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)

Flow and storage in groundwater systems.

PubMed

Alley, William M; Healy, Richard W; LaBaugh, James W; Reilly, Thomas E

2002-06-14

The dynamic nature of groundwater is not readily apparent, except where discharge is focused at springs or where recharge enters sinkholes. Yet groundwater flow and storage are continually changing in response to human and climatic stresses. Wise development of groundwater resources requires a more complete understanding of these changes in flow and storage and of their effects on the terrestrial environment and on numerous surface-water features and their biota.

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.

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

USGS Publications Warehouse

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

2007-01-01

avenues of ground-water flow. Prior to this investigation, the conceptual model of ground-water flow for the region focused primarily on bedding planes and strike-parallel faults and joints as controls on ground-water flow but did not recognize the importance of cross-strike faults and fracture zones that allow ground water to flow downgradient across or through less permeable geologic formations. Results of the ground-water flow simulation indicate that current operations at the Center do not substantially affect either streamflow (less than a 5-percent reduction in annual streamflow) or ground-water levels in the Leetown area under normal climatic conditions but potentially could have greater effects on streamflow during long-term drought (reduction in streamflow of approximately 14 percent). On the basis of simulation results, ground-water withdrawals based on the anticipated need for an additional 150 to 200 gal/min (gallons per minute) of water at the Center also would not seriously affect streamflow (less than 8 to 9 percent reduction in streamflow) or ground-water levels in the area during normal climatic conditions. During drought conditions, however, the effects of current ground-water withdrawals and anticipated additional withdrawals of 150 to 200 gal/min to augment existing supplies result in moderate to substantial declines in water levels of 0.5-1.2 feet (ft) in the vicinity of the Center's springs and production wells. Streamflow was predicted to be reduced locally by approximately 21 percent. Such withdrawals during a drought or prolonged period of below normal ground-water levels would result in substantial declines in the flow of the Center's springs and likely would not be sustainable for more than a few months. The drought simulated in this model was roughly equivalent to the more than 1-year drought that affected the region from November 1998 through February 2000. The potential reduction in streamflow is a result of capture of ground water tha

Effects of warming on groundwater flow in mountainous snowmelt-dominated catchments

NASA Astrophysics Data System (ADS)

Evans, S. G.; Ge, S.; Molotch, N. P.

2015-12-01

In mountainous regions, warmer air temperatures have led to an earlier onset of spring snowmelt and lower snowmelt rates; i.e. because snowmelt has shifted earlier when energy availability is lower. These changes to snowmelt will likely affect the partitioning of snowmelt water between surface runoff and groundwater flow, and therefore, the lag time between snowmelt and streamflow. While the connection between snowmelt and surface runoff has been well-studied, the impact of snowmelt variability on groundwater flow processes has received limited attention, especially in mountainous catchments. We construct a two-dimensional, finite element, coupled flow and heat transport hydrogeologic model to evaluate how changes in snowmelt onset and rate may alter groundwater discharge to streams in mountainous catchments. The coupled hydrogeologic model simulates seasonally frozen ground by incorporating permeability variation as a function of temperature and allows for modeling of pore water freeze and thaw. We apply the model to the Green Lakes Valley (GLV) watershed in the Rocky Mountains of Colorado, a representative snowmelt-dominated catchment. Snowmelt for the GLV catchment is reconstructed from a 12 year (1996-2007) dataset of hydrometeorological records and satellite-derived snow covered area. Modeling results suggest that on a yearly cycle, groundwater infiltration and discharge is limited by the seasonally frozen subsurface. Under average conditions from 1996 to 2007, maximum groundwater discharge to the surface lags maximum snowmelt by approximately two months. Ongoing modeling is exploring how increasing air temperatures affect lag times between snowmelt and groundwater discharge to streams. This study has implications for water resource availability and its temporal variability in a warming global climate.

Heat and Groundwater Flow in the San Gabriel Mountains, California

NASA Astrophysics Data System (ADS)

Newman, A. A.; Becker, M.; Laton, W. R., Jr.

2017-12-01

Groundwater flow paths in mountainous terrain often vary widely in both time and space. Such systems remain difficult to characterize due to fracture-dominated flow paths, high topographic relief, and sparse hydrologic data. We develop a hydrogeologic conceptual model of the Western San Gabriel Mountains in Southern California based on geophysical, thermal, and hydraulic head data. Boreholes are located along the San Gabriel Fault Zone (SGFZ) and cover a wide range of elevations to capture the heterogeneity of the hydrogeologic system. Long term (2016-2017) monitoring of temperature and hydraulic head was carried out in four shallow (300-600m depth) boreholes within the study area using fiber-optic distributed temperature sensing (DTS). Borehole temperature profiles were used to assess the regional groundwater flow system and local flows in fractures intersecting the borehole. DTS temperature profiles were compared with available borehole geophysical logs and head measurements collected with grouted vibrating wire pressure transducers (VWPT). Spatial and temporal variations in borehole temperature profiles suggest that advective heat transfer due to fluid flow affected the subsurface thermal regime. Thermal evidence of groundwater recharge and/or discharge and flow through discrete fractures was found in all four boreholes. Analysis of temporal changes to the flow system in response to seasonal and drilling-induced hydraulic forcing was useful in reducing ambiguities in noisy datasets and estimating interborehole relationships. Acoustic televiewer logs indicate fractures were primarily concentrated in densely fractured intervals, and only a minor decrease of fracture density was observed with depth. Anomalously high hydraulic gradients across the SGFZ suggest that the feature is a potential barrier to lateral flow. However, transient thermal anomalies consistent with groundwater flow within the SGFZ indicate this feature may be a potential conduit to vertical flow

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.

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.

Evaluating groundwater flow using passive electrical measurements

NASA Astrophysics Data System (ADS)

Voytek, E.; Revil, A.; Singha, K.

2016-12-01

Accurate quantification of groundwater flow patterns, both in magnitude and direction, is a necessary component of evaluating any hydrologic system. Groundwater flow patterns are often determined using a dense network of wells or piezometers, which can be limited due to logistical or regulatory constraints. The self-potential (SP) method, a passive geophysical technique that relies on currents generated by water movement through porous materials, is a re-emerging alternative or addition to traditional piezometer networks. Naturally generated currents can be measured as voltage differences at the ground surface using only two electrodes, or a more complex electrode array. While the association between SP measurements and groundwater flow was observed as early as 1890s, the method has seen resurgence in hydrology since the governing equations were refined in the 1980s. The method can be used to analyze hydrologic processes at various temporal and spatial scales. Here we present the results of multiple SP surveys collected a multiple scales (1 to 10s of meters). Here single SP grid surveys are used to evaluate flow patterns through artic hillslopes at a discrete point in time. Additionally, a coupled groundwater and electrical model is used to analyze multiple SP data sets to evaluate seasonal changes in groundwater flow through an alpine meadow.

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.

Detecting influential observations in nonlinear regression modeling of groundwater flow

USGS Publications Warehouse

Yager, Richard 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.

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

USGS Publications Warehouse

Shoemaker, W. Barclay; Cunningham, Kevin J.; Kuniansky, Eve L.; Dixon, Joann F.

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.

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

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

Impacts of preferential flow on coastal groundwater-surface water interactions: The heterogeneous volcanic aquifer of Hawaii

NASA Astrophysics Data System (ADS)

Geng, X.; Kreyns, P.; Koneshloo, M.; Michael, H. A.

2017-12-01

Groundwater flow and salt transport processes are important for protection of coastal water resources and ecosystems. Geological heterogeneity has been recognized as a key factor affecting rates and patterns of groundwater flow and the evolution of subsurface salinity distributions in coastal aquifers. The hydrogeologic system of the volcanic Hawaiian Islands is characterized by lava flows that can form continuous, connected geologic structures in subsurface. Understanding the role of geological heterogeneity in aquifer salinization and water exchange between aquifers and the ocean is essential for effective assessment and management of water resources in the Hawaii islands. In this study, surface-based geostatistical techniques were adopted to generate geologically-realistic, statistically equivalent model realizations of the hydrogeologic system on the Big Island of Hawaii. The density-dependent groundwater flow and solute transport code SEAWAT was used to perform 3D simulations to investigate subsurface flow and salt transport through these random realizations. Flux across the aquifer-ocean interface, aquifer salinization, and groundwater flow pathways and associated transit times were quantified. Numerical simulations of groundwater pumping at various positions in the aquifers were also conducted, and associated impacts on saltwater intrusion rates were evaluated. Results indicate the impacts of continuous geologic features on large-scale groundwater processes in coastal aquifers.

Estimating Hyrdologic Properties of Groundwater Wells Using Tracer Pulse Dynamic Flow Profiling

NASA Astrophysics Data System (ADS)

Miles, K. A.; Heller, N.

2016-12-01

Traditional groundwater well design places the pump intake above the top of the well screen. It is common in this case to design the well screen for uniform entrance velocity along the profile of the well screen, even though non-uniform flow may occur. Particularly in the case where the pump is set near the very top or bottom of the well, there are instances where the zonal testing with a test pump indicates favorable water quality at one pump depth of the groundwater production well, and the water quality results yielded from the well at another depth are not compliant with federal and state regulatory limits for various naturally occurring and anthropogenic compounds. Well bore flow velocity and chemistry were determined using the USGS Tracer Pulse Dynamic Flow Profiling method along the length of well screens, while varying the pump depth. The information was then used to perform a flow and chemical mass balance to characterize the distribution of flow and chemical contribution, groundwater well screen entrance velocities, and hydrologic parameters. The presented results show pump placement affecting the average chemical discharge, and entrance velocities along the length of well screens.

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

Groundwater flow and transport modeling

USGS Publications Warehouse

Konikow, Leonard 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.

Hydrogeology and Simulated Ground-Water Flow in the Salt Pond Region of Southern Rhode Island

USGS Publications Warehouse

Masterson, John P.; Sorenson, Jason R.; Stone, Janet R.; Moran, S. Bradley; Hougham, Andrea

2007-01-01

The Salt Pond region of southern Rhode Island extends from Westerly to Narragansett Bay and forms the natural boundary between the Atlantic Ocean and the shallow, highly permeable freshwater aquifer of the South Coastal Basin. Large inputs of fresh ground water coupled with the low flushing rates to the open ocean make the salt ponds particularly susceptible to eutrophication and bacterial contamination. Ground-water discharge to the salt ponds is an important though poorly quantified source of contaminants, such as dissolved nutrients. A ground-water-flow model was developed and used to delineate the watersheds to the salt ponds, including the areas that contribute ground water directly to the ponds and the areas that contribute ground water to streams that flow into ponds. The model also was used to calculate ground-water fluxes to these coastal areas for long-term average conditions. As part of the modeling analysis, adjustments were made to model input parameters to assess potential uncertainties in model-calculated watershed delineations and in ground-water discharge to the salt ponds. The results of the simulations indicate that flow to the salt ponds is affected primarily by the ease with which water is transmitted through a glacial moraine deposit near the regional ground-water divide, and by the specified recharge rate used in the model simulations. The distribution of the total freshwater flow between direct ground-water discharge and ground-water-derived surface-water (streamflow) discharge to the salt ponds is affected primarily by simulated stream characteristics, including the streambed-aquifer connection and the stream stage. The simulated position of the ground-water divide and, therefore, the model-calculated watershed delineations for the salt ponds, were affected only by changes in the transmissivity of the glacial moraine. Selected changes in other simulated hydraulic parameters had substantial effects on total freshwater discharge and the

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

USGS Publications Warehouse

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

2003-01-01

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

The `Henry Problem' of `density-driven' groundwater flow versus Tothian `groundwater flow systems' with variable density: A review of the influential Biscayne aquifer data.

NASA Astrophysics Data System (ADS)

Weyer, K. U.

2017-12-01

Coastal groundwater flow investigations at the Biscayne Bay, south of Miami, Florida, gave rise to the concept of density-driven flow of seawater into coastal aquifers creating a saltwater wedge. Within that wedge, convection-driven return flow of seawater and a dispersion zone were assumed by Cooper et al. (1964) to be the cause of the Biscayne aquifer `sea water wedge'. This conclusion was based on the chloride distribution within the aquifer and on an analytical model concept assuming convection flow within a confined aquifer without taking non-chemical field data into consideration. This concept was later labelled the `Henry Problem', which any numerical variable density flow program must be able to simulate to be considered acceptable. Both, `density-driven flow' and Tothian `groundwater flow systems' (with or without variable density conditions) are driven by gravitation. The difference between the two are the boundary conditions. 'Density-driven flow' occurs under hydrostatic boundary conditions while Tothian `groundwater flow systems' occur under hydrodynamic boundary conditions. Revisiting the Cooper et al. (1964) publication with its record of piezometric field data (heads) showed that the so-called sea water wedge has been caused by discharging deep saline groundwater driven by gravitational flow and not by denser sea water. Density driven flow of seawater into the aquifer was not found reflected in the head measurements for low and high tide conditions which had been taken contemporaneously with the chloride measurements. These head measurements had not been included in the flow interpretation. The very same head measurements indicated a clear dividing line between shallow local fresh groundwater flow and saline deep groundwater flow without the existence of a dispersion zone or a convection cell. The Biscayne situation emphasizes the need for any chemical interpretation of flow pattern to be supported by head data as energy indicators of flow fields

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

USGS Publications Warehouse

Heywood, Charles E.; Pope, Jason P.

2009-01-01

The groundwater model documented in this report simulates the transient evolution of water levels in the aquifers and confining units of the Virginia Coastal Plain and adjacent portions of Maryland and North Carolina since 1890. Groundwater withdrawals have lowered water levels in Virginia Coastal Plain aquifers and have resulted in drawdown in the Potomac aquifer exceeding 200 feet in some areas. The discovery of the Chesapeake Bay impact crater and a revised conceptualization of the Potomac aquifer are two major changes to the hydrogeologic framework that have been incorporated into the groundwater model. The spatial scale of the model was selected on the basis of the primary function of the model of assessing the regional water-level responses of the confined aquifers beneath the Coastal Plain. The local horizontal groundwater flow through the surficial aquifer is not intended to be accurately simulated. Representation of recharge, evapotranspiration, and interaction with surface-water features, such as major rivers, lakes, the Chesapeake Bay, and the Atlantic Ocean, enable simulation of shallow flow-system details that influence locations of recharge to and discharge from the deeper confined flow system. The increased density of groundwater associated with the transition from fresh to salty groundwater near the Atlantic Ocean affects regional groundwater flow and was simulated with the Variable Density Flow Process of SEAWAT (a U.S. Geological Survey program for simulation of three-dimensional variable-density groundwater flow and transport). The groundwater density distribution was generated by a separate 108,000-year simulation of Pleistocene freshwater flushing around the Chesapeake Bay impact crater during transient sea-level changes. Specified-flux boundaries simulate increasing groundwater underflow out of the model domain into Maryland and minor underflow from the Piedmont Province into the model domain. Reported withdrawals accounted for approximately

Patterns and age distribution of ground-water flow to streams

USGS Publications Warehouse

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

1997-01-01

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

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, ...

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.

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

Groundwater Recharge and Flow Regime revealed by multi-tracers approach in a headwater, North China Plain

NASA Astrophysics Data System (ADS)

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

2014-05-01

Groundwater recharge is a crucial hydrological process for effective water management especially in arid/ semi-arid regions. However, the insufficient number of specific research regarding groundwater recharge process has been reported previously. Intensive field surveys were conducted during rainy season, mid dry season, and end of dry season, in order to clarify comprehensive groundwater recharge and flow regime of Wangkuai watershed in a headwater, which is a main recharge zone of North China Plain. The groundwater, spring, stream water and lake water were sampled, and inorganic solute constituents and stable isotopes of oxygen 18 and deuterium were determined on all water samples. Also the stream flow rate was observed. The solute ion concentrations and stable isotopic compositions show that the most water of this region can be characterized by Ca-HCO3 type and the main water source is precipitation which is affected by altitude effect of stable isotopes. In addition, the river and reservoir of the area seem to recharge the groundwater during rainy season, whereas interaction between surface water and groundwater does not become dominant gradually after the rainy season. The inversion analysis applied in Wangkuai watershed using simple mixing model represents an existing multi-flow systems which shows a distinctive tracer signal and flow rate. In summary, the groundwater recharged at different locations in the upper stream of Wangkuai reservoir flows downward to alluvial fan with a certain amount of mixing together, also the surface water recharges certainly the groundwater in alluvial plain in the rainy season.

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

Vertical groundwater flow in Permo-Triassic sediments underlying two cities in the Trent River Basin (UK)

NASA Astrophysics Data System (ADS)

Taylor, R. G.; Cronin, A. A.; Trowsdale, S. A.; Baines, O. P.; Barrett, M. H.; Lerner, D. N.

2003-12-01

The vertical component of groundwater flow that is responsible for advective penetration of contaminants in sandstone aquifers is poorly understood. This lack of knowledge is of particular concern in urban areas where abstraction disrupts natural groundwater flow regimes and there exists an increased density of contaminant sources. Vertical hydraulic gradients that control vertical groundwater flow were investigated using bundled multilevel piezometers and a double-packer assembly in dedicated boreholes constructed to depths of between 50 and 92 m below ground level in Permo-Triassic sediments underlying two cities within the Trent River Basin of central England (Birmingham, Nottingham). The hydrostratigraphy of the Permo-Triassic sediments, indicated by geophysical logging and hydraulic (packer) testing, demonstrates considerable control over observed vertical hydraulic gradients and, hence, vertical groundwater flow. The direction and magnitude of vertical hydraulic gradients recorded in multilevel piezometers and packers are broadly complementary and range, within error, from +0.1 to -0.7. Groundwater is generally found to flow vertically toward transmissive zones within the hydrostratigraphical profile though urban abstraction from the Sherwood Sandstone aquifer also influences observed vertical hydraulic gradients. Bulk, downward Darcy velocities at two locations affected by abstraction are estimated to be in the order of several metres per year. Consistency in the distribution of hydraulic head with depth in Permo-Triassic sediments is observed over a one-year period and adds support the deduction of hydrostratigraphic control over vertical groundwater flow.

Groundwater flow in a coastal peatland and its influence on submarine groundwater discharge

NASA Astrophysics Data System (ADS)

Ptak, T.; Ibenthal, M.; Janssen, M.; Massmann, G.; Lenartz, B.

2017-12-01

Coastal peatlands are characterized by intense interactions between land and sea, comprising both a submarine discharge of fresh groundwater and inundations of the peatland with seawater. Nutrients and salts can influence the biogeochemical processes both in the shallow marine sediments and in the peatland. The determination of flow direction and quantity of groundwater flow are therefore elementary. Submarine groundwater discharge (SGD) has been reported from several locations in the Baltic. The objective of this study is to quantify the exchange of fresh and brackish water across the shoreline in a coastal peatland in Northeastern Germany, and to assess the influence of a peat layer extending into the Baltic Sea. Below the peatland, a shallow fine sand aquifer differs in depth and is limited downwards by glacial till. Water level and electrical conductivity (EC) are permanently measured in different depths at eight locations in the peatland. First results indicate a general groundwater flow direction towards the sea. Electrical conductivity measurements suggest different permeabilities within the peat layer, depending on its thickness and degradation. Near the beach, EC fluctuates partially during storm events due to seawater intrusion and reverse discharge afterwards. The groundwater flow will be verified with a 3D model considering varying thicknesses of the aquifer. Permanent water level and electrical conductivity readings, meteorological data and hydraulic conductivity from slug tests and grain size analysis are the base for the calibration of the numerical model.

Effective contaminant detection networks in uncertain groundwater flow fields.

PubMed

Hudak, P F

2001-01-01

A mass transport simulation model tested seven contaminant detection-monitoring networks under a 40 degrees range of groundwater flow directions. Each monitoring network contained five wells located 40 m from a rectangular landfill. The 40-m distance (lag) was measured in different directions, depending upon the strategy used to design a particular monitoring network. Lagging the wells parallel to the central flow path was more effective than alternative design strategies. Other strategies allowed higher percentages of leaks to migrate between monitoring wells. Results of this study suggest that centrally lagged groundwater monitoring networks perform most effectively in uncertain groundwater-flow fields.

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

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.

Climate reconstruction from borehole temperatures influenced by groundwater flow

NASA Astrophysics Data System (ADS)

Kurylyk, B.; Irvine, D. J.; Tang, W.; Carey, S. K.; Ferguson, G. A. G.; Beltrami, H.; Bense, V.; McKenzie, J. M.; Taniguchi, M.

2017-12-01

Borehole climatology offers advantages over other climate reconstruction methods because further calibration steps are not required and heat is a ubiquitous subsurface property that can be measured from terrestrial boreholes. The basic theory underlying borehole climatology is that past surface air temperature signals are reflected in the ground surface temperature history and archived in subsurface temperature-depth profiles. High frequency surface temperature signals are attenuated in the shallow subsurface, whereas low frequency signals can be propagated to great depths. A limitation of analytical techniques to reconstruct climate signals from temperature profiles is that they generally require that heat flow be limited to conduction. Advection due to groundwater flow can thermally `contaminate' boreholes and result in temperature profiles being rejected for regional climate reconstructions. Although groundwater flow and climate change can result in contrasting or superimposed thermal disturbances, groundwater flow will not typically remove climate change signals in a subsurface thermal profile. Thus, climate reconstruction is still possible in the presence of groundwater flow if heat advection is accommodated in the conceptual and mathematical models. In this study, we derive a new analytical solution for reconstructing surface temperature history from borehole thermal profiles influenced by vertical groundwater flow. The boundary condition for the solution is composed of any number of sequential `ramps', i.e. periods with linear warming or cooling rates, during the instrumented and pre-observational periods. The boundary condition generation and analytical temperature modeling is conducted in a simple computer program. The method is applied to reconstruct climate in Winnipeg, Canada and Tokyo, Japan using temperature profiles recorded in hydrogeologically active environments. The results demonstrate that thermal disturbances due to groundwater flow and climate

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

NASA Astrophysics Data System (ADS)

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

2003-04-01

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

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

Groundwater flow and hydrogeochemical evolution in the Jianghan Plain, central China

NASA Astrophysics Data System (ADS)

Gan, Yiqun; Zhao, Ke; Deng, Yamin; Liang, Xing; Ma, Teng; Wang, Yanxin

2018-05-01

Hydrogeochemical analysis and multivariate statistics were applied to identify flow patterns and major processes controlling the hydrogeochemistry of groundwater in the Jianghan Plain, which is located in central Yangtze River Basin (central China) and characterized by intensive surface-water/groundwater interaction. Although HCO3-Ca-(Mg) type water predominated in the study area, the 457 (21 surface water and 436 groundwater) samples were effectively classified into five clusters by hierarchical cluster analysis. The hydrochemical variations among these clusters were governed by three factors from factor analysis. Major components (e.g., Ca, Mg and HCO3) in surface water and groundwater originated from carbonate and silicate weathering (factor 1). Redox conditions (factor 2) influenced the geogenic Fe and As contamination in shallow confined groundwater. Anthropogenic activities (factor 3) primarily caused high levels of Cl and SO4 in surface water and phreatic groundwater. Furthermore, the factor score 1 of samples in the shallow confined aquifer gradually increased along the flow paths. This study demonstrates that enhanced information on hydrochemistry in complex groundwater flow systems, by multivariate statistical methods, improves the understanding of groundwater flow and hydrogeochemical evolution due to natural and anthropogenic impacts.

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. © 2014, National Ground Water Association.

The limited and localized flow of fresh groundwater to the world's oceans

NASA Astrophysics Data System (ADS)

Luijendijk, E.; Gleeson, T. P.; Moosdorf, N.

2017-12-01

Submarine groundwater discharge, the flow of fresh or saline groundwater to oceans [Burnett et al., 2003], may be a significant contributor to the water and chemical budgets of the world's oceans [Taniguchi et al., 2002] potentially buffering ocean acidification with groundwater alkalinity and is arguably the most uncertain component of the global groundwater budget [Alley et al., 2002]. The fresh component of submarine groundwater discharge is critical due to its high solute and nutrient load, and has been quantified locally and but only roughly estimated globally using significant assumptions. Here we show that that fresh submarine groundwater discharge is an insignificant water contributor to global oceans (0.05% of the total input) but that the freshwater discharge may still be an important chemical and nutrient contributor especially around distinct hotspots. The first spatially-explicit, physically-based global estimate of fresh submarine groundwater discharge was derived by combining density-dependent numerical groundwater models and a geospatial analysis of global coastal watersheds to robustly simulate the partitioning of onshore and offshore groundwater discharge. Although fresh submarine groundwater discharge is an insignificant part of fresh coastal groundwater discharge, results are consistent with previous estimates of significant recirculated seawater discharging as groundwater as well as quantifying the significant near-shore terrestrial discharge, a flux that has so far been overlooked in global hydrological studies and that affects coastal water budgets, evapotranspiration and ecosystems.

The use of natural isotopes for identifying the origins of groundwater flows: Drentsche Aa Brook Valley, The Netherlands.

NASA Astrophysics Data System (ADS)

Elshehawi, Samer; Grootjans, Ab; Bregman, Enno

2017-04-01

This paper investigates the origin of various groundwater flows in a small brook valley reserve Drentsche Aa Valley in the northern part of the Netherlands. The aim was also to validate a hydrological model that simulated coupled particle flow in this area and also incorporated different scenarios for groundwater abstraction in order to predict future implications of groundwater abstraction on ecological values. Water samples from various sites and depths were analysed for macro-ionic composition, stable isotopes (2H and 18O) and also 14C. Three sites have 14C activities over 100%, indicating very recent water. The main groundwater discharge areas showed inflow of old groundwater up to 5000 years. Inflow of different groundwater flows of various ages could be detected most clearly from the 14C data. Downstream area that were affected by groundwater abstraction showed distinct infiltration characteristics, both in macro-ionic composition and contents of natural isotopes, to a depth of 6m below surface In the main exfiltration areas, we found that at 95 meters below the surface, the groundwater was characterized by a NaCl type groundwater facies. But the absolute concentrations were not high enough to conclude that double diffusive convection (DDC) near a salt diapir was responsible for this effect.

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

Hydrogeology and Simulation of Groundwater Flow in the Plymouth-Carver-Kingston-Duxbury Aquifer System, Southeastern Massachusetts

USGS Publications Warehouse

Masterson, John P.; Carlson, Carl S.; Walter, Donald A.; Other contributing authors: Bent, Gardner C.; Massey, Andrew J.

2009-01-01

The glacial sediments that underlie the Plymouth-Carver-Kingston-Duxbury area of southeastern Massachusetts compose an important aquifer system that is the primary source of water for a region undergoing rapid development. Population increases and land-use changes in this area has led to two primary environmental effects that relate directly to groundwater resources: (1) increases in pumping that can adversely affect environmentally sensitive groundwater-fed surface waters, such as ponds, streams, and wetlands; and (2) adverse effects of land use on the quality of water in the aquifer. In response to these concerns, the U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, began an investigation in 2005 to improve the understanding of the hydrogeology in the area and to assess the effects of changing pumping and recharge conditions on groundwater flow in the Plymouth-Carver-Kingston-Duxbury aquifer system. A numerical flow model was developed based on the USGS computer program MODFLOW-2000 to assist in the analysis of groundwater flow. Model simulations were used to determine water budgets, flow directions, and the sources of water to pumping wells, ponds, streams, and coastal areas. Model-calculated water budgets indicate that approximately 298 million gallons per day (Mgal/d) of water recharges the Plymouth-Carver-Kingston-Duxbury aquifer system. Most of this water (about 70 percent) moves through the aquifer, discharges to streams, and then reaches the coast as surface-water discharge. Of the remaining 30 percent of flow, about 25 percent of the water that enters the aquifer as recharge discharges directly to coastal areas and 5 percent discharges to pumping wells. Groundwater withdrawals are anticipated to increase from the current (2005) rate of about 14 Mgal/d to about 21 Mgal/d by 2030. Pumping from large-capacity production wells decreases water levels and increases the potential for effects on surface

Estimates of consumptive use and ground-water return flow using water budgets in Palo Verde Valley, California

USGS Publications Warehouse

Owen-Joyce, Sandra J.; Kimsey, Steven L.

1987-01-01

Palo Verde Valley, California, is an agricultural area in the flood plain of the Colorado River where irrigation water is diverted from the river and groundwater is discharged to a network of drainage ditches and (or) the river. Consumptive use by vegetation and groundwater return flow were calculated using water budgets. Consumptive use by vegetation was 484,000 acre-ft in 1981, 453,600 acre-ft in 1982, 364,400 acre-ft in 1983, and 374,300 acre-ft in 1984. The consumptive-use estimates are most sensitive to two measured components of the water budget, the diversion at Palo Verde Dam and the discharge from drainage ditches to the river. Groundwater return flow was 31,700 acre-ft in 1981, 24,000 acre-ft in 1982, 2,500 acre-ft in 1983, and 7 ,900 acre-ft in 1984. The return-flow estimates are most sensitive to discharge from drainage ditches; various irrigation requirements and crop areas, particularly alfalfa; the diversion at Palo Verde Dam; and the estimate of consumptive use. During increasing flows in the river, the estimate of groundwater return flow is sensitive also to change in groundwater storage. Change in groundwater storage was estimated to be -5,700 acre-ft in 1981, -12,600 acre-ft in 1982, 5,200 acre-ft in 1983, and 11 ,600 acre-ft in 1984. Changes in storage can be a significant component in the water budget used to estimate groundwater return flow but is negligible in the water budget used to estimate consumptive use. Change in storage was 1 to 3% of annual consumptive use. Change in storage for the area drained by the river ranged from 7 to 96% of annual groundwater return flow during the 4 years studied. Consumptive use calculated as diversions minus return flows was consistently lower than consumptive use calculated in a water budget. Water-budget estimates of consumptive use account for variations in precipitation, tributary inflow, river stage, and groundwater storage. The calculations for diversions minus return flows do not account for these

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.

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

NASA Astrophysics Data System (ADS)

Genereux, David P.; Jordan, Michael

2006-04-01

This paper reviews work related to interbasin groundwater flow (naturally occurring groundwater flow beneath watershed topographic divides) into lowland rainforest watersheds at La Selva Biological Station in Costa Rica. Chemical mixing calculations (based on dissolved chloride) have shown that up to half the water in some streams and up to 84% of the water in some riparian seeps and wells is due to high-solute interbasin groundwater flow (IGF). The contribution is even greater for major ions; IGF accounts for well over 90% of the major ions at these sites. Proportions are highly variable both among watersheds and with elevation within the same watershed (there is greater influence of IGF at lower elevations). The large proportion of IGF found in water in some riparian wetlands suggests that IGF is largely responsible for maintaining these wetlands. δ 18O data support the conclusions from the major ion data. Annual water and major ion budgets for two adjacent watersheds, one affected by IGF and the other not, showed that IGF accounted for two-thirds of the water input and 92-99% of the major ion input (depending on the major ion in question) to the former watershed. The large (in some cases, dominating) influence of IGF on watershed surface water quantity and quality has important implications for stream ecology and watershed management in this lowland rainforest. Because of its high phosphorus content, IGF increases a variety of ecological variables (algal growth rates, leaf decay rate, fungal biomass, invertebrate biomass, microbial respiration rates on leaves) in streams at La Selva. The significant rates of IGF at La Selva also suggest the importance of regional (as opposed to small-scale local) water resource planning that links lowland watersheds with regional groundwater. IGF is a relatively unexplored and potentially critical factor in the conservation of lowland rainforest.

The Importance of Capturing Topographic Features for Modeling Groundwater Flow and Transport in Mountainous Watersheds

NASA Astrophysics Data System (ADS)

Wang, C.; Gomez-Velez, J. D.; Wilson, J. L.

2017-12-01

Groundwater plays a key role in runoff generation and stream water chemistry from reach to watershed scales. The spatial distribution of ridges and streams can influence the spatial patterns of groundwater recharge and drainage, specially in mountainous terrains where these features are more prominent. However, typical modeling efforts simplify or ignore some of these features due to computational limitations without a systematic investigation of the implications for flow and transport within the watershed. In this study, we investigate the effect of capturing key topographic features on modeled groundwater flow and transport characteristics in a mountainous watershed. We build model scenarios of different topographic complexity levels (TCLs) to capture different levels of representation of streams and ridges in the model. Modeled baseflow and groundwater mean residence time (MRT) are used to quantify the differences among TCLs. Our results show that capturing the streams and ridges has a significant influence on simulated groundwater flow and transport patterns. Topographic complexity controls the proportion of baseflow generated from local, intermediate, and regional flow paths, thus influencing the amount and MRT of basefow flowing into streams of different Horton-Strahler orders. We further simulate the concentration of solute exported into streams from subsurface chemical weathering. The concentration of chemical weathering products in streams is less sensitive to model TCL due to the thermodynamic constraint on the equilibrium concentration of the chemical weathering. We also tested the influence of geology on the effect of TCL. The effect of TCL is consistent under different geological conditions; however, it is enhanced in models with low hydraulic conductivity because more of the flow is forced into shallow and local flow paths. All of these changes can affect our ability to interpret environmental tracer data and predict bio- and geo-chemical evolution of

The influence of heterogeneity on coastal groundwater flow - physical and numerical modeling of fringing reefs, dykes and structured conductivity fields

NASA Astrophysics Data System (ADS)

Houben, Georg J.; Stoeckl, Leonard; Mariner, Katrina E.; Choudhury, Anis S.

