, Guoliang; Han, Dongmei; Currell, Matthew J.; Zheng, Chunmiao

    2016-09-01

    Groundwater flow in deep sedimentary basins results from complex evolution processes on geological timescales. Groundwater flow systems conceptualized according to topography and/or groundwater table configuration generally assume a near-equilibrium state with the modern landscape. However, the time to reach such a steady state, and more generally the timescales of groundwater flow system evolution are key considerations for large sedimentary basins. This is true in the North China Basin (NCB), which has been studied for many years due to its importance as a groundwater supply. Despite many years of study, there remain contradictions between the generally accepted conceptual model of regional flow, and environmental tracer data. We seek to reconcile these contractions by conducting simulations of groundwater flow, age and heat transport in a three dimensional model, using an alternative conceptual model, based on geological, thermal, isotope and historical data. We infer flow patterns under modern hydraulic conditions using this new model and present the theoretical maximum groundwater ages under such a flow regime. The model results show that in contrast to previously accepted conceptualizations, most groundwater is discharged in the vicinity of the break-in-slope of topography at the boundary between the piedmont and central plain. Groundwater discharge to the ocean is in contrast small, and in general there are low rates of active flow in the eastern parts of the basin below the central and coastal plain. This conceptualization is more compatible with geochemical and geothermal data than the previous model. Simulated maximum groundwater ages of ∼1 Myrs below the central and coastal plain indicate that residual groundwater may be retained in the deep parts of the basin since being recharged during the last glacial period or earlier. The groundwater flow system has therefore probably not reached a new equilibrium state with modern-day hydraulic conditions. The

  3. New Insights into the Influence of Structural Controls Affecting Groundwater Flow and Storage Within an Ocean Island Volcano, Mauna Kea, Hawaii

    NASA Astrophysics Data System (ADS)

    Thomas, D. M.; Haskins, E.; Wallin, E.; Pierce, H. A.

    2015-12-01

    The Humu'ula Groundwater Research Project was undertaken on the Island of Hawaii in an effort to characterize the hydrologic structures controlling groundwater movement and storage within Saddle region between Mauna Loa and Mauna Kea volcanoes. In 2013, the project drilled a 1764 m, continuously-cored, borehole from an elevation of 1946 m amsl near the center of the Saddle, and has now completed a second borehole at an elevation of 1645 m on the western edge of the Saddle. Although the stratigraphy of the rocks is similar, dominantly pahoehoe lava flows with somewhat fewer a'a lavas and occasional dike rock intervals, the hydrologic character of the formation in the latter is distinctly different from the former. Whereas the former test hole encountered a few high elevation perched aquifers that were underlain by an inferred regional, dike-impounded, water table at an elevation of 1390 m amsl, the latter bore encountered a sequence of confined aquifers with heads substantially higher than depth of entry. The shallowest of the confined aquifers was encountered at an elevation of 1340 m and showed a hydrostatic head of >160 m when the capping formation was breached. Deeper confined aquifers showed initial heads of > 400 m although none had heads sufficient to discharge at the surface. Most of the confined aquifers were associated with clay-rich ash beds that mantled the more permeable lavas however one of the deeper confined zones, that showed the highest head, was associated with a highly compacted breccia zone that has tentatively been ascribed to an explosive deposit. Chemical analysis of the clasts within this layer is underway to determine whether this deposit is associated with explosive activity of Mauna Kea or with another volcano on the island. Previous geophysical surveys have suggested that these confined aquifers may extend well down the leeward slopes of Mauna Kea. Evidence of multiple confining layers within the flanks of Mauna Kea suggest that its

  4. Glaciation and regional groundwater flow in the Fennoscandian shield

    USGS Publications Warehouse

    Provost, A.M.; Voss, C.I.; Neuzil, C.E.

    2012-01-01

    Regional-scale groundwater flow modeling of the Fennoscandian shield suggests that groundwater flow can be strongly affected by future climate change and glaciation. We considered variable-density groundwater flow in a 1500-km-long and approximately 10-km-deep cross-section through southern Sweden. Groundwater flow and shield brine transport in the cross-sectional model were analyzed under projected surface conditions for the next 140 ka. Simulations suggest that blockage of recharge and discharge by low-permeability permafrost or cold-based ice causes sinking of brine and consequent freshening of near-surface water in areas of natural discharge. Although recharge of basal meltwater is limited by the requirement that water pressure at the base of the ice sheet not exceed the pressure exerted by the weight of the ice, warm-based ice with basal melting creates a potential for groundwater recharge rates much larger than those of present, ice-free conditions. In the simulations, regional-scale redistribution of recharged water by subsurface flow is minor over the duration of a glacial advance (approximately 10 ka). During glacial retreat, significant upward flow of groundwater may occur below the ice sheet owing to pressure release. If the mechanical loading efficiency of the rocks is high, both subsurface penetration of meltwater during glacial advance and up-flow during glacial retreat are reduced because of loading-induced pressure changes. The maximum rate of groundwater discharge in the simulations occurs at the receding ice margin, and some discharge occurs below incursive postglacial seas. Recharge of basal meltwater could decrease the concentration of dissolved solids significantly below present-day levels at depths of up to several kilometers and may bring oxygenated conditions to an otherwise reducing chemical environment for periods exceeding 10 ka.

  5. Considering Barometric Pressure in Groundwater Flow Investigations

    SciTech Connect

    Spane, Frank A. )

    2002-06-18

    Well water-level elevation measurements are commonly used as the basis to delineate groundwater-flow patterns (i.e., flow direction and hydraulic gradient). Barometric pressure fluctuations, however, can have a discernable impact on well water-levels. These barometric effects may lead to erroneous indications of hydraulic head within the aquifer. Total hydraulic head within the aquifer, not well water-level elevation, is the hydrologic parameter for determining groundwater-flow direction and hydraulic gradient conditions. For low-gradient, unconfined aquifer sites exhibiting variable vadose zone characteristics (e.g., thickness, pneumatic diffusivity), barometric pressure fluctuations can also cause actual, temporal changes in lateral flow direction and flow velocity. Discrete water-level measurements used to determine the average or long-term groundwater-flow conditions, therefore, may provide non-representative results. Calculation of the barometric response characteristics for individual wells provides the basis to account for the temporal effects of barometric pressure fluctuations from monitor well measurements, so that average, long-term groundwater-flow pattern behavior can be determined.

  6. Effects of wetlands creation on groundwater flow

    USGS Publications Warehouse

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

    1991-01-01

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

  7. Regression modeling of ground-water flow

    USGS Publications Warehouse

    Cooley, R.L.; Naff, R.L.

    1985-01-01

    Nonlinear multiple regression methods are developed to model and analyze groundwater flow systems. Complete descriptions of regression methodology as applied to groundwater flow models allow scientists and engineers engaged in flow modeling to apply the methods to a wide range of problems. Organization of the text proceeds from an introduction that discusses the general topic of groundwater flow modeling, to a review of basic statistics necessary to properly apply regression techniques, and then to the main topic: exposition and use of linear and nonlinear regression to model groundwater flow. Statistical procedures are given to analyze and use the regression models. A number of exercises and answers are included to exercise the student on nearly all the methods that are presented for modeling and statistical analysis. Three computer programs implement the more complex methods. These three are a general two-dimensional, steady-state regression model for flow in an anisotropic, heterogeneous porous medium, a program to calculate a measure of model nonlinearity with respect to the regression parameters, and a program to analyze model errors in computed dependent variables such as hydraulic head. (USGS)

  8. Groundwater Flow and Arsenic Biogeochemistry in Bangladesh

    NASA Astrophysics Data System (ADS)

    Harvey, C. F.

    2004-12-01

    Although groundwater in Bangladesh is severely contaminated by arsenic, little is known about the complex transient patterns of groundwater flow that flush solutes from aquifers and carry solutes into the subsurface. Hydrologic modeling results for our field site in the Munshiganj district indicate that groundwater flow is vigorous, flushing the aquifer over time-scales of decades and also introducing solute loads into the aquifer with recharge from rice fields, ponds and rivers. The combined hydrologic and biogeochemical results from our field site imply that the biogeochemistry of the aquifer system may not be in steady-state, and that the net effect of competing processes could either increase or decrease arsenic concentrations over the next decades. Modeling results suggest that irrigation has greatly changed the location, timing and chemical content of recharge to the aquifer, drawing large fluxes of anoxic water into the aquifer during the dry season that may mobilize arsenic from oxides in near-surface sediments.

  9. Geomorphic aspects of groundwater flow

    NASA Astrophysics Data System (ADS)

    LaFleur, Robert G.

    The many roles that groundwater plays in landscape evolution are becoming more widely appreciated. In this overview, three major categories of groundwater processes and resulting landforms are considered: (1) Dissolution creates various karst geometries, mainly in carbonate rocks, in response to conditions of recharge, geologic setting, lithology, and groundwater circulation. Denudation and cave formation rates can be estimated from kinetic and hydraulic parameters. (2) Groundwater weathering generates regoliths of residual alteration products at weathering fronts, and subsequent exhumation exposes corestones, flared slopes, balanced rocks, domed inselbergs, and etchplains of regional importance. Groundwater relocation of dissolved salts creates duricrusts of various compositions, which become landforms. (3) Soil and rock erosion by groundwater processes include piping, seepage erosion, and sapping, important agents in slope retreat and headward gully migration. Thresholds and limits are important in many chemical and mechanical groundwater actions. A quantitative, morphometric approach to groundwater landforms and processes is exemplified by selected studies in carbonate and clastic terrains of ancient and recent origins. Résumé Les rôles variés joués par les eaux souterraines dans l'évolution des paysages deviennent nettement mieux connus. La revue faite ici prend en considération trois grandes catégories de processus liés aux eaux souterraines et les formes associées: (1) La dissolution crée des formes karstiques variées, surtout dans les roches carbonatées, en fonction des conditions d'alimentation, du cadre géologique, de la lithologie et de la circulation des eaux souterraines. Les taux d'érosion et de formation des grottes peuvent être estimés à partir de paramètres cinétiques et hydrauliques. (2) L'érosion par les eaux souterraines donne naissance à des régolites, résidus d'altération sur des fronts d'altération, et l'exhumation r

  10. Geomorphic aspects of groundwater flow

    NASA Astrophysics Data System (ADS)

    LaFleur, Robert G.

    The many roles that groundwater plays in landscape evolution are becoming more widely appreciated. In this overview, three major categories of groundwater processes and resulting landforms are considered: (1) Dissolution creates various karst geometries, mainly in carbonate rocks, in response to conditions of recharge, geologic setting, lithology, and groundwater circulation. Denudation and cave formation rates can be estimated from kinetic and hydraulic parameters. (2) Groundwater weathering generates regoliths of residual alteration products at weathering fronts, and subsequent exhumation exposes corestones, flared slopes, balanced rocks, domed inselbergs, and etchplains of regional importance. Groundwater relocation of dissolved salts creates duricrusts of various compositions, which become landforms. (3) Soil and rock erosion by groundwater processes include piping, seepage erosion, and sapping, important agents in slope retreat and headward gully migration. Thresholds and limits are important in many chemical and mechanical groundwater actions. A quantitative, morphometric approach to groundwater landforms and processes is exemplified by selected studies in carbonate and clastic terrains of ancient and recent origins. Résumé Les rôles variés joués par les eaux souterraines dans l'évolution des paysages deviennent nettement mieux connus. La revue faite ici prend en considération trois grandes catégories de processus liés aux eaux souterraines et les formes associées: (1) La dissolution crée des formes karstiques variées, surtout dans les roches carbonatées, en fonction des conditions d'alimentation, du cadre géologique, de la lithologie et de la circulation des eaux souterraines. Les taux d'érosion et de formation des grottes peuvent être estimés à partir de paramètres cinétiques et hydrauliques. (2) L'érosion par les eaux souterraines donne naissance à des régolites, résidus d'altération sur des fronts d'altération, et l'exhumation r

  11. Factors Affecting the Sustainability of Groundwater-Source Cooling

    NASA Astrophysics Data System (ADS)

    Ferguson, G. A.; Woodbury, A. D.

    2004-12-01

    The use of groundwater in thermal applications has grown in popularity due to increases in environmental awareness and rising energy costs. While this source of energy is generally seen as beneficial to the environment, changes in subsurface temperatures resulting from thermal development and other factors may make this practice unsustainable. An example of such changes in subsurface temperatures has been observed in Winnipeg, Manitoba, where groundwater is extensively used for cooling applications. Temperatures in a regional aquifer beneath the city were found to be as much as ten degrees Celsius greater than those measured in surrounding rural areas. Numerical modeling indicates increases in temperature of up to 5 degrees Celsius can be attributed to downward heat flow originating in buildings in many cases. Areas where increases in temperature were found to be greater corresponded to areas where water is being injected into the aquifer. This water is being produced in the process of using groundwater for cooling applications, such as air conditioning and industrial cooling, and is being injected back into the aquifer to maintain hydraulic head and reduce the demand on Winnipeg's sewer system. In most cases, the heat introduced by injecting this water is significantly affecting temperatures at the production well of the same system and numerical modeling indicates that this is inevitable with the current method of development. The combination of heat loss from buildings and injection of heated water is largely responsible for a reduction in the efficiency of groundwater as a coolant and may eventually make the use of groundwater in cooling applications unsustainable.

  12. IN SITU FLOW METERS AROUND A GROUNDWATER CIRCULATION WELL (ABSTRACT)

    EPA Science Inventory

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

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

    EPA Science Inventory

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

  14. 3PE: A Tool for Estimating Groundwater Flow Vectors

    EPA Science Inventory

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

  15. Comparison of groundwater flow in Southern California coastal aquifers

    USGS Publications Warehouse

    Hanson, Randall T.; Izbicki, John A.; Reichard, Eric G.; Edwards, Brian D.; Land, Michael; Martin, Peter

    2009-01-01

    Development of the coastal aquifer systems of Southern California has resulted in overdraft, changes in streamflow, seawater intrusion, land subsidence, increased vertical flow between aquifers, and a redirection of regional flow toward pumping centers. These water-management challenges can be more effectively addressed by incorporating new understanding of the geologic, hydrologic, and geochemical setting of these aquifers. Groundwater and surface-water flow are controlled, in part, by the geologic setting. The physiographic province and related tectonic fabric control the relation between the direction of geomorphic features and the flow of water. Geologic structures such as faults and folding also control the direction of flow and connectivity of groundwater flow. The layering of sediments and their structural association can also influence pathways of groundwater flow and seawater intrusion. Submarine canyons control the shortest potential flow paths that can result in seawater intrusion. The location and extent of offshore outcrops can also affect the flow of groundwater and the potential for seawater intrusion and land subsidence in coastal aquifer systems. As coastal aquifer systems are developed, the source and movement of ground-water and surface-water resources change. In particular, groundwater flow is affected by the relative contributions of different types of inflows and outflows, such as pump-age from multi-aquifer wells within basal or upper coarse-grained units, streamflow infiltration, and artificial recharge. These natural and anthropogenic inflows and outflows represent the supply and demand components of the water budgets of ground-water within coastal watersheds. They are all significantly controlled by climate variability related to major climate cycles, such as the El Niño–Southern Oscillation and the Pacific Decadal Oscillation. The combination of natural forcings and anthropogenic stresses redirects the flow of groundwater and either

  16. Modeling groundwater flow on massively parallel computers

    SciTech Connect

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

    1994-12-31

    The authors will explore the numerical simulation of groundwater flow in three-dimensional heterogeneous porous media. An interdisciplinary team of mathematicians, computer scientists, hydrologists, and environmental engineers is developing a sophisticated simulation code for use on workstation clusters and MPPs. To date, they have concentrated on modeling flow in the saturated zone (single phase), which requires the solution of a large linear system. they will discuss their implementation of preconditioned conjugate gradient solvers. The preconditioners under consideration include simple diagonal scaling, s-step Jacobi, adaptive Chebyshev polynomial preconditioning, and multigrid. They will present some preliminary numerical results, including simulations of groundwater flow at the LLNL site. They also will demonstrate the code`s scalability.

  17. Hydrogeochemical Indicators of Groundwater Flow Systems in the Yangwu River Alluvial Fan, Xinzhou Basin, Shanxi, China

    NASA Astrophysics Data System (ADS)

    Han, Dongmei; Liang, Xing; Jin, Menggui; Currell, Matthew J.; Han, Ying; Song, Xianfang

    2009-08-01

    Based on analysis of groundwater hydrochemical and isotopic indicators, this article aims to identify the groundwater flow systems in the Yangwu River alluvial fan, in the Xinzhou Basin, China. Groundwater δ2H and δ18O values indicate that the origin of groundwater is mainly from precipitation, with local evaporative influence. d-excess values lower than 10% in most groundwaters suggest a cold climate during recharge in the area. Major ion chemistry, including rCa/rMg and rNa/rCl ratios, show that groundwater salinization is probably dominated by water-rock interaction (e.g., silicate mineral weathering, dissolution of calcite and dolomite and cation exchange) in the Yangwu River alluvial fan, and locally by intensive evapotranspiration in the Hutuo River valley. Cl and Sr concentrations follow an increasing trend in shallow groundwater affected by evaporation, and a decreasing trend in deep groundwater. 87Sr/86Sr ratios reflect the variety of lithologies encountered during throughflow. The groundwater flow systems (GFS) of the Yangwu River alluvial fan include local and intermediate flow systems. Hydrogeochemical modeling results, simulated using PHREEQC, reveal water-rock interaction processes along different flow paths. This modeling method is more effective for characterizing flow paths in the intermediate system than in the local system. Artificial exploitation on groundwater in the alluvial fan enhances mixing between different groundwater flow systems.

  18. Hydrogeochemical indicators of groundwater flow systems in the Yangwu River alluvial fan, Xinzhou Basin, Shanxi, China.

    PubMed

    Han, Dongmei; Liang, Xing; Jin, Menggui; Currell, Matthew J; Han, Ying; Song, Xianfang

    2009-08-01

    Based on analysis of groundwater hydrochemical and isotopic indicators, this article aims to identify the groundwater flow systems in the Yangwu River alluvial fan, in the Xinzhou Basin, China. Groundwater delta(2)H and delta(18)O values indicate that the origin of groundwater is mainly from precipitation, with local evaporative influence. d-excess values lower than 10% in most groundwaters suggest a cold climate during recharge in the area. Major ion chemistry, including rCa/rMg and rNa/rCl ratios, show that groundwater salinization is probably dominated by water-rock interaction (e.g., silicate mineral weathering, dissolution of calcite and dolomite and cation exchange) in the Yangwu River alluvial fan, and locally by intensive evapotranspiration in the Hutuo River valley. Cl and Sr concentrations follow an increasing trend in shallow groundwater affected by evaporation, and a decreasing trend in deep groundwater. (87)Sr/(86)Sr ratios reflect the variety of lithologies encountered during throughflow. The groundwater flow systems (GFS) of the Yangwu River alluvial fan include local and intermediate flow systems. Hydrogeochemical modeling results, simulated using PHREEQC, reveal water-rock interaction processes along different flow paths. This modeling method is more effective for characterizing flow paths in the intermediate system than in the local system. Artificial exploitation on groundwater in the alluvial fan enhances mixing between different groundwater flow systems. PMID:19548025

  19. Basin wide Nitrate-Nitrogen pollution of groundwater, Miyakonojo, Japan, with the relation of the regional Groundwater flow system

    NASA Astrophysics Data System (ADS)

    Mikami, K.; Shimada, J.; Zikuzono, Y.

    2006-12-01

    Miyakonojo basin is well-known agriculture area in Southern Kyushu, Japan and highly depends on groundwater resources for their everyday use. Local unconfined groundwater aquifer is widely polluted by Nitrate-Nitrogen originated from agriculture. It will become serious problem if this unconfined Nitrate pollution enlarges into the confined aquifer system which is used for local city water source. However, the detailed groundwater flow system between unconfined and confined aquifer system has not been cleared yet. The detailed three dimensional groundwater flow system study has been done by using existing wells in a basin to understand the three dimensional distribution pattern of Nitrate-Nitrogen in the aquifer. The field sampling for unconfined, intermediate and confined groundwater was done in July, 2005 and February, 2006 for about 200 wells to analyze inorganic water chemistry, hydrogen / oxygen stable isotopes and tritium. For the unconfined groundwater, there exists clear difference for the groundwater flow pattern between the eastern and western basin, which is mostly affected by the surface topography. The unconfined groundwater flowed into the confined aquifer at the eastern part of a basin, while in the western part of a basin the unconfined groundwater on a plateau flowed into the confined aquifer somehow, but most part of the unconfined groundwater has been discharge out to small river valleys between plateaus. While for the confined groundwater, the topographic effect has been disappeared and basin scale groundwater flow from the basin margin toward the basin center is dominated. In the unconfined aquifer, basin wide distribution of Nitrate-Nitrogen content has been recognized and it is relatively higher in the western basin where the cattle farming are dominated. While in the confined aquifer, there are some high Nitrate-Nitrogen spots but do not have regional trend. It is considered that some part of the basin has not distributed the welded tuff

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

    USGS Publications Warehouse

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

    2013-01-01

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

  1. Connections between groundwater flow and transpiration partitioning.

    PubMed

    Maxwell, Reed M; Condon, Laura E

    2016-07-22

    Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes. PMID:27463671

  2. Connections between groundwater flow and transpiration partitioning

    NASA Astrophysics Data System (ADS)

    Maxwell, Reed M.; Condon, Laura E.

    2016-07-01

    Understanding freshwater fluxes at continental scales will help us better predict hydrologic response and manage our terrestrial water resources. The partitioning of evapotranspiration into bare soil evaporation and plant transpiration remains a key uncertainty in the terrestrial water balance. We used integrated hydrologic simulations that couple vegetation and land-energy processes with surface and subsurface hydrology to study transpiration partitioning at the continental scale. Both latent heat flux and partitioning are connected to water table depth, and including lateral groundwater flow in the model increases transpiration partitioning from 47 ± 13 to 62 ± 12%. This suggests that lateral groundwater flow, which is generally simplified or excluded in Earth system models, may provide a missing link for reconciling observations and global models of terrestrial water fluxes.

  3. Groundwater flow as a cooling agent of the continental lithosphere

    NASA Astrophysics Data System (ADS)

    Kooi, Henk

    2016-03-01

    Groundwater that flows through the outer shell of the Earth as part of the hydrologic cycle influences the distribution of heat and, thereby, the temperature field in the Earth’s crust. Downward groundwater flow in recharge areas lowers crustal temperatures, whereas upward flow in discharge areas tends to raise temperatures relative to a purely conductive geothermal regime. Here I present numerical simulations of generalized topography-driven groundwater flow. The simulations suggest that groundwater-driven convective cooling exceeds groundwater-driven warming of the Earth’s crust, and hence that groundwater flow systems cause net temperature reductions of groundwater basins. Moreover, the simulations demonstrate that this cooling extends into the underlying crust and lithosphere. I find that horizontal components of groundwater flow play a central role in this net subsurface cooling by conveying relatively cold water to zones of upward groundwater flow. The model calculations suggest that the crust and lithosphere beneath groundwater basins can cool by several tens of degrees Celsius where groundwater flows over large distances in basins that consist of crustal rock. In contrast, groundwater-induced cooling is small in unconsolidated sedimentary settings, such as deltas.

  4. Coupled Groundwater and Heat Flow in the Tahoe Basin Region

    NASA Astrophysics Data System (ADS)

    Trask, J. C.

    2002-12-01

    We propose that recent developments in available temperature probe technology and improvements in appropriate modeling software, together with the advent of desktop high-speed computing, have enabled the thermal analysis approach to be an inexpensive, robust, and practical way to constrain groundwater flow fields in a wide variety of environments. We present field measurements and numerical models of coupled heat and groundwater flow in the Tahoe Basin region. In montane regions such as the Tahoe Basin, steep topography provides a driving force for deep groundwater flow. Deep groundwater flow re-routes subsurface heat flow, impacting temperature gradients to depth, including the shallow subsurface (<100m depth). In the Tahoe Basin region, the magnitude of deep groundwater flow on the areal or regional scale has been largely unknown. We present examples of borehole temperature profiles that constrain possible areal groundwater flow patterns, including the magnitude of flow beneath the bottom of boreholes probed.

  5. Patterns in groundwater chemistry resulting from groundwater flow

    NASA Astrophysics Data System (ADS)

    Stuyfzand, Pieter J.

    Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic-methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15m and of adsorbed marine cations (Na+, K+, and Mg2+) as much as 2500m in the flow direction is shown to correspond with about 5000yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Résumé Les écoulements souterrains influencent les différents types hydrochimiques, parce que l'écoulement réduit le mélange par diffusion, porte les marques chimiques de changements biologiques et anthropiques dans la zone d'alimentation et lessive le système aquifère. Ces types dans leur ensemble sont surtout déterminés par des différences dans le flux d'eau météorique traversant le sous-sol. Dans les "hydrosomes" (masses d'eau d'origine déterminée), les lignes marquant une évolution prograde (séquence de faciès) se développent normalement dans la direction de l'écoulement souterrain : depuis des fluctuations fortes de la

  6. 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

  7. Groundwater Recharge and Flow Processes in Taihang Mountains, a Semi-humid Region, North China

    NASA Astrophysics Data System (ADS)

    Sakakibara, Koichi; Tsujimura, Maki; Song, Xianfang; Zhang, Jie

    2015-04-01

    Groundwater flow/recharge variations in time and space are crucial for effective water management especially in semi-arid and semi-humid regions. In order to reveal comprehensive groundwater flow/recharge processes in a catchment with a large topographical relief and seasonal hydrological variations, intensive field surveys were undertaken at 4 times in different seasons (June 2011, August 2012, November 2012, February 2014) in the Wangkuai watershed, Taihang mountains, which is a main groundwater recharge area of the North China Plain. The groundwater, spring, stream water and reservoir water were taken, and inorganic solute constituents and stable isotopes of oxygen-18 and deuterium were determined on all water samples. Also, the stream flow rate and the depth of groundwater table were observed. The stable isotopic compositions and inorganic solute constituents in the groundwater are depleted and shown similar values as those of the surface water at the mountain-plain transitional area. Additionally, the groundwater in the vicinity of the Wangkuai Reservoir presents clearly higher stable isotopic compositions and lower d-excess than those of the stream water, indicating the groundwater around the reservoir is affected by evaporation same as the Wangkuai Reservoir itself. Hence, the surface water in the mountain-plain transitional area and Wangkuai Reservoir are principal groundwater recharge sources. An inversion analysis and simple mixing model were applied in the Wangkuai watershed using stable isotopes of oxygen-18 and deuterium to construct a groundwater flow model. The model shows that multi-originated groundwater flows from upstream to downstream along topography with certain mixing. In addition, the groundwater recharge occurs dominantly at the altitude from 421 m to 953 m, and the groundwater recharge rate by the Wangkuai Reservoir is estimated to be 2.4 % of the total groundwater recharge in the Wangkuai watershed. Therefore, the stream water and

  8. Evaluation of processes affecting 1,2-dibromo-3-chloropropane (DBCP) concentrations in ground water in the eastern San Joaquin Valley, California : analysis of chemical data and ground-water flow and transport simulations

    USGS Publications Warehouse

    Burow, Karen R.; Panshin, Sandra Y.; Dubrovsky, Neil H.; Vanbrocklin, David; Fogg, Graham E.

    1999-01-01

    A conceptual two-dimensional numerical flow and transport modeling approach was used to test hypotheses addressing dispersion, transformation rate, and in a relative sense, the effects of ground- water pumping and reapplication of irrigation water on DBCP concentrations in the aquifer. The flow and transport simulations, which represent hypothetical steady-state flow conditions in the aquifer, were used to refine the conceptual understanding of the aquifer system rather than to predict future concentrations of DBCP. Results indicate that dispersion reduces peak concentrations, but this process alone does not account for the apparent decrease in DBCP concentrations in ground water in the eastern San Joaquin Valley. Ground-water pumping and reapplication of irrigation water may affect DBCP concentrations to the extent that this process can be simulated indirectly using first-order decay. Transport simulation results indicate that the in situ 'effective' half-life of DBCP caused by processes other than dispersion and transformation to BAA could be on the order of 6 years.

  9. When is groundwater flow an important consideration in ground surface temperature reconstructions?

    NASA Astrophysics Data System (ADS)

    Ferguson, G.; Woodbury, A. D.; Beltrami, H.

    2005-12-01

    The utility of subsurface temperatures in paleoclimate studies has become well established in recent years. However, there are many different factors that could cause questioning of the result of ground surface temperature (GST) reconstructions from temperature measured in boreholes. One of these factors is groundwater flow, particularly downward groundwater flow. In this case, the resulting curvature in the temperature profile is similar to that observed in many conductive environments where GST has increased over the past century. Simulations of heat flow with steady-state groundwater flow and constant GST indicate that groundwater flow will only significantly affect groundwater reconstructions when Peclet numbers are greater than 0.1 to 1.0. This generally occurs in areas with moderately high recharge rates. Here we show how meteorological records and information on permeability of the rocks and soils in the vicinity of a borehole can be used boreholes in areas where advection will have a minimal effect on GST reconstructions.

  10. Groundwater Flow Model for Taos, New Mexico

    NASA Astrophysics Data System (ADS)

    Burck, P. W.; Barroll, P. W.; Core, A. B.; Rappuhn, D.

    2003-12-01

    The New Mexico Office of the State Engineer - Hydrology Bureau (OSE) has developed a regional groundwater flow model for Taos, New Mexico. The MODFLOW 2000 model will serve as a tool to evaluate alternatives in settlement negotiations in an on-going water rights adjudication. If current settlement negotiations fail, it is conceivable that the model might be used in support of litigation. OSE produced the model in cooperation with technical representatives of the various parties to the adjudication. Regional hydrogeologic data including well records, aquifer test results, stream flow measurements and seepage studies have been shared relatively freely among the parties. A recent deep drilling program conducted in conjunction with the negotiation effort has added substantially to the hydrogeologic data set. Among the hydrologic processes simulated by the model are mountain front recharge; areal recharge from precipitation; evapotranspiration; discharge from springs; river and stream flow; accretions to groundwater from irrigation return flow, seepage from acequias, canals, and ditches, and deep percolation; and pumping by municipal entities and mutual domestic water users associations. The resulting model files are available for all parties to review and evaluate. Comments are assessed and many have resulted in significant improvements to the model. At this stage, however, it is unclear whether adopting this cooperative approach will increase the likelihood of model acceptance by the parties.

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

    USGS Publications Warehouse

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

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  13. Is in situ stress important to groundwater flow in shallow fractured rock aquifers?

    NASA Astrophysics Data System (ADS)

    Mortimer, L.; Aydin, A.; Simmons, C. T.; Love, A. J.

    2011-03-01

    SummaryIn situ stress affects the permeability tensor of fractured rock masses at depth but its effect on shallow to near-surface fractured rock aquifers has received little attention. This is partly because stress-related effects on groundwater flow at shallow depths are difficult to identify and characterise due to the complex interactions between all of the inherent properties of a fractured rock aquifer. These properties include the factors that dominantly control groundwater flow: fracture network density, geometry, connectivity and infill. Furthermore, surface processes such as weathering, erosion and unloading alter the original hydraulic nature (connectivity, transmissivity) of fractured rock masses resulting in higher degrees of spatial heterogeneity within shallow flow systems. These processes and interactions often mask the influence of in situ stress fields on fracture network permeability and groundwater flow. In this study, an integrated analysis of local area fracture networks, borehole geophysical logs, borehole groundwater yields and hydromechanical models demonstrate that in situ stress does affect groundwater flow in shallow (<200 m) fractured rock aquifers by altering fracture hydraulic aperture distributions, fracture network connectivity and groundwater flow rates via fracture deformation processes. In particular, a comparison between representative models of deformed (stressed state) and undeformed (zero stress state) fracture networks showed that below 100 m depth, groundwater flow rates could decrease several fold under the influence of the contemporary stress field. This prediction was highly consistent with the field observations. In contrast, groundwater flow modelling of shallow fractured rock aquifers is typically conducted under the assumption that permeability is independent of the state of stress. A key finding of this study is that in situ stress may be a more important control on both local and regional scale shallow groundwater

  14. Guidelines for Evaluating Ground-Water Flow Models

    USGS Publications Warehouse

    Reilly, Thomas E.; Harbaugh, Arlen W.

    2004-01-01

    Ground-water flow modeling is an important tool frequently used in studies of ground-water systems. Reviewers and users of these studies have a need to evaluate the accuracy or reasonableness of the ground-water flow model. This report provides some guidelines and discussion on how to evaluate complex ground-water flow models used in the investigation of ground-water systems. A consistent thread throughout these guidelines is that the objectives of the study must be specified to allow the adequacy of the model to be evaluated.

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

    USGS Publications Warehouse

    Yager, R.M.

    1998-01-01

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

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

    SciTech Connect

    Moran, J E; Hudson, G B

    2005-08-31

    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 validation, in conceptual or numerical models of groundwater flow. The Groundwater Ambient Monitoring and Assessment Program, sponsored by the California State Water Resources Control Board, and carried out in collaboration with the U.S. Geological Survey, has provided the means to gather an unprecedented number of tritium-helium groundwater ages in the basins of California. As the examples below illustrate, a collection of groundwater ages in a basin allows delineation of recharge areas (youngest ages), bulk flow rates and flowpaths, as well as a means of assessing susceptibility to anthropogenic contaminants.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  18. Analysis of groundwater flow in mountainous, headwater catchments with permafrost

    NASA Astrophysics Data System (ADS)

    Evans, Sarah G.; Ge, Shemin; Liang, Sihai

    2015-12-01

    Headwater catchments have a direct impact on the water resources of downstream lowland regions as they supply freshwater in the form of surface runoff and discharging groundwater. Often, these mountainous catchments contain expansive permafrost that may alter the natural topographically controlled groundwater flow system. As permafrost could degrade with climate change, it is imperative to understand the effect of permafrost on groundwater flow in headwater catchments. This study characterizes groundwater flow in mountainous headwater catchments and evaluates the effect of permafrost in the context of climate change on groundwater movement using a three-dimensional, finite element, hydrogeologic model. The model is applied to a representative headwater catchment on the Qinghai-Tibet Plateau, China. Results from the model simulations indicate that groundwater contributes significantly to streams in the form of baseflow and the majority of groundwater flow is from the shallow aquifer above the permafrost, disrupting the typical topographically controlled flow pattern observed in most permafrost-free headwater catchments. Under a warming scenario where mean annual surface temperature is increased by 2°C, reducing the areal extent of permafrost in the catchment, groundwater contribution to streamflow may increase three-fold. These findings suggest that, in headwater catchments, permafrost has a large influence on groundwater flow and stream discharge. Increased annual air temperatures may increase groundwater discharge to streams, which has implications for ecosystem health and the long-term availability of water resources to downstream regions.

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

    USGS Publications Warehouse

    Cooley, Richard L.

    1985-01-01

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

  20. Simulation of groundwater flow and effects of groundwater irrigation on stream base flow in the Elkhorn and Loup River Basins, Nebraska, 1895-2055-Phase Two

    USGS Publications Warehouse

    Stanton, Jennifer S.; Peterson, Steven M.; Fienen, Michael N.

    2010-01-01

    base flow from the 1970s to the end of the calibration period for the Elkhorn River at Norfolk, Beaver Creek at Genoa, and Cedar River near Fullerton. Effects of groundwater irrigation on stream base flow were predicted using several methods: (1) simulated base-flow depletion was mapped to represent the percentage of water pumped from a hypothetical well during 2006 through 2055 that corresponds to base-flow depletions at the end of that 50-year period; (2) the groundwater-flow simulation predicted changes in stream base flow that result from modifying the number of irrigated acres in a 25-year period (2009 through 2033); and (3) a simulation-optimization model determined the minimum reduction of groundwater pumpage that would be necessary in the Elkhorn River Basin in a 25-year period (2009 through 2033) to comply with various hypothetical base-flow requirements for the Elkhorn River. The results are not intended to determine specific management plans that must be adopted, but rather to improve the understanding of how base flow is affected by irrigation. A 50-year simulation (2006-55) indicated that depletions of less than 10 percent of pumpage mainly occur in areas that are about 10 miles or farther from the Elkhorn and Loup Rivers and their tributaries. The calibrated simulation was used to predict the 25-year effect on base flow of a 10 percent decrease in irrigated acres and the effect of increasing acres at the presently (2010) allowed rate. Hypothesized changes to irrigated acres were applied only to areas where mapped base-flow depletions were at least 10 percent of pumpage. The effect of changes in irrigated acres includes the combined effects of changes to pumpage and additional recharge from irrigated acres. When irrigated acres were decreased by 10 percent within selected areas of four Natural Resources Districts (a total reduction of about 120,000 acres and a 5 percent reduction in irrigation pumpage), simulated base flow was predicted to inc

  1. Is there a geomorphic expression of interbasin groundwater flow in watersheds? Interactions between interbasin groundwater flow, springs, streams, and geomorphology

    NASA Astrophysics Data System (ADS)

    Frisbee, Marty D.; Tysor, Elizabeth H.; Stewart-Maddox, Noah S.; Tsinnajinnie, Lani M.; Wilson, John L.; Granger, Darryl E.; Newman, Brent D.

    2016-02-01

    Interbasin groundwater flow (IGF) can play a significant role in the generation and geochemical evolution of streamflow. However, it is exceedingly difficult to identify IGF and to determine the location and quantity of water that is exchanged between watersheds. How does IGF affect landscape/watershed geomorphic evolution? Can geomorphic metrics be used to identify the presence of IGF? We examine these questions in two adjacent sedimentary watersheds in northern New Mexico using a combination of geomorphic/landscape metrics, springflow residence times, and spatial geochemical patterns. IGF is expressed geomorphically in the landscape placement of springs and flow direction and shape of stream channels. Springs emerge preferentially on one side of stream valleys where landscape incision has intercepted IGF flow paths. Stream channels grow toward the IGF source and show little bifurcation. In addition, radiocarbon residence times of springs decrease and the geochemical composition of springs changes as the connection to IGF is lost.

  2. An Integrated Approach on Groundwater Flow and Heat/Solute Transport for Sustainable Groundwater Source Heat Pump (GWHP) System Operation

    NASA Astrophysics Data System (ADS)

    Park, D. K.; Bae, G. O.; Joun, W.; Park, B. H.; Park, J.; Park, I.; Lee, K. K.

    2015-12-01

    The GWHP system uses a stable temperature of groundwater for cooling and heating in buildings and thus has been known as one of the most energy-saving and cost-efficient renewable energy techniques. A GWHP facility was installed at an island located at the confluence of North Han and South Han rivers, Korea. Because of well-developed alluvium, the aquifer is suitable for application of this system, extracting and injecting a large amount of groundwater. However, the numerical experiments under various operational conditions showed that it could be vulnerable to thermal interference due to the highly permeable gravel layer, as a preferential path of thermal plume migration, and limited space for well installation. Thus, regional groundwater flow must be an important factor of consideration for the efficient operation under these conditions but was found to be not simple in this site. While the groundwater level in this site totally depends on the river stage control of Paldang dam, the direction and velocity of the regional groundwater flow, observed using the colloidal borescope, have been changed hour by hour with the combined flows of both the rivers. During the pumping and injection tests, the water discharges in Cheongpyeong dam affected their respective results. Moreover, the measured NO3-N concentrations might imply the effect of agricultural activities around the facility on the groundwater quality along the regional flow. It is obvious that the extraction and injection of groundwater during the facility operation will affect the fate of the agricultural contaminants. Particularly, the gravel layer must also be a main path for contaminant migration. The simulations for contaminant transport during the facility operation showed that the operation strategy for only thermal efficiency could be unsafe and unstable in respect of groundwater quality. All these results concluded that the integrated approach on groundwater flow and heat/solute transport is necessary

  3. Wave-Induced Groundwater Flows in a Freshwater Beach Aquifer

    NASA Astrophysics Data System (ADS)

    Malott, S. S.; Robinson, C. E.; O'Carroll, D. M.

    2014-12-01

    Wave-induced recirculation across the sediment-water interface can impact the transport of pollutants through a beach aquifer and their ultimate flux into coastal waters. The fate of nutrients (e.g. from septic and agricultural sources) and fecal indicator bacteria (e.g. E. coil) near the sediment-water interface are of particular concern as these pollutants often lead to degradation of recreational water quality and nearshore ecosystems. This paper presents detailed field measurements of groundwater flows in a freshwater beach aquifer on Lake Huron over periods of intensified wave conditions. Quantifying wave-driven processes in a freshwater beach aquifer enables wave effects to be studied in isolation from density and tidal effects that complicate groundwater flows in marine beaches. Water exchange across the sediment-water interface and groundwater flow patterns were measured using groundwater wells, arrays of vertically nested pressure transducers and manometers. Results show that wave action induces rapid infiltration/exfiltration across the sediment-water interface and a larger recirculation cell through the beach aquifer. Field data is used to validate a numerical groundwater model of wave-induced groundwater flows. While prior studies have simulated the effects of waves on beach groundwater flows, this study is the first attempt to validate these sophisticated modeling approaches. Finally, field data illustrating the impact of wave-induced groundwater flows on nutrient and bacteria fate and transport in beach aquifers will also be presented.

  4. 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

  5. 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.

  6. 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.

  7. Regional Groundwater Processes and Flow Dynamics from Age Tracer Data

    NASA Astrophysics Data System (ADS)

    Morgenstern, Uwe; Stewart, Mike K.; Matthews, Abby

    2016-04-01

    Age tracers are now used in New Zealand on regional scales for quantifying the impact and lag time of land use and climate change on the quantity and quality of available groundwater resources within the framework of the National Policy Statement for Freshwater Management 2014. Age tracers provide measurable information on the dynamics of groundwater systems and reaction rates (e.g. denitrification), essential for conceptualising the regional groundwater - surface water system and informing the development of land use and groundwater flow and transport models. In the Horizons Region of New Zealand, around 200 wells have tracer data available, including tritium, SF6, CFCs, 2H, 18O, Ar, N2, CH4 and radon. Well depths range from shallower wells in gravel aquifers in the Horowhenua and Tararua districts, and deeper wells in the aquifers between Palmerston North and Wanganui. Most of the groundwater samples around and north of the Manawatu River west of the Tararua ranges are extremely old (>100 years), even from relatively shallow wells, indicating that these groundwaters are relatively disconnected from fresh surface recharge. The groundwater wells in the Horowhenua tap into a considerably younger groundwater reservoir with groundwater mean residence time (MRT) of 10 - 40 years. Groundwater along the eastern side of the Tararua and Ruahine ranges is significantly younger, typically <5 years MRT. Vertical groundwater recharge rates, as deduced from groundwater depth and MRT, are extremely low in the central coastal area, consistent with confined groundwater systems, or with upwelling of old groundwater close to the coast. Very low vertical recharge rates along the Manawatu River west of the Manawatu Gorge indicate upwelling groundwater conditions in this area, implying groundwater discharge into the river is more likely here than loss of river water into the groundwater system. High recharge rates observed at several wells in the Horowhenua area and in the area east of

  8. Locating groundwater flow in karst by acoustic emission surveys

    SciTech Connect

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

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  10. 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

  11. Soil-aquifer phenomena affecting groundwater under vertisols: a review

    NASA Astrophysics Data System (ADS)

    Kurtzman, D.; Baram, S.; Dahan, O.

    2015-09-01

    Vertisols are cracking clayey soils that: (i) usually form in alluvial lowlands where normally, groundwater pools into aquifers, (ii) have different types of voids (due to cracking) which make flow and transport of water, solutes and gas complex, and (iii) are regarded as fertile soils in many areas. The combination of these characteristics results in the unique soil-aquifer phenomena that are highlighted and summarized in this review. The review is divided into the following four sections: (1) soil cracks as preferential pathways for water and contaminants; in this section lysimeter- to basin-scale observations that show the significance of cracks as preferential flow paths in vertisols which bypass matrix blocks in the unsaturated zone are summarized. Relatively fresh-water recharge and groundwater contamination from these fluxes and their modeling are reviewed, (2) soil cracks as deep evaporators and unsaturated-zone salinity; deep sediment samples under uncultivated vertisols in semiarid regions reveal a dry (immobile), saline matrix, partly due to enhanced evaporation through soil cracks. Observations of this phenomenon are compiled in this section and the mechanism of evapoconcentration due to air flow in the cracks is discussed, (3) impact of cultivation on flushing of the unsaturated zone and aquifer salinization; the third section examines studies reporting that land-use change of vertisols from native land to cropland promotes greater fluxes through the saline unsaturated-zone matrix, eventually flushing salts to the aquifer. Different degrees of salt flushing are assessed as well as aquifer salinization on different scales, and a comparison is made with aquifers under other soils, (4) relatively little nitrate contamination in aquifers under vertisols; In this section we turn the light on observations showing that aquifers under cultivated vertisols are somewhat resistant to groundwater contamination by nitrate (the major agriculturally related

  12. Soil-aquifer phenomena affecting groundwater under vertisols: a review

    NASA Astrophysics Data System (ADS)

    Kurtzman, D.; Baram, S.; Dahan, O.

    2016-01-01

    Vertisols are cracking clayey soils that (i) usually form in alluvial lowlands where, normally, groundwater pools into aquifers; (ii) have different types of voids (due to cracking), which make flow and transport of water, solutes and gas complex; and (iii) are regarded as fertile soils in many areas. The combination of these characteristics results in the unique soil-aquifer phenomena that are highlighted and summarized in this review. The review is divided into the following four sections: (1) soil cracks as preferential pathways for water and contaminants: in this section lysimeter-to basin-scale observations that show the significance of cracks as preferential-flow paths in vertisols, which bypass matrix blocks in the unsaturated zone, are summarized. Relatively fresh-water recharge and groundwater contamination from these fluxes and their modeling are reviewed; (2) soil cracks as deep evaporators and unsaturated-zone salinity: deep sediment samples under uncultivated vertisols in semiarid regions reveal a dry (immobile), saline matrix, partly due to enhanced evaporation through soil cracks. Observations of this phenomenon are compiled in this section and the mechanism of evapoconcentration due to air flow in the cracks is discussed; (3) impact of cultivation on flushing of the unsaturated zone and aquifer salinization: the third section examines studies reporting that land-use change of vertisols from native land to cropland promotes greater fluxes through the saline unsaturated-zone matrix, eventually flushing salts to the aquifer. Different degrees of salt flushing are assessed as well as aquifer salinization on different scales, and a comparison is made with aquifers under other soils; (4) relatively little nitrate contamination in aquifers under vertisols: in this section we turn the light on observations showing that aquifers under cultivated vertisols are somewhat resistant to groundwater contamination by nitrate (the major agriculturally related

  13. Using Groundwater Temperatures and Heat Flow Patterns to Assess Groundwater Flow in Snake Valley, Nevada and Utah, USA

    NASA Astrophysics Data System (ADS)

    Masbruch, M. D.; Chapman, D. S.