2018-03-01

Geological heterogeneity of the subsurface, caused by both discrete features and spatially distributed hydraulic conductivity fields, affects the flow of coastal groundwater. It influences the shape and the position of the interface between saltwater and freshwater, as well as the location and flux rate of freshwater discharge to the ocean. Fringing reefs lead to a bimodal regime of freshwater discharge, with discharge at the beach face and through deeper, submarine springs. Impermeable vertical flow barriers (dykes) lead to an impoundment of fresh groundwater and a compartmentalization of the aquifer but also to a delayed expulsion of saline water. Spatially distributed conductivity fields affect the shape of the interface and the geometry of the saltwater wedge. Higher effective conductivities lead to a further landward intrusion of the wedge toe. These flow characteristics can be important for groundwater extraction, the delineation of protection zones and the assessment of contaminant transport to coastal ecosystems.

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.

Groundwater response to the 2014 pulse flow in the Colorado River Delta

USGS Publications Warehouse

Kennedy, Jeffrey; Rodriguez-Burgueno, Eliana; Ramirez-Hernandez, Jorge

2017-01-01

During the March-May 2014 Colorado River Delta pulse flow, approximately 102 × 106 m3 (82,000 acre-feet) of water was released into the channel at Morelos Dam, with additional releases further downstream. The majority of pulse flow water infiltrated and recharged the regional aquifer. Using groundwater-level and microgravity data we mapped the spatial and temporal distribution of changes in aquifer storage associated with pulse flow. Surface-water losses to infiltration were greatest around the Southerly International Boundary, where a lowered groundwater level owing to nearby pumping created increased storage potential as compared to other areas with shallower groundwater. Groundwater levels were elevated for several months after the pulse flow but had largely returned to pre-pulse levels by fall 2014. Elevated groundwater levels in the limitrophe (border) reach extended about 2 km to the east around the midway point between the Northerly and Southerly International Boundaries, and about 4 km to the east at the southern end. In the southern part of the delta, although total streamflow in the channel was less due to upstream infiltration, augmented deliveries through irrigation canals and possible irrigation return flows created sustained increases in groundwater levels during summer 2014. Results show that elevated groundwater levels and increases in groundwater storage were relatively short lived (confined to calendar year 2014), and that depressed water levels associated with groundwater pumping around San Luis, Arizona and San Luis Rio Colorado, Sonora cause large, unavoidable infiltration losses of in-channel water to groundwater in the vicinity.

Megacity pumping and preferential flow threaten groundwater quality

PubMed Central

Khan, Mahfuzur R.; Koneshloo, Mohammad; Knappett, Peter S. K.; Ahmed, Kazi M.; Bostick, Benjamin C.; Mailloux, Brian J.; Mozumder, Rajib H.; Zahid, Anwar; Harvey, Charles F.; van Geen, Alexander; Michael, Holly A.

2016-01-01

Many of the world's megacities depend on groundwater from geologically complex aquifers that are over-exploited and threatened by contamination. Here, using the example of Dhaka, Bangladesh, we illustrate how interactions between aquifer heterogeneity and groundwater exploitation jeopardize groundwater resources regionally. Groundwater pumping in Dhaka has caused large-scale drawdown that extends into outlying areas where arsenic-contaminated shallow groundwater is pervasive and has potential to migrate downward. We evaluate the vulnerability of deep, low-arsenic groundwater with groundwater models that incorporate geostatistical simulations of aquifer heterogeneity. Simulations show that preferential flow through stratigraphy typical of fluvio-deltaic aquifers could contaminate deep (>150 m) groundwater within a decade, nearly a century faster than predicted through homogeneous models calibrated to the same data. The most critical fast flowpaths cannot be predicted by simplified models or identified by standard measurements. Such complex vulnerability beyond city limits could become a limiting factor for megacity groundwater supplies in aquifers worldwide. PMID:27673729

Numerical Study of Heat Transfer during Artificial Ground Freezing Combined with Groundwater Flow based on in-situ Measurement

NASA Astrophysics Data System (ADS)

Hu, R.; Liu, Q.

2016-12-01

For civil engineering projects, especially in the subsurface with groundwater, the artificial ground freezing (AGF) method has been widely used. Commonly, a refrigerant is circulated through a pre-buried pipe network to form a freezing wall to support the construction. In many cases, the temperature change is merely considered as a result of simple heat conduction. However, the influence of the water-ice phase change on the flow properties should not be neglected, if large amount of groundwater with high flow velocities is present. In this work, we perform a 2D modelling (software: Comsol Multiphysics) of an AFG project of a metro tunnel in Southern China, taking groundwater flow into account. The model is validated based on in-situ measurement of groundwater flow and temperature. We choose a cross section of this horizontal AGF project and set up a model with horizontal groundwater flow normal to the axial of the tunnel. The Darcy velocity is a coupling variable and related to the temperature field. During the phase change of the pore water and the decrement of permeability in freezing zone, we introduce a variable of effective hydraulic conductivity which is described by a function of temperature change. The energy conservation problem is solved by apparent heat capacity method and the related parameter change is described by a step function (McKenzie, et. al. 2007). The results of temperature contour maps combined with groundwater flow velocity at different times indicate that the freezing wall appears in an asymmetrical shape along the groundwater flow direction. It forms slowly and on the upstream side the thickness of the freezing wall is thinner than that on the downstream side. The closure time of the freezing wall increases at the middle of the both up and downstream sides. The average thickness of the freezing wall on the upstream side is mostly affected by the groundwater flow velocity. With the successful validation of this model, this numerical

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

USGS Publications Warehouse

Kikuchi, Colin P.

2013-01-01

The Matanuska-Susitna Valley is in the Upper Cook Inlet Basin and is currently undergoing rapid population growth outside of municipal water and sewer service areas. In response to concerns about the effects of increasing water use on future groundwater availability, a study was initiated between the Alaska Department of Natural Resources and the U.S. Geological Survey. The goals of the study were (1) to compile existing data and collect new data to support hydrogeologic conceptualization of the study area, and (2) to develop a groundwater flow model to simulate flow dynamics important at the regional scale. The purpose of the groundwater flow model is to provide a scientific framework for analysis of regional-scale groundwater availability. To address the first study goal, subsurface lithologic data were compiled into a database and were used to construct a regional hydrogeologic framework model describing the extent and thickness of hydrogeologic units in the Matanuska-Susitna Valley. The hydrogeologic framework model synthesizes existing maps of surficial geology and conceptual geochronologies developed in the study area with the distribution of lithologies encountered in hundreds of boreholes. The geologic modeling package Geological Surveying and Investigation in Three Dimensions (GSI3D) was used to construct the hydrogeologic framework model. In addition to characterizing the hydrogeologic framework, major groundwater-budget components were quantified using several different techniques. A land-surface model known as the Deep Percolation Model was used to estimate in-place groundwater recharge across the study area. This model incorporates data on topography, soils, vegetation, and climate. Model-simulated surface runoff was consistent with observed streamflow at U.S. Geological Survey streamgages. Groundwater withdrawals were estimated on the basis of records from major water suppliers during 2004-2010. Fluxes between groundwater and surface water were

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.

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.

A high-resolution land model coupled with groundwater lateral flow, human water regulation and the changes in soil freeze-thaw fronts

NASA Astrophysics Data System (ADS)

Xie, Z.; Zeng, Y.; Liu, S.; Gao, J.; Jia, B.; Qin, P.

2017-12-01

Both anthropogenic water regulation and groundwater lateral flow essentially affect groundwater table patterns. Their relationship is close because lateral flow recharges the groundwater depletion cone, which is induced by over-exploitation. And the movement of frost and thaw fronts (FTFs) affects soil water and thermal characteristics, as well as energy and water exchanges between land surface and the atmosphere. In this study, schemes describing groundwater lateral flow, human water regulation and the changes in soil freeze-thaw fronts were developed and incorporated into the Community Land Model 4.5. Then the model was applied in Heihe River Basin(HRB), an arid and semiarid region, northwest China. High resolution ( 1 km) numerical simulations showed that groundwater lateral flow driven by changes in water heads can essentially change the groundwater table pattern with the deeper water table appearing in the hillslope regions and shallower water table appearing in valley bottom regions and plains. Over the last decade, anthropogenic groundwater exploitation deepened the water table by approximately 2 m in the middle reaches of the HRB and rapidly reduced the terrestrial water storage, while irrigation increased soil moisture by approximately 0.1 m3 m-3. The water stored in the mainstream of the Heihe River was also reduced by human surface water withdrawal. The latent heat flux was increased by 30 W m-2 over the irrigated region, with an identical decrease in sensible heat flux. The simulated groundwater lateral flow was shown to effectively recharge the groundwater depletion cone caused by over-exploitation. The offset rate is higher in plains than mountainous regions. In addition, the simulated FTFs depth compared well with the observed data both in D66 station (permafrost) and Hulugou station (seasonally frozen ground). Over the HRB, the upstream area is permafrost region with maximum thawed depth at 2.5 m and lower region is seasonal frozen ground region

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

USGS Publications Warehouse

Iverson, Richard M.; Reid, Mark E.

1992-01-01

Hilly or mountainous topography influences gravity-driven groundwater flow and the consequent distribution of effective stress in shallow subsurface environments. Effective stress, in turn, influences the potential for slope failure. To evaluate these influences, we formulate a two-dimensional, steady state, poroelastic model. The governing equations incorporate groundwater effects as body forces, and they demonstrate that spatially uniform pore pressure changes do not influence effective stresses. We implement the model using two finite element codes. As an illustrative case, we calculate the groundwater flow field, total body force field, and effective stress field in a straight, homogeneous hillslope. The total body force and effective stress fields show that groundwater flow can influence shear stresses as well as effective normal stresses. In most parts of the hillslope, groundwater flow significantly increases the Coulomb failure potential Φ, which we define as the ratio of maximum shear stress to mean effective normal stress. Groundwater flow also shifts the locus of greatest failure potential toward the slope toe. However, the effects of groundwater flow on failure potential are less pronounced than might be anticipated on the basis of a simpler, one-dimensional, limit equilibrium analysis. This is a consequence of continuity, compatibility, and boundary constraints on the two-dimensional flow and stress fields, and it points to important differences between our elastic continuum model and limit equilibrium models commonly used to assess slope stability.

Antarctic subglacial groundwater: measurement concept and potential influence on ice flow

NASA Astrophysics Data System (ADS)

Kulessa, Bernd; Siegert, Martin; Bougamont, Marion; Christoffersen, Poul; Key, Kerry; Andersen, Kristoffer; Booth, Adam; Smith, Andrew

2017-04-01

Is groundwater abundant in Antarctica and does it modulate ice flow? Answering this question matters because ice streams flow by gliding over a wet substrate of till. Water fed to ice-stream beds thus influences ice-sheet dynamics and, potentially, sea-level rise. It is recognised that both till and the sedimentary basins from which it originates are porous and could host a reservoir of mobile groundwater that interacts with the subglacial interfacial system. According to recent numerical modelling up to half of all water available for basal lubrication, and time lags between hydrological forcing and ice-sheet response as long as millennia, may have been overlooked in models of ice flow. Here, we review evidence in support of Antarctic groundwater and propose how it can be measured to ascertain the extent to which it modulates ice flow. We present new seismoelectric soundings of subglacial till, and new magnetotelluric and transient electromagnetic forward models of subglacial groundwater reservoirs. We demonstrate that multi-facetted and integrated geophysical datasets can detect, delineate and quantify the groundwater contents of subglacial sedimentary basins and, potentially, monitor groundwater exchange rates between subglacial till layers. We thus describe a new area of glaciological investigation and how it should progress in future.

Stability analysis of rockmass using a hydrogeologic model of groundwater flow at an underground limestone mine in Korea

NASA Astrophysics Data System (ADS)

Baek, H.; Kim, D.; Kim, G.; Kim, D.; Cheong, S.

2017-12-01

The safety and environmental issues should be addressed for sustainable mining operations. One of the key factors is the groundwater flow into underground mine workings, which will affect the overall workability and efficiency of the mining operation. Prediction of the groundwater inflow requires a detailed knowledge of the geologic conditions, including the presence of major faults and other geologic structures at the mine site. The hydrologic boundaries and depth of the phreatic surface of the mine area, as well as other relevant properties of the rockmass, are also provided. The stability of underground structures, in terms of the maximum stresses and deformations within the rockmass, can be analyzed using either the total stress or the effective stress approaches. Both the dried and saturated conditions should be considered with appropriate safety factors, as the distribution of the water pressure within the rockmass resulted from the groundwater flow directly affects the stability. In some cases, the rockmass rating systems such as the RMR and Q-systems are also applied. Various numerical codes have been used to construct the hydrogeologic models of mine sites, and the MINEDW by Itasca is one of those groundwater flow model codes developed to simulate groundwater flow related to mining. In this study, with a 3D hydrogeologic model constructed using the MINEDW for an underground limestone mine, the rate of mine water inflow and the porewater pressure were estimated. The stability of mine pillars and adits was analyzed adopting the porewater pressure and effective stress developed in the rockmass. The results were also compared with those from other 2D stability analysis procedures.

Detect groundwater flowing from riverbed using a drone

NASA Astrophysics Data System (ADS)

Kato, Kenji; Takemon, Yasuhiro

2017-04-01

Estimate the direct flow of groundwater to river is an important step in understanding of hydrodynamics in river system. Function of groundwater in river system does not limit to the mass of water. Continuous supply with thermally stable water from riverbed produces a space with unique condition, which provides various functions for organisms inhabiting in river as a shelter avoiding large shift of temperature, or to maintain productivity for small scale ecosystem by supplying nutrient rich groundwater if it gushes out from the riverbed in a deep pool of river. This may contribute to biodiversity of river system. Such function of groundwater is more significant for rivers run in island and in mountain zone. To evaluate the function of groundwater flowing from riverbed we first try to find such site by using a drone equipped with a sensitive thermo-camera to detect water surface temperature. In the examined area temperature of the groundwater doesn't change much throughout a year at around 15 to 16 °C, while surface temperature of the examined river fluctuates from below 10 °C to over 25 °C throughout seasons. By using this difference in temperature between groundwater and river water we tried to find site where groundwater comes out from the riverbed. Obviously winter when surface temperature becomes below 10 °C is an appropriate season to find groundwater as it comes up to the surface of river with depth ranging from 1 to 3 m. Trial flight surveys of drone were conducted in Kano-river in Izu Peninsula located at southern foot of Mt. Fuji in central Japan. Employed drone was Inspire1 (DJI, China) equipped with a Thermal camera (Zenmuse XT ZXTA 19 FP, FLIR, USA) and operated by Kazuhide Juta (KELEK Co. Ltd., Japan) and Mitsuhiro Komiya (TAM.Co.,LTD). In contrast to the former cases with employing airplane for taking aerial photograph, drone takes photo while flying at a low-altitude. When it flies at 40m above the water surface of river, resolution is at an

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

USGS Publications Warehouse

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

2018-01-01

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

Groundwater flow model for the Little Plover River basin in Wisconsin’s Central Sands

USGS Publications Warehouse

Ken Bradbury,; Fienen, Michael N.; Kniffin, Maribeth; Jacob Krause,; Westenbroek, Stephen M.; Leaf, Andrew T.; Barlow, Paul M.

2017-01-01

The Little Plover River is a groundwater-fed stream in the sand plains region of central Wisconsin. In this region, sandy sediment deposited during or soon after the last glaciation forms an important unconfined sand and gravel aquifer. This aquifer supplies water for numerous high-capacity irrigation, municipal, and industrial wells that support a thriving agricultural industry. In recent years the addition of many new wells, combined with observed diminished flows in the Little Plover and other nearby rivers, has raised concerns about the impacts of the wells on groundwater levels and on water levels and flows in nearby lakes, streams, and wetlands. Diverse stakeholder groups, including well operators, Growers, environmentalists, local land owners, and regulatory and government officials have sought a better understanding of the local groundwater-surface water system and have a shared desire to balance the water needs of the he liagricultural, industrial, and urban users with the maintenance and protection of groundwater-dependent natural resources. To help address these issues, the Wisconsin Department of Natural Resources requested that the Wisconsin Geological and Natural History Survey and U.S. Geological Survey cooperatively develop a groundwater flow model that could be used to demonstrate the relationships among groundwater, surface water, and well withdrawals and also be a tool for testing and evaluating alternative water management strategies for the central sands region. Because of an abundance of previous studies, data availability, local interest, and existing regulatory constraints the model focuses on the Little Plover River watershed, but the modeling methodology developed during this study can apply to much of the larger central sands of Wisconsin. The Little Plover River groundwater flow model simulates three-dimensional groundwater movement in and around the Little Plover River basin under steady-state and transient conditions. This model

Hydrology and simulation of ground-water flow in the Tooele Valley ground-water basin, Tooele County, Utah

USGS Publications Warehouse

Stolp, Bernard J.; Brooks, Lynette E.

2009-01-01

Ground water is the sole source of drinking water within Tooele Valley. Transition from agriculture to residential land and water use necessitates additional understanding of water resources. The ground-water basin is conceptualized as a single interconnected hydrologic system consisting of the consolidated-rock mountains and adjoining unconsolidated basin-fill valleys. Within the basin fill, unconfined conditions exist along the valley margins and confined conditions exist in the central areas of the valleys. Transmissivity of the unconsolidated basin-fill aquifer ranges from 1,000 to 270,000 square feet per day. Within the consolidated rock of the mountains, ground-water flow largely is unconfined, though variability in geologic structure, stratigraphy, and lithology has created some areas where ground-water flow is confined. Hydraulic conductivity of the consolidated rock ranges from 0.003 to 100 feet per day. Ground water within the basin generally moves from the mountains toward the central and northern areas of Tooele Valley. Steep hydraulic gradients exist at Tooele Army Depot and near Erda. The estimated average annual ground-water recharge within the basin is 82,000 acre-feet per year. The primary source of recharge is precipitation in the mountains; other sources of recharge are irrigation water and streams. Recharge from precipitation was determined using the Basin Characterization Model. Estimated average annual ground-water discharge within the basin is 84,000 acre-feet per year. Discharge is to wells, springs, and drains, and by evapotranspiration. Water levels at wells within the basin indicate periods of increased recharge during 1983-84 and 1996-2000. During these periods annual precipitation at Tooele City exceeded the 1971-2000 annual average for consecutive years. The water with the lowest dissolved-solids concentrations exists in the mountain areas where most of the ground-water recharge occurs. The principal dissolved constituents are calcium

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

DOE PAGES

McLing, Travis L.; Smith, Richard P.; Smith, Robert W.; ...

2016-04-10

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,more » 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.« less

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.

New approach for simulating groundwater flow in discrete fracture network

NASA Astrophysics Data System (ADS)

Fang, H.; Zhu, J.

2017-12-01

In this study, we develop a new approach to calculate groundwater flowrate and hydraulic head distribution in two-dimensional discrete fracture network (DFN) where both laminar and turbulent flows co-exist in individual fractures. The cubic law is used to calculate hydraulic head distribution and flow behaviors in fractures where flow is laminar, while the Forchheimer's law is used to quantify turbulent flow behaviors. Reynolds number is used to distinguish flow characteristics in individual fractures. The combination of linear and non-linear equations is solved iteratively to determine flowrates in all fractures and hydraulic heads at all intersections. We examine potential errors in both flowrate and hydraulic head from the approach of uniform flow assumption. Applying the cubic law in all fractures regardless of actual flow conditions overestimates the flowrate when turbulent flow may exist while applying the Forchheimer's law indiscriminately underestimate the flowrate when laminar flows exist in the network. The contrast of apertures of large and small fractures in the DFN has significant impact on the potential errors of using only the cubic law or the Forchheimer's law. Both the cubic law and Forchheimer's law simulate similar hydraulic head distributions as the main difference between these two approaches lies in predicting different flowrates. Fracture irregularity does not significantly affect the potential errors from using only the cubic law or the Forchheimer's law if network configuration remains similar. Relative density of fractures does not significantly affect the relative performance of the cubic law and Forchheimer's law.

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

DOE PAGES

Sjöberg, Ylva; Coon, Ethan; K. Sannel, A. Britta; ...

2016-02-04

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

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

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.

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

DOE PAGES

Frisbee, Marty D.; Tysor, Elizabeth H.; Stewart-Maddox, Noah; ...

2016-02-13

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 streammore » channels. Springs emerge preferentially on one side of stream valleys where landscape incision has intercepted IGF flowpaths. 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.« less

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

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

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.

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.

2015-08-12

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

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. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

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.

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.

Evaluation of multiple tracer methods to estimate low groundwater flow velocities

DOE PAGES

Reimus, Paul W.; Arnold, Bill W.

2017-02-20

Here, four different tracer methods were used to estimate groundwater flow velocity at a multiple-well site in the saturated alluvium south of Yucca Mountain, Nevada: (1) two single-well tracer tests with different rest or “shut-in” periods, (2) a cross-hole tracer test with an extended flow interruption, (3) a comparison of two tracer decay curves in an injection borehole with and without pumping of a downgradient well, and (4) a natural-gradient tracer test. Such tracer methods are potentially very useful for estimating groundwater velocities when hydraulic gradients are flat (and hence uncertain) and also when water level and hydraulic conductivity datamore » are sparse, both of which were the case at this test location. The purpose of the study was to evaluate the first three methods for their ability to provide reasonable estimates of relatively low groundwater flow velocities in such low-hydraulic-gradient environments. The natural-gradient method is generally considered to be the most robust and direct method, so it was used to provide a “ground truth” velocity estimate. However, this method usually requires several wells, so it is often not practical in systems with large depths to groundwater and correspondingly high well installation costs. The fact that a successful natural gradient test was conducted at the test location offered a unique opportunity to compare the flow velocity estimates obtained by the more easily deployed and lower risk methods with the ground-truth natural-gradient method. The groundwater flow velocity estimates from the four methods agreed very well with each other, suggesting that the first three methods all provided reasonably good estimates of groundwater flow velocity at the site. We discuss the advantages and disadvantages of the different methods, as well as some of the uncertainties associated with them.« less

Evaluation of multiple tracer methods to estimate low groundwater flow velocities

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

Reimus, Paul W.; Arnold, Bill W.

Here, four different tracer methods were used to estimate groundwater flow velocity at a multiple-well site in the saturated alluvium south of Yucca Mountain, Nevada: (1) two single-well tracer tests with different rest or “shut-in” periods, (2) a cross-hole tracer test with an extended flow interruption, (3) a comparison of two tracer decay curves in an injection borehole with and without pumping of a downgradient well, and (4) a natural-gradient tracer test. Such tracer methods are potentially very useful for estimating groundwater velocities when hydraulic gradients are flat (and hence uncertain) and also when water level and hydraulic conductivity datamore » are sparse, both of which were the case at this test location. The purpose of the study was to evaluate the first three methods for their ability to provide reasonable estimates of relatively low groundwater flow velocities in such low-hydraulic-gradient environments. The natural-gradient method is generally considered to be the most robust and direct method, so it was used to provide a “ground truth” velocity estimate. However, this method usually requires several wells, so it is often not practical in systems with large depths to groundwater and correspondingly high well installation costs. The fact that a successful natural gradient test was conducted at the test location offered a unique opportunity to compare the flow velocity estimates obtained by the more easily deployed and lower risk methods with the ground-truth natural-gradient method. The groundwater flow velocity estimates from the four methods agreed very well with each other, suggesting that the first three methods all provided reasonably good estimates of groundwater flow velocity at the site. We discuss the advantages and disadvantages of the different methods, as well as some of the uncertainties associated with them.« less

Evaluation of multiple tracer methods to estimate low groundwater flow velocities.

PubMed

Reimus, Paul W; Arnold, Bill W

2017-04-01

Four different tracer methods were used to estimate groundwater flow velocity at a multiple-well site in the saturated alluvium south of Yucca Mountain, Nevada: (1) two single-well tracer tests with different rest or "shut-in" periods, (2) a cross-hole tracer test with an extended flow interruption, (3) a comparison of two tracer decay curves in an injection borehole with and without pumping of a downgradient well, and (4) a natural-gradient tracer test. Such tracer methods are potentially very useful for estimating groundwater velocities when hydraulic gradients are flat (and hence uncertain) and also when water level and hydraulic conductivity data are sparse, both of which were the case at this test location. The purpose of the study was to evaluate the first three methods for their ability to provide reasonable estimates of relatively low groundwater flow velocities in such low-hydraulic-gradient environments. The natural-gradient method is generally considered to be the most robust and direct method, so it was used to provide a "ground truth" velocity estimate. However, this method usually requires several wells, so it is often not practical in systems with large depths to groundwater and correspondingly high well installation costs. The fact that a successful natural gradient test was conducted at the test location offered a unique opportunity to compare the flow velocity estimates obtained by the more easily deployed and lower risk methods with the ground-truth natural-gradient method. The groundwater flow velocity estimates from the four methods agreed very well with each other, suggesting that the first three methods all provided reasonably good estimates of groundwater flow velocity at the site. The advantages and disadvantages of the different methods, as well as some of the uncertainties associated with them are discussed. Published by Elsevier B.V.

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

Reconstructing the groundwater flow in the Baltic Basin during the Last glaciation

NASA Astrophysics Data System (ADS)

Saks, T.; Sennikovs, J.; Timuhins, A.; Kalvāns, A.

2012-04-01

In last decades it has been discussed that most large ice sheets tend to reside on warm beds even in harsh clima tic conditions and subglacial melting occurs due to geothermal heat flow and deformation heat of the ice flow. However the subglacial groundwater recharge and flow conditions have been addressed in only few studies. The aim of this study is to establish the groundwater flow pattern in the Baltic Basin below the Scandinavian ice sheet during the Late Weichselian glaciation. The calculation results are compared to the known distribution of the groundwater body of the glacial origin found in Cambrian - Vendian (Cm-V) aquifer in the Northern Estonia which is believed to have originated as a result of subglacial meltwater infiltration during the reoccurring glaciations. Steady state regional groundwater flow model of the Baltic Basin was used to simulate the groundwater flow beneath the ice sheet with its geometry adjusted to reflect the subglacial topography. Ice thickness modelling data (Argus&Peltier, 2010) was used for the setup of the boundary conditions: the meltwater pressure at the ice bed was assumed equal to the overlying ice mass. The modelling results suggest two main recharge areas of the Cm-V aquifer system, and reversed groundwater flow that persisted for at least 14 thousand years. Model results show that the groundwater flow velocities in the Cm-V aquifer in the recharge area in N-Estonia beneath the ice sheet exceeded the present velocities by a factor of 10 on average. The calculated meltwater volume recharged into the Cm-V aquifer system during the Late Weichselian corresponds roughly to the estimated, however, considering the fact, that the study area has been glaciated at least 4 times this is an overestimation. The modeling results attest the hypothesis of light dO18 groundwater glacial origin in the Cm-V aquifer system, however the volumes, timing and processes involved in the meltwater intrusion are yet to be explored. This study was

Simulation of groundwater flow and interaction of groundwater and surface water on the Lac du Flambeau Reservation, Wisconsin

USGS Publications Warehouse

Juckem, Paul F.; Fienen, Michael N.; Hunt, Randall J.

2014-01-01

The Lac du Flambeau Band of Lake Superior Chippewa and Indian Health Service are interested in improving the understanding of groundwater flow and groundwater/surface-water interaction on the Lac du Flambeau Reservation (Reservation) in southwest Vilas County and southeast Iron County, Wisconsin, with particular interest in an understanding of the potential for contamination of groundwater supply wells and the fate of wastewater that is infiltrated from treatment lagoons on the Reservation. This report describes the construction, calibration, and application of a regional groundwater flow model used to simulate the shallow groundwater flow system of the Reservation and water-quality results for groundwater and surface-water samples collected near a system of waste-water-treatment lagoons. Groundwater flows through a permeable glacial aquifer that ranges in thickness from 60 to more than 200 feet (ft). Seepage and drainage lakes are common in the area and influence groundwater flow patterns on the Reservation. A two-dimensional, steady-state analytic element groundwater flow model was constructed using the program GFLOW. The model was calibrated by matching target water levels and stream base flows through the use of the parameter-estimation program, PEST. Simulated results illustrate that groundwater flow within most of the Reservation is toward the Bear River and the chain of lakes that feed the Bear River. Results of analyses of groundwater and surface-water samples collected downgradient from the wastewater infiltration lagoons show elevated levels of ammonia and dissolved phosphorus. In addition, wastewater indicator chemicals detected in three downgradient wells and a small downgradient stream indicate that infiltrated wastewater is moving southwest of the lagoons toward Moss Lake. Potential effects of extended wet and dry periods (within historical ranges) were evaluated by adjusting precipitation and groundwater recharge in the model and comparing the

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.

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.

A comprehensive surface-groundwater flow model

NASA Astrophysics Data System (ADS)

Arnold, Jeffrey G.; Allen, Peter M.; Bernhardt, Gilbert

1993-02-01

In this study, a simple groundwater flow and height model was added to an existing basin-scale surface water model. The linked model is: (1) watershed scale, allowing the basin to be subdivided; (2) designed to accept readily available inputs to allow general use over large regions; (3) continuous in time to allow simulation of land management, including such factors as climate and vegetation changes, pond and reservoir management, groundwater withdrawals, and stream and reservoir withdrawals. The model is described, and is validated on a 471 km 2 watershed near Waco, Texas. This linked model should provide a comprehensive tool for water resource managers in development and planning.

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

USGS Publications Warehouse

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

2016-02-23

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

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

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.

Redox zonation for different groundwater flow paths during bank filtration: a case study at Liao River, Shenyang, northeastern China

NASA Astrophysics Data System (ADS)

Su, Xiaosi; Lu, Shuai; Yuan, Wenzhen; Woo, Nam Chil; Dai, Zhenxue; Dong, Weihong; Du, Shanghai; Zhang, Xinyue

2018-03-01

The spatial and temporal distribution of redox zones in an aquifer is important when designing groundwater supply systems. Redox zonation can have direct or indirect control of the biological and chemical reactions and mobility of pollutants. In this study, redox conditions are characterized by interpreting the hydrogeological conditions and water chemistry in groundwater during bank infiltration at a site in Shenyang, northeast China. The relevant redox processes and zonal differences in a shallow flow path and deeper flow path at the field scale were revealed by monitoring the redox parameters and chemistry of groundwater near the Liao River. The results show obvious horizontal and vertical components of redox zones during bank filtration. Variations in the horizontal extent of the redox zone were controlled by the different permeabilities of the riverbed sediments and aquifer with depth. Horizontally, the redox zone was situated within 17 m of the riverbank for the shallow flow path and within 200 m for the deep flow path. The vertical extent of the redox zone was affected by precipitation and seasonal river floods and extended to 10 m below the surface. During bank filtration, iron and manganese oxides or hydroxides were reductively dissolved, and arsenic that was adsorbed onto the medium surface or coprecipitated is released into the groundwater. This leads to increased arsenic content in groundwater, which poses a serious threat to water supply security.

Numerical simulation of steady state three-dimensional groundwater flow near lakes

USGS Publications Warehouse

Winter, Thomas C.

1978-01-01

Numerical simulation of three-dimensional groundwater flow near lakes shows that the continuity of the boundary encompassing the local groundwater flow system associated with a lake is the key to understanding the interaction of a lake with the groundwater system. The continuity of the boundary can be determined by the presence of a stagnation zone coinciding with the side of the lake nearest the downgradient side of the groundwater system. For most settings modeled in this study the stagnation zone underlies the lakeshore, and it generally follows its curvature. The length of the stagnation zone is controlled by the geometry of the lake's drainage basin divide on the side of the lake nearest the downgradient side of the groundwater system. In the case of lakes that lose water to the groundwater system, three-dimensional modeling also allows for estimating the area of lake bed through which outseepage takes place. Analysis of the effects of size and lateral and vertical distribution of aquifers within the groundwater system on the outseepage from lakes shows that the position of the center point of the aquifer relative to the littoral zone on the side of the lake nearest the downgradient side of the groundwater system is a critical factor. If the center point is downslope from this part of the littoral zone, the local flow system boundary tends to be weak or outseepage occurs. If the center point is upslope from this littoral zone, the stagnation zone tends to be stronger (to have a higher head in relation to lake level), and outseepage is unlikely to occur.

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.

Controls on groundwater flow in the Bengal Basin of India and Bangladesh: regional modeling analysis

NASA Astrophysics Data System (ADS)

Michael, Holly A.; Voss, Clifford I.

2009-11-01

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.

Hydrologic and geochemical approaches for determining ground-water flow components

USGS Publications Warehouse

Hjalmarson, H.W.; Robertson, F.N.

1991-01-01

Lyman Lake is an irrigation-storage reservoir on the Little Colorado River near St. Johns, Arizona. The main sources of water for the lake are streamflow in the Little Colorado River and ground-water inflow from the underlying Coconino aquifer. Two approaches, a hydrologic analysis and a geochemical analysis, were used to compute the quantity of ground-water flow to and from Lyman Lake. Hydrologic data used to calculate a water budget were precipitation on the lake, evaporation from the lake, transpiration from dense vegetation, seepage through the dam, streamflow in and out of the lake, and changes in lake storage. Geochemical data used to calculate the ground-water flow components were major ions, trace elements, and the stable isotopes of hydrogen and oxygen. During the study, the potentiometric level of the Coconino aquifer was above the lake level at the upstream end of the lake and below the lake level at the downstream end. Hydrologic and geochemical data indicate that about 10 percent and 8 percent, respectively, of the water in the lake is ground-water inflow and that about 35 percent of the water in the Little Colorado River 6 miles downgradient from the lake near Salado Springs is ground water. These independent estimates of ground-water flow derived from each approach are in agreement and support a conceptual model of the water budget.

Ambient groundwater flow diminishes nitrogen cycling in streams

NASA Astrophysics Data System (ADS)

Azizian, M.; Grant, S. B.; Rippy, M.; Detwiler, R. L.; Boano, F.; Cook, P. L. M.

2017-12-01

Modeling and experimental studies demonstrate that ambient groundwater reduces hyporheic exchange, but the implications of this observation for stream N-cycling is not yet clear. We utilized a simple process-based model (the Pumping and Streamline Segregation or PASS model) to evaluate N- cycling over two scales of hyporheic exchange (fluvial ripples and riffle-pool sequences), ten ambient groundwater and stream flow scenarios (five gaining and losing conditions and two stream discharges), and three biogeochemical settings (identified based on a principal component analysis of previously published measurements in streams throughout the United States). Model-data comparisons indicate that our model provides realistic estimates for direct denitrification of stream nitrate, but overpredicts nitrification and coupled nitrification-denitrification. Riffle-pool sequences are responsible for most of the N-processing, despite the fact that fluvial ripples generate 3-11 times more hyporheic exchange flux. Across all scenarios, hyporheic exchange flux and the Damkohler Number emerge as primary controls on stream N-cycling; the former regulates trafficking of nutrients and oxygen across the sediment-water interface, while the latter quantifies the relative rates of organic carbon mineralization and advective transport in streambed sediments. Vertical groundwater flux modulates both of these master variables in ways that tend to diminish stream N-cycling. Thus, anthropogenic perturbations of ambient groundwater flows (e.g., by urbanization, agricultural activities, groundwater mining, and/or climate change) may compromise some of the key ecosystem services provided by streams.

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

Numerical groundwater-flow modeling to evaluate potential effects of pumping and recharge: implications for sustainable groundwater management in the Mahanadi delta region, India

NASA Astrophysics Data System (ADS)

Sahoo, Sasmita; Jha, Madan K.

2017-12-01

Process-based groundwater models are useful to understand complex aquifer systems and make predictions about their response to hydrological changes. A conceptual model for evaluating responses to environmental changes is presented, considering the hydrogeologic framework, flow processes, aquifer hydraulic properties, boundary conditions, and sources and sinks of the groundwater system. Based on this conceptual model, a quasi-three-dimensional transient groundwater flow model was designed using MODFLOW to simulate the groundwater system of Mahanadi River delta, eastern India. The model was constructed in the context of an upper unconfined aquifer and lower confined aquifer, separated by an aquitard. Hydraulic heads of 13 shallow wells and 11 deep wells were used to calibrate transient groundwater conditions during 1997-2006, followed by validation (2007-2011). The aquifer and aquitard hydraulic properties were obtained by pumping tests and were calibrated along with the rainfall recharge. The statistical and graphical performance indicators suggested a reasonably good simulation of groundwater flow over the study area. Sensitivity analysis revealed that groundwater level is most sensitive to the hydraulic conductivities of both the aquifers, followed by vertical hydraulic conductivity of the confining layer. The calibrated model was then employed to explore groundwater-flow dynamics in response to changes in pumping and recharge conditions. The simulation results indicate that pumping has a substantial effect on the confined aquifer flow regime as compared to the unconfined aquifer. The results and insights from this study have important implications for other regional groundwater modeling studies, especially in multi-layered aquifer systems.

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.

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. 

Effects of groundwater-flow paths on nitrate concentrations across two riparian forest corridors

USGS Publications Warehouse

Speiran, Gary K.

2010-01-01

Groundwater levels, apparent age, and chemistry from field sites and groundwater-flow modeling of hypothetical aquifers collectively indicate that groundwater-flow paths contribute to differences in nitrate concentrations across riparian corridors. At sites in Virginia (one coastal and one Piedmont), lowland forested wetlands separate upland fields from nearby surface waters (an estuary and a stream). At the coastal site, nitrate concentrations near the water table decreased from more than 10 mg/L beneath fields to 2 mg/L beneath a riparian forest buffer because recharge through the buffer forced water with concentrations greater than 5 mg/L to flow deeper beneath the buffer. Diurnal changes in groundwater levels up to 0.25 meters at the coastal site reflect flow from the water table into unsaturated soil where roots remove water and nitrate dissolved in it. Decreases in aquifer thickness caused by declines in the water table and decreases in horizontal hydraulic gradients from the uplands to the wetlands indicate that more than 95% of the groundwater discharged to the wetlands. Such discharge through organic soil can reduce nitrate concentrations by denitrification. Model simulations are consistent with field results, showing downward flow approaching toe slopes and surface waters to which groundwater discharges. These effects show the importance of buffer placement over use of fixed-width, streamside buffers to control nitrate concentrations.

Uncertainty in simulated groundwater-quality trends in transient flow

USGS Publications Warehouse

Starn, J. Jeffrey; Bagtzoglou, Amvrossios; Robbins, Gary A.

2013-01-01

In numerical modeling of groundwater flow, the result of a given solution method is affected by the way in which transient flow conditions and geologic heterogeneity are simulated. An algorithm is demonstrated that simulates breakthrough curves at a pumping well by convolution-based particle tracking in a transient flow field for several synthetic basin-scale aquifers. In comparison to grid-based (Eulerian) methods, the particle (Lagrangian) method is better able to capture multimodal breakthrough caused by changes in pumping at the well, although the particle method may be apparently nonlinear because of the discrete nature of particle arrival times. Trial-and-error choice of number of particles and release times can perhaps overcome the apparent nonlinearity. Heterogeneous aquifer properties tend to smooth the effects of transient pumping, making it difficult to separate their effects in parameter estimation. Porosity, a new parameter added for advective transport, can be accurately estimated using both grid-based and particle-based methods, but predictions can be highly uncertain, even in the simple, nonreactive case.

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

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.

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

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

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.

Numerical simulation of groundwater flow at Puget Sound Naval Shipyard, Naval Base Kitsap, Bremerton, Washington

USGS Publications Warehouse

Jones, Joseph L.; Johnson, Kenneth H.; Frans, Lonna M.

2016-08-18

Information about groundwater-flow paths and locations where groundwater discharges at and near Puget Sound Naval Shipyard is necessary for understanding the potential migration of subsurface contaminants by groundwater at the shipyard. The design of some remediation alternatives would be aided by knowledge of whether groundwater flowing at specific locations beneath the shipyard will eventually discharge directly to Sinclair Inlet of Puget Sound, or if it will discharge to the drainage system of one of the six dry docks located in the shipyard. A 1997 numerical (finite difference) groundwater-flow model of the shipyard and surrounding area was constructed to help evaluate the potential for groundwater discharge to Puget Sound. That steady-state, multilayer numerical model with homogeneous hydraulic characteristics indicated that groundwater flowing beneath nearly all of the shipyard discharges to the dry-dock drainage systems, and only shallow groundwater flowing beneath the western end of the shipyard discharges directly to Sinclair Inlet.Updated information from a 2016 regional groundwater-flow model constructed for the greater Kitsap Peninsula was used to update the 1997 groundwater model of the Puget Sound Naval Shipyard. That information included a new interpretation of the hydrogeologic units underlying the area, as well as improved recharge estimates. Other updates to the 1997 model included finer discretization of the finite-difference model grid into more layers, rows, and columns, all with reduced dimensions. This updated Puget Sound Naval Shipyard model was calibrated to 2001–2005 measured water levels, and hydraulic characteristics of the model layers representing different hydrogeologic units were estimated with the aid of state-of-the-art parameter optimization techniques.The flow directions and discharge locations predicted by this updated model generally match the 1997 model despite refinements and other changes. In the updated model, most

Hydrogeology and ground-water flow in the carbonate rocks of the Little Lehigh Creek basin, Lehigh County, Pennsylvania

USGS Publications Warehouse

Sloto, R.A.; Cecil, L.D.; Senior, L.A.

1991-01-01

The Little Lehigh Creek basin is underlain mainly by a complex assemblage of highly-deformed Cambrian and Ordovician carbonate rocks. The Leithsville Formation, Allentown Dolomite, Beekmantown Group, and Jacksonburg Limestone act as a single hydrologic unit. Ground water moves through fractures and other secondary openings and generally is under water-table conditions. Median annual ground-water discharge (base flow) to Little Lehigh Creek near Allentown (station 01451500) during 1946-86 was 12.97 inches or 82 percent of streamflow. Average annual recharge for 1975-83 was 21.75 inches. Groundwater and surface-water divides do not coincide in the basin. Ground-water underflow from the Little Lehigh Creek basin to the Cedar Creek basin in 1987 was 4 inches per year. A double-mass curve analysis of the relation of cumulative precipitation at Allentown to the flow of Schantz Spring for 1956-84 showed that cessation of quarry pumping and development of ground water for public supply in the Schantz Spring basin did not affect the flow of Schantz Spring. Ground-water flow in the Little Lehigh Creek basin was simulated using a finite-difference, two-dimensional computer model. The geologic units in the modeled area were simulated as a single water-table aquifer. The 134-squaremile area of carbonate rocks between the Lehigh River and Sacony Creek was modeled to include the natural hydrologic boundaries of the ground-water-flow system. The ground-water-flow model was calibrated under steady-state conditions using 1975-83 average recharge, evapotranspiration, and pumping rates. Each geologic unit was assigned a different hydraulic conductivity. Initial aquifer hydraulic conductivity was estimated from specific-capacity data. The average (1975-83) water budget for the Little Lehigh Creek basin was simulated. The simulated base flow from the carbonate rocks of the Little Lehigh Creek basin above gaging station 01451500 is 11.85 inches per year. The simulated ground-water

An analytical study on groundwater flow in drainage basins with horizontal wells

NASA Astrophysics Data System (ADS)

Wang, Jun-Zhi; Jiang, Xiao-Wei; Wan, Li; Wang, Xu-Sheng; Li, Hailong

2014-06-01

Analytical studies on release/capture zones are often limited to a uniform background groundwater flow. In fact, for basin-scale problems, the undulating water table would lead to the development of hierarchically nested flow systems, which are more complex than a uniform flow. Under the premise that the water table is a replica of undulating topography and hardly influenced by wells, an analytical solution of hydraulic head is derived for a two-dimensional cross section of a drainage basin with horizontal injection/pumping wells. Based on the analytical solution, distributions of hydraulic head, stagnation points and flow systems (including release/capture zones) are explored. The superposition of injection/pumping wells onto the background flow field leads to the development of new internal stagnation points and new flow systems (including release/capture zones). Generally speaking, the existence of n injection/pumping wells would result in up to n new internal stagnation points and up to 2n new flow systems (including release/capture zones). The analytical study presented, which integrates traditional well hydraulics with the theory of regional groundwater flow, is useful in understanding basin-scale groundwater flow influenced by human activities.

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

PubMed

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

2011-02-01

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

Use of RORA for Complex Ground-Water Flow Conditions

USGS Publications Warehouse

Rutledge, A.T.

2004-01-01

The RORA computer program for estimating recharge is based on a condition in which ground water flows perpendicular to the nearest stream that receives ground-water discharge. The method, therefore, does not explicitly account for the ground-water-flow component that is parallel to the stream. Hypothetical finite-difference simulations are used to demonstrate effects of complex flow conditions that consist of two components: one that is perpendicular to the stream and one that is parallel to the stream. Results of the simulations indicate that the RORA program can be used if certain constraints are applied in the estimation of the recession index, an input variable to the program. These constraints apply to a mathematical formulation based on aquifer properties, recession of ground-water levels, and recession of streamflow.

Simulation of the effects of rainfall and groundwater use on historical lake water levels, groundwater levels, and spring flows in central Florida

USGS Publications Warehouse

O'Reilly, Andrew M.; Roehl, Edwin A.; Conrads, Paul; Daamen, Ruby C.; Petkewich, Matthew D.

2014-01-01

in water levels and flows were identified that are consistent with historical groundwater-use patterns. The sensitivity of the hydrologic system to rainfall is expected, owing to the well-drained karst terrain and relatively thin confinement of the Floridan aquifer system in much of central Florida. These characteristics facilitate the relatively rapid transmission of infiltrating water from rainfall to the water table and contribute to downward leakage of water to the Floridan aquifer system. The areally distributed nature of rainfall, as opposed to the site-specific nature of groundwater use, and the generally high transmissivity and low storativity properties of the semiconfined Floridan aquifer system contribute to the prevalence of water-level and flow patterns that mimic rainfall patterns. In general, the data-mining analyses demonstrate that the hydrologic system in central Florida is affected by groundwater use differently during wet periods, when little or no system storage is available (high water levels), compared to dry periods, when there is excess system storage (low water levels). Thus, by driving the overall behavior of the system, rainfall indirectly influences the degree to which groundwater use will effect persistent trends in water levels and flows, with groundwater-use impacts more prevalent during periods of low water levels and spring flows caused by low rainfall and less prevalent during periods of high water levels and spring flows caused by high rainfall. Differences in the magnitudes of rainfall and groundwater use during wet and dry periods also are important determinants of hydrologic response. An important implication of the data-mining analyses is that rainfall variability at subannual to multidecadal timescales must be considered in combination with groundwater use to provide robust system-response predictions that enhance sustainable resource management in an open karst aquifer system. The data-driven approach was limited, however, by

Simulation of the Groundwater-Flow System in Pierce, Polk, and St. Croix Counties, Wisconsin

USGS Publications Warehouse

Juckem, Paul F.

2009-01-01

Groundwater is the sole source of residential water supply in Pierce, Polk, and St. Croix Counties, Wisconsin. A regional three-dimensional groundwater-flow model and three associated demonstration inset models were developed to simulate the groundwater-flow systems in the three-county area. The models were developed by the U.S. Geological Survey in cooperation with the three county governments. The objectives of the regional model of Pierce, Polk, and St. Croix Counties were to improve understanding of the groundwaterflow system and to develop a tool suitable for evaluating the effects of potential water-management programs. The regional groundwater-flow model described in this report simulates the major hydrogeologic features of the modeled area, including bedrock and surficial aquifers, groundwater/surface-water interactions, and groundwater withdrawals from high-capacity wells. Results from the regional model indicate that about 82 percent of groundwater in the three counties is from recharge within the counties; 15 percent is from surface-water sources, consisting primarily of recirculated groundwater seepage in areas with abrupt surface-water-level changes, such as near waterfalls, dams, and the downgradient side of reservoirs and lakes; and 4 percent is from inflow across the county boundaries. Groundwater flow out of the counties is to streams (85 percent), outflow across county boundaries (14 percent), and pumping wells (1 percent). These results demonstrate that the primary source of groundwater withdrawn by pumping wells is water that recharges within the counties and would otherwise discharge to local streams and lakes. Under current conditions, the St. Croix and Mississippi Rivers are groundwater discharge locations (gaining reaches) and appear to function as 'fully penetrating' hydraulic boundaries such that groundwater does not cross between Wisconsin and Minnesota beneath them. Being hydraulic boundaries, however, they can change in response to

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

Two-dimensional advective transport in ground-water flow parameter estimation

USGS Publications Warehouse

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

1996-01-01

Nonlinear regression is useful in ground-water flow parameter estimation, but problems of parameter insensitivity and correlation often exist given commonly available hydraulic-head and head-dependent flow (for example, stream and lake gain or loss) observations. To address this problem, advective-transport observations are added to the ground-water flow, parameter-estimation model MODFLOWP using particle-tracking methods. The resulting model is used to investigate the importance of advective-transport observations relative to head-dependent flow observations when either or both are used in conjunction with hydraulic-head observations in a simulation of the sewage-discharge plume at Otis Air Force Base, Cape Cod, Massachusetts, USA. The analysis procedure for evaluating the probable effect of new observations on the regression results consists of two steps: (1) parameter sensitivities and correlations calculated at initial parameter values are used to assess the model parameterization and expected relative contributions of different types of observations to the regression; and (2) optimal parameter values are estimated by nonlinear regression and evaluated. In the Cape Cod parameter-estimation model, advective-transport observations did not significantly increase the overall parameter sensitivity; however: (1) inclusion of advective-transport observations decreased parameter correlation enough for more unique parameter values to be estimated by the regression; (2) realistic uncertainties in advective-transport observations had a small effect on parameter estimates relative to the precision with which the parameters were estimated; and (3) the regression results and sensitivity analysis provided insight into the dynamics of the ground-water flow system, especially the importance of accurate boundary conditions. In this work, advective-transport observations improved the calibration of the model and the estimation of ground-water flow parameters, and use of

Microbes Characteristics in Groundwater Flow System in Mountainous Area

NASA Astrophysics Data System (ADS)

Yamamoto, Chisato; Tsujimura, Maki; Kato, Kenji; Sakakibara, Koichi; Ogawa, Mahiro; Sugiyama, Ayumi; Nagaosa, Kazuyo

2017-04-01

We focus on a possibility of microbes as a tracer for groundwater flow investigation. Some previous papers showed that the total number of prokaryotes in groundwater has correlation with depth and geology (Parkes et al., 1994; Griebler et al., 2009; Kato et al., 2012). However, there are few studies investigating both microbe characteristics and groundwater flow system. Therefore, we investigated a relationship between the total number of prokaryotes and age of spring water and groundwater. Intensive field survey was conducted at four mountainous areas, namely Mt. Fuji (volcano), a headwater at Mt. Setohachi, a headwater at River Oi and a headwater at River Nagano underlain by volcanic lava at Mt. Fuji, granite at Mt. Setohachi and sedimentary rock at River Oi and River Nagano. We collected totally 40 spring water/ groundwater samples in these mountainous areas in October 2015, August, October and November 2016 and analyzed concentration of inorganic ions, the stable isotopes of oxygen - 18, deuterium, CFCs and SF6. Also, we counted prokaryotic cells under the epifluorescence microscopy after fixation and filteration. The total number of prokaryotes in the spring water/ groundwater ranged from 1.0×102 to 7.0×103cells mL-1 at the Mt. Fuji, 1.3×104 to 2.7×105cells mL-1 at Mt. Setohachi, 3.1×104cells mL-1 at River Oi and 1.8×105 to 3.2×106cells mL-1 at River Nagano. The SF6 age of the spring water/ groundwater ranged from 8 to 64 years at Mt. Fuji, 2 to 32.5 years at Mt. Setohachi, 2.5 years at River Oi and 15 to 16 years at River Nagano. The total number of prokaryotes showed a clear negative correlation with residence time of spring water/ groundwater in all regions. Especially the prokaryotes number increased in the order of 102 cells mL-1 with decreasing of residence time in approximately 10 years in the groundwater and spring water with the age less than 15 years.

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

Simulation of ground-water/surface-water flow in the Santa Clara-Calleguas ground-water basin, Ventura County, California

USGS Publications Warehouse

Hanson, Randall T.; Martin, Peter; Koczot, Kathryn M.

2003-01-01

Ground water is the main source of water in the Santa Clara-Calleguas ground-water basin that covers about 310 square miles in Ventura County, California. A steady increase in the demand for surface- and ground-water resources since the late 1800s has resulted in streamflow depletion and ground-water overdraft. This steady increase in water use has resulted in seawater intrusion, inter-aquifer flow, land subsidence, and ground-water contamination. The Santa Clara-Calleguas Basin consists of multiple aquifers that are grouped into upper- and lower-aquifer systems. The upper-aquifer system includes the Shallow, Oxnard, and Mugu aquifers. The lower-aquifer system includes the upper and lower Hueneme, Fox Canyon, and Grimes Canyon aquifers. The layered aquifer systems are each bounded below by regional unconformities that are overlain by extensive basal coarse-grained layers that are the major pathways for ground-water production from wells and related seawater intrusion. The aquifer systems are bounded below and along mountain fronts by consolidated bedrock that forms a relatively impermeable boundary to ground-water flow. Numerous faults act as additional exterior and interior boundaries to ground-water flow. The aquifer systems extend offshore where they crop out along the edge of the submarine shelf and within the coastal submarine canyons. Submarine canyons have dissected these regional aquifers, providing a hydraulic connection to the ocean through the submarine outcrops of the aquifer systems. Coastal landward flow (seawater intrusion) occurs within both the upper- and lower-aquifer systems. A numerical ground-water flow model of the Santa Clara-Calleguas Basin was developed by the U.S. Geological Survey to better define the geohydrologic framework of the regional ground-water flow system and to help analyze the major problems affecting water-resources management of a typical coastal aquifer system. Construction of the Santa Clara-Calleguas Basin model required

Simulation of regional ground-water flow in the Upper Deschutes Basin, Oregon

USGS Publications Warehouse

Gannett, Marshall W.; Lite, Kenneth E.

2004-01-01

This report describes a numerical model that simulates regional ground-water flow in the upper Deschutes Basin of central Oregon. Ground water and surface water are intimately connected in the upper Deschutes Basin and most of the flow of the Deschutes River is supplied by ground water. Because of this connection, ground-water pumping and reduction of artificial recharge by lining leaking irrigation canals can reduce the amount of ground water discharging to streams and, consequently, streamflow. The model described in this report is intended to help water-management agencies and the public evaluate how the regional ground-water system and streamflow will respond to ground-water pumping, canal lining, drought, and other stresses. Ground-water flow is simulated in the model by the finite-difference method using MODFLOW and MODFLOWP. The finite-difference grid consists of 8 layers, 127 rows, and 87 columns. All major streams and most principal tributaries in the upper Deschutes Basin are included. Ground-water recharge from precipitation was estimated using a daily water-balance approach. Artificial recharge from leaking irrigation canals and on-farm losses was estimated from diversion and delivery records, seepage studies, and crop data. Ground-water pumpage for irrigation and public water supplies, and evapotranspiration are also included in the model. The model was calibrated to mean annual (1993-95) steady-state conditions using parameter-estimation techniques employing nonlinear regression. Fourteen hydraulic-conductivity parameters and two vertical conductance parameters were determined using nonlinear regression. Final parameter values are all within expected ranges. The general shape and slope of the simulated water-table surface and overall hydraulic-head distribution match the geometry determined from field measurements. The fitted standard deviation for hydraulic head is about 76 feet. The general magnitude and distribution of ground-water discharge to

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

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

USGS Publications Warehouse

Kozar, Mark D.; Weary, David J.

2009-01-01

model to develop a realistic simulation of ground-water flow in the larger Opequon Creek watershed area. In the model, recharge for average hydrologic conditions was 689 m3/d/km2 (cubic meters per day per square kilometer) over the entire Opequon Creek watershed area. Mean and median measured base flows at the streamflow-gaging station on the Opequon Creek near Martinsburg, West Virginia, were 604,384 and 349,907 m3/d (cubic meters per day), respectively. The simulated base flow of 432,834 m3/d fell between the mean and median measured stream base flows for the station. Simulated base-flow yields for subwatersheds during average conditions ranged from 0 to 2,643 m3/d/km2, and the median for the entire Opequon Creek watershed area was 557 m3/d/km2. A drought was simulated by reducing model recharge by 40 percent, a rate that approximates the recharge during the prolonged 16-month drought that affected the region from November 1998 to February 2000. Mean and median measured streamflows for the Opequon Creek watershed area at the Martinsburg, West Virginia, streamflow-gaging station during the 1999 drought were 341,098 and 216,551 m3/d, respectively. The simulated drought base flow at the station of 252,356 m3/d is within the range of flows measured during the 1999 drought. Recharge was 413 m3/d/km2 over the entire watershed during the simulated drought, and was 388 m3/d/km2 at the gaging station. Simulated base-flow yields for drought conditions ranged from 0 to 1,865 m3/d/km2 and averaged 327 m3/d/km2 over the entire Opequon Creek watershed. Water budgets developed from the simulation results indicate a substantial component of direct ground-water discharge to the Potomac River. This phenomenon had long been suspected but had not been quantified. During average conditions, approximately 564,176 m3/d of base flow discharges to the Potomac River. An additional 124,379 m3/d of ground water is also estimated to discharge directly to the Potomac River and rep

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.

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

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

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

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 depthmore » 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

The Practical Application of Aqueous Geochemistry in Mapping Groundwater Flow Systems in Fractured Rock Masses

NASA Astrophysics Data System (ADS)

Bursey, G.; Seok, E.; Gale, J. E.

2017-12-01

Flow to underground mines and open pits takes place through an interconnected network of regular joints/fractures and intermediate to large scale structural features such as faults and fracture zones. Large scale features can serve either as high permeability pathways or as barriers to flow, depending on the internal characteristics of the structure. Predicting long term water quality in barrier-well systems and long-term mine water inflows over a mine life, as a mine expands, requires the use of a 3D numerical flow and transport code. The code is used to integrate the physical geometry of the fractured-rock mass with porosity, permeability, hydraulic heads, storativity and recharge data and construct a model of the flow system. Once that model has been calibrated using hydraulic head and permeability/inflow data, aqueous geochemical and isotopic data provide useful tools for validating flow-system properties, when one is able to recognize and account for the non-ideal or imperfect aspects of the sampling methods used in different mining environments. If groundwater samples are collected from discrete depths within open boreholes, water in those boreholes have the opportunity to move up or down in response to the forces that drive groundwater flow, whether they be hydraulic gradients, gas pressures, or density differences associated with variations in salinity. The use of Br/Cl ratios, for example, can be used to determine if there is active flow into, or out of, the boreholes through open discontinuities in the rock mass (i.e., short-circuiting). Natural groundwater quality can also be affected to varying degrees by mixing with drilling fluids. The combined use of inorganic chemistry and stable isotopes can be used effectively to identify dilution signals and map the dilution patterns through a range of fresh, brackish and saline water types. The stable isotopes of oxygen and hydrogen are nearly ideal natural tracers of water, but situations occur when deep

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

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.

Spatiotemporal Responses of Groundwater Flow and Aquifer-River Exchanges to Flood Events

NASA Astrophysics Data System (ADS)

Liang, Xiuyu; Zhan, Hongbin; Schilling, Keith

2018-03-01

Rapidly rising river stages induced by flood events lead to considerable river water infiltration into aquifers and carry surface-borne solutes into hyporheic zones which are widely recognized as an important place for the biogeochemical activity. Existing studies for surface-groundwater exchanges induced by flood events usually limit to a river-aquifer cross section that is perpendicular to river channels, and neglect groundwater flow in parallel with river channels. In this study, surface-groundwater exchanges to a flood event are investigated with specific considerations of unconfined flow in direction that is in parallel with river channels. The groundwater flow is described by a two-dimensional Boussinesq equation and the flood event is described by a diffusive-type flood wave. Analytical solutions are derived and tested using the numerical solution. The results indicate that river water infiltrates into aquifers quickly during flood events, and mostly returns to the river within a short period of time after the flood event. However, the rest river water will stay in aquifers for a long period of time. The residual river water not only flows back to rivers but also flows to downstream aquifers. The one-dimensional model of neglecting flow in the direction parallel with river channels will overestimate heads and discharge in upstream aquifers. The return flow induced by the flood event has a power law form with time and has a significant impact on the base flow recession at early times. The solution can match the observed hydraulic heads in riparian zone wells of Iowa during flood events.

Simulation and assessment of groundwater flow and groundwater and surface-water exchanges in lakes of the northeast Twin Cities Metropolitan Area, Minnesota, 2003 through 2013: Chapter B of Water levels and groundwater and surface-water exchanges in lakes of the northeast Twin Cities Metropolitan Area, Minnesota, 2002 through 2015

USGS Publications Warehouse

Jones, Perry M.; Roth, Jason L.; Trost, Jared J.; Christenson, Catherine A.; Diekoff, Aliesha L.; Erickson, Melinda L.

2017-09-05

, and White Bear Lake. Simulated lake-water levels and budgets for Snail Lake and White Bear Lake were affected by 30-percent changes in groundwater withdrawals and 5-percent changes in precipitation in the area, whereas the water level in Big Marine Lake was mainly affected by 5-percent precipitation changes. The effects of groundwater withdrawals on the lake-water levels depend on the number of wells and amount of withdrawals from wells near the lakes. Although lake-water levels are sensitive to precipitation changes, increases in groundwater withdrawals during dry periods exacerbate lake-water level declines. The calibrated, groundwater-flow model is a tool that water-resources managers can use to address future water management issues in the northeast Twin Cities Metropolitan Area.

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

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.

Ground-water flow and ground- and surface-water interaction at McBaine Bottoms, Columbia, Missouri--2000-02

USGS Publications Warehouse

Smith, Brenda J.

2003-01-01

gradients around the high became more shallow than in the winter months. In early summer, the high was the least pronounced. During mid-sum-mer, the high became more pronounced, and it continued to become higher, increasing until it reached its maximum height in late fall or early winter. Fluctuations in the ground-water high were partially produced by the cycle of flooding of the Eagle Bluffs Conservation Area wetland pools in the fall and subsequent drainage so crops could be planted in many of the wetland pools. The cone of depression in the northern part of the study area generally extended from the base of the ground-water high in the northern part of the Eagle Bluffs Conservation Area throughout the rest of the study area. The depth of the cone primarily was affected by the altitude of the Missouri River and the quantity of water being pumped from the alluvial aquifer by the city of Columbia well field. Ground-water flow in the alluvial aquifer in McBaine Bottoms in the late 1960?s before the development of the city of Columbia well field and the Eagle Bluffs Conservation Area was from northwest to southeast approximately parallel to the Missouri River. The ground-water high beneath the Eagle Bluffs Conservation Area and the cone of depression around the city of Columbia well field were not present in water-level maps for 1968 and 1978. The Missouri River can be a source of recharge to the alluvial aquifer. Generally the altitude of the river in the northern part of the study area was higher than the water table in the aquifer. Ground-water flow in this area was from the river into the alluvial aquifer. In the southern part of the study area adjacent to the Eagle Bluffs Conservation Area, the Missouri River was lower than the water table in the alluvial aquifer, indicating that the river was receiving water from the alluvial aquifer beneath the Eagle Bluffs Conservation Area.

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

Use of temperature profiles beneath streams to determine rates of vertical ground-water flow and vertical hydraulic conductivity

USGS Publications Warehouse

Lapham, Wayne W.

1989-01-01

The use of temperature profiles beneath streams to determine rates of vertical ground-water flow and effective vertical hydraulic conductivity of sediments was evaluated at three field sites by use of a model that numerically solves the partial differential equation governing simultaneous vertical flow of fluid and heat in the Earth. The field sites are located in Hardwick and New Braintree, Mass., and in Dover, N.J. In New England, stream temperature varies from about 0 to 25 ?C (degrees Celsius) during the year. This stream-temperature fluctuation causes ground-water temperatures beneath streams to fluctuate by more than 0.1 ?C during a year to a depth of about 35 ft (feet) in fine-grained sediments and to a depth of about 50 ft in coarse-grained sediments, if ground-water velocity is 0 ft/d (foot per day). Upward flow decreases the depth affected by stream-temperature fluctuation, and downward flow increases the depth. At the site in Hardwick, Mass., ground-water flow was upward at a rate of less than 0.01 ft/d. The maximum effective vertical hydraulic conductivity of the sediments underlying this site is 0.1 ft/d. Ground-water velocities determined at three locations at the site in New Braintree, Mass., where ground water discharges naturally from the underlying aquifer to the Ware River, ranged from 0.10 to 0.20 ft/d upward. The effective vertical hydraulic conductivity of the sediments underlying this site ranged from 2.4 to 17.1 ft/d. Ground-water velocities determined at three locations at the Dover, N.J., site, where infiltration from the Rockaway River into the underlying sediments occurs because of pumping, were 1.5 ft/d downward. The effective vertical hydraulic conductivity of the sediments underlying this site ranged from 2.2 to 2.5 ft/d. Independent estimates of velocity at two of the three sites are in general agreement with the velocities determined using temperature profiles. The estimates of velocities and conductivities derived from the

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

A three-dimensional analytical model to simulate groundwater flow during operation of recirculating wells

NASA Astrophysics Data System (ADS)

Huang, Junqi; Goltz, Mark N.

2005-11-01

The potential for using pairs of so-called horizontal flow treatment wells (HFTWs) to effect in situ capture and treatment of contaminated groundwater has recently been demonstrated. To apply this new technology, design engineers need to be able to simulate the relatively complex groundwater flow patterns that result from HFTW operation. In this work, a three-dimensional analytical solution for steady flow in a homogeneous, anisotropic, contaminated aquifer is developed to efficiently calculate the interflow of water circulating between a pair of HFTWs and map the spatial extent of contaminated groundwater flowing from upgradient that is captured. The solution is constructed by superposing the solutions for the flow fields resulting from operation of partially penetrating wells. The solution is used to investigate the flow resulting from operation of an HFTW well pair and to quantify how aquifer anisotropy, well placement, and pumping rate impact capture zone width and interflow. The analytical modeling method presented here provides a fast and accurate technique for representing the flow field resulting from operation of HFTW systems, and represents a tool that can be useful in designing in situ groundwater contamination treatment systems.

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

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

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

Chemical evolution of groundwater near a sinkhole lake, northern Florida: 1. Flow patterns, age of groundwater, and influence of lakewater leakage

USGS Publications Warehouse

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

1995-01-01

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.