    2009-12-01

    The Southern Nevada Water Authority’s (SNWA) proposal to develop groundwater resources in Snake Valley and adjacent basins in eastern Nevada has focused attention on understanding the links between basin-fill and carbonate aquifer systems, groundwater flow paths, and the movement of groundwater between basins. The SNWA development plans are contentious in part because (1) there are few perennial streams that flow into the basins and these surface-water resources are fully appropriated; (2) groundwater resources that sustain streams, springs, wetlands, and the local agricultural economy are also limited; and (3) because Snake Valley straddles the Utah-Nevada state line. We report groundwater temperatures and estimates of heat flow used to constrain estimates of groundwater flow into and through Snake Valley. Thermal logs have been collected from 24 monitoring wells in the Utah part of the valley. Natural, undisturbed geothermal gradients within the Basin and Range are generally 30 °C/km, which correspond to heat flow values of approximately 90 mW/m2. Geothermal gradients in the southern portion of Snake Valley are lower than typical Basin and Range geothermal gradients, with the majority ranging between 10 and 20 °C/km, corresponding to heat flow values of 30 to 60 mW/m2. In the northern portion of the basin, however, geothermal gradients are generally higher than typical Basin and Range geothermal gradients, with thermal logs of two wells indicating gradients of 39 °C/km and 51 °C/km, which correspond to heat flow values of approximately 117 and 153 mW/m2, respectively. These observations suggest heat is being redistributed by groundwater flow to discharge points in northern Snake Valley. This interpretation is also supported by spring temperatures in northern Snake Valley and at Fish Springs National Wildlife Refuge to the northeast that are higher than ambient (12 °C) surface temperature. These thermal data are being used together with water levels and

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

    USGS Publications Warehouse

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

    1991-01-01

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

  15. Numerical error in groundwater flow and solute transport simulation

    NASA Astrophysics Data System (ADS)

    Woods, Juliette A.; Teubner, Michael D.; Simmons, Craig T.; Narayan, Kumar A.

    2003-06-01

    Models of groundwater flow and solute transport may be affected by numerical error, leading to quantitative and qualitative changes in behavior. In this paper we compare and combine three methods of assessing the extent of numerical error: grid refinement, mathematical analysis, and benchmark test problems. In particular, we assess the popular solute transport code SUTRA [Voss, 1984] as being a typical finite element code. Our numerical analysis suggests that SUTRA incorporates a numerical dispersion error and that its mass-lumped numerical scheme increases the numerical error. This is confirmed using a Gaussian test problem. A modified SUTRA code, in which the numerical dispersion is calculated and subtracted, produces better results. The much more challenging Elder problem [Elder, 1967; Voss and Souza, 1987] is then considered. Calculation of its numerical dispersion coefficients and numerical stability show that the Elder problem is prone to error. We confirm that Elder problem results are extremely sensitive to the simulation method used.

  16. 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.

  17. Factors affecting ground-water exchange and catchment size for Florida lakes in mantled karst terrain

    USGS Publications Warehouse

    Lee, Terrie Mackin

    2002-01-01

    In the mantled karst terrain of Florida, the size of the catchment delivering ground-water inflow to lakes is often considerably smaller than the topographically defined drainage basin. The size is determined by a balance of factors that act individually to enhance or diminish the hydraulic connection between the lake and the adjacent surficial aquifer, as well as the hydraulic connection between the surficial aquifer and the deeper limestone aquifer. Factors affecting ground-water exchange and the size of the ground-water catchment for lakes in mantled karst terrain were examined by: (1) reviewing the physical and hydrogeological characteristics of 14 Florida lake basins with available ground-water inflow estimates, and (2) simulating ground-water flow in hypothetical lake basins. Variably-saturated flow modeling was used to simulate a range of physical and hydrogeologic factors observed at the 14 lake basins. These factors included: recharge rate to the surficial aquifer, thickness of the unsaturated zone, size of the topographically defined basin, depth of the lake, thickness of the surficial aquifer, hydraulic conductivity of the geologic units, the location and size of karst subsidence features beneath and onshore of the lake, and the head in the Upper Floridan aquifer. Catchment size and the magnitude of ground-water inflow increased with increases in recharge rate to the surficial aquifer, the size of the topographically defined basin, hydraulic conductivity in the surficial aquifer, the degree of confinement of the deeper Upper Floridan aquifer, and the head in the Upper Floridan aquifer. The catchment size and magnitude of ground-water inflow increased with decreases in the number and size of karst subsidence features in the basin, and the thickness of the unsaturated zone near the lake. Model results, although qualitative, provided insights into: (1) the types of lake basins in mantled karst terrain that have the potential to generate small and large

  18. Groundwater flow and its effect on salt dissolution in Gypsum Canyon watershed, Paradox Basin, southeast Utah, USA

    NASA Astrophysics Data System (ADS)

    Reitman, Nadine G.; Ge, Shemin; Mueller, Karl

    2014-09-01

    Groundwater flow is an important control on subsurface evaporite (salt) dissolution. Salt dissolution can drive faulting and associated subsidence on the land surface and increase salinity in groundwater. This study aims to understand the groundwater flow system of Gypsum Canyon watershed in the Paradox Basin, Utah, USA, and whether or not groundwater-driven dissolution affects surface deformation. The work characterizes the groundwater flow and solute transport systems of the watershed using a three-dimensional (3D) finite element flow and transport model, SUTRA. Spring samples were analyzed for stable isotopes of water and total dissolved solids. Spring water and hydraulic conductivity data provide constraints for model parameters. Model results indicate that regional groundwater flow is to the northwest towards the Colorado River, and shallow flow systems are influenced by topography. The low permeability obtained from laboratory tests is inconsistent with field observed discharges, supporting the notion that fracture permeability plays a significant role in controlling groundwater flow. Model output implies that groundwater-driven dissolution is small on average, and cannot account for volume changes in the evaporite deposits that could cause surface deformation, but it is speculated that dissolution may be highly localized and/or weaken evaporite deposits, and could lead to surface deformation over time.

  19. Numerical simulations of groundwater flow at New Jersey Shallow Shelf

    NASA Astrophysics Data System (ADS)

    Fehr, Annick; Patterson, Fabian; Lofi, Johanna; Reiche, Sönke

    2016-04-01

    During IODP Expedition 313, three boreholes were drilled in the so-called New Jersey transect. Hydrochemical studies revealed the groundwater situation as more complex than expected, characterized by several sharp boundaries between fresh and saline groundwater. Two conflicting hypotheses regarding the nature of these freshwater reservoirs are currently debated. One hypothesis is that these reservoirs are connected with onshore aquifers and continuously recharged by seaward-flowing groundwater. The second hypothesis is that fresh groundwater was emplaced during the last glacial period. In addition to the petrophysical properties measured during IODP 313 expedition, Nuclear Magnetic Resonance (NMR) measurements were performed on samples from boreholes M0027, M0028 and M0029 in order to deduce porosities and permeabilities. These results are compared with data from alternative laboratory measurements and with petrophysical properties inferred from downhole logging data. We incorporate these results into a 2D numerical model that reflects the shelf architecture as known from drillings and seismic data to perform submarine groundwater flow simulations. In order to account for uncertainties related to the spatial distribution of physical properties, such as porosity and permeability, systematic variation of input parameters was performed during simulation runs. The target is to test the two conflicting hypotheses of fresh groundwater emplacements offshore New Jersey and to improve the understanding of fluid flow processes at marine passive margins.

  20. Effects of ground-water chemistry and flow on quality of drainflow in the western San Joaquin Valley, California

    USGS Publications Warehouse

    Fio, John L.; Leighton, David A.

    1994-01-01

    Chemical and geohydrologic data were used to assess the effects of regional ground-water flow on the quality of on-farm drainflows in a part of the western San Joaquin Valley, California. Shallow ground water beneath farm fields has been enriched in stable isotopes and salts by partial evaporation from the shallow water table and is being displaced by irrigation, drainage, and regional ground-water flow. Ground-water flow is primarily downward in the study area but can flow upward in some down- slope areas. Transitional areas exist between the downward and upward flow zones, where ground water can move substantial horizontal distances (0.3 to 3.6 kilometers) and can require 10 to 90 years to reach the downslope drainage systems. Simulation of ground-water flow to drainage systems indicates that regional ground water contributes to about 11 percent of annual drainflow. Selenium concentrations in ground water and drainwater are affected by geologic source materials, partial evaporation from a shallow water table, drainage-system, and regional ground-water flow. Temporal variability in drainflow quality is affected in part by the distribution of chemical constituents in ground water and the flow paths to the drainage systems. The mass flux of selenium in drainflows, or load, generally is proportional to flow, and reductions in drainflow quantity should reduce selenium loads over the short-term. Uncertain changes in the distribution of ground-water quality make future changes in drainflow quality difficult to quantify.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Nearly 2 billion people use groundwater and in Canada it is the potable water supply for about 30% of the population. Groundwater is also used in industrial and agricultural applications, and contributes to important hydrological habitats for various species. Limited research has been conducted to determine the potential impacts of climate change on groundwater. Local studies are crucial to better understand how, for example, increased duration and frequency of storms or drought periods may affect groundwater dependent ecosystems in order to anticipate and mitigate the impacts. Thus, the aim of this research is to explore the effects of climate change on a groundwater-surface water interacting system that supports a fragile ecosystem. This research is used to inform ecological conservation measures. The research site is the 17500 ha Covey Hill Natural Laboratory, which is located on the Quebec, Canada and New York State, USA border in the Chateauguay River watershed. At various locations within the Natural Laboratory there is continuous monitoring of groundwater levels and river flows. Covey Hill is an important recharge zone for the regional aquifer and provides habitat for endangered salamanders in discharge zones. Two hydrogeological models were constructed to represent flow at the site. First, a three-dimensional, finite difference model was developed using MODFLOW software to simulate overall groundwater flow at the research site. Second, a smaller-scale, discrete fracture, transient, three-dimensional, finite difference, integrated model was developed using HydroGeoSphere software to represent in better detail flow from bedrock springs that occur at mid-slope and provide the habitat for endangered salamanders. The models were used to: 1) observe groundwater flow under current climate conditions; 2) quantify water dynamics in response to climate change using 10 scenarios from the Canadian Regional Climate Model (for 1971-2000 and 2041-2070 time periods); and 3

  2. 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.

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

    SciTech Connect

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

    2006-05-16

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  5. An initial examination of tungsten geochemistry along groundwater flow paths

    NASA Astrophysics Data System (ADS)

    Dave, H. B.; Johannesson, K. H.

    2008-12-01

    Groundwater samples were collected along groundwater flow paths from the Upper Floridan (Florida), Carrizo Sand (Texas), and the Aquia (Maryland) aquifers and analyzed for tungsten (W) concentrations by high- resolution inductively couple plasma mass spectrometry. At each well head, groundwater samples were also analyzed for pH, specific conductance, temperature, alkalinity, dissolved oxygen (DO), oxidation-reduction potential (Eh), dissolved iron speciation, and dissolved sulfide [S(-II)] concentrations. Sediment samples from the Carrizo Sand and Aquia aquifers were also collected and subjected to sequential extractions to provide additional insights into the solid-phase speciation of W in these aquifers. Tungsten concentrations varied along the groundwater flow paths chiefly in response to changing pH, and to a lesser extent, variations in the redox conditions. For groundwater from the Carrizo Sand aquifer, W ranges between 3.64 and 1297 pmol/kg, exhibiting the lowest values proximal to the recharge zone. Tungsten concentrations progressively increase along the flow path, reaching 1297 pmol/kg in the sulfidic groundwaters located approximately 60 km downgradient from the recharge area. Tungsten is strongly correlated with S(-II) concentrations and pH in Carrizo groundwaters (r = 0.95 and 0.78, respectively). Within the Aquia aquifer, however, W generally occurs at lower concentrations than the Carrizo (14 to 184 pmol/kg; mean = 80 pmol/kg), and shows no systematic trends along the flow path (e.g., r = 0.08 and 0.4 for W vs. S(-II) and pH, respectively). Our data are consistent with the increase in W concentrations in Carrizo groundwaters reflecting, in part, pH-related desorption, which has been shown to be substantial for pH greater than 8. Moreover, because of the broad similarities in the chemistry of W and Mo, which forms thiomolybdates in sulfidic waters, we suggest that thiotungstate complexes may form in sulfidic groundwaters, thus partially explaining the

  6. 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.

  7. 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

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

    NASA Astrophysics Data System (ADS)

    Kohara, N.; Marui, A.

    2011-12-01

    / fresh water interface (position of the submarine groundwater discharge) may appear on the seafloor. Moreover, neither the salinity concentration nor the groundwater age depends on depth. It is thought that it is because that the groundwater forms the complex flow situation through the change in a long-term groundwater flow system. The technology to understand the coastal groundwater flow consists of remote sensing, geographical features analysis, surface of the earth investigation, geophysical exploration, drilling survey, and indoor examination and the measurement. Integration of each technology is needed to interpret groundwater flow system because the one is to catch the local groundwater flow in the time series and another one is to catch the long-term and regional groundwater flow in the general situation. The purpose of this study is to review the previous research of coastal groundwater flow, and to integrate an applicable evaluation approach to understand this mechanism. In this presentation, the review of the research and case study using numerical simulation are introduced.

  9. An initial inverse calibration of the ground-water flow model for the Hanford unconfined aquifer

    SciTech Connect

    Jacobson, E.A. . Desert Research Inst.); Freshly, M.D. )

    1990-03-01

    Large volumes of process cooling water are discharged to the ground form U.S. Department of Energy (DOE) nuclear fuel processing operations in the central portion of the Hanford Site in southeastern Washington. Over the years, these large volumes of waste water have recharged the unconfined aquifer at the Site. This artificial recharge has affected ground-water levels and contaminant movement in the unconfined aquifer. Ground-water flow and contaminant transport models have been applied to assess the impacts of site operations on the rate and direction of ground-water flow and contaminant transport in unconfined aquifer at the Hanford Site. The inverse calibration method developed by Neuman and modified by Jacobson was applied to improve calibration of a ground-water flow model of the unconfined aquifer at the Hanford Site. All information about estimates of hydraulic properties of the aquifer, hydraulic heads, boundary conditions, and discharges to and withdrawals form the aquifer is included in the inverse method to obtain an initial calibration of the ground-water flow model. The purpose of this report is to provide a description of the inverse method, its initial application to the unconfined aquifer at Hanford, and to present results of the initial inverse calibration. 28 refs., 19 figs., 1 tab.

  10. Consistency of groundwater flow patterns in mountainous topography: Implications for valley bottom water replenishment and for defining groundwater flow boundaries

    NASA Astrophysics Data System (ADS)

    Welch, L. A.; Allen, D. M.

    2012-05-01

    Topographic influences on groundwater flow processes that contribute to baseflow and mountain block recharge (MBR) are conceptually investigated using three-dimensional numerical models of saturated groundwater flow. Model domains for conceptual and real topographies are developed as "mountain groundwatershed units" (MGUs) to represent regional-scale watershed systems. Results indicate regularity in groundwater flow patterns that reflect consistency of prominent topographic features, providing a basis for conceptualizing three-dimensional groundwater flow. Baseflow is generated mainly from recharge within the watershed area. MBR is produced primarily from recharge that is focused across triangular facets near the mountain front (˜73%-97% of total MBR), with additional contributions originating within the watershed (up to ˜27% of MBR). MBR contributions originating from recharge near the highest-elevation watershed boundaries are minimal but are greater for topography with less stream incision. With orographic influences, more MBR originates within the watershed. MBR rates are relatively consistent between models because of similarities in mountain front topography, while baseflow is variable. Gains and losses to systems via cross-watershed groundwater flux, generated because of topographic differences between adjacent watersheds, cause baseflow to vary by up to ˜10% but do not significantly influence MBR. In data-sparse regions such as mountains, a basic numerical modeling approach, using the MGU concept with topography data and mapped watershed boundaries, can be used to develop site-specific conceptual models to constrain water budgets, to delineate recharge areas, and to guide further investigation and data collection.

  11. 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.

  12. Detecting groundwater flow direction from infrared thermal images

    NASA Astrophysics Data System (ADS)

    Ahmad, Akhundzadah Noor; Saito, Hirotaka; Asada, Kei; Kato, Makoto

    In this study we propose an approach to directly measure temperature changes around the heat source placed in a borehole using an infrared camera for determining groundwater flow direction. A plastic box filled with sands with a cylindrical perforated column placed in middle of the box was used in lab experiments. A heater was inserted in the center of the borehole. To detect the flow direction from the temperature distribution, an infrared camera that was placed face-down at the top of the cylinder (i.e., borehole) was used. COMSOL was used to numerically simulate coupled water flow and heat transfer to evaluate experimental results. Results show that when the flux is in the order of 10-2 to 10-4cm s-1, we can determine the groundwater flow direction because of a skewed temperature distribution due to convective transport of heat.

  13. Perturbation of ground surface temperature reconstructions by groundwater flow?

    NASA Astrophysics Data System (ADS)

    Ferguson, Grant; Beltrami, Hugo; Woodbury, Allan D.

    2006-07-01

    Subsurface temperatures have been shown to be a robust source of information on past climates. Most analyses neglect groundwater flow (GWF) and assume purely conductive heat flow. However, in many situations GWF has not been fully considered and to date there are no general GWF criteria for either accepting or rejecting a temperature profile for paleoclimate analysis. Here we examine the transition from conduction dominated environments to environments where advection has a significant effect on the subsurface temperature regime and thus ground surface temperature (GST) histories. We provide guidelines indicating when advection is important and conclude that it is unlikely that groundwater flow is a significant source of error in the global data set maintained by the International Heat Flow Commission.

  14. 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.

  15. Estimation of the pore pressure distribution from three dimensional groundwater flow model at mine sites in Korea

    NASA Astrophysics Data System (ADS)

    Kang, Sangsoo; Jang, Myounghwan; Kim, Gyoungman; Kim, Donghui; Kim, Daehoon; Baek, Hwanjo

    2016-04-01

    Mining activities continually change the groundwater flow and associated pore pressure distributions within the rockmass around the mine openings or the open-pit bench during the operational periods. As the pore pressure distributions may substantially affect the mechanical behaviour or stability of the rockmass, it is important to monitor the variation of pore pressure incurred by mining operation. The pore pressure distributions within the rockmass can be derived using a two- or three-dimensional finite element groundwater flow model, adopted to simulate the groundwater flow. While the groundwater inflow at mines has generally been dealt with respect to the working environment, detailed case studies on the distribution of pore water pressure related to the stability analysis of mine openings have been relatively rare in Korea. Recently, however, as the health and safety problems are emerged for sustainable mining practice, these issues are of the major concerns for the mining industries. This study aims to establish a three dimensional groundwater flow model to estimate the pore pressure distributions in order to employ as an input parameter for numerical codes such as the FLAC 3D. Also, the groundwater flow simulated can be used for de-watering design at a mine site. The MINEDW code, a groundwater flow model code specifically developed to simulate the complicated hydro-geologic conditions related to mining, has mainly been used in this study. Based on the data collected from field surveys and literature reviews, a conceptual model was established and sensitivity analysis was performed.

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

    NASA Astrophysics Data System (ADS)

    Spanoudaki, Katerina; Kampanis, Nikolaos A.

    2014-05-01

    Coastal areas are the most densely-populated areas in the world. Consequently water demand is high, posing great pressure on fresh water resources. Climatic change and its direct impacts on meteorological variables (e.g. precipitation) and indirect impact on sea level rise, as well as anthropogenic pressures (e.g. groundwater abstraction), are strong drivers causing groundwater salinisation and subsequently affecting coastal wetlands salinity with adverse effects on the corresponding ecosystems. Coastal zones are a difficult hydrologic environment to represent with a mathematical model due to the large number of contributing hydrologic processes and variable-density flow conditions. Simulation of sea level rise and tidal effects on aquifer salinisation and accurate prediction of interactions between coastal waters, groundwater and neighbouring wetlands requires the use of integrated surface water-groundwater models. In the past few decades several computer codes have been developed to simulate coupled surface and groundwater flow. In these numerical models surface water flow is usually described by the 1-D Saint Venant equations (e.g. Swain and Wexler, 1996) or the 2D shallow water equations (e.g. Liang et al., 2007). Further simplified equations, such as the diffusion and kinematic wave approximations to the Saint Venant equations, are also employed for the description of 2D overland flow and 1D stream flow (e.g. Gunduz and Aral, 2005). However, for coastal bays, estuaries and wetlands it is often desirable to solve the 3D shallow water equations to simulate surface water flow. This is the case e.g. for wind-driven flows or density-stratified flows. Furthermore, most integrated models are based on the assumption of constant fluid density and therefore their applicability to coastal regions is questionable. Thus, most of the existing codes are not well-suited to represent surface water-groundwater interactions in coastal areas. To this end, the 3D integrated

  17. Simulation of groundwater flow around a pilot waste tire site

    SciTech Connect

    Lin, Y.; Chyi, L.L. . Dept. of Geology)

    1994-04-01

    The groundwater system in the area contains several aquifers divided by underclays as confining layers. The three aquifers addressed under this research include the upper aquifer above the No. 6 underclay, the middle aquifer above the No. 5 underclay and the lower aquifer above the No. 4 underclay. A quasi-3D conceptual model is used in simulating groundwater flow and MODFLOW is used for the actual modeling. The boundary of the model area is defined by a local divide on the north, the Hugle Run on the west and the Temple Ditch on the east and the Sandy Creek on the south. The model consists of three aquifer layers and two confining layers. The upper one is unconfined, the middle one is a hybrid, and the lower one is confined. In the simulation of the upper aquifer, drain boundary condition is defined to include seepage. In the simulation of the middle aquifer, the Hugle Run and the Temple ditch associated with the alluvium represent a drain boundary and the Sand Creek to the south represents a constant head. The lower aquifer does not have a natural hydrogeologic boundary. The equipotential contours are assigned as constant head boundary. Simulation has indicated that minimal groundwater flow existed in the upper aquifer and it is flowing toward the southwest. Groundwater flow in the middle aquifer near the pilot waste site is somewhat divergent to the south. The velocity is slow near the site but increases quickly toward the southwest. Leakage from the upper aquifer appears to be predominant over the regional flow in the recharge of the middle aquifer. The lower aquifer is recharged mainly by the regional flow and is flowing almost due south.

  18. The transition of flow patterns through critical stagnation points in two-dimensional groundwater flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A flow pattern is characterized by aquifer features and the number, type, and distribution of stagnation points (locations where the discharge is zero). This article identifies a condition for transition of flow patterns in two-dimensional groundwater flow obeying Darcy's law by examining changes in...

  19. 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.

  20. Groundwater availability as constrained by hydrogeology and environmental flows

    USGS Publications Warehouse

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

    2014-01-01

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

  1. 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

    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., Seņņikovs, 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.

  2. Groundwater flow systems in mountainous terrain, 1. Numerical modeling technique

    NASA Astrophysics Data System (ADS)

    Forster, Craig; Smith, Leslie

    1988-07-01

    A coupled model of fluid flow and heat transfer is developed to characterize steady groundwater flow within a mountain massif. A coupled model is necessary because high-relief terrain can enhance groundwater flow to depths where elevated temperatures are encountered. A wide range in water table form and elevation expected in high-relief terrain is accommodated using a free-surface method. This approach allows us to examine the influence of thermal conditions on the patterns and rates of groundwater flow and the position of the water table. Vertical fluid flow is assumed to occur within the unsaturated zone to provide a simple basis for modeling advective heat transfer above the water table. This approach ensures that temperatures at the water table, and throughout the domain, are consistent with temperature conditions specified at the bedrock surface. Conventional free-surface methods provide poor estimates of the water table configuration in high-relief terrain. A modified free-surface approach is introduced to accommodate recharge at upper elevations on the seepage face, in addition to recharge at the free surface.

  3. Partitioning a regional groundwater flow system into shallow local and deep regional flow compartments

    NASA Astrophysics Data System (ADS)

    Goderniaux, Pascal; Davy, Philippe; Bresciani, Etienne; Dreuzy, Jean-Raynald; Borgne, Tanguy

    2013-04-01

    The distribution of groundwater fluxes in aquifers is strongly influenced by topography, and organized between hillslope and regional scales. The objective of this study is to provide new insights regarding the compartmentalization of aquifers at the regional scale and the partitioning of recharge between shallow/local and deep/regional groundwater transfers. A finite-difference flow model was implemented, and the flow structure was analyzed as a function of recharge (from 20 to 500 mm/yr), at the regional-scale (1400 km2), in three dimensions, and accounting for variable groundwater discharge zones; aspects which are usually not considered simultaneously in previous studies. The model allows visualizing 3-D circulations, as those provided by Tothian models in 2-D, and shows local and regional transfers, with 3-D effects. The probability density function of transit times clearly shows two different parts, interpreted using a two-compartment model, and related to regional groundwater transfers and local groundwater transfers. The role of recharge on the size and nature of the flow regimes, including groundwater pathways, transit time distributions, and volumes associated to the two compartments, have been investigated. Results show that topography control on the water table and groundwater compartmentalization varies with the recharge rate applied. When recharge decreases, the absolute value of flow associated to the regional compartment decreases, whereas its relative value increases. The volume associated to the regional compartment is calculated from the exponential part of the two-compartment model, and is nearly insensitive to the total recharge fluctuations.

  4. Simulation of ground-water flow and areas contributing ground water to production wells, Cadillac, Michigan

    USGS Publications Warehouse

    Hoard, Christopher J.; Westjohn, David B.

    2005-01-01

    Ground water is the primary source of water for domestic, municipal, and industrial use within the northwest section of Michigan's Lower Peninsula. Because of the importance of this resource, numerous communities including the city of Cadillac in Wexford County, Michigan, have begun local wellhead protection programs. In these programs, communities protect their ground-water resources by identifying the areas that contribute water to production wells, identifying potential sources of contamination, and developing methods to cooperatively manage and minimize threats to the water supply. The U.S. Geological Survey, in cooperation with the city of Cadillac, simulated regional ground-water flow and estimated areas contributing recharge and zones of transport to the production well field. Ground-water flow models for the Clam River watershed, in Wexford and Missaukee Counties, were developed using the U.S. Geological Survey modular three-dimensional finite-difference ground-water flow model (MODFLOW 2000). Ground-water flow models were calibrated using the observation, sensitivity, and parameter estimation packages of MODFLOW 2000. Ground-water-head solutions from calibrated flow models were used in conjunction with MODPATH, a particle-tracking program, to simulate regional ground-water flow and estimate areas contributing recharge and zones of transport to the Cadillac production-well field for a 10-year period. Model simulations match the conceptual model in that regional ground-water flow in the deep ground-water system is from southeast to northwest across the watershed. Areas contributing water were determined for the optimized parameter set and an alternate parameter set that included increased recharge and hydraulic conductivity values. Although substantially different hydrologic parameters (assumed to represent end-member ranges of realistic hydrologic parameters) were used in alternate numerical simulations, simulation results differ little in predictions of

  5. New understanding of the complexity of groundwater flow in Chalk catchments of the UK

    NASA Astrophysics Data System (ADS)

    Peach, D.; Shand, P.; Gooddy, D.; Abesser, C.; Bloomfield, J.; Mathias, S.; Butler, A.; Williams, A.; Binley, A.; Wheater, H.

    2006-12-01

    The Chalk is the largest aquifer in the UK accounting for more than half the groundwater used and nearly a quarter of the total public water supplied in England and Wales. Although the Chalk is a double porosity and permeability medium, transmission of water in the saturated zone depends largely on flow through fractures, the location and distribution of which are controlled by lithology and geological structure. These features operate on a number of spatial scales and so provide a range of flow pathways that can markedly affect both stream flow and water quality. In addition, overlying Palaeogene or superficial deposits can act as controls on recharge and zones of increased groundwater storage. As part of a major initiative on Lowland Catchment Research in the UK two Chalk sub-catchments, in the River Thames basin, the rivers Pang and Lambourn, have been the focus of an intensive set of studies. The catchments have been characterised using a multidisciplinary approach. This has resulted in an improved understanding of the way such catchments work and the mechanisms that control groundwater flow. The low fracture porosity gives rise to a low specific yield, which means that large fluctuations in water table elevation beneath the interfluves are not uncommon. Consequently, groundwater catchments differ from the topographic catchments and their size varies seasonally. This means, for example, that groundwater might be flowing to the River Pang in winter but to the River Thames in summer. It also means that various flow features in the catchment may be active at different locations and times during the year. Four flow systems have been identified, through a detailed analysis of the data; a shallow, but rapid flow system; a slower, deeper system; a very high velocity system developed in large diameter solution enhanced fractures and a system found in the river valley sediments. The interconnections between and within these systems can be poor and sometimes vary on a

  6. Concepts of Groundwater Occurrence and Flow Near Oak Ridge National Laboratory, Tennessee

    SciTech Connect

    Moore, G.K.

    1988-01-01

    Previous studies of the area near Oak Ridge National Laboratory (ORNL) assumed that nearly all groundwater from precipitation and infiltration moves vertically down to the water table and then follows a combination of intergranular and fracture flow paths to the streams. These studies also generally assumed nearly linear flow paths, amounts of groundwater flow that are determined by differences in water-level elevation, large permeability differences between regolith and bedrock, and important hydrologic differences between named geologic units. It has been commonly stated for 37 years, for example, that the Conasauga Group has fewer cavities and is less permeable than the Chickamauga Group. All of these assumptions and conclusions are faulty. The new concepts in this report may be controversial, but they explain the available data. Only the stormflow zone from land surface to a depth of 1-2 m has a permeability large enough to transport most groundwater to the streams. Calculations show that 90-95% of all groundwater flow is in the stormflow zone, 4-9% is in a few water-producing intervals below the water table, and about 1% occurs in other intervals. The available data also show that nearly all groundwater flows through enlarged openings such as macropores, fractures, and cavities, and that there are no significant differences between regolith and bedrock or between the Conasauga Group and the Chickamauga group. Flow paths apparently are much more complex than was previously assumed. Multiple paths connect any two points below the water table, and each flow path is more likely to be tortuous than linear. Hydraulic gradients are affected by this complexity and by changes in hydraulic potential on steep hillsides. Below the water table, a large difference in the head of two points generally does not indicate a large flow rate between these points. Groundwater storage in amounts above field capacity is apparently intergranular in only the stormflow and vadose zones

  7. 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.

  8. Flow partitioning in regional groundwater flow systems as a function of recharge and topography

    NASA Astrophysics Data System (ADS)

    Goderniaux, P.; Davy, P.; Bresciani, E.; De Dreuzy, J.; Le Borgne, T.

    2013-12-01

    The distribution of groundwater fluxes in aquifers is strongly influenced by topography, and organized between hillslope and regional scales. In this study, we use a finite-difference flow model to quantify the partitioning of recharge and compartmentalization of aquifers between shallow/local and deep/regional groundwater transfers. The flow structure is analyzed for a regional aquifers, as a function of recharge (from 20 to 500 mm/yr), in 3-dimensions, and accounting for variable groundwater discharge zones. The Probability Density Function of transit times shows two different parts, interpreted using a two-compartment model, related to regional and local groundwater flows. The role of recharge on the size and nature of the flow regimes, including groundwater pathways, transit time distributions, and volumes associated to the two compartments is investigated. Results show that topography control on the water table and groundwater compartmentalization varies with the recharge rate applied. The volume associated to the regional compartment is calculated from the exponential part of the two-compartment model, and is nearly insensitive to the total recharge fluctuations. The model also allows visualizing 3D circulations, as those provided by Tothian models in 2D, and shows local and regional transfers, with 3D effects. Results are presented for a specific basin (1400 km2) in Brittany (France). Preliminary results using different kinds of topography are presented and compared.

  9. ShowFlow: A practical interface for groundwater modeling

    SciTech Connect

    Tauxe, J.D.

    1990-12-01

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

  10. Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling

    NASA Astrophysics Data System (ADS)

    Sjöberg, Ylva; Coon, Ethan; Sannel, A. Britta K.; Pannetier, Romain; Harp, Dylan; Frampton, Andrew; Painter, Scott L.; Lyon, Steve W.

    2016-03-01

    Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this study we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels were observed in boreholes. These observations were used to set up one- and two-dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. As sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.

  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

  12. Groundwater--Baseflow interactions of a shallow fracture flow system: Childress Creek basin, central Texas

    SciTech Connect

    Mann, J.F. . Geology Dept.)

    1993-02-01

    The Georgetown Formation in central Texas crops out west of the major urban growth along Interstate Highway 35. The Georgetown Formation, comprised of interbedded limestone and calcareous shale, is not recognized as a major aquifer. However, numerous shallow wells occur in these bedrock units and shallow groundwater is directly connected to surface streams. A large percentage of cities throughout central Texas are dependent upon surface water for their primary water supply. Recent investigations revealed shallow flow systems along bedding plane separations and fractures associated with weathering, release of overburden, neotectonic movements and the Balcones Fault Zone. Many pollutants which can affect this source are conveyed through the groundwater system and return to the streams as baseflow. Therefore a better understanding of surface-groundwater relations is needed to aid in understanding the potential for impacts in the watershed. Data obtained from monitoring baseflow, groundwater levels, and rainfall is being used to investigate recharge, shallow fracture flow systems, transmissivity in the watershed, baseflow recession, and groundwater levels. This information will help determine regional aquifer characteristics, modeling flow paths, and water budgets in watersheds having highly fractured unconfined aquifers such as those found in the Washita Prairie. As a result coefficients of storage, transmissivity, and scale simulation model will yield a regional water budget. This study provided a detailed analysis of the relationship between groundwater levels and stream baseflow in Childress Creek. These same methods may in turn be applied to watersheds in areas of increased urban development and used in watershed models for analysis of regional impacts related to landuse changes and pollution loads.

  13. Groundwater flow system and Nitrogen cycle in volcanic aquifer of pyroclastic flow uplands, Japan

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Study area is well-known agriculture area in Southern Kyushu, Japan and highly depends on groundwater resources for their everyday use. Local unconfined groundwater aquifer is widely polluted by Nitrate-Nitrogen originated from agriculture and cattle farming. It will become serious problem if this unconfined Nitrate pollution enlarges into the confined aquifer system which is used for local city water source. The detailed three dimensional groundwater flow system study has been done by using existing wells in the basin to understand the three dimensional distribution pattern of Nitrate-Nitrogen in the aquifer. However, the detailed groundwater age analysis by using Tritium for unconfined and confined groundwater has not been succeeded because of present low atmosphere tritium concentration. Thus we applied to challenge the CFCs dating method. Although the CFCs method has been widely used for dating the young groundwater instead of tritium in many countries, in Japan CFCs has been used only by Oceanographic study and has not been used in the field of Hydrology. The history and fate of Nitrate contamination have been shown in multidisciplinary local transect studies in areas with agricultural sources (Bohlke and Denver 1995). However, identification of Nitrogen sources can be difficult in larger regional studies because of co-occurrence of multiple anthropogenic Nitrogen sources and uncertainty in Nitrogen transformation pathways. Thus, the characterization of N geochemistry remains challenging, particularly in aquifer-scale assessments (Stephen 2006). In this study, the evidence of the shallow groundwater flowing towards deep aquifer was verified by the groundwater dating and the detailed Nitrogen reduction process was confirmed along the groundwater flow.

  14. 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.

  15. Elevated atmospheric carbon dioxide in agroecosystems affects groundwater quality

    SciTech Connect

    Torbert, H.A.; Prior, S.A.; Rogers, H.H.; Schlesinger, W.H.; Mullins, G.L.; Runion, G.B.

    1996-07-01

    Increasing atmospheric carbon dioxide (CO{sub 2}) concentration has led to concerns about global changes to the environment. One area of global change that has not been addressed is the effect of elevated atmospheric CO{sub 2} on groundwater quality below agroecosystems. Elevated CO{sub 2} concentration alterations of plant growth and C/N ratios may modify C and N cycling in soil and affect nitrate (NO{sub 3}{sup {minus}}) leaching to groundwater. This study was conducted to examine the effects of a legume (soybean [Glycine max (L.) Merr.]) and a nonlegume (grain sorghum [Sorghum bicolor (L.) Moench]) CO{sub 2}-enriched agroecosystems on NO{sub 3}{sup {minus}} movement below the root zone in a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study was a split-plot design replicated three times with plant species (soybean and grain sorghum) as the main plots and CO{sub 2} concentration ({approximately}360 and {approximately}720 {mu}L L{sup {minus}1} CO{sub 2}) as subplots using open-top field chambers. Fertilizer application was made with {sup 15}N-depleted NH{sub 4}NO{sub 3} to act as a fertilizer tracer. Soil solution samples were collected weekly at 90-cm depth for a 2-yr period and monitored for NO{sub 3}{sup {minus}}-N concentrations. Isotope analysis of soil solution indicated that the decomposition of organic matter was the primary source of No{sub 3}{sup {minus}}-N in soil solution below the root zone through most of the monitoring period. Significant differences were observed for NO{sub 3}{sup {minus}}-N concentrations between soybean and grain sorghum, with soybean having the higher NO{sub 3}{sup {minus}}-N concentration. Elevated CO{sub 2} increased total dry weight, total N content, and C/N ratio of residue returned to soil in both years. Elevated CO{sub 2} significantly decreased NO{sub 3}{sup {minus}}-N concentrations below the root zone in both soybean and grain sorghum. 37 refs., 2 figs., 2 tabs.

  16. On the mechanism of earthquake induced groundwater flow

    NASA Astrophysics Data System (ADS)

    Dudley Ward, Nicholas F.

    2015-11-01

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

  17. Predicting groundwater flow system discharge in the river network at the watershed scale

    NASA Astrophysics Data System (ADS)

    Caruso, Alice; Ridolfi, Luca; Boano, Fulvio

    2016-04-01

    The interaction between rivers and aquifers affects the quality and the quantity of surface and subsurface water since it plays a crucial role for solute transport, nutrient cycling and microbial transformations. The groundwater-surface water interface, better known as hyporheic zone, has a functional significance for the biogeochemical and ecological conditions of the fluvial ecosystem since it controls the flux of groundwater solutes discharging into rivers, and vice versa. The hyporheic processes are affected by the complex surrounding aquifer because the groundwater flow system obstructs the penetration of stream water into the sediments. The impact of large-scale stream-aquifer interactions on small scale exchange has generally been analyzed at local scales of a river reach, or even smaller. However, a complete comprehension of how hyporheic fluxes are affected by the groundwater system at watershed scale is still missing. Evaluating this influence is fundamental to predict the consequences of hyporheic exchange on water quality and stream ecology. In order to better understand the actual structure of hyporheic exchange along the river network, we firstly examine the role of basin topography complexity in controlling river-aquifer interactions. To reach this target, we focus on the analysis of surface-subsurface water exchange at the watershed scale, taking into account the river-aquifer interactions induced by landscape topography. By way of a mathematical model, we aim to improve the estimation of the role of large scale hydraulic gradients on hyporheic exchange. The potential of the method is demonstrated by the analysis of a benchmark case's study, which shows how the topographic conformation influences the stream-aquifer interaction and induces a substantial spatial variability of the groundwater discharge even among adjacent reaches along the stream. The vertical exchange velocity along the river evidences a lack of autocorrelation. Both the groundwater

  18. Tide-induced fingering flow during submarine groundwater discharge

    NASA Astrophysics Data System (ADS)

    Greskowiak, Janek

    2013-04-01

    Submarine groundwater discharge (SGD) is a relevant component of the hydrological cycle (Moore, 2010). The discharge of fresh groundwater that originated from precipitation on the land typically occurs at the near shore scale (~ 10m-100m) and the embayment scale (~ 100m - 10km) (Bratton, 2010). In the recent years a number of studies revealed that tidal forcing has an important effect on the fresh SGD pattern in the beach zone, i.e., it leads to the formation of an upper saline recirculation cell and a lower "freshwater discharge tube" (Boufadel, 2000, Robinson et al., 2007; Kuan et al., 2012). Thereby the discharge of the fresh groundwater occurs near the low-tide mark. The shape and extent of the upper saline recirculation cell is mainly defined by the tidal amplitude, beach slope, fresh groundwater discharge rate and hydraulic conductivity (Robinson et al., 2007). In spite of fact that in this case sea water overlies less denser freshwater, all previous modeling studies suggested that the saline recirculation cell and the freshwater tube are rather stable. However, new numerical investigations indicate that there maybe realistic cases where the upper saline recirculation cell becomes unstable as a result of the density contrast to the underlying freshwater tube. In these cases salt water fingers develop and move downward, thereby penetrating the freshwater tube. To the author's knowledge, the present study is the first that illustrate the possibility of density induced fingering flow during near shore SGD. A total of 240 high resolution simulations with the density dependent groundwater modelling software SEAWAT-2000 (Langevin et al., 2007) has been carried out to identify the conditions under which salt water fingering starts to occur. The simulations are based on the field-scale model setup employed in Robinson et al. (2007). The simulation results indicate that a very flat beach slope of less than 1:35, a hydraulic conductivity of 10 m/d and already a tidal

  19. Deterministic modelling of the cumulative impacts of underground structures on urban groundwater flow and the definition of a potential state of urban groundwater flow: example of Lyon, France

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Underground structures have been shown to have a great influence on subsoil resources in urban aquifers. A methodology to assess the actual and the potential state of the groundwater flow in an urban area is proposed. The study develops a three-dimensional modeling approach to understand the cumulative impacts of underground infrastructures on urban groundwater flow, using a case in the city of Lyon (France). All known underground structures were integrated in the numerical model. Several simulations were run: the actual state of groundwater flow, the potential state of groundwater flow (without underground structures), an intermediate state (without impervious structures), and a transient simulation of the actual state of groundwater flow. The results show that underground structures fragment groundwater flow systems leading to a modification of the aquifer regime. For the case studied, the flow systems are shown to be stable over time with a transient simulation. Structures with drainage systems are shown to have a major impact on flow systems. The barrier effect of impervious structures was negligible because of the small hydraulic gradient of the area. The study demonstrates that the definition of a potential urban groundwater flow and the depiction of urban flow systems, which involves understanding the impact of underground structures, are important issues with respect to urban underground planning.

  20. Deterministic modelling of the cumulative impacts of underground structures on urban groundwater flow and the definition of a potential state of urban groundwater flow: example of Lyon, France

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    Underground structures have been shown to have a great influence on subsoil resources in urban aquifers. A methodology to assess the actual and the potential state of the groundwater flow in an urban area is proposed. The study develops a three-dimensional modeling approach to understand the cumulative impacts of underground infrastructures on urban groundwater flow, using a case in the city of Lyon (France). All known underground structures were integrated in the numerical model. Several simulations were run: the actual state of groundwater flow, the potential state of groundwater flow (without underground structures), an intermediate state (without impervious structures), and a transient simulation of the actual state of groundwater flow. The results show that underground structures fragment groundwater flow systems leading to a modification of the aquifer regime. For the case studied, the flow systems are shown to be stable over time with a transient simulation. Structures with drainage systems are shown to have a major impact on flow systems. The barrier effect of impervious structures was negligible because of the small hydraulic gradient of the area. The study demonstrates that the definition of a potential urban groundwater flow and the depiction of urban flow systems, which involves understanding the impact of underground structures, are important issues with respect to urban underground planning.

  1. Ground-water levels, predevelopment ground-water flow, and stream-aquifer relations in the vicinity of the Savannah River Site, Georgia and South Carolina

    USGS Publications Warehouse

    Clarke, John S.; West, Christopher T.

    1998-01-01

    Ground-water levels, predevelopment ground-water flow, and stream-aquifer relations in the vicinity of the U.S. Department of Energy Savannah River Site, Georgia and South Carolina, were evaluated as part of a cooperative study between the U.S. Geological Survey, U.S. Department of Energy, and Georgia Department of Natural Resources. As part of this evaluation: (1) ground-water-level fluctuations and trends in three aquifer systems in sediment of Cretaceous and Tertiary age were described and related to patterns of ground-water use and precipitations; (2) a conceptual model ofthe stream-aquifer flow system was developed; (3) the predevelopment ground-water flow system, configuration of potentiometric surfaces, trans-river flow, and recharge-discharge relations were described; and (4) stream-aquifer relations and the influence of river incision on ground-water flow and stream-aquifer relations were described. The 5,147-square mile study area is located in the northern part of the Coastal Plain physiographic province of Georgia and South Carolina. Coastal Plain sediments comprise three aquifer systems consisting of seven aquifers that are separated hydraulically by confining units. The aquifer systems are, in descending order: (1) the Floridan aquifer system?consisting of the Upper Three Runs and Gordon aquifers in sediments of Eocene age; (2) the Dublin aquifer system?consisting of the Millers Pond, upper Dublin, and lower Dublin aquifers in sediments of Paleocene-Late Cretaceous age; and (3) the Midville aquifer system?consisting of the upper Midville and lower Midville aquifers in sediments of Late Cretaceous age. The Upper Three Runs aquifer is the shallowest aquifer and is unconfined to semi-confined throughout most of the study area. Ground-water levels in the Upper Three Runs aquifer respond to a local flow system and are affected mostly by topography and climate. Ground-water flow in the deeper, Gordon aquifer and Dublin and Midville aquifer systems is

  2. 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

    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.