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

Deep thermal disturbances related to the sub-surface groundwater flow (Western Alps, France)

NASA Astrophysics Data System (ADS)

Mommessin, Grégoire; Dzikowski, Marc; Menard, Gilles; Monin, Nathalie

2013-04-01

In mountain area, the bedrock of the valley side is affected by a thickness of decompressed rock in subsurface (decompressed zone). Groundwater flowing in this zone disrupts the depth geothermal gradients. The evolution of thermal gradients under the decompressed zone depends of groundwater temperature changes into the decompressed zone. In this study, the phenomenon is studied from data acquired in exploration drilling prior to the construction of the France - Italy transalpine tunnel (High Speed Line project between Lyon and Turin). The study area is located in the Vanoise siliceous series between Modane and Avrieux (Western Alps, France). Of 31 boreholes, we selected 14 wells showing a natural thermal disturbance (not due to the drilling) linked to the groundwater flow in decompressed zone. The drill holes have a length between 200 and 1380m and well logs were carried out (gamma log, acoustic log, temperature log, flowmeter log). The rocks are constituted mainly by quartzite with high thermal conductivity or by schist and gneiss with low thermal conductivity. The decompressed zone concerns the quartzite with thicknesses ranging from 50m to 750m where groundwater flow imposes a constant temperature throughout the rock thickness. In the very low permeability rocks under the decompressed zone, the thermal gradient shows variations with depth. These variations suggest a water temperature change in the decompressed zone probably due to a paleoclimate event. We used the derived of the equation describing the propagation of a temperature in a 1D semi-infinite, in response to a sudden temperature disturbance at the boundary of the medium, to estimate the age and the amplitude of temperature change in the decompressed zone. The medium under the decompressed zone is supposed to be initially in a steady state and only conductive. Numerical tests assess that the 1D model is applicable in the slope context. The results obtained from 13 wells data show a few warming degrees

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.

2016-03-15

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.

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

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

Identifying three-dimensional nested groundwater flow systems in a Tóthian basin

NASA Astrophysics Data System (ADS)

Wang, Xu-Sheng; Wan, Li; Jiang, Xiao-Wei; Li, Hailong; Zhou, Yangxiao; Wang, Junzhi; Ji, Xiaohui

2017-10-01

Nested groundwater flow systems have been revealed in Tóth's theory as the structural property of basin-scale groundwater circulation but were only well known with two-dimensional (2D) profile models. The method of searching special streamlines across stagnation points for partitioning flow systems, which has been successfully applied in the 2D models, has never been implemented for three-dimensional (3D) Tóthian basins because of the difficulty in solving the dual stream functions. Alternatively, a new method is developed to investigate 3D nested groundwater flow systems without determination of stagnation points. Connective indices are defined to quantify the connection between individual recharge and discharge zones along streamlines. Groundwater circulation cells (GWCCs) are identified according to the distribution of the connective indices and then grouped into local, intermediate and regional flow systems. This method requires existing solution of the flow velocity vector and is implemented via particle tracking technique. It is applied in a hypothetical 3D Tóthian basin with an analytical solution of the flow field and in a real-world basin with a numerical modeling approach. Different spatial patterns of flow systems compared to 2D profile models are found. The outcrops boundaries of GWCCs on water table may significantly deviate from and are not parallel to the nearby water table divides. Topological network is proposed to represent the linked recharge-discharge zones through closed and open GWCCs. Sensitivity analysis indicates that the development of GWCCs depends on the basin geometry, hydraulic parameters and water table shape.

Regional groundwater flow modeling of the Geba basin, northern Ethiopia

NASA Astrophysics Data System (ADS)

Gebreyohannes, Tesfamichael; De Smedt, Florimond; Walraevens, Kristine; Gebresilassie, Solomon; Hussien, Abdelwassie; Hagos, Miruts; Amare, Kassa; Deckers, Jozef; Gebrehiwot, Kindeya

2017-05-01

The Geba basin is one of the most food-insecure areas of the Tigray regional state in northern Ethiopia due to recurrent drought resulting from erratic distribution of rainfall. Since the beginning of the 1990s, rain-fed agriculture has been supported through small-scale irrigation schemes mainly by surface-water harvesting, but success has been limited. Hence, use of groundwater for irrigation purposes has gained considerable attention. The main purpose of this study is to assess groundwater resources in the Geba basin by means of a MODFLOW modeling approach. The model is calibrated using observed groundwater levels, yielding a clear insight into the groundwater flow systems and reserves. Results show that none of the hydrogeological formations can be considered as aquifers that can be exploited for large-scale groundwater exploitation. However, aquitards can be identified that can support small-scale groundwater abstraction for irrigation needs in regions that are either designated as groundwater discharge areas or where groundwater levels are shallow and can be tapped by hand-dug wells or shallow boreholes.

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

USGS Publications Warehouse

Sepúlveda, 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.

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. © 2014, National Ground Water Association.

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

USGS Publications Warehouse

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

2014-01-01

Full appropriation of tributary streamflow during summer, a growing population, and agricultural needs are increasing the demand for groundwater in the Willamette Basin. Greater groundwater use could diminish streamflow and create seasonal and long-term declines in groundwater levels. The U.S. Geological Survey (USGS) and the Oregon Water Resources Department (OWRD) cooperated in a study to develop a conceptual and quantitative understanding of the groundwater-flow system of the Willamette Basin with an emphasis on the Central Willamette subbasin. This final report from the cooperative study describes numerical models of the regional and local groundwater-flow systems and evaluates the effects of pumping on groundwater and surface‑water resources. The models described in this report can be used to evaluate spatial and temporal effects of pumping on groundwater, base flow, and stream capture. The regional model covers about 6,700 square miles of the 12,000-square mile Willamette and Sandy River drainage basins in northwestern Oregon—referred to as the Willamette Basin in this report. The Willamette Basin is a topographic and structural trough that lies between the Coast Range and the Cascade Range and is divided into five sedimentary subbasins underlain and separated by basalts of the Columbia River Basalt Group (Columbia River basalt) that crop out as local uplands. From north to south, these five subbasins are the Portland subbasin, the Tualatin subbasin, the Central Willamette subbasin, the Stayton subbasin, and the Southern Willamette subbasin. Recharge in the Willamette Basin is primarily from precipitation in the uplands of the Cascade Range, Coast Range, and western Cascades areas. Groundwater moves downward and laterally through sedimentary or basalt units until it discharges locally to wells, evapotranspiration, or streams. Mean annual groundwater withdrawal for water years 1995 and 1996 was about 400 cubic feet per second; irrigation withdrawals

Human impact on regional groundwater composition through intervention in natural flow patterns and changes in land use

NASA Astrophysics Data System (ADS)

Schot, P. P.; van der Wal, J.

1992-06-01

The relations between groundwater composition, land use, soil conditions and flow patterns on a regional scale are studied for the Gooi and Vechtstreek area in the Netherlands. This densely populated area consists of a glacier-created ridge with dry sand soils bordered by the Vecht and Eem River plains with wet peat and clay soils. R-mode factor analysis and Q-mode cluster analysis were applied to a set of 1349 groundwater analyses to determine the factors controlling groundwater composition and the main resulting water types. The results indicate that groundwater composition in the study area is affected on a regional scale by human activities through changes in land use and intervention in natural flow patterns. On the ridge, ground water is recharged by precipitation, which dissolves carbonates from the matrix of the sandy aquifer. Increased solute concentrations in shallow ground water, especially of nitrate, sulphate and potassium, indicate increased pollution resulting from urbanization and increasingly intensive agricultural activity over the past decades. In the Vecht River plain infiltration occurs as a result of drainage of polders and groundwater extraction on the ridge. Recharge occurs by precipitation and from polluted surface water to which ammonium, organic complexes and carbonic acid are added through decomposition of organic matter in the peat and clay soils. The carbonic acid results in enhanced dissolution of carbonates present in the soil and the underlying sandy aquifer. Oxygen depletion and subsequent low redox potentials result in denitrification, dissolution of manganese and iron oxides, and sulphate reduction. The flow of ground water from high-level to low-level polders causes displacement of a former stagnant brakish groundwater body under the Vecht River plain accompanied by increased mixing of fresh and brackish ground water.

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 ...

Numerical simulation of ground-water flow in lower Satus Creek Basin, Yakima Indian Reservation, Washington

USGS Publications Warehouse

Prych, E.A.

1983-01-01

A multilayer numerical model of steady-state ground-water flow in lower Satus Creek basin was constructed, calibrated using time-averaged data, and used to estimate the long-term effects of proposed irrigation-water management plans on ground-water levels in the area. Model computations showed that irrigation of new lands in the Satus uplands would raise ground-water levels in lower Satus Creek basin and thereby increase the size of the waterlogged areas. The model also demonstrated that pumping water from wells, reducing the amount of irrigation water used in the lowlands, and stopping leakage from Satus No. 2 and 3 Pump Canals were all effective methods to alleviate present waterlogging in some parts of the basin and to counteract some of the anticipated ground-water-level rises that would be caused by irrigating the uplands. The proposed changes in water use affected model-computed ground-water levels most in the eastern part of the basin between Satus No. 2 and No. 3 Pump Canals. The effects on ground-water levels in the western part of the basin between Satus Creek and Satus No. 2 Pump Canal were smaller. (USGS)

Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and Canada

USGS Publications Warehouse

Davis, Kyle W.; Long, Andrew J.

2018-05-31

The U.S. Geological Survey developed a groundwater-flow model for the uppermost principal aquifer systems in the Williston Basin in parts of Montana, North Dakota, and South Dakota in the United States and parts of Manitoba and Saskatchewan in Canada as part of a detailed assessment of the groundwater availability in the area. The assessment was done because of the potential for increased demands and stresses on groundwater associated with large-scale energy development in the area. As part of this assessment, a three-dimensional groundwater-flow model was developed as a tool that can be used to simulate how the groundwater-flow system responds to changes in hydrologic stresses at a regional scale.The three-dimensional groundwater-flow model was developed using the U.S. Geological Survey’s numerical finite-difference groundwater model with the Newton-Rhapson solver, MODFLOW–NWT, to represent the glacial, lower Tertiary, and Upper Cretaceous aquifer systems for steady-state (mean) hydrological conditions for 1981‒2005 and for transient (temporally varying) conditions using a combination of a steady-state period for pre-1960 and transient periods for 1961‒2005. The numerical model framework was constructed based on existing and interpreted hydrogeologic and geospatial data and consisted of eight layers. Two layers were used to represent the glacial aquifer system in the model; layer 1 represented the upper one-half and layer 2 represented the lower one-half of the glacial aquifer system. Three layers were used to represent the lower Tertiary aquifer system in the model; layer 3 represented the upper Fort Union aquifer, layer 4 represented the middle Fort Union hydrogeologic unit, and layer 5 represented the lower Fort Union aquifer. Three layers were used to represent the Upper Cretaceous aquifer system in the model; layer 6 represented the upper Hell Creek hydrogeologic unit, layer 7 represented the lower Hell Creek aquifer, and layer 8 represented the Fox

Groundwater monitoring of an open-pit limestone quarry: groundwater characteristics, evolution and their connections to rock slopes.

PubMed

Eang, Khy Eam; Igarashi, Toshifumi; Fujinaga, Ryota; Kondo, Megumi; Tabelin, Carlito Baltazar

2018-03-06

Groundwater flow and its geochemical evolution in mines are important not only in the study of contaminant migration but also in the effective planning of excavation. The effects of groundwater on the stability of rock slopes and other mine constructions especially in limestone quarries are crucial because calcite, the major mineral component of limestone, is moderately soluble in water. In this study, evolution of groundwater in a limestone quarry located in Chichibu city was monitored to understand the geochemical processes occurring within the rock strata of the quarry and changes in the chemistry of groundwater, which suggests zones of deformations that may affect the stability of rock slopes. There are three distinct geological formations in the quarry: limestone layer, interbedded layer of limestone and slaty greenstone, and slaty greenstone layer as basement rock. Although the hydrochemical facies of all groundwater samples were Ca-HCO 3 type water, changes in the geochemical properties of groundwater from the three geological formations were observed. In particular, significant changes in the chemical properties of several groundwater samples along the interbedded layer were observed, which could be attributed to the mixing of groundwater from the limestone and slaty greenstone layers. On the rainy day, the concentrations of Ca 2+ and HCO 3 - in the groundwater fluctuated notably, and the groundwater flowing along the interbedded layer was dominated by groundwater from the limestone layer. These suggest that groundwater along the interbedded layer may affect the stability of rock slopes.

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

Adaptation of the Carter-Tracy water influx calculation to groundwater flow simulation

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. It is a good approximation for constant flow rates but is poor for time-varying flow rates where the variation is large relative to the mean. A variety of outer aquifer region geometries, exterior boundary conditions, and flow rate versus potentiometric head relations can be used. The radial, transient-flow case presented is representative. An analytical approximation to the functions of Van Everdingen and Hurst for the dimensionless potentiometric head versus dimensionless time is given.

General Separations Area (GSA) Groundwater Flow Model Update: Hydrostratigraphic Data

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

Bagwell, L.; Bennett, P.; Flach, G.

2017-02-21

This document describes the assembly, selection, and interpretation of hydrostratigraphic data for input to an updated groundwater flow model for the General Separations Area (GSA; Figure 1) at the Department of Energy’s (DOE) Savannah River Site (SRS). This report is one of several discrete but interrelated tasks that support development of an updated groundwater model (Bagwell and Flach, 2016).

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

Temperature-driven groundwater convection in cold climates

NASA Astrophysics Data System (ADS)

Engström, Maria; Nordell, Bo

2016-08-01

The aim was to study density-driven groundwater flow and analyse groundwater mixing because of seasonal changes in groundwater temperature. Here, density-driven convection in groundwater was studied by numerical simulations in a subarctic climate, i.e. where the water temperature was <4 °C. The effects of soil permeability and groundwater temperature (i.e. viscosity and density) were determined. The influence of impermeable obstacles in otherwise homogeneous ground was also studied. An initial disturbance in the form of a horizontal groundwater flow was necessary to start the convection. Transient solutions describe the development of convective cells in the groundwater and it took 22 days before fully developed convection patterns were formed. The thermal convection reached a maximum depth of 1.0 m in soil of low permeability (2.71 · 10-9 m2). At groundwater temperature close to its density maximum (4 °C), the physical size (in m) of the convection cells was reduced. Small stones or frost lenses in the ground slightly affect the convective flow, while larger obstacles change the size and shape of the convection cells. Performed simulations show that "seasonal groundwater turnover" occurs. This knowledge may be useful in the prevention of nutrient leakage to underlying groundwater from soils, especially in agricultural areas where no natural vertical groundwater flow is evident. An application in northern Sweden is discussed.

Ground-water flow in low permeability environments

USGS Publications Warehouse

Neuzil, Christopher 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 sytems 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 pertroleum 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 measurements of parameters. These limitations have resulted in rather distinct small- and large-scale approaches to the problem. The first part of the review considers experimental investigations of low-permeability flow, including in situ testing; these are generally conducted on temporal and spatial scales which are relatively small compared with those of interest. Results from this work have provided increasingly detailed information about many aspects of the flow but leave certain questions unanswered. Recent advances in laboratory and in situ testing techniques have permitted measurements of permeability and storage properties in progressively “tighter” media and investigation of transient flow under these conditions. However, very large hydraulic gradients are still required for the tests; an observational gap exists for typical in situ gradients. The applicability of Darcy's law in this range is therefore untested, although claims of observed non-Darcian behavior appear flawed. Two important nonhydraulic

Simulation of groundwater flow in the glacial aquifer system of northeastern Wisconsin with variable model complexity

USGS Publications Warehouse

Juckem, Paul F.; Clark, Brian R.; Feinstein, Daniel T.

2017-05-04

The U.S. Geological Survey, National Water-Quality Assessment seeks to map estimated intrinsic susceptibility of the glacial aquifer system of the conterminous United States. Improved understanding of the hydrogeologic characteristics that explain spatial patterns of intrinsic susceptibility, commonly inferred from estimates of groundwater age distributions, is sought so that methods used for the estimation process are properly equipped. An important step beyond identifying relevant hydrogeologic datasets, such as glacial geology maps, is to evaluate how incorporation of these resources into process-based models using differing levels of detail could affect resulting simulations of groundwater age distributions and, thus, estimates of intrinsic susceptibility.This report describes the construction and calibration of three groundwater-flow models of northeastern Wisconsin that were developed with differing levels of complexity to provide a framework for subsequent evaluations of the effects of process-based model complexity on estimations of groundwater age distributions for withdrawal wells and streams. Preliminary assessments, which focused on the effects of model complexity on simulated water levels and base flows in the glacial aquifer system, illustrate that simulation of vertical gradients using multiple model layers improves simulated heads more in low-permeability units than in high-permeability units. Moreover, simulation of heterogeneous hydraulic conductivity fields in coarse-grained and some fine-grained glacial materials produced a larger improvement in simulated water levels in the glacial aquifer system compared with simulation of uniform hydraulic conductivity within zones. The relation between base flows and model complexity was less clear; however, the relation generally seemed to follow a similar pattern as water levels. Although increased model complexity resulted in improved calibrations, future application of the models using simulated particle

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

USGS Publications Warehouse

Sepúlveda, 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.

Hydrology and simulation of ground-water flow, Lake Point, Tooele County, Utah

USGS Publications Warehouse

Brooks, Lynette E.

2006-01-01

Water for new residential development in Lake Point, Utah may be supplied by public-supply wells completed in consolidated rock on the east side of Lake Point. Ground-water flow models were developed to help understand the effect the proposed withdrawal will have on water levels, flowing-well discharge, spring discharge, and ground-water quality in the study area. This report documents the conceptual and numerical ground-water flow models for the Lake Point area.The ground-water system in the Lake Point area receives recharge from local precipitation and irrigation, and from ground-water inflow from southwest of the area. Ground water discharges mostly to springs. Discharge also occurs to evapotranspiration, wells, and Great Salt Lake. Even though ground water discharges to Great Salt Lake, dense salt water from the lake intrudes under the less-dense ground water and forms a salt-water wedge under the valley. This salt water is responsible for some of the high dissolved-solids concentrations measured in ground water in Lake Point.A steady-state MODFLOW-2000 ground-water model of Tooele Valley adequately simulates water levels, ground-water discharge, and ground-water flow direction observed in Lake Point in 1969 and 2002. Simulating an additional 1,650 acre-feet per year withdrawal from wells causes a maximum projected drawdown of about 550 feet in consolidated rock near the simulated wells and drawdown exceeding 80 feet in an area encompassing most of the Oquirrh Mountains east of Lake Point. Drawdown in most of Lake Point ranges from 2 to 10 ft, but increases to more than 40 feet in the areas proposed for residential development. Discharge to Factory Springs, flowing wells, evapotranspiration, and Great Salt Lake is decreased by about 1,100 acre-feet per year (23 percent).The U.S. Geological Survey SUTRA variable-density ground-water-flow model generates a reasonable approximation of 2002 dissolved-solids concentration when simulating 2002 withdrawals. At most

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

NASA Astrophysics Data System (ADS)

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

2009-12-01

Widespread arsenic poisoning is occurring in large areas of Bangladesh and West Bengal, India due to high arsenic levels in shallow groundwater, which is the primary source of irrigation and drinking water in the region. The high-arsenic groundwater exists in aquifers of the Bengal Basin, a huge sedimentary system approximately 500km x 500km wide and greater than 15km deep in places. Deeper groundwater (>150m) is nearly universally low in arsenic and a potential source of safe drinking water, but evaluation of its sustainability requires understanding of the entire, interconnected regional aquifer system. Numerical modeling of flow and arsenic transport in the basin introduces problems of scale: challenges in representing the system in enough detail to produce meaningful simulations and answer relevant questions while maintaining enough simplicity to understand controls on processes and operating within computational constraints. A regional groundwater flow and transport model of the Bengal Basin was constructed to assess the large-scale functioning of the deep groundwater flow system, the vulnerability of deep groundwater to pumping-induced migration from above, and the effect of chemical properties of sediments (sorption) on sustainability. The primary challenges include the very large spatial scale of the system, dynamic monsoonal hydrology (small temporal scale fluctuations), complex sedimentary architecture (small spatial scale heterogeneity), and a lack of reliable hydrologic and geologic data. The approach was simple. Detailed inputs were reduced to only those that affect the functioning of the deep flow system. Available data were used to estimate upscaled parameter values. Nested small-scale simulations were performed to determine the effects of the simplifications, which include treatment of the top boundary condition and transience, effects of small-scale heterogeneity, and effects of individual pumping wells. Simulation of arsenic transport at the large

A hydrogeologic approach to identify land uses that overlie ground-water flow paths, Broward County, Florida

USGS Publications Warehouse

Sonenshein, R.S.

1995-01-01

A hydrogeologic approach that integrates the use of hydrogeologic and spatial tools aids in the identification of land uses that overlie ground- water flow paths and permits a better understanding of ground-water flow systems. A mathematical model was used to simulate the ground-water flow system in Broward County, particle-tracking software was used to determine flow paths leading to the monitor wells in Broward County, and a Geographic Information System was used to identify which land uses overlie the flow paths. A procedure using a geographic information system to evaluate the output from a ground-water flow model has been documented. The ground-water flow model was used to represent steady-state conditions during selected wet- and dry-season months, and an advective flow particle- tracking program was used to simulate the direction of ground-water flow in the aquifer system. Digital spatial data layers were created from the particle pathlines that lead to the vicinity of the open interval of selected wells in the Broward County ground-water quality monitoring network. Buffer zone data layers were created, surrounding the particle pathlines to represent the area of contribution to the water sampled from the monitor wells. Spatial data layers, combined with a land-use data layer, were used to identify the land uses that overlie the ground-water flow paths leading to the monitor wells. The simulation analysis was performed on five Broward County wells with different hydraulic parameters to determine the source of ground-water stress, determine selected particle pathlines, and identify land use in buffer zones in the vicinity of the wells. The flow paths that lead to the grid cells containing wells G-2355, G-2373, and G-2373A did not vary between the wet- and dry-season conditions. Changes in the area of contribution for wells G-2345X and G-2369 were attributed to variations in rainfall patterns, well-field pumpage, and surface-water management practices

Simulation of ground-water flow in the Mojave River basin, California

USGS Publications Warehouse

Stamos, Christina L.; Martin, Peter; Nishikawa, Tracy; Cox, Brett F.

2001-01-01

The proximity of the Mojave River ground-water basin to the highly urbanized Los Angeles region has led to rapid growth in population and, consequently, to an increase in the demand for water. The Mojave River, the primary source of surface water for the region, normally is dry-except for a small stretch of perennial flow and periods of flow after intense storms. Thus, the region relies almost entirely on ground water to meet its agricultural and municipal needs. Ground-water withdrawal since the late 1800's has resulted in discharge, primarily from pumping wells, that exceeds natural recharge. To better understand the relation between the regional and the floodplain aquifer systems and to develop a management tool that could be used to estimate the effects that future stresses may have on the ground-water system, a numerical ground-water flow model of the Mojave River ground-water basin was developed, in part, on the basis of a previously developed analog model. The ground-water flow model has two horizontal layers; the top layer (layer 1) corresponds to the floodplain aquifer and the bottom layer (layer 2) corresponds to the regional aquifer. There are 161 rows and 200 columns with a horizontal grid spacing of 2,000 by 2,000 feet. Two stress periods (wet and dry) per year are used where the duration of each stress period is a function of the occurrence, quantity of discharge, and length of stormflow from the headwaters each year. A steady-state model provided initial conditions for the transient-state simulation. The model was calibrated to transient-state conditions (1931-94) using a trial-and-error approach. The transient-state simulation results are in good agreement with measured data. Under transient-state conditions, the simulated floodplain aquifer and regional aquifer hydrographs matched the general trends observed for the measured water levels. The simulated streamflow hydrographs matched wet stress period average flow rates and times of no flow at the

A high-resolution global-scale groundwater model

NASA Astrophysics Data System (ADS)

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

2015-02-01

Groundwater is the world's largest accessible source of fresh water. It plays a vital role in satisfying basic needs for drinking water, agriculture and industrial activities. During times of drought groundwater sustains baseflow to rivers and wetlands, thereby supporting ecosystems. Most global-scale hydrological models (GHMs) do not include a groundwater flow component, mainly due to lack of geohydrological data at the global scale. For the simulation of lateral flow and groundwater head dynamics, a realistic physical representation of the groundwater system is needed, especially for GHMs that run at finer resolutions. In this study we present a global-scale groundwater model (run at 6' resolution) using MODFLOW to construct an equilibrium water table at its natural state as the result of long-term climatic forcing. The used aquifer schematization and properties are based on available global data sets of lithology and transmissivities combined with the estimated thickness of an upper, unconfined aquifer. This model is forced with outputs from the land-surface PCRaster Global Water Balance (PCR-GLOBWB) model, specifically net recharge and surface water levels. A sensitivity analysis, in which the model was run with various parameter settings, showed that variation in saturated conductivity has the largest impact on the groundwater levels simulated. Validation with observed groundwater heads showed that groundwater heads are reasonably well simulated for many regions of the world, especially for sediment basins (R2 = 0.95). The simulated regional-scale groundwater patterns and flow paths demonstrate the relevance of lateral groundwater flow in GHMs. Inter-basin groundwater flows can be a significant part of a basin's water budget and help to sustain river baseflows, especially during droughts. Also, water availability of larger aquifer systems can be positively affected by additional recharge from inter-basin groundwater flows.

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.

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.

Hydrogeology, groundwater flow, and groundwater quality of an abandoned underground coal-mine aquifer, Elkhorn Area, West Virginia

USGS Publications Warehouse

Kozar, Mark D.; McCoy, Kurt J.; Britton, James Q.; Blake, B.M.

2017-01-01

The Pocahontas No. 3 coal seam in southern West Virginia has been extensively mined by underground methods since the 1880’s. An extensive network of abandoned mine entries in the Pocahontas No. 3 has since filled with good-quality water, which is pumped from wells or springs discharging from mine portals (adits), and used as a source of water for public supplies. This report presents results of a three-year investigation of the geology, hydrology, geochemistry, and groundwater flow processes within abandoned underground coal mines used as a source of water for public supply in the Elkhorn area, McDowell County, West Virginia. This study focused on large (> 500 gallon per minute) discharges from the abandoned mines used as public supplies near Elkhorn, West Virginia. Median recharge calculated from base-flow recession of streamflow at Johns Knob Branch and 12 other streamflow gaging stations in McDowell County was 9.1 inches per year. Using drainage area versus mean streamflow relationships from mined and unmined watersheds in McDowell County, the subsurface area along dip of the Pocahontas No. 3 coal-mine aquifer contributing flow to the Turkey Gap mine discharge was determined to be 7.62 square miles (mi2), almost 10 times larger than the 0.81 mi2 surface watershed. Results of this investigation indicate that groundwater flows down dip beneath surface drainage divides from areas up to six miles east in the adjacent Bluestone River watershed. A conceptual model was developed that consisted of a stacked sequence of perched aquifers, controlled by stress-relief and subsidence fractures, overlying a highly permeable abandoned underground coal-mine aquifer, capable of substantial interbasin transfer of water. Groundwater-flow directions are controlled by the dip of the Pocahontas No. 3 coal seam, the geometry of abandoned mine workings, and location of unmined barriers within that seam, rather than surface topography. Seven boreholes were drilled to intersect

Renewable and Sustainable Study of Groundwater Flow System based on Numerical Simulation in Qaidam Basin, China

NASA Astrophysics Data System (ADS)

Cui, Y.

2015-12-01

In order to study surface water and groundwater exchange and renewal capacity of groundwater system of Qaidam Basin, inland northwest China, TOUGH2 (Transport of Unsaturated Groundwater and Heat 2) simulation software was used to establish a two-dimensional variable saturated numerical model of a typical cross-section from the Nuomuhong river to the Amunike mountain. According to previous results, evaporation is a function of soil saturation given as an upper boundary to characterize water transport near surface through iterative calculation. Parameters were calibrated with 52 groundwater observation data by trial-and-error method. Particle tracking and isotopic dating results were combined to simulate groundwater age and calibrate models. The results showed that the typical profile of Qaidam basin can be divided into three lumped groundwater flow systems: (1) The circulation depth (CD) of local groundwater flow system is about 200m, where discharge in this lumped system accounts for 74.4% of the total amount of discharge (TAD), of which spring overflow constitutes large fraction. Groundwater age is generally less than 500 years and renewal rate is 1.13% a-1; (2) The CD of middle flow system can reach 800m, where it takes up 18.5% of TAD, evaporation and river overflows is the main outlet of discharge. Groundwater age is generally less than 10ka and renewal rate is 0.094% a-1; (3) The CD of regional flow system is from 1000 to 1500m. It accounts for 7.1% of TAD, of which evaporation is the largest component. Groundwater age is from 10ka to 50ka and renewal rate of which is 0.0074% a-1. Sulingguole river is the discharge area of regional groundwater system, the age of which is greater than 30ka. The method used here can obtain the renewal capacity of groundwater system and better reflect regional circulation characteristics, which have certain significance for the urgent study of regional groundwater circulation and flow systems in areas with limited available data.

Assessing Groundwater Resources Sustainability Using Groundwater Footprint Concept

NASA Astrophysics Data System (ADS)

Charchousi, Despoina; Spanoudaki, Katerina; Papadopoulou, Maria P.

2017-04-01

Over-pumping, water table depletion and climate change impacts require effective groundwater management. The Groundwater Footprint (GWF), introduced by Gleeson et al. in 2012 expresses the area required to sustain groundwater use and groundwater dependent ecosystem services. GWF represents a water balance between aquifer inflows and outflows, focusing on environmental flow requirements. Developing the water balance, precipitation recharge and additional recharge from irrigation are considered as inflows, whereas outflows are considered the groundwater abstraction from the aquifer of interest and the quantity of groundwater that is needed to sustain ecosystem services. The parameters required for GWF calculation can be estimated through in-situ measurements, observations and models outputs. The actual groundwater abstraction is often difficult to be estimated with a high accuracy. Environmental flow requirements can be calculated through different approaches; the most accurate of which are considered the ones that focus on hydro-ecological data analysis. As the GWF is a tool recently introduced in groundwater assessment and management, only a few studies have been reported in the literature to use it as groundwater monitoring and management tool. The present study emphasizes on a case study in Southern Europe, where awareness should be raised about rivers' environmental flow. GWF concept will be applied for the first time to a pilot area in Greece, where the flow of the perennial river that crosses the area of interest is dependent on baseflow. Recharge and abstraction of the pilot area are estimated based on historical data and previous reports and a groundwater flow model is developed using Visual Modflow so as to diminish the uncertainty of the input parameters through model calibration. The groundwater quantity that should be allocated on surface water body in order to sustain satisfactory biological conditions is estimated under the assumption that surface

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

USGS Publications Warehouse

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

2012-01-01

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

Geohydrology and simulated ground-water flow in an irrigated area of northwestern Indiana

USGS Publications Warehouse

Arihood, L.D.; Basch, M.E.

1994-01-01

Water for irrigation in parts of Newton and Jasper Counties and adjacent areas of northwestern Indiana is pumped mostly from the carbonate- bedrock aquifer that underlies glacial drift. To help in managing the ground-water resources of the area, a three-dimensional ground-water model was developed and tested with hydrologic data collected during 1986 and 1988. Two major aquifers and a confining unit were identified. The surficial unconfined outwash aquifer consists of sand and some gravel. Saturated thickness averages about 30 feet. Estimated values of horizontal hydraulic conductivity and storage coefficient are 350 feet per day and 0.07, respectively. The generally continuous confining unit beneath the outwash aquifer is composed predominantly of till and lacustrine silt and clay and is 0 to 125 feet thick. The carbonate-bedrock aquifer is composed of Silurian and Devonian dolomitic limestone; dolomite and has a median transmissivity of 2,000 feet squared per day. A nine-layer digital model was developed to simulate flow in the ground-water system. The mean absolute errors for simulated water levels in the bedrock aquifer ranged from 5 to 7 feet for two recent periods of irrigation. The component of the flow system that most affects water-level drawdowns in the bedrock aquifer is the confining unit which controls the rate of leakage to the bedrock aquifer. The model is most accurate in areas for which data for confining-unit thickness and bedrock water levels are available.

Ground-water flow in the New Jersey Coastal Plain

USGS Publications Warehouse

Martin, Mary

1998-01-01

Ground-water flow in 10 aquifers and 9 intervening confining units of the New Jersey Coastal Plain was simulated as part of the Regional Aquifer System Analysis. Data on aquifer and confining unit characteristics and on pumpage and water levels from 1918 through 1980 were incorporated into a multilayer finite-difference model. The report describes the conceptual hydrogeologic model of the unstressed flow systems, the methods and approach used in simulating flow, and the results of the simulations.

The use of simulation and multiple environmental tracers to quantify groundwater flow in a shallow aquifer

USGS Publications Warehouse

Reilly, Thomas E.; Plummer, Niel; Phillips, Patrick J.; Busenberg, Eurybiades

1994-01-01

Measurements of the concentrations of chlorofluorocarbons (CFCs), tritium, and other environmental tracers can be used to calculate recharge ages of shallow groundwater and estimate rates of groundwater movement. Numerical simulation also provides quantitative estimates of flow rates, flow paths, and mixing properties of the groundwater system. The environmental tracer techniques and the hydraulic analyses each contribute to the understanding and quantification of the flow of shallow groundwater. However, when combined, the two methods provide feedback that improves the quantification of the flow system and provides insight into the processes that are the most uncertain. A case study near Locust Grove, Maryland, is used to investigate the utility of combining groundwater age dating, based on CFCs and tritium, and hydraulic analyses using numerical simulation techniques. The results of the feedback between an advective transport model and the estimates of groundwater ages determined by the CFCs improve a quantitative description of the system by refining the system conceptualization and estimating system parameters. The plausible system developed with this feedback between the advective flow model and the CFC ages is further tested using a solute transport simulation to reproduce the observed tritium distribution in the groundwater. The solute transport simulation corroborates the plausible system developed and also indicates that, for the system under investigation with the data obtained from 0.9-m-long (3-foot-long) well screens, the hydrodynamic dispersion is negligible. Together the two methods enable a coherent explanation of the flow paths and rates of movement while indicating weaknesses in the understanding of the system that will require future data collection and conceptual refinement of the groundwater system.

Simulation of ground-water flow in the Cedar River alluvial aquifer flow system, Cedar Rapids, Iowa

USGS Publications Warehouse

Turco, Michael J.; Buchmiller, Robert C.

2004-01-01

Model results indicate that the primary sources of inflow to the modeled area are infiltration from the Cedar River (53.0 percent) and regional flow in the glacial and bedrock materials (34.1 percent). The primary sources of outflow from the modeled area are discharge to the Cedar River (45.4 percent) and pumpage (44.8 percent). Current steady-state pumping rates have increased the flow of water from the Cedar River to the alluvial aquifer by 43.8 cubic feet per second. Steady-state and transient hypothetical pumpage scenarios were used to show the relation between changes in pumpage and changes in infiltration of water from the Cedar River. Results indicate that more than 99 percent of the water discharging from municipal wells infiltrates from the Cedar River, that the time required for induced river recharge to equilibrate with municipal pumpage may be 150 days or more, and that ground-water availability in the Cedar Rapids area will not be significantly affected by doubling current pumpage as long as there is sufficient flow in the Cedar River to provide recharge.

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

Investigation of Arsenotrophic Microbiome in Arsenic-Affected Bangladesh Groundwater.

PubMed

Sultana, Munawar; Mou, Taslin Jahan; Sanyal, Santonu Kumar; Diba, Farzana; Mahmud, Zahid Hayat; Parvez, Anowar Khasru; Hossain, M Anwar

2017-09-01

Arsenotrophic bacteria contribute to the nutrient cycling in arsenic (As) affected groundwater. This study employed a culture-independent and -dependent investigation of arsenotrophic microbiomes in As affected groundwater samples collected from Madhabpur, Sonatengra, and Union Porishod in Singair Upazila, Manikganj, Bangladesh. Total As contents, detected by Atomic Absorption Spectrophotometry (AAS) of the samples, were 47 µg/L (Madhabpur, SNGW-1), 53 µg/L (Sonatengra, SNGW-2), and 12 µg/L (Union porishod, SNGW-3), whereas the control well (SNGW-4; depths >150 m) showed As content of 6 µg/L. Denaturing Gradient Gel Electrophoresis (DGGE) analysis of the amplified 16S rRNA gene from As-affected groundwater samples revealed the dominance of aerobic bacteria Pseudomonas within heterogeneous bacterial populations. DGGE of heterotrophic enrichments supplemented with arsenite [As (III)] for 4 weeks showed the dominance of Chryseobacterium, Flavobacterium, and Aquabacterium, whereas the dominant genera in that of autotrophic enrichments were Aeromonas, Acinetobacter, and Pseudomonas. Cultured bacteria retrieved from both autotrophic and heterotrophic enrichments were distinguished into nine genotypes belonging to Chryseobacterium, Acinetobacter, Escherichia, Pseudomonas, Stenotrophomonas, Janibacter, Staphylococcus, and Bacillus. They exhibited varying range of As(III) tolerance from 4 to 27 mM. As(III) transformation potential was confirmed within the isolates with oxidation rate as high as 0.143 mM/h for Pseudomonas sp. Sn 28. The arsenotrophic microbiome specifies their potential role in groundwater As-cycling and their genetic information provide the scientific basis for As-bioremediation. © 2017, National Ground Water Association.

Comparison of Sap Flow- and White's Equation-Based Estimates of Groundwater Evapotranspiration

NASA Astrophysics Data System (ADS)

Widdowson, M.; Harding, B.

2017-12-01

Estimates of evapotranspiration (ET) of groundwater are useful at sites where phytoremediation is a component of the remedial strategy and the management of contaminant plumes. Methods to quantify direct ET of groundwater rely on multiple lines of evidence but are often limited to the measurement of water table levels and analysis of diurnal trends (e.g., White's Equation and related derivative methods). In this study, sap flow was collected and combined with monitoring of groundwater levels during the entire growing season at a site located in the Atlantic Coastal Plain (Georgia, USA). Our objective was to quantify temporal variations in estimates of groundwater ET in a phytoremediation test plot consisting of approximately 370 trees at a creosote-contaminated source zone. Trees ranging from 8-cm to 9-cm in diameter were instrumented with thermal dissipation sap velocity probes connected to a recording data logger. Wells and piezometers screened across the water table located within and around the periphery of the stand of trees were instrumented with recording pressure transducers. Sap flow estimates using the Granier method varied from 1 to 3 L/d per tree in dry months to 1 to 15 L/d per tree during periods of frequent precipitation and high ET potential. Results show no clear or consistent relationship between estimates of groundwater ET derived from water table fluctuations and sap flow results during the entire period of performance. However, this approach provides an upper and lower bound of groundwater consumption and concomitant plant uptake of light-weight polycyclic aromatic hydrocarbons.

Hydrogeology and simulation of groundwater flow in the Arbuckle-Simpson aquifer, south-central Oklahoma

USGS Publications Warehouse

Christenson, Scott; Osborn, Noel I.; Neel, Christopher R.; Faith, Jason R.; Blome, Charles D.; Puckette, James; Pantea, Michael P.

2011-01-01

Groundwater in the aquifer moves from areas of high head (altitude) to areas of low head along streams and springs. The potentiometric surface in the eastern Arbuckle-Simpson aquifer generally slopes from a topographic high from northwest to the southeast, indicating that regional groundwater flow is predominantly toward the southeast. Freshwater is known to extend beyond the aquifer outcrop near the City of Sulphur, Oklahoma, and Chickasaw National Recreation Area, where groundwater flows west from the outcrop of the eastern Arbuckle-Simpson aquifer and becomes confin

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, David 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.

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

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

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

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

Documentation of a finite-element two-layer model for simulation of ground-water flow

USGS Publications Warehouse

Mallory, Michael J.

1979-01-01

This report documents a finite-element model for simulation of ground-water flow in a two-aquifer system where the two aquifers are coupled by a leakage term that represents flow through a confining layer separating the two aquifers. The model was developed by Timothy J. Durbin (U.S. Geological Survey) for use in ground-water investigations in southern California. The documentation assumes that the reader is familiar with the physics of ground-water flow, numerical methods of solving partial-differential equations, and the FORTRAN IV computer language. It was prepared as part of the investigations made by the U.S. Geological Survey in cooperation with the San Bernardino Valley Municipal Water District. (Kosco-USGS)

Groundwater and surface-water interaction, water quality, and processes affecting loads of dissolved solids, selenium, and uranium in Fountain Creek near Pueblo, Colorado, 2012–2014

USGS Publications Warehouse

Arnold, L. Rick; Ortiz, Roderick F.; Brown, Christopher R.; Watts, Kenneth R.

2016-11-28

In 2012, the U.S. Geological Survey, in cooperation with the Arkansas River Basin Regional Resource Planning Group, initiated a study of groundwater and surface-water interaction, water quality, and loading of dissolved solids, selenium, and uranium to Fountain Creek near Pueblo, Colorado, to improve understanding of sources and processes affecting loading of these constituents to streams in the Arkansas River Basin. Fourteen monitoring wells were installed in a series of three transects across Fountain Creek near Pueblo, and temporary streamgages were established at each transect to facilitate data collection for the study. Groundwater and surface-water interaction was characterized by using hydrogeologic mapping, groundwater and stream-surface levels, groundwater and stream temperatures, vertical hydraulic-head gradients and ratios of oxygen and hydrogen isotopes in the hyporheic zone, and streamflow mass-balance measurements. Water quality was characterized by collecting periodic samples from groundwater, surface water, and the hyporheic zone for analysis of dissolved solids, selenium, uranium, and other selected constituents and by evaluating the oxidation-reduction condition for each groundwater sample under different hydrologic conditions throughout the study period. Groundwater loads to Fountain Creek and in-stream loads were computed for the study area, and processes affecting loads of dissolved solids, selenium, and uranium were evaluated on the basis of geology, geochemical conditions, land and water use, and evapoconcentration.During the study period, the groundwater-flow system generally contributed flow to Fountain Creek and its hyporheic zone (as a single system) except for the reach between the north and middle transects. However, the direction of flow between the stream, the hyporheic zone, and the near-stream aquifer was variable in response to streamflow and stage. During periods of low streamflow, Fountain Creek generally gained flow from

Model Refinement and Simulation of Groundwater Flow in Clinton, Eaton, and Ingham Counties, Michigan

USGS Publications Warehouse

Luukkonen, Carol L.

2010-01-01

A groundwater-flow model that was constructed in 1996 of the Saginaw aquifer was refined to better represent the regional hydrologic system in the Tri-County region, which consists of Clinton, Eaton, and Ingham Counties, Michigan. With increasing demand for groundwater, the need to manage withdrawals from the Saginaw aquifer has become more important, and the 1996 model could not adequately address issues of water quality and quantity. An updated model was needed to better address potential effects of drought, locally high water demands, reduction of recharge by impervious surfaces, and issues affecting water quality, such as contaminant sources, on water resources and the selection of pumping rates and locations. The refinement of the groundwater-flow model allows simulations to address these issues of water quantity and quality and provides communities with a tool that will enable them to better plan for expansion and protection of their groundwater-supply systems. Model refinement included representation of the system under steady-state and transient conditions, adjustments to the estimated regional groundwater-recharge rates to account for both temporal and spatial differences, adjustments to the representation and hydraulic characteristics of the glacial deposits and Saginaw Formation, and updates to groundwater-withdrawal rates to reflect changes from the early 1900s to 2005. Simulations included steady-state conditions (in which stresses remained constant and changes in storage were not included) and transient conditions (in which stresses changed in annual and monthly time scales and changes in storage within the system were included). These simulations included investigation of the potential effects of reduced recharge due to impervious areas or to low-rainfall/drought conditions, delineation of contributing areas with recent pumping rates, and optimization of pumping subject to various quantity and quality constraints. Simulation results indicate

Geohydrology, simulation of ground-water flow, and ground-water quality at two landfills, Marion County, Indiana

USGS Publications Warehouse

Duwelius, R.F.; Greeman, T.K.

1989-01-01

Concentrations of dissolved inorganic substances in ground-water samples indicate that leachate from both landfills is reaching the shallow aquifers. The effect on deeper aquifers is small because of the predominance of horizontal ground-water flow and discharge to the streams. Increases in almost all dissolved constituents were observed in shallow wells that are screened beneath and downgradient from the landfills. Several analyses, especially those for bromide, dissolved solids, and ammonia, were useful in delineating the plume of leachate at both landfills.

Coastal groundwater discharge for the U.S. East and Gulf Coasts calculated with three-dimensional groundwater flow models

NASA Astrophysics Data System (ADS)

Befus, K. M.; Kroeger, K. D.; Smith, C. G.; Swarzenski, P. W.

2017-12-01

Fresh groundwater discharge to coastal environments contribute to the physical and chemical conditions of coastal waters. At regional scales, groundwater fluxes remain poorly constrained, representing uncertainty in both water and chemical budgets that have implications for downstream ecosystem health and for how human activities alter coastal hydrologic processes. Coastal groundwater discharges remain widely unconstrained due to the interconnectedness of highly heterogeneous hydrogeologic frameworks and hydrologic conditions. We use regional-scale, three-dimensional groundwater flow models with the best available hydrostratigraphic framework data to calculate the magnitude of groundwater discharging from coastal aquifers to coastal waterbodies along the eastern U.S. In addition, we constrain the inland areas that contribute to coastal groundwater discharges using particle tracking. We find that 27 km3/yr of groundwater enters coastal waters of the eastern U.S. and Gulf of Mexico and was over 175,000 km2. The contributing areas to coastal groundwater discharge extended kilometers inland and often were supplied by recharge occurring tens of kilometers inland. These results suggest that coastal groundwater discharges rely on larger contributing areas and potentially transport more dissolved constituents than previously calculated, which are important factors for constraining the role of groundwater in coastal chemical budgets and its impacts on coastal ecosystems.

A regional groundwater-flow model for sustainable groundwater-resource management in the south Asian megacity of Dhaka, Bangladesh

NASA Astrophysics Data System (ADS)

Islam, Md Bayzidul; Firoz, A. B. M.; Foglia, Laura; Marandi, Andres; Khan, Abidur Rahman; Schüth, Christoph; Ribbe, Lars

2017-05-01

The water resources that supply most of the megacities in the world are under increased pressure because of land transformation, population growth, rapid urbanization, and climate-change impacts. Dhaka, in Bangladesh, is one of the largest of 22 growing megacities in the world, and it depends on mainly groundwater for all kinds of water needs. The regional groundwater-flow model MODFLOW-2005 was used to simulate the interaction between aquifers and rivers in steady-state and transient conditions during the period 1981-2013, to assess the impact of development and climate change on the regional groundwater resources. Detailed hydro-stratigraphic units are described according to 150 lithology logs, and a three-dimensional model of the upper 400 m of the Greater Dhaka area was constructed. The results explain how the total abstraction (2.9 million m3/d) in the Dhaka megacity, which has caused regional cones of depression, is balanced by recharge and induced river leakage. The simulated outcome shows the general trend of groundwater flow in the sedimentary Holocene aquifers under a variety of hydrogeological conditions, which will assist in the future development of a rational and sustainable management approach.

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. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

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

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.

A Semi-Analytical Solution to Time Dependent Groundwater Flow Equation Incorporating Stream-Wetland-Aquifer Interactions

NASA Astrophysics Data System (ADS)

Boyraz, Uǧur; Melek Kazezyılmaz-Alhan, Cevza

2017-04-01

Groundwater is a vital element of hydrologic cycle and the analytical & numerical solutions of different forms of groundwater flow equations play an important role in understanding the hydrological behavior of subsurface water. The interaction between groundwater and surface water bodies can be determined using these solutions. In this study, new hypothetical approaches are implemented to groundwater flow system in order to contribute to the studies on surface water/groundwater interactions. A time dependent problem is considered in a 2-dimensional stream-wetland-aquifer system. The sloped stream boundary is used to represent the interaction between stream and aquifer. The rest of the aquifer boundaries are assumed as no-flux boundary. In addition, a wetland is considered as a surface water body which lies over the whole aquifer. The effect of the interaction between the wetland and the aquifer is taken into account with a source/sink term in the groundwater flow equation and the interaction flow is calculated by using Darcy's approach. A semi-analytical solution is developed for the 2-dimensional groundwater flow equation in 5 steps. First, Laplace and Fourier cosine transforms are employed to obtain the general solution in Fourier and Laplace domain. Then, the initial and boundary conditions are applied to obtain the particular solution. Finally, inverse Fourier transform is carried out analytically and inverse Laplace transform is carried out numerically to obtain the final solution in space and time domain, respectively. In order to verify the semi-analytical solution, an explicit finite difference algorithm is developed and analytical and numerical solutions are compared for synthetic examples. The comparison of the analytical and numerical solutions shows that the analytical solution gives accurate results.

Subsurface thermal regime to delineate the paleo-groundwater flow system in an arid area, Al Kufra, Libya

NASA Astrophysics Data System (ADS)

Salem, Zenhom El-Said

2016-12-01

The purpose of this study was to understand the groundwater flow system in Al Kufra basin, Libya, as a case study of arid areas using subsurface temperature. The temperature-depth profiles and water levels were measured in eight boreholes in the area. Well 6 is considered a recharge type profile with low geothermal gradient (0.0068 °C/m) and an estimated paleo-temperature around 19.5 °C. The other profiles are of discharge type with higher geothermal gradient (0.0133 to 0.0166 °C/m). The constructed horizontal 2D distribution maps of the hydraulic heads and the subsurface temperature measurements reveal that the main recharge area is located to the south with low temperature while the main discharge area is located to the north with higher temperature. Vertical 2D distribution maps show that location of well 4 has low hydraulic heads and higher temperature indicating that the fault defined in the area may have affected the groundwater flow system. The estimated groundwater flux ranges from 0.001 to 0.1 mm/day for the recharge area and from -0.3 to -0.7 mm/day in average in the discharge area.

Regional groundwater-flow model of the Lake Michigan Basin in support of Great Lakes Basin water availability and use studies

USGS Publications Warehouse

Feinstein, D.T.; Hunt, R.J.; Reeves, H.W.

2010-01-01

. Lastly, it describes several categories of limitations and discusses ways of extending the regional model to address issues at the local scale. Results of the simulations portray a regional groundwater-flow system that, over time, has largely maintained its natural predevelopment configuration but that locally has been strongly affected by well withdrawals. The quantity of rainfall in the Lake Michigan Basin and adjacent areas supports a dense surface-water network and recharge rates consistent with generally shallow water tables and predominantly shallow groundwater flow. At the regional scale, pumping has not caused major modifications of the shallow flow system, but it has resulted in decreases in base flow to streams and in direct discharge to Lake Michigan (about 2 percent of the groundwater discharged and about 0.5 cubic foot per second per mile of shoreline). On the other hand, well withdrawals have caused major reversals in regional flow patterns around pumping centers in deep, confined aquifers - most noticeably in the Cambrian-Ordovician aquifer system on the west side of Lake Michigan near the cities of Green Bay and Milwaukee in eastern Wisconsin, and around Chicago in northeastern Illinois, as well as in some shallow bedrock aquifers (for example, in the Marshall aquifer near Lansing, Mich.). The reversals in flow have been accompanied by large drawdowns with consequent local decrease in storage. On the west side of Lake Michigan, groundwater withdrawals have caused appreciable migration of the deep groundwater divides. Before the advent of pumping, the deep Lake Michigan groundwater-basin boundaries extended west of the Lake Michigan surface-water basin boundary, in some places by tens of miles. Over time, the pumping centers have replaced Lake Michigan as the regional sink for the deep flow system. The regional model is intended to support the framework pilot study of water availability and use for the Great Lakes Basin (Reeves, in press).

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.

Resolving hyporheic and groundwater components of streambed water flux

USGS Publications Warehouse

Bhaskar, Aditi S.; Harvey, Judson W.; Henry, Eric J.

2012-01-01

Hyporheic and groundwater fluxes typically occur together in permeable sediments beneath flowing stream water. However, streambed water fluxes quantified using the thermal method are usually interpreted as representing either groundwater or hyporheic fluxes. Our purpose was to improve understanding of co-occurring groundwater and hyporheic fluxes using streambed temperature measurements and analysis of one-dimensional heat transport in shallow streambeds. First, we examined how changes in hyporheic and groundwater fluxes affect their relative magnitudes by reevaluating previously published simulations. These indicated that flux magnitudes are largely independent until a threshold is crossed, past which hyporheic fluxes are diminished by much larger (1000-fold) groundwater fluxes. We tested accurate quantification of co-occurring fluxes using one-dimensional approaches that are appropriate for analyzing streambed temperature data collected at field sites. The thermal analytical method, which uses an analytical solution to the one-dimensional heat transport equation, was used to analyze results from a numerical heat transport model, in which hyporheic flow was represented as increased thermal dispersion at shallow depths. We found that co-occurring groundwater and hyporheic fluxes can be quantified in streambeds, although not always accurately. For example, using a temperature time series collected in a sandy streambed, we found that hyporheic and groundwater flow could both be detected when thermal dispersion due to hyporheic flow was significant compared to thermal conduction. We provide guidance for when thermal data can be used to quantify both hyporheic and groundwater fluxes, and we show that neglecting thermal dispersion may affect accuracy and interpretation of estimated streambed water fluxes.

Effects of Sea Level Rise on Groundwater Flow Paths in a Coastal Aquifer System

NASA Astrophysics Data System (ADS)

Morrissey, S. K.; Clark, J. F.; Bennett, M. W.; Richardson, E.; Stute, M.

2008-05-01

Changes in groundwater flow in the Floridan aquifer system, South Florida, from the rise in sea level at the end of the last glacial period may be indicative of changes coastal aquifers will experience with continued sea level rise. As sea level rises, the hydraulic head near the coast increases. Coastal aquifers can therefore experience decreased groundwater gradients (increased residence times) and seawater intrusion. Stable isotopes of water, dissolved noble gas temperatures, radiocarbon and He concentrations were analyzed in water collected from 68 wells in the Floridan aquifer system throughout South Florida. Near the recharge area, geochemical data along groundwater flow paths in the Upper Floridan aquifer show a transition from recently recharged groundwater to glacial-aged water. Down gradient from this transition, little variation is apparent in the stable isotopes and noble gas recharge temperatures, indicating that most of the Upper Floridan aquifer contains groundwater recharged during the last glacial period. The rapid 120-meter rise in sea level marking the end of the last glacial period increased the hydraulic head in the Floridan aquifer system near the coast, slowing the flow of groundwater from the recharge area to the ocean and trapping glacial-aged groundwater. The raised sea level also flooded half of the Florida platform and caused seawater to intrude into the Lower Floridan. This circulation of seawater in the Lower Floridan continues today as our data indicate that the groundwater is similar to modern seawater with a freshwater component entering vertically from the recharge area to the Upper Floridan.

Simulation of the regional groundwater-flow system of the Menominee Indian Reservation, Wisconsin

USGS Publications Warehouse

Juckem, Paul F.; Dunning, Charles P.

2015-01-01

The likely extent of the Neopit wastewater plume was simulated by using the groundwater-flow model and Monte Carlo techniques to evaluate the sensitivity of predictive simulations to a range of model parameter values. Wastewater infiltrated from the currently operating lagoons flows predominantly south toward Tourtillotte Creek. Some of the infiltrated wastewater is simulated as having a low probability of flowing beneath Tourtillotte Creek to the nearby West Branch Wolf River. Results for the probable extent of the wastewater plume are considered to be qualitative because the method only considers advective flow and does not account for processes affecting contaminant transport in porous media. Therefore, results for the probable extent of the wastewater plume are sensitive to the number of particles used to represent flow from the lagoon and the resolution of a synthetic grid used for the analysis. Nonetheless, it is expected that the qualitative results may be of use for identifying potential downgradient areas of concern that can then be evaluated using the quantitative “area contributing recharge to wells” method or traditional contaminant-transport simulations.

GSFLOW - Coupled Ground-Water and Surface-Water Flow Model Based on the Integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005)

USGS Publications Warehouse

Markstrom, Steven L.; Niswonger, Richard G.; Regan, R. Steven; Prudic, David E.; Barlow, Paul M.

2008-01-01

The need to assess the effects of variability in climate, biota, geology, and human activities on water availability and flow requires the development of models that couple two or more components of the hydrologic cycle. An integrated hydrologic model called GSFLOW (Ground-water and Surface-water FLOW) was developed to simulate coupled ground-water and surface-water resources. The new model is based on the integration of the U.S. Geological Survey Precipitation-Runoff Modeling System (PRMS) and the U.S. Geological Survey Modular Ground-Water Flow Model (MODFLOW). Additional model components were developed, and existing components were modified, to facilitate integration of the models. Methods were developed to route flow among the PRMS Hydrologic Response Units (HRUs) and between the HRUs and the MODFLOW finite-difference cells. This report describes the organization, concepts, design, and mathematical formulation of all GSFLOW model components. An important aspect of the integrated model design is its ability to conserve water mass and to provide comprehensive water budgets for a location of interest. This report includes descriptions of how water budgets are calculated for the integrated model and for individual model components. GSFLOW provides a robust modeling system for simulating flow through the hydrologic cycle, while allowing for future enhancements to incorporate other simulation techniques.

Tracer Tests in the Fractured Rock to Investigate Preferential Groundwater Flow

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

Stable isotopes and volatile organic compounds along seven ground-water flow paths in divergent and convergent flow systems, southern California, 2000

USGS Publications Warehouse

Milby Dawson, Barbara J.; Belitz, Kenneth; Land, Michael; Danskin, Wesley R.

2003-01-01

Ground water is a major source of drinking water in southern California. In an effort to understand factors influencing the susceptibility of ground water tapped by public supply wells, the U.S. Geological Survey has undertaken studies in cooperation with the California State Water Resources Control Board. The vertical and lateral distribution of stable isotopes (deuterium and oxygen-18) and volatile organic compounds (VOC) were examined along seven ground-water flow paths in three urban ground-water basins in southern California: Central Basin in Los Angeles County, Main Basin in Orange County, and Bunker Hill Basin in San Bernardino County. Forty-seven monitoring wells and 100 public supply wells were sampled. The results of this study suggest that the direction of flow and perhaps the degree of confinement in an aquifer system are important controls on the distribution of VOCs. Ground-water flow in the Central and Main Basins in the southern California coastal plain is characterized as radially divergent, with ground-water flow directions moving outward from focused areas of recharge in the unconfined part of the aquifer system toward dispersed areas of discharge in the more confined part. In these basins, there is a volume of water containing VOCs that extends out into a volume of water containing no VOCs. This pattern suggests that radially divergent flow systems disperse VOCs in distal areas. The overall pattern also suggests that ground water in the pressure area is generally insulated from compounds introduced at land surface. These two factors?dispersion of VOCs due to divergence of flow and insulation from land-surface inputs?suggest that the susceptibility of public supply wells to surface contamination decreases with distance in radially divergent, well confined ground-water flow system. In the inland Bunker Hill Basin, ground-water flow is characterized as radially convergent; ground-water flow directions move inward from dispersed recharge areas in

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

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

Cole, Charles R.; Bergeron, Marcel P.; Murray, Christopher J.

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 anmore » uncertainty analysis framework.« less

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.

Documentation of a computer program to simulate stream-aquifer relations using a modular, finite-difference, ground-water flow model

USGS Publications Warehouse

Prudic, David E.

1989-01-01

Computer models are widely used to simulate groundwater flow for evaluating and managing the groundwater resource of many aquifers, but few are designed to also account for surface flow in streams. A computer program was written for use in the US Geological Survey modular finite difference groundwater flow model to account for the amount of flow in streams and to simulate the interaction between surface streams and groundwater. The new program is called the Streamflow-Routing Package. The Streamflow-Routing Package is not a true surface water flow model, but rather is an accounting program that tracks the flow in one or more streams which interact with groundwater. The program limits the amount of groundwater recharge to the available streamflow. It permits two or more streams to merge into one with flow in the merged stream equal to the sum of the tributary flows. The program also permits diversions from streams. The groundwater flow model with the Streamflow-Routing Package has an advantage over the analytical solution in simulating the interaction between aquifer and stream because it can be used to simulate complex systems that cannot be readily solved analytically. The Streamflow-Routing Package does not include a time function for streamflow but rather streamflow entering the modeled area is assumed to be instantly available to downstream reaches during each time period. This assumption is generally reasonable because of the relatively slow rate of groundwater flow. Another assumption is that leakage between streams and aquifers is instantaneous. This assumption may not be reasonable if the streams and aquifers are separated by a thick unsaturated zone. Documentation of the Streamflow-Routing Package includes data input instructions; flow charts, narratives, and listings of the computer program for each of four modules; and input data sets and printed results for two test problems, and one example problem. (Lantz-PTT)

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

USGS Publications Warehouse

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

1996-01-01

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 U.S. Department of Energy, under its Environmental Restoration Program, has made NTS the subject of a long-term investigation. Efforts supported through the U.S. Department of Energy program 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. Test-generated contaminants have been introduced over large areas and at variable depths above and below the water table throughout NTS. Evaluating the risks associated with these byproducts of underground testing presupposes a knowledge of the source, transport, and potential receptors of these contaminants. 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. Any assessment of the risk must rely in part on the current understanding of ground-water flow, and the assessment will be only as good as the understanding

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.

Construction of a groundwater-flow model for the Big Sioux Aquifer using airborne electromagnetic methods, Sioux Falls, South Dakota

USGS Publications Warehouse

Valder, Joshua F.; Delzer, Gregory C.; Carter, Janet M.; Smith, Bruce D.; Smith, David V.

2016-09-28

The city of Sioux Falls is the fastest growing community in South Dakota. In response to this continued growth and planning for future development, Sioux Falls requires a sustainable supply of municipal water. Planning and managing sustainable groundwater supplies requires a thorough understanding of local groundwater resources. The Big Sioux aquifer consists of glacial outwash sands and gravels and is hydraulically connected to the Big Sioux River, which provided about 90 percent of the city’s source-water production in 2015. Managing sustainable groundwater supplies also requires an understanding of groundwater availability. An effective mechanism to inform water management decisions is the development and utilization of a groundwater-flow model. A groundwater-flow model provides a quantitative framework for synthesizing field information and conceptualizing hydrogeologic processes. These groundwater-flow models can support decision making processes by mapping and characterizing the aquifer. Accordingly, the city of Sioux Falls partnered with the U.S. Geological Survey to construct a groundwater-flow model. Model inputs will include data from advanced geophysical techniques, specifically airborne electromagnetic methods.

Simulation of ground-water flow in the Vevay Township area, Ingham County, Michigan

USGS Publications Warehouse

Luukkonen, Carol L.; Simard, Andreanne

2004-01-01

Ground water is the primary source of water for domestic, public-supply, and industrial use within the Tri-County region that includes Clinton, Eaton, and Ingham Counties in Michigan. Because of the importance of this ground-water resource, numerous communities, including the city of Mason in Ingham County, have begun local Wellhead Protection Programs. In these programs, communities protect their groundwater resource by identifying the areas that contribute water to production wells and potential sources of contamination, and by developing methods to manage and minimize threats to the water supply. In addition, some communities in Michigan are concerned about water availability, particularly in areas experiencing water-level declines in the vicinity of quarry dewatering operations. In areas where Wellhead Protection Programs are implemented and there are potential threats to the water supply, residents and communities need adequate information to protect the water supply.In 1996, a regional ground-water-flow model was developed by the U.S. Geological Survey to simulate ground-water flow in Clinton, Eaton, and Ingham Counties. This model was developed primarily to simulate the bedrock ground-waterflow system; ground-water flow in the unconsolidated glacial sediments was simulated to support analysis of flow in the underlying bedrock Saginaw aquifer. Since its development in 1996, regional model simulations have been conducted to address protection concerns and water availability questions of local water-resources managers. As a result of these continuing model simulations, additional hydrogeologic data have been acquired in the Tri-County region that has improved the characterization of the simulated ground-water-flow system and improved the model calibration. A major benefit of these updates and refinements is that the regional Tri-County model continues to be a useful tool that improves the understanding of the ground-water-flow system in the Tri-County region

Modeling Groundwater Flow System of a Drainage Basin in the Basement Complex Environment of Southwestern Nigera

NASA Astrophysics Data System (ADS)

Akinwumiju, Akinola S.; Olorunfemi, Martins O.

2018-05-01

This study attempted to model the groundwater flow system of a drainage basin within the Basement Complex environment of Southwestern Nigeria. Four groundwater models were derived from Vertical Electrical Sounding (VES) Data, remotely sensed data, geological information (hydrolineaments and lithology) and borehole data. Subsequently, two sub-surface (local and regional) flow systems were delineated in the study area. While the local flow system is controlled by surface topography, the regional flow system is controlled by the networks of intermediate and deep seated faults/fractures. The local flow system is characterized by convergence, divergence, inflow and outflow in places, while the regional flow system is dominated by NNE-SSW and W-E flow directions. Minor flow directions include NNW-SSE and E-W with possible linkages to the main flow-paths. The NNE-SSW regional flow system is a double open ended flow system with possible linkage to the Niger Trough. The W-E regional flow system is a single open ended system that originates within the study area (with possible linkage to the NNE-SSW regional flow system) and extends to Ikogosi in the adjoining drainage basin. Thus, the groundwater drainage basin of the study area is much larger and extensive than its surface drainage basin. The all year round flowing (perennial) rivers are linked to groundwater outcrops from faults/fractures and contact zones. Consequently, larger percentage of annual rainwater usually leaves the basin in form of runoff and base flow. Therefore, the basin is categorized as a donor basin but with suspected subsurface water input at its northeastern axis.

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

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.

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

USGS Publications Warehouse

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

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.

Soil and geologic controls on recharge and groundwater flow response to climate perturbation: A case study of the Yakima River Basin

NASA Astrophysics Data System (ADS)

Nguyen, T. T.; Pham, H. V.; Bachmann, M.; Tague, C.; Adam, J. C.

2017-12-01

The Yakima River Basin (YRB) is one of the most important agricultural basins in Washington State with annual revenues in excess of $3.2 billion. This intensively irrigated basin is, however, one of the state's most climatically sensitive water resources system as it heavily relies on winter snowpack and limited reservoir storage. Water shortages and drought are expected to be more frequent with climate change, population growth and increasing agricultural demand. This could result in significant impacts on the groundwater system and subsequently the Yakima River. The goal of this study is to assess how soil and geologic characteristics affect catchment recharge and groundwater flow across three catchments within the YRB using a coupled framework including a physically based hydro-ecological model, the Regional Hydro-Ecologic Simulation System (RHESSys) and a groundwater model, MODFLOW. Soil and geologic-related parameters were randomly sampled to use within the Distributed Evaluation of Local Sensitivity Analysis (DELSA) framework to explore their roles in governing catchment recharge and groundwater flow to climate perturbation. Preliminarily results show that catchment recharge is most sensitive to variation in soil transmissivity in two catchments. However, in the other catchment, recharge is more influenced by soil field capacity and bypass recharge. Recharge is also more sensitive to geologic related parameters in catchments where a portion of its flow comes from deep groundwater. When including the effect of climate perturbations, the sensitivity of recharge responses to soil and geologic characteristics varies with temperature and precipitation change. On the other hand, horizontal hydraulic conductivity is the dominant factor that controls groundwater flow responses in catchments with low permeability soil; alternatively, specific storage (and, to some extent, vertical anisotropy) are important in catchments with more conductive soil. The modeling

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.