  3. Spatial geochemical and isotopic characteristics associated with groundwater flow in the North China Plain

    NASA Astrophysics Data System (ADS)

    Chen, Jianyao; Tang, Changyuan; Sakura, Yasuo; Kondoh, Akihiko; Yu, Jingjie; Shimada, Jun; Tanaka, Tadashi

    2004-11-01

    The North China Plain (NCP) is an important agricultural area in China and has a high population density. Serious water shortages have occurred in this region over the last 20 years. Water transfer from the Yangtze River (the east route) was initiated in the year 2002 to provide water for the major cities of the NCP. This study was carried out before the implementation of the water transfer project, focusing on the spatial integration of the groundwater flow system and geochemical characteristics, which are mainly controlled by tectonics, geomorphology, and lithology. The field survey and the geochemical analyses of the groundwater samples indicated that the groundwater in the NCP has a two-layer structure, with a boundary at a depth of about 100-150 m. The two layers differ in pH, concentrations of SiO2 and major ions, and isotopes (18O, deuterium and tritium (T)). Chemical components in the upper layer showed a wider range and higher variability than those in the lower layer, indicating the impact of human activity. The flow direction of the groundwater in the upper layer was examined in detail in two profiles, showing that the upper layer flows east towards the Cangzhou-Daming fault, while the groundwater in the lower layer flows northeast towards Tianjin. Three hydrogeological zones are identified: recharge (Zone I), intermediate (Zone II), and discharge (Zone III). The recharge zone was found to be low in chloride (Cl-) but high in T. The discharge zone was found to be high in Cl- and low in T. This may be due to the difference in groundwater age. The discharge zone was subdivided into two sub-zones, Zone III1 and Zone III2, by considering the effects of human activities. Zone III2 was strongly affected by water diversions from the Yellow River. As groundwater flows from the recharge zone to the intermediate and discharge zones, chemical patterns evolve in the order: Ca-HCO3 > Mg-HCO3 > Na-Cl + SO4.

  4. 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

  5. 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

  6. Evaluation of groundwater flow patterns around a dual-screened groundwater circulation well.

    PubMed

    Johnson, Richard L; Simon, Michelle A

    2007-08-15

    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 flow of this circulation cell are difficult to measure or predict. The objective of this study is to develop a robust protocol for assessing GCW performance. To accomplish this, groundwater flow patterns surrounding a GCW are assessed using a suite of tools and data, including: hydraulic head, in situ flow velocity, measured hydraulic conductivity data from core samples, chemical tracer tests, contaminant distribution data, and numerical flow and transport models. The hydraulic head data show patterns that are consistent with pumping on a dual-screened well, however, many of the observed changes are smaller than expected. In situ thermal perturbation flow sensors successfully measured horizontal flow, but vertical flow could not be determined with sufficient accuracy to be useful in mapping flow patterns. Two types of chemical tracer tests were utilized at the site and showed that much of the flow occurs within a few meters of the GCW. Flow patterns were also assessed based on changes in contaminant (trichloroethylene, TCE) concentrations over time. The TCE data clearly showed treated water moving away from the GCW at shallow and intermediate depths, but the circulation of that water back to the well, except very close to the well, was less clear. Detailed vertical and horizontal hydraulic conductivities were measured on 0.3 m-long sections from a continuous core from the GCW installation borehole. The measured vertical and horizontal hydraulic conductivity data were used to construct numerical flow and transport models, the results of which were compared to the head, velocity and concentration data. Taken together, the field data and modeling present a fairly consistent picture of flow

  7. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

    USGS Publications Warehouse

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

    2015-01-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  8. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

    SciTech Connect

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

    2015-02-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  9. 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

  10. Groundwater Parameters and Flow Systems Near Oak Ridge National Laboratory

    SciTech Connect

    Moore, G.K.

    1989-01-01

    Precipitation near Oak Ridge National Laboratory (ORNL) averages 132 cm/yr. About 76 cm/yr of water is consumed by evapotranspiration. The natural streamflow, which averages 56 cm/yr of water, consists of overland flow (about 21 cm/yr) from water bodies, wetlands, and impervious areas of groundwater discharge (about 35 cm/yr of water). Groundwater occurs in a stormflow zone that extends from the land surface to a depth of 0.3-2 m and in shallow and deeper aquifers that extend from the water table to the base of fresh water. in the stormflow zone, most water flows through macropores and mesopores, which have a volumetric porosity of about 0.002. In the vadose zone and below the water table, water flows through fractures that have a volumetric porosity in the range 1 x 10{sup -5} to 0.02. Water inflow occurs by precipitation and infiltration. infiltration that exceeds the soil water deficit forms a perched water table in the stormflow zone at the level where infiltration rate exceeds vertical hydraulic conductivity. Some water percolates down to the water table but the majority flows downslope to the streams. Recharge of the shallow aquifer is only about 3.2 cm/yr of water or 5.7% of streamflow. Most of the water that recharges the shallow aquifer is discharged by evapotranspiration above the water table. The remainder is discharged at springs and streams where the water table is within the stormflow zone. Digital models that permit unsaturated conditions and transient flows may be more appropriate than steady-state models of saturated flow for the ORNL area.

  11. Groundwater Flow Model of the General Separations Area Using PORFLOW

    SciTech Connect

    FLACH, GREGORY

    2004-07-15

    The E Area PA (McDowell-Boyer et al. 2000) includes a steady-state simulation of groundwater flow in the General Separations Area as a prerequisite for saturated zone contaminant transport analyses. The groundwater flow simulations are based on the FACT code (Hamm and Aleman2000). The FACT-based GSA model was selected during preparation of the original PA to take advantage of an existing model developed for environmental restoration applications at the SRS (Flach and Harris 1997, 1999; Flach 1999). The existing GSA/FACT model was then slightly modified for PA use, as described in the PA document. FACT is a finite-element code utilizing deformed brick elements. Material properties are defined at element centers, and state variables such as hydraulic head are located at element vertices. The PORFLOW code (Analytic and Computational Research, Inc. 2000) was selected for performing saturated zone transport simulations of source zone radionuclides and their progeny. PORFLOW utilizes control volume discretization and the nodal point integration method, with all properties and state variables being defined at the center of an interior grid cell. The groundwater flow calculation includes translating the Darcy velocity field computed by FACT into a form compatible for input to PORFLOW. The FACT velocity field is defined at element vertices, whereas PORFLOW requires flux across cell faces. For the present PA, PORFLOW cell face flux is computed in a two-step process. An initial face flux is computed from FACT as an average of the normal components of Darcy velocity at the four corners. The derived flux field approximately conserves mass, but not rigorously. Thus, the flux field is subsequently perturbed to force rigorous mass conservation on a cell-by-cell basis. The undocumented process used is non-unique and can introduce significant artifacts into the final flux field.

  12. Effects of Hysteresis on Groundwater Recharge From Ephemeral Flows

    NASA Astrophysics Data System (ADS)

    Parissopoulos, G. A.; Wheater, H. S.

    1992-11-01

    The effects of hysteresis on the movement of the saturated and unsaturated soil water phase due to infiltration from ephemeral surface water flows are investigated for different scenarios of flood events in homogeneous and heterogeneous media with the use of a two-dimensional model based on Richards' equation and the dependent domain hysteresis model of Mualem (1984). Hysteresis effects were found in general to be small, but sensitive to water ponding depth, hydraulic contact between surface and groundwater and initial moisture distribution. In all cases tested, hysteresis resulted in higher rise of the toe of the water mound formed beneath the wadi despite a decrease of cumulative infiltration.

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

    NASA Astrophysics Data System (ADS)

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

    1989-04-01

    Geological, hydrological, isotope (tritium and 18O) and chemical (mainly nitrate and chloride concentrations) evidence is interpreted to give a mutually consistent picture of the recharge sources and flow patterns of the important groundwater resource in the deep glacial and interglacial deposits of the sector of the Canterbury Plains between the Selwyn River and Ashley River. Particular attention is paid to the confined gravel aquifers which presently provide about 300,000 m 3 daily of mainly very high-quality water for the needs of Christchurch city. The study period for tritium measurements extends over 27 years, encompassing the peak and decline of thermonuclear tritium fallout in this region. Major rivers emerging from the hill and mountain catchments to the west of the Plains are depleted in 18O relative to average low-level precipitation. Most of the groundwater is river-recharged, but some areas of significant local precipitation recharge contribution are clearly identified by 18O and chemical concentrations. The pressure distribution, tritium and chemical data reveal that the artesian ground-water underlying Christchurch ascends from deeper aquifers into the shallowest aquifer via gaps in the confining layers; much of this flow is induced by withdrawal, and the data reveal nothing about possible offshore discharge through the seaward extension of the shallowest aquifer, which is known to outcrop 40 km beyond the coast. The Christchurch aquifers are recharged by infiltration from Waimakariri River in its central Plains reaches, and the resulting flow regime is east- and southeast-directed; satisfactory water quality of the deeper Christchurch aquifers appears to be guaranteed for the future provided the river can be maintained in its present condition. Shallow groundwater, and water recharged to depth by other rivers, irrigation and local precipitation on the unconfined western areas of the Plains, are more susceptible to agricultural and other pollutants

  14. 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.

  15. Influence of vertical flows in wells on groundwater sampling.

    PubMed

    McMillan, Lindsay A; Rivett, Michael O; Tellam, John H; Dumble, Peter; Sharp, Helen

    2014-11-15

    Pumped groundwater sampling evaluations often assume that horizontal head gradients predominate and the sample comprises an average of water quality variation over the well screen interval weighted towards contributing zones of higher hydraulic conductivity (a permeability-weighted sample). However, the pumping rate used during sampling may not always be sufficient to overcome vertical flows in wells driven by ambient vertical head gradients. Such flows are reported in wells with screens between 3 and 10m in length where lower pumping rates are more likely to be used during sampling. Here, numerical flow and particle transport modeling is used to provide insight into the origin of samples under ambient vertical head gradients and under a range of pumping rates. When vertical gradients are present, sample provenance is sensitive to pump intake position, pumping rate and pumping duration. The sample may not be drawn from the whole screen interval even with extended pumping times. Sample bias is present even when the ambient vertical flow in the wellbore is less than the pumping rate. Knowledge of the maximum ambient vertical flow in the well does, however, allow estimation of the pumping rate that will yield a permeability-weighted sample. This rate may be much greater than that recommended for low-flow sampling. In practice at monitored sites, the sampling bias introduced by ambient vertical flows in wells may often be unrecognized or underestimated when drawing conclusions from sampling results. It follows that care should be taken in the interpretation of sampling data if supporting flow investigations have not been undertaken. PMID:24999176

  16. 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.

  17. Delineation of groundwater flow paths using hydrochemical and strontium isotope composition: A case study in high arsenic aquifer systems of the Datong basin, northern China

    NASA Astrophysics Data System (ADS)

    Xie, Xianjun; Wang, Yanxin; Ellis, Andre; Su, Chunli; Li, Junxia; Li, Mengdi; Duan, Mengyu

    2013-01-01

    SummaryStrontium isotopic compositions and major ion chemistry were used to delineate flow paths in an arsenic affected groundwater flow system in the Datong basin, China. Total of 28 samples including one spring and one river water were collected for major ions and strontium isotopic compositions and concentration analysis. The ion ratios indicate that dissolution of silicates and carbonates is the dominant geochemical process controlling the hydrochemistry of groundwater from two recharge areas at the basin margins, while the water chemistry in the center of the basin is affected by the dissolution of evaporites (including gypsum and halite). Groundwater from eastern and western margin areas have relatively high 87Sr/86Sr values ranging from 0.72114 to 0.72604 and from 0.71119 to 0.71151, which are consistent with expected values for groundwater dominantly affected by dissolution of silicates. However, in the discharge area, the groundwater samples had lower 87Sr/86Sr values and varied between 0.71016 and 0.71753. The contour map of δ87Sr in groundwater shows the general tendency of decrease from the western and eastern margin areas to the discharge area. The plot of 87Sr/86Sr vs. Sr/Na indicates that interactions between Quaternary aquifer sediment and groundwater in the recharge areas along the flow paths control the hydrochemistry and strontium isotopic compositions of groundwater. By contrast, groundwater samples from the discharge area are plotted on the mixing line, indicating that mixing of groundwater from recharge area with low 87Sr/86Sr values groundwater could be the controlling factor on their hydrochemistry and strontium isotopic compositions. Four main flow paths of groundwater were inferred from hydrochemical and isotopic data. The results of PHREEQC inverse modeling matched quite well with the results of strontium isotopic and ion compositions along the flow paths. The distribution of high arsenic groundwater in this area could be attributed to

  18. STRING 3: An Advanced Groundwater Flow Visualization Tool

    NASA Astrophysics Data System (ADS)

    Schröder, Simon; Michel, Isabel; Biedert, Tim; Gräfe, Marius; Seidel, Torsten; König, Christoph

    2016-04-01

    The visualization of 3D groundwater flow is a challenging task. Previous versions of our software STRING [1] solely focused on intuitive visualization of complex flow scenarios for non-professional audiences. STRING, developed by Fraunhofer ITWM (Kaiserslautern, Germany) and delta h Ingenieurgesellschaft mbH (Witten, Germany), provides the necessary means for visualization of both 2D and 3D data on planar and curved surfaces. In this contribution we discuss how to extend this approach to a full 3D tool and its challenges in continuation of Michel et al. [2]. This elevates STRING from a post-production to an exploration tool for experts. In STRING moving pathlets provide an intuition of velocity and direction of both steady-state and transient flows. The visualization concept is based on the Lagrangian view of the flow. To capture every detail of the flow an advanced method for intelligent, time-dependent seeding is used building on the Finite Pointset Method (FPM) developed by Fraunhofer ITWM. Lifting our visualization approach from 2D into 3D provides many new challenges. With the implementation of a seeding strategy for 3D one of the major problems has already been solved (see Schröder et al. [3]). As pathlets only provide an overview of the velocity field other means are required for the visualization of additional flow properties. We suggest the use of Direct Volume Rendering and isosurfaces for scalar features. In this regard we were able to develop an efficient approach for combining the rendering through raytracing of the volume and regular OpenGL geometries. This is achieved through the use of Depth Peeling or A-Buffers for the rendering of transparent geometries. Animation of pathlets requires a strict boundary of the simulation domain. Hence, STRING needs to extract the boundary, even from unstructured data, if it is not provided. In 3D we additionally need a good visualization of the boundary itself. For this the silhouette based on the angle of

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

    SciTech Connect

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

    2001-11-09

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

  20. Adaptive multiresolution modeling of groundwater flow in heterogeneous porous media

    NASA Astrophysics Data System (ADS)

    Malenica, Luka; Gotovac, Hrvoje; Srzic, Veljko; Andric, Ivo

    2016-04-01

    different temporal lines and local time stepping control. Critical aspect of time integration accuracy is construction of spatial stencil due to accurate calculation of spatial derivatives. Since common approach applied for wavelets and splines uses a finite difference operator, we developed here collocation one including solution values and differential operator. In this way, new improved algorithm is adaptive in space and time enabling accurate solution for groundwater flow problems, especially in highly heterogeneous porous media with large lnK variances and different correlation length scales. In addition, differences between collocation and finite volume approaches are discussed. Finally, results show application of methodology to the groundwater flow problems in highly heterogeneous confined and unconfined aquifers.

  1. Scaling of flow and transport behavior in heterogeneous groundwater systems

    NASA Astrophysics Data System (ADS)

    Scheibe, Timothy; Yabusaki, Steven

    1998-11-01

    Three-dimensional numerical simulations using a detailed synthetic hydraulic conductivity field developed from geological considerations provide insight into the scaling of subsurface flow and transport processes. Flow and advective transport in the highly resolved heterogeneous field were modeled using massively parallel computers, providing a realistic baseline for evaluation of the impacts of parameter scaling. Upscaling of hydraulic conductivity was performed at a variety of scales using a flexible power law averaging technique. A series of tests were performed to determine the effects of varying the scaling exponent on a number of metrics of flow and transport behavior. Flow and transport simulation on high-performance computers and three-dimensional scientific visualization combine to form a powerful tool for gaining insight into the behavior of complex heterogeneous systems. Many quantitative groundwater models utilize upscaled hydraulic conductivity parameters, either implicitly or explicitly. These parameters are designed to reproduce the bulk flow characteristics at the grid or field scale while not requiring detailed quantification of local-scale conductivity variations. An example from applied groundwater modeling is the common practice of calibrating grid-scale model hydraulic conductivity or transmissivity parameters so as to approximate observed hydraulic head and boundary flux values. Such parameterizations, perhaps with a bulk dispersivity imposed, are then sometimes used to predict transport of reactive or non-reactive solutes. However, this work demonstrates that those parameters that lead to the best upscaling for hydraulic conductivity and head do not necessarily correspond to the best upscaling for prediction of a variety of transport behaviors. This result reflects the fact that transport is strongly impacted by the existence and connectedness of extreme-valued hydraulic conductivities, in contrast to bulk flow which depends more strongly on

  2. 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.

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

    USGS Publications Warehouse

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

    2016-01-01

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

  4. Groundwater.

    ERIC Educational Resources Information Center

    Braids, Olin C.; Gillies, Nola P.

    1978-01-01

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

  5. 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

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

    EPA Science Inventory

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

  7. Ground-water flow in the Coastal Plain aquifers of South Carolina.

    USGS Publications Warehouse

    Aucott, W.R.; Speiran, G.K.

    1985-01-01

    The Coastal Plain aquifers are recharged primarily by precipitation in their outcrop areas. Groundwater flows from these areas of recharge, through the aquifers, and discharges to upper Costal Plain rivers, overlying aquifers as upward leakage, and wells. Ground-water flow in the Floridan aquifer system and the Tertiary sand aquifer prior to development is generally perpendicular to the coast.-from Authors

  8. 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)

  9. Biogeochemical factors affecting the presence of 210Po in groundwater

    USGS Publications Warehouse

    Seiler, R.L.; Stillings, L.L.; Cutler, N.; Salonen, L.; Outola, I.

    2011-01-01

    The discovery of natural 210Po enrichment at levels exceeding 500 mBq/L in numerous domestic wells in northern Nevada, USA, led to a geochemical investigation of the processes responsible for its mobilization. 210Po activities in 63 domestic and public-supply wells ranged from below 1 mBq/L to 6590 ± 590 mBq/L, among the highest reported levels in the USA. There is little spatial or depth variability in 210Pb activity in study-area sediments and mobilization of a few percent of the 210Po in the sediments would account for all of the 210Po in water. Stable-isotope measurements indicate SO4 reduction has occurred in all 210Po contaminated wells. Sulfide species are not accumulating in the groundwater in much of Lahontan Valley, probably because of S cycling involving microbial SO4 reduction, abiotic oxidation of H2S to S0 by Mn(IV), followed by microbial disproportionation of S0 to H2S and SO4. The high pH, Ca depletion, MnCO3 saturation, and presence of S0 in Lahontan Valley groundwater may be consequences of the anaerobic S cycling. Consistent with data from naturally-enriched wells in Florida, 210Po activities begin to decrease when aqueous sulfide species begin to accumulate. This may be due to formation and precipitation of PoS, however, Eh–pH diagrams suggest PoS would not be stable in study-area groundwater. An alternative explanation for the study area is that H2S accumulation begins when anaerobic S cycling stops because Mn oxides are depleted and their reduction is no longer releasing 210Po. Common features of 210Po-enriched groundwater were identified by comparing the radiological and geochemical data from Nevada with data from naturally-enriched wells in Finland, and Florida and Maryland in the USA. Values of pH ranged from 9 in Nevada wells, indicating that pH is not critical in determining whether 210Po is present. Where U is present in the sediments, the data suggest 210Po levels may be elevated in aquifers with (1) SO4-reducing waters with low H2S

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Qiao, L.

    2010-12-01

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

  13. A numerical approach for groundwater flow in unsaturated porous media

    NASA Astrophysics Data System (ADS)

    Quintana, F.; Guarracino, L.; Saliba, R.

    2006-07-01

    In this article, a computational tool to simulate groundwater flow in variably saturated non-deformable fractured porous media is presented, which includes a conceptual model to obtain analytical expressions of water retention and hydraulic conductivity curves for fractured hard rocks and a numerical algorithm to solve the Richards equation. To calculate effective saturation and relative hydraulic conductivity curves we adopt the Brooks-Corey model assuming fractal laws for both aperture and number of fractures. A standard Galerkin formulation was employed to solve the Richards' equation together with a Crank-Nicholson scheme with Richardson extrapolation for the time discretization.The main contribution of this paper is to group an analytical model of the authors with a robust numerical algorithm designed to solve adequately the highly non-linear Richards' equation generating a tool for porous media engineering.

  14. 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.

  15. Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling

    DOE PAGESBeta

    Sjöberg, Ylva; Coon, Ethan; K. Sannel, A. Britta; Pannetier, Romain; Harp, Dylan; Frampton, Andrew; Painter, Scott L.; Lyon, Steve W.

    2016-02-05

    Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this paper, we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels weremore » observed in boreholes. These observations were used to set up one- and two-dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. Finally, as sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.« less

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    Groundwater chemistry and isotopic data from 40 production wells in the Atemajac and Toluquilla valleys, located in and around the Guadalajara metropolitan area, were determined to develop a conceptual model of groundwater flow processes and mixing. Stable water isotopes (δ2H, δ18O) were used to trace hydrological processes and tritium (3H) to evaluate the relative contribution of modern water in samples. Multivariate analysis including cluster analysis and principal component analysis were used to elucidate distribution patterns of constituents and factors controlling groundwater chemistry. Based on this analysis, groundwater was classified into four groups: cold groundwater, hydrothermal groundwater, polluted groundwater and mixed groundwater. Cold groundwater is characterized by low temperature, salinity, and Cl and Na concentrations and is predominantly of Na-HCO3-type. It originates as recharge at "La Primavera" caldera and is found predominantly in wells in the upper Atemajac Valley. Hydrothermal groundwater is characterized by high salinity, temperature, Cl, Na and HCO3, and the presence of minor elements such as Li, Mn and F. It is a mixed-HCO3 type found in wells from Toluquilla Valley and represents regional flow circulation through basaltic and andesitic rocks. Polluted groundwater is characterized by elevated nitrate and sulfate concentrations and is usually derived from urban water cycling and subordinately from agricultural return flow. Mixed groundwaters between cold and hydrothermal components are predominantly found in the lower Atemajac Valley. Twenty-seven groundwater samples contain at least a small fraction of modern water. The application of a multivariate mixing model allowed the mixing proportions of hydrothermal fluids, polluted waters and cold groundwater in sampled water to be evaluated. This study will help local water authorities to identify and dimension groundwater contamination, and act accordingly. It may be broadly applicable to

  17. Relation of streams, lakes, and wetlands to groundwater flow systems

    NASA Astrophysics Data System (ADS)

    Winter, Thomas C.

    Surface-water bodies are integral parts of groundwater flow systems. Groundwater interacts with surface water in nearly all landscapes, ranging from small streams, lakes, and wetlands in headwater areas to major river valleys and seacoasts. Although it generally is assumed that topographically high areas are groundwater recharge areas and topographically low areas are groundwater discharge areas, this is true primarily for regional flow systems. The superposition of local flow systems associated with surface-water bodies on this regional framework results in complex interactions between groundwater and surface water in all landscapes, regardless of regional topographic position. Hydrologic processes associated with the surface-water bodies themselves, such as seasonally high surface-water levels and evaporation and transpiration of groundwater from around the perimeter of surface-water bodies, are a major cause of the complex and seasonally dynamic groundwater flow fields associated with surface water. These processes have been documented at research sites in glacial, dune, coastal, mantled karst, and riverine terrains. Résumé Les eaux de surface sont parties intégrantes des systèmes aquifères. Les eaux souterraines interagissent avec les eaux de surface dans presque tous les types d'environnements, depuis les petits ruisseaux, les lacs et les zones humides jusqu'aux bassins versants des vallées des grands fleuves et aux lignes de côte. Il est en général admis que les zones topographiquement hautes sont des lieux de recharge des aquifères et les zones basses des lieux de décharge, ce qui est le cas des grands systèmes aquifères régionaux. La superposition de systèmes locaux, associés à des eaux de surface, à l'organisation régionale d'écoulements souterrains résulte d'interactions complexes entre les eaux souterraines et les eaux de surface dans tous les environnements, quelle que soit la situation topographique régionale. Les processus

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

    ERIC Educational Resources Information Center

    Ousey, John Russell, Jr.

    1986-01-01

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

  19. Field identification of groundwater flow systems and hydraulic traps in drainage basins using a geophysical method

    NASA Astrophysics Data System (ADS)

    Jiang, Xiao-Wei; Wan, Li; Wang, Jun-Zhi; Yin, Bin-Xi; Fu, Wen-Xiang; Lin, Chang-Hong

    2014-04-01

    Groundwater flow systems and stagnant zones in drainage basins are critical to a series of geologic processes. Unfortunately, the difficulty of mapping flow system boundaries and no field example of detected stagnant zones restrict the application of the concept of nested flow systems. By assuming the variation in bulk resistivity of an aquifer with uniform porosity is mainly caused by groundwater salinity, the magnetotelluric technique is used to obtain the apparent resistivity of a profile across a groundwater-fed river in the Ordos Plateau, China. Based on the variations in apparent resistivity of the Cretaceous sandstone aquifer, the basin-bottom hydraulic trap below the river has been detected for the first time, and its size is found to be large enough for possible deposition of large ore bodies. The boundaries between local and regional flows have also been identified, which would be useful for groundwater exploration and calibration of large-scale groundwater models.

  20. 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.

  1. Hydrologic data and groundwater-flow simulations in the Brown Ditch Watershed, Indiana Dunes National Lakeshore, near Beverly Shores and Town of Pines, Indiana

    USGS Publications Warehouse

    Lampe, David C.

    2016-01-01

    The results of this study can be used by water-resource managers to understand how surrounding ditches affect water levels in Great Marsh and other inland wetlands and residential areas. The groundwater model developed can be applied to answer questions about how alterations to the drainage system in the area affects water levels in the public and residential areas surrounding Great Marsh. The modeling methods developed in this study provide a template for other studies of groundwater flow and groundwater/surface-water interactions within the shallow surficial aquifer in northern Indiana, and in similar hydrologic settings that include surficial sand aquifers in coastal areas.

  2. Hydrogeologic setting and simulation of groundwater flow near the Canterbury and Leadville Mine Drainage Tunnels, Leadville, Colorado

    USGS Publications Warehouse

    Wellman, Tristan P.; Paschke, Suzanne S.; Minsley, Burke; Dupree, Jean A.

    2011-01-01

    -current resistivity field survey was performed to evaluate the geologic structure of the study area. The results show that the Canterbury Tunnel is located in a downthrown structural block that is not in direct physical connection with the Leadville Mine Drainage Tunnel. The presence of this structural discontinuity implies there is no direct groundwater pathway between the tunnels along a laterally continuous bedrock unit. Water-quality results for pH and major-ion concentrations near the Canterbury Tunnel showed that acid mine drainage has not affected groundwater quality. Stable-isotope ratios of hydrogen and oxygen in water indicate that snowmelt is the primary source of groundwater recharge. On the basis of chlorofluorocarbon and tritium concentrations and mixing ratios for groundwater samples, young groundwater (groundwater recharged after 1953) was indicated at well locations upgradient from and in a fault block separate from the Canterbury Tunnel. Samples from sites downgradient from the Canterbury Tunnel were mixtures of young and old (pre-1953) groundwater and likely represent snowmelt recharge mixed with older regional groundwater that discharges from the bedrock units to the Arkansas River valley. Discharge from the Canterbury Tunnel contained the greatest percentage of old (pre-1953) groundwater with a mixture of about 25 percent young water and about 75 percent old water. A calibrated three-dimensional groundwater model representing high-flow conditions was used to evaluate large-scale flow characteristics of the groundwater and to assess whether a substantial hydraulic connection was present between the Canterbury Tunnel and Leadville Mine Drainage Tunnel. As simulated, the faults restrict local flow in many areas, but the fracture-damage zones adjacent to the faults allow groundwater to move along faults. Water-budget results indicate that groundwater flow across the lateral edges of the model controlled the majority of flow in and out of the aquifer (79 percent and

  3. Ground-water flow and simulated effects of development in Paradise Valley, a basin tributary to the Humboldt River in Humboldt County, Nevada

    USGS Publications Warehouse

    Prudic, D.E.; Herman, M.E.

    1996-01-01

    A computer model was used to characterize ground-water flow in Paradise Valley, Nevada, and to evaluate probable long-term effects of five hypothetical development scenarios. One finding of the study is that concentrating pumping at the south end of Paradise Valley may increase underflow from the adjacent Humboldt River valley, and might affect flow in the river.

  4. Exploring Online Game Players' Flow Experiences and Positive Affect

    ERIC Educational Resources Information Center

    Chiang, Yu-Tzu; Lin, Sunny S. J.; Cheng, Chao-Yang; Liu, Eric Zhi-Feng

    2011-01-01

    The authors conducted two studies to explore online game players' flow experiences and positive affect. Our findings indicated that online game are capable of evoking flow experiences and positive affect, and games of violent or nonviolent type may not arouse players' aggression. The players could be placed into four flow conditions: flow,…

  5. Wellbore and groundwater temperature distribution eastern Snake River Plain, Idaho: Implications for groundwater flow and geothermal potential

    NASA Astrophysics Data System (ADS)

    McLing, Travis L.; Smith, Richard P.; Smith, Robert W.; Blackwell, David D.; Roback, Robert C.; Sondrup, Andrus J.

    2016-06-01

    A map of groundwater temperatures from the Eastern Snake River Plain (ESRP) regional aquifer can be used to identify and interpret important features of the aquifer, including aquifer flow direction, aquifer thickness, and potential geothermal anomalies. The ESRP is an area of high heat flow, yet most of this thermal energy fails to reach the surface, due to the heat being swept downgradient by the aquifer to the major spring complexes near Thousand Springs, ID, a distance of 300 km. Nine deep boreholes that fully penetrate the regional aquifer display three common features: (1) high thermal gradients beneath the aquifer, corresponding to high conductive heat flow in low-permeability hydrothermally-altered rocks; (2) isothermal temperature profiles within the aquifer, characteristic of an actively flowing groundwater; and (3) moderate thermal gradients in the vadose zone with values that indicate that over half of the geothermal heat flow is removed by advective transport in the regional aquifer system. This study utilized temperature data from 250 ESRP aquifer wells to evaluate regional aquifer flow direction, aquifer thickness, and potential geothermal anomalies. Because the thermal gradients are typically low in the aquifer, any measurement of groundwater temperature is a reasonable estimate of temperature throughout the aquifer thickness, allowing the construction of a regional aquifer temperature map for the ESRP. Mapped temperatures are used to identify cold thermal plumes associated with recharge from tributary valleys and adjacent uplands, and warm zones associated with geothermal input to the aquifer. Warm zones in the aquifer can have various causes, including local circulation of groundwater through the deep conductively dominated region, slow groundwater movement in low-permeability regions, or localized heat flow from deeper thermal features.

  6. Groundwater flow dynamics and arsenic source characterization in an aquifer system of West Bengal, India

    NASA Astrophysics Data System (ADS)

    Desbarats, A. J.; Koenig, C. E. M.; Pal, T.; Mukherjee, P. K.; Beckie, R. D.

    2014-06-01

    Numerical groundwater flow modeling, reverse particle tracking, and environmental tracers are used to locate the source of geogenic As affecting an aquifer in West Bengal. The aquifer is hosted by point-bar sands deposited in a meandering fluvial environment. Wells tapping the aquifer exhibit As concentrations up to 531 μg/L. High-As groundwaters are recharged in ponds marking an abandoned river channel. The source of As is traced to the underlying fine-grained channel-fill sediments. Arsenic release within these sediments is accompanied by a concomitant release of Br and DOC indicating that these species may be decay products of natural organobromines codeposited along with As. Mass transfer of As to the dissolved phase and its flushing from source sediments are described using a simplified reactive solute transport model. Based on this model, a characteristic reaction time for mass transfer is estimated at 6.7 years. Average groundwater residence times in the source are estimated to have declined from 16.6 to 6.6 years with the advent of intensive irrigation pumping. The ratio of residence and reaction times, a Damköhler number, has declined correspondingly from 2.49 to 0.99, indicating a shift from transport to reaction rate limited As mobilization. Greater insight into the As problem in SE Asia may be achieved by shifting the focus of field investigations from aquifers to potential contamination sources in aquitards.

  7. Numerical Groundwater Flow Modeling of the Arsenic Contaminated Gotra Aquifer, West Bengal, India

    NASA Astrophysics Data System (ADS)

    Koenig, C. E.; Desbarats, A. J.; Beckie, R. D.; Pal, T.; Mukherjee, P. K.

    2009-12-01

    We present results of a groundwater flow study in a 7 square kilometer region centered on our field site in the village of Gotra, West Bengal, India, where naturally occurring arsenic contaminates shallow groundwater (mostly < 40 m below surface) at levels that exceed World Health Organization limits. Field investigations since 2004 include sediment coring, geochemical surveys of domestic wells and dedicated piezometers, and monitoring of piezometric levels with dataloggers in several wells over a period of three years. The village itself is situated upon the natural levee of a sinuous abandoned channel, which terminates a classical fluvio-deltaic depositional sequence originating from the north east. The formerly prograding meander bend deposited point bar sands that now comprise the 25-30m-thick shallow aquifer, while incising a deeper sand unit as well as a floodplain sequence to the south west. Hand-pumped domestic tubewells are restricted to the point bar sands, whereas the majority of irrigation wells are screened within the deeper aquifer. Both steady-state and transient simulations were used to estimate aquifer recharge and boundary fluxes, as well as to distinguish groundwater flow paths and average residence times under the influence of irrigation and seasonal stresses. The hydrogeology of the deeper aquifer, as well as the thickness and continuity of the low permeable paleosol separating shallow and deep flow systems are major uncertainties that are explored through model sensitivity testing. Recharge to the shallow flow system is estimated at ~170mm/yr, predominantly by monsoon precipitation. Groundwater in the arsenic affected area generally flows downward through the fine-grained channel-fill deposits, then horizontally through the point bar sands perpendicular to the trend of the abandoned channel. This flowpath coincides with observed geochemical gradients from surveys of domestic well quality conducted in previous years, and supports a model of

  8. Effect of irrigation return flow on groundwater recharge in an overexploited aquifer in Bangladesh

    NASA Astrophysics Data System (ADS)

    Touhidul Mustafa, Syed Md.; Shamsudduha, Mohammad; Huysmans, Marijke

    2016-04-01

    Irrigated agriculture has an important role in the food production to ensure food security of Bangladesh that is home to over 150 million people. However, overexploitation of groundwater for irrigation, particularly during the dry season, causes groundwater-level decline in areas where abstraction is high and surface geology inhibits direct recharge to underlying shallow aquifer. This is causing a number of potential adverse socio-economic, hydrogeological, and environmental problems in Bangladesh. Alluvial aquifers are primarily recharged during monsoon season from rainfall and surface sources. However, return flow from groundwater-fed irrigation can recharge during the dry months. Quantification of the effect of return flow from irrigation in the groundwater system is currently unclear but thought to be important to ensure sustainable management of the overexploited aquifer. The objective of the study is to investigate the effect of irrigation return flow on groundwater recharge in the north-western part of Bangladesh, also known as Barind Tract. A semi-physically based distributed water balance model (WetSpass-M) is used to simulate spatially distributed monthly groundwater recharge. Results show that, groundwater abstraction for irrigation in the study area has increased steadily over the last 29 years. During the monsoon season, local precipitation is the controlling factor of groundwater recharge; however, there is no trend in groundwater recharge during that period. During the dry season, however, irrigation return-flow plays a major role in recharging the aquifer in the irrigated area compared to local precipitation. Therefore, during the dry season, mean seasonal groundwater recharge has increased and almost doubled over the last 29 years as a result of increased abstraction for irrigation. The increase in groundwater recharge during dry season has however no significant effect in the improvement of groundwater levels. The relation between groundwater

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

    PubMed

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

    2015-01-01

    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

  10. Groundwater Flow in the Arthur Marble Aquifer, New Zealand

    NASA Astrophysics Data System (ADS)

    Stewart, M. K.

    2008-05-01

    Arthur Marble underlies the Takaka Valley and outcrops in Karst Uplands to east and west of the valley in the South Island of New Zealand. It is the principal groundwater aquifer in the region and host to the remarkable Waikoropupu Springs near the coast. With average flow of 13,300 L/s, the karstic springs have many interesting features including unusual size and clarity. This work uses rainfall and river level, natural tracer and chemical measurements to determine the recharge sources and nature of the flow system in the Arthur Marble Aquifer (AMA). Total recharge to the AMA of 19,750 L/s comes from three sources (Karst Uplands stream seepage, Takaka River seepage and Takaka Valley rainfall infiltration). Since 13,300 L/s is discharged at the springs, the remainder must escape via offshore springs (6,450 L/s). The oxygen-18 mass balance allows the contribution of each source to each spring to be determined; most of the flow to the Main Spring of the Waikoropupu Springs comes from the Karst Uplands. The offshore springs are mostly fed from the Takaka River. The chemical concentrations of the Main Spring show input of 0.5% of sea water on average, but varying with flow. This variation with flow shows that two water components (sea-water-bearing and non-sea-water-bearing) contribute to the spring's discharge. Tritium measurements spanning 40 years, and CFC-11 measurements, give a mean residence time of 8 years for the Main Spring water using the preferred two-component model. Our conceptual flow model, based on the flow, oxygen-18, chloride and tritium measurements, reveals that two different flow systems with different recharge sources are needed to explain the flow within the AMA. One system contains deeply penetrating old water with mean age 10.2 years and water volume 3 cubic kilometers, recharged from the Karst Uplands. The other, at shallow levels below the valley floor, has much younger water, with mean age 1.2 years and water volume 0.4 cubic kilometers

  11. Simulation for the development of the continuous groundwater flow measurement technology

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kaoru; Kumagai, Koki; Fujima, Ritsuko; Chikahisa, Hiroshi

    The flow of groundwater varies with time due to rainfall, atmospheric pressure change, tidal change, melting of snow during seasonal change, underground construction works etc. Therefore, to increase the precision of assessing in-situ groundwater flow characteristics, it is important to measure continuously the direction and velocity of the flow, in addition to obtaining accurate data for the afore mentioned environmental changes. The first part of this paper describes the development of a new device for measuring the direction and velocity of groundwater flow. The device was composed of a unique floating sensor with a hinge end at the bottom, which enabled continuous measurement of groundwater flow based on image data processing technique. In the second part, discussion is focused on clarifying the optimum cross-section shape and the behavior of the float sensor in saltwater and freshwater using numerical analysis.

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

  13. Degradation of ground ice in a changing climate: the potential impact of groundwater flow

    NASA Astrophysics Data System (ADS)

    de Grandpré, I.; Fortier, D.; Stephani, E.

    2011-12-01

    Climate changes affecting the North West portion of Canada alter the thermal state of the permafrost and promote ground ice degradation. Melting of ground ice leads to greater water flow into the ground and to significant hydraulic changes (i.e. drainage of peatland and lakes, triggering of thermokarst and new groundwater flow patterns). Road infrastructures built on permafrost are particularly sensitive to permafrost degradation. Road construction and maintenance induce heat flux into the ground by the increase of solar radiation absorption (comparing to natural ground), the increase of snow cover on side slopes, the infiltration of water in embankment material and the migration of surface water in the active layer. The permafrost under the roads is therefore submitted to a warmer environment than in natural ground and his behavior reflects how the permafrost will act in the future with the global warming trend. The permafrost degradation dynamic under a road was studied at the Beaver Creek (Yukon) experimental site located on the Alaska Highway. Permafrost was characterized as near-zero Celcius and highly susceptible to differential thaw-settlement due to the ground ice spatial distribution. Ice-rich cryostructures typical of syngenetic permafrost (e.g. microlenticular) were abundant in the upper and lower cryostratigraphic units of fine-grained soils (Units 1, 2A, and 2C). The middle ice-poor silt layer (Unit 2B) characterized by porous cryostructure comprised the top of a buried ice-wedge network extending several meters in the underlying layers and susceptible to degradation by thermo-erosion. These particular features of the permafrost at the study site facilitated the formation of taliks (unfrozen zones) under the road which leaded to a greater water flow. We believe that water flow is promoting an acceleration of permafrost degradation by advective heat transfer. This process remains poorly studied and quantified in permafrost environment. Field data on

  14. Occurrence and transport of pharmaceuticals in a karst groundwater system affected by domestic wastewater treatment plants

    NASA Astrophysics Data System (ADS)

    Einsiedl, Florian; Radke, Michael; Maloszewski, Piotr

    2010-09-01

    The occurrence of two pharmaceuticals, ibuprofen and diclofenac, in a vulnerable karst groundwater system was investigated. The hydrogeology of the karst system was identified by collecting 3H samples in groundwater over 27 years and by performing tracer tests. The isotopes and tracer data were interpreted by mathematical modeling to estimate the mean transit time of water and to characterize the hydrogeological flow paths in the groundwater system. By this approach, a mean 3H transit time of 4.6 years for the fissured-porous karst aquifer was determined, whereas the fast flowing water in the conduit system showed a mean transit time of days. Both pharmaceuticals which infiltrated along sinkholes and small streams into the karst system were detected in concentrations of up to approximately 1 μg/L in effluent water of the wastewater treatment plants. Diclofenac was present in most samples collected from four springs discharging the karst groundwater to the rivers Altmühl and Anlauter in concentrations between 3.6 and 15.4 ng/L. In contrast, ibuprofen was rarely detected in groundwater. The results of this study suggest that both pharmaceuticals move into the fractured system of the karst system and go into storage. Thus dilution processes are the dominant control on the concentrations of both pharmaceuticals in the fractured system, whereas biodegradation is likely less important.

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

    NASA Astrophysics Data System (ADS)

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

    2002-09-01

    The current conceptual model of the unconfined karstic aquifer in the Yucatan Peninsula, Mexico, is that a fresh-water lens floats above denser saline water that penetrates more than 40 km inland. The transmissivity of the aquifer is very high so the hydraulic gradient is very low, ranging from 7-10 mm/km through most of the northern part of the peninsula. The computer modeling program AQUIFER was used to investigate the regional groundwater flow in the aquifer. The karstified zone was modeled using the assumption that it acts hydraulically similar to a granular, porous medium. As part of the calibration, the following hypotheses were tested: (1) karstic features play an important role in the groundwater-flow system; (2) a ring or belt of sinkholes in the area is a manifestation of a zone of high transmissivity that facilitates the channeling of groundwater toward the Gulf of Mexico; and (3) the geologic features in the southern part of Yucatan influence the groundwater-flow system. The model shows that the Sierrita de Ticul fault, in the southwestern part of the study area, acts as a flow barrier and head values decline toward the northeast. The modeling also shows that the regional flow-system dynamics have not been altered despite the large number of pumping wells because the volume of water pumped is small compared with the volume of recharge, and the well-developed karst system of the region has a very high hydraulic conductivity. Résumé. Le modèle conceptuel classique de l'aquifère karstique libre de la péninsule du Yucatan (Mexique) consiste en une lentille d'eau douce flottant sur une eau salée plus dense qui pénètre à plus de 40 km à l'intérieur des terres. La transmissivité de l'aquifère est très élevée, en sorte que le gradient hydraulique est très faible, compris entre 7 et 10 mm/km dans la plus grande partie du nord de la péninsule. Le modèle AQUIFER a été utilisé pour explorer les écoulements souterrains régionaux dans cet

  16. Investigation of surfactant-enhanced dissolution of entrapped nonaqueous phase liquid chemicals in a two-dimensional groundwater flow field.

    PubMed

    Saba, T; Illangasekare, T H; Ewing, J

    2001-09-01

    Because of their low solubility, waste chemicals in the form of nonaqueous phase liquids (NAPLs) that are entrapped in subsurface formations act as long-term sources of groundwater contamination. In the design of remediation schemes that use surfactants, it is necessary to estimate the mass transfer rate coefficients under multi-dimensional flow fields that exit at field sites. In this study, we investigate mass transfer under a two-dimensional flow field to obtain an understanding of the basic mechanisms of surfactant-enhanced dissolution and to quantify the mass transfer rates. Enhanced dissolution experiments in a two-dimensional test cell were conducted to measure rates of mass depletion from entrapped NAPLs to a flowing aqueous phase containing a surfactant. In situ measurement of transient saturation changes using a gamma attenuation system revealed dissolution patterns that are affected by the dimensionality of the groundwater flow field. Numerical modeling of local flow fields that changed with time, due to depletion of NAPL sources, enabled the examination of the basic mechanisms of NAPL dissolution in complex groundwater systems. Through nonlinear regression analysis, mass transfer rates were correlated to porous media properties, NAPL saturation and aqueous phase velocity. Results from the experiments and numerical analyses were used to identify deficiencies in existing methods of analysis that uses assumptions of one-dimensional flow, homogeneity of aquifer properties, local equilibrium and idealized transient mass transfer. PMID:11530927

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

    PubMed

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

    2013-03-01

    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. PMID:22891702

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Knowledge of groundwater residence times and recharge locations is vital to the sustainable management of groundwater resources. Here we investigate groundwater residence times and patterns of recharge in the Gellibrand Valley, southeast Australia, where outcropping aquifer sediments of the Eastern View Formation form an "aquifer window" that may receive diffuse recharge from rainfall and recharge from the Gellibrand River. To determine recharge patterns and groundwater flow paths, environmental isotopes (3H, 14C, δ13C, δ18O, δ2H) are used in conjunction with groundwater geochemistry and continuous monitoring of groundwater elevation and electrical conductivity. The water table fluctuates by 0.9 to 3.7 m annually, implying recharge rates of 90 and 372 mm yr-1. However, residence times of shallow (11 to 29 m) groundwater determined by 14C are between 100 and 10 000 years, 3H activities are negligible in most of the groundwater, and groundwater electrical conductivity remains constant over the period of study. Deeper groundwater with older 14C ages has lower δ18O values than younger, shallower groundwater, which is consistent with it being derived from greater altitudes. The combined geochemistry data indicate that local recharge from precipitation within the valley occurs through the aquifer window, however much of the groundwater in the Gellibrand Valley predominantly originates from the regional recharge zone, the Barongarook High. The Gellibrand Valley is a regional discharge zone with upward head gradients that limits local recharge to the upper 10 m of the aquifer. Additionally, the groundwater head gradients adjacent to the Gellibrand River are generally upwards, implying that it does not recharge the surrounding groundwater and has limited bank storage. 14C ages and Cl concentrations are well correlated and Cl concentrations may be used to provide a first-order estimate of groundwater residence times. Progressively lower chloride concentrations from 10

  20. Effects of groundwater lateral flow on land surface processes: a case study in Heihe River Basin, north-west of China

    NASA Astrophysics Data System (ADS)

    Xie, Z.; Zeng, Y.; Yu, Y.