Scale problems in assessment of hydrogeological parameters of groundwater flow models

NASA Astrophysics Data System (ADS)

Nawalany, Marek; Sinicyn, Grzegorz

2015-09-01

An overview is presented of scale problems in groundwater flow, with emphasis on upscaling of hydraulic conductivity, being a brief summary of the conventional upscaling approach with some attention paid to recently emerged approaches. The focus is on essential aspects which may be an advantage in comparison to the occasionally extremely extensive summaries presented in the literature. In the present paper the concept of scale is introduced as an indispensable part of system analysis applied to hydrogeology. The concept is illustrated with a simple hydrogeological system for which definitions of four major ingredients of scale are presented: (i) spatial extent and geometry of hydrogeological system, (ii) spatial continuity and granularity of both natural and man-made objects within the system, (iii) duration of the system and (iv) continuity/granularity of natural and man-related variables of groundwater flow system. Scales used in hydrogeology are categorised into five classes: micro-scale - scale of pores, meso-scale - scale of laboratory sample, macro-scale - scale of typical blocks in numerical models of groundwater flow, local-scale - scale of an aquifer/aquitard and regional-scale - scale of series of aquifers and aquitards. Variables, parameters and groundwater flow equations for the three lowest scales, i.e., pore-scale, sample-scale and (numerical) block-scale, are discussed in detail, with the aim to justify physically deterministic procedures of upscaling from finer to coarser scales (stochastic issues of upscaling are not discussed here). Since the procedure of transition from sample-scale to block-scale is physically well based, it is a good candidate for upscaling block-scale models to local-scale models and likewise for upscaling local-scale models to regional-scale models. Also the latest results in downscaling from block-scale to sample scale are briefly referred to.

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

Rare Earth Element Concentrations and Fractionation Patterns Along Groundwater Flow Paths in Two Different Aquifer Types (i.e., Sand vs. Carbonate)

NASA Astrophysics Data System (ADS)

Johannesson, K. H.; Tang, J.

2003-12-01

Groundwater samples were collected in two different types of aquifer (i.e., Carrizo Sand Aquifer, Texas and Upper Floridan carbonate Aquifer, west-central Florida) to study the concentrations, fractionation, and speciation of rare earth elements (REE) along groundwater flow paths in each aquifer. Major solutes and dissolved organic carbon (DOC) were also measured in these groundwaters. The Carrizo Sand aquifer was sampled in October 2002 and June 2003, whereas, to date, we have only sampled the Floridan once (i.e., June 2003). The data reveal no significant seasonal differences in major solute and REE concentrations for the Carrizo. In Carrizo sand aquifer, groundwaters from relatively shallow wells (i.e., less than 167 m) in the recharge zone are chiefly Ca-Na-HCO3-Cl type waters. With flow down-gradient the groundwaters shift composition to the Na-HCO3 waters. pH and alkalinity initially decrease with flow away from the recharge zone before increasing again down-gradient. DOC is generally low (0.65 mg/L) along the flow path. REE concentrations are highest in groundwaters from the recharge zone (Nd 40.5 pmol/kg), and decrease substantially with flow down-gradient reaching relatively low and stable values (Nd 4.1-8.6 pmol/kg) roughly 10 km from the recharge zone. Generally, Carrizo groundwaters exhibit HREE-enriched shale-normalized patterns. The HREE enrichments are especially strong for waters from the recharge zone [(Yb/Nd)SN =1.7-5.6], whereas down-gradient (deep) groundwaters have flatter patterns [(Yb/Nd)SN =0.7-2.5]. All groundwaters have slightly positive Eu anomalies (Eu/Eu* 0.09-0.14) and negative Ce anomalies (Ce/Ce* -0.85 - -0.07). In the Upper Floridan Aquifer, Ca, Mg, SO4, and Cl concentrations generally increase along groundwater flow path, whereas pH and alkalinity generally decrease. DOC is higher (0.64 - 2.29 mg/L) than in the Carrizo and initially increases along the flow path and then decreases down-gradient. LREE (Nd) concentrations generally

Simulation of groundwater and surface-water flow in the upper Deschutes Basin, Oregon

USGS Publications Warehouse

Gannett, Marshall W.; Lite, Kenneth E.; Risley, John C.; Pischel, Esther M.; La Marche, Jonathan L.

2017-10-20

This report describes a hydrologic model for the upper Deschutes Basin in central Oregon developed using the U.S. Geological Survey (USGS) integrated Groundwater and Surface-Water Flow model (GSFLOW). The upper Deschutes Basin, which drains much of the eastern side of the Cascade Range in Oregon, is underlain by large areas of permeable volcanic rock. That permeability, in combination with the large annual precipitation at high elevations, results in a substantial regional aquifer system and a stream system that is heavily groundwater dominated.The upper Deschutes Basin is also an area of expanding population and increasing water demand for public supply and agriculture. Surface water was largely developed for agricultural use by the mid-20th century, and is closed to additional appropriations. Consequently, water users look to groundwater to satisfy the growing demand. The well‑documented connection between groundwater and the stream system, and the institutional and legal restrictions on streamflow depletion by wells, resulted in the Oregon Water Resources Department (OWRD) instituting a process whereby additional groundwater pumping can be permitted only if the effects to streams are mitigated, for example, by reducing permitted surface-water diversions. Implementing such a program requires understanding of the spatial and temporal distribution of effects to streams from groundwater pumping. A groundwater model developed in the early 2000s by the USGS and OWRD has been used to provide insights into the distribution of streamflow depletion by wells, but lacks spatial resolution in sensitive headwaters and spring areas.The integrated model developed for this project, based largely on the earlier model, has a much finer grid spacing allowing resolution of sensitive headwater streams and important spring areas, and simulates a more complete set of surface processes as well as runoff and groundwater flow. In addition, the integrated model includes improved

Ground-water flow patterns and water budget of a bottomland forested wetland, Black Swamp, eastern Arkansas

USGS Publications Warehouse

Gonthier, G.J.; Kleiss, B.A.

1996-01-01

The U.S. Geological Survey, working in cooperation with the U.S. Army Corps of Engineers, Waterways Experiment Station, collected surface-water and ground-water data from 119 wells and 13 staff gages from September 1989 to September 1992 to describe ground-water flow patterns and water budget in the Black Swamp, a bottomland forested wetland in eastern Arkansas. The study area was between two streamflow gaging stations located about 30.5 river miles apart on the Cache River. Ground-water flow was from northwest to southeast with some diversion toward the Cache River. Hydraulic connection between the surface water and the alluvial aquifer is indicated by nearly equal changes in surface-water and ground-water levels near the Cache River. Diurnal fluctuations of hydraulic head ranged from more than 0 to 0.38 feet and were caused by evapotranspiration. Changes in hydraulic head of the alluvial aquifer beneath the wetland lagged behind stage fluctuations and created the potential for changes in ground-water movement. Differences between surface-water levels in the wetland and stage of the Cache River created a frequently occurring local ground-water flow condition in which surface water in the wetland seeped into the upper part of the alluvial aquifer and then seeped into the Cache River. When the Cache River flooded the wetland, ground water consistently seeped to the surface during falling surface-water stage and surface water seeped into the ground during rising surface-water stage. Ground-water flow was a minor component of the water budget, accounting for less than 1 percent of both inflow and outflow. Surface-water drainage from the study area through diversion canals was not accounted for in the water budget and may be the reason for a surplus of water in the budget. Even though ground-water flow volume is small compared to other water budget components, ground-water seepage to the wetland surface may still be vital to some wetland functions.

Estimating shallow groundwater availability in small catchments using streamflow recession and instream flow requirements of rivers in South Africa

NASA Astrophysics Data System (ADS)

Ebrahim, Girma Y.; Villholth, Karen G.

2016-10-01

Groundwater is an important resource for multiple uses in South Africa. Hence, setting limits to its sustainable abstraction while assuring basic human needs is required. Due to prevalent data scarcity related to groundwater replenishment, which is the traditional basis for estimating groundwater availability, the present article presents a novel method for determining allocatable groundwater in quaternary (fourth-order) catchments through information on streamflow. Using established methodologies for assessing baseflow, recession flow, and instream ecological flow requirement, the methodology develops a combined stepwise methodology to determine annual available groundwater storage volume using linear reservoir theory, essentially linking low flows proportionally to upstream groundwater storages. The approach was trialled for twenty-one perennial and relatively undisturbed catchments with long-term and reliable streamflow records. Using the Desktop Reserve Model, instream flow requirements necessary to meet the present ecological state of the streams were determined, and baseflows in excess of these flows were converted into a conservative estimates of allocatable groundwater storages on an annual basis. Results show that groundwater development potential exists in fourteen of the catchments, with upper limits to allocatable groundwater volumes (including present uses) ranging from 0.02 to 3.54 × 106 m3 a-1 (0.10-11.83 mm a-1) per catchment. With a secured availability of these volume 75% of the years, variability between years is assumed to be manageable. A significant (R2 = 0.88) correlation between baseflow index and the drainage time scale for the catchments underscores the physical basis of the methodology and also enables the reduction of the procedure by one step, omitting recession flow analysis. The method serves as an important complementary tool for the assessment of the groundwater part of the Reserve and the Groundwater Resource Directed Measures in

Treatment of Chlorinated Aliphatic Contamination of Groundwater by Horizontal Recirculation Wells and by Constructed Vertical Flow Wetlands

DTIC Science & Technology

2002-03-01

groundwater laden with contaminants. Once the contaminated water is at the surface, it must be treated for contaminant destruction, generally by...treatment walls only work under very specific hydrogeologic conditions (relatively shallow water table, no seasonal fluctuations in groundwater flow...GCWs Elevation Schematic Water Table Contaminated Groundwater Contaminated Groundwater Treated Groundwater Treated Groundwater Reactive Porous Medium

Regional scale impact of tidal forcing on groundwater flow in unconfined coastal aquifers

NASA Astrophysics Data System (ADS)

Pauw, P. S.; Oude Essink, G. H. P.; Leijnse, A.; Vandenbohede, A.; Groen, J.; van der Zee, S. E. A. T. M.

2014-09-01

This paper considers the impact of tidal forcing on regional groundwater flow in an unconfined coastal aquifer. Numerical models are used to quantify this impact for a wide range of hydrogeological conditions. Both a shallow and a deep aquifer are investigated with regard to three dimensionless parameter groups that determine the groundwater flow to a large extent. Analytical expressions are presented that allow for a quick estimate of the regional scale effect of tidal forcing under the same conditions as used in the numerical models. Quantitatively, the results in this paper are complementary to previous studies by taking into account variable density groundwater flow, dispersive salt transport and a seepage face in the intertidal area. Qualitatively, the results are in line with previous investigations. The time-averaged hydraulic head at the high tide mark increases upon a decrease of each of the three considered dimensionless parameter groups: R (including the ratio of the hydraulic conductivity and the precipitation excess), α (the slope of the intertidal area) and AL (the ratio of the width of the fresh water lens and the tidal amplitude). The relative change of the location and the hydraulic head of the groundwater divide, which together characterize regional groundwater flow, increase as α and AL decrease, but decrease as R decreases. The difference between the analytical solutions and numerical results is small. Therefore, the presented analytical solutions can be used to estimate the bias that is introduced in a numerical model if tidal forcing is neglected. The results should be used with caution in case of significant wave forcing, as this was not considered.

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

Revising the `Henry Problem' of density-driven groundwater flow: A review of historic Biscayne aquifer data.

NASA Astrophysics Data System (ADS)

Weyer, K. U.

2016-12-01

Coastal groundwater flow investigations at the Cutler site of the Biscayne Bay south of Miami, Florida, gave rise to the dominating concept of density-driven flow of sea water into coastal aquifers indicated as a saltwater wedge. Within that wedge convection type return flow of seawater and a dispersion zone were concluded by Cooper et al. (1964, USGS Water Supply Paper 1613-C) to be the cause of the Biscayne aquifer `sea water wedge'. This conclusion was merely based on the chloride distribution within the aquifer and on an analytical model concept assuming convection flow within a confined aquifer without taking non-chemical field data into consideration. This concept was later labelled the `Henry Problem', which any numerical variable density flow program has to be able to simulate to be considered acceptable. Revisiting the above summarizing publication with its record of piezometric field data (heads) showed that the so-called sea water wedge was actually caused by discharging deep saline groundwater driven by gravitational flow and not by denser sea water. Density driven flow of seawater into the aquifer was not found reflected in the head measurements for low and high tide conditions which had been taken contemporaneously with the chloride measurements. These head measurements had not been included in the flow interpretation. The very same head measurements indicated a clear dividing line between shallow local fresh groundwater flow and saline deep groundwater flow without the existence of a dispersion zone or a convection cell. The Biscayne situation emphasizes the need for any chemical interpretation of flow pattern to be backed up by head data as energy indicators of flow fields. At the Biscayne site density driven flow of seawater did and does not exist. Instead this site and the Florida coast line in general are the end points of local fresh and regional saline groundwater flow systems driven by gravity forces and not by density differences.

Channel Incision Driven by Suburbanization: Impacts to Riparian Groundwater Flow and Overbank Flow Frequency

NASA Astrophysics Data System (ADS)

Bowles, C. J.; Lawrence, R. L.; Noll, C.; Hancock, G. S.

2005-12-01

Channel incision is a widely observed response to increased flow in urbanized watersheds, but the effects of channel lowering on riparian water tables is not well documented. In a rapidly incising suburban stream in the Virginia Coastal Plain, we hypothesize that stream incision has lowered floodplain water tables and decreased the overbank flow frequency. The monitored stream is a tributary to the James River draining 1.3 km2 of which 15% is impervious cover. Incision has occurred largely through upstream migration of a one meter high knickpoint at a rate of ~1.5 m/yr, primarily during high flow events. We installed 63 wells in six stream-perpendicular transects as well as a cluster of wells around the knickpoint to assess water table elevations beneath the floodplain adjacent to the incising stream. Two transects are located 30 and 50 m upstream of the knickpoint in the unincised floodplain, and the remainder are 5, 30, 70, and 100 m downstream in the incised floodplain. In one transect above and two below, pressure transducers attached to dataloggers provide a high-resolution record of water table changes. Erosion pins were installed and channel cross-sections surveyed to determine streambed stability. Significant differences are observed in bank morphology and groundwater flow above vs. below the knickpoint. Above the knickpoint, the banks are stable, ~3 m wide, and ~0.3 m deep, and widen and deepen slightly toward the knickpoint. The water table is relatively flat and is 0.2-0.4 m below the floodplain surface, and groundwater contours suggest flow is parallel to the stream direction. The water table responds immediately to precipitation events, and rises to the floodplain surface in significant rainfall events. Immediately downstream of the knickpoint, channel width increases by about a meter, and stream depth increases to ~1.5 meters. The water table immediately below the knickpoint possesses a steep gradient, and is up to one meter below the floodplain

Groundwater flow simulation of the Savannah River Site general separations area

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

Flach, G.; Bagwell, L.; Bennett, P.

The most recent groundwater flow model of the General Separations Area, Savannah River Site, is referred to as the “GSA/PORFLOW” model. GSA/PORFLOW was developed in 2004 by porting an existing General Separations Area groundwater flow model from the FACT code to the PORFLOW code. The preceding “GSA/FACT” model was developed in 1997 using characterization and monitoring data through the mid-1990’s. Both models were manually calibrated to field data. Significantly more field data have been acquired since the 1990’s and model calibration using mathematical optimization software has become routine and recommended practice. The current task involved updating the GSA/PORFLOW model usingmore » selected field data current through at least 2015, and use of the PEST code to calibrate the model and quantify parameter uncertainty. This new GSA groundwater flow model is named “GSA2016” in reference to the year in which most development occurred. The GSA2016 model update is intended to address issues raised by the DOE Low-Level Waste (LLW) Disposal Facility Federal Review Group (LFRG) in a 2008 review of the E-Area Performance Assessment, and by the Nuclear Regulatory Commission in reviews of tank closure and Saltstone Disposal Facility Performance Assessments.« less

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

NASA Astrophysics Data System (ADS)

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

2010-10-01

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

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.

Structure and application of an interface program between a geographic-information system and a ground-water flow model

USGS Publications Warehouse

Van Metre, P.C.

1990-01-01

A computer-program interface between a geographic-information system and a groundwater flow model links two unrelated software systems for use in developing the flow models. The interface program allows the modeler to compile and manage geographic components of a groundwater model within the geographic information system. A significant savings of time and effort is realized in developing, calibrating, and displaying the groundwater flow model. Four major guidelines were followed in developing the interface program: (1) no changes to the groundwater flow model code were to be made; (2) a data structure was to be designed within the geographic information system that follows the same basic data structure as the groundwater flow model; (3) the interface program was to be flexible enough to support all basic data options available within the model; and (4) the interface program was to be as efficient as possible in terms of computer time used and online-storage space needed. Because some programs in the interface are written in control-program language, the interface will run only on a computer with the PRIMOS operating system. (USGS)

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; 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

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.

Simulation of the effects of development of the ground-water flow system of Long Island, New York

USGS Publications Warehouse

Buxton, Herbert T.; Smolensky, Douglas A.

1999-01-01

Extensive development on Long Island since the late 19th century and projections of increased urbanization and ground-water use makes effective water-resource management essential for preservation of the island's hydrologic environment and maintenance of a reliable source of water supply. This report presents results of a ground-water flow simulation analysis of the effects of development on the Long Island ground-water system. It describes ground-water levels, stream-flow, and the ground-water budget for the predevelopment period (pre-1900), the 1960's drought, and a more recent (1968-83) period with significant hydrologic stress. The report also presents estimated effects of a proposed water-supply strategy for the year 2020. Long Island has three major aquifers-the upper glacial (water-table), the Magothy, and the Lloyd aquifers-that are separated to varying degrees by confining units. Before development, recharge from precipitation entered the ground-water system at a rate of more than 1.1 billion gallons per day. An equal amount discharged to streams (41 percent), the shore (52 percent), and subsea boundaries (7 percent) . Urbanization and withdrawal of more than 400 Mgal/d (million gallons per day) from wells have resulted in local effects that include declines in ground-water levels, drying up and burial of streams and wetlands, reduction of ground-water recharge by increased overland flow to the ocean, a general decrease in ground-water discharge, and salt water intrusion. In some areas, the reduction in recharge is mitigated by leakage from water-supply and wastewater disposal lines, and infiltration of storm water through recharge basins. During 1968-83, a net loss of 240 Mgal/d from the ground-water system caused a decrease in ground-water discharge to streams (135 Mgal/d), to the shore (82 Mgal/d), and to subsea boundaries (23Mgal/d).The greatest adverse effects have been in western Long Island, where the most severe development has occurred. This

Groundwater flow in the Venice lagoon and remediation of the Porto Marghera industrial area (Italy)

NASA Astrophysics Data System (ADS)

Beretta, Giovanni Pietro; Terrenghi, Jacopo

2017-05-01

This study aims to determine the groundwater flow in a large area of the Venice (northeast Italy) lagoon that is under great anthropogenic pressure, which is influencing the regional flow in the surficial aquifer (about 30 m depth). The area presents several elements that condition the groundwater flow: extraction by means of drainage pumps and wells; tidal fluctuation; impermeable barriers that define part of the coastline, rivers and artificial channels; precipitation; recharge, etc. All the elements were studied separately, and then they were brought together in a numerical groundwater flow model to estimate the impact of each one. Identification of the impact of each element will help to optimise the characteristics of the Porto Marghera remediation systems. Longstanding industrial activity has had a strong impact on the soil and groundwater quality, and expensive and complex emergency remediation measures in problematic locations have been undertaken to ensure the continuity of industrial and maritime activities. The land reclamation and remediation works withdraw 56-74% of the water budget, while recharge from the river accounts for about 21-48% of the input. Only 21-42% of groundwater in the modelled area is derived from natural recharge sources, untouched by human activity. The drop of the piezometric level due to the realization of the upgradient impermeable barrier can be counteracted with the reduction of the pumping rate of the remediation systems.

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

USGS Publications Warehouse

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

1998-01-01

This report describes the results of two related studies: a study of ground-water age, flow, and quality near a landfill in the south-central part of the Swinomish Indian Reservation; and a study of changes in ground-water conditions for the entire reservation from 1976 to 1996. The Swinomish Indian Reservation is a 17-square-mile part of Fidalgo Island in northwestern Washington. The groundwater flow system in the reservation is probably independent of other flow systems in the area because it is almost completely surrounded by salt water. There has been increasing stress on the ground-water resources of the reservation because the population has almost tripled during the past 20 years, and 65 percent of the population obtain their domestic water supply from the local ground-water system. The Swinomish Tribe is concerned that increased pumping of ground water might have caused decreased ground-water discharge into streams, declines in ground-water levels, and seawater intrusion into the ground-water system. There is also concern that leachate from an inactive landfill containing mostly household and wood-processing wastes may be contaminating the ground water. The study area is underlain by unconsolidated glacial and interglacial deposits of Quaternary age that range from about 300 to 900 feet thick. Five hydrogeologic units have been defined in the unconsolidated deposits. From top to bottom, the hydrogeologic units are a till confining bed, an outwash aquifer, a clay confining bed, a sea-level aquifer, and an undifferentiated unit. The ground-water flow system of the reservation is similar to other island-type flow systems. Water enters the system through the water table as infiltration and percolation of precipitation (recharge), then the water flows downward and radially outward from the center of the island. At the outside edges of the system, ground water flows upward to discharge into the surrounding saltwater bodies. Average annual recharge is estimated to

Climate proxy data as groundwater tracers in regional flow systems

NASA Astrophysics Data System (ADS)

Clark, J. F.; Morrissey, S. K.; Stute, M.

2008-05-01

The isotopic and chemical signatures of groundwater reflect local climate conditions. By systematically analyzing groundwater and determining their hydrologic setting, records of past climates can be constructed. Because of their chemistries and relatively uncomplicated source functions, dissolved noble gases have yielded reliable records of continental temperatures for the last 30,000 to 50,000 years. Variations in the stable isotope compositions of groundwater due to long term climate changes have also been documented over these time scales. Because glacial - interglacial climate changes are relatively well known, these climate proxies can be used as "stratigraphic" markers within flow systems and used to distinguish groundwaters that have recharged during the Holocene from those recharged during the last glacial period, important time scales for distinguishing regional and local flow systems in many aquifers. In southern Georgia, the climate proxy tracers were able to identify leakage from surface aquifers into the Upper Floridan aquifer in areas previously thought to be confined. In south Florida, the transition between Holocene and glacial signatures in the Upper Floridan aquifer occurs mid-way between the recharge area and Lake Okeechobee. Down gradient of the lake, the proxies are uniform, indicating recharge during the last glacial period. Furthermore, there is no evidence for leakage from the shallow aquifers into the Upper Floridan. In the Lower Floridan, the climate proxies indicate that the saline water entered the aquifer after sea level rose to its present level.

Human effects on the hydrologic system of the Verde Valley, central Arizona, 1910–2005 and 2005–2110, using a regional groundwater flow model

USGS Publications Warehouse

Garner, Bradley D.; Pool, D.R.; Tillman, Fred D.; Forbes, Brandon T.

2013-01-01

Water budgets were developed for the Verde Valley of central Arizona in order to evaluate the degree to which human stresses have affected the hydrologic system and might affect it in the future. The Verde Valley is a portion of central Arizona wherein concerns have been raised about water availability, particularly perennial base flow of the Verde River. The Northern Arizona Regional Groundwater Flow Model (NARGFM) was used to generate the water budgets and was run in several configurations for the 1910–2005 and 2005–2110 time periods. The resultant water budgets were subtracted from one another in order to quantify the relative changes that were attributable solely to human stresses; human stresses included groundwater withdrawals and incidental and artificial recharge but did not include, for example, human effects on the global climate. Three hypothetical and varied conditions of human stresses were developed and applied to the model for the 2005–2110 period. On the basis of this analysis, human stresses during 1910–2005 were found to have already affected the hydrologic system of the Verde Valley, and human stresses will continue to affect the hydrologic system during 2005–2110. Riparian evapotranspiration decreased and underflow into the Verde Valley increased because of human stresses, and net groundwater discharge to the Verde River in the Verde Valley decreased for the 1910–2005 model runs. The model also showed that base flow at the upstream end of the study area, as of 2005, was about 4,900 acre-feet per year less than it would have been in the absence of human stresses. At the downstream end of the Verde Valley, base flow had been reduced by about 10,000 acre-feet per year by the year 2005 because of human stresses. For the 2005–2110 period, the model showed that base flow at the downstream end of the Verde Valley may decrease by an additional 5,400 to 8,600 acre-feet per year because of past, ongoing, and hypothetical future human

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

Evolutionary analysis of groundwater flow: Application of multivariate statistical analysis to hydrochemical data in the Densu Basin, Ghana

NASA Astrophysics Data System (ADS)

Yidana, Sandow Mark; Bawoyobie, Patrick; Sakyi, Patrick; Fynn, Obed Fiifi

2018-02-01

An evolutionary trend has been postulated through the analysis of hydrochemical data of a crystalline rock aquifer system in the Densu Basin, Southern Ghana. Hydrochemcial data from 63 groundwater samples, taken from two main groundwater outlets (Boreholes and hand dug wells) were used to postulate an evolutionary theory for the basin. Sequential factor and hierarchical cluster analysis were used to disintegrate the data into three factors and five clusters (spatial associations). These were used to characterize the controls on groundwater hydrochemistry and its evolution in the terrain. The dissolution of soluble salts and cation exchange processes are the dominant processes controlling groundwater hydrochemistry in the terrain. The trend of evolution of this set of processes follows the pattern of groundwater flow predicted by a calibrated transient groundwater model in the area. The data suggest that anthropogenic activities represent the second most important process in the hydrochemistry. Silicate mineral weathering is the third most important set of processes. Groundwater associations resulting from Q-mode hierarchical cluster analysis indicate an evolutionary pattern consistent with the general groundwater flow pattern in the basin. These key findings are at variance with results of previous investigations and indicate that when carefully done, groundwater hydrochemical data can be very useful for conceptualizing groundwater flow in basins.

TopoDrive and ParticleFlow--Two Computer Models for Simulation and Visualization of Ground-Water Flow and Transport of Fluid Particles in Two Dimensions

USGS Publications Warehouse

Hsieh, Paul A.

2001-01-01

This report serves as a user?s guide for two computer models: TopoDrive and ParticleFlow. These two-dimensional models are designed to simulate two ground-water processes: topography-driven flow and advective transport of fluid particles. To simulate topography-driven flow, the user may specify the shape of the water table, which bounds the top of the vertical flow section. To simulate transport of fluid particles, the model domain is a rectangle with overall flow from left to right. In both cases, the flow is under steady state, and the distribution of hydraulic conductivity may be specified by the user. The models compute hydraulic head, ground-water flow paths, and the movement of fluid particles. An interactive visual interface enables the user to easily and quickly explore model behavior, and thereby better understand ground-water flow processes. In this regard, TopoDrive and ParticleFlow are not intended to be comprehensive modeling tools, but are designed for modeling at the exploratory or conceptual level, for visual demonstration, and for educational purposes.

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.

Simulation of ground-water flow in the Cedar River alluvium, northwest Black Hawk County and southwest Bremer County, Iowa

USGS Publications Warehouse

Schaap, Bryan D.; Savoca, Mark E.; Turco, Michael J.

2003-01-01

In general, once high ground-water levels occur, either because of high Cedar River water Abstract levels or above normal local precipitation or both, ground-water in the central part of the study area along Highway 218 flows toward the south rather than following shorter flow paths to the Cedar River. Intermittent streams in the study area discharge substantial amounts of water from the ground-water flow system.

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.

2016-12-01

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.

An update of the Death Valley regional groundwater flow system transient model, Nevada and California

USGS Publications Warehouse

Belcher, Wayne R.; Sweetkind, Donald S.; Faunt, Claudia C.; Pavelko, Michael T.; Hill, Mary C.

2017-01-19

Since the original publication of the Death Valley regional groundwater flow system (DVRFS) numerical model in 2004, more information on the regional groundwater flow system in the form of new data and interpretations has been compiled. Cooperators such as the Bureau of Land Management, National Park Service, U.S. Fish and Wildlife Service, the Department of Energy, and Nye County, Nevada, recognized a need to update the existing regional numerical model to maintain its viability as a groundwater management tool for regional stakeholders. The existing DVRFS numerical flow model was converted to MODFLOW-2005, updated with the latest available data, and recalibrated. Five main data sets were revised: (1) recharge from precipitation varying in time and space, (2) pumping data, (3) water-level observations, (4) an updated regional potentiometric map, and (5) a revision to the digital hydrogeologic framework model.The resulting DVRFS version 2.0 (v. 2.0) numerical flow model simulates groundwater flow conditions for the Death Valley region from 1913 to 2003 to correspond to the time frame for the most recently published (2008) water-use data. The DVRFS v 2.0 model was calibrated by using the Tikhonov regularization functionality in the parameter estimation and predictive uncertainty software PEST. In order to assess the accuracy of the numerical flow model in simulating regional flow, the fit of simulated to target values (consisting of hydraulic heads and flows, including evapotranspiration and spring discharge, flow across the model boundary, and interbasin flow; the regional water budget; values of parameter estimates; and sensitivities) was evaluated. This evaluation showed that DVRFS v. 2.0 simulates conditions similar to DVRFS v. 1.0. Comparisons of the target values with simulated values also indicate that they match reasonably well and in some cases (boundary flows and discharge) significantly better than in DVRFS v. 1.0.

Using SWAT-MODFLOW to simulate groundwater flow and groundwater-surface water interactions in an intensively irrigated stream-aquifer system

NASA Astrophysics Data System (ADS)

Wei, X.; Bailey, R. T.

2017-12-01

Agricultural irrigated watersheds in semi-arid regions face challenges such as waterlogging, high soil salinity, reduced crop yield, and leaching of chemical species due to extreme shallow water tables resulting from long-term intensive irrigation. Hydrologic models can be used to evaluate the impact of land management practices on water yields and groundwater-surface water interactions in such regions. In this study, the newly developed SWAT-MODFLOW, a coupled surface/subsurface hydrologic model, is applied to a 950 km2 watershed in the Lower Arkansas River Valley (southeastern Colorado). The model accounts for the influence of canal diversions, irrigation applications, groundwater pumping, and earth canal seepage losses. The model provides a detailed description of surface and subsurface flow processes, thereby enabling detailed description of watershed processes such as runoff, infiltration, in-streamflow, three-dimensional groundwater flow in a heterogeneous aquifer system with sources and sinks (e.g. pumping, seepage to subsurface drains), and spatially-variable surface and groundwater exchange. The model was calibrated and tested against stream discharge from 5 stream gauges in the Arkansas River and its tributaries, groundwater levels from 70 observation wells, and evapotranspiration (ET) data estimated from satellite (ReSET) data during the 1999 to 2007 period. Since the water-use patterns within the study area are typical of many other irrigated river valleys in the United States and elsewhere, this modeling approach is transferable to other regions.

A three-dimensional numerical model of predevelopment conditions in the Death Valley regional ground-water flow system, Nevada and California

USGS Publications Warehouse

D'Agnese, Frank A.; O'Brien, G. M.; Faunt, C.C.; Belcher, W.R.; San Juan, C.

2002-01-01

In the early 1990's, two numerical models of the Death Valley regional ground-water flow system were developed by the U.S. Department of Energy. In general, the two models were based on the same basic hydrogeologic data set. In 1998, the U.S. Department of Energy requested that the U.S. Geological Survey develop and maintain a ground-water flow model of the Death Valley region in support of U.S. Department of Energy programs at the Nevada Test Site. The purpose of developing this 'second-generation' regional model was to enhance the knowledge an understanding of the ground-water flow system as new information and tools are developed. The U.S. Geological Survey also was encouraged by the U.S. Department of Energy to cooperate to the fullest extent with other Federal, State, and local entities in the region to take advantage of the benefits of their knowledge and expertise. The short-term objective of the Death Valley regional ground-water flow system project was to develop a steady-state representation of the predevelopment conditions of the ground-water flow system utilizing the two geologic interpretations used to develop the previous numerical models. The long-term objective of this project was to construct and calibrate a transient model that simulates the ground-water conditions of the study area over the historical record that utilizes a newly interpreted hydrogeologic conceptual model. This report describes the result of the predevelopment steady-state model construction and calibration. The Death Valley regional ground-water flow system is situated within the southern Great Basin, a subprovince of the Basin and Range physiographic province, bounded by latitudes 35 degrees north and 38 degrees 15 minutes north and by longitudes 115 and 118 degrees west. Hydrology in the region is a result of both the arid climatic conditions and the complex geology. Ground-water flow generally can be described as dominated by interbasinal flow and may be conceptualized as

Characterization and simulation of ground-water flow in the Kansas River Valley at Fort Riley, Kansas, 1990-98

USGS Publications Warehouse

Myers, Nathan C.

2000-01-01

Hydrologic data and a ground-water flow model were used to characterize ground-water flow in the Kansas River alluvial aquifer at Fort Riley in northeast Kansas. The ground-water flow model was developed as a tool to project ground-water flow and potential contaminant-transport paths in the alluvial aquifer on the basis of past hydrologic conditions. The model also was used to estimate historical and hypothetical ground-water flow paths with respect to a private- and several public-supply wells. The ground-water flow model area extends from the Smoky Hill and Republican Rivers downstream to about 2.5 miles downstream from the city of Ogden. The Kansas River Valley has low relief and, except for the area within the Fort Riley Military Reservation, is used primarily for crop production. Sedimentary deposits in the Kansas River Valley, formed after the ancestral Kansas River eroded into bedrock, primarily are alluvial sediment deposited by the river during Quaternary time. The alluvial sediment consists of as much as about 75 feet of poorly sorted, coarse-to-fine sand, silt, and clay, 55 feet of which can be saturated with ground water. The alluvial aquifer is unconfined and is bounded on the sides and bottom by Permian-age shale and limestone bedrock. Hydrologic data indicate that ground water in the Kansas River Valley generally flows in a downstream direction, but flow direction can be quite variable near the Kansas River due to changes in river stage. Ground-water-level changes caused by infiltration of precipitation are difficult to detect because they are masked by larger changes caused by fluctuation in Kansas River stage. Ratios of strontium isotopes Sr87 and Sr86 in water collected from wells in the Camp Funston Area indicate that the ground water along the northern valley wall originates, in part, from upland areas north of the river valley. Water from Threemile Creek, which flows out of the uplands north of the river valley, had Sr87:Sr86 ratios similar to

The 2016 groundwater flow model for Dane County, Wisconsin

USGS Publications Warehouse

Parsen, Michael J.; Bradbury, Kenneth R.; Hunt, Randall J.; Feinstein, Daniel T.

2016-01-01

A new groundwater flow model for Dane County, Wisconsin, replaces an earlier model developed in the 1990s by the Wisconsin Geological and Natural History Survey (WGNHS) and the U.S. Geological Survey (USGS). This modeling study was conducted cooperatively by the WGNHS and the USGS with funding from the Capital Area Regional Planning Commission (CARPC). Although the overall conceptual model of the groundwater system remains largely unchanged, the incorporation of newly acquired high-quality datasets, recent research findings, and improved modeling and calibration techniques have led to the development of a more detailed and sophisticated model representation of the groundwater system. The new model is three-dimensional and transient, and conceptualizes the county’s hydrogeology as a 12-layer system including all major unlithified and bedrock hydrostratigraphic units and two high-conductivity horizontal fracture zones. Beginning from the surface down, the model represents the unlithified deposits as two distinct model layers (1 and 2). A single layer (3) simulates the Ordovician sandstone and dolomite of the Sinnipee, Ancell, and Prairie du Chien Groups. Sandstone of the Jordan Formation (layer 4) and silty dolostone of the St. Lawrence Formation (layer 5) each comprise separate model layers. The underlying glauconitic sandstone of the Tunnel City Group makes up three distinct layers: an upper aquifer (layer 6), a fracture feature (layer 7), and a lower aquifer (layer 8). The fracture layer represents a network of horizontal bedding-plane fractures that serve as a preferential pathway for groundwater flow. The model simulates the sandstone of the Wonewoc Formation as an upper aquifer (layer 9) with a bedding-plane fracture feature (layer 10) at its base. The Eau Claire aquitard (layer 11) includes shale beds within the upper portion of the Eau Claire Formation. This layer, along with overlying bedrock units, is mostly absent in the preglacially eroded valleys along

Characterizing Ground-Water Flow Paths in High-Altitude Fractured Rock Settings Impacted by Mining Activities

NASA Astrophysics Data System (ADS)

Wireman, M.; Williams, D.

2003-12-01

The Rocky Mountains of the western USA have tens of thousands of abandoned, inactive and active precious-metal(gold,silver,copper)mine sites. Most of these sites occur in fractured rock hydrogeologic settings. Mining activities often resulted in mobilization and transport of associated heavy metals (zinc,cadmium,lead) which pose a significant threat to aquatic communities in mountain streams.Transport of heavy metals from mine related sources (waste rock piles,tailings impoudments,underground workings, mine pits)can occur along numerous hydrological pathways including complex fracture controlled ground-water pathways. Since 1991, the United States Environmental Protection Agency, the Colorado Division of Minerals and Geology and the University of Colorado (INSTAAR)have been conducting applied hydrologic research at the Mary Murphy underground mine. The mine is in the Chalk Creek mining district which is located on the southwestern flanks of the Mount Princeton Batholith, a Tertiary age intrusive comprised primarily of quartz monzonite.The Mount Princeton batholith comprises a large portion of the southern part of the Collegiate Range west of Buena Vista in Chaffee County, CO. Chalk Creek and its 14 tributaries drain about 24,900 hectares of the eastern slopes of the Range including the mining district. Within the mining district, ground-water flow is controlled by the distribution, orientation and permeability of discontinuities within the bedrock. Important discontinuities include faults, joints and weathered zones. Local and intermediate flow systems are perturbed by extensive underground excavations associated with mining (adits, shafts, stopes, drifts,, etc.). During the past 12 years numerous hydrological investigations have been completed. The investigations have been focused on developing tools for characterizing ground-water flow and contaminant transport in the vicinity of hard-rock mines in fractured-rock settings. In addition, the results from these

The combined use of MODFLOW and precipitation-runoff modeling to simulate groundwater flow in a diffuse-pollution prone watershed.

PubMed

Elçi, A; Karadaş, D; Fistikoğlu, O

2010-01-01

A numerical modeling case study of groundwater flow in a diffuse pollution prone area is presented. The study area is located within the metropolitan borders of the city of Izmir, Turkey. This groundwater flow model was unconventional in the application since the groundwater recharge parameter in the model was estimated using a lumped, transient water-budget based precipitation-runoff model that was executed independent of the groundwater flow model. The recharge rate obtained from the calibrated precipitation-runoff model was used as input to the groundwater flow model, which was eventually calibrated to measured water table elevations. Overall, the flow model results were consistent with field observations and model statistics were satisfactory. Water budget results of the model revealed that groundwater recharge comprised about 20% of the total water input for the entire study area. Recharge was the second largest component in the budget after leakage from streams into the subsurface. It was concluded that the modeling results can be further used as input for contaminant transport modeling studies in order to evaluate the vulnerability of water resources of the study area to diffuse pollution.

Occurrence and distribution of organophosphorus flame retardants and plasticizers in anthropogenically affected groundwater.

PubMed

Regnery, J; Püttmann, W; Merz, C; Berthold, G

2011-02-01

Occurrence and distribution of chlorinated and non-chlorinated organophosphates in 72 groundwater samples from Germany under different recharge/infiltration conditions were investigated. Tris(2-chloro-1-methylethyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP) were the most frequently detected organophosphates in groundwater samples. Highest individual organophosphate concentrations (>0.1 µg L(-1)) were determined in groundwater polluted by infiltrating leachate and groundwater recharged via riverbank filtration of organophosphate-loaded recipients. In samples from springs and deep groundwater monitoring wells that are not affected by surface waters, organophosphate concentrations were mostly below the limit of detection. The occurrence (3-9 ng L(-1)) of TCPP and TCEP in samples from aquifers with groundwater ages between 20 and 45 years indicates the persistence of both compounds within the aquifer. At urban sites organophosphate-loaded precipitation, surface runoff, and leakage of wastewater influenced groundwater quality. For rural sites, where groundwater recharge is only influenced by precipitation, organophosphates were very rarely detectable in groundwater.

Investigation of Submarine Groundwater Discharge and Preferential Groundwater Flow-paths in a Coastal Karst Area using towed Marine and Terrestrial Electrical Resistivity

NASA Astrophysics Data System (ADS)

O'connell, Y.; Daly, E.; Duffy, G.; Henry, T.

2012-12-01

Large volumes of groundwater, containing nutrients and contaminants enter the coastal waters of southern Galway Bay on the west coast of Ireland through submarine groundwater discharge (SGD). The SGD occurs through karstified Carboniferous limestone in a major karst region comprising the Burren and Gort Lowlands. The Carboniferous limestones have experienced extensive dissolution resulting in the development of an underground network of conduits and fissures that define a trimodal groundwater flow pattern across the region. Groundwater discharge to the sea in this area is exclusively intertidal and submarine. Storage in the karst is limited and typical winter rainfall conditions result in the karst system becoming saturated. Temporary lakes (turloughs) form in lowlying areas and act as large reservoirs which provide storage to enable the transmission of the large volumes of water in the system to the sea. Between 2010 and 2012, terrestrial and shallow marine geophysical surveying has been undertaken to investigate preferential groundwater flow-paths and SGD locations in order to quantify the groundwater-seawater interactions in this coastal karst system. A report into the groundwater system of this karst region following a major flood event proposed a conceptual conduit model defined by extensive water tracing, water level monitoring, hydrochemical sampling, geological mapping and drilling. Limited information about the dimensions of the conduits was known. Electrical resistivity tomography (ERT) profiling to depths of 100m below ground level, with multiple array configurations, has been carried out to investigate the modes of groundwater flow in to and out of both temporary and permanent freshwater lakes in the system. Towed dipole-dipole profiles have been recorded to investigate conduits beneath a permanent lake exhibiting a tidal influence despite its location 5.5 km from the seashore. The ERT data indicates significant variations in subsurface resistivities

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

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

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 upmore » 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.« less

Containment of groundwater contamination plumes: minimizing drawdown by aligning capture wells parallel to regional flow

NASA Astrophysics Data System (ADS)

Christ, John A.; Goltz, Mark N.

2004-01-01

Pump-and-treat systems that are installed to contain contaminated groundwater migration typically involve placement of extraction wells perpendicular to the regional groundwater flow direction at the down gradient edge of a contaminant plume. These wells capture contaminated water for above ground treatment and disposal, thereby preventing further migration of contaminated water down gradient. In this work, examining two-, three-, and four-well systems, we compare well configurations that are parallel and perpendicular to the regional groundwater flow direction. We show that orienting extraction wells co-linearly, parallel to regional flow, results in (1) a larger area of aquifer influenced by the wells at a given total well flow rate, (2) a center and ultimate capture zone width equal to the perpendicular configuration, and (3) more flexibility with regard to minimizing drawdown. Although not suited for some scenarios, we found orienting extraction wells parallel to regional flow along a plume centerline, when compared to a perpendicular configuration, reduces drawdown by up to 7% and minimizes the fraction of uncontaminated water captured.

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.

Comparison of a Conceptual Groundwater Model and Physically Based Groundwater Mode

NASA Astrophysics Data System (ADS)

Yang, J.; Zammit, C.; Griffiths, J.; Moore, C.; Woods, R. A.

2017-12-01

Groundwater is a vital resource for human activities including agricultural practice and urban water demand. Hydrologic modelling is an important way to study groundwater recharge, movement and discharge, and its response to both human activity and climate change. To understand the groundwater hydrologic processes nationally in New Zealand, we have developed a conceptually based groundwater flow model, which is fully integrated into a national surface-water model (TopNet), and able to simulate groundwater recharge, movement, and interaction with surface water. To demonstrate the capability of this groundwater model (TopNet-GW), we applied the model to an irrigated area with water shortage and pollution problems in the upper Ruamahanga catchment in Great Wellington Region, New Zealand, and compared its performance with a physically-based groundwater model (MODFLOW). The comparison includes river flow at flow gauging sites, and interaction between groundwater and river. Results showed that the TopNet-GW produced similar flow and groundwater interaction patterns as the MODFLOW model, but took less computation time. This shows the conceptually-based groundwater model has the potential to simulate national groundwater process, and could be used as a surrogate for the more physically based model.

Simulation of ground-water flow in glaciofluvial aquifers in the Grand Rapids area, Minnesota

USGS Publications Warehouse

Jones, Perry M.

2004-01-01

A calibrated steady-state, finite-difference, ground-waterflow model was constructed to simulate ground-water flow in three glaciofluvial aquifers, defined in this report as the upper, middle, and lower aquifers, in an area of about 114 mi2 surrounding the city of Grand Rapids in north-central Minnesota. The calibrated model will be used by Minnesota Department of Health and communities in the Grand Rapids area in the development of wellhead protection plans for their water supplies. The model was calibrated through comparison of simulated ground-water levels to measured static water levels in 351 wells, and comparison of simulated base-flow rates to estimated base-flow rates for reaches of the Mississippi and Prairie Rivers. Model statistics indicate that the model tends to overestimate ground-water levels. The root mean square errors ranged from +12.83 ft in wells completed in the upper aquifer to +19.10 ft in wells completed in the middle aquifer. Mean absolute differences between simulated and measured water levels ranged from +4.43 ft for wells completed in the upper aquifer to +9.25 ft for wells completed in the middle aquifer. Mean algebraic differences ranged from +9.35 ft for wells completed in the upper aquifer to +14.44 ft for wells completed in the middle aquifer, with the positive differences indicating that the simulated water levels were higher than the measured water levels. Percentage errors between simulated and estimated base-flow rates for the three monitored reaches all were less than 10 percent, indicating good agreement. Simulated ground-water levels were most sensitive to changes in general-head boundary conductance, indicating that this characteristic is the predominant model input variable controlling steady-state water-level conditions. Simulated groundwater flow to stream reaches was most sensitive to changes in horizontal hydraulic conductivity, indicating that this characteristic is the predominant model input variable controlling

Spatial Dynamic Optimization of Groundwater Use with Ecological Standards for Instream Flow

NASA Astrophysics Data System (ADS)

Brozovic, N.; Han, J.; Speir, C.

2011-12-01

Instream flow requirements for protected species in arid and semi-arid regions have created the need to reduce groundwater use adjacent to streams. We present an integrated hydrologic-economic model that optimizes agricultural groundwater use next to streams with flow standards. Policies to meet instream flow standards should aim to minimize the welfare losses to irrigated agriculture due to reduced pumping. Previous economic studies have proposed spatially targeted water allocations between groundwater irrigators and instream demands. However, these studies focused on meeting aggregate instream flow goals on a seasonal or yearly basis rather than meeting them on a continuous basis. Temporally aggregated goals ignore important intra-seasonal hydrologic effects and may not provide sufficient habitat quality for species of concern. We present an optimization model that solves for groundwater pumping allocations across space in a stream-aquifer system with instream flow goals that must be met on a daily basis. We combine an analytical model of stream depletion with a farm profit maximization model that includes cumulative crop yield damages from water stress. The objective is the minimization of agricultural losses from reduced groundwater use while minimum instream flow requirements for ecological needs are met on a daily basis. As a case study, we apply our model to the Scott River Basin in northern California. This is a region where stream depletion resulting from extensive irrigation has degraded habitat for Coho salmon, a species protected under the U.S. Endangered Species Act. Our results indicate the importance of considering the lag between the time at which pumping occurs and the time at which stream depletion related to that pumping occurs. In general, we find that wells located farther from the stream should be allocated more water in most hydrologic scenarios. However, we also find that the spatial and temporal distribution of optimal groundwater pumping

Looking Deeper Into Hydrologic Connectivity and Streamflow Generation: A Groundwater Hydrologist's Perspective.

NASA Astrophysics Data System (ADS)

Gardner, W. P.

2016-12-01

In this presentation the definition of hydraulic connection will be explored with a focus on the role of deep groundwater in streamflow generation and its time and space limits. Regional groundwater flow paths can be important sources of baseflow and potentially event response in surface water systems. This deep groundwater discharge plays an important role in determining how the watershed responds to climatic forcing, whether watersheds are a carbon source or sink and can be significant for watershed geochemistry and nutrient loading. These flow paths potentially "connect" to surface water systems and saturated soil zones at large distances, and over long time scales. However, these flow paths are challenging to detect, especially with hydraulic techniques. Here we will discuss some of the basic physical processes that affect the hydraulic signal along a groundwater flow path and their implications for the definition of hydrologic connection. Methods of measuring hydraulic connection using groundwater head response and their application in detecting regional groundwater discharge will be discussed. Environmental tracers are also a powerful method for identifying connected flowpaths in groundwater systems, and are commonly used to determine flow connection and flow rates in groundwater studies. Isotopic tracer methods for detecting deep, regional flow paths in watersheds will be discussed, along with observations of deep groundwater discharge in shallow alluvial systems around the world. The goal of this talk is to discuss hydraulic and hydrologic connection from a groundwater hydrologist's perspective, spark conversation on the meaning of hydrologic connection, the processes which govern hydraulic response and methods to measure flow connections and flux.

Groundwater Flow Model of Göksu Delta Coastal Aquifer System

NASA Astrophysics Data System (ADS)

Erdem Dokuz, Uǧur; Çelik, Mehmet; Arslan, Şebnem; Engin, Hilal

2016-04-01

Like many other coastal areas, Göksu Delta (Mersin-Silifke, Southern Turkey) is a preferred place for human settlement especially due to its productive farmlands and water resources. The water dependent ecosystem in Göksu delta hosts about 332 different plant species and 328 different bird species besides serving for human use. Göksu Delta has been declared as Special Environmental Protection Zone, Wildlife Protection Area, and RAMSAR Convention for Wetlands of International Importance area. Unfortunately, rising population, agricultural and industrial activities cause degradation of water resources both by means of quality and quantity. This problem also exists for other wetlands around the world. It is necessary to prepare water management plans by taking global warming issues into account to protect water resources for next generations. To achieve this, the most efficient tool is to come up with groundwater management strategies by constructing groundwater flow models. By this aim, groundwater modeling studies were carried out for Göksu Delta coastal aquifer system. As a first and most important step in all groundwater modeling studies, geological and hydrogeological settings of the study area have been investigated. Göksu Delta, like many other deltaic environments, has a complex structure because it was formed with the sediments transported by Göksu River throughout the Quaternary period and shaped throughout the transgression-regression periods. Both due to this complex structure and the lack of observation wells penetrating deep enough to give an idea of the total thickness of the delta, it was impossible to reveal out the hydrogeological setting in a correct manner. Therefore, six wells were drilled to construct the conceptual hydrogeological model of Göksu Delta coastal aquifer system. On the basis of drilling studies and slug tests that were conducted along Göksu Delta, hydrostratigraphic units of the delta system have been obtained. According to

Modeling the Death Valley regional ground-water flow system

USGS Publications Warehouse

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

2004-01-01

The development of a regional ground-water flow model of the Death Valley region in the southwestern United States is discussed in the context of the fourteen guidelines of Hill. This application of the guidelines demonstrates how they may be used for model calibration and evaluation, and to direct further model development and data collection.

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.

Simulation of the ground-water flow system at Naval Submarine Base Bangor and vicinity, Kitsap County, Washington

USGS Publications Warehouse

Heeswijk, Marijke van; Smith, Daniel T.

2002-01-01

An evaluation of the interaction between ground-water flow on Naval Submarine Base Bangor and the regional-flow system shows that for selected alternatives of future ground-water pumping on and near the base, the risk is low that significant concentrations of on-base ground-water contamination will reach off-base public-supply wells and hypothetical wells southwest of the base. The risk is low even if worst-case conditions are considered ? no containment and remediation of on-base contamination. The evaluation also shows that future saltwater encroachment of aquifers below sea level may be possible, but this determination has considerable uncertainty associated with it. The potential effects on the ground-water flow system resulting from four hypothetical ground-water pumping alternatives were considered, including no change in 1995 pumping rates, doubling the rates, and 2020 rates estimated from population projections with two different pumping distributions. All but a continuation of 1995 pumping rates demonstrate the possibility of future saltwater encroachment in the Sea-level aquifer on Naval Submarine Base Bangor. The amount of time it would take for encroachment to occur is unknown. For all pumping alternatives, future saltwater encroachment in the Sea-level aquifer also may be possible along Puget Sound east and southeast of the base. Future saltwater encroachment in the Deep aquifer also may be possible throughout large parts of the study area. Projections of saltwater encroachment are least certain outside the boundaries of Naval Submarine Base Bangor. The potential effects of the ground-water pumping alternatives were evaluated by simulating the ground-water flow system with a three-dimensional uniform-density ground-water flow model. The model was calibrated by trial-and-error by minimizing differences between simulated and measured or estimated variables. These included water levels from prior to January 17, 1977 (termed 'predevelopment'), water

Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event

NASA Astrophysics Data System (ADS)

Malott, Spencer; O'Carroll, Denis M.; Robinson, Clare E.

2016-07-01

Dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters. In this study, field data are presented that show, for the first time, the influence of a period of intensified wave conditions (wave event) on nearshore groundwater flows and geochemistry in a sandy beach. Field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines (e.g., tides). Pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations. The groundwater flows were simulated in FEFLOW using a phase-averaged wave setup approach to represent waves acting on the sediment-water interface. Comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave-induced perturbations in groundwater flows. While prior studies have shown sharp pH and redox spatial zonations in nearshore aquifers, this study reveals rapid temporal variations in conductivity, pH, and redox (ORP) in shallow sediments (up to 0.5 m depth) in response to varying wave conditions. Comparison of head gradients with calculated conductivity and pH mixing ratios indicates the controlling effect of the wave-induced water exchange and flows in driving the observed geochemical dynamics. While we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes, the pH and ORP variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers.

Simulation of groundwater flow and pumping scenarios for 1900–2050 near Mount Pleasant, South Carolina

USGS Publications Warehouse

Fine, Jason M.; Petkewich, Matthew D.; Campbell, Bruce G.

2017-10-31

Groundwater withdrawals from the Upper Cretaceous-age Middendorf aquifer in South Carolina have created a large, regional cone of depression in the potentiometric surface of the Middendorf aquifer in Charleston and Berkeley Counties, South Carolina. Groundwater-level declines of as much as 249 feet have been observed in wells over the past 125 years and are a result of groundwater use for public water supply, irrigation, and private industry. To address the concerns of users of the Middendorf aquifer, the U.S. Geological Survey, in cooperation with Mount Pleasant Waterworks (MPW), recalibrated an existing groundwater-flow model to incorporate additional groundwater-use and water-level data since 2008. This recalibration process consisted of a technique of parameter estimation that uses regularized inversion and employs “pilot points” for spatial hydraulic property characterization. The groundwater-flow system of the Coastal Plain physiographic province of South Carolina and parts of Georgia and North Carolina was simulated using the U.S. Geological Survey finite-difference computer code MODFLOW-2000.After the model recalibration, the following six predictive water-management scenarios were created to simulate potential changes in groundwater flow and groundwater-level conditions in the Mount Pleasant, South Carolina, area: Scenario 1—maximize MPW reverse-osmosis plant capacity by increasing groundwater withdrawals from the Middendorf aquifer from 3.9 million gallons per day (Mgal/d), which was the amount withdrawn in 2015, to 8.58 Mgal/d; Scenario 2—same as Scenario 1, but with the addition of a 0.5 Mgal/d supply well in the Middendorf aquifer near Moncks Corner, South Carolina; Scenario 3—same as Scenario 1, but with the addition of a 1.5 Mgal/d supply well in the Middendorf aquifer near Moncks Corner, South Carolina; Scenario 4—maximize MPW well capacity by increasing withdrawals from the Middendorf aquifer from 3.9 Mgal/d (in 2015) to 10.16 Mgal

Tracking the Subsurface Signal of Decadal Climate Warming to Quantify Vertical Groundwater Flow Rates

NASA Astrophysics Data System (ADS)

Bense, V. F.; Kurylyk, B. L.

2017-12-01

Sustained ground surface warming on a decadal time scale leads to an inversion of thermal gradients in the upper tens of meters. The magnitude and direction of vertical groundwater flow should influence the propagation of this warming signal, but direct field observations of this phenomenon are rare. Comparison of temperature-depth profiles in boreholes in the Veluwe area, Netherlands, collected in 1978-1982 and 2016 provided such direct measurement. We used these repeated profiles to track the downward propagation rate of the depth at which the thermal gradient is zero. Numerical modeling of the migration of this thermal gradient "inflection point" yielded estimates of downward groundwater flow rates (0-0.24 m a-1) that generally concurred with known hydrogeological conditions in the area. We conclude that analysis of inflection point depths in temperature-depth profiles impacted by surface warming provides a largely untapped opportunity to inform sustainable groundwater management plans that rely on accurate estimates of long-term vertical groundwater fluxes.

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.

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.

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.

Groundwater-flow model of the northern High Plains aquifer in Colorado, Kansas, Nebraska, South Dakota, and Wyoming

USGS Publications Warehouse

Peterson, Steven M.; Flynn, Amanda T.; Traylor, Jonathan P.

2016-12-13

The High Plains aquifer is a nationally important water resource underlying about 175,000 square miles in parts of eight states: Colorado, Kansas, Oklahoma, Nebraska, New Mexico, South Dakota, Texas, and Wyoming. Droughts across much of the Northern High Plains from 2001 to 2007 have combined with recent (2004) legislative mandates to elevate concerns regarding future availability of groundwater and the need for additional information to support science-based water-resource management. To address these needs, the U.S. Geological Survey began the High Plains Groundwater Availability Study to provide a tool for water-resource managers and other stakeholders to assess the status and availability of groundwater resources.A transient groundwater-flow model was constructed using the U.S. Geological Survey modular three-dimensional finite-difference groundwater-flow model with Newton-Rhapson solver (MODFLOW–NWT). The model uses an orthogonal grid of 565 rows and 795 columns, and each grid cell measures 3,281 feet per side, with one variably thick vertical layer, simulated as unconfined. Groundwater flow was simulated for two distinct periods: (1) the period before substantial groundwater withdrawals, or before about 1940, and (2) the period of increasing groundwater withdrawals from May 1940 through April 2009. A soil-water-balance model was used to estimate recharge from precipitation and groundwater withdrawals for irrigation. The soil-water-balance model uses spatially distributed soil and landscape properties with daily weather data and estimated historical land-cover maps to calculate spatial and temporal variations in potential recharge. Mean annual recharge estimated for 1940–49, early in the history of groundwater development, and 2000–2009, late in the history of groundwater development, was 3.3 and 3.5 inches per year, respectively.Primary model calibration was completed using statistical techniques through parameter estimation using the parameter

Groundwater flow in the transition zone between freshwater and saltwater: a field-based study and analysis of measurement errors

NASA Astrophysics Data System (ADS)

Post, Vincent E. A.; Banks, Eddie; Brunke, Miriam

2018-02-01

The quantification of groundwater flow near the freshwater-saltwater transition zone at the coast is difficult because of variable-density effects and tidal dynamics. Head measurements were collected along a transect perpendicular to the shoreline at a site south of the city of Adelaide, South Australia, to determine the transient flow pattern. This paper presents a detailed overview of the measurement procedure, data post-processing methods and uncertainty analysis in order to assess how measurement errors affect the accuracy of the inferred flow patterns. A particular difficulty encountered was that some of the piezometers were leaky, which necessitated regular measurements of the electrical conductivity and temperature of the water inside the wells to correct for density effects. Other difficulties included failure of pressure transducers, data logger clock drift and operator error. The data obtained were sufficiently accurate to show that there is net seaward horizontal flow of freshwater in the top part of the aquifer, and a net landward flow of saltwater in the lower part. The vertical flow direction alternated with the tide, but due to the large uncertainty of the head gradients and density terms, no net flow could be established with any degree of confidence. While the measurement problems were amplified under the prevailing conditions at the site, similar errors can lead to large uncertainties everywhere. The methodology outlined acknowledges the inherent uncertainty involved in measuring groundwater flow. It can also assist to establish the accuracy requirements of the experimental setup.

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

USGS Publications Warehouse

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

2012-01-01

A numerical transient model of the surficial and Floridan aquifer systems in east-central Florida was developed to (1) increase the understanding of water exchanges between the surficial and the Floridan aquifer systems, (2) assess the recharge rates to the surficial aquifer system from infiltration through the unsaturated zone and (3) obtain a simulation tool that could be used by water-resource managers to assess the impact of changes in groundwater withdrawals on spring flows and on the potentiometric surfaces of the hydrogeologic units composing the Floridan aquifer system. The hydrogeology of east-central Florida was evaluated and used to develop and calibrate the groundwater flow model, which simulates the regional fresh groundwater flow system. The U.S. Geological Survey three-dimensional groundwater flow model, MODFLOW-2005, was used to simulate transient groundwater flow in the surficial, intermediate, and Floridan aquifer systems from 1995 to 2006. The East-Central Florida Transient model encompasses an actively simulated area of about 9,000 square miles. Although the model includes surficial processes-rainfall, irrigation, evapotranspiration (ET), runoff, infiltration, lake water levels, and stream water levels and flows-its primary purpose is to characterize and refine the understanding of groundwater flow in the Floridan aquifer system. Model-independent estimates of the partitioning of rainfall into ET, streamflow, and aquifer recharge are provided from a water-budget analysis of the surficial aquifer system. The interaction of the groundwater flow system with the surface environment was simulated using the Green-Ampt infiltration method and the MODFLOW-2005 Unsaturated-Zone Flow, Lake, and Streamflow-Routing Packages. The model is intended to simulate the part of the groundwater system that contains freshwater. The bottom and lateral boundaries of the model were established at the estimated depths where the chloride concentration is 5,000 milligrams

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

USGS Publications Warehouse

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

2012-01-01

A numerical transient model of the surficial and Floridan aquifer systems in east-central Florida was developed to (1) increase the understanding of water exchanges between the surficial and the Floridan aquifer systems, (2) assess the recharge rates to the surficial aquifer system from infiltration through the unsaturated zone and (3) obtain a simulation tool that could be used by water-resource managers to assess the impact of changes in groundwater withdrawals on spring flows and on the potentiometric surfaces of the hydrogeologic units composing the Floridan aquifer system. The hydrogeology of east-central Florida was evaluated and used to develop and calibrate the groundwater flow model, which simulates the regional fresh groundwater flow system. The U.S. Geological Survey three-dimensional groundwater flow model, MODFLOW-2005, was used to simulate transient groundwater flow in the surficial, intermediate, and Floridan aquifer systems from 1995 to 2006. The east-central Florida transient model encompasses an actively simulated area of about 9,000 square miles. Although the model includes surficial processes-rainfall, irrigation, evapotranspiration, runoff, infiltration, lake water levels, and stream water levels and flows-its primary purpose is to characterize and refine the understanding of groundwater flow in the Floridan aquifer system. Model-independent estimates of the partitioning of rainfall into evapotranspiration, streamflow, and aquifer recharge are provided from a water-budget analysis of the surficial aquifer system. The interaction of the groundwater flow system with the surface environment was simulated using the Green-Ampt infiltration method and the MODFLOW-2005 Unsaturated-Zone Flow, Lake, and Streamflow-Routing Packages. The model is intended to simulate the part of the groundwater system that contains freshwater. The bottom and lateral boundaries of the model were established at the estimated depths where the chloride concentration is 5

Geohydrology and Numerical Simulation of the Ground-Water Flow System of Molokai, Hawaii

USGS Publications Warehouse

Oki, Delwyn S.

1997-01-01

A two-dimensional, steady-state, areal ground-water flow model was developed for the island of Molokai, Hawaii, to enhance the understanding of (1) the conceptual framework of the ground-water flow system, (2) the distribution of aquifer hydraulic properties, and (3) the regional effects of ground-water withdrawals on water levels and coastal discharge. The model uses the finite-element code AQUIFEM-SALT, which simulates flow of fresh ground water in systems that may have a freshwater lens floating on denser underlying saltwater. Model results are in agreement with the general conceptual model of the flow system on Molokai, where ground water flows from the interior, high-recharge areas to the coast. The model-calculated ground-water divide separating flow to the northern and southern coasts lies to either the north or the south of the topographic divide but is generally not coincident with the topographic divide. On the basis of model results, the following horizontal hydraulic conductivities were estimated: (1) 1,000 feet per day for the dike-free volcanic rocks of East and West Molokai, (2) 100 feet per day for the marginal dike zone of the East Molokai Volcano, (3) 2 feet per day for the West Molokai dike complex, (4) 0.02 feet per day for the East Molokai dike complex, and (5) 500 feet per day for the Kalaupapa Volcanics. Three simulations to determine the effects of proposed ground-water withdrawals on water levels and coastal discharge, relative to model-calculated water levels and coastal discharge for 1992-96 withdrawal rates, show that the effects are widespread. For a withdrawal rate of 0.337 million gallons per day from a proposed well about 4 miles southeast of Kualapuu and 3 miles north of Kamiloloa, the model-calculated drawdown of 0.01 foot or more extends 4 miles southeast and 6 miles northwest from the well. For a withdrawal rate of 1.326 million gallons per day from the same well, the model-calculated drawdown of 0.01 foot or more extends 6 miles

Possible changes in ground-water flow to the Pecos River caused by Santa Rosa Lake, Guadalupe County, New Mexico

USGS Publications Warehouse

Risser, D.W.