    2015-12-01

    As an important component of hydrologic cycle, groundwater is affected by topography, vegetation, climate condition, and anthropogenic activity. Groundwater horizontal convergence and divergence and vertical interaction with soil water result in variations of soil moisture, water and energy exchanges between the land surface and the atmosphere, which ultimately influences climate. In this work, a two-dimensional groundwater lateral flow scheme based on groundwater mass equation, is developed and incorporated into the land surface model CLM4.5 to investigate effects of groundwater lateral flow on land surface processes in a river basin. A 30-year simulation with groundwater lateral flow and a control run without the horizontal movement are conducted over Heihe River Basin, north-west China, from 1979 to 2012 using the developed model. Results show that with groundwater lateral flow, equilibrium distribution of groundwater table shows more spatial variability following topography rather than the water balance between local precipitation and evapotranspiration, and are much closer to well observations especially over middle reaches area. Along with shallower groundwater table over piedmont areas in the middle reaches, increased soil moisture is shown which alleviates the underestimation of CLM4.5 at here. Changes in evapotranspiration are occurred and it is mainly controlled by the variation of local surface soil moisture, since water is the major limitation factor of evapotranspiration over this arid area. Besides, groundwater lateral flow can change the distribution of surface runoff by changing the saturated area fraction of each model grid cell. Energy cycle also responds to the changes of hydrological cycle which redistributes the sensible heat flux and latent heat flux in the entire basin.

  1. Regional groundwater flow and geochemical evolution in the Amacuzac River Basin, Mexico

    NASA Astrophysics Data System (ADS)

    Morales-Casique, Eric; Guinzberg-Belmont, Jacobo; Ortega-Guerrero, Adrián

    2016-05-01

    An approach is presented to investigate the regional evolution of groundwater in the basin of the Amacuzac River in Central Mexico. The approach is based on groundwater flow cross-sectional modeling in combination with major ion chemistry and geochemical modeling, complemented with principal component and cluster analyses. The hydrogeologic units composing the basin, which combine aquifers and aquitards both in granular, fractured and karstic rocks, were represented in sections parallel to the regional groundwater flow. Steady-state cross-section numerical simulations aided in the conceptualization of the groundwater flow system through the basin and permitted estimation of bulk hydraulic conductivity values, recharge rates and residence times. Forty-five water locations (springs, groundwater wells and rivers) were sampled throughout the basin for chemical analysis of major ions. The modeled gravity-driven groundwater flow system satisfactorily reproduced field observations, whereas the main geochemical processes of groundwater in the basin are associated to the order and reactions in which the igneous and sedimentary rocks are encountered along the groundwater flow. Recharge water in the volcanic and volcano-sedimentary aquifers increases the concentration of HCO3 -, Mg2+ and Ca2+ from dissolution of plagioclase and olivine. Deeper groundwater flow encounters carbonate rocks, under closed CO2 conditions, and dissolves calcite and dolomite. When groundwater encounters gypsum lenses in the shallow Balsas Group or the deeper Huitzuco anhydrite, gypsum dissolution produces proportional increased concentration of Ca2+ and SO4 2-; two samples reflected the influence of hydrothermal fluids and probably halite dissolution. These geochemical trends are consistent with the principal component and cluster analyses.

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

    SciTech Connect

    Doughty, Christine; Karasaki, Kenzi

    2002-12-11

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    Groundwater chemistry and isotopic data from 40 production wells in the Atemajac and Toluquilla Valleys, located in and around the Guadalajara metropolitan area, were determined to develop a conceptual model of groundwater flow processes and mixing. Multivariate analysis including cluster analysis and principal component analysis were used to elucidate distribution patterns of constituents and factors controlling groundwater chemistry. Based on this analysis, groundwater was classified into four groups: cold groundwater, hydrothermal water, polluted groundwater and mixed groundwater. Cold groundwater is characterized by low temperature, salinity, and Cl and Na concentrations and is predominantly of Na-HCO3 type. It originates as recharge at Primavera caldera and is found predominantly in wells in the upper Atemajac Valley. Hydrothermal water is characterized by high salinity, temperature, Cl, Na, HCO3, and the presence of minor elements such as Li, Mn and F. It is a mixed HCO3 type found in wells from Toluquilla Valley and represents regional flow circulation through basaltic and andesitic rocks. Polluted groundwater is characterized by elevated nitrate and sulfate concentrations and is usually derived from urban water cycling and subordinately from agricultural practices. Mixed groundwaters between cold and hydrothermal components are predominantly found in the lower Atemajac Valley. Tritium method elucidated that practically all of the sampled groundwater contains at least a small fraction of modern water. The multivariate mixing model M3 indicates that the proportion of hydrothermal fluids in sampled well water is between 13 (local groundwater) and 87% (hydrothermal water), and the proportion of polluted water in wells ranges from 0 to 63%. This study may help local water authorities to identify and quantify groundwater contamination and act accordingly.

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

    USGS Publications Warehouse

    Leighton, David A.; Phillips, Steven P.

    2003-01-01

    Antelope Valley, California, is a topographically closed basin in the western part of the Mojave Desert, about 50 miles northeast of Los Angeles. The Antelope Valley ground-water basin is about 940 square miles and is separated from the northern part of Antelope Valley by faults and low-lying hills. Prior to 1972, ground water provided more than 90 percent of the total water supply in the valley; since 1972, it has provided between 50 and 90 percent. Most ground-water pumping in the valley occurs in the Antelope Valley ground-water basin, which includes the rapidly growing cities of Lancaster and Palmdale. Ground-water-level declines of more than 200 feet in some parts of the ground-water basin have resulted in an increase in pumping lifts, reduced well efficiency, and land subsidence of more than 6 feet in some areas. Future urban growth and limits on the supply of imported water may continue to increase reliance on ground water. To better understand the ground-water flow system and to develop a tool to aid in effectively managing the water resources, a numerical model of ground-water flow and land subsidence in the Antelope Valley ground-water basin was developed using old and new geohydrologic information. The ground-water flow system consists of three aquifers: the upper, middle, and lower aquifers. The aquifers, which were identified on the basis of the hydrologic properties, age, and depth of the unconsolidated deposits, consist of gravel, sand, silt, and clay alluvial deposits and clay and silty clay lacustrine deposits. Prior to ground-water development in the valley, recharge was primarily the infiltration of runoff from the surrounding mountains. Ground water flowed from the recharge areas to discharge areas around the playas where it discharged either from the aquifer system as evapotranspiration or from springs. Partial barriers to horizontal ground-water flow, such as faults, have been identified in the ground-water basin. Water-level declines owing to

  5. Groundwater resources of the Wood River Valley, Idaho--A groundwater-flow model for resource management

    USGS Publications Warehouse

    Bartolino, James; Vincent, Sean

    2013-01-01

    The U.S. Geological Survey (USGS), in collaboration with the Idaho Department of Water Resources (IDWR), will use the current understanding of the Wood River Valley aquifer system to construct a MODFLOW numerical groundwater-flow model to simulate potential anthropogenic and climatic effects on groundwater and surface-water resources. This model will serve as a tool for water rights administration and water-resource management and planning. The study will be conducted over a 3-year period from late 2012 until model and report completion in 2015.

  6. 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.

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

    USGS Publications Warehouse

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

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

    EPA Science Inventory

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

  10. Combining groundwater quality analysis and a numerical flow simulation for spatially establishing utilization strategies for groundwater and surface water in the Pingtung Plain

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    Overexploitation of groundwater is a common problem in the Pingtung Plain area of Taiwan, resulting in substantial drawdown of groundwater levels as well as the occurrence of severe seawater intrusion and land subsidence. Measures need to be taken to preserve these valuable groundwater resources. This study seeks to spatially determine the most suitable locations for the use of surface water on this plain instead of extracting groundwater for drinking, irrigation, and aquaculture purposes based on information obtained by combining groundwater quality analysis and a numerical flow simulation assuming the planning of manmade lakes and reservoirs to the increase of water supply. The multivariate indicator kriging method is first used to estimate occurrence probabilities, and to rank townships as suitable or unsuitable for groundwater utilization according to water quality standards for drinking, irrigation, and aquaculture. A numerical model of groundwater flow (MODFLOW) is adopted to quantify the recovery of groundwater levels in townships after model calibration when groundwater for drinking and agricultural demands has been replaced by surface water. Finally, townships with poor groundwater quality and significant increases in groundwater levels in the Pingtung Plain are prioritized for the groundwater conservation planning based on the combined assessment of groundwater quality and quantity. The results of this study indicate that the integration of groundwater quality analysis and the numerical flow simulation is capable of establishing sound strategies for joint groundwater and surface water use. Six southeastern townships are found to be suitable locations for replacing groundwater with surface water from manmade lakes or reservoirs to meet drinking, irrigation, and aquaculture demands.

  11. Quantifying uranium complexation by groundwater dissolved organic carbon using asymmetrical flow field-flow fractionation

    NASA Astrophysics Data System (ADS)

    Ranville, James F.; Hendry, M. Jim; Reszat, Thorsten N.; Xie, Qianli; Honeyman, Bruce D.

    2007-05-01

    The long-term mobility of actinides in groundwaters is important for siting nuclear waste facilities and managing waste-rock piles at uranium mines. Dissolved organic carbon (DOC) may influence the mobility of uranium, but few field-based studies have been undertaken to examine this in typical groundwaters. In addition, few techniques are available to isolate DOC and directly quantify the metals complexed to it. Determination of U-organic matter association constants from analysis of field-collected samples compliments laboratory measurements, and these constants are needed for accurate transport calculations. The partitioning of U to DOC in a clay-rich aquitard was investigated in 10 groundwater samples collected between 2 and 30 m depths at one test site. A positive correlation was observed between the DOC (4-132 mg/L) and U concentrations (20-603 μg/L). The association of U and DOC was examined directly using on-line coupling of Asymmetrical Flow Field-Flow Fractionation (AsFlFFF) with UV absorbance (UVA) and inductively coupled plasma-mass spectrometer (ICP-MS) detectors. This method has the advantages of utilizing very small sample volumes (20-50 μL) as well as giving molecular weight information on U-organic matter complexes. AsFlFFF-UVA results showed that 47-98% of the DOC (4-136 mg C/L) was recovered in the AsFlFFF analysis, of which 25-64% occurred in the resolvable peak. This peak corresponded to a weight-average molecular weight of about 900-1400 Daltons (Da). In all cases, AsFlFFF-ICP-MS suggested that ≤ 2% of the U, likely present as U(VI), was complexed with the DOC. This result was in good agreement with the U speciation modeling performed on the sample taken from the 2.3 m depth, which predicted approximately 3% DOC-complexed U. This good agreement suggests that the AsFlFFF-ICP-MS method may be very useful for determining U-organic matter association in small volume samples. Because the pH (7.0-8.1) and carbonate concentrations of these waters

  12. Documentation of finite-difference model for simulation of three-dimensional ground-water flow

    USGS Publications Warehouse

    Trescott, Peter C.; Larson, S.P.

    1976-01-01

    User experience has indicated that the documentation of the model of three-dimensional ground-water flow (Trescott and Larson, 1975) should be expanded. This supplement is intended to fulfill that need. The original report emphasized the theory of the strongly implicit procedure, instructions for using the groundwater-flow model, and practical considerations for application. (See also W76-02962 and W76-13085) (Woodard-USGS)

  13. Estimation of the velocities and discharge rates of groundwater flows by helium and tritium distributions

    SciTech Connect

    Ivanov, V.V.; Antonenko, E.F.; Obukhova, S.N.

    1995-11-01

    Modeling is used to show that bends in the curves of groundwater flows and confluence of different-age flows demonstrate themselves in spatial variability in concentration fields of {sup 4}He, {sup 3}H, and {sup 14}C isotopes. The results are used to reveal typical flows in a section of Switzerland and to estimate their velocities and discharge rates.

  14. Sructural Control Of Groundwater Flow In The Sinai Peninsula: Integrated Studies

    NASA Astrophysics Data System (ADS)

    Mohamed, L.; Sultan, M.; Farag, A. Z. A.

    2014-12-01

    The crystalline complex and overlying sedimentary sequences in southern and central Sinai are highly dissected by numerous faults, shear systems, and dikes, hereafter referred to as discontinuities. Understanding the distribution of these discontinuities, their cross cutting relations, and the hydraulic gradient gives clues as to the distribution of water resources in the area. In the study area, extensional tectonics has been active as early as the Precambrian era as evidenced by the widely distributed dikes, bimodal volcanics, and dip-slip faults and shear zones of varying ages. These extensional tectonics and associated structural elements enhance the porosity and permeability of Sinai's basement and overlying sedimentary sequences. To investigate the impact of the discontinuities on groundwater flow, the following steps were conducted: 1) the spatial and temporal precipitation events over the basement complex were identified from TRMM data; 2) observations extracted from temporal change in backscattering coefficient in radar (Envisat ASAR radar scenes) were used to identify water-bearing discontinuities; 3) the discontinuities were delineated using false color images that were generated from ASTER, SIR C and band ratio images, 4) field observations, Very Low Frequency (VLF), magnetic investigations, and stable isotopic analyses for groundwater samples were then applied to refine satellite-based observations and selections, test the validity of our satellite-based methodologies for locating sub-vertical discontinuities, and decipher their role as conduits or barriers for groundwater flow. Findings include: (1) sub-vertical faults and shear zones and highly weathered chilled margins of sub-vertical mafic dykes are water-bearing and are conducive for groundwater flow; felsic dykes are massive (do not promote groundwater flow), (2) groundwater flow generally follows the topographic relief, but locally the flow is controlled by the discontinuities, (3

  15. Well data and groundwater flow direction problem: Steuben County, Indiana case study

    SciTech Connect

    Goings, M.H. ); Isiorho, S.A. . Dept. of Geosciences)

    1994-04-01

    The rapid industrial growth in Northeastern Indiana has lead to the demand for more complete geologic information for Steuben County, Indiana by the citizenry. The information would allow environmental scientists, geologists and engineers to more accurately predict the potential migration and impact of pollutants on the soil and groundwater. As part of ongoing environmental site investigations in Steuben County, well data were collected from Indiana Department of Environmental management (IDEM) and the State of Indiana Department of Natural Resources to determine local and regional groundwater flow directions. Of the 162 registered wells in the study area, only 67 of them, that is, 41% of the data could be used. The remaining well data could not be used because of poor, inaccurate or incomplete information on the forms (i.e., location description, well log, elevation, etc.). The regional groundwater flow direction was northwest as would be expected from the topography. A groundwater divide or ridge that was implied from the local groundwater flow directions could not be confirmed due to poor well data. The determination of groundwater flow direction was made more complicated due to incomplete well logs from drillers. Increased industrial activities in the region could lead to greater potential for surface and groundwater pollution problems. It is recommended that well data be collected by qualified personnel (field geologists) during well drilling.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. Heat and Groundwater Flow through Continental Flood Basalt Provinces: Insights Gained from Alternative Models of Permeability/Depth Relationships for the Columbia Plateau, USA

    NASA Astrophysics Data System (ADS)

    Burns, E. R.; Williams, C. F.; Ingebritsen, S.; Voss, C. I.; Spane, F.; DeAngelo, J.

    2014-12-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (~3.5 orders of magnitude) at 600-900 m depth and ~40oC. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at ~600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Abrupt k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration. Because pore filling hydrothermal minerals are largely controlled by the major mineral assemblages of the volcanic rocks, other continental flood basalt provinces may also have large permeability changes at depths corresponding to ~40oC.

  18. The impact of glaciations and glacial processes on groundwater flow dynamics: a numerical investigation

    NASA Astrophysics Data System (ADS)

    Sterckx, A.; Lemieux, J. M.; Vaikmae, R.

    2015-12-01

    Numerical models are widely used to investigate the impact of glaciations on groundwater flow systems because they can simulate complex glacial processes. However, it isn't clear which of these processes are relevant to adequately capture groundwater flow dynamics. Given the complexity of representing these processes in a numerical model and the paucity of field data available for their validation, it is of prime interest to assess how they impact groundwater flow and if any of these processes could be neglected. In order to assess the specific impact of glacial processes on groundwater flow dynamics, those processes were included in the numerical model FEFLOW and simulations were conducted in a simple conceptual model representing a 21 ky glacial cycle in a sedimentary basin. The following processes have been simulated: subglacial recharge, linear and non-linear compaction of the porous medium under the weight of the ice, isostasy, proglacial lakes, as well as permafrost. Solute transport was simulated along with groundwater flow to track groundwater originating from the ice-sheet. To interpret the results, a base case scenario considering only subglacial recharge was selected and compared with the other scenarios, where individual glacial processes were simulated. When comparing the results at the end of the simulations, it appears that most of the aforementioned glacial processes don't lead to a significant difference in meltwater distribution with respect to the base case. Only hydromechanical coupling brings some noticeable change. Conversely, the type and the value of the boundary condition applied at the base of the ice-sheet play a major role in groundwater flow dynamics. The presence of confining hydrogeological units also seems to be a key to understand the long-term effect of glaciations. These results suggest that some of the glacial processes may be neglected for the simulation of groundwater flow dynamics during a glacial period.

  19. Ramification of Channel Networks Incised by Groundwater Flow

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  20. Monitoring the Remediation of Salt-Affected Soils and Groundwater

    NASA Astrophysics Data System (ADS)

    Bentley, L. R.; Callaghan, M. V.; Cey, E. E.

    2008-12-01

    Salt-affected soil is one of the most common environmental issues facing the petroleum hydrocarbon industry. Large quantities of brines are often co-produced with gas and oil and have been introduced into the environment through, for example, flare pits, drilling operations and pipe line breaks. Salt must be flushed from the soil and tile drain systems can be used to collect salt water which is then be routed for disposal. A flushing experiment over a 2 m deep tile drain system is being monitored by arrays of tensiometers, repeated soil coring, direct push electrical conductivity profiles (PTC), electromagnetic surveys and electrical resistivity tomography (ERT) surveys. Water table elevation is monitored with pressure transducers. Thermocouple arrays provide temperature profiles that are used to adjust electrical conductivity data to standard temperature equivalents. A 20 m by 20 m plot was deep tilled and treated with soil amendments. Numerous infiltration tests were conducted inside and outside the plot area using both a tension infiltrometer and Guelph permeameter to establish changes in soil hydraulic properties and macroporosity as a result of deep tillage. The results show that till greatly diminished the shallow macroporosity and increased the matrix saturated hydraulic conductivity. A header system is used to evenly flood the plot with 10 m3 of water on each of three consecutive days for an approximate total of 7.5 cm of water. The flood event is being repeated four times over a period of 6 weeks. Baseline PTC and ERT surveys show that the salt is concentrated in the upper 2 to 3 m of soil. Tensiometer data show that the soil at 30 cm depth responds within 2 to 3 hours to flooding events once the soil is wetted and begins to dry again after one week. Soil suction at 1.5 m does not show immediate response to the daily flooding events, but is steadily decreasing in response to the flooding and rainfall events. An ERT survey in October will provide the first

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

    USGS Publications Warehouse

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

    2012-01-01

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

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

    PubMed

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

    2012-01-01

    Various approaches have been proposed to manage the nonlinearities associated with the unconfined flow equation and to simulate perched groundwater conditions using the MODFLOW family of codes. The approaches comprise a variety of numerical techniques to prevent dry cells from becoming inactive and to achieve a stable solution focused on formulations of the unconfined, partially-saturated, groundwater flow equation. Keeping dry cells active avoids a discontinuous head solution which in turn improves the effectiveness of parameter estimation software that relies on continuous derivatives. Most approaches implement an upstream weighting of intercell conductance and Newton-Raphson linearization to obtain robust convergence. In this study, several published approaches were implemented in a stepwise manner into MODFLOW for comparative analysis. First, a comparative analysis of the methods is presented using synthetic examples that create convergence issues or difficulty in handling perched conditions with the more common dry-cell simulation capabilities of MODFLOW. Next, a field-scale three-dimensional simulation is presented to examine the stability and performance of the discussed approaches in larger, practical, simulation settings. PMID:21635246

  3. Groundwater flow delineation study at the Massachusetts Military Reservation using the colloidal borescope

    SciTech Connect

    Kearl, P.M.; Gardner, F.G.; Gunderson, M.J.

    1993-02-01

    Observations of colloidal movement under natural conditions using the colloidal borescope were conducted at several sites in the vicinity of the Massachusetts Military Reservation (MM) located on Cape Cod. The purpose of the study was to assess the reliability of the colloidal borescope and provide additional hydrogeologic data for site-characterization work. Because of the variability observed in groundwater flow at other sites, a well-characterized site was needed to test the borescope. Results of this work indicate that existing hydrologic information specific to the various sites tested at the MM compares favorably with the borehole velocity data collected with the colloidal borescope. Direction measurements at the MM, however, appear to be less reliable than at other sites tested. Most significant among factors potentially affecting direction measurements is the relatively flat hydraulic gradient at the MM, which is an order of magnitude less than at other sites. This is due to the gentle topography and the relatively high permeability of the aquifer. Under these conditions, the geometric alignment of preferential flow paths could dominate flow direction. If the gradient is increased, flow will tend to parallel the hydraulic gradient. This report describes the field site and the colloidal borescope and discusses the results and conclusions of the field investigations.

  4. Seasonal Reversals of Groundwater Flow Around Lakes and the Relevance to Stagnation Points and Lake Budgets

    NASA Astrophysics Data System (ADS)

    Anderson, Mary P.; Munter, James A.

    1981-08-01

    Several researchers have observed seasonal reversals in the direction of groundwater flow around lakes. If these reversals are prolonged and are accompanied by the formation of a stagnation point, they may have a significant effect on a lake's water and nutrient budgets. The formation of a stagnation point at a flow-through lake (i.e., a lake that receives groundwater through part of the lake basin and recharges the groundwater system over the rest of the lake basin) is accomplished by the formation of a groundwater mound on the downgradient side of the lake. In this paper the seasonal formation of a stagnation point at Snake Lake, Wisconsin, is investigated with the aid of two-dimensional transient computer models applied in cross section and areally. The analysis demonstrates the potential for the seasonal formation of a stagnation point at a flow-through lake and provides some insight into the transient development of the stagnation point.

  5. Radiocarbon determinations for estimating groundwater flow velocities in central Florida

    USGS Publications Warehouse

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

    1965-01-01

    Carbon-14 activity was determined from HCO3- in samples of groundwater obtained from the principal artesian aquifer in Florida. From these data the "age" of water obtained from a series of wells, each progressively farther down gradient on the piezometric surface, was established. Relative carbon-14 ages indicated a velocity of groundwater movement of 23 feet (7 meters) per year for about 85 miles (137 kilometers) of travel. A velocity of 23 feet per year was calculated independently from Darcy's law.

  6. Comparison of groundwater flow in Southern California coastal aquifers

    USGS Publications Warehouse

    Hanson, Randall T.; Izbicki, John A.; Reichard, Eric G.; Edwards, Brian D.; Land, Michael; Martin, Peter

    2009-01-01

    Maintaining the sustainability of Southern California coastal aquifers requires joint management of surface water and groundwater (conjunctive use). This requires new data collection and analyses (including research drilling, modern geohydrologic investigations, and development of detailed computer groundwater models that simulate the supply and demand components separately), implementation of new facilities (including spreading and injection facilities for artificial recharge), and establishment of new institutions and policies that help to sustain the water resources and better manage regional development.

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

    NASA Astrophysics Data System (ADS)

    Price, René M.; Top, Zafer; Happell, James D.; Swart, Peter K.

    2003-09-01

    The concentrations of tritium (3H) and helium isotopes (3He and 4He) were used as tracers of groundwater flow in the surficial aquifer system (SAS) beneath Everglades National Park (ENP), south Florida. From ages determined by 3H/3He dating techniques, groundwater within the upper 28 m originated within the last 30 years. Below 28 m, waters originated prior to 30 years before present with evidence of mixing at the interface. Interannual variation of the 3H/3He ages within the upper 28 m was significant throughout the 3 year investigation, corresponding with varying hydrologic conditions. In the region of Taylor Slough Bridge, younger groundwater was consistently detected below older groundwater in the Biscayne Aquifer, suggesting preferential flow to the lower part of the aquifer. An increase in 4He with depth in the SAS indicated that radiogenic 4He produced in the underlying Hawthorn Group migrates into the SAS by diffusion. Higher Δ4He values in brackish groundwaters compared to fresh waters from similar depths suggested a possible enhanced vertical transport of 4He in the seawater mixing zone. Groundwater salinity measurements indicated the presence of a wide (6-28 km) seawater mixing zone. Comparison of groundwater levels with surface water levels in this zone indicated the potential for brackish groundwater discharge to the overlying Everglades surface water.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Xing, Lina; Guo, Huaming; Zhan, Yanhong

    2013-07-01

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

  10. Sensitivity analysis of hydrogeological parameters affecting groundwater storage change caused by sea level rise

    NASA Astrophysics Data System (ADS)

    Shin, J.; Kim, K.-H.; Lee, K.-K.

    2012-04-01

    Sea level rise, which is one of the representative phenomena of climate changes caused by global warming, can affect groundwater system. The rising trend of the sea level caused by the global warming is reported to be about 3 mm/year for the most recent 10 year average (IPCC, 2007). The rate of sea level rise around the Korean peninsula is reported to be 2.30±2.22 mm/yr during the 1960-1999 period (Cho, 2002) and 2.16±1.77 mm/yr (Kim et al., 2009) during the 1968-2007 period. Both of these rates are faster than the 1.8±0.5 mm/yr global average for the similar 1961-2003 period (IPCC, 2007). In this study, we analyzed changes in the groundwater environment affected by the sea level rise by using an analytical methodology. We tried to find the most effective parameters of groundwater amount change in order to estimate the change in fresh water amount in coastal groundwater. A hypothetical island model of a cylindrical shape in considered. The groundwater storage change is bi-directional as the sea level rises according to the natural and hydrogeological conditions. Analysis of the computation results shows that topographic slope and hydraulic conductivity are the most sensitive factors. The contributions of the groundwater recharge rate and the thickness of aquifer below sea level are relatively less effective. In the island with steep seashore slopes larger than 1~2 degrees or so, the storage amount of fresh water in a coastal area increases as sea level rises. On the other hand, when sea level drops, the storage amount decreases. This is because the groundwater level also rises with the rising sea level in steep seashores. For relatively flat seashores, where the slope is smaller than around 1-2 degrees, the storage amount of coastal fresh water decreases when the sea level rises because the area flooded by the rising sea water is increased. The volume of aquifer fresh water in this circumstance is greatly reduced in proportion to the flooded area with the sea

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

    USGS Publications Warehouse

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

    2011-01-01

    Groundwater is the sole source of drinking water for the population of Bainbridge Island. Increased use of groundwater supplies on Bainbridge Island as the population has grown over time has created concern about the quantity of water available and whether saltwater intrusion will occur as groundwater usage increases. A groundwater-flow model was developed to aid in the understanding of the groundwater system and the effects of groundwater development alternatives on the water resources of Bainbridge Island. Bainbridge Island is underlain by unconsolidated deposits of glacial and nonglacial origin. The surficial geologic units and the deposits at depth were differentiated into aquifers and confining units on the basis of areal extent and general water-bearing characteristics. Eleven principal hydrogeologic units are recognized in the study area and form the basis of the groundwater-flow model. A transient variable-density groundwater-flow model of Bainbridge Island and the surrounding area was developed to simulate current (2008) groundwater conditions. The model was calibrated to water levels measured during 2007 and 2008 using parameter estimation (PEST) to minimize the weighted differences or residuals between simulated and measured hydraulic head. The calibrated model was used to make some general observations of the groundwater system in 2008. Total flow through the groundwater system was about 31,000 acre-ft/ yr. The recharge to the groundwater system was from precipitation and septic-system returns. Groundwater flow to Bainbridge Island accounted for about 1,000 acre-ft/ yr or slightly more than 5 percent of the recharge amounts. Groundwater discharge was predominately to streams, lakes, springs, and seepage faces (16,000 acre-ft/yr) and directly to marine waters (10,000 acre-ft/yr). Total groundwater withdrawals in 2008 were slightly more than 6 percent (2,000 acre-ft/yr) of the total flow. The calibrated model was used to simulate predevelopment conditions

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

    USGS Publications Warehouse

    Snyder, D.T.; Wilkinson, J.M.; Orzol, L.L.

    1996-01-01

    A ground-water flow model was used in conjunction with particle tracking to evaluate ground-water vulnerability in Clark County, Washington. Using the particle-tracking program, particles were placed in every cell of the flow model (about 60,000 particles) and tracked backwards in time and space upgradient along flow paths to their recharge points. A new computer program was developed that interfaces the results from a particle-tracking program with a geographic information system (GIS). The GIS was used to display and analyze the particle-tracking results. Ground-water vulnerability was evaluated by selecting parts of the ground-water flow system and combining the results with ancillary information stored in the GIS to determine recharge areas, characteristics of recharge areas, downgradient impact of land use at recharge areas, and age of ground water. Maps of the recharge areas for each hydrogeologic unit illustrate the presence of local, intermediate, or regional ground-water flow systems and emphasize the three-dimensional nature of the ground-water flow system in Clark County. Maps of the recharge points for each hydrogeologic unit were overlaid with maps depicting aquifer sensitivity as determined by DRASTIC (a measure of the pollution potential of ground water, based on the intrinsic characteristics of the near-surface unsaturated and saturated zones) and recharge from on-site waste-disposal systems. A large number of recharge areas were identified, particularly in southern Clark County, that have a high aquifer sensitivity, coincide with areas of recharge from on-site waste-disposal systems, or both. Using the GIS, the characteristics of the recharge areas were related to the downgradient parts of the ground-water system that will eventually receive flow that has recharged through these areas. The aquifer sensitivity, as indicated by DRASTIC, of the recharge areas for downgradient parts of the flow system was mapped for each hydrogeologic unit. A number of

  13. Vestibular stimulation affects optic-flow sensitivity.

    PubMed

    Edwards, Mark; O'Mahony, Simon; Ibbotson, Michael R; Kohlhagen, Stuart

    2010-01-01

    Typically, multiple cues can be used to generate a particular percept. Our area of interest is the extent to which humans are able to synergistically combine cues that are generated when moving through an environment. For example, movement through the environment leads to both visual (optic-flow) and vestibular stimulation, and studies have shown that non-human primates are able to combine these cues to generate a more accurate perception of heading than can be obtained with either cue in isolation. Here we investigate whether humans show a similar ability to synergistically combine optic-flow and vestibular cues. This was achieved by determining the sensitivity to optic-flow stimuli while physically moving the observer, and hence producing a vestibular signal, that was either consistent with the optic-flow signal, eg a radially expanding pattern coupled with forward motion, or inconsistent with it, eg a radially expanding pattern with backward motion. Results indicate that humans are more sensitive to motion-in-depth optic-flow stimuli when they are combined with complementary vestibular signals than when they are combined with conflicting vestibular signals. These results indicate that in humans, like in nonhuman primates, there is perceptual integration of visual and vestibular signals. PMID:21180352

  14. Mixing between hyporheic flow cells and upwelling groundwater: laboratory simulations and implications for mixing-dependent reactions

    NASA Astrophysics Data System (ADS)

    Hester, E. T.; Nida, A.

    2014-12-01

    The hyporheic zone is the region where surface water and groundwater interact beneath and adjacent to stream and river systems. The hyporheic zone has been shown to affect water quality constituents such as heat, pollutants, and nutrients in this interfacial region. Recent modeling studies have shown that some compounds upwelling from groundwater toward surface water only react when water originating in surface water and groundwater mix at the edge of the hyporheic zone. These "mixing-dependent" reactions may be important for addressing upwelling pollution, yet depend on the extent of the mixing zone. Recent modeling studies have also shown this mixing zone to be thin, but this has not been confirmed in lab or field studies. Our current study took the first step toward such confirmation by simulating mixing between hyporheic flow cells and upwelling groundwater in a 1.7 m x 1m flow-through laboratory sediment mesocosm. We used tracer dyes and digital photographs taken through the glass wall of the mesocosm to quantify mixing zone thickness. We varied key hydraulic controls such as the surface water head drop that drives the hyporheic flow cells. Steady-state results confirm the thin mixing zones predicted by the earlier modeling. Mixing zone length increases with increasing surface water head drop, but mixing zone thickness appears to remain relatively constant. Furthermore, if the head drop in surface water changes rapidly, the mixing zone moves through riverbed sediments but does not appear to change appreciably in thickness. As a result, we conclude that mixing zones are probably thin under a range of field conditions. This has implications for one common definition of the hyporheic zone as an area of substantial mixing of surface water and groundwater. Thin mixing zones also may limit mixing-dependent reactions of upwelling contaminants, which bears further study.

  15. 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

  16. Enhancing Safety Of Nuclear Waste Disposal By Exploiting Regional Groundwater Flow: The Recharge Area Concept

    NASA Astrophysics Data System (ADS)

    Tóth, József; Sheng, Grant

    1996-04-01

    The Recharge Area Concept is the proposition that in Canadian-Shield type natural environments recharge areas of regional groundwater flow systems are superior for high-level nuclear waste repositories to other types of groundwater flow regimes, especially to areas of groundwater discharge. This conclusion is reached from an analysis of basinal groundwater flow models. The calculations were made for a two-dimensional flank of a fully saturated topographic basin, 20 km long and 4 km deep, in which groundwater is driven by gravity. Variants of hydraulic-conductivity distributions were considered: 1) homogeneous; 2) stratified; and 3) stratified-faulted. The faults' attitudes were changed by steps from vertical to horizontal for different variants. The model is assumed conceptually to represent the crystalline-rock environment of the Canadian Shield. The hydrogeologic performances of hypothetical repositories placed 500 m deep in the recharge and discharge areas were characterized by thirteen parameters. The principal advantages of recharge- over discharge-area locations are: 1) longer travel paths and return-flow times from repository to surface; 2) robustness of predicted values of performance parameters; 3) field-verifiability of favourable hydrogeologic conditions (amounting to an implicit validation of the calculated minimum values of return-flow times); 4) site acceptance based on quantifiable and observable flow-controlling parameters; and 5) simple logistics and favourable economics of site selection and screening. As a by-product of modeling, it is demonstrated that the presence of old water is not an indication of stagnancy.

  17. 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.

  18. Tracing Groundwater Flow on a Barrier Island in the North-east Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Reide Corbett, D.; Dillon, K.; Burnett, W.

    2000-08-01

    Groundwater flow on St. George Island, a barrier island in the north-east Gulf of Mexico, was monitored downfield from wastewater systems using artificial tracer techniques. Sulphur hexafluoride and fluorescein dye were used to determine groundwater flow velocity, hydraulic conductivity, and dispersivity at selected sites on the island. Monthly hydraulic head measurements illustrate the aquifer's dependence on recharge associated with rainfall. However, during periods of little rain, tidal stage also influences the direction and magnitude of groundwater flow within approximately 30 m of the waters edge. Estimated hydraulic conductivities ranged from 3 to 180 m day -1, with an overall estimate of 36 m day -1. Groundwater tracers showed very little dilution and calculated longitudinal dispersivities were approximately 0·1 to 0·5 m, which is in the same range as previous studies of sandy aquifers. The total groundwater flux into adjacent Apalachicola Bay was also evaluated using two independent techniques. Darcy's law was applied using an estimated cross sectional area and the experimental horizontal transport rates to estimate the volumetric flow. In addition, a simple water balance calculation was used, which accounted for all known sources and sinks of water to the aquifer. The two independent approaches agreed very well, with an estimated groundwater flux from the surficial aquifer to Apalachicola Bay between 1-9×10 6 m 3 year -1.

  19. Groundwater flows in weathered crystalline rocks: Impact of piezometric variations and depth-dependent fracture connectivity

    NASA Astrophysics Data System (ADS)

    Guihéneuf, N.; Boisson, A.; Bour, O.; Dewandel, B.; Perrin, J.; Dausse, A.; Viossanges, M.; Chandra, S.; Ahmed, S.; Maréchal, J. C.

    2014-04-01

    Groundwater in shallow weathered and fractured crystalline rock aquifers is often the only perennial water resource, especially in semi-arid region such as Southern India. Understanding groundwater flows in such a context is of prime importance for sustainable aquifer management. Here, we describe a detailed study of fracture properties and relate the hydraulic connectivity of fractures to groundwater flows at local and watershed scales. Investigations were carried out at a dedicated Experimental Hydrogeological Park in Andhra Pradesh (Southern India) where a large network of observation boreholes has been set up. Twenty-height boreholes have been drilled in a small area of about 18,000 m2 in which borehole loggings and hydraulic tests were carried out to locate the main flowing fractured zones and investigate fractures connectivity. Several hydraulic tests (nineteen slug tests and three pumping tests) performed under two water level conditions revealed contrasting behavior. Under high water level conditions, the interface including the bottom of the saprolite and the first flowing fractured zone in the upper part of the granite controls groundwater flows at the watershed-scale. Under low water level conditions, the aquifer is characterized by lateral compartmentalization due to a decrease in the number of flowing fractures with depth. Depending on the water level conditions, the aquifer shifts from a watershed flow system to independent local flow systems. A conceptual groundwater flow model, which includes depth-dependent fracture connectivity, is proposed to illustrate this contrasting hydrological behavior. Implications for watershed hydrology, groundwater chemistry and aquifer vulnerability are also discussed.

  20. Application of boundary-fitted coordinate (BFC) transformations to groundwater flow and transport modeling

    SciTech Connect

    Lee, K.K.

    1992-01-01

    A numerical method is presented to simulate groundwater flow and transport using the Boundary-Fitted Coordinate (BFC) systems approach initially developed for aerodynamics. An irregularly-shaped physical domain is transformed to a simple computational domain with uniform grids. Governing equations defined in the physical domain are transformed into the computational domain, wherein all transformed equations are solved by the Finite Difference Method (FDM). This study developed three FORTRAN 77 computer programs: (1) BFCGW, which simulates groundwater flow and transport, (2) SEEPAGE, which simulates free-surface and seepage face, and (3) Q3D, which simulates multi-layered flow. A series of plotting programs using [open quotes]DISSPLA,[close quotes] an IBM FORTRAN graphics package, was also developed to plot grid lines, contour lines, and flow vectors in an irregularly-shaped physical domain with non-uniform grids. Each of the three programs was verified by solving an idealized problem for which the analytical solution was known and/or a realistic problem for which field measurements could be obtained. The computer program BFCGW was employed to simulate an idealized well flow in a triangular physical domain and actual groundwater flows in the area of West Lafayette, Indiana. The numerical solutions in both cases closely matched the analytical solutions and/or numerical simulations by other computer codes such as AQUA and MODFLOW. The program BFCGW performs rotation and stretching of local coordinates prior to BFC transformations to simulate heterogeneous and anisotropic groundwater flow. The rotation and stretching technique simplifies transformed governing equations of anisotropic groundwater flow. With the program BFCGW, the groundwater flow and the transport equations are solved sequentially to simulate solute concentration distributions.

  1. Regional ground-water flow in the Lower Peninsula of Michigan

    SciTech Connect

    Grannemann, N.G.; Huffman, G.C. )

    1994-04-01

    A steady-state, numerical model is being developed to simulate groundwater flow in four regional aquifers in Michigan's Lower Peninsula. The uppermost layer in the model simulates flow in the glaciofluvial aquifer and the second layer simulates flow in the Saginaw aquifer, both of which contain freshwater. The lower two modeled units simulate flow in the Parma-Bayport and Marshall aquifers, both of which contain saline water or brine, except at or near their subcrop, where they contain freshwater. The US Geological Survey's Modular Model (MODFLOW) was modified to simulate variable-density groundwater flow in the lower two aquifers by assuming that groundwater density and viscosity differ from place to place but do not change over time. The model simulates groundwater conditions prior to large-scale withdrawals from the aquifer. Boundaries for the model include constant-head boundaries at the shorelines of Lakes Michigan, Huron, St. Clair, and Erie, as well as the St. Clair and Detroit Rivers. The southern boundary is simulated as a no-flow condition along several major stream divides in Michigan and Indiana. Recharge to the glaciofluvial aquifer is estimated to range from 0.2 to 22 inches per year and averages 8.4 inches per year. Regional groundwater flow occurs in areas where the bedrock aquifers are confined and in parts of the glaciofluvial aquifer, such as in the north-central part of the Lower Peninsula. Regional discharge primarily occurs to Saginaw Bay and to streams in the Saginaw and Michigan Lowlands. Parts of the Grand and Maple rivers may also receive discharge on a regional scale. Local flow systems control the direction and rate of groundwater flow in areas where aquifers are unconfined or hydraulically connected to overlying glacial deposits.

  2. Analytical solutions for two-dimensional groundwater flow with subsurface drainage tiles

    NASA Astrophysics Data System (ADS)

    Liang, Xiuyu; Zhang, You-Kuan; Schilling, Keith E.

    2015-02-01

    The tile drainage problem in an unconfined aquifer was investigated. A mathematical model was established that describes two-dimensional groundwater flow in an unconfined aquifer near a river with a linearized Boussinesq equation, time-dependent sources and a sloped tile. Analytical solutions for groundwater level and discharge were derived and used to compare hydrologic conditions in a system with and without tile (natural drainage). We found that the spatial and temporal variations of groundwater level and discharge were significantly altered by the presence of drainage tile. In an aquifer with tile drainage, the groundwater level was lower and total groundwater discharge to the river increased compared to an aquifer with no tile. Application of the solutions to a synthetic case demonstrates that the analytical solutions derived can be used to quantify effect of tiles on nitrate loads in the baseflow of a river and assess the effectiveness of various conservation practices.

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

    SciTech Connect

    B. Arnold; T. Corbet

    2001-12-18

    The purpose of the flow boundary conditions analysis is to provide specified-flux boundary conditions for the saturated zone (SZ) site-scale flow and transport model. This analysis is designed to use existing modeling and analysis results as the basis for estimated groundwater flow rates into the SZ site-scale model domain, both as recharge at the upper (water table) boundary and as underflow at the lateral boundaries. The objective is to provide consistency at the boundaries between the SZ site-scale flow model and other groundwater flow models. The scope of this analysis includes extraction of the volumetric groundwater flow rates simulated by the SZ regional-scale flow model to occur at the lateral boundaries of the SZ site-scale flow model and the internal qualification of the regional-scale model for use in this analysis model report (AMR). In addition, the scope includes compilation of information on the recharge boundary condition taken from three sources: (1) distributed recharge as taken from the SZ regional-scale flow model, (2) recharge below the area of the unsaturated zone (UZ) site-scale flow model, and (3) focused recharge along the Fortymile Wash channel.

  4. 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

  5. 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.

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

    USGS Publications Warehouse

    Gerhart, J.M.

    1984-01-01

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

  7. 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...

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    Pimentel, Elizabeth T.; Hamza, Valiya M.

    2012-08-01

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

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

    USGS Publications Warehouse

    Buxton, Herbert T.; Modica, Edward

    1992-01-01

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

  14. 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...

  15. Simulation of ground-water flow, contributing recharge areas, and ground-water travel time in the Missouri River alluvial aquifer near Ft. Leavenworth, Kansas

    USGS Publications Warehouse

    Kelly, Brian P.

    2004-01-01

    field is affected by changes in river stage and pumping rates and by the location of the well or well field with respect to the major rivers, alluvial valley walls, and other pumping wells. The shapes of the simulated contributing recharge areas for the well fields in the study area are elongated in the upstream direction for all well-pumping/river-stage scenarios. The capture of ground water by the pumping wells as it moved downgradient toward the Missouri River caused the long up-valley extent of the contributing recharge areas. Recharge to the Iatan and Weston well fields primarily is from precipitation and surface runoff from the surrounding uplands because the contributing recharge area does not intersect the Missouri River for any well-pumping/river-stage scenarios. Recharge to the Leavenworth and Ft. Leavenworth well fields is from precipitation, surface runoff from the surrounding uplands, and the Missouri River because the contributing recharge area intersects these boundaries for all well-pumping/river-stage scenarios. Particle tracking analysis indicated ground water from the three contaminated sites was captured by the Ft. Leavenworth well field for all well-pumping/river-stage scenarios. Ground-water travel times to the Ft. Leavenworth well field for average well-pumping/river-stage scenario ranged from about 33 years for the closest contamination site to about 71 years for the farthest contamination site. Ground-water flow was induced below the Missouri River by the Ft. Leavenworth and Leavenworth well fields for all well-pumping/river-stage scenarios.

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

    USGS Publications Warehouse

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

    2000-01-01

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

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

    SciTech Connect

    Not Available

    1992-05-15

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

  18. Ground-water flow and water quality in the sand aquifer of Long Beach Peninsula, Washington

    USGS Publications Warehouse

    Thomas, B.E.

    1995-01-01

    This report describes a study that was undertaken to improve the understanding of ground-water flow and water quality in the coastal sand aquifer of the Long Beach Peninsula of southwestern Washington. Data collected for the study include monthly water levels at 103 wells and 28 surface-water sites during 1992, and water-quality samples from about 40 wells and 13 surface-water sites in February and July 1992. Ground water generally flows at right angles to a ground-water divide along the spine of the low-lying peninsula. Historical water-level data indicate that there was no long-term decline in the water table from 1974 to 1992. The water quality of shallow ground water was generally good with a few local problems. Natural concentrations of dissolved iron were higher than 0.3 milligrams per liter in about one-third of the samples. The dissolved-solids concentrations were generally low, with a range of 56 to 218 milligrams per liter. No appreciable amount of seawater has intruded into the sand aquifer, chloride concentrations were low, with a maximum of 52 milligrams per liter. Agricultural activities do not appear to have significantly affected the quality of ground water. Concentrations of nutrients were low in the cranberry-growing areas, and selected pesticides were not found above the analytical detection limits. Septic systems probably caused an increase in the concentration of nitrate from medians of less than 0.05 milligrams per liter in areas of low population density to 0.74 milligrams per liter in areas of high density.

  19. L'aquifère du bassin de la Mamora, Maroc: geometrie et ecoulements souterrainsThe aquifer of the Mamora Basin, Morocco: geometry and groundwater flow

    NASA Astrophysics Data System (ADS)

    Zouhri, L.

    2001-05-01

    The Mamora aquifer, in the northern Moroccan Meseta, constitutes the main regional water resource. Its impermeable basement is mostly composed of blue marls. The lithostratigraphy of the basin aquifer is characterised by a sequence of sandstones, sandy limestones, conglomerates and sandy clays. The structure of the basement of the Mamora aquifer, deduced from electrical resistivity measurements, allowed the hydrogeological behaviour of the reservoir, and the direction of the groundwater flow, to be established. The combination of the lithological, morphological, piezometric, geophysical and structural investigations revealed a northward thickening of the substrate with groundwater flow towards the Rharb (to the north) and towards the Atlantic Ocean (northwest). This 'multicriteria' approach enabled a structural model to be defined, which correlated well with the aquifer geometry and the groundwater flow. The variability of the hydrogeological units, and the northward thickening of the sedimentary facies, were controlled by northeast-southwest orientated faults, which affect their impermeability.

  20. Quasi 3D modeling of water flow in vadose zone and groundwater

    NASA Astrophysics Data System (ADS)

    Kuznetsov, M.; Yakirevich, A.; Pachepsky, Y. A.; Sorek, S.; Weisbrod, N.

    2012-07-01

    SummaryThe complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One habitual simplification is based on the assumption that lateral flow and transport in unsaturated zone are not significant unless the capillary fringe is involved. In such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1D phenomenon, whereas the flow and transport through groundwater are viewed as 2D or 3D phenomena. A new approach for a numerical scheme for 3D variably saturated flow using quasi 3D Richards' equation and finite difference scheme is presented. The corresponding numerical algorithm and the QUASI-3D computer code were developed. Results of the groundwater level simulations were compared with transient laboratory experimental data for 2D data constant-flux infiltration, quasi-3D HYDRUS-MODFLOW numerical model and a FULL-3D numerical model using Richards' equation. Hypothetical 3D examples of infiltration, pumping and groundwater mound dissipation for different spatial-time scales are presented. Water flow simulation for the Alto Piura aquifer (Peru) demonstrates the QUASI-3D model application at the regional scale. Computationally the QUASI-3D code was found to be more efficient by an order of 10-300%, while being accurate with respect to the benchmark fully 3D variable saturation code, when the capillary fringe was considered.

  1. 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.

  2. Evidence for deep groundwater flow and convective heat transport in mountainous terrain, Delta County, Colorado, USA

    NASA Astrophysics Data System (ADS)

    Lazear, Gregory D.

    2006-12-01

    The Tongue Creek watershed lies on the south flank of Grand Mesa in western Colorado, USA and is a site with 1.5 km of topographic relief, heat flow of 100 mW/m2, thermal conductivity of 3.3 W m-1 °C-1, hydraulic conductivity of 10-8 m/s, a water table that closely follows surface topography, and groundwater temperatures 3-15°C above mean surface temperatures. These data suggest that convective heat transport by groundwater flow has modified the thermal regime of the site. Steady state three-dimensional numerical simulations of heat flow, groundwater flow, and convective transport were used to model these thermal and hydrological data. The simulations provided estimates for the scale of hydraulic conductivity and bedrock base flow discharge within the watershed. The numerical models show that (1) complex three-dimensional flow systems develop with a range of scales from tens of meters to tens of kilometers; (2) mapped springs are frequently found at locations where contours of hydraulic head indicate strong vertical flow at the water table, and; (3) the distribution of groundwater temperatures in water wells as a function of surface elevation is predicted by the model.

  3. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  5. Numerical study of groundwater flow cycling controlled by seawater/freshwater interaction in a coastal karst aquifer through conduit network using CFPv2

    NASA Astrophysics Data System (ADS)

    Xu, Zexuan; Hu, Bill X.; Davis, Hal; Kish, Stephen

    2015-11-01

    In this study, a groundwater flow cycling in a karst springshed and an interaction between two springs, Spring Creek Springs and Wakulla Springs, through a subground conduit network are numerically simulated using CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). The Spring Creek Springs and Wakulla Springs, located in a marine estuary and 11 miles inland, respectively, are two major groundwater discharge spots in the Woodville Karst Plain (WKP), North Florida, USA. A three-phase conceptual model of groundwater flow cycling between the two springs and surface water recharge from a major surface creek (Lost Creek) was proposed in various rainfall conditions. A high permeable subground karst conduit network connecting the two springs was found by tracer tests and cave diving. Flow rate of discharge, salinity, sea level and tide height at Spring Creek Springs could significantly affect groundwater discharge and water stage at Wakulla Springs simultaneously. Based on the conceptual model, a numerical hybrid discrete-continuum groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flows in conduits and flow exchange between conduits and porous medium are implemented in the hybrid coupling numerical model. Time-variable salinity and equivalent freshwater head boundary conditions at the submarine spring as well as changing recharges have significant impacts on seawater/freshwater interaction and springs' discharges. The developed numerical model is used to simulate the dynamic hydrological process and quantitatively represent the three-phase conceptual model from June 2007 to June 2010. Simulated results of two springs' discharges match reasonably well to measurements with correlation coefficients 0.891 and 0.866 at Spring Creeks Springs and Wakulla Springs, respectively. The impacts of sea level rise on regional groundwater flow field and relationship between the inland springs and submarine springs are

  6. Numerical study of groundwater flow cycling controlled by seawater/freshwater interaction in a coastal karst aquifer through conduit network using CFPv2.

    PubMed

    Xu, Zexuan; Hu, Bill X; Davis, Hal; Kish, Stephen

    2015-11-01

    In this study, a groundwater flow cycling in a karst springshed and an interaction between two springs, Spring Creek Springs and Wakulla Springs, through a subground conduit network are numerically simulated using CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). The Spring Creek Springs and Wakulla Springs, located in a marine estuary and 11 miles inland, respectively, are two major groundwater discharge spots in the Woodville Karst Plain (WKP), North Florida, USA. A three-phase conceptual model of groundwater flow cycling between the two springs and surface water recharge from a major surface creek (Lost Creek) was proposed in various rainfall conditions. A high permeable subground karst conduit network connecting the two springs was found by tracer tests and cave diving. Flow rate of discharge, salinity, sea level and tide height at Spring Creek Springs could significantly affect groundwater discharge and water stage at Wakulla Springs simultaneously. Based on the conceptual model, a numerical hybrid discrete-continuum groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flows in conduits and flow exchange between conduits and porous medium are implemented in the hybrid coupling numerical model. Time-variable salinity and equivalent freshwater head boundary conditions at the submarine spring as well as changing recharges have significant impacts on seawater/freshwater interaction and springs' discharges. The developed numerical model is used to simulate the dynamic hydrological process and quantitatively represent the three-phase conceptual model from June 2007 to June 2010. Simulated results of two springs' discharges match reasonably well to measurements with correlation coefficients 0.891 and 0.866 at Spring Creeks Springs and Wakulla Springs, respectively. The impacts of sea level rise on regional groundwater flow field and relationship between the inland springs and submarine springs are

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

    SciTech Connect

    Ballard, S.; Gibson, J.

    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.

  8. Application of MODFLOW and geographic information system to groundwater flow simulation in North China Plain, China

    NASA Astrophysics Data System (ADS)

    Wang, Shiqin; Shao, Jingli; Song, Xianfang; Zhang, Yongbo; Huo, Zhibin; Zhou, Xiaoyuan

    2008-10-01

    MODFLOW is a groundwater modeling program. It can be compiled and remedied according to the practical applications. Because of its structure and fixed data format, MODFLOW can be integrated with Geographic Information Systems (GIS) technology for water resource management. The North China Plain (NCP), which is the politic, economic and cultural center of China, is facing with water resources shortage and water pollution. Groundwater is the main water resource for industrial, agricultural and domestic usage. It is necessary to evaluate the groundwater resources of the NCP as an entire aquifer system. With the development of computer and internet information technology it is also necessary to integrate the groundwater model with the GIS technology. Because the geological and hydrogeological data in the NCP was mainly in MAPGIS format, the powerful function of GIS of disposing of and analyzing spatial data and computer languages such as Visual C and Visual Basic were used to define the relationship between the original data and model data. After analyzing the geological and hydrogeological conditions of the NCP, the groundwater flow numerical simulation modeling was constructed with MODFLOW. On the basis of GIS, a dynamic evaluation system for groundwater resources under the internet circumstance was completed. During the process of constructing the groundwater model, a water budget was analyzed, which showed a negative budget in the NCP. The simulation period was from 1 January 2002 to 31 December 2003. During this period, the total recharge of the groundwater system was 49,374 × 106 m3 and the total discharge was 56,530 × 106 m3 the budget deficit was -7,156 × 106 m3. In this integrated system, the original data including graphs and attribution data could be stored in the database. When the process of evaluating and predicting groundwater flow was started, these data were transformed into files that the core program of MODFLOW could read. The calculated water

  9. Non-intrusive characterization methods for wastewater-affected groundwater plumes discharging to an alpine lake.

    PubMed

    Roy, James W; Robillard, Jasen M; Watson, Susan B; Hayashi, Masaki

    2009-02-01

    Streams and lakes in rocky environments are especially susceptible to nutrient loading from wastewater-affected groundwater plumes. However, the use of invasive techniques such as drilling wells, installing piezometers or seepage meters, to detect and characterize these plumes can be prohibitive. In this work, we report on the use of four non-intrusive methods for this purpose at a site in the Rocky Mountains. The methods included non-invasive geophysical surveys of subsurface electrical conductivity (EC), in-situ EC measurement of discharging groundwater at the lake-sediment interface, shoreline water sampling and nutrient analysis, and shoreline periphyton sampling and analysis of biomass and taxa relative abundance. The geophysical surveys were able to detect and delineate two high-EC plumes, with capacitively coupled ERI (OhmMapper) providing detailed two-dimensional images. In situ measurements at the suspected discharge locations confirmed the presence of high-EC water in the two plumes and corroborated their spatial extent. The nutrient and periphyton results showed that only one of the two high-EC plumes posed a current eutrophication threat, with elevated nitrogen and phosphorus levels, high localized periphyton biomass and major shifts in taxonomic composition to taxa that are commonly associated with anthropogenic nutrient loading. This study highlights the need to use non-intrusive methods in combination, with geophysical and water EC-based methods used for initial detection of wastewater-affected groundwater plumes, and nutrient or periphyton sampling used to characterize their ecological effects. PMID:18253851

  10. Paleohydrological Information from Profiles in Pore Water of Holocene Low-Permeability Cores and Groundwater Flow Simulation, Lake Kasumigaura, Japan

    NASA Astrophysics Data System (ADS)

    Takamoto, N.; Shimada, J.

    2014-12-01

    The paleohydrological information can become important to predict hydrological conditions in the future. In Japan, which hydrologically is characterized by relatively small catchment scales with steep relief of topography under humid temperate climatic conditions, the residence time of the groundwater should be relatively short. Thus the paleohydrological information preserved in the groundwater aquifer should also be limited compared with the continental aquifer. However, regarding groundwater in clay and silt sediments have low-permeability characteristic, archiving the paleohydrologic information at the time of deposition is expected.  Therefore, in this study, cores were drilled into Holocene clay and silt deposits (Site K-1 and Site K-2) in the Lake Kasumigaurain Japan, where the depositional rate 10,000 years ago was rapid and it has been affected strongly by sea level changes including transgression and regression. By using the obtained core samples and extracted pore water from the cores, paleohydrologic information was investigated, and it was tried to understand hydrologic environments at the study area during a Holocene. In addition, groundwater flow and solute transport simulation were conducted to reproduce profiles of pore water.  Results of investigation show that the profiles of pore water contents reflect sea level change and the difference in hydrological environment at that time at each site. The content of the paleo-brackish water in the culmination of transgression was about 14,000 mg/l in Cl-, -13.0‰ in δD and -2.6‰ in δ18O. It is allowed better understanding paleohydrological information by studying not only inorganic chemistry contents and stable isotopes of pore water and also the diatom fossils and groundwater flow and solute transport simulation. We will characterize the paleohydrological information of the study area acquired by those investigations and analysis.

  11. Analysis and simulation of ground-water flow in Lake Wales Ridge and adjacent areas of central Florida

    USGS Publications Warehouse

    Yobbi, Dann K.

    1996-01-01

    final test of model calibration was conducted by successfully simulating transient conditions for the period October 1988 through September 1989. Altitudes of the water table, base of the surficial aquifer, riverbed conductances, confining-unit leakances, aquifer transmissivities, and net recharge and discharge rates were determine during calibration. Steady- state and transient simulations reasonably approximated measured aquifer heads and lake levels. Residuals were within the established calibration criteria that required 68 percent of all simulated heads to be within + - 2 feet of observed surficial aquifer heads and lake levels and + - 5 feet of observed intermediate and Upper Floridan aquifer heads. Simulation of streamflow was poor, probably due to the scale of the model and regulated streamflow conditions. Simulation indicates a marked difference between the ground-water flow rates of September 1989 (steady-state conditions, end of wet season) and May 1990 (large pumpage, end of dry season) in million gallons per day: September May 1989 1990 Pumping rate 126 486 Donward leakage (into 367 564 Upper Floridan aquifer) Streamflow 67 13 Net lateral boundary flow 218 115 Total discharge (excluding 479 626 evapotranspiration The calibrated flow model was used to simulate the short-term (one year) effects of 1990 water year pumpage (349 Mgal/d) on the September 1989 ground- water flow system in response to five different pumping schemes: (2) no pumpage, (2) no public supply pumpage, (3) no industrial pumpage, (4) no agricultural pumpage, and (5) no regional pumping outside the Water Use Caution Area. Simulation of no pumpage indicated maximum aquifer head rises of about 2 feet in the surficial aquifer and lakes, about 12 feet in the intermediate aquifer and about 16 feet in the Upper Floridan aquifer. The high rate recharge areas along the Lake Wales Ridge are most affect

  12. 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.

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

    USGS Publications Warehouse

    Sanford, R.F.

    1994-01-01

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

  14. Summary of hydrogeologic controls on ground-water flow at the Nevada Test Site, Nye County, Nevada

    SciTech Connect

    Laczniak, R.J.; Cole, J.C.; Sawyer, D.A.; Trudeau, D.A.

    1996-07-01

    The underground testing of nuclear devices has generated substantial volumes of radioactive and other chemical contaminants below ground at the Nevada Test Site (NTS). Many of the more radioactive contaminants are highly toxic and are known to persist in the environment for thousands of years. In response to concerns about potential health hazards, the US Department of Energy, under its Environmental Restoration Program, has made NTS the subject of a long-term investigation. Efforts will assess whether byproducts of underground testing pose a potential hazard to the health and safety of the public and, if necessary, will evaluate and implement steps to remediate any of the identified dangers. Ground-water flow is the primary mechanism by which contaminants can be transported significant distances away from the initial point of injection. Flow paths between contaminant sources and potential receptors are separated by remote areas that span tens of miles. The diversity and structural complexity of the rocks along these flow paths complicates the hydrology of the region. Although the hydrology has been studied in some detail, much still remains uncertain about flow rates and directions through the fractured-rock aquifers that transmit water great distances across this arid region. Unique to the hydrology of NTS are the effects of underground testing, which severely alter local rock characteristics and affect hydrologic conditions throughout the region. This report summarizes what is known and inferred about ground-water flow throughout the NTS region. The report identifies and updates what is known about some of the major controls on ground-water flow, highlights some of the uncertainties in the current understanding, and prioritizes some of the technical needs as related to the Environmental Restoration Program. 113 refs.

  15. 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

    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

  16. 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.

  17. 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.

  18. Ground-water flow and solute transport at a municipal landfill site on Long Island, New York

    USGS Publications Warehouse

    Wexler, E.J.

    1988-01-01

    Hydrogeology and water quality in a 4 sq mi area surrounding the Brookhaven landfill site in the Town of Brookhaven, New York, were studied in 1981-83. The 60-acre sanitary landfill at the site was excavated in highly permeable glacial outwash that forms the upper glacial aquifer and is lined with a polyvinyl chloride membrane. Groundwater beneath the site is under water table conditions and flows southeast at approximately 1.1 ft/day. Samples from wells downgradient indicate that leachate has entered the aquifer despite the liner. A plume 3,700 ft long , 2,400 ft wide, and at least 90 ft thick was delineated based on specific conductance data. Water quality in the Magothy aquifer and in Beaverdam Creek, a groundwater fed stream 2,000 ft southeast of the landfill site, does not appear to be affected. (USGS)

  19. Study of electrokinetic effects to quantify groundwater flow

    SciTech Connect

    Brown, S.R.; Haupt, R.W.

    1997-04-01

    An experimental study of electrokinetic effects (streaming potential) in earth materials was undertaken. The objective was to evaluate the measurement of electrokinetic effects as a method of monitoring and predicting the movement of groundwater, contaminant plumes, and other fluids in the subsurface. The laboratory experiments verified that the electrokinetic effects in earth materials are prominent, repeatable, and can be described well to first order by a pair of coupled differential equations.

  20. Simulation of groundwater flow and analysis of the effects of water-management options in the North Platte Natural Resources District, Nebraska

    USGS Publications Warehouse

    Peterson, Steven M.; Flynn, Amanda T.; Vrabel, Joseph; Ryter, Derek W.

    2015-01-01

    The calibrated groundwater-flow model was used with the Groundwater-Management Process for the 2005 version of the U.S. Geological Survey modular three-dimensional groundwater model, MODFLOW–2005, to provide a tool for the NPNRD to better understand how water-management decisions could affect stream base flows of the North Platte River at Bridgeport, Nebr., streamgage in a future period from 2008 to 2019 under varying climatic conditions. The simulation-optimization model was constructed to analyze the maximum increase in simulated stream base flow that could be obtained with the minimum amount of reductions in groundwater withdrawals for irrigation. A second analysis extended the first to analyze the simulated base-flow benefit of groundwater withdrawals along with application of intentional recharge, that is, water from canals being released into rangeland areas with sandy soils. With optimized groundwater withdrawals and intentional recharge, the maximum simulated stream base flow was 15–23 cubic feet per second (ft3/s) greater than with no management at all, or 10–15 ft3/s larger than with managed groundwater withdrawals only. These results indicate not only the amount that simulated stream base flow can be increased by these management options, but also the locations where the management options provide the most or least benefit to the simulated stream base flow. For the analyses in this report, simulated base flow was best optimized by reductions in groundwater withdrawals north of the North Platte River and in the western half of the area. Intentional recharge sites selected by the optimization had a complex distribution but were more likely to be closer to the North Platte River or its tributaries. Future users of the simulation-optimization model will be able to modify the input files as to type, location, and timing of constraints, decision variables of groundwater withdrawals by zone, and other variables to explore other feasible management

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

    USGS Publications Warehouse

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

    1998-01-01

    of an area near the center of the modeled area where the horizontal hydraulic conductivity is 170 feet per day. Transmissivity of the lower aquifer increases generally from southwest to northeast; transmissivity values range from near 0 where the lower aquifer is absent to 57,000 square feet per day and average about 8,100 square feet per day. The vertical hydraulic conductivity of the confining unit is 0.07 feet per day; the vertical conductivity of the streambeds commonly is 1.0 foot per day and ranges from 0.05 foot per day to 50 feet per day. The areal recharge rate to the outwash deposits was determined by a base-flow separation technique to be 16 inches per year, and the areal recharge rate to the till was assumed to be 4 inches per year. A two-layer digital model was used to simulate flow in the ground-water system. The model was calibrated on the basis of historical water-use data, water-level records, and gain/loss data for streams during May and June 1979. The model was recalibrated with water-use data and water-level records from 1988. For 1979 data, 49 percent of the inflow to the model area is from precipitation and 46 percent is ground-water inflow across the model boundaries. Most of the ground-water inflow across the model boundary is from the north and east, which corresponds to high values of transmissivity?as high as 57,000 feet squared per day?in the model layers in the northern and eastern areas. Eighty-two percent of the ground-water discharge is to the streams; 5 percent of the ground-water discharge is to wells. Source areas and flow paths to the City of Elkhart public well fields are affected by the location of streams and the geology in the area. Flow to the North Well Field originates north-west of the well field, forms relatively straight flow paths, and moves southeast toward the well field and the St. Joseph River. Flow to the South Well Field begins mostly in the out-wash along Yellow Creek south of the well field, moves northward, and

  2. Quasi 3D modeling of water flow and solute transport in vadose zone and groundwater

    NASA Astrophysics Data System (ADS)

    Yakirevich, A.; Kuznetsov, M.; Weisbrod, N.; Pachepsky, Y. A.

    2013-12-01

    The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One commonly used simplification is based on the assumption that lateral flow and transport in unsaturated zone is insignificant unless the capillary fringe is involved. In such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1D phenomenon, whereas through groundwater they are viewed as 2D or 3D phenomena. A new approach for a numerical scheme for 3D variably saturated flow and transport is presented. A Quasi-3D approach allows representing flow in the 'vadose zone - aquifer' system by a series of 1D Richards' equations solved in variably-saturated zone and by 3D-saturated flow equation in groundwater (modified MODFLOW code). The 1D and 3D equations are coupled at the phreatic surface in a way that aquifer replenishment is calculated using the Richards' equation, and solving for the moving water table does not require definition of the specific yield parameter. The 3D advection-dispersion equation is solved in the entire domain by the MT3D code. Using implicit finite differences approximation to couple processes in the vadose zone and groundwater provides mass conservation and increase of computational efficiency. The above model was applied to simulate the impact of irrigation on groundwater salinity in the Alto Piura aquifer (Northern Peru). Studies on changing groundwater quality in arid and semi-arid lands show that irrigation return flow is one of the major factors contributing to aquifer salinization. Existing mathematical models do not account explicitly for the solute recycling during irrigation on a daily scale. Recycling occurs throughout the unsaturated and saturated zones, as function of the solute mass extracted from pumping wells. Salt concentration in irrigation water is calculated at each time step as a function of concentration of both surface water and groundwater

  3. 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

  4. A Numerical Study for Groundwater Flow, Heat and Solute Transport Associated with Operation of Open-loop Geothermal System in Alluvial Aquifer

    NASA Astrophysics Data System (ADS)

    Park, D. K.; Bae, G. O.; Lee, K. K.

    2014-12-01

    The open-loop geothermal system directly uses a relatively stable temperature of groundwater for cooling and heating in buildings and thus has been known as an eco-friendly, energy-saving, and cost-efficient technique. The facility for this system was installed at a site located near Paldang-dam in Han-river, Korea. Because of the well-developed alluvium, the site might be appropriate to application of this system requiring extraction and injection of a large amount of groundwater. A simple numerical experiment assuming various hydrogeologic conditions demonstrated that regional groundwater flow direction was the most important factor for efficient operation of facility in this site having a highly permeable layer. However, a comparison of river stage data and groundwater level measurements showed that the daily and seasonal controls of water level at Paldang-dam have had a critical influence on the regional groundwater flow in the site. Moreover, nitrate concentrations measured in the monitoring wells gave indication of the effect of agricultural activities around the facility on the groundwater quality. The facility operation, such as extraction and injection of groundwater, will obviously affect transport of the agricultural contaminant and, maybe, it will even cause serious problems in the normal operation. Particularly, the high-permeable layer in this aquifer must be a preferential path for quick spreadings of thermal and contaminant plumes. The objective of this study was to find an efficient, safe and stable operation plan of the open-loop geothermal system installed in this site having the complicated conditions of highly permeable layer, variable regional groundwater flow, and agricultural contamination. Numerical simulations for groundwater flow, heat and solute transport were carried out to analyze all the changes in groundwater level and flow, temperature, and quality according to the operation, respectively. Results showed that an operation plan for

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Slope instability in complex topography is generally controlled by the interaction between gravitationally induced stresses, 3D strengths, and 3D pore-fluid pressure fields produced by flowing groundwater. As an example of this complexity, coastal bluffs sculpted by landsliding commonly exhibit a progression of undulating headlands and re-entrants. In this landscape, stresses differ between headlands and re-entrants and 3D groundwater flow varies from vertical rainfall infiltration to lateral groundwater flow on lower permeability layers with subsequent discharge at the curved bluff faces. In plan view, groundwater flow converges in the re-entrant regions. To investigate relative slope instability induced by undulating topography, we couple the USGS 3D limit-equilibrium slope-stability model, SCOOPS, with the USGS 3D groundwater flow model, MODFLOW. By rapidly analyzing the stability of millions of potential failures, the SCOOPS model can determine relative slope stability throughout the 3D domain underlying a digital elevation model (DEM), and it can utilize both fully 3D distributions of pore-water pressure and material strength. The two models are linked by first computing a groundwater-flow field in MODFLOW, and then computing stability in SCOOPS using the pore-pressure field derived from groundwater flow. Using these two models, our analyses of 60m high coastal bluffs in Seattle, Washington showed augmented instability in topographic re-entrants given recharge from a rainy season. Here, increased recharge led to elevated perched water tables with enhanced effects in the re-entrants owing to convergence of groundwater flow. Stability in these areas was reduced about 80% compared to equivalent dry conditions. To further isolate these effects, we examined groundwater flow and stability in hypothetical landscapes composed of uniform and equally spaced, oscillating headlands and re-entrants with differing amplitudes. The landscapes had a constant slope for both

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

    USGS Publications Warehouse

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

    1989-01-01

    Under an interagency contractual agreement with the Agency for Toxic Substances and Disease Registration, the U.S. Geological Survey evaluated geologic and hydrogeologic data available for the Industrial Excess Landfill (IEL) site in Uniontown, Ohio. During previous studies, ground-water contaminations was detected in observation wells installed at the site and in residential wells near the site. Water levels recorded on drillers' logs from 279 wells were used to characterize the regional ground-water flow system in the area of the IEL site. On the basis of the gross lithologic differences between the unconsolidated glacial-drift material and the indurated bedrock, and the inferred differences in their hydraulic properties, the flow system in the area of the IEL site was divided into two regional aquifers: a shallow, unconfined glacial-drift aquifer and a deeper, semiconfined bedrock aquifer. About 33 percent of the drillers' logs were from wells completed in the glacial-drift aquifer, whereas 67 percent were from wells completed in the bedrock aquifer. A composite potentiometric-surface map of the glacial drift aquifer shows that the IEL site appears to straddle a prominent ground-water ridge that trends northeast-southwest. Ground water flows radially away from this ridge, primarily to the northwest and to the southeast; as a result flow in the glacial-drift aquifer as the IEL site moves in a radial pattern away from the site in all directions. A composite, regional potentiometric-surface map of the bedrock aquifer shows a similar shows a similar elongated ground-water ridge trending northeast-southwest across the north-western corner of the IEL site; however, it does not appear that the IEL site straddles the ground-water ridge in the bedrock potentiometric surface. As a consequence of the radial-type of flow pattern in the glacial-drift aquifer at the IEL site, the direction of potential off-site movement of a contaminant at the IEL site, This radial type of

  8. 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

  9. Water scarcity, groundwater and base flow in Dutch catchments: effects of climate and human impact

    NASA Astrophysics Data System (ADS)

    Hendriks, D. M. D.; van Ek, R.; Kuijper, M. J. M.

    2012-04-01

    During recent years (2003, 2006 en 2008) water boards in the Netherlands have had to cope with drought and water scarcity. Because of human impacts in the area, like groundwater abstraction and extensive drainage, the upper parts of streams run dry during low precipitation periods. The lack of water is a risk for the environmental flow needs of the streams. In addition, agricultural areas encounter problems due to low groundwater levels and limited availability of water for spray irrigation. Such problems are likely to occur more frequent in the future, because of increasing frequency of dry spells, reduced water intake possibilities from large rivers and a higher demand for water for agriculture and other land use functions. Several studies have been carried out to investigate the possibilities for structural improvement of groundwater and base flow conditions, thereby improving the situation of agriculture and ecology (Hendriks et al., 2010; Kuijper et al., 2012). The effects of both climate change and unsustainable use of water resources on base flow were assessed at various scales. For this purpose, spatially distributed groundwater models with fine meshed grids (25x25 m) were used to simultaneously assess the effects of climate and human impacts on both groundwater conditions and surface water discharge. Climatic effects were assessed by comparison of meteorologically dry and average years, as well as through climate scenarios from the Royal Dutch Weather Service (KNMI). Human impacts were assessed by modeling various scenarios with reduced or increased drainage and groundwater abstraction, including a scenario of the undisturbed situation. Also, the impact of stream morphology was studied. The suitability of a new modeling approach (Van der Velde et al., 2009), allowing a fast assessment of discharge with high accuracy, was tested to improve discharge simulations from groundwater models. Model results show that extensive drainage systems have a large impact

  10. Calculating discharge of phosphorus and nitrogen with groundwater base flow to a small urban stream reach

    NASA Astrophysics Data System (ADS)

    Fitzgerald, Alex; Roy, James W.; Smith, James E.

    2015-09-01

    Elevated levels of nutrients, especially phosphorus, in urban streams can lead to eutrophication and general degradation of stream water quality. Contributions of phosphorus from groundwater have typically been assumed minor, though elevated concentrations have been associated with riparian areas and urban settings. The objective of this study was to investigate the importance of groundwater as a pathway for phosphorus and nitrogen input to a gaining urban stream. The stream at the 28-m study reach was 3-5 m wide and straight, flowing generally eastward, with a relatively smooth bottom of predominantly sand, with some areas of finer sediments and a few boulders. Temperature-based methods were used to estimate the groundwater flux distribution. Detailed concentration distributions in discharging groundwater were mapped using in-stream piezometers and diffusion-based peepers, and showed elevated levels of soluble reactive phosphorus (SRP) and ammonium compared to the stream (while nitrate levels were lower), especially along the south bank, where groundwater fluxes were lower and geochemically reducing conditions dominated. Field evidence suggests the ammonium may originate from nearby landfills, but that local sediments likely contribute the SRP. Ammonium and SRP mass discharges with groundwater were then estimated as the product of the respective concentration distributions and the groundwater flux distribution. These were determined as approximately 9 and 200 g d-1 for SRP and ammonium, respectively, which compares to stream mass discharges over the observed range of base flows of 20-1100 and 270-7600 g d-1, respectively. This suggests that groundwater from this small reach, and any similar areas along Dyment's Creek, has the potential to contribute substantially to the stream nutrient concentrations.

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

    USGS Publications Warehouse

    Long, Andrew J.; Valder, Joshua F.

    2011-01-01

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

  12. Groundwater as a nonpoint source of atrazine and deethylatrazine in a river during base flow conditions

    USGS Publications Warehouse

    Squillace, Paul J.; Thurman, E.M.; Furlong, Edward T.

    1993-01-01

    Alluvial groundwater adjacent to the main stem river is the principal nonpoint source of atrazine and deethylatrazine in the Cedar River of Iowa after the river has been in base flow conditions for 5 days. Between two sites along a 116-km reach of the Cedar River, tributaries contributed about 25% of the increase in the atrazine and deethylatrazine load, whereas groundwater from the alluvial aquifer contributed at least 75% of the increase in load. Within the study area, tributaries aggregate almost all of the discharge from tile drains, and yet the tributaries still only contribute 25% of the increase in loads in the main stem river. At an unfamned study site adjacent to the Cedar River, the sources of atrazine and deethylatrazine in the alluvial groundwater are bank storage of river water and groundwater recharge from areas distant from the river. Atrazine and deethylatrazine associated with bank storage water will provide larger concentrations to the river during early base flow conditions. After the depletion of bank storage, stable and smaller concentrations of atrazine and deethylatrazine, originating from groundwater recharge, continue to be discharged from the alluvial aquifer to the river; thus these results indicate that alluvial aquifers are an important nonpoint source of atrazine and deethylatrazine in rivers during base flow.

  13. 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

  14. Simulation of groundwater flow and hydrologic effects of groundwater withdrawals from the Kirkwood-Cohansey aquifer system in the Pinelands of southern New Jersey

    USGS Publications Warehouse

    Charles, Emmanuel G.; Nicholson, Robert S.

    2012-01-01

    flow. Pumping stresses at aquifer-test sites resulted in measurable drawdown in each observation well installed for the tests. The magnitude of drawdown in shallow wetland observation wells at the end of pumping ranged from 5.5 to 16.7 centimeters (cm). The stresses induced by the respective tests reduced the flow of the smallest stream (McDonalds Branch) by 75 percent and slightly reduced flow in a side channel of Morses Mill Stream, but did not measurably affect the flow of Morses Mill Stream or Albertson Brook. Results of aquifer-test simulations were used to refine the estimates of hydraulic properties used in the models and to confirm the ability of the model to replicate observed hydrologic responses to pumping. Steady-state sensitivity simulation results for a variety of single well locations and depths were used to define overall “best-case” (smallest effect on wetland water levels and base flow) and “worst-case” (greatest effect on wetland water levels and base flow) groundwater withdrawal configurations. “Best-case” configurations are those for which the extent of the wetland areas within a 1-kilometer (km) radius of the withdrawal well is minimized, the well is located at least 100 m and as far from wetland boundaries as possible, and the withdrawal is from a deep well (50–90 m deep). “Worst-case” configurations are those for which the extent of wetlands within a 1-km radius of the withdrawal well is maximized, the well is located 100 m or less from a wetland boundary, and the withdrawal is from a relatively shallow well (30–67 m deep). “Best-” and “worst-case” simulations were applied by locating hypothetical wells across the study areas and assigning groundwater withdrawals so that the sum of the withdrawals for the basin is equal to 5, 10, 15, and 30 percent of overall recharge. The results were compared to the results of simulations of no groundwater withdrawals. Results for withdrawals of 5 percent of recharge show that the

  15. 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

  16. 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

  17. Evaluating the Effects of Horizontal Spatial Discretization on Interflow in the Soil Zone Using the Richards and Groundwater Flow Equations

    NASA Astrophysics Data System (ADS)

    Henson, W.; Niswonger, R. G.

    2011-12-01

    In many mountainous regions, a large proportion of streamflow originates as shallow subsurface storm flow (interflow) within the shallow soils of hillslopes. Infiltration can accumulate to form perched groundwater within the upper few meters of the soil horizon that drains to streams through both macropores and soil-matrix. Richards Equation has become a commonly used governing equation for simulating interflow in regional-scale models. Recent research has shown that optimal vertical discretization for Richards Equation near land surface and the water table is much smaller than the discretization typically used in basin-scale hydrologic models, yet little is known about optimal horizontal discretization or potential effects of horizontal discretization on interflow solutions. Most of the work related to the effects of discretization on the solution of Richards Equation has focused on the vertical infiltration problem. This study evaluates horizontal spatial discretization effects on interflow predictions using 1) a modified version of GSFLOW and 2) VS2DT. The modified GSFLOW couples Smith-Parlange 1-D infiltration equations with 3-D unconfined groundwater flow equation, whereas VS2DT uses Richards Equation to represent infiltration and variably saturated flow. Interflow solutions and breakthrough at the stream were compared using a model domain similar to Vauclin and others (1979) with horizontal grid resolutions ranging from 0.05-5m and vertical resolutions ranging between 0.05-1m, with horizontal flow path lengths of 25m to the stream. Variable horizontal spatial resolutions affected VS2DT interflow solutions (RMSE up to 0.12) and interflow breakthrough at the stream, whereas GSFLOW solutions were well correlated (RMSE <0.052). Interflow breakthrough was delayed by up to 10 days with increasing resolution in VS2DT, whereas GSFLOW breakthrough was consistently the same day. Results indicate that the solution of Richards Equation for soil-zone interflow is much

  18. 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.

  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. Echo-acoustic flow affects flight in bats.

    PubMed

    Kugler, Kathrin; Greiter, Wolfgang; Luksch, Harald; Firzlaff, Uwe; Wiegrebe, Lutz

    2016-06-15

    Flying animals need to react fast to rapid changes in their environment. Visually guided animals use optic flow, generated by their movement through structured environments. Nocturnal bats cannot make use of optic flow, but rely mostly on echolocation. Here, we show that bats exploit echo-acoustic flow to negotiate flight through narrow passages. Specifically, bats' flight between lateral structures is significantly affected by the echo-acoustic salience of those structures, independent of their physical distance. This is true even though echolocation, unlike vision, provides explicit distance cues. Moreover, the bats reduced the echolocation sound levels in stronger flow, probably to compensate for the increased summary target strength of the lateral reflectors. However, bats did not reduce flight velocity under stronger echo-acoustic flow. Our results demonstrate that sensory flow is a ubiquitous principle for flight guidance, independent of the fundamentally different peripheral representation of flow across the senses of vision and echolocation. PMID:27045094

  1. Influence of permafrost distribution on groundwater flow in the context of climate-driven permafrost thaw: example from Yukon Flats Basin, Alaska, United States

    USGS Publications Warehouse

    Walvoord, Michelle A.; Voss, Clifford I.; Wellman, Tristan P.

    2012-01-01

    Understanding the role of permafrost in controlling groundwater flow paths and fluxes is central in studies aimed at assessing potential climate change impacts on vegetation, species habitat, biogeochemical cycling, and biodiversity. Recent field studies in interior Alaska show evidence of hydrologic changes hypothesized to result from permafrost degradation. This study assesses the hydrologic control exerted by permafrost, elucidates modes of regional groundwater flow for various spatial permafrost patterns, and evaluates potential hydrologic consequences of permafrost degradation. The Yukon Flats Basin (YFB), a large (118,340 km2) subbasin within the Yukon River Basin, provides the basis for this investigation. Model simulations that represent an assumed permafrost thaw sequence reveal the following trends with decreasing permafrost coverage: (1) increased groundwater discharge to rivers, consistent with historical trends in base flow observations in the Yukon River Basin, (2) potential for increased overall groundwater flux, (3) increased spatial extent of groundwater discharge in lowlands, and (4) decreased proportion of suprapermafrost (shallow) groundwater contribution to total base flow. These trends directly affect the chemical composition and residence time of riverine exports, the state of groundwater-influenced lakes and wetlands, seasonal river-ice thickness, and stream temperatures. Presently, the YFB is coarsely mapped as spanning the continuous-discontinuous permafrost transition that model analysis shows to be a critical threshold; thus, the YFB may be on the verge of major hydrologic change should the current permafrost extent decrease. This possibility underscores the need for improved characterization of permafrost and other hydrogeologic information in the region via geophysical techniques, remote sensing, and ground-based observations.

  2. Groundwater Management Policies for Maintaining Stream Flow Given Variable Climatic Conditions

    NASA Astrophysics Data System (ADS)

    Pohll, G.; Carroll, R. W.; Brozovic, N.

    2012-12-01

    Groundwater is an important resource to agriculture throughout the semi-arid United States, where farmers often supplement surface water diversions with groundwater pumping. Understanding the complex exchange over space and time between rivers and aquifers is important in developing management alternatives that are capable of preserving stream flow for habitat and increasing water deliveries downstream while minimizing lost crop production. Previous integrated hydrologic-economic models have generally assumed superposition of the impacts of groundwater pumping on the hydrologic system for analytical tractability. Although this assumption may be reasonable for some surface water-groundwater systems, in many systems the behavior diverges considerably from the linear assumption. We present analyses using an integrated hydrologic-economic model of surface water-groundwater interaction with nonlinear dynamics, developed for the Mason Valley area in Nevada. The study area has active water conflict between upstream and downstream water users, where groundwater pumping has an important impact on streamflow. The model replicates the movement of water throughout the coupled river and aquifer of the Walker River system and is used to analyze hypothetical tradeoffs between increasing streamflow at the basin outlet and meeting crop water demands for irrigation. The model is run from 1997 to 2006 to capture wet and dry climatic conditions, including a four year drought period in which groundwater pumping accounts for more than 50% of the irrigated water budget. Three alternate groundwater management policies are analyzed to compare economic performance (resulting from reductions in crop area due to reduced groundwater pumping) and hydrologic impact (in terms of increased stream discharge at the basin outlet). First, uniform pumping quotas are the simplest policy to implement and are modeled here as equal reductions in groundwater pumping for each stakeholder at a lumped field

  3. 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...

  4. Incorporation of prior information on parameters into nonlinear regression groundwater flow models 2. Applications.

    USGS Publications Warehouse

    Cooley, R.L.

    1983-01-01

    Investigates factors influencing the degree of improvement in estimates of parameters of a nonlinear regression groundwater flow model by incorporating prior information of unknown reliability. Consideration of expected behavior of the regression solutions and results of a hypothetical modeling problem lead to several general conclusions. -from Author

  5. 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.

  6. Hydrologic data and groundwater flow simulations in the vicinity of Long Lake, Indiana Dunes National Lakeshore, near Gary, Indiana

    USGS Publications Warehouse

    Lampe, David C.; Bayless, Randall

    2013-01-01

    decrease discharge as much as 6 percent while increasing the simulated inundated area during wet weather. (5) Deepening of County Line Road ditch can decrease the discharge from US-12 ditch by 26 percent during dry weather and 24 percent during wet weather, as well as decrease the extent of flooded areas south and east of the filtration pond near Ogden Dunes. (7) The increase of the Lake Michigan water level to match the historical maximum can increase the discharge from US-12 ditch by 14 percent during dry weather and by 9.6 percent during wet weather. (8) The decrease of the Lake Michigan water level to match the historical minimum can decrease the discharge from US-12 ditch by 7.4 percent during dry weather and by 3.1 percent during wet weather. The results of this study can be used by water-resource managers to understand how surrounding ditches affect water levels in East and West Long Lake and in the surrounding wetlands and residential areas. The groundwater model developed in this study can be applied in the future to answer questions about how alterations to the drainage system in the area will affect water levels in East and West Long Lake and surrounding areas. The modeling methods developed in this study provide a template for other studies of groundwater flow and groundwater/surface-water interactions within the shallow surficial aquifer in northern Indiana, and in similar hydrologic settings that include surficial sand aquifers in coastal settings.

  7. Ground-water levels and directions of flow near the Industrial Excess Landfill, Uniontown, Ohio, March 1994

    USGS Publications Warehouse

    Dumouchelle, D.H.; Bair, E.S.

    1994-01-01

    Industrial Excess Landfill (IEL), a U.S. Environmental Protection Agency Super-fund site, is a closed landfill in northeastern Ohio. In March 1994, personnel from the U.S. Geological Survey, Ohio Environmental Protection Agency, and PRC Environmental Management, Inc., measured water levels in 149 wells in the area. Surface-water altitudes were measured in 9 piezometers associated with the gages. The data show that the regional pattern of ground-water flow generally is from east to west, but it is locally altered by ground-water mounds that reflect the hummocky terrain. At the landfill, regional flow is altered by two ground-water mounds- one in the southeastern corner of the site and one just to the north. The relatively small ground-water mound at the landfill causes ground water to flow radially away from the southeastern corner of the landfill. Ground water that flows to east and south flows toward Metzger Ditch, whereas flow to the west is consistent with the regional direction of ground-water flow. Ground-water flow northward from IEL is diverted east or west by the southerly component of flow from the larger ground-water mound north of IEL.

  8. 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

  9. Closing the irrigation deficit in Cambodia: Implications for transboundary impacts on groundwater and Mekong River flow

    NASA Astrophysics Data System (ADS)

    Erban, Laura E.; Gorelick, Steven M.

    2016-04-01

    Rice production in Cambodia, essential to food security and exports, is largely limited to the wet season. The vast majority (96%) of land planted with rice during the wet season remains fallow during the dry season. This is in large part due to lack of irrigation capacity, increases in which would entail significant consequences for Cambodia and Vietnam, located downstream on the Mekong River. Here we quantify the extent of the dry season "deficit" area in the Cambodian Mekong River catchment, using a recent agricultural survey and our analysis of MODIS satellite data. Irrigation of this land for rice production would require a volume of water up to 31% of dry season Mekong River flow to Vietnam. However, the two countries share an aquifer system in the Mekong Delta, where irrigation demand is increasingly met by groundwater. We estimate expansion rates of groundwater-irrigated land to be >10% per year in the Cambodian Delta using LANDSAT satellite data and simulate the effects of future expansion on groundwater levels over a 25-year period. If groundwater irrigation continues to expand at current rates, the water table will drop below the lift limit of suction pump wells, used for domestic supply by >1.5 million people, throughout much of the area within 15 years. Extensive groundwater irrigation jeopardizes access for shallow domestic water supply wells, raises the costs of pumping for all groundwater users, and may exacerbate arsenic contamination and land subsidence that are already widespread hazards in the region.

  10. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    USGS Publications Warehouse

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

    2015-01-01

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

  13. Statistical Performance Evaluation of Spatiotemporal Characteristics of Groundwater Flow and Contaminant Mass Transport

    NASA Astrophysics Data System (ADS)

    Matiatos, Ioannis; Papadopoulou, Maria P.; Varouchakis, Emmanouil A.

    2016-04-01

    As groundwater remains one of the most critical natural resources worldwide, numerical models of groundwater flow and contaminant mass transport provide a reliable tool for the efficient protection, planning and sustainable management of groundwater resources. This work focuses on the evaluation of the performance of different numerical models which have been developed to simulate spatiotemporal groundwater flow and contaminant mass transport in a coastal aquifer system. The evaluation of the models' performance has been based on 9 different statistical measures and indices of goodness of fit. Overall, the simulation of groundwater level and contaminant mass concentration delivered very good calibration and validation results in all cases, quite close to the desired values. Maps of aquifer water level and contaminant mass concentrations are provided for all cases in order the differences to be discussed and assessed. The selection of the appropriate model(s) is case oriented and it should be based on the problem's characteristics in order the spatiotemporal variability of the components under study to be optimally estimated.

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

    SciTech Connect

    S. James

    2004-10-06

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

  15. Basin-scale conceptual groundwater flow model for an unconfined and confined thick carbonate region

    NASA Astrophysics Data System (ADS)

    Mádl-Szőnyi, Judit; Tóth, Ádám

    2015-11-01

    Application of the gravity-driven regional groundwater flow (GDRGF) concept to the hydrogeologically complex thick carbonate system of the Transdanubian Range (TR), Hungary, is justified based on the principle of hydraulic continuity. The GDRGF concept informs about basin hydraulics and groundwater as a geologic agent. It became obvious that the effect of heterogeneity and anisotropy on the flow pattern could be derived from hydraulic reactions of the aquifer system. The topography and heat as driving forces were examined by numerical simulations of flow and heat transport. Evaluation of groups of springs, in terms of related discharge phenomena and regional chloride distribution, reveals the dominance of topography-driven flow when considering flow and related chemical and temperature patterns. Moreover, heat accumulation beneath the confined part of the system also influences these patterns. The presence of cold, lukewarm and thermal springs and related wetlands, creeks, mineral precipitates, and epigenic and hypogenic caves validates the existence of GDRGF in the system. Vice versa, groups of springs reflect rock-water interaction and advective heat transport and inform about basin hydraulics. Based on these findings, a generalized conceptual GDRGF model is proposed for an unconfined and confined carbonate region. An interface was revealed close to the margin of the unconfined and confined carbonates, determined by the GDRGF and freshwater and basinal fluids involved. The application of this model provides a background to interpret manifestations of flowing groundwater in thick carbonates generally, including porosity enlargement and hydrocarbon and heat accumulation.

  16. 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.

  17. 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.

  18. Groundwater Flow Dynamic Simulations of a Buried Valley Aquifer Calibrated with Field and Remotely Sensed Data

    NASA Astrophysics Data System (ADS)

    Calderhead, A. I.; Hinton, M. J.; Logan, C. E.; Sharpe, D.; Russel, H. A.; Oldenborger, G. A.; Pugin, A.; Rivera, A.; Castellazzi, P.; Martel, R.

    2013-12-01

    Buried valleys are a common occurrence in the North American prairie landscape. They are often characterized as high yield sources of groundwater in regions where low yield shale and tills dominate the hydrogeological setting. Firstly, 3D conceptual and geological models have been generated and used as a basis for creating a 3D finite element groundwater flow model. Field data, including piezometric readings, base flow measurements, and soil moisture probe data were collected between 2011 and 2013 and are used for calibrating the flow model. Secondly, the study aims to improve the spatial discretization of recharge estimates and include these refined values in the flow model. A temporal series of C-band Radar data and several land surface models were compared with the soil moisture probe data from the Spiritwood buried valley aquifer. The radar backscatter was used to develop moisture estimates at the regional scale. These estimates were then input into the HELP multi-parameter recharge model with the aim of assisting in estimates of a spatial discretization for groundwater recharge. Preliminary groundwater simulation results, with uniform recharge, show good agreement with piezometer readings and measured base flow readings. The temporal series of C-band radar backscatter, moisture probe data, and land surface models show corresponding variations between October, 2011 and October, 2012. The high resolution and regional extent of the radar data has a high potential to help develop a better understanding of recharge patterns in buried valley settings. Integrating a temporal series of high-resolution data into conceptual and numerical model development will refine our mapping, understanding and assessment of buried valley aquifers. Future work will include incorporating the spatially variable recharge estimates into the 3D finite element flow model. Additionally, various interpretations of the geological model will be tested to determine the extent, if any, that a

  19. Perched groundwater-surface interactions and their consequences in stream flow generation in a semi-arid headwater catchment

    NASA Astrophysics Data System (ADS)

    Molenat, Jerome; Bouteffeha, Maroua; Raclot, Damien; Bouhlila, Rachida

    2013-04-01

    In semi-arid headwater catchment, it is usually admitted that stream flow comes predominantly from Hortonian overland flow (infiltration excess overland flow). Consequently, subsurface flow processes, and especially perched or shallow groundwater flow, have not been studied extensively. Here we made the assumption that perched groundwater flow could play a significant role in stream flow generation in semi-arid catchment. To test this assumption, we analyzed stream flow time series of a headwater catchment in the Tunisian Cap Bon region and quantified the flow fraction coming from groundwater discharge and that from overland flow. Furthermore, the dynamics of the perched groundwater was analyzed, by focusing on the different perched groundwater-surface interaction processes : diffuse and local infiltration, diffuse exfiltration, and direct groundwater discharge to the stream channel. This work is based on the 2.6 km² Kamech catchment (Tunisia), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). Results show that even though Hortonian overland flow was the main hydrological process governing the stream flow generation, groundwater discharge contribution to the stream channel annually accounted for from 10% to 20 % depending on the year. Furthermore, at some periods, rising of groundwater table to the soil surface in bottom land areas provided evidences of the occurrence of saturation excess overland flow processes during some storm events. Reference Voltz , M. and Albergel , J., 2002. OMERE : Observatoire Méditerranéen de l'Environnement Rural et de l'Eau - Impact des actions anthropiques sur les transferts de masse dans les hydrosystèmes méditerranéens ruraux. Proposition d'Observatoire de Recherche en Environnement, Ministère de la Recherche.

  20. Testing and benchmarking of a three-dimensional groundwater flow and solute transport model

    SciTech Connect

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

    1988-12-31

    A three-dimensional finite-difference model was developed to simulate groundwater flow and solute transport. The model is intended for application to a variety of groundwater resource and solute migration evaluations, including several complex sites at the Savannah River Plant (SRP). Because the model, FTWORK, is relatively new, there is a need to provide confidence in the model results. Methodologies that test models include comparisons with analytical solutions, comparisons with empirical data, and checking that conservation properties hold. Another level of testing is the comparison of one code against another. This paper describes the testing and benchmarking procedure used to verify the validate FTWORK.

  1. 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.

  2. 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.

  3. Groundwater Flow and Solute Transport in a Tidally influenced gravel beach in Prince William Sound, Alaska

    NASA Astrophysics Data System (ADS)

    Bobo, A. M.; Boufadel, M. C.; Abdollahi Nasab, A.

    2009-12-01

    We investigated beach hydraulics in a gravel beach on Eleanor Island, Prince William Sound, Alaska that was previously polluted with the Exxon Valdez oil spill in 1989. The beach contains trace amounts of oil such that they don’t affect beach hydraulics. Measurements of water pressure and salinity were analyzed and simulated using the model SUTRA (Saturated-Unsaturated Groundwater Flow and Solute Transport). The results indicated that the beach consists of two layers with contrasting hydraulic properties: an upper layer with a hydraulic conductivity of 10-2 m/s, and a lower layer with a hydraulic conductivity of 10-5 m/s. The presence of the layer of low hydraulic conductivity constrained the fall of the water table resulting in a water table fluctuation that is almost independent of distance from the shoreline. This is unlike previous studies, which occurred in sandy beaches, and where the fluctuation decreased going landward. The water table remained above the layers’ interface, which suggests that the oil did not penetrate the lower layer. This could explain the presence of only tracer amount of oil in the beach. A sudden seaward increase of the slope of the two layers’ interface resulted in water leaving the lower layer near the mid-intertidal zone, and draining to the sea through the upper layer. This created the effect of a hydraulic rupture separating the hydraulics in the seaward portion of the beach from the rest of beach, especially at low tide.

  4. Groundwater flow and potential effects on evaporite dissolution in the Paradox Basin, SE Utah

    NASA Astrophysics Data System (ADS)

    Reitman, N.; Ge, S.; Mueller, K. J.

    2012-12-01

    A hydrogeologic study was conducted in the portion of the Paradox Basin south of the Needles District of Canyonlands National Park, Utah. Geology of the study area comprises fractured and faulted Paleozoic sandstone, limestone, and shale, which are underlain by evaporite cycles of the Paradox Formation. The evaporite deposits deform and dissolve when they come in contact with groundwater, generating land subsidence, saline groundwater, and salt input to the Colorado River. Active faults in the region slip at a rate of approximately 2 mm/year, likely due to evaporite dissolution. The objective of this study is to better understand groundwater flow and solute transport dynamics and to help determine the rate and timing of subsurface salt dissolution, which is an important control on the salt tectonics in the region. Study methods include hydrologic fieldwork, laboratory tests, and numerical modeling. No groundwater wells exist in the study area. Water samples from springs and seeps were collected throughout the study area. Analysis of total dissolved solids (TDS), stable oxygen (δ18O) and deuterium (δD) isotopes, spring and seep locations, and prior data are used to gain a preliminary understanding of the shallow groundwater flow in the region. Stable isotope ratios of oxygen (18O/16O) and deuterium (D/H) are used to constrain the source of spring water. Measured δ values are compared to predicted δ values for precipitation from WaterIsotopes.org for each sample site. Measured isotopic values range from -14.9 ‰ to -10.7 ‰ for δ18O and -108 ‰ to -78 ‰ for δD. The majority of samples from above 2000 m match predicted isotopic values for precipitation. Most samples taken below 2000 m are lighter than predicted isotopic values for precipitation. The TDS of spring samples measured in the lab show they range from 184 mg/L to 1552 mg/L with the majority of samples between 220 - 430 mg/L. TDS shows a weak correlation (R2 = 0.54) with altitude, where lower TDS

  5. Analysis of the shallow groundwater flow system near Connetqout Brook, Long Island, New York

    USGS Publications Warehouse

    Prince, K.R.; Reilly, T.E.; Franke, O.L.

    1989-01-01

    Streamflow on Long Island is derived principally from shallow groundwater that flows above the deeper regional flow system. The movement of shallow groundwater was studied during 1975-1982 at Connetquot Brook - an undisturbed stream in Connetquot River State Park - in south-central Long Island. The investigation encompassed: (1) field studies of streamflow, groundwater levels, and age of water as indicated by tritium concentrations, and (2) numerical simulation of the shallow flow system to evaluate the hydraulic factors that influence groundwater flow near and beneath the stream. Analysis of water-level data indicates that groundwater flow is essentially horizontal throughout the drainage basin except near and beneath the stream, where it moves upward diagonally and discharges into the streambank at three sites were 1-2 ft higher than stream stage in the and in wells driven into the streambank at three sites were 1-2 ft higher than stream stage in the first 5 ft of penetration. Increases in head, which were detected to depths of 30 ft beneath the streambed, indicate upward movement of water above that depth. Water samples from selected wells were analyzed for tritium concentration to determine the relative age of water to locate the bottom boundary of the shallow flow system. Tritium concentrations indicate that the lower boundary is from 45 to 100 ft below the water table. A two-dimensional cross-sectional flow model of the shallow flow system indicated that: (1) stream width and streambed hydraulic conductivity influence heads mostly within about 50 ft of the stream; (2) the thickness of the shallow flow system influences heads more distant from the stream but has a negligible effect near the stream; and (3) the quantity of water entering the system as recharge from precipitation influences the heads throughout the area. Field measurements of hydraulic head indicate the shallow flow system to extend to about 30 ft below the stream channel. Results of the

  6. Numerical modeling of groundwater flow in the coastal aquifer system of Taranto (southern Italy)

    NASA Astrophysics Data System (ADS)

    De Filippis, Giovanna; Giudici, Mauro; Negri, Sergio; Margiotta, Stefano; Cattaneo, Laura; Vassena, Chiara

    2014-05-01

    The Mediterranean region is characterized by a strong development of coastal areas with a high concentration of water-demanding human activities, resulting in weakly controlled withdrawals of groundwater which accentuate the saltwater intrusion phenomenon. The worsening of groundwater quality is a huge problem especially for those regions, like Salento (southern Italy), where a karst aquifer system represents the most important water resource because of the deficiency of a well developed superficial water supply. In this frame, the first 2D numerical model describing the groundwater flow in the karst aquifer of Salento peninsula was developed by Giudici et al. [1] at the regional scale and then improved by De Filippis et al. [2]. In particular, the estimate of the saturated thickness of the deep aquifer highlighted that the Taranto area is particularly sensitive to the phenomenon of seawater intrusion, both for the specific hydrostratigraphic configuration and for the presence of highly water-demanding industrial activities. These remarks motivate a research project which is part of the research program RITMARE (The Italian Research for the Sea), within which a subprogram is specifically dedicated to the problem of the protection and preservation of groundwater quality in Italian coastal aquifers and in particular, among the others, in the Taranto area. In this context, the CINFAI operative unit aims at providing a contribution to the characterization of groundwater in the study area. The specific objectives are: a. the reconstruction of the groundwater dynamic (i.e., the preliminary identification of a conceptual model for the aquifer system and the subsequent modeling of groundwater flow in a multilayered system which is very complex from the hydrostratigraphical point of view); b. the characterization of groundwater outflows through submarine and subaerial springs and the water exchanges with the shallow coastal water bodies (e.g. Mar Piccolo) and the off

  7. Groundwater flow and tritium migration from the SRS Old Burial Ground to Fourmile Branch

    SciTech Connect

    Flach, G.P.; Hamm, L.L.; Harris, M.K.

    1996-04-01

    The objectives of this investigation are twofold. The initial goal is to devise and demonstrate a technique for directly incorporating fine-scale lithologic data into heterogeneous hydraulic conductivity fields, for improved groundwater flow and contaminant transport model accuracy. The ultimate goal is to rigorously simulate past and future tritium migration from the SRS Old Burial Ground towards Fourmile Branch, to better understand the effects of various remediation alternatives such as no action and capping. Large-scale variability in hydraulic conductivity is usually the main influence on field-scale groundwater flow patterns and dispersive transport, following the relative locations of recharge and discharge areas. Incorporating realistic hydraulic conductivity heterogeneity into flow and transport models is paramount to accurate simulations, particularly for contaminant migration. Sediment lithologic descriptions and geophysical logs typically offer finer spatial resolution, and therefore more potential information about heterogeneity, than other site characterization data.

  8. Local Modelling of Groundwater Flow Using Analytic Element Method Three-dimensional Transient Unconfined Groundwater Flow With Partially Penetrating Wells and Ellipsoidal Inhomogeneites

    NASA Astrophysics Data System (ADS)

    Jankovic, I.; Barnes, R. J.; Soule, R.

    2001-12-01

    The analytic element method is used to model local three-dimensional flow in the vicinity of partially penetrating wells. The flow domain is bounded by an impermeable horizontal base, a phreatic surface with recharge and a cylindrical lateral boundary. The analytic element solution for this problem contains (1) a fictitious source technique to satisfy the head and the discharge conditions along the phreatic surface, (2) a fictitious source technique to satisfy specified head conditions along the cylindrical boundary, (3) a method of imaging to satisfy the no-flow condition across the impermeable base, (4) the classical analytic solution for a well and (5) spheroidal harmonics to account for the influence of the inhomogeneities in hydraulic conductivity. Temporal variations of the flow system due to time-dependent recharge and pumping are represented by combining the analytic element method with a finite difference method: analytic element method is used to represent spatial changes in head and discharge, while the finite difference method represents temporal variations. The solution provides a very detailed description of local groundwater flow with an arbitrary number of wells of any orientation and an arbitrary number of ellipsoidal inhomogeneities of any size and conductivity. These inhomogeneities may be used to model local hydrogeologic features (such as gravel packs and clay lenses) that significantly influence the flow in the vicinity of partially penetrating wells. Several options for specifying head values along the lateral domain boundary are available. These options allow for inclusion of the model into steady and transient regional groundwater models. The head values along the lateral domain boundary may be specified directly (as time series). The head values along the lateral boundary may also be assigned by specifying the water-table gradient and a head value at a single point (as time series). A case study is included to demonstrate the application

  9. A preliminary evaluation of regional ground-water flow in south-central Washington

    USGS Publications Warehouse

    La Sala, A. M., Jr.; Doty, G.C.; Pearson, F.J., Jr.

    1973-01-01

    The characteristics of regional ground-water flow were investigated in a 4,500-square-mile region of south-central Washington, centered on the U.S. Atomic Energy Commission Hanford Reservation. The investigation is part of the Commission's feasibility study on storing high-level radioactive waste in chambers mined in basaltic rocks at a. depth of about 3,000 feet or more below the surface. Ground-water flow., on a regional scale, occurs principally in the basalt and-in interbedded sediments of the Columbia River Group, and is controlled by topography, the structure of the basalt, and the large streams--the Columbia, Snake, and Yakima Rivers. The ground water beneath the main part of the Hanford Reservation, south and west of the Columbia River, inures southeastward from recharge areas in the uplands, including Cold Creek and Dry Creek valleys, and ultimately discharges to the Columbia River south of the reservation: East and southeast of the Columbia River, ground water flows generally southwestward and discharges to the River. The Yakima River valley contains a distinct flow system in which movement is toward the Yakima River from the topographic divides. A large southward-flowing ground-water system beneath the southern flank of the Horse Heaven Hills discharges to the Columbia River in the westward-trending reach downstream from Wallula Gap.

  10. 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.

  11. 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.

  12. Temporal evolution of soil moisture statistical fractal and controls by soil texture and regional groundwater flow

    NASA Astrophysics Data System (ADS)

    Ji, Xinye; Shen, Chaopeng; Riley, William J.

    2015-12-01

    Soil moisture statistical fractal is an important tool for downscaling remotely-sensed observations and has the potential to play a key role in multi-scale hydrologic modeling. The fractal was first introduced two decades ago, but relatively little is known regarding how its scaling exponents evolve in time in response to climatic forcings. Previous studies have neglected the process of moisture re-distribution due to regional groundwater flow. In this study we used a physically-based surface-subsurface processes model and numerical experiments to elucidate the patterns and controls of fractal temporal evolution in two U.S. Midwest basins. Groundwater flow was found to introduce large-scale spatial structure, thereby reducing the scaling exponents (τ), which has implications for the transferability of calibrated parameters to predict τ. However, the groundwater effects depend on complex interactions with other physical controls such as soil texture and land use. The fractal scaling exponents, while in general showing a seasonal mode that correlates with mean moisture content, display hysteresis after storm events that can be divided into three phases, consistent with literature findings: (a) wetting, (b) re-organizing, and (c) dry-down. Modeling experiments clearly show that the hysteresis is attributed to soil texture, whose "patchiness" is the primary contributing factor. We generalized phenomenological rules for the impacts of rainfall, soil texture, groundwater flow, and land use on τ evolution. Grid resolution has a mild influence on the results and there is a strong correlation between predictions of τ from different resolutions. Overall, our results suggest that groundwater flow should be given more consideration in studies of the soil moisture statistical fractal, especially in regions with a shallow water table.

  13. Characterization of Groundwater Flow at a Mountainous Watershed, Niwot Ridge, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Evans, S. G.; Ge, S.

    2013-12-01

    We present a 3D coupled flow and solute transport hydrogeologic model for the Niwot Ridge Watershed in the Front Range of Colorado. This is the first 3D modeling attempt at detailing groundwater recharges at this site. The 7.6 km2 watershed ranges in elevation from 3241 to 4082 m and is representative of an alpine setting. Its climate is characterized by a mean annual precipitation of 1.95 m, mean annual air temperature of -2.1 °C, and extensive snow coverage six months of the year with 80% of the precipitation falling as snow. At the study site, Proterozoic metamorphic and igneous bedrock is intruded by Tertiary stocks and overlain by Quaternary deposits. In the middle of the watershed are six paternoster lakes connected by North Boulder Creek, the headwaters of the South Platte River. We use a steady state 3D finite element coupled flow and solute transport model to characterize the groundwater and solute transport systems and quantify mountain recharge under averaged long-term conditions. Field data including effective porosity, hydraulic conductivity, and solute concentration in surface water are utilized to constrain and calibrate model parameters. We conduct model sensitivity analysis to examine how uncertainties in model input parameters may influence model results. Preliminary model results indicate that regional groundwater flow is from northwest to southeast, towards North Boulder Creek. This groundwater flow pattern is consistent with field observations. The average hydraulic head gradient over the entire modeled area is approximately 0.12 m/m. Groundwater velocity varies from 1.4 x 10-6 to 1.8 x 10-3 m/s. Groundwater flow is primarily driven by a topographically influenced precipitation regime, with 7% of the total precipitation recharging into the subsurface. Groundwater contribution to baseflow of North Boulder Creek is at an average rate of 0.03 m3/s, which is on the same magnitude as observed values. Modeled discharge solute concentration (Na

  14. Knowledge, transparency, and refutability in groundwater models, an example from the Death Valley regional groundwater flow system

    NASA Astrophysics Data System (ADS)

    Hill, Mary C.; Faunt, Claudia C.; Belcher, Wayne R.; Sweetkind, Donald S.; Tiedeman, Claire R.; Kavetski, Dmitri

    This work demonstrates how available knowledge can be used to build more transparent and refutable computer models of groundwater systems. The Death Valley regional groundwater flow system, which surrounds a proposed site for a high level nuclear waste repository of the United States of America, and the Nevada National Security Site (NNSS), where nuclear weapons were tested, is used to explore model adequacy, identify parameters important to (and informed by) observations, and identify existing old and potential new observations important to predictions. Model development is pursued using a set of fundamental questions addressed with carefully designed metrics. Critical methods include using a hydrogeologic model, managing model nonlinearity by designing models that are robust while maintaining realism, using error-based weighting to combine disparate types of data, and identifying important and unimportant parameters and observations and optimizing parameter values with computationally frugal schemes. The frugal schemes employed in this study require relatively few (10-1000 s), parallelizable model runs. This is beneficial because models able to approximate the complex site geology defensibly tend to have high computational cost. The issue of model defensibility is particularly important given the contentious political issues involved.

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

    USGS Publications Warehouse

    Halford, Keith J.

    2006-01-01

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

  16. 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.

  17. 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.

  18. TYBO/BENHAM: Model Analysis of Groundwater Flow and Radionuclide Migration from Underground Nuclear Tests in Southwestern Pahute Mesa, Nevada

    SciTech Connect

    Andrew Wolfsberg; Lee Glascoe; Guoping Lu; Alyssa Olson; Peter Lichtner; Maureen McGraw; Terry Cherry; Guy Roemer

    2002-09-01

    Recent field studies have led to the discovery of trace quantities of plutonium originating from the BENHAM underground nuclear test in two groundwater observation wells on Pahute Mesa at the Nevada Test Site. These observation wells are located 1.3 km from the BENHAM underground nuclear test and approximately 300 m from the TYBO underground nuclear test. In addition to plutonium, several other conservative (e.g. tritium) and reactive (e.g. cesium) radionuclides were found in both observation wells. The highest radionuclide concentrations were found in a well sampling a welded tuff aquifer more than 500m above the BENHAM emplacement depth. These measurements have prompted additional investigations to ascertain the mechanisms, processes, and conditions affecting subsurface radionuclide transport in Pahute Mesa groundwater. This report describes an integrated modeling approach used to simulate groundwater flow, radionuclide source release, and radionuclide transport near the BENHAM and TYBO underground nuclear tests on Pahute Mesa. The components of the model include a flow model at a scale large enough to encompass many wells for calibration, a source-term model capable of predicting radionuclide releases to aquifers following complex processes associated with nonisothermal flow and glass dissolution, and site-scale transport models that consider migration of solutes and colloids in fractured volcanic rock. Although multiple modeling components contribute to the methodology presented in this report, they are coupled and yield results consistent with laboratory and field observations. Additionally, sensitivity analyses are conducted to provide insight into the relative importance of uncertainty ranges in the transport parameters.

  19. 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

  20. Groundwater in times of droughts

    NASA Astrophysics Data System (ADS)

    Attinger, Sabine; Kumar, Rohini; Musuuza, Jude; Samaniego, Luis

    2014-05-01

    Droughts are characterized as sustained and regionally extensive occurrences of below-average natural water availability. They affect all components of the water cycle: from deficits in soil moisture (agricultural droughts) through reduced groundwater recharge and groundwater levels to low streamflows or dried-up rivers (hydrological droughts). Groundwater discharge is a significant component of streamflow, with groundwater contributing as much as 90 percent of annual streamflow volume in some parts of the U.S., Canada and Europe (Beck et al., 2013). And groundwater systems strongly control the hydrological drought characteristics all over the world (van Lanen et al., 2013). Making use of large scale hydrological models van Lanen demonstrated that groundwater systems substantially affect the duration, particularly of the more extreme drought events. The responsiveness of the groundwater system is as important as climate for hydrological drought development. This urges for an improvement of subsurface modules in conceptual hydrological models to be more useful for water resources assessments. In this talk, we will discuss different subsurface modeling approaches ranging from spatially distributed groundwater models to simpler reservoir-type modeling approaches and the implications the chosen model has on modelled groundwater droughts and base flow characteristics. In particular, we discuss a standardized groundwater drought index (SGI) to characterize the groundwater deficit and the groundwater head anomalies. Based on SGI, we investigate different statistics (severity, area and duration) of individual drought events for the different model approaches. These results will be related to locally measured groundwater data.

  1. 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)

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

    USGS Publications Warehouse

    Moreo, Michael T.; Justet, Leigh

    2008-01-01

    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.

  3. 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.

  4. Investigation of groundwater flow paths through combined inversion of strontium isotope ratios and hydraulic head data. Final report

    SciTech Connect

    Thomas M. Johnson

    1999-12-04

    Strontium (Sr) isotope and other geochemical data were collected for groundwater samples from the Snake River Plain aquifer in the vicinity of the Idaho National Engineering and Environmental Laboratory (INEEL). These geochemical data provide strong evidence for slow and fast groundwater flow zones that had not been previously characterized. The geochemical data were combined with existing hydraulic head data in groundwater flow and transport models. These models enable quantitative extraction of flow information from the data (i.e., inversion of the data). This new approach and the implications for INEEL environmental activities will be reported in two journal articles. One submitted recently and a second in preparation.

  5. 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.

    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)

  6. MODFLOW-Based Coupled Surface Water Routing and Groundwater-Flow Simulation.

    PubMed

    Hughes, J D; Langevin, C D; White, J 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. PMID:24902965

  7. Groundwater Flow and Salt Transport at a Sand Tailings Dam: Field Observations and Modelling Results.

    NASA Astrophysics Data System (ADS)

    Price, A. C.; Mendoza, C. A.

    2004-05-01

    Large volumes of sand tailings are produced during the extraction of bitumen from the oil sands of Northeastern Alberta. The long-term groundwater response and subsequent movement of water and solutes within the large permeable sand tailings storage areas is uncertain. At the Southwest Sand Storage (SWSS) Facility, located at Syncrude's Mildred Lake operations near Ft. McMurray, there is concern that salts from the tailings water may discharge to newly placed reclamation material that covers the sand tailings. This saline discharge water could destroy the reclamation soil structure and negatively impact vegetation. The steady-state groundwater flow and transient movement of salts at the local (bench and slope) and intermediate (pile) scales in the SWSS are investigated. Water levels, seepage and groundwater quality (including TDS) have been measured for over a year along two transects of piezometers installed in the SWSS. The field data have been used to complete traditional hydrogeological interpretations of the site, and to develop a conceptual model of flow and transport. The local and intermediate flow systems and salt transport in the dam are being evaluated with numerical models. The models will allow possible future hydrogeological behaviour of the structure to be tested. Preliminary results show differences in flow systems and salinity distribution that depend on the deposition of the SWSS. This research will facilitate better long-term environmental management of this and similar sites.

  8. 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.

  9. Geo-Hydro Statistical Characterization of Preferential Flow and Transport Processes in Karst Groundwater Systems

    NASA Astrophysics Data System (ADS)

    Anaya, A. A.; Padilla, I. Y.; Macchiavelli, R. E.

    2011-12-01

    Karst groundwater systems are highly productive and provide an important fresh water resource for human development and ecological integrity. Their high productivity is often associated with conduit flow and high matrix permeability. The same characteristics that make these aquifers productive also make them highly vulnerable to contamination and a likely for contaminant exposure. Of particular interest are chlorinated organic contaminants and phthalates derived from industrial solvents and plastic by-products. These chemicals have been identified as potential precursors of pre-term birth, a leading cause of neonatal complications with a significant health and societal cost. The general objectives of this work are to: (1) develop fundamental knowledge and determine the processes controlling the release, mobility, persistence, and possible pathways of contaminants in karst groundwater systems, and (2) characterize transport processes in conduit and diffusion-dominated flow under base flow and storm flow conditions. The work presented herein focuses on the development of geo-hydro statistical tools to characterize flow and transport processes under different flow regimes. Multidimensional, laboratory-scale Geo-Hydrobed models were developed and tested for this purpose. The models consist of stainless-steel tanks containing karstified limestone blocks collected from the karst aquifer formation of northern Puerto Rico. The models a network of sampling wells to monitor flow, pressure, and solute concentrations temporally and spatially. Experimental work entailed making a series of point injections in wells while monitoring the hydraulic response in other wells. Statistical mixed models were applied to spatial probabilities of hydraulic response and weighted injected volume data, and were used to determinate the best spatial correlation structure to represent paths of preferential flow in the limestone units under different groundwater flow regimes. Preliminary testing

  10. Ground-water flow in Melton Valley, Oak Ridge reservation, Roane County, Tennessee; preliminary model analysis

    USGS Publications Warehouse

    Tucci, Patrick

    1986-01-01

    Shallow land burial of low-level radioactive waste has been practiced since 1951 in Melton Valley. Groundwater flow modeling was used to better understand the geohydrology of the valley, and to provide a foundation for future contaminant transport modeling. The three-dimensional, finite difference model simulates the aquifer as a two layer system that represents the regolith and bedrock. Transmissivities, which were adjusted during model calibration, range from 8 to 16 sq ft/day for the regolith, and from 0.2 to 1.5 sq ft/day for bedrock. An anisotropy ratio of 1:3 for strike-normal to strike-parallel transmissivity values, in conjunction with recharge rate = 6% of precipitation that is uniformly distributed over the model area, produces the best match between simulated and observed water levels. Simulated water levels generally compare well to observed or estimated 1978 groundwater conditions. Simulated water levels for the regolith for 39 of 69 comparison points are within +/- 10 ft of average 1978 levels. Simulated vertical flow components are in the observed direction for 9 of 11 comparison points. Preliminary simulations indicate that nearly all groundwater flow is within the regolith and discharges to either the Clinch River or the White Oak Creek-Melton Branch drainage systems. Less than 3% of the flow is between the regolith and bedrock, and < 1% of total groundwater flow discharges to the Clinch River through bedrock. Additional data needed to refine and further calibrate the model, include: (1) quantity and areal distribution of recharge; (2) water levels in the regolith near the model boundaries and beyond the Clinch River; (3) water levels and aquifer characteristics for bedrock; and (4) additional surface water data. (Author 's abstract)

  11. Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Li, Ling; Erler, Dirk V.; Santos, Isaac; Lockington, David

    2016-02-01

    Variations of beach morphology in both the cross-shore and alongshore directions, associated with tidal creeks, are common at natural coasts, as observed at a field site on the east coast of Rarotonga, Cook Islands. Field investigations and three-dimensional (3-D) numerical simulations were conducted to study the nearshore groundwater flow and solute transport in such a system. The results show that the beach morphology, combined with tides, induced a significant alongshore flow and modified local pore water circulation and salt transport in the intertidal zone substantially. The bathymetry and hydraulic head of the creek enabled further and more rapid landward intrusion of seawater along the creek than in the aquifer, which created alongshore hydraulic gradient and solute concentration gradient to drive pore water flow and salt transport in the alongshore direction within the aquifer. The effects of the creek led to the formation of a saltwater plume in groundwater at an intermediate depth between fresher water zones on a cross-shore transect. The 3-D pore water flow in the nearshore zone was also complicated by the landward hydraulic head condition, resulting in freshwater drainage across the inland section of the creek while seawater infiltrating the seaward section. These results provided new insights into the complexity, intensity, and time scales of mixing among fresh groundwater, recirculating seawater and creek water in three dimensions. The 3-D characteristics of nearshore pore water flow and solute transport have important implications for studies of submarine groundwater discharge and associated chemical input to the coastal sea, and for evaluation of the beach habitat conditions.

  12. Uncertainty analysis of a groundwater flow model in East-central Florida.

    PubMed

    Sepúlveda, Nicasio; Doherty, John

    2015-01-01

    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 or temporal variability of uncertainties that are associated with predictions of future system behavior in a complex hydrogeological context. PMID:25040026

  13. 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.

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

    USGS Publications Warehouse

    Long, A.J.; Valder, J.F.

    2011-01-01

    Principal component analysis (PCA) applied to hydrochemical data has been used with end-member mixing to characterize groundwater flow to a limited extent, but aspects of this approach are unresolved. Previous similar approaches typically have assumed that the extreme-value samples identified by PCA represent end members. The method presented herein is different from previous work in that (1) end members were not assumed to have been sampled but rather were estimated and constrained by prior knowledge; (2) end-member mixing was quantified in relation to hydrogeologic domains, which focuses model results on major hydrologic processes; (3) a method to select an appropriate number of end members using a series of cluster analyses is presented; and (4) conservative tracers were weighted preferentially in model calibration, which distributed model errors of optimized values, or residuals, more appropriately than would otherwise be the case. The latter item also provides an estimate of the relative influence of geochemical evolution along flow paths in comparison to mixing. This method was applied to groundwater in Wind Cave and the associated karst aquifer in the Black Hills of South Dakota, USA. The end-member mixing model was used to test a hypothesis that five different end-member waters are mixed in the groundwater system comprising five hydrogeologic domains. The model estimated that Wind Cave received most of its groundwater inflow from local surface recharge with an additional 33% from an upgradient aquifer. Artesian springs in the vicinity of Wind Cave primarily received water from regional groundwater flow. ?? 2011.

  15. Ground-water heat pumps: an examination of hydrogeologic, environmental, legal, and economic factors affecting their use

    SciTech Connect

    Armitage, D M; Bacon, D J; Massey-Norton, J T; Miller, J D

    1980-11-12

    Groundwater is attractive as a potential low-temperature energy source in residential space-conditioning applications. When used in conjuncton with a heat pump, ground water can serve as both a heat source (for heating) and a heat sink (for cooling). Major hydrogeologic aspects that affect system use include groundwater temperature and availability at shallow depths as these factors influence operational efficiency. Ground-water quality is considered as it affects the performance and life-expectancy of the water-side heat exchanger. Environmental impacts related to groundwater heat pump system use are most influenced by water use and disposal methods. In general, recharge to the subsurface (usually via injection wells) is recommended. Legal restrictions on system use are often stricter at the municipal and county levels than at state and Federal levels. Although Federal regulations currently exist, the agencies are not equipped to regulate individual, domestic installations. Computer smulations indicate that under a variety of climatologic conditions, groundwater heat pumps use less energy than conventional heating and cooling equipment. Life-cycle cost comparisons with conventional equipment depend on alternative system choices and well cost options included in the groundwater heat pump system.

  16. 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

  17. Water and rock geochemistry, geologic cross sections, geochemical modeling, and groundwater flow modeling for identifying the source of groundwater to Montezuma Well, a natural spring in central Arizona

    USGS Publications Warehouse

    Johnson, Raymond H.; DeWitt, Ed; Wirt, Laurie; Arnold, L. Rick; Horton, John D.

    2011-01-01

    The National Park Service (NPS) seeks additional information to better understand the source(s) of groundwater and associated groundwater flow paths to Montezuma Well in Montezuma Castle National Monument, central Arizona. The source of water to Montezuma Well, a flowing sinkhole in a desert setting, is poorly understood. Water emerges from the middle limestone facies of the lacustrine Verde Formation, but the precise origin of the water and its travel path are largely unknown. Some have proposed artesian flow to Montezuma Well through the Supai Formation, which is exposed along the eastern margin of the Verde Valley and underlies the Verde Formation. The groundwater recharge zone likely lies above the floor of the Verde Valley somewhere to the north or east of Montezuma Well, where precipitation is more abundant. Additional data from groundwater, surface water, and bedrock geology are required for Montezuma Well and the surrounding region to test the current conceptual ideas, to provide new details on the groundwater flow in the area, and to assist in future management decisions. The results of this research will provide information for long-term water resource management and the protection of water rights.

  18. Coupled modeling of groundwater flow solute transport, chemical reactions and microbial processes in the 'SP' island

    SciTech Connect

    Samper, Javier; Molinero, Jorg; Changbing, Yang; Zhang, Guoxiang

    2003-12-01

    The Redox Zone Experiment was carried out at the Aespoe HRL in order to study the redox behavior and the hydrochemistry of an isolated vertical fracture zone disturbed by the excavation of an access tunnel. Overall results and interpretation of the Redox Zone Project were reported by /Banwart et al, 1995/. Later, /Banwart et al, 1999/ presented a summary of the hydrochemistry of the Redox Zone Experiment. Coupled groundwater flow and reactive transport models of this experiment were carried out by /Molinero, 2000/ who proposed a revised conceptual model for the hydrogeology of the Redox Zone Experiment which could explain simultaneously measured drawdown and salinity data. The numerical model was found useful to understand the natural system. Several conclusions were drawn about the redox conditions of recharge waters, cation exchange capacity of the fracture zone and the role of mineral phases such as pyrite, calcite, hematite and goethite. This model could reproduce the measured trends of dissolved species, except for bicarbonate and sulfate which are affected by microbially-mediated processes. In order to explore the role of microbial processes, a coupled numerical model has been constructed which accounts for water flow, reactive transport and microbial processes. The results of this model is presented in this report. This model accounts for groundwater flow and reactive transport in a manner similar to that of /Molinero, 2000/ and extends the preliminary microbial model of /Zhang, 2001/ by accounting for microbially-driven organic matter fermentation and organic matter oxidation. This updated microbial model considers simultaneously the fermentation of particulate organic matter by yeast and the oxidation of dissolved organic matter, a product of fermentation. Dissolved organic matter is produced by yeast and serves also as a substrate for iron-reducing bacteria. Model results reproduce the observed increase in bicarbonate and sulfate concentration, thus

  19. Borehole Geophysics, Hydraulic Characteristics and Chemistry of Groundwater Flow in Fractured Granite With Very Low Permeability

    NASA Astrophysics Data System (ADS)

    Lukes, J.; Rukavickova, L.; Paces, T.

    2005-12-01

    increased with depth to the maximum of 8.8 fractures per meter. The hydraulic conductivity of the fractured granite was investigated with WPT and slug tests. We measured the water loss at pressures 2.7x10-1 and 4.5x10-1 MPa. The water loss was tested in sections separated with the packers. The thickness of the sections varied from 1 to 50 meters. The water loss below 150 m was extremely low from 5x10-5 to 4x10-4 liters per minute per meter. Above 100 m depth the water loss varied from 3x10-3 to 7x10-1 L/min/m. The weathered zone to a depth of 25 m had a permeability of 2x10-6 m/s. The zone of opened fractures reached to a depth of 95 m with permeability from 2x10-9 to 2x10-7 m/s. Granite below 95 m had a dense net of fractures, however, the fractures were closed so that the permeability was very low from 2x10-12 to 4x10-9 m/s. After the logging and hydraulic tests, samplers of water were installed in four sections of one of the drill holes. Very small quantities of water are periodically pumped out and analyzed. Electric conductivity and chemical composition of groundwater from the granite returned to a natural composition not affected by injection of salt after several months. Water from the deepest section (230-296 m) reflects the influence of local stream water while water from the shallower sections reflects a prolonged or more intensive interaction with granite. This indicates also the complexity of the fracture system. The data are used to build a specific simulation model to represent groundwater flow and water-rock interaction in fractured granite.

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

    USGS Publications Warehouse

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

    1992-01-01

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

  1. 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.

  2. Digital models of ground-water flow in the Cape Cod aquifer system, Massachusetts

    USGS Publications Warehouse

    Guswa, John H.; LeBlanc, Denis R.

    1985-01-01

    The Cape Cod aquifer system was simulated with three-dimensional finite-difference ground-water-flow models. Five areas were modeled to provide tools that can be used to evaluate the hydrologic impacts of regional water development and waste disposal. The model boundaries were selected to represent the natural hydrologic boundaries of the aquifer. The boundary between fresh and saline ground water was treated as an interface along which there is no dispersion. The saline-water zone was treated as static (nonflowing). Comparisons of calculated and observed values of head, position of the boundary between fresh and saline water, and ground-water discharge (at locations where data were available) indicate that the simulated groundwater reservoirs generally agree with field conditions. Model analyses indicate that the total steady-state freshwater-flow rate through the five modeled areas is approximately 412 cubic feet per second.

  3. Automatic Time Stepping with Global Error Control for Groundwater Flow Models

    SciTech Connect

    Tang, Guoping

    2008-09-01

    An automatic time stepping with global error control is proposed for the time integration of the diffusion equation to simulate groundwater flow in confined aquifers. The scheme is based on an a posteriori error estimate for the discontinuous Galerkin (dG) finite element methods. A stability factor is involved in the error estimate and it is used to adapt the time step and control the global temporal error for the backward difference method. The stability factor can be estimated by solving a dual problem. The stability factor is not sensitive to the accuracy of the dual solution and the overhead computational cost can be minimized by solving the dual problem using large time steps. Numerical experiments are conducted to show the application and the performance of the automatic time stepping scheme. Implementation of the scheme can lead to improvement in accuracy and efficiency for groundwater flow models.

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

    USGS Publications Warehouse

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

    2009-01-01

    A substantial number of public water system wells in south-central Texas withdraw groundwater from the karstic, highly productive Edwards aquifer. However, the use of numerical groundwater flow models to aid in the delineation of contributing areas for public water system wells in the Edwards aquifer is problematic because of the complex hydrogeologic framework and the presence of conduit-dominated flow paths in the aquifer. The U.S. Geological Survey, in cooperation with the Texas Commission on Environmental Quality, evaluated six published numerical groundwater flow models (all deterministic) that have been developed for the Edwards aquifer San Antonio segment or Barton Springs segment, or both. This report describes the models developed and evaluates each with respect to accessibility and ease of use, range of conditions simulated, accuracy of simulations, agreement with dye-tracer tests, and limitations of the models. These models are (1) GWSIM model of the San Antonio segment, a FORTRAN computer-model code that pre-dates the development of MODFLOW; (2) MODFLOW conduit-flow model of San Antonio and Barton Springs segments; (3) MODFLOW diffuse-flow model of San Antonio and Barton Springs segments; (4) MODFLOW Groundwater Availability Modeling [GAM] model of the Barton Springs segment; (5) MODFLOW recalibrated GAM model of the Barton Springs segment; and (6) MODFLOW-DCM (dual conductivity model) conduit model of the Barton Springs segment. The GWSIM model code is not commercially available, is limited in its application to the San Antonio segment of the Edwards aquifer, and lacks the ability of MODFLOW to easily incorporate newly developed processes and packages to better simulate hydrologic processes. MODFLOW is a widely used and tested code for numerical modeling of groundwater flow, is well documented, and is in the public domain. These attributes make MODFLOW a preferred code with regard to accessibility and ease of use. The MODFLOW conduit-flow model

  5. Chemical Evolution of Groundwater Near a Sinkhole Lake, Northern Florida: 1. Flow Patterns, Age of Groundwater, and Influence of Lake Water Leakage

    NASA Astrophysics Data System (ADS)

    Katz, Brian G.; Lee, Terrie M.; Plummer, L. Niel; Busenberg, Eurybiades

    1995-06-01

    Leakage from sinkhole lakes significantly influences recharge to the Upper Floridan aquifer in poorly confined sediments in northern Florida. Environmental isotopes (oxygen 18, deuterium, and tritium), chlorofluorocarbons (CFCs: CFC-11, CCl3F; CFC-12, CCl2F2; and CFC-113, C2Cl3F3), and solute tracers were used to investigate groundwater flow patterns near Lake Barco, a seepage lake in a mantled karst setting in northern Florida. Stable isotope data indicated that the groundwater downgradient from the lake contained 11-67% lake water leakage, with a limit of detection of lake water in groundwater of 4.3%. The mixing fractions of lake water leakage, which passed through organic-rich sediments in the lake bottom, were directly proportional to the observed methane concentrations and increased with depth in the groundwater flow system. In aerobic groundwater upgradient from Lake Barco, CFC-modeled recharge dates ranged from 1987 near the water table to the mid 1970s for water collected at a depth of 30 m below the water table. CFC-modeled recharge dates (based on CFC-12) for anaerobic groundwater downgradient from the lake ranged from the late 1950s to the mid 1970s and were consistent with tritium data. CFC-modeled recharge dates based on CFC-11 indicated preferential microbial degradation in anoxic waters. Vertical hydraulic conductivities, calculated using CFC-12 modeled recharge dates and Darcy's law, were 0.17, 0.033, and 0.019 m/d for the surficial aquifer, intermediate confining unit, and lake sediments, respectively. These conductivities agreed closely with those used in the calibration of a three-dimensional groundwater flow model for transient and steady state flow conditions.

  6. 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

  7. Phytoremediation of explosives contaminated groundwater in constructed wetlands: 2. Flow through study. Draft report

    SciTech Connect

    DBehrends, L.L.; Sikora, F.J.; Phillips, W.D.; Baily, E.; McDonald, C.

    1996-02-01

    This study evaluates the utility of constructed wetlands for remediating explosives contaminated groundwaters using bench scale flow-through type reactors. Specifially the study examines: the degradation of TNT, TNB, RDX, and HMX in contaminated waters in plant lagoons and gravel-based wetlands. The study also provides design recommendations for the wetland demonstration project to be located at the Milan Army Ammunition Plant (MAAP), in Tennessee.

  8. Overland flow caused by groundwater springs in the Catskill Mountains, New York, USA

    NASA Astrophysics Data System (ADS)

    Harpold, A. A.; Steenhuis, T.

    2007-12-01

    Groundwater springs have been shown to be important for baseflow maintenance, ecological diversity, and biogeochemical transport in the Catskill Mountains of New York State. A study was undertaken to evaluate the importance of groundwater springs to stream flow response, spatial distribution of saturated areas, and chemical transport on a 2 km2 watershed. Discharge and water chemistry were monitored at five upland springs and the watershed outlet during three storm events and weekly for one year. The spatiotemporal connectivity of groundwater springs to the stream was evaluated using the isotopes, conservative geochemical tracers, groundwater heights, temperature probes, and soil moisture measurements. The data indicates that spring discharge is capable of maintaining isolated areas of saturation and overland flow that provide hydrologic connections between upland hillslopes and the stream. Thus, upslope springs can be important sources of solutes and nutrients, especially during baseflow periods. The response of the individual springs was correlated to the upslope contributing area during large rain events. However, terrain indices were not capable of predicting relative spring discharge during moderate to dry conditions. The results suggest that two geomorphologic wetness states exist for this Catskill watershed: 1. during wet antecedent conditions surface topography is a first- order control on water table heights and overland flow, 2. during dry to average antecedent wetness conditions geomorphologic heterogeneities (e.g. bedrock fractures and confining layers) control locations and extent of saturated areas and overland flow. The two-state wetness system hypothesis has important ramifications for developing watershed-scale parameters (i.e. drainage density) and spatial modeling in heterogeneous landscapes.

  9. 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).

  10. A comparison of several methods of solving nonlinear regression groundwater flow problems.

    USGS Publications Warehouse

    Cooley, R.L.

    1985-01-01

    Computational efficiency and computer memory requirements for four methods of minimizing functions were compared for four test nonlinear-regression steady state groundwater flow problems. The fastest methods were the Marquardt and quasi-linearization methods, which required almost identical computer times and numbers of iterations; the next fastest was the quasi-Newton method, and last was the Fletcher-Reeves method, which did not converge in 100 iterations for two of the problems.-from Author

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

    USGS Publications Warehouse

    Cooley, R.L.

    1982-01-01

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

  12. Analytical solutions for groundwater flow with arbitrary dimensionality and a finite well radius in fractured rock

    NASA Astrophysics Data System (ADS)

    Rehbinder, G.

    2010-03-01

    The generalized radial flow model describes mathematically nonsteady flow of arbitrary dimensionality from a source in a porous medium. Closed solutions of the corresponding equation have hitherto been considered as impractical except for one simple special case. Two closed solutions of the generalized radial flow equation, corresponding to given head in or given discharge from the source have been derived. The noninteger dimensionality is the only parameter in the problem. The solutions become not valid if the time tends to infinity, such as for 1-D and 2-D flows. The influence of a possible noninteger dimensionality has attracted interest in connection with the flow of groundwater in fractured rock, particularly around a repository for nuclear waste or in connection with grouting. In contrast to numerical solutions, the closed solutions offer simple means for evaluation of field tests.

  13. Parameter identification in stationary groundwater flow problems in drainage basins

    NASA Astrophysics Data System (ADS)

    Malengier, B.

    2004-07-01

    We discuss the recovery of some parameters in an elliptic boundary value problem, which models a specific stationary flow problem in drainage basins, by using the measured values of the hydraulic head in discrete points through the physical domain. The underlying direct problem is the one considered by Toth (J. Geophys. Res. 67 (1962) 4375; 67 (1963) 4795), among others. The inverse problem is solved by means of the Levenberg-Marquardt method (in: G.A. Watson (Ed.), Numerical Analysis, Lecture Notes in Mathematics, Vol. 630, Springer, Berlin, New York, 1977, pp. 105-116). We also show how the infinite element method allows the identification of the far field value of the hydraulic head.

  14. Connecting Surface Planting with Subsurface Erosion Due to Groundwater Flow

    NASA Astrophysics Data System (ADS)

    Reardon, M.; Curran, J. C.

    2014-12-01

    Bank erosion and failure is a major contributor of fine sediment to streams and rivers, and can be driven by subsurface flow. In restoration projects, vegetation is often planted on banks to reduce erosion and stabilize the banks. However, the relationship between subsurface flow, erosion and vegetation remains somewhat speculative. A comparative study quantified the effect of surface planting on subsurface erosion and soil strength. Six 32-gallon containers were layered with a sandy loam overlying a highly conductive sand layer and a confining clay. Three treatments were applied in pairs: switchgrass (Panicum virgatum L.), sod (turf-type tall fescue and Kentucky bluegrass mix), and no vegetation. After a vegetation establishment period, the 2, 10, and 100 year rainfalls were simulated. Samples collected from ports in the containers were analyzed for subsurface drainage volume and suspended sediment concentration. After all rainfall simulations, a sediment core was taken from each container to measure shear strength and root density. Results indicate the relative benefits of vegetative planting to reduce subsurface erosion during storms and enhance soil strength. Switchgrass reduced the total amount of sediment removed from containers during all three storms when compared to the sod and during the 10 and 100 year storms when compared to the bare ground. Results from the volume analysis were more variable. Switchgrass retained the greatest volume of water from the 100 year storm event, but also released the largest fraction of water in the 2 and 10 year storms. Both sod and switchgrass planting considerably increased the time required for the soil samples to fail despite reducing the shear stress at failure. Where switchgrass grew long, woody roots, the sod developed a dense mat of interconnected thin roots. We suspect the different root patterns between sod and switchgrass to be a dominant factor in the response of the different containers.

  15. Simulating the influence of two shallow, flow-through lakes on a groundwater system: implications for groundwater mounds and hinge lines

    NASA Astrophysics Data System (ADS)

    Gosselin, David C.; Khisty, Mohan J.

    2001-10-01

    Groundwater mounds and hinge lines are important features related to the interaction of groundwater and lakes. In contrast to the transient formation of groundwater mounds, numerical simulations indicate that permanent groundwater mounds form between closely spaced lakes as the natural consequence of adding two net sinks to a groundwater flow system. The location of the groundwater mound and the position of the hinge lines between the two lakes are intimately related. As the position of the mound changes there is a corresponding shift in the position of the hinge line. This results in a change in the ratio of groundwater inflow to outflow (Qi/Qo) for the lake. The response of the lake is an increase or decrease in the lake level. Our simulations indicate that the movement of the hinge line in a natural system is a consequence of the dynamic interrelationships between recharge, the slope of the water table upgradient and downgradient of the lake, and the loss of water from the lake by evaporation. The extent of the seasonal movement of the hinge line will vary from one year to the next depending on local changes in the magnitude of the hydrologic variables.

  16. How geomorphology and groundwater level affect the spatio-temporal variability of riverine cold water patches?

    NASA Astrophysics Data System (ADS)

    Wawrzyniak, Vincent; Piégay, Hervé; Allemand, Pascal; Vaudor, Lise; Goma, Régis; Grandjean, Philippe

    2016-04-01

    . Nonetheless, amongst all patch types, some are quite stable over time, while others are transient. These results can be used to target areas with high densities of stable and spatially extensive cold water patches that are considered ecological refuges, in the context of pronounced low flow and a rise in water temperature. Key words: River temperature; Thermal Infrared (TIR) remote sensing; groundwater; fluvial geomorphic features; side channels; spatio-temporal variability; lower Ain River (France).

  17. Analytical solutions of three-dimensional groundwater flow to a well in a leaky sloping fault-zone aquifer

    NASA Astrophysics Data System (ADS)

    Zhao, Yuqing; Zhang, You-Kuan; Liang, Xiuyu

    2016-08-01

    A semi-analytical solution was presented for groundwater flow due to pumping in a leaky sloping fault-zone aquifer surrounded by permeable matrices. The flow in the aquifer was descried by a three-dimensional flow equation, and the flow in the upper and lower matrix blocks are described by a one-dimensional flow equation. A first-order free-water surface equation at the outcrop of the fault-zone aquifer was used to describe the water table condition. The Laplace domain solution was derived using Laplace transform and finite Fourier transform techniques and the semi-analytical solutions in the real time domain were evaluated using the numerical inverse Laplace transform method. The solution was in excellent agreement with Theis solution combined with superposition principle as well as the solution of Huang et al. (2014). It was found that the drawdown increases as the sloping angle of the aquifer increases in early time and the impact of the angle is insignificant after pumping for a long time. The free-water surface boundary as additional source recharges the fault aquifer and significantly affect the drawdown at later time. The surrounding permeable matrices have a strong influence on drawdown but this influence can be neglected when the ratio of the specific storage and the ratio of the hydraulic conductivity of the matrices to those of the fault aquifer are less than 0.001.

  18. Simulation of groundwater flow in a volatile organic compound-contaminated area near Bethpage, Nassau County, New York-A discussion of modeling considerations

    USGS Publications Warehouse

    Misut, Paul E.

    2011-01-01

    The 2010 Bethpage groundwater-flow model (ARCADIS, 2010) was based on a steady state assumption. Although it is widely acknowledged that significant water-level changes have occurred in the past, the reviewed model does not represent changing water levels. The steady state approach limits the effectiveness of the following: 1. identification of sources of contamination, 2. analysis of model accuracy, 3. model calibration, and 4. simulations of future scenarios. Future plume movement was simulated in an incomplete manner through an unchanging groundwater-flow field. Available time-series information on temporal variation of factors affecting groundwater-flow dynamics includes: 1. public-supply pumping, 2. groundwater discharges from systems remediating volatile organic compound (VOC) plumes, 3. recharge and precipitation rates, and 4. water levels and streamflows. Transient phenomena that might be useful in future hypothetical simulations include pumping variations, redirection of containment-system waters for industrial use, and climate-change scenarios. Public-domain computer programs, U.S. Geological Survey guidance reports on transient-state calibration and uncertainty methods (Doherty and Hunt, 2010), and additional local and regional datasets are available to provide additional confidence in model evaluations and allow better evaluation of their limitations.

  19. Effect of land fill on the groundwater flow and nutrient supply in the coastal area

    NASA Astrophysics Data System (ADS)

    Onodera, S.; Saito, M.; Kato, Y.; Shimizu, Y.; Yoshikawa, S.

    2009-12-01

    To clarify the land fill effect of tidal flat and offshore on groundwater flow and seawater nutrient, we conducted the tracer measurements of sea and terrestrial water and observations of piezometers at a coast are with a small city of Seto Inland Sea watershed. The research area is located on the Marugame city and suburban area around that in Sikoku island of southwest Japan. This city has 100,000 of population and land fill area distributes around coastal area. The present coastal line shifted to offshore 2km for last 50 years. The rainfall is around 1000mm. Water samples contained sea water at 500m intervals around a coastal line of 10km, river and blackish water at the some points in two rivers at the city and suburban area, pore water of the river bed, and groundwater at some boreholes and wells. We analyzed the samples for 222Rn, nutrient, and inorganic elements. The samplings were conducted in summer of 2008 and 2009 and observations were from 2007 to 2009, respectively. The 222Rn concentration of seawater was higher around suburban area, on the other hand that was lower than around city area. In addition, piezometric head in the piezometer were higher than tidal river water level at the inland area of around 2km from the present river mouth, but those were same as the river water level at around the river mouth area in the city area. These results suggested that groundwater discharge stopped to the ocean, whereas groundwater discharged to the tidal river around the past coastal line. Consequently, we confirmed that nutrient of groundwater does not reached directly to the ocean around city area. We should consider more about the nutrient transport process in the tidal river. Keywords: land fill, seawater, tidal flat, groundwater, nutrient

  20. Numerical simulation of groundwater flow in Dar es Salaam Coastal Plain (Tanzania)

    NASA Astrophysics Data System (ADS)

    Luciani, Giulia; Sappa, Giuseppe; Cella, Antonella

    2016-04-01

    They are presented the results of a groundwater modeling study on the Coastal Aquifer of Dar es Salaam (Tanzania). Dar es Salaam is one of the fastest-growing coastal cities in Sub-Saharan Africa, with with more than 4 million of inhabitants and a population growth rate of about 8 per cent per year. The city faces periodic water shortages, due to the lack of an adequate water supply network. These two factors have determined, in the last ten years, an increasing demand of groundwater exploitation, carried on by quite a number of private wells, which have been drilled to satisfy human demand. A steady-state three dimensional groundwater model has been set up by the MODFLOW code, and calibrated with the UCODE code for inverse modeling. The aim of the model was to carry out a characterization of groundwater flow system in the Dar es Salaam Coastal Plain. The inputs applied to the model included net recharge rate, calculated from time series of precipitation data (1961-2012), estimations of average groundwater extraction, and estimations of groundwater recharge, coming from zones, outside the area under study. Parametrization of the hydraulic conductivities was realized referring to the main geological features of the study area, based on available literature data and information. Boundary conditions were assigned based on hydrogeological boundaries. The conceptual model was defined in subsequent steps, which added some hydrogeological features and excluded other ones. Calibration was performed with UCODE 2014, using 76 measures of hydraulic head, taken in 2012 referred to the same season. Data were weighted on the basis of the expected errors. Sensitivity analysis of data was performed during calibration, and permitted to identify which parameters were possible to be estimated, and which data could support parameters estimation. Calibration was evaluated based on statistical index, maps of error distribution and test of independence of residuals. Further model

  1. Investigation of uranium geochemistry along groundwater flow path in the Continental Intercalaire aquifer (Southern Tunisia).

    PubMed

    Dhaoui, Z; Chkir, N; Zouari, K; Ammar, F Hadj; Agoune, A

    2016-06-01

    Environmental tracers ((2)H, (18)O, isotopes of Uranium) and geochemical processes occurring within groundwaters from the Continental Intercalaire (CI) in Southern Tunisia were used to understand the hydrodynamics and the recharge conditions of this aquifer. This study investigates the chemical and isotopic compositions of the CI groundwater. The water types are dominated by Na(+), SO4(2-), Cl(-) throughout most of the basin with a general increase in total dissolved solids from the Saharan Platform margins towards the Chotts region. Large scale groundwater flow paths are toward the Chotts region. The stable isotopes composition of the analyzed groundwater ranges from -8.8 to -6‰ vs V-SMOW for δ(18)O and from -67 to -40‰ vs V-SMOW for δ(2)H. The relatively enriched stable isotopes contents suggest the contribution of the Dahar sandstones outcrops in the current recharge of the CI aquifer in an arid context. However, the most depleted values in heavy isotopes indicate a paleorecharge of the aquifer under wetter conditions revealing a long residence time of groundwaters. The results from water samples using alpha spectrometry method indicate a range in (238)U concentrations and (234)U/(238)U activity ratios (AR) of 0.044-1.285 μg kg(-1) and 1.2 to 8.84 respectively. The geochemistry of uranium isotopes in groundwater is controlled by many factors, essentially, the influence of water rock interactions, the preferential dissolution of (234)U relative to (238)U due to alpha recoil and the mixing processes between different waters with distinct AR as well as (238)U concentrations. PMID:27015035

  2. Simultaneous parameter estimation and contaminant source characterization for coupled groundwater flow and contaminant transport modelling

    USGS Publications Warehouse

    Wagner, B.J.

    1992-01-01

    Parameter estimation and contaminant source characterization are key steps in the development of a coupled groundwater flow and contaminant transport simulation model. Here a methodologyfor simultaneous model parameter estimation and source characterization is presented. The parameter estimation/source characterization inverse model combines groundwater flow and contaminant transport simulation with non-linear maximum likelihood estimation to determine optimal estimates of the unknown model parameters and source characteristics based on measurements of hydraulic head and contaminant concentration. First-order uncertainty analysis provides a means for assessing the reliability of the maximum likelihood estimates and evaluating the accuracy and reliability of the flow and transport model predictions. A series of hypothetical examples is presented to demonstrate the ability of the inverse model to solve the combined parameter estimation/source characterization inverse problem. Hydraulic conductivities, effective porosity, longitudinal and transverse dispersivities, boundary flux, and contaminant flux at the source are estimated for a two-dimensional groundwater system. In addition, characterization of the history of contaminant disposal or location of the contaminant source is demonstrated. Finally, the problem of estimating the statistical parameters that describe the errors associated with the head and concentration data is addressed. A stage-wise estimation procedure is used to jointly estimate these statistical parameters along with the unknown model parameters and source characteristics. ?? 1992.

  3. Reduced order modeling of the Newton formulation of MODFLOW to solve unconfined groundwater flow

    NASA Astrophysics Data System (ADS)

    Boyce, Scott E.; Nishikawa, Tracy; Yeh, William W.-G.

    2015-09-01

    Projection-based model reduction techniques have been shown to be very effective for reducing the computational burden of high-dimensional groundwater simulations, but only applied to confined groundwater flow. A new methodology is proposed that reduces the dimension of a discretized, transient, unconfined groundwater-flow model. This unconfined model reduction technique is based on Galerkin projection and the Newton formulation of MODFLOW. The method is implemented following the standard package design and code structure that MODFLOW employs for all its features. When the package is invoked within MODFLOW it can collect snapshots, produce a basis, construct the reduced model and propagate the reduced model forward in time. The new formulation accurately represents the water-table surface under a variety of nonlinear settings, such as intraborehole flow from a Multi-Node Well. The unconfined model reduction is applied to four test cases to illustrate its flexibility in handling nonlinear features. Several test cases are discussed to demonstrate the unconfined model reduction applicability. The final test case applies the new model reduction methodology to a scoping MODFLOW model of Santa Barbara, CA composed of 113,578 cells, which requires solving 113,578 equations per time step, and reduces it to 127 equations.

  4. 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.

  5. 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.

  6. NONLINEAR-REGRESSION GROUNDWATER FLOW MODELING OF A DEEP REGIONAL AQUIFER SYSTEM.

    USGS Publications Warehouse

    Cooley, Richard L.; Konikow, Leonard F.; Naff, Richard L.

    1986-01-01

    A nonlinear regression groundwater flow model, based on a Galerkin finite-element discretization, was used to analyze steady state two-dimensional groundwater flow in the areally extensive Madison aquifer in a 75,000 mi**2 area of the Northern Great Plains. Regression parameters estimated include intrinsic permeabilities of the main aquifer and separate lineament zones, discharges from eight major springs surrounding the Black Hills, and specified heads on the model boundaries. Aquifer thickness and temperature variations were included as specified functions. The regression model was applied using sequential F testing so that the fewest number and simplest zonation of intrinsic permeabilities, combined with the simplest overall model, were evaluated initially; additional complexities (such as subdivisions of zones and variations in temperature and thickness) were added in stages to evaluate the subsequent degree of improvement in the model results. It was found that only the eight major springs, a single main aquifer intrinsic permeability, two separate lineament intrinsic permeabilities of much smaller values, and temperature variations are warranted by the observed data (hydraulic heads and prior information on some parameters) for inclusion in a model that attempts to explain significant controls on groundwater flow.

  7. Natural and anthropogenic factors affecting the groundwater quality in the Nandong karst underground river system in Yunan, China

    NASA Astrophysics Data System (ADS)

    Jiang, Yongjun; Wu, Yuexia; Groves, Chris; Yuan, Daoxian; Kambesis, Pat

    2009-10-01

    The Nandong Underground River System (NURS) is located in a typical karst agriculture dominated area in the southeast Yunnan Province, China. Groundwater plays an important role for social and economical development in the area. However, with the rapid increase in population and expansion of farm land, groundwater quality has degraded. 42 groundwater samples collected from springs in the NURS showed great variation of chemical compositions across the study basin. With increased anthropogenic contamination in the area, the groundwater chemistry has changed from the typical Ca-HCO 3 or Ca (Mg)-HCO 3 type in karst groundwater to the Ca-Cl (+ NO 3) or Ca (Mg)-Cl (+ NO 3), and Ca-Cl (+ NO 3 + SO 4) or Ca (Mg)-Cl (+ NO 3 + SO 4) type, indicating increases in NO 3-, Cl - and SO 42- concentrations that were caused most likely by human activities in the region. This study implemented the R-mode factor analysis to investigate the chemical characteristics of groundwater and to distinguish the natural and anthropogenic processes affecting groundwater quality in the system. The R-mode factor analysis together with geology and land uses revealed that: (a) contamination from human activities such as sewage effluents and agricultural fertilizers; (b) water-rock interaction in the limestone-dominated system; and (c) water-rock interaction in the dolomite-dominated system were the three major factors contributing to groundwater quality. Natural dissolution of carbonate rock (water-rock interaction) was the primary source of Ca 2+ and HCO 3- in groundwater, water-rock interaction in dolomite-dominated system resulted in higher Mg 2+ in the groundwater, and human activities were likely others sources. Sewage effluents and fertilizers could be the main contributor of Cl -, NO 3-, SO 42-, Na + and K + to the groundwater system in the area. This study suggested that both natural and anthropogenic processes contributed to chemical composition of groundwater in the NURS, human activities

  8. Partitioning groundwater recharge between rainfall infiltration and irrigation return flows using stable isotopes: the Crau aquifer.

    NASA Astrophysics Data System (ADS)

    Seraphin, Pierre; Vallet-Coulomb, Christine; Gonçalvès, Julio

    2016-04-01

    Traditional flood irrigation is used since the 16th century in the Crau plain (Southern France) for hay production. To supply this high consuming irrigation practice, water is diverted from the Durance River, originating from the Alps, and the large amount of irrigation return flows constitutes the main recharge of the Crau aquifer, which is in turn largely exploited for domestic, industrial and agricultural water use. A possible reduction of irrigation fluxes due to a need of water saving or to a future land-use change could endanger the groundwater resource. A robust quantification of the groundwater mass balance is thus required to assess a sustainable water management in the region. The high isotopic contrast between these exogenous irrigation waters and local precipitations allows the use of stable isotopes of water as conservative tracers to deduce their contributions to the surface recharge. An extensive groundwater sampling was performed to obtain δ18O and δ2H over the whole aquifer. Based on a new piezometric contour map, combined with a reestimate of the aquifer geometry, the isotopic data are implemented in a geostatistical approach to produce a conceptual equivalent-homogeneous reservoir, in order to apply a simple water and isotope mass balance mixing model. The isotopic composition of the two end-members is assessed, and the quantification of groundwater flows is then used to calculate the two recharge fluxes. Near to steady-state condition, the set of isotopic data treated by geostatistics leads to a recharge by irrigation of 5.20 ± 0.93 m3 s-1 i.e. 1173 ± 210 mm yr-1, and a natural recharge of 2.26 ± 0.91 m3 s-1 i.e. 132 ± 53 mm yr-1. Thus, 70 ± 9% of the effective surface recharge comes from the irrigation return flow, consistent with the literature (between 67% and 78%). This study constitutes a straightforward and independent approach to assess groundwater surface recharges with uncertainties and will help to constrain a future transient

  9. 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.

  10. wrv: An R Package for Groundwater Flow Model Construction, Wood River Valley Aquifer System, Idaho

    NASA Astrophysics Data System (ADS)

    Fisher, J. C.

    2014-12-01

    Groundwater models are one of the main tools used in the hydrogeological sciences to assess resources and to simulate possible effects from future water demands and changes in climate. The hydrological inputs to groundwater models can be numerous and can vary in both time and space. Difficulties associated with model construction are often related to extensive datasets and cumbersome data processing tasks. To mitigate these difficulties, a graphical user interface (GUI) is often employed to aid the input of data for creating models. Unfortunately, GUI software presents an obstacle to reproducibility, a cornerstone of research. The considerable effort required to document processing steps in a GUI program, and the rapid obsoleteness of these steps with subsequent versions of the software, has prompted modelers to explicitly write down processing steps as source code to make them 'easily' reproducible. This research describes the R package wrv, a collection of datasets and functions for pre- and post-processing the numerical groundwater flow model of the Wood River Valley aquifer system, south-central Idaho. R largely facilitates reproducible modeling with the package vignette; a document that is a combination of content and source code. The code is run when the vignette is built, and all data analysis output (such as figures and tables) is created on the fly and inserted into the final document. The wrv package includes two vignettes that explain and run steps that (1) create package datasets from raw data files located on a publicly accessible repository, and (2) create and run the groundwater flow model. MODFLOW-USG, the numerical groundwater model used in this study, is executed from the vignette, and model output is returned for exploratory analyses. The ability of R to perform all processing steps in a single workflow is attributed to its comprehensive list of features; that include geographic information system and time series functionality.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  12. 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.

  13. Multigrid preconditioned conjugate gradients for the numerical simulation of groundwater flow on the Cray T3D

    SciTech Connect

    Ashby, S.F.; Falgout, R.D.; Smith, S.G.; Fogwell, T.W.

    1994-09-01

    This paper discusses the numerical simulation of groundwater flow through heterogeneous porous media. The focus is on the performance of a parallel multigrid preconditioner for accelerating convergence of conjugate gradients, which is used to compute the hydraulic pressure head. The numerical investigation considers the effects of enlarging the domain, increasing the grid resolution, and varying the geostatistical parameters used to define the subsurface realization. The results were obtained using the PARFLOW groundwater flow simulator on the Cray T3D massively parallel computer.

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

    SciTech Connect

    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.

  15. A moving mesh algorithm for 3-D regional groundwater flow with water table and seepage face

    NASA Astrophysics Data System (ADS)

    Knupp, P.

    A numerical algorithm is described for solving the free-surface groundwater flow equations in 3-D large-scale unconfined aquifers with strongly heterogeneous conductivity and surface recharge. The algorithm uses a moving mesh to track the water-table as it evolves according to kinematic and seepage face boundary conditions. Both steady-state and transient algorithms are implemented in the SECO-Flow 3-D code and demonstrated on stratigraphy based on the Delaware Basin of south-eastern New Mexico.

  16. Ground-Water Flow, 2004-07, and Water Quality, 1992-2007, in McBaine Bottoms, Columbia, Missouri

    USGS Publications Warehouse

    Smith, Brenda Joyce; Richards, Joseph M.

    2008-01-01

    The U.S. Geological Survey, in cooperation with the city of Columbia, Missouri, and the Missouri Department of Conservation, collected ground-water quality data, surface-water quality data, and water-level data in McBaine Bottoms, southwest of Columbia. McBaine Bottoms, adjacent to the Missouri River, is the location of the municipal-supply well field for the city of Columbia, the city of Columbia wastewater-treatment wetlands, and the Missouri Department of Conservation Eagle Bluffs Conservation Area. This report describes the ground-water flow and water quality of McBaine Bottoms and provides information to better understand the interaction between treated effluent from the wetlands used on the Eagle Bluffs Conservation Area and the water in the alluvial aquifer that is pumped from the city of Columbia municipal-supply well field. Changes in major chemical constituent concentrations have been detected at several sampling sites between pre- and post-effluent application data. Analysis of post-effluent data indicates substantial changes in calcium, potassium, sodium, chloride, and sulfate concentrations in ground water. These changes became apparent shortly after the beginning of the operation of the wastewater-treatment wetland in 1994 and the formation of the Eagle Bluffs Conservation Area, which uses the treated effluent as a water source for the management of migratory water fowl. The changes have continued throughout the 15 years of sample collection. The concentrations of these major chemical constituents are on the mixing continuum between pre-effluent ground water as one end member and the treated wastewater effluent as the other end member. For monitoring wells that had changes in major chemical constituent concentrations, the relative percentage of treated effluent in the ground water, assuming chloride is conservative, ranged from 6 to 88 percent. Twenty-two monitoring wells throughout McBaine Bottoms have been affected by effluent based on chloride

  17. Groundwater flow associated with coalbed gas production, Ferron Sandstone, east-central Utah

    USGS Publications Warehouse

    Anna, L.O.

    2003-01-01

    The flow and distribution of water associated with coalbed gas production in the Ferron Sandstone was characterized utilizing a discrete fracture network model and a porous media model. A discrete fracture network model calculated fluid flux through volumes of various scales to determine scale effects, directional bulk permeability, and connectivity. The mean directional permeabilities varied by less than a factor of 6, with the northwest-southeast direction (face cleat direction) as the most conductive. Northwest southeast directed hydrofracture simulations increased permeability in all directions except the northeast-southwest, although the permeability increase was not more than a factor of 3. Cluster analysis showed that the simulated cleat network was very well connected at all simulated scales. For thick coals, the entire cleat network formed one compartment, whereas thin coals formed several compartments. Convex hulls of the compartments confirmed that the directional bulk permeability was nearly isotropic. Volumetric calculations of the Ferron coal indicated that all the water produced to date can be accounted for from the coal cleat porosity system and does not depend on contributions of water from contiguous units.Flow paths, determined from porous media modeling from recharge to discharge, indicate that the three coalbed gas (CBG) fields assessed in this study could have different groundwater chemical compositions as confirmed by geochemical data. Simulated water production from 185 wells from 1993 to 1998 showed that in 1998 the maximum head drawdown from the Drunkards Wash field was more than 365 m, and the cone of depression extended to within a short distance of the Ferron outcrop. Maximum drawdown in the Helper field was 120 m, and the maximum drawdown in the Buzzards Bench field was just over 60 m. The cone of depression for the Helper field was half the size of the Drunkards Wash field, and the cone of depression for the Buzzards Bench field was

  18. Budgets and chemical characterization of groundwater for the Diamond Valley flow system, central Nevada, 2011–12

    USGS Publications Warehouse

    Berger, David L.; Mayers, C. Justin; Garcia, C. Amanda; Buto, Susan G.; Huntington, Jena M.

    2016-01-01

    The pre-development, steady state, groundwater budget for the Diamond Valley flow system was estimated at about 70,000 acre-ft/yr of inflow and outflow. During years 2011–12, inflow components of groundwater recharge from precipitation and subsurface inflow from adjacent basins totaled 70,000 acre-ft/yr for the DVFS, whereas outflow components included 64,000 acre-ft/yr of groundwater evapotranspiration and 69,000 acre-ft/yr of net groundwater withdrawals, or net pumpage. Spring discharge in northern Diamond Valley declined about 6,000 acre-ft/yr between pre-development time and years 2011–12. Assuming net groundwater withdrawals minus spring flow decline is equivalent to the storage change, the 2011–12 summation of inflow and storage change was balanced with outflow at about 133,000 acre-ft/yr.

  19. Assessing controls on diffuse groundwater recharge using unsaturated flow modeling

    NASA Astrophysics Data System (ADS)

    Keese, K. E.; Scanlon, B. R.; Reedy, R. C.

    2005-06-01

    Understanding climate, vegetation, and soil controls on recharge is essential for estimating potential impacts of climate variability and land use/land cover change on recharge. Recharge controls were evaluated by simulating drainage in 5-m-thick profiles using a one-dimensional (1-D) unsaturated flow code (UNSAT-H), climate data, and vegetation and soil coverages from online sources. Soil hydraulic properties were estimated from STATSGO/SSURGO soils data using pedotransfer functions. Vegetation parameters were obtained from the literature. Long-term (1961-1990) simulations were conducted for 13 county-scale regions representing arid to humid climates and different vegetation and soil types, using data for Texas. Areally averaged recharge rates are most appropriate for water resources; therefore Geographic Information Systems were used to determine spatial weighting of recharge results from 1-D models for the combination of vegetation and soils in each region. Simulated 30-year mean annual recharge in bare sand is high (51-709 mm/yr) and represents 23-60% (arid-humid) of mean annual precipitation (MAP). Adding vegetation reduced recharge by factors of 2-30 (humid-arid), and soil textural variability reduced recharge by factors of 2-11 relative to recharge in bare sand. Vegetation and soil textural variability both resulted in a large range of recharge rates within each region; however, spatially weighted, long-term recharge rates were much less variable and were positively correlated with MAP (r2 = 0.85 for vegetated sand; r2 = 0.62 for variably textured soils). The most realistic simulations included vegetation and variably textured soils, which resulted in recharge rates from 0.2 to 118 mm/yr (0.1-10% of MAP). Mean annual precipitation explains 80% of the variation in recharge and can be used to map recharge.

  20. Model Reduction of a Transient Groundwater-Flow Model for Bayesian Inverse Problems

    NASA Astrophysics Data System (ADS)

    Boyce, S. E.; Yeh, W. W.

    2011-12-01

    A Bayesian inverse problem requires many repeated model simulations to characterize an unknown parameter's posterior probability distribution. It is computationally infeasible to solve a Bayesian inverse problem of a discretized groundwater flow model with a high dimension parameter and state space. Model reduction has been shown to reduce the dimension of a groundwater model by several orders of magnitude and is well suited for Bayesian inverse problems. A projection-based model reduction approach is proposed to reduce the parameter and state dimensions of a groundwater model. Previous work has done this by using a greedy algorithm for the selection of parameter vectors that make up a basis and their corresponding steady-state solutions for a state basis. The proposed method extends this idea to include transient models by assembling sequentially though the greedy algorithm the parameter and state projection bases. The method begins with the parameter basis being a single vector that is equal to one or an accepted series of values. A set of state vectors that are solutions to the groundwater model using this parameter vector at appropriate times is called the parameter snapshot set. The appropriate times for the parameter snapshot set are determined by maximizing the set's minimum singular value. This optimization is a similar to those used in experimental design for maximizing information. The two bases are made orthonormal by a QR decomposition and applied to the full groundwater model to form a reduced model. The parameter basis is increased with a new parameter vector that maximizes the error between the full model and the reduced model at a set of observation times. The new parameter vector represents where the reduced model is least accurate in representing the original full model. The corresponding parameter snapshot set's appropriate times are found using a greedy algorithm. This sequentially chooses times that have maximum error between the full and

  1. Revised Multi-Node Well (MNW2) Package for MODFLOW Ground-Water Flow Model

    USGS Publications Warehouse

    Konikow, Leonard F.; Hornberger, George Z.; Halford, Keith J.; Hanson, Randall T.; Harbaugh, Arlen W.

    2009-01-01

    Wells that are open to multiple aquifers can provide preferential pathways to flow and solute transport that short-circuit normal fluid flowlines. Representing these features in a regional flow model can produce a more realistic and reliable simulation model. This report describes modifications to the Multi-Node Well (MNW) Package of the U.S. Geological Survey (USGS) three-dimensional ground-water flow model (MODFLOW). The modifications build on a previous version and add several new features, processes, and input and output options. The input structure of the revised MNW (MNW2) is more well-centered than the original verion of MNW (MNW1) and allows the user to easily define hydraulic characteristics of each multi-node well. MNW2 also allows calculations of additional head changes due to partial penetration effects, flow into a borehole through a seepage face, changes in well discharge related to changes in lift for a given pump, and intraborehole flows with a pump intake located at any specified depth within the well. MNW2 also offers an improved capability to simulate nonvertical wells. A new output option allows selected multi-node wells to be designated as 'observation wells' for which changes in selected variables with time will be written to separate output files to facilitate postprocessing. MNW2 is compatible with the MODFLOW-2000 and MODFLOW-2005 versions of MODFLOW and with the version of MODFLOW that includes the Ground-Water Transport process (MODFLOW-GWT).

  2. Development of a conceptual model of groundwater flow, Chesterfield County, South Carolina

    USGS Publications Warehouse

    Campbell, Bruce G.; Landmeyer, James E.

    2010-01-01

    Chesterfield County is located in the north central part of South Carolina (SC) and is adjacent to the North Carolina border. The County lies along the Fall Line, the geologic boundary between the Atlantic Coastal Plain (ACP) and Piedmont physiographic provinces. Between 2000 and 2007, the population increased from 42,768 to 43,191 people (U.S. Census Bureau, 2007). Associated with this population growth is an increased demand for domestic, public, industrial, and agricultural water supplies. The ACP sediments underlying Chesterfield County contain abundant supplies of highquality groundwater (Newcome, 2004). The U.S. Geological Survey, in cooperation with the South Carolina Department of Natural Resources is investigating the ACP groundwater resources of Chesterfield County. The initial task of the study is to establish a hydrologic data-collection network for the ACP part of the County. A groundwater-flow model and derived water budgets for the ACP aquifer that underlies most of the County will be constructed and calibrated later in the study. Both anthropogenic and natural groundwater contaminants that have been identified in the study area will be quantified and described as part of a companion study.

  3. Ground-water flow paths and traveltime to three small embayments within the Peconic Estuary, eastern Suffolk County, New York

    USGS Publications Warehouse

    Schubert, Christopher E.

    1999-01-01

    The Peconic Estuary, at the eastern end of Long Island, has been plagued by a recurrent algal bloom that has caused the severe decline of local marine resources. Although the onset, duration, and cessation of the bloom remain unpredictable, ground-water discharge has been shown to affect surface-water quality in the western part of the estuary. Results from a study on the North Fork of Long Island indicate that local hydrogeologic factors cause differences in ground-water age and characteristics of discharge to the estuary. The need for information on the local patterns and rates of ground-water discharge to the Peconic Estuary prompted analysis of ground-water flow paths and traveltime to three small embayments within the estuary.Meetinghouse Creek, near the west end of the North Fork; Sag Harbor Cove, in the central part of the South Fork; and West Neck Bay, on Shelter Island. Ground-water-flow models were developed, and particle-tracking procedures were applied to the results of each model, to define the flow paths and traveltime of ground water to the three embayments. The steady-state flow models represent the two-dimensional ground-water-flow system along a vertical section through the uplands of each embayment and simulate long-term hydrologic conditions. The particle-tracking procedure used model-generated ground-water levels and flow rates to calculate the water-particle pathlines and times-of-travel through each flow system from the point of entry (recharge) to the point of exit at streams, the shore, or subsea-discharge areas. Results for the Meetinghouse Creek study area indicate that about 50 percent of the total recharge that enters the system flows southward to Meetinghouse Creek; half of this amount discharges as base flow to the fresh-water reach of the creek, and half as shoreline underflow to the estuarine reach. About 85 percent of the total discharge to Meetinghouse Creek has flowed entirely within the upper glacial aquifer, and about 15

  4. Semi-analytical solution of groundwater flow in a leaky aquifer system subject to bending effect

    NASA Astrophysics Data System (ADS)

    Yu, Chia-Chi; Yang, Shaw-Yang; Yeh, Hund-Der

    2013-04-01

    SummaryThe bending of aquitard like a plate due to aquifer pumping and compression is often encountered in many practical problems of subsurface flow. This reaction will have large influence on the release of the volume of water from the aquifer, which is essential for the planning and management of groundwater resources in aquifers. However, the groundwater flow induced by pumping in a leaky aquifer system is often assumed that the total stress of aquifer maintains constant all the time and the mechanical behavior of the aquitard formation is negligible. Therefore, this paper devotes to the investigation of the effect of aquitard bending on the drawdown distribution in a leaky aquifer system, which is obviously of interest in groundwater hydrology. Based on the work of Wang et al. (2004) this study develops a mathematical model for investigating the impacts of aquitard bending and leakage rate on the drawdown of the confined aquifer due to a constant-rate pumping in the leaky aquifer system. This model contains three equations; two flow equations delineate the transient drawdown distributions in the aquitard and the confined aquifer, while the other describes the vertical displacement in response to the aquitard bending. For the case of no aquitard bending, this new solution can reduce to the Hantush Laplace-domain solution (Hantush, 1960). On the other hand, this solution without the leakage effect can reduce to the time domain solution of Wang et al. (2004). The results show that the aquifer drawdown is influenced by the bending effect at early time and by the leakage effect at late time. The results of sensitivity analysis indicate that the aquifer compaction is sensitive only at early time, causing less amount of water released from the pumped aquifer than that predicted by the traditional groundwater theory. The dimensionless drawdown is rather sensitive to aquitard's hydraulic conductivity at late time. Additionally, both the hydraulic conductivity and

  5. 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.

  6. How does ice sheet loading affect ocean flow around Antarctica?

    NASA Astrophysics Data System (ADS)

    Dijkstra, H. A.; Rugenstein, M. A.; Stocchi, P.; von der Heydt, A. S.

    2012-12-01

    Interactions and dynamical feedbacks between ocean circulation, heat and atmospheric moisture transport, ice sheet evolution, and Glacial Isostatic Adjustment (GIA) are overlooked issues in paleoclimatology. Here we will present first results on how ocean flows were possibly affected by the glaciation of Antarctica across the Eocene-Oligocene Transition (~ 34 Ma) through GIA and bathymetry variations. GIA-induced gravitationally self-consistent bathymetry variations are determined by solving the Sea Level Equation (SLE), which describes the time dependent shape of (i) the solid Earth and (ii) the equipotential surface of gravity. Since the ocean circulation equations are defined relative to the equipotential surface of gravity, only bathymetry variations can influence ocean flows, although the sea surface slope will also change through time due to gravitational attraction. We use the Hallberg Isopycnal Model under late Eocene conditions to calculate equilibrium ocean flows in a domain in which the bathymetry evolves under ice loading according to the SLE. The bathymetric effects of the glaciation of Antarctica lead to substantial spatial changes in ocean flows, and close to the coast, the flow even reverses direction. Volume transports through the Drake Passage and Tasman Seaway adjust to the new bathymetry. The results indicate that GIA-induced ocean flow variations alone may have had an impact on sedimentation and erosion patterns, the repositioning of fronts, ocean heat transport and grounding line and ice sheet stability.

  7. Microbial Community-Level Physiological Profiles (CLPP) and herbicide mineralization potential in groundwater affected by agricultural land use

    NASA Astrophysics Data System (ADS)

    Janniche, Gry Sander; Spliid, Henrik; Albrechtsen, Hans-Jørgen

    2012-10-01

    Diffuse groundwater pollution from agricultural land use may impact the microbial groundwater community, which was investigated as Community-Level Physiological Profiles (CLPP) using EcoPlate™. Water was sampled from seven piezometers and a spring in a small agricultural catchment with diffuse herbicide and nitrate pollution. Based on the Shannon-Wiener and Simpson's diversity indices the diversity in the microbial communities was high. The response from the EcoPlates™ showed which substrates support groundwater bacteria, and all 31 carbon sources were utilized by organisms from at least one water sample. However, only nine carbon sources were utilized by all water samples: D-Mannitol, N-acetyl-D-glucosamine, putrescine, D-galacturonic acid, itaconic acid, 4-hydroxy benzoic acid, tween 40, tween 80, and L-asparagine. In all water samples the microorganisms preferred D-mannitol, D-galacturonic acid, tween 40, and 4-hydroxy benzoic acid as substrates, whereas none preferred 2-hydroxy benzoic acid, α-D-lactose, D,L-α-glycerol phosphate, α-ketobutyric acid, L-threonine and glycyl-L-glutamic acid. Principal Component Analysis of the CLPP's clustered the most agriculturally affected groundwater samples, indicating that the agricultural land use affects the groundwater microbial communities. Furthermore, the ability to mineralize atrazine and isoproturon, which have been used in the catchment, was also associated with this cluster.

  8. Parameter Identification and Uncertainty Analysis for Visual MODFLOW based Groundwater Flow Model in a Small River Basin, Eastern India

    NASA Astrophysics Data System (ADS)

    Jena, S.

    2015-12-01

    The overexploitation of groundwater resulted in abandoning many shallow tube wells in the river Basin in Eastern India. For the sustainability of groundwater resources, basin-scale modelling of groundwater flow is essential for the efficient planning and management of the water resources. The main intent of this study is to develope a 3-D groundwater flow model of the study basin using the Visual MODFLOW package and successfully calibrate and validate it using 17 years of observed data. The sensitivity analysis was carried out to quantify the susceptibility of aquifer system to the river bank seepage, recharge from rainfall and agriculture practices, horizontal and vertical hydraulic conductivities, and specific yield. To quantify the impact of parameter uncertainties, Sequential Uncertainty Fitting Algorithm (SUFI-2) and Markov chain Monte Carlo (MCMC) techniques were implemented. Results from the two techniques were compared and the advantages and disadvantages were analysed. Nash-Sutcliffe coefficient (NSE) and coefficient of determination (R2) were adopted as two criteria during calibration and validation of the developed model. NSE and R2 values of groundwater flow model for calibration and validation periods were in acceptable range. Also, the MCMC technique was able to provide more reasonable results than SUFI-2. The calibrated and validated model will be useful to identify the aquifer properties, analyse the groundwater flow dynamics and the change in groundwater levels in future forecasts.

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

    NASA Astrophysics Data System (ADS)

    Arnold, B. W.; Gardner, P.

    2013-12-01

    Calibration of groundwater flow models for the purpose of evaluating flow and aquifer heterogeneity typically uses observations of hydraulic head in wells and appropriate boundary conditions. Environmental tracers have a wide variety of decay rates and input signals in recharge, resulting in a potentially broad source of additional information to constrain flow rates and heterogeneity. A numerical study was conducted to evaluate the reduction in uncertainty during model calibration using observations of various environmental tracers and combinations of tracers. A synthetic data set was constructed by simulating steady groundwater flow and transient tracer transport in a high-resolution, 2-D aquifer with heterogeneous permeability and porosity using the PFLOTRAN software code. Data on pressure and tracer concentration were extracted at well locations and then used as observations for automated calibration of a flow and transport model using the pilot point method and the PEST code. Optimization runs were performed to estimate parameter values of permeability at 30 pilot points in the model domain for cases using 42 observations of: 1) pressure, 2) pressure and CFC11 concentrations, 3) pressure and Ar-39 concentrations, and 4) pressure, CFC11, Ar-39, tritium, and He-3 concentrations. Results show significantly lower uncertainty, as indicated by the 95% linear confidence intervals, in permeability values at the pilot points for cases including observations of environmental tracer concentrations. The average linear uncertainty range for permeability at the pilot points using pressure observations alone is 4.6 orders of magnitude, using pressure and CFC11 concentrations is 1.6 orders of magnitude, using pressure and Ar-39 concentrations is 0.9 order of magnitude, and using pressure, CFC11, Ar-39, tritium, and He-3 concentrations is 1.0 order of magnitude. Data on Ar-39 concentrations result in the greatest parameter uncertainty reduction because its half-life of 269

  10. 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.

  11. Numerical Study of a Groundwater Flow Cycling Controlled By Seawater Intrusion within Karst Conduit Networks Using Modflow-CFP

    NASA Astrophysics Data System (ADS)

    Xu, Z.; Hu, B. X.; Davis, H.

    2014-12-01

    A groundwater flow cycling process between a submarine spring and an inland fresh water spring has been simulated using the latest research version of MODFLOW-CFP (Conduit Flow Process). Spring Creek Springs and Wakulla Spring, which are located in a marine estuary and 18 km inland, respectively, are two major groundwater discharge spots of Woodville Karst Plain (WKP), North Florida, USA. The two springs are found to be connected with karst conduits networks. Rising sea level may put seawater into the Spring Creek Springs and block groundwater discharge, which, in turn, increases freshwater discharge at Wakulla Spring. Three repeating phases in a karst spring flow cycle were proposed from low rainfall period to heavy rainfall period, and back to low rainfall period. During low rainfall periods, seawater flowed back into the conduits at Spring Creek Spring and freshwater was diverted to Wakulla Spring. After heavy rainfall, seawater was pushed back from Spring Creek Spring conduits. A MODFLOW model for WKP was modified to numerically study the groundwater flow cycling and seawater intrusion for three years. Conduit network distribution, high speed groundwater flow and exchange between conduits and matrix domain were simulated through the MODFLOW-CFP model. Rainfall, springs and creeks discharge data were used to calibrate the model. Simulation results catch very well with measurements, and numerically presented the three-phase groundwater cycling. In additional, simulation results were also supported by temperature data measured in conduits, which reflect precipitation recharge to groundwater, and indicate conduit flow direction. Key Words: Karst, Seawater Instrusion, MODFLOW-CFP, Groundwater Cycling

  12. Inverse Modeling of Groundwater Flow for a Fractured Confined Aquifer

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Wang, D.

    2013-12-01

    A two-dimensional inverse method is developed to simultaneously estimate steady-state hydraulic conductivities, state variables, and boundary conditions (BC) for a fractured confined aquifer. Computation experiments were performed with five fractured models where each model is driven by dominantly lateral flow (true BC) through both fractures (Kf) and matrix (Km). From each model, observation data including hydraulic heads and Darcy fluxes were sampled without imposing measurement errors. These data were provided to inversion to estimate Kf and the unknown model BC. For the first 4 models, the same sampling data density was used, while Kf/Km ratio is fixed at 10. The 1st model contains a single vertical fracture, and the error of the estimated Kf is almost 0. The 2nd model contains a single horizontal fracture, and the error of the estimated Kf is 4.6%. The 3rd model contains a vertical and a horizontal fracture, and the error is 5.3%. The 4th model is same as the third, except that the fracture volume is 25 times greater, and the error is 0.70%. In this model, the highest BC estimation error occurred at the domain corners, where the inversion extrapolation error is the greatest (reduction of this error will be investigated in the future with local grid refinement and increased data density). The 5th model contains a set of diagonal fractures, two of which run from the left bottom corner to the right top corner and the other one runs from the left top corner to the right bottom corner. For this model, under a given data density, increasing Kf/Km (10 to 1,000,000) was tested. Kf estimation is found not to be sensitive to this variability - the largest Kf error is only 5.27%. For the same model, at Kf/Km =10, local sensitivity analysis using 1 percent scaled sensitivity (1ss) suggests that observed heads at different locations are important for estimating different parameters. A global inverse sensitivity analysis was then performed by increasing the number of the

  13. Effects of groundwater withdrawal on borehole flow and salinity measured in deep monitor wells in Hawai'i-implications for groundwater management

    USGS Publications Warehouse

    Rotzoll, Kolja

    2010-01-01

    Water-resource managers in Hawai`i rely heavily on salinity profiles from deep monitor wells to estimate the thickness of freshwater and the depth to the midpoint of the transition zone between freshwater and saltwater in freshwater-lens systems. The deep monitor wells are typically open boreholes below the water table and extend hundreds of feet below sea level. Because of possible borehole-flow effects, there is concern that salinity profiles measured in these wells may not accurately reflect the salinity distribution in the aquifer and consequently lead to misinterpretations that adversely affect water-resource management. Steplike changes in salinity or temperature with depth in measured profiles from nonpumped deep monitor wells may be indicative of water moving within the well, and such changes are evident to some extent in all available profiles. The maximum vertical step length, or displacement, in measured profiles ranges from 7 to 644 feet. Vertical steps longer than 70 feet exceed the typical thickness of massive lava flows; they therefore cannot be attributed entirely to geologic structure and may be indicative of borehole flow. The longest vertical steps occur in monitor wells located in southern O'ahu, coinciding with the most heavily developed part of the aquifer. Although regional groundwater withdrawals have caused a thinning of the freshwater lens over the past several decades, the measured midpoint of the transition zone in most deep monitor wells has shown only inconsequential depth displacement in direct response to short-term variations in withdrawals from nearby production wells. For profiles from some deep monitor wells, however, the depth of the measured top of the transition zone, indicated by a specific-conductance value of 1,000 microsiemens per centimeter, has risen several hundred feet in response to withdrawals from nearby production wells. For these deep monitor wells, monitoring the apparent top of the transition zone may not

  14. 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. 

  15. A statistical processor for analyzing simulations made using the Modular Finite-Difference Ground-water Flow Model

    USGS Publications Warehouse

    Scott, J.C.

    1990-01-01

    Many hydrologic studies of ground-water systems are conducted using a digital computer model as an aid to understanding the flow system. One of the most commonly used ground-water modeling programs is the Modular Three-Dimensional Ground-water Flow Model (Modular Model) by McDonald and Harbaugh. This report presents a computer program to summarize the data input to and output from the Modular Model. The program is named the Modular Model Statistical Processor and is designed to be run following the Modular Model. The Modular Model Statistical Processor provides ground-water modelers with the capabilities to easily read data input to and output from the Modular Model, calculate descriptive statistics, generate histograms, perform logical tests using relational operators, calculate data arrays using arithmetic operators, and calculate flow vectors for use in a graphical-display program.

  16. Development of a numerical model to simulate groundwater flow in the shallow aquifer system of Assateague Island, Maryland and Virginia

    USGS Publications Warehouse

    Masterson, John P.; Fienen, Michael N.; Gesch, Dean B.; Carlson, Carl S.

    2013-01-01

    A three-dimensional groundwater-flow model was developed for Assateague Island in eastern Maryland and Virginia to simulate both groundwater flow and solute (salt) transport to evaluate the groundwater system response to sea-level rise. The model was constructed using geologic and spatial information to represent the island geometry, boundaries, and physical properties and was calibrated using an inverse modeling parameter-estimation technique. An initial transient solute-transport simulation was used to establish the freshwater-saltwater boundary for a final calibrated steady-state model of groundwater flow. This model was developed as part of an ongoing investigation by the U.S. Geological Survey Climate and Land Use Change Research and Development Program to improve capabilities for predicting potential climate-change effects and provide the necessary tools for adaptation and mitigation of potentially adverse impacts.

  17. Use of particle tracking to improve numerical model calibration and to analyze ground-water flow and contaminant migration, Massachusetts Military Reservation, western Cape Cod, Massachusetts

    USGS Publications Warehouse

    Masterson, John P.; Walter, Donald A.; Savoie, Jennifer

    1997-01-01

    A steady-state, three-dimensional flow model coupled with a particle-tracking algorithm was developed to assess the complex interaction of hydrogeologic conditions affecting ground-water flow and contaminant transport--including aquifer heterogeneities, hydrologic boundaries such as ponds and streams, ground-water withdrawals, and aquifer recharge to characterize the migration of contaminants emanating from beneath the Massachusetts Military Reservation, Cape Cod, Massachusetts. The known extent of contaminant plumes were used to assess the effects of changes in model input parameters on model-calculated water-table and pond altitudes, streamflow, and water-particle pathlines. Although changes in selected simulated hydrogeologic conditions resulted in minor changes in model-calculated water-table altitudes, pond altitudes, and streamflow, these changes had significant effects on the projection of model-calculated water-particle pathlines.

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

    SciTech Connect

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

    1995-03-01

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

  19. Migration of contaminants in groundwater at a landfill: A case study. 1. Groundwater flow and plume delineation

    NASA Astrophysics Data System (ADS)

    MacFarlane, D. S.; Cherry, J. A.; Gillham, R. W.; Sudicky, E. A.

    1983-05-01

    A landfill-derived contaminant plume with a maximum width of ˜600 m, a length of ˜700 m and a maximum depth of 20 m in an unconfined sand aquifer was delineated by means of a monitoring network that includes standpipe piezometers, multilevel point-samplers and bundle-piezometers. The extent of detectable contamination caused by the landfill, which began operation in 1940 and which became inactive in 1976, was determined from the distributions of chloride, sulfate and electrical conductance in the sand aquifer, all of which have levels in the leachate that are greatly above those in uncontaminated groundwater. The maximum temperature of groundwater in the zone of contamination beneath the landfill is 12°C, which is 4-5°C above background. The thermal plume in the aquifer extends ˜150 m downgradient from the centre of the landfill. A slight transient water-table mound exists beneath the landfill in the late spring and summer in response to snowmelt and heavy rainfall. Beneath the landfill, the zone of leachate contamination extends to the bottom of the aquifer, apparently because of transient downward components of hydraulic gradient caused by the water-table mound and possibly because of the higher density and lower viscosity of the contaminated water. Values of hydraulic conductivity, which show variations due to local heterogeneity, were obtained from slug tests of piezometers, from pumping tests and from laboratory tests. Because of the inherent uncertainty in the aquifer parameter values, the 38-yr. frontal position of the plume calculated using the Darcy equation with the assumption of plug flow can differ from the observed frontal position by many hundreds of metres, although the use of mean parameter values produces a close agreement. The width of the plume is large relative to the width of the landfill and can be accounted for primarily by variable periods of lateral east- and westward flow caused by changes in water-table configuration due to the

  20. Documentation of a Groundwater Flow Model Developed To Assess Groundwater Availability in the Northern Atlantic Coastal Plain Aquifer System From Long Island, New York, to North Carolina

    USGS Publications Warehouse

    Masterson, John P.; Pope, Jason P.; Fienen, Michael N.; Monti, Jr., Jack; Nardi, Mark R.; Finkelstein, Jason S.

    2016-01-01

    The numerical representation of the hydrogeologic information used in the development of this regional flow model was dependent upon how the aquifer system and simulated hydrologic stresses were discretized in space and time. Lumping hydraulic parameters in space and hydrologic stresses and time-varying observational data in time can limit the capabilities of this tool to simulate how the groundwater flow system responds to changes in hydrologic stresses, particularly at the local scale.

  1. Advances in Fluid Dynamics of Subsurface Flow of Groundwater, Hydrocarbons, and CO2

    NASA Astrophysics Data System (ADS)

    Weyer, K. U.

    2015-12-01

    In the past, the chemical methods of contaminant hydrogeology have dominated much of hydrogeological thinking. In their wake, understanding the physics of subsurface fluid flow and its application to practice and science seemingly has played a secondary role and it often has been replaced by numerical modelling only. Building an understanding of the actual physics of subsurface flow beyond numerical modelling, however, is a confusing experience exposing one to conflicting statements from the sides of engineers, hydrogeologists, and, for a decade or more, by the followers of free convection and density-driven flow. Within the physics of subsurface flow a number of questions arise, such as: Is water really incompressible as assumed in engineering hydraulics? How does buoyancy work? Are underground buoyancy forces generally directed vertically upwards or downwards? What is the consequential difference between hydrostatic and hydrodynamic conditions? What are the force fields causing subsurface flow for water, hydrocarbons and CO2? Is fluid flow really driven by pressure gradients as assumed in reservoir engineering? What is the effect of geothermal gradients on subsurface flow? Do convection cells and free convection exist on-shore? How does variable density flow work? Can today's numerical codes adequately determine variable density flow? Does saltwater really sink to the bottom of geologic systems due to its higher density? Aquitards create confining conditions and thereby confine fluid movements to aquifers? Does more water flow in aquifers than aquitards? The presentation will shed light on the maze of conflicting statements issued within engineering hydraulics and groundwater dynamics. It will also present a field case and its numerical modelling of variable density flow at a major industrial landfill site. The presentation will thereby foster the understanding of the correct physics involved and how this physics can be beneficially applied to practical cases

  2. Imaging lateral groundwater flow in the shallow subsurface using stochastic temperature fields

    NASA Astrophysics Data System (ADS)

    Fairley, Jerry P.; Nicholson, Kirsten N.

    2006-04-01

    Although temperature has often been used as an indication of vertical groundwater movement, its usefulness for identifying horizontal fluid flow has been limited by the difficulty of obtaining sufficient data to draw defensible conclusions. Here we use stochastic simulation to develop a high-resolution image of fluid temperatures in the shallow subsurface at Borax Lake, Oregon. The temperature field inferred from the geostatistical simulations clearly shows geothermal fluids discharging from a group of fault-controlled hydrothermal springs, moving laterally through the subsurface, and mixing with shallow subsurface flow originating from nearby Borax Lake. This interpretation of the data is supported by independent geochemical and isotopic evidence, which show a simple mixing trend between Borax Lake water and discharge from the thermal springs. It is generally agreed that stochastic simulation can be a useful tool for extracting information from complex and/or noisy data and, although not appropriate in all situations, geostatistical analysis may provide good definition of flow paths in the shallow subsurface. Although stochastic imaging techniques are well known in problems involving transport of species, e.g. delineation of contaminant plumes from soil gas survey data, we are unaware of previous applications to the transport of thermal energy for the purpose of inferring shallow groundwater flow.

  3. Hydrogeology and groundwater flow in a basalt-capped Mesozoic sedimentary series of the Ethiopian highlands

    NASA Astrophysics Data System (ADS)

    Vandecasteele, Ine; Nyssen, Jan; Clymans, Wim; Moeyersons, Jan; Martens, Kristine; van Camp, Marc; Gebreyohannes, Tesfamichael; Desmedt, Florimond; Deckers, Jozef; Walraevens, Kristine

    2011-05-01

    A hydrogeological study was undertaken in the Zenako-Argaka catchment, near Hagere Selam in Tigray, northern Ethiopia, during the rainy season of 2006. A geological map was produced through geophysical measurements and field observations, and a fracture zone identified in the north west of the catchment. A perched water table was found within the Trap Basalt series above the laterized upper Aram Aradam Sandstones. A map of this water table was compiled. Water-level variation during the measurement period was at least 4.5 m. Variation in basal flow for the whole catchment for the measurement period was between 12 and 276 m3/day. A groundwater flow model was produced using Visual MODFLOW, indicating the general direction of flow to be towards the south, and illustrating that the waterways have only a limited influence on groundwater flow. The soil water budget was calculated for the period 1995-2006, which showed the important influence of the distribution of rainfall in time. Although Hagere Selam received some 724 mm of rainfall per year over this period, the strong seasonal variation in rainfall meant there was a water deficit for on average 10 months per year.

  4. Two-phase flow numerical simulation of infiltration and groundwater drainage in a rice field

    NASA Astrophysics Data System (ADS)

    Lugomela, G. V.

    Farming of rice normally uses a substantially larger amount of water than other cereal grain crops mainly due to the traditional flooding of rice fields. Flooding of the fields result in a seepage flow condition whereby infiltration occurs at a potential rate. The potential infiltration rate obstructs the free movement of pore-air through the ground surface and gradually compresses the pore-air between the infiltrating wetting front and the groundwater table under which subsurface drains are installed. The Galerkin finite element method (FEM) simulation of two-phase flow of air and water in the porous media of the rice field shows that the subsequent increase in the pore-air pressure makes the pore-air act as a link phase which transfers the effects of the processes taking place in the wetting front above and the saturated zone below the groundwater table. This phenomenon is clearly demonstrated when the results of the two-phase flow simulation are compared to the corresponding single-phase flow simulation which neglects the effect of the pore-air. It is concluded that the ‘ponding’ which appears in rice fields can partly be explained by the resistance offered by the pore-air to the percolation process. The study demonstrates that flooding of rice fields during most of its growth time is not necessary rather it is enough to keep the ground surface just saturated and the rest of the water can be saved.

  5. Driving mechanisms for groundwater flow and salt transport in a subterranean estuary

    NASA Astrophysics Data System (ADS)

    Robinson, C.; Gibbes, B.; Li, L.

    2006-02-01

    This paper presents field measurements and numerical simulations of groundwater dynamics in the intertidal zone of a sandy meso-tidal beach. The study, focusing on vertical hydraulic gradients and pore water salinities, reveals that tides and waves provide important forcing mechanisms for flow and salt transport in the nearshore aquifer. Such forcing, interacting with the beach morphology, enhances the exchange between the aquifer and ocean. The spatial and temporal variations of vertical hydraulic gradients demonstrate the complexity and dynamic nature of the processes and the extent of mixing between fresh groundwater and seawater in a ``subterranean estuary''. These results provide evidence of a potentially important reaction zone in the nearshore aquifer driven by oceanic oscillations. Land-derived contaminants may undergo important biogeochemical transformations in this zone prior to discharge.

  6. Evaluating the sources of water to wells: Three techniques for metamodeling of a groundwater flow model

    USGS Publications Warehouse

    Fienen, Michael N.; Nolan, Bernard T.; Feinstein, Daniel T.

    2016-01-01

    For decision support, the insights and predictive power of numerical process models can be hampered by insufficient expertise and computational resources required to evaluate system response to new stresses. An alternative is to emulate the process model with a statistical “metamodel.” Built on a dataset of collocated numerical model input and output, a groundwater flow model was emulated using a Bayesian Network, an Artificial neural network, and a Gradient Boosted Regression Tree. The response of interest was surface water depletion expressed as the source of water-to-wells. The results have application for managing allocation of groundwater. Each technique was tuned using cross validation and further evaluated using a held-out dataset. A numerical MODFLOW-USG model of the Lake Michigan Basin, USA, was used for the evaluation. The performance and interpretability of each technique was compared pointing to advantages of each technique. The metamodel can extend to unmodeled areas.

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

    USGS Publications Warehouse

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

    2000-01-01

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

  8. Identification of potential groundwater flow paths using geological and geophysical data

    SciTech Connect

    Pohlmann, K.; Andricevic, R.

    1994-09-01

    This project represents the first phase in the development of a methodology for generating three-dimensional equiprobable maps of hydraulic conductivity for the Nevada Test Site (NTS). In this study, potential groundwater flow paths were investigated for subsurface tuffs at Yucca Flat by studying how these units are connected. The virtual absence of site-specific hydraulic conductivity data dictates that as a first step a surrogate attribute (geophysical logs) be utilized. In this first phase, the connectivity patterns of densely welded ash-flow tuffs were studied because these tuffs are the most likely to form zones of high hydraulic conductivity. Densely welded tuffs were identified based on the response shown on resistivity logs and this information was transformed into binary indicator values. The spatial correlation of the indicator data was estimated through geostatistical methods. Equiprobable three-dimensional maps of the distribution of the densely-welded and nonwelded tuffs (i.e., subsurface heterogeneity) were then produced using a multiple indicator simulation formalism. The simulations demonstrate that resistivity logs are effective as soft data for indicating densely welded tuffs. The simulated welded tuffs reproduce the stratigraphic relationships of the welded tuffs observed in hydrogeologic cross sections, while incorporating the heterogeneity and anisotropy that is expected in this subsurface setting. Three-dimensional connectivity of the densely welded tuffs suggests potential groundwater flow paths with lengths easily over 1 km. The next phase of this investigation should incorporate other geophysical logs (e.g., gamma-gamma logs) and then calibrate the resulting soft data maps with available hard hydraulic conductivity data. The soft data maps can then augment the hard data to produce the final maps of the spatial distribution of hydraulic conductivity that can be used as input for numerical solution of groundwater flow and transport.

  9. 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.

  10. Hydrogeologic Settings and Ground-Water Flow Simulations for Regional Studies of the Transport of Anthropogenic and Natural Contaminants to Public-Supply Wells - Studies Begun in 2001

    USGS Publications Warehouse

    Paschke, Suzanne S., (Edited By)

    2007-01-01

    This study of the Transport of Anthropogenic and Natural Contaminants to public-supply wells (TANC study) is being conducted as part of the U.S. Geological Survey National Water Quality Assessment (NAWQA) Program and was designed to increase understanding of the most important factors to consider in ground-water vulnerability assessments. The seven TANC studies that began in 2001 used retrospective data and ground-water flow models to evaluate hydrogeologic variables that affect aquifer susceptibility and vulnerability at a regional scale. Ground-water flow characteristics, regional water budgets, pumping-well information, and water-quality data were compiled from existing data and used to develop conceptual models of ground-water conditions for each study area. Steady-state regional ground-water flow models were used to represent the conceptual models, and advective particle-tracking simulations were used to compute areas contributing recharge and traveltimes from recharge to selected public-supply wells. Retrospective data and modeling results were tabulated into a relational database for future analysis. Seven study areas were selected to evaluate a range of hydrogeologic settings and management practices across the Nation: the Salt Lake Valley, Utah; the Eagle Valley and Spanish Springs Valley, Nevada; the San Joaquin Valley, California; the Northern Tampa Bay region, Florida; the Pomperaug River Basin, Connecticut; the Great Miami River Basin, Ohio; and the Eastern High Plains, Nebraska. This Professional Paper Chapter presents the hydrogeologic settings and documents the ground-water flow models for each of the NAWQA TANC regional study areas that began work in 2001. Methods used to compile retrospective data, determine contributing areas of public-supply wells, and characterize oxidation-reduction (redox) conditions also are presented. This Professional Paper Chapter provides the foundation for future susceptibility and vulnerability analyses in the TANC

  11. Palaeosol control on groundwater flow and pollutant distribution: the example of arsenic.

    PubMed

    McArthur, John M; Nath, Bibhash; Banerjee, Dhiraj M; Purohit, R; Grassineau, N

    2011-02-15

    The consumption of groundwater polluted by arsenic (As) has a severe and adverse effect on human health, particularly where, as happens in parts of SE Asia, groundwater is supplied largely from fluvial/deltaic aquifers. The lateral distribution of the As-pollution in such aquifers is heterogeneous. The cause of the heterogeneity is obscure. The location and severity of the As-pollution is therefore difficult to predict, despite the importance of such predictions to the protection of consumer health, aquifer remediation, and aquifer development. To explain the heterogeneity, we mapped As-pollution in groundwater using 659 wells across 102 km(2) of West Bengal, and logged 43 boreholes, to reveal that the distribution of As-pollution is governed by subsurface sedimentology. Across 47 km(2) of contiguous palaeo-interfluve, we found that the shallow aquifer (<70 mbgl) is unpolluted by As (<10 μg/L) because it is capped by an impermeable palaeosol of red clay (the last glacial maximum palaeosol, or LGMP, of ref 1 ) at depths between 16 and 24 mbgl. The LGMP protects the aquifer from vertical recharge that might carry As-rich water or dissolved organic matter that might drive reduction of sedimentary iron oxides and so release As to groundwater. In 55 km(2) of flanking palaeo-channels, the palaeosol is absent, so invasion of the aquifer by As and dissolved organic matter can occur, so palaeo-channel groundwater is mostly polluted by As (>50 μg/L). The role of palaeosols and, in particular, the LGMP, has been overlooked as a control on groundwater flow and pollutant movement in deltaic and coastal aquifers worldwide. Models of pollutant infiltration in such environments must include the appreciation that, where the LGMP (or other palaeosols) are present, recharge moves downward in palaeo-channel regions that are separated by palaeo-interfluvial regions where vertical recharge to underlying aquifers cannot occur and where horizontal flow occurs above the LGMP and any

  12. Numerical investigation for the impact of CO2 geologic sequestration on regional groundwater flow

    SciTech Connect

    Yamamoto, H.; Zhang, K.; Karasaki, K.; Marui, A.; Uehara, H.; Nishikawa, N.

    2009-04-15

    Large-scale storage of carbon dioxide in saline aquifers may cause considerable pressure perturbation and brine migration in deep rock formations, which may have a significant influence on the regional groundwater system. With the help of parallel computing techniques, we conducted a comprehensive, large-scale numerical simulation of CO{sub 2} geologic storage that predicts not only CO{sub 2} migration, but also its impact on regional groundwater flow. As a case study, a hypothetical industrial-scale CO{sub 2} injection in Tokyo Bay, which is surrounded by the most heavily industrialized area in Japan, was considered, and the impact of CO{sub 2} injection on near-surface aquifers was investigated, assuming relatively high seal-layer permeability (higher than 10 microdarcy). A regional hydrogeological model with an area of about 60 km x 70 km around Tokyo Bay was discretized into about 10 million gridblocks. To solve the high-resolution model efficiently, we used a parallelized multiphase flow simulator TOUGH2-MP/ECO2N on a world-class high performance supercomputer in Japan, the Earth Simulator. In this simulation, CO{sub 2} was injected into a storage aquifer at about 1 km depth under Tokyo Bay from 10 wells, at a total rate of 10 million tons/year for 100 years. Through the model, we can examine regional groundwater pressure buildup and groundwater migration to the land surface. The results suggest that even if containment of CO{sub 2} plume is ensured, pressure buildup on the order of a few bars can occur in the shallow confined aquifers over extensive regions, including urban inlands.

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

    USGS Publications Warehouse

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

    2010-01-01

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

  14. Modeling Groundwater Flow and Infiltration at Potential Low-Level Radioactive Waste Disposal Sites in Taiwan

    NASA Astrophysics Data System (ADS)

    Arnold, B. W.; Lee, C.; Ma, C.; Knowlton, R. G.

    2006-12-01

    Taiwan is evaluating representative sites for the potential disposal of low-level radioactive waste (LLW), including consideration of shallow land burial and cavern disposal concepts. A representative site for shallow land burial is on a small island in the Taiwan Strait with basalt bedrock. The shallow land burial concept includes an engineered cover to limit infiltration into the waste disposal cell. A representative site for cavern disposal is located on the southeast coast of Taiwan. The tunnel system for this disposal concept would be several hundred meters below the mountainous land surface in argillite bedrock. The LLW will consist of about 966,000 drums, primarily from the operation and decommissioning of four nuclear power plants. Sandia National Laboratories and the Institute of Nuclear Energy Research have collaborated to develop performance assessment models to evaluate the long-term safety of LLW disposal at these representative sites. Important components of the system models are sub-models of groundwater flow in the natural system and infiltration through the engineered cover for the shallow land burial concept. The FEHM software code was used to simulate groundwater flow in three-dimensional models at both sites. In addition, a higher-resolution two-dimensional model was developed to simulate flow through the engineered tunnel system at the cavern site. The HELP software was used to simulate infiltration through the cover at the island site. The primary objective of these preliminary models is to provide a modeling framework, given the lack of site-specific data and detailed engineering design specifications. The steady-state groundwater flow model at the island site uses a specified recharge boundary at the land surface and specified head at the island shoreline. Simulated groundwater flow vectors are extracted from the FEHM model along a cross section through one of the LLW disposal cells for utilization in radionuclide transport simulations in

  15. 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.

  16. ENVIRONMENTAL RESEARCH BRIEF: SPATIAL HETEROGENEITY OF GEOCHEMICAL AND HYDROLOGIC PARAMETERS AFFECTING METAL TRANSPORT IN GROUNDWATER

    EPA Science Inventory

    Reliable assessment of the hazards or risks arising from groundwater contamination and the design of effective means of rehabilitation of contaminated sites requires the capability to predict the movement and fate of dissolved solutes in groundwater. he modeling of metal transpor...

  17. Temporal dynamics of groundwater-dissolved inorganic carbon beneath a drought-affected braided stream: Platte River case study

    NASA Astrophysics Data System (ADS)

    Boerner, Audrey R.; Gates, John B.

    2015-05-01

    Impacts of environmental changes on groundwater carbon cycling are poorly understood despite their potentially high relevance to terrestrial carbon budgets. This study focuses on streambed groundwater chemistry during a period of drought-induced river drying and consequent disconnection between surface water and groundwater. Shallow groundwater underlying vegetated and bare portions of a braided streambed in the Platte River (Nebraska, USA) was monitored during drought conditions in summer 2012. Water temperature and dissolved inorganic carbon (dominated by HCO3-) in streambed groundwater were correlated over a 3 month period coinciding with a decline in river discharge from 35 to 0 m3 s-1. Physical, chemical, and isotopic parameters were monitored to investigate mechanisms affecting the HCO3- trend. Equilibrium thermodynamic modeling suggests that an increase of pCO2 near the water table, coupled with carbonate mineral weathering, can explain the trend. Stronger temporal trends in Ca2+ and Mg2+ compared to Cl- are consistent with carbonate mineral reequilibria rather than evaporative concentration as the primary mechanism of the increased HCO3-. Stable isotope trends are not apparent, providing further evidence of thermodynamic controls rather than evaporation from the water table. A combination of increased temperature and O2 in the dewatered portion of the streambed is the most likely driver of increased pCO2 near the water table. Results of this study highlight potential linkages between surface environmental changes and groundwater chemistry and underscore the need for high-resolution chemical monitoring of alluvial groundwater in order to identify environmental change impacts.

  18. Conceptualization of groundwater flow of a coastal arid aquifer using isotopic and chemical tools: La Paz, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Tamez-Melendez, Carol; Hernández-Antonio, Arturo; Mahlknecht, Jürgen

    2016-04-01

    Groundwater from the La Paz coastal aquifer in Baja California Sur, Mexico, is the main source of drinking water for the local population. Due to its proximity to the coast, sea water intrusion is the main factor of salinization of groundwater. Other geochemical processes also affect the quality of the aquifer threating its vulnerability. Forty-seven samples were analyzed for ion chemistry and isotopes. A hierarchical cluster analysis was performed for a better interpretation resulting in three main groups and proved for geographical correspondence. Deuterium and d18O ranged from -82 to -52.1 and from -11.6 to -7 permil, respectively, showing that the main recharge originates in the Sierra el Novillo, flowing toward SE-NW direction and in accordance to deuterium excess (d) high evaporation effects (d>10‰) are mostly in the middle portion of the study area and in El Centenario due to high kinetic isotope fractioning related to elevated temperatures. Hydrogeochemistry analyses demonstrated salinization mainly due to sea water intrusion and in second instance due water-rock interaction, where enrichment of Na+ (ranges from 35.7 to 1089 mg/L-1) was present in some samples probably due to weathering of silicates and/or cation exchange in soils with Ca2+ (27.7 to 658 mg/L-1) at clay-surfaces. High concentrations of NO3-2 (ranges from 1.4 to 48.8 mg/L-1), Cl- (ranges from 54.4 to 2960 mg/L-1) and Na+ show that anthropogenic input is mainly coming from an agricultural area (El Centenario-Chametla) where heavy groundwater extractions are made for irrigational purposes, lowering the groundwater table up to 10 m and consequently promoting upconing and salinity concentrations (NaCl). Carbon-13 and radiocarbon ranged from -12.3 to -9.1‰ and from 29.5 to 100.4 pmC, respectively. Distribution of ages (up to ~5000 years) indicates two flow trends (E-W and SE-NW).

  19. Spatial and temporal constraints on regional-scale groundwater flow in the Pampa del Tamarugal Basin, Atacama Desert, Chile

    NASA Astrophysics Data System (ADS)

    Jayne, Richard S.; Pollyea, Ryan M.; Dodd, Justin P.; Olson, Elizabeth J.; Swanson, Susan K.

    2016-08-01

    Aquifers within the Pampa del Tamarugal Basin (Atacama Desert, northern Chile) are the sole source of water for the coastal city of Iquique and the economically important mining industry. Despite this, the regional groundwater system remains poorly understood. Although it is widely accepted that aquifer recharge originates as precipitation in the Altiplano and Andean Cordillera to the east, there remains debate on whether recharge is driven primarily by near-surface groundwater flow in response to periodic flood events or by basal groundwater flux through deep-seated basin fractures. In addressing this debate, the present study quantifies spatial and temporal variability in regional-scale groundwater flow paths at 20.5°S latitude by combining a two-dimensional model of groundwater and heat flow with field observations and δ18O isotope values in surface water and groundwater. Results suggest that both previously proposed aquifer recharge mechanisms are likely influencing aquifers within the Pampa del Tamarugal Basin; however, each mechanism is operating on different spatial and temporal scales. Storm-driven flood events in the Altiplano readily transmit groundwater to the eastern Pampa del Tamarugal Basin through near-surface groundwater flow on short time scales, e.g., 100-101 years, but these effects are likely isolated to aquifers in the eastern third of the basin. In addition, this study illustrates a physical mechanism for groundwater originating in the eastern highlands to recharge aquifers and salars in the western Pampa del Tamarugal Basin over timescales of 104-105 years.

  20. 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

  1. Groundwater flow and transport modeling: A case study of alluvial aquifer in the Tuul River Basin, Mongolia

    NASA Astrophysics Data System (ADS)

    Dandar, Enkhbayar; Carrera, Jesús; Nemer, Buyankhishig

    2016-04-01

    The Tuul River basin is located northern Mongolia. It includes Ulaanbaatar city, which hosts 48% of Mongolian population. Water supply to the city relies exclusively on groundwater withdrawn from alluvial aquifers along the Tuul River Basin. Water demand of the city has increased recently as a result of rapid industrial development and population growth due to migration from rural areas. The aim of this study is to characterize the aquifer by integrating existing data in a flow model. Unfortunately, existing data are not sufficient for unequivocal identification of model parameters (groundwater recharge, permeability, lateral inflow, etc.). Fluctuations of water temperature have been recognized as a natural tracer that may be used for hydrogeological characterization and model calibration. Temperatures within the aquifer are affected by the temperature of inflowing water as well as by conduction from the soil surface, which we suspect may control aquifer temperatures. Properly acknowledging these fluctuations would require a three dimensional model. Instead, we propose a semianalytical solution based on the use of memory and influence functions.

  2. Geochemical evidence of groundwater flow paths and the fate and transport of constituents of concern in the alluvial aquifer at Fort Wingate Depot Activity, New Mexico, 2009

    USGS Publications Warehouse

    Robertson, Andrew J.; Henry, David W.; Langman, Jeffery B.

    2013-01-01

    As part of an environmental investigation at Fort Wingate Depot Activity, New Mexico, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, interpreted aqueous geochemical concentrations to better understand the groundwater flow paths and the fate and transport of constituents of concern in the alluvial aquifer underlying the study area. The fine-grained nature of the alluvial matrix creates a highly heterogeneous environment, which adds to the difficulty of characterizing the flow of groundwater and the fate of aqueous constituents of concern. The analysis of the groundwater geochemical data collected in October 2009 provides evidence that is used to identify four groundwater flow paths and their extent in the aquifer and indicates the dominant attenuation processes for the constituents of concern. The extent and interaction of groundwater flow paths were delineated by the major ion concentrations and their relations to each other. Four areas of groundwater recharge to the study area were identified based on groundwater elevations, hydrogeologic characteristics, and geochemical and isotopic evidence. One source of recharge enters the study area from the saturated alluvial deposits underlying the South Fork of the Puerco River to the north of the study area. A second source of recharge is shown to originate from a leaky cistern containing production water from the San Andres-Glorieta aquifer. The other two sources of recharge are shown to enter the study area from the south: one from an arroyo valley draining an area to the south and one from hill-front recharge that passes under the reported release of perchlorate and explosive constituents. The spatial extent and interaction of groundwater originating from these various sources along identified flow paths affect the persistence and attenuation of constituents of concern. It was determined that groundwater originating in the area of a former explosives’ wash-out operation and an

  3. Temperature change affected groundwater quality in a confined marine aquifer during long-term heating and cooling.

    PubMed

    Saito, Takeshi; Hamamoto, Shoichiro; Ueki, Takashi; Ohkubo, Satoshi; Moldrup, Per; Kawamoto, Ken; Komatsu, Toshiko

    2016-05-01

    Global warming and urbanization together with development of subsurface infrastructures (e.g. subways, shopping complexes, sewage systems, and Ground Source Heat Pump (GSHP) systems) will likely cause a rapid increase in the temperature of relatively shallow groundwater reservoirs (subsurface thermal pollution). However, potential effects of a subsurface temperature change on groundwater quality due to changed physical, chemical, and microbial processes have received little attention. We therefore investigated changes in 34 groundwater quality parameters during a 13-month enhanced-heating period, followed by 14 months of natural or enhanced cooling in a confined marine aquifer at around 17 m depth on the Saitama University campus, Japan. A full-scale GSHP test facility consisting of a 50 m deep U-tube for circulating the heat-carrying fluid and four monitoring wells at 1, 2, 5, and 10 m from the U-tube were installed, and groundwater quality was monitored every 1-2 weeks. Rapid changes in the groundwater level in the area, especially during the summer, prevented accurate analyses of temperature effects using a single-well time series. Instead, Dual-Well Analysis (DWA) was applied, comparing variations in subsurface temperature and groundwater chemical concentrations between the thermally-disturbed well and a non-affected reference well. Using the 1 m distant well (temperature increase up to 7 °C) and the 10 m distant well (non-temperature-affected), the DWA showed an approximately linear relationships for eight components (B, Si, Li, dissolved organic carbon (DOC), Mg(2+), NH4(+), Na(+), and K(+)) during the combined 27 months of heating and cooling, suggesting changes in concentration between 4% and 31% for a temperature change of 7 °C. PMID:26938497

  4. Simulation of ground-water flow and potential land subsidence, upper Santa Cruz Basin, Arizona

    USGS Publications Warehouse

    Hanson, R.T.; Benedict, J.F.

    1994-01-01

    A numerical ground-water flow model of the upper Santa Cruz basin in Pinal, Pima, and Santa Cruz Counties was developed to evaluate predevelopment conditions in 1940, ground-water withdrawals for 1940-86, and potential water-level declines and land subsidence for 1987-2024. Simulations of steady-state ground-water conditions indicate 12,900 acre-feet of ground-water inflow, 15,260 acre-feet of outflow, 53,000 acre-feet of pre- development pumpage, 29,840 acre-feet of mountain- front recharge, and 34,020 acre-feet of streamflow infiltration in 1940. Simulations of transient ground-water conditions indicate a total of 6.6 million acre-feet of net pumpage and 3.4 million acre-feet of water removed from aquifer storage for 1941-86. A difference of 1.2 million acre-feet between estimated and net pumpage is attributed to increased recharge from irrigation return flow, mine return flow, and infiltration of sewage effluent. Estimated natural recharge represents 40 percent of pumpage for 1966-86 and averaged 63,860 acre-feet per year for 1940-57 and 76,250 acre-feet per year for 1958-86. The increase in recharge after 1958 was coincident with above- average winter streamflow in the Santa Cruz River for 1959-86. Increased recharge after 1958 and decreased pumpage after 1975 contributed to decreased water-level declines or to recoveries after 1977 in wells near the Santa Cruz River and its tributaries. The results of projection simu- lations indicate that a maximum potential subsi- dence for 1987-2024 ranges from 1.2 feet for an inelastic specific storage of .0001 ft to 12 feet for an inelastic specific storage of .0015 ft. The simulations were made on the basis of pumpage and recharge rates from 1986 and by using a preconso- lidation-stress threshold of 100 feet. A permanent reduction in acquitard storage can range from 1 to 12 percent of the potential loss of 3.9 million acre-feet in aquifer-system storage for 1987-2024.

  5. Approximate analytic solutions to 3D unconfined groundwater flow within regional 2D models

    NASA Astrophysics Data System (ADS)

    Luther, K.; Haitjema, H. M.

    2000-04-01

    We present methods for finding approximate analytic solutions to three-dimensional (3D) unconfined steady state groundwater flow near partially penetrating and horizontal wells, and for combining those solutions with regional two-dimensional (2D) models. The 3D solutions use distributed singularities (analytic elements) to enforce boundary conditions on the phreatic surface and seepage faces at vertical wells, and to maintain fixed-head boundary conditions, obtained from the 2D model, at the perimeter of the 3D model. The approximate 3D solutions are analytic (continuous and differentiable) everywhere, including on the phreatic surface itself. While continuity of flow is satisfied exactly in the infinite 3D flow domain, water balance errors can occur across the phreatic surface.

  6. Evaluation of Geochemical Processes Affecting Uranium Sequestration and Longevity of Permeable Reactive Barriers for Groundwater Remediation

    NASA Astrophysics Data System (ADS)

    Fuller, C. C.; Webb, S.; Bargar, J.; Naftz, D. L.

    2009-12-01

    Development of effective remediation techniques for protecting existing drinking water supplies and for mitigating existing contamination problems requires evaluating both the contaminant sequestration processes and the secondary reactions affecting the long term stability of contaminant attenuation. Permeable reactive barriers (PRB) provide a means for passive remediation of dissolved groundwater contaminants and may be an effective strategy for remediation of uranium (U) groundwater contamination provided that long term stability of the sequestered U can be achieved for the geochemical conditions of the aquifer expected subsequent to remediation. Understanding the chemical reaction mechanisms resulting in U uptake and PRB performance are critical to evaluating the potential for release of sequestered U and for improved design of remediation devices. We are using synchrotron X-ray techniques to investigate U sequestration reaction mechanisms and biogeochemical processes in PRB materials recovered from a 9-year field demonstration of zero-valent iron (ZVI) and bone char apatite PRBs in a U contaminated aquifer near Fry Canyon, Utah. X-ray microprobe mapping of iron phases shows that extensive secondary precipitation of mackinawite, siderite and aragonite in the ZVI PRB has resulted from ZVI corrosion coupled with microbial sulfate reduction. Bulk U-EXAFS measurements and micron-scale U-oxidation state mapping indicates that U removal occurs largely by reduction and precipitation of a UO2-like U(IV) phase on the ZVI surfaces, and that the sequestered U is often buried by the secondary Fe precipitates. These findings are significant to the efficacy of ZVI PRBs for remediation of U and other contaminants in that the ongoing secondary phase precipitation cements grains and fills internal porosity resulting in the observed decreased PRB permeability and limits subsequent U removal, but likely limits oxidative remobilization of U. In the bone char apatite PRB, elevated

  7. Metals in Particulate Pollutants Affect Peak Expiratory Flow of Schoolchildren

    PubMed Central

    Hong, Yun-Chul; Hwang, Seung-Sik; Kim, Jin Hee; Lee, Kyoung-Ho; Lee, Hyun-Jung; Lee, Kwan-Hee; Yu, Seung-Do; Kim, Dae-Seon

    2007-01-01

    Background The contribution of the metal components of particulate pollutants to acute respiratory effects has not been adequately evaluated. Moreover, little is known about the effects of genetic polymorphisms of xenobiotic metabolism on pulmonary function. Objectives This study was conducted to assess lung function decrement associated with metal components in particulate pollutants and genetic polymorphisms of glutathione S-transferase M1 and T1. Methods We studied 43 schoolchildren who were in the 3rd to 6th grades. Each student measured peak expiratory flow rate three times a day for 42 days. Particulate air concentrations were monitored every day, and the concentrations of iron, manganese, lead, zinc, and aluminum in the particles were measured. Glutathione S-transferase M1 and T1 genetic polymorphisms were determined using DNA extracted from participant buccal washings. We used a mixed linear regression model to estimate the association between peak expiratory flow rate and particulate air pollutants. Results We found significant reduction in the peak expiratory flow rate after the children’s exposure to particulate pollutants. The effect was shown most significantly 1 day after exposure to the ambient particles. Manganese and lead in the particles also reduced the peak expiratory flow rate. Genetic polymorphisms of glutathione S-transferase M1 and T1 did not significantly affect peak expiratory flow rate. Conclusions This study demonstrated that particulate pollutants and metals such as manganese and lead in the particles are associated with a decrement of peak expiratory flow rate. These effects were robust even with consideration of genetic polymorphisms of glutathione S-transferase. PMID:17431494

  8. Groundwater contributions of flow, nitrate, and dissolved organic carbon to the lower San Joaquin River, California, 2006-08

    USGS Publications Warehouse

    Zamora, Celia; Dahlgren, Randy A.; Kratzer, Charles R.; Downing, Bryan D.; Russell, Ann D.; Dileanis, Peter D.; Bergamaschi, Brian A.; Phillips, Steven P.

    2013-01-01

    groundwater samples collected from the in-stream wells as part of the synoptic surveys. Only 7 of the 113 cross-sectional transects had nitrate concentrations greater than 1 mg/L as N. In contrast, surface waters in the San Joaquin River tended to have nitrate concentrations in the 1–3 mg/L as N range. A zone of lower oxygen (less than 2 mg/L) in the streambed could limit nitrate contributions from regional groundwater flow because nitrate can be converted to nitrogen gas within this zone. Appreciable concentrations of ammonium (average concentration was 1.92 mg/L as N, and 95th percentile was 10.34 mg/L as N) in the shallow groundwater, believed to originate from anoxic mineralization of streambed sediments, could contribute nitrogen to the overlying stream as nitrate following in-stream nitrification, however. Dissolved organic carbon concentrations were highly variable in the shallow groundwater below the river (1 to 6 ft below streambed) and generally ranged between 1 and 5 mg/L, but had maximum concentrations in the 15–25 mg/L range. The longitudinal profile surveys were not particularly useful in identifying groundwater discharge areas. However, the longitudinal approach described in this report was useful as a baseline survey of measured water-quality parameters and for identifying tributary inflows that affect surface-water concentrations of nitrate. Results of the calibrated MODFLOW model indicated that the simulated groundwater discharge rate was approximately 1.0 cubic foot per second per mile (cfs/mi), and the predominant horizontal groundwater flow direction between the deep bank wells was westward beneath the river. The modeled (VS2DH) flux values (river gain versus river loss) were calculated for the irrigation and non-irrigation season, and these fluxes were an order of magnitude less than those from MODFLOW. During the irrigation season, the average river gain was 0.11 cfs/mi, and the average river loss was −0.05 cfs/mi. During the non-irrigation season

  9. Understanding response times and groundwater flow dynamics of thaw zone (talik) evolution below lakes in the Yukon Flats, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Wellman, T. P.; Minsley, B. J.; Voss, C. I.; Walvoord, M. A.

    2013-12-01

    In cold regions, hydrologic systems possess seasonal and perennial ice-free zones (taliks) within areas of permafrost that control and are enhanced by groundwater flow. Simulation of talik development that follows lake formation in watersheds modeled after those in the Yukon Flats of interior Alaska (USA) provides insight on the coupled interaction between groundwater flow and ice distribution. The SUTRA groundwater simulator with freeze-thaw physics is used to examine the effect of climate, lake size, and lake-groundwater relations on talik formation. Considering a range of these factors, simulated times for a through-going sub-lake talik to form through 90 m of permafrost range from ~200 to >1,000 years (vertical thaw rates <0.1-0.5 m yr^-1). Seasonal temperature cycles along lake margins impact supra-permafrost flow and late-stage cryologic processes. Warmer climate accelerates complete permafrost thaw and enhances seasonal flow within the supra-permafrost layer. Prior to open talik formation, sub-lake permafrost thaw is dominated by heat conduction. When hydraulic conditions induce upward or downward flow between the lake and sub-permafrost aquifer, thaw rates are greatly increased. The complexity of ground-ice and water-flow interplay, together with anticipated warming in the arctic, underscores the utility of coupled groundwater-energy transport models in evaluating hydrologic systems impacted by permafrost.

  10. Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain

    USGS Publications Warehouse

    Doyle, Jessica M.; Gleeson, Tom; Manning, Andrew H.; Mayer, K. Ulrich

    2015-01-01

    Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used