1987-01-01

In 1980 Santa Rosa Dam began impounding water on the Pecos River about 7 miles north of Santa Rosa, New Mexico, to provide flood control, sediment control, and storage for irrigation. Santa Rosa Lake has caused changes in the groundwater flow system, which may cause changes in the streamflow of the Pecos River that cannot be detected at the present streamflow gaging stations. Data collected at these stations are used to measure the amount of water available for downstream users. A three-dimensional groundwater flow model for a 950 sq mi area between Anton Chico and Puerto de Luna was used to simulate the effects of Santa Rosa Lake on groundwater flow to a gaining reach of the Pecos River for lake levels of 4,675, 4,715, 4,725, 4,750, 4,776, and 4,797 feet above sea level and durations of impoundment of 30, 90, 182, and 365 days for all levels except 4 ,797 feet. These simulations indicated that streamflow in the Pecos River could increase by as much as 2 cu ft/sec between the dam and Puerto de Luna if the lake level were maintained at 4 ,797 feet for 90 days or 4,776 feet for 1 year. About 90% of this increased streamflow would occur < 0.5 mi downstream from the dam, some of which would be measured at the streamflow gaging station located 0.2 mile downstream from the dam. Simulations also indicated that the lake will affect groundwater flow such that inflow to the study area may be decreased by as much as 1.9 cu ft/sec. This water may leave the Pecos River drainage basin or be diverted back to the Pecos River downstream from the gaging station near Puerto de Luna. In either case, this quantity represents a net loss of water upstream from Puerto de Luna. Most simulations indicated that the decrease in groundwater flow into the study area would be of about the same quantity as the simulated increase in streamflow downstream from the dam. Therefore, the net effect of the lake on the flow of the Pecos River in the study area appears to be negligible. Model simulations

Ambient groundwater flow diminishes nitrate processing in the hyporheic zone of streams

NASA Astrophysics Data System (ADS)

Azizian, Morvarid; Boano, Fulvio; Cook, Perran L. M.; Detwiler, Russell L.; Rippy, Megan A.; Grant, Stanley B.

2017-05-01

Modeling and experimental studies demonstrate that ambient groundwater reduces hyporheic exchange, but the implications of this observation for stream N-cycling is not yet clear. Here we utilize a simple process-based model (the Pumping and Streamline Segregation or PASS model) to evaluate N-cycling over two scales of hyporheic exchange (fluvial ripples and riffle-pool sequences), ten ambient groundwater and stream flow scenarios (five gaining and losing conditions and two stream discharges), and three biogeochemical settings (identified based on a principal component analysis of previously published measurements in streams throughout the United States). Model-data comparisons indicate that our model provides realistic estimates for direct denitrification of stream nitrate, but overpredicts nitrification and coupled nitrification-denitrification. Riffle-pool sequences are responsible for most of the N-processing, despite the fact that fluvial ripples generate 3-11 times more hyporheic exchange flux. Across all scenarios, hyporheic exchange flux and the Damköhler Number emerge as primary controls on stream N-cycling; the former regulates trafficking of nutrients and oxygen across the sediment-water interface, while the latter quantifies the relative rates of organic carbon mineralization and advective transport in streambed sediments. Vertical groundwater flux modulates both of these master variables in ways that tend to diminish stream N-cycling. Thus, anthropogenic perturbations of ambient groundwater flows (e.g., by urbanization, agricultural activities, groundwater mining, and/or climate change) may compromise some of the key ecosystem services provided by streams.

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.

The use of groundwater age as a calibration target

USGS Publications Warehouse

Konikow, Leonard F.; Hornberger, G.Z.; Putnam, L.D.; Shapiro, A.M.; Zinn, B.A.

2008-01-01

Groundwater age (or residence time), as estimated on the basis of concentrations of one or more environmental tracers, can provide a useful and independent calibration target for groundwater models. However, concentrations of environmental tracers are affected by the complexities and mixing inherent in groundwater flow through heterogeneous media, especially in the presence of pumping wells. An analysis of flow and age distribution in the Madison aquifer in South Dakota, USA, illustrates the additional benefits and difficulties of using age as a calibration target. Alternative numerical approaches to estimating travel time and age with backward particle tracking are assessed, and the resulting estimates are used to refine estimates of effective porosity and to help assess the adequacy and credibility of the flow model.

Flow, affect and visual creativity.

PubMed

Cseh, Genevieve M; Phillips, Louise H; Pearson, David G

2015-01-01

Flow (being in the zone) is purported to have positive consequences in terms of affect and performance; however, there is no empirical evidence about these links in visual creativity. Positive affect often--but inconsistently--facilitates creativity, and both may be linked to experiencing flow. This study aimed to determine relationships between these variables within visual creativity. Participants performed the creative mental synthesis task to simulate the creative process. Affect change (pre- vs. post-task) and flow were measured via questionnaires. The creativity of synthesis drawings was rated objectively and subjectively by judges. Findings empirically demonstrate that flow is related to affect improvement during visual creativity. Affect change was linked to productivity and self-rated creativity, but no other objective or subjective performance measures. Flow was unrelated to all external performance measures but was highly correlated with self-rated creativity; flow may therefore motivate perseverance towards eventual excellence rather than provide direct cognitive enhancement.

Groundwater similarity across a watershed derived from time-warped and flow-corrected time series

NASA Astrophysics Data System (ADS)

Rinderer, M.; McGlynn, B. L.; van Meerveld, H. J.

2017-05-01

Information about catchment-scale groundwater dynamics is necessary to understand how catchments store and release water and why water quantity and quality varies in streams. However, groundwater level monitoring is often restricted to a limited number of sites. Knowledge of the factors that determine similarity between monitoring sites can be used to predict catchment-scale groundwater storage and connectivity of different runoff source areas. We used distance-based and correlation-based similarity measures to quantify the spatial and temporal differences in shallow groundwater similarity for 51 monitoring sites in a Swiss prealpine catchment. The 41 months long time series were preprocessed using Dynamic Time-Warping and a Flow-corrected Time Transformation to account for small timing differences and bias toward low-flow periods. The mean distance-based groundwater similarity was correlated to topographic indices, such as upslope contributing area, topographic wetness index, and local slope. Correlation-based similarity was less related to landscape position but instead revealed differences between seasons. Analysis of variance and partial Mantel tests showed that landscape position, represented by the topographic wetness index, explained 52% of the variability in mean distance-based groundwater similarity, while spatial distance, represented by the Euclidean distance, explained only 5%. The variability in distance-based similarity and correlation-based similarity between groundwater and streamflow time series was significantly larger for midslope locations than for other landscape positions. This suggests that groundwater dynamics at these midslope sites, which are important to understand runoff source areas and hydrological connectivity at the catchment scale, are most difficult to predict.

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

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.

2016-07-29

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.

Hydrogeology and water quality of the Pepacton Reservoir Watershed in southeastern New York. Part 4. Quantity and quality of ground-water and tributary contributions to stream base flow in selected main-valley reaches

USGS Publications Warehouse

Heisig, Paul M.

2004-01-01

constituents such as nutrients.The total gain in streamflow from the upper end to the lower end of each valley reach was positively correlated with the annual-runoff volume calculated for the drainage area of the reach. This correlation was not greatly affected by the proportions of ground-water and tributary contributions, except at two reaches that lost much of their tributary flow after the July survey. In these reaches, the gain in total streamflow showed a negative departure from this correlation.Calculated ground-water discharge exceeded the total tributary inflow in each valley reach in both surveys. Groundwater discharge, as a percentage of streamflow gain, was greatest among reaches in wide valleys (about 1,000-ft wide valley floors) that contain permeable valley fill because tributary flows were seasonally diminished or absent as a result of streambed infiltration. Tributary inflows, as a percentage of streamflow gain, were highest in reaches of narrow valleys (200-500-ft wide valley floors) with little valley fill and high annual runoff.Stream-water and ground-water quality were characterized by major-ion type as either (1) naturally occurring water types, relatively unaffected by road salt, or (2) road-salt-affected water types having elevated concentrations of chloride and sodium. The naturally occurring waters were typically the calcium-bicarbonate type, but some contained magnesium and (or) sulfate as secondary ions. Magnesium concentration in base flow is probably related to the amount of till and its carbonate content, or to the amount of lime used on cultivated fields within a drainage area. Sulfate was a defining ion only in dilute waters (with short or unreactive flow paths) with low concentrations of bicarbonate. Nearly all tributary waters were classified as naturally occurring water types.Ground-water discharge from nearly all valley reaches that contain State or county highways had elevated concentrations of chloride and sodsodium. The mean chloride

The characteristics of hydrogeochemical zonation of groundwater in inland plain

NASA Astrophysics Data System (ADS)

Xin-yu, HOU; Li-ting, XING; Yi, YANG; Wen-jing, ZHANG; Guang-yao, CHI

2018-05-01

To find out the hydrochemical zoning of groundwaterin the inland plain, taking Jiyang plain as an example, based on mathematical statistics, ion ratio coefficient and isotopic analysis method, the characteristics of water chemical composition and its zoning at different depths of 500m were studied. The result shows: ①The groundwater flow system in the study area can be divided into local flow system, intermediate flow system and regional flow system. ②The hydrochemical type of shallow groundwater is complex. The hydrochemical types of middle confined water are mainly ClṡSO4—MgṡNa and SO4ṡCl—NaṡMg. The deep confined water is mainly HCO3. ③The TDS of shallow groundwater increases gradually along the direction of groundwater flow. ④The shallow saltwater and freshwater are alternately distributed in horizontal direction, and saltwater is distributed sporadically in the interfluve area with sporadic punctate or banded, and hydrochemical types are mainly ClṡSO4—NaṡMgṡCa. Conclusion: Groundwater in the study area is affected by complicated hydrogeochemical action, mainly in the form of filtration, cation exchange and evaporation. The inland plain area is characterized by hydrogeochemical zonation in horizontal and vertical.

Flow pattern and residence time of groundwater within the south-eastern Taoudeni sedimentary basin (Burkina Faso, Mali)

NASA Astrophysics Data System (ADS)

Huneau, F.; Dakoure, D.; Celle-Jeanton, H.; Vitvar, T.; Ito, M.; Traore, S.; Compaore, N. F.; Jirakova, H.; Le Coustumer, P.

2011-10-01

SummaryThe knowledge about groundwater flow conditions within the Southeastern Taoudeni Basin Aquifer shared by Burkina Faso and Mali is relatively limited with very little information on potentiometric heads, recharge processes, residence time and water quality. A better evaluation of groundwater resources in this area is a strategic point for water resources management in the entire Soudano-Sahelian region which endures since the beginning of the twentieth century a continuous decrease in precipitation amount. This paper provides a transboundary synthesis using water ( 18O, 2H and 3H) and carbon isotopes ( 13C and 14C) in conjunction with hydrogeological and hydrochemical data. The objectives are to improve the conceptual model of groundwater recharge and flow within this sandstone reservoir, and to assess the changes in the aquifer due to water abstraction and recent climate changes including an insight into Sahelian aquifers palaeorecharge processes. The local meteoric water line for the Bobo-Dioulasso station is proposed: δ 2H = 8.0 (±0.5)δ 18O + 10.2 (±2.1). Two main tendencies can be derived from groundwater chemistry. First, a slight evolution from the Ca-Mg-HCO 3 type towards a Na-K-HCO 3 type that indicates developed interactions between groundwater and clay minerals related to the residence time of groundwater. A second tendency towards Cl-NO 3-SO 4-HCO 3 water types indicates the anthropogenic influence on groundwater related to the poor sanitary conditions observed around wells. The carbon-14 activity measured on the TDIC varies between 0.3 and 122 pmC, so our record contains samples covering a wide period from Actual to Pleistocene suggesting a continuous recharge of the system through time even if the Sahel region has endured many different climate phases which have influenced the infiltration and recharge processes. All groundwater samples have stable isotope compositions in the range of the present day regional and global meteoric water line

Estimation of groundwater flow from temperature monitoring in a borehole heat exchanger during a thermal response test

NASA Astrophysics Data System (ADS)

Yoshioka, Mayumi; Takakura, Shinichi; Uchida, Youhei

2018-05-01

To estimate the groundwater flow around a borehole heat exchanger (BHE), thermal properties of geological core samples were measured and a thermal response test (TRT) was performed in the Tsukuba upland, Japan. The thermal properties were measured at 57 points along a 50-m-long geological core, consisting predominantly of sand, silt, and clay, drilled near the BHE. In this TRT, the vertical temperature in the BHE was also monitored during and after the test. Results for the thermal properties of the core samples and from the monitoring indicated that groundwater flow enhanced thermal transfers, especially at shallow depths. The groundwater velocities around the BHE were estimated using a two-dimensional numerical model with monitoring data on temperature changes. According to the results, the estimated groundwater velocity was generally consistent with hydrogeological data from previous studies, except for the data collected at shallow depths consisting of a clay layer. The reasons for this discrepancy at shallow depths were predicted to be preferential flow and the occurrence of vertical flow through the BHE grout, induced by the hydrogeological conditions.

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

Preliminary evaluation of ground-water flow in Bear Creek Valley, the Oak Ridge Reservation, Tennessee

USGS Publications Warehouse

Bailey, Z.C.

1988-01-01

Bear Creek Valley, Tennessee contains hazardous waste disposal sites where contaminants leach into ground and surface water. Groundwater flow and the potential migration of contaminants is poorly understood. The Valley is underlain by calcareous shale that contains limestone units. Ridges to the north and south are underlain by interbedded sandstones, siltstone and shale, and by massive, siliceous dolomite, respectively. The bedrock, which dips about 45 degrees southeast, is overlain by regolith to a maximum thickness of 80 ft. Observed hydraulic conductivities for the regolith range from 0.01 to 13 ft/day, and for the bedrock, from 0.001 to 11 ft/day. Groundwater flow is probably toward streams and is preferential along strike because of an areal anisotropy in hydraulic conductivity. A cross sectional groundwater flow model was used to test the conceptualized flow system and to help identify areas where additional data are needed. The preliminary model shows a pattern of recharge at both ridges, flow toward the valley, and upward flow that discharges into Bear Creek. Final model values of hydraulic conductivity in the bedrock range from 0.01 to 0.1 ft/day and reflect an areal anisotropy ratio of 1:5. Simulated recharge was 10 inches/year. (USGS)

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

USGS Publications Warehouse

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

2011-01-01

A numerical flow model (MODFLOW) of the groundwater flow system in the primary aquifers in northern Arizona was developed to simulate interactions between the aquifers, perennial streams, and springs for predevelopment and transient conditions during 1910 through 2005. Simulated aquifers include the Redwall-Muav, Coconino, and basin-fill aquifers. Perennial stream reaches and springs that derive base flow from the aquifers were simulated, including the Colorado River, Little Colorado River, Salt River, Verde River, and perennial reaches of tributary streams. Simulated major springs include Blue Spring, Del Rio Springs, Havasu Springs, Verde River headwater springs, several springs that discharge adjacent to major Verde River tributaries, and many springs that discharge to the Colorado River. Estimates of aquifer hydraulic properties and groundwater budgets were developed from published reports and groundwater-flow models. Spatial extents of aquifers and confining units were developed from geologic data, geophysical models, a groundwater-flow model for the Prescott Active Management Area, drill logs, geologic logs, and geophysical logs. Spatial and temporal distributions of natural recharge were developed by using a water-balance model that estimates recharge from direct infiltration. Additional natural recharge from ephemeral channel infiltration was simulated in alluvial basins. Recharge at wastewater treatment facilities and incidental recharge at agricultural fields and golf courses were also simulated. Estimates of predevelopment rates of groundwater discharge to streams, springs, and evapotranspiration by phreatophytes were derived from previous reports and on the basis of streamflow records at gages. Annual estimates of groundwater withdrawals for agriculture, municipal, industrial, and domestic uses were developed from several sources, including reported withdrawals for nonexempt wells, estimated crop requirements for agricultural wells, and estimated per

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

Using radon to understand parafluvial flows and the changing locations of groundwater inflows in the Avon River, southeast Australia

NASA Astrophysics Data System (ADS)

Cartwright, Ian; Hofmann, Harald

2016-09-01

Understanding the location and magnitude of groundwater inflows to rivers is important for the protection of riverine ecosystems and the management of connected groundwater and surface water systems. This study utilizes 222Rn activities and Cl concentrations in the Avon River, southeast Australia, to determine the distribution of groundwater inflows and to understand the importance of parafluvial flow on the 222Rn budget. The distribution of 222Rn activities and Cl concentrations implies that the Avon River contains alternating gaining and losing reaches. The location of groundwater inflows changed as a result of major floods in 2011-2013 that caused significant movement of the floodplain sediments. The floodplain of the Avon River comprises unconsolidated coarse-grained sediments with numerous point bars and sediment banks through which significant parafluvial flow is likely. The 222Rn activities in the Avon River, which are locally up to 3690 Bq m-3, result from a combination of groundwater inflows and the input of water from the parafluvial zone that has high 222Rn activities due to 222Rn emanation from the alluvial sediments. If the high 222Rn activities were ascribed solely to groundwater inflows, the calculated net groundwater inflows would exceed the measured increase in streamflow along the river by up to 490 % at low streamflows. Uncertainties in the 222Rn activities of groundwater, the gas transfer coefficient, and the degree of hyporheic exchange cannot explain a discrepancy of this magnitude. The proposed model of parafluvial flow envisages that water enters the alluvial sediments in reaches where the river is losing and subsequently re-enters the river in the gaining reaches with flow paths of tens to hundreds of metres. Parafluvial flow is likely to be important in rivers with coarse-grained alluvial sediments on their floodplains and failure to quantify the input of 222Rn from parafluvial flow will result in overestimating groundwater inflows

Biogeochemistry of Arsenic in Groundwater Flow Systems: The Case of Southern Louisiana

NASA Astrophysics Data System (ADS)

Johannesson, K. H.; Yang, N.; Datta, S.

2017-12-01

Arsenic (As) is a highly toxic and carcinogenic metalloid that can cause serious health effects, including increased risk of cancers, infant mortality, and reduced intellectual and motor function in children to populations chronically exposed to As. Recent estimates suggest that more than 140 million people worldwide are drinking As-contaminated groundwater (i.e., As ≥ 10 µg kg-1), and the most severely affected region is the Ganges-Brahmaputra-Meghna delta in Bangladesh and India (i.e., Bengal Basin). Arsenic appears to be mobilized to Bengal Basin groundwaters by reductive dissolution of Fe oxides in aquifer sediments with the source of the labile organic matter occurring in the aquifer sediments. Studies within the lower Mississippi River delta of southern Louisiana (USA) also reveal high As concentrations (up to 640 µg kg-1) in shallow groundwaters. It is not known what affects, if any, the elevated groundwater As has had on local communities. The regional extent of high As shallow groundwaters is controlled, in part, by the distribution of Holocene sediments, deltaic deposits, and organic-rich sediments, similar to the Bengal Basin. Field and laboratory studies suggest that As is largely of geogenic origin, and further that microbial reduction of Fe(III)/Mn(IV) oxides/oxyhydroxides within the sediments contributes the bulk of the As to the groundwaters. Incubation studies are supported by biogeochemical reactive transport modeling, which also indicates reductive dissolution of metal oxides/oxyhydroxides as the likely source of As to these groundwaters. Finally, reactive transport modeling of As in shallow groundwaters suggests that sorption to aquifer mineral surfaces limits the transport of As after mobilization, which may explain, in part, the heterogeneous distribution of As in groundwaters of southern Louisiana and, perhaps, the Bengal Basin.

The Effects of Different Scales of Topographic Variation on Shallow Groundwater Flow in an Arctic Watershed

NASA Astrophysics Data System (ADS)

Nicholaides, K. D.; O'Connor, M.; Cardenas, M. B.; Neilson, B. T.; Kling, G. W.

2017-12-01

Arctic permafrost degradation is occurring as global temperatures increase. In addition, recent evidence shows the Arctic is shifting from a sink to a source of carbon to the atmosphere. However, the cause of this shift is unclear, as is the role of newly exposed organic soil carbon leaching into groundwater and transported to surface water. This soil carbon may be photo-oxidized to CO2 or microbially respired to CO2 and methane, adding greenhouse gases to the atmosphere. The fate of carbon in permafrost is largely governed by the length of time spent in transport and the surface or subsurface route it follows. However, groundwater flow regimes within shallow active layer aquifers overlying permafrost is poorly understood. We determined to what extent smaller scale topography influences groundwater flow and residence times in arctic tundra. The study focused on Imnavait Creek watershed, a 1st-order drainage on the Alaskan North Slope underlain by continuous permafrost. We used direct measurements of hydraulic conductivities and porosities over a range of depths as well as basin-scale topography to develop vertically-integrated groundwater flow models. By systematically decreasing the amount of topographic detail, we were able to compare the influence of more detailed topography on groundwater flow estimates. Scaling up this model will be a useful tool in understanding how larger basins in permafrost will respond to future climate change and their contributions to greenhouse gases in the atmosphere.

Grid refinement in Cartesian coordinates for groundwater flow models using the divergence theorem and Taylor's series.

PubMed

Mansour, M M; Spink, A E F

2013-01-01

Grid refinement is introduced in a numerical groundwater model to increase the accuracy of the solution over local areas without compromising the run time of the model. Numerical methods developed for grid refinement suffered certain drawbacks, for example, deficiencies in the implemented interpolation technique; the non-reciprocity in head calculations or flow calculations; lack of accuracy resulting from high truncation errors, and numerical problems resulting from the construction of elongated meshes. A refinement scheme based on the divergence theorem and Taylor's expansions is presented in this article. This scheme is based on the work of De Marsily (1986) but includes more terms of the Taylor's series to improve the numerical solution. In this scheme, flow reciprocity is maintained and high order of refinement was achievable. The new numerical method is applied to simulate groundwater flows in homogeneous and heterogeneous confined aquifers. It produced results with acceptable degrees of accuracy. This method shows the potential for its application to solving groundwater heads over nested meshes with irregular shapes. © 2012, British Geological Survey © NERC 2012. Ground Water © 2012, National GroundWater Association.

Simulation of ground-water flow in the Saginaw Aquifer, Clinton, Eaton, and Ingham counties, Michigan

USGS Publications Warehouse

Holtschlag, David J.; Luukkonen, Carol L.; Nicholas, J.R.

1996-01-01

A numerical model was developed to simulate ground-water flow in the Tri-County region, which consists of Clinton, Eaton, and Ingham Counties, Michigan. This region includes a nine-township area surrounding Lansing, Michigan. The model simulates the regional response of the Saginaw aquifer to major groundwater withdrawals associated with public-supply wells. The Saginaw aquifer, which is in the Grand River and Saginaw Formations of Pennsylvanian age, is the primary source of ground water for Tri-County residents. The Saginaw aquifer is overlain by glacial deposits, which also are important ground-water sources in some locations. Flow in the Saginaw aquifer and the glacial deposits is simulated by discretizing the flow system into model cells arranged in two layers. Each cell, which corresponds to a land area of 0.0625 square mile, represents the locally averaged properties of the system. The spatial variation of hydraulic properties controlling ground-water flow was estimated by geostatistical analysis of 4,947 well logs. Parameter estimation, a form of nonlinear regression, was used to calibrate the flow model. Results of steady-state ground-water-flow simulations show close agreement between water flowing into and out of the model area for 1992 pumping conditions; standard error of the difference between simulated and measured heads is 14.7 feet. Simulation results for three alternative pumping scenarios for the year 2020 show that the glacial aquifer could be dewatered in places if hypothetical increases in pumping are not distributed throughout the Tri-County region. Contributing areas to public-supply wells in the nine-township area were delineated by a particle-tracking analysis. These areas cover about 121 square miles. Contributing areas for particles having travel times of 40 years or less cover about 42 square miles. Results of tritium sampling support results of model simulations to delineate contributing areas.

Stream-Groundwater Interactions Along Streams of the Eastern Sierra Nevada, California: Implications for Assessing Potential Impacts of Flow Diversions

Treesearch

G. Mathias Kondolf

1989-01-01

One of the most fundamental hydrologic determinations to be made in assessing the probable impacts of flow diversions on riparian vegetation is whether flows are gaining or losing water to groundwater in the reach of interest. Flow measurements on eight streams in the Owens River and Mono Lake basins show that stream- groundwater interactions can produce substantial...

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.

Assessing the hydrogeochemical processes affecting groundwater pollution in arid areas using an integration of geochemical equilibrium and multivariate statistical techniques.

PubMed

El Alfy, Mohamed; Lashin, Aref; Abdalla, Fathy; Al-Bassam, Abdulaziz

2017-10-01

Rapid economic expansion poses serious problems for groundwater resources in arid areas, which typically have high rates of groundwater depletion. In this study, integration of hydrochemical investigations involving chemical and statistical analyses are conducted to assess the factors controlling hydrochemistry and potential pollution in an arid region. Fifty-four groundwater samples were collected from the Dhurma aquifer in Saudi Arabia, and twenty-one physicochemical variables were examined for each sample. Spatial patterns of salinity and nitrate were mapped using fitted variograms. The nitrate spatial distribution shows that nitrate pollution is a persistent problem affecting a wide area of the aquifer. The hydrochemical investigations and cluster analysis reveal four significant clusters of groundwater zones. Five main factors were extracted, which explain >77% of the total data variance. These factors indicated that the chemical characteristics of the groundwater were influenced by rock-water interactions and anthropogenic factors. The identified clusters and factors were validated with hydrochemical investigations. The geogenic factors include the dissolution of various minerals (calcite, aragonite, gypsum, anhydrite, halite and fluorite) and ion exchange processes. The anthropogenic factors include the impact of irrigation return flows and the application of potassium, nitrate, and phosphate fertilizers. Over time, these anthropogenic factors will most likely contribute to further declines in groundwater quality. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Simulation of cylindrical flow to a well using the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model

USGS Publications Warehouse

Reilly, Thomas E.; Harbaugh, Arlen W.

1993-01-01

Cylindrical (axisymmetric) flow to a well is an important specialized topic of ground-water hydraulics and has been applied by many investigators to determine aquifer properties and determine heads and flows in the vicinity of the well. A recent modification to the U.S. Geological Survey Modular Three-Dimensional Finite-Difference Ground-Water Flow Model provides the opportunity to simulate axisymmetric flow to a well. The theory involves the conceptualization of a system of concentric shells that are capable of reproducing the large variations in gradient in the vicinity of the well by decreasing their area in the direction of the well. The computer program presented serves as a preprocessor to the U.S. Geological Survey model by creating the input data file needed to implement the axisymmetric conceptualization. Data input requirements to this preprocessor are described, and a comparison with a known analytical solution indicates that the model functions appropriately.

Future Flows Hydrology: an ensemble of daily river flow and monthly groundwater levels for use for climate change impact assessment across Great Britain

NASA Astrophysics Data System (ADS)

Prudhomme, C.; Haxton, T.; Crooks, S.; Jackson, C.; Barkwith, A.; Williamson, J.; Kelvin, J.; Mackay, J.; Wang, L.; Young, A.; Watts, G.

2012-12-01

The dataset Future Flows Hydrology was developed as part of the project "Future Flows and Groundwater Levels" to provide a consistent set of transient daily river flow and monthly groundwater levels projections across England, Wales and Scotland to enable the investigation of the role of climate variability on river flow and groundwater levels nationally and how this may change in the future. Future Flows Hydrology is derived from Future Flows Climate, a national ensemble projection derived from the Hadley Centre's ensemble projection HadRM3-PPE to provide a consistent set of climate change projections for the whole of Great Britain at both space and time resolutions appropriate for hydrological applications. Three hydrological models and one groundwater level model were used to derive Future Flows Hydrology, with 30 river sites simulated by two hydrological models to enable assessment of hydrological modelling uncertainty in studying the impact of climate change on the hydrology. Future Flows Hydrology contains an 11-member ensemble of transient projections from January 1951 to December 2098, each associated with a single realisation from a different variant of HadRM3 and a single hydrological model. Daily river flows are provided for 281 river catchments and monthly groundwater levels at 24 boreholes as .csv files containing all 11 ensemble members. When separate simulations are done with two hydrological models, two separate .csv files are provided. Because of potential biases in the climate-hydrology modelling chain, catchment fact sheets are associated with each ensemble. These contain information on the uncertainty associated with the hydrological modelling when driven using observed climate and Future Flows Climate for a period representative of the reference time slice 1961-1990 as described by key hydrological statistics. Graphs of projected changes for selected hydrological indicators are also provided for the 2050s time slice. Limitations associated with

Future Flows Hydrology: an ensemble of daily river flow and monthly groundwater levels for use for climate change impact assessment across Great Britain

NASA Astrophysics Data System (ADS)

Prudhomme, C.; Haxton, T.; Crooks, S.; Jackson, C.; Barkwith, A.; Williamson, J.; Kelvin, J.; Mackay, J.; Wang, L.; Young, A.; Watts, G.

2013-03-01

The dataset Future Flows Hydrology was developed as part of the project "Future Flows and Groundwater Levels'' to provide a consistent set of transient daily river flow and monthly groundwater level projections across England, Wales and Scotland to enable the investigation of the role of climate variability on river flow and groundwater levels nationally and how this may change in the future. Future Flows Hydrology is derived from Future Flows Climate, a national ensemble projection derived from the Hadley Centre's ensemble projection HadRM3-PPE to provide a consistent set of climate change projections for the whole of Great Britain at both space and time resolutions appropriate for hydrological applications. Three hydrological models and one groundwater level model were used to derive Future Flows Hydrology, with 30 river sites simulated by two hydrological models to enable assessment of hydrological modelling uncertainty in studying the impact of climate change on the hydrology. Future Flows Hydrology contains an 11-member ensemble of transient projections from January 1951 to December 2098, each associated with a single realisation from a different variant of HadRM3 and a single hydrological model. Daily river flows are provided for 281 river catchments and monthly groundwater levels at 24 boreholes as .csv files containing all 11 ensemble members. When separate simulations are done with two hydrological models, two separate .csv files are provided. Because of potential biases in the climate-hydrology modelling chain, catchment fact sheets are associated with each ensemble. These contain information on the uncertainty associated with the hydrological modelling when driven using observed climate and Future Flows Climate for a period representative of the reference time slice 1961-1990 as described by key hydrological statistics. Graphs of projected changes for selected hydrological indicators are also provided for the 2050s time slice. Limitations associated with

Concentrations and speciation of arsenic along a groundwater flow-path in the Upper Floridan aquifer, Florida, USA

NASA Astrophysics Data System (ADS)

Haque, S. E.; Johannesson, K. H.

2006-05-01

Arsenic (As) concentrations and speciation were determined in groundwaters along a flow-path in the Upper Floridan aquifer (UFA) to investigate the biogeochemical “evolution“ of As in this relatively pristine aquifer. Dissolved inorganic As species were separated in the field using anion-exchange chromatography and subsequently analyzed by inductively coupled plasma mass spectrometry. Total As concentrations are higher in the recharge area groundwaters compared to down-gradient portions of UFA. Redox conditions vary from relatively oxic to anoxic along the flow-path. Mobilization of As species in UFA groundwaters is influenced by ferric iron reduction and subsequent dissolution, sulfate reduction, and probable pyrite precipitation that are inferred from the data to occur along distinct regions of the flow-path. In general, the distribution of As species are consistent with equilibrium thermodynamics, such that arsenate dominates in more oxidizing waters near the recharge area, and arsenite predominates in the progressively reducing groundwaters beyond the recharge area.

Integrated Water Flow Model (IWFM), A Tool For Numerically Simulating Linked Groundwater, Surface Water And Land-Surface Hydrologic Processes

NASA Astrophysics Data System (ADS)

Dogrul, E. C.; Brush, C. F.; Kadir, T. N.

2006-12-01

The Integrated Water Flow Model (IWFM) is a comprehensive input-driven application for simulating groundwater flow, surface water flow and land-surface hydrologic processes, and interactions between these processes, developed by the California Department of Water Resources (DWR). IWFM couples a 3-D finite element groundwater flow process and 1-D land surface, lake, stream flow and vertical unsaturated-zone flow processes which are solved simultaneously at each time step. The groundwater flow system is simulated as a multilayer aquifer system with a mixture of confined and unconfined aquifers separated by semiconfining layers. The groundwater flow process can simulate changing aquifer conditions (confined to unconfined and vice versa), subsidence, tile drains, injection wells and pumping wells. The land surface process calculates elemental water budgets for agricultural, urban, riparian and native vegetation classes. Crop water demands are dynamically calculated using distributed soil properties, land use and crop data, and precipitation and evapotranspiration rates. The crop mix can also be automatically modified as a function of pumping lift using logit functions. Surface water diversions and groundwater pumping can each be specified, or can be automatically adjusted at run time to balance water supply with water demand. The land-surface process also routes runoff to streams and deep percolation to the unsaturated zone. Surface water networks are specified as a series of stream nodes (coincident with groundwater nodes) with specified bed elevation, conductance and stage-flow relationships. Stream nodes are linked to form stream reaches. Stream inflows at the model boundary, surface water diversion locations, and one or more surface water deliveries per location are specified. IWFM routes stream flows through the network, calculating groundwater-surface water interactions, accumulating inflows from runoff, and allocating available stream flows to meet specified or

Geochemistry and the understanding of ground-water systems

USGS Publications Warehouse

Glynn, Pierre D.; Plummer, Niel

2005-01-01

Geochemistry has contributed significantly to the understanding of ground-water systems over the last 50 years. Historic advances include development of the hydrochemical facies concept, application of equilibrium theory, investigation of redox processes, and radiocarbon dating. Other hydrochemical concepts, tools, and techniques have helped elucidate mechanisms of flow and transport in ground-water systems, and have helped unlock an archive of paleoenvironmental information. Hydrochemical and isotopic information can be used to interpret the origin and mode of ground-water recharge, refine estimates of time scales of recharge and ground-water flow, decipher reactive processes, provide paleohydrological information, and calibrate ground-water flow models. Progress needs to be made in obtaining representative samples. Improvements are needed in the interpretation of the information obtained, and in the construction and interpretation of numerical models utilizing hydrochemical data. The best approach will ensure an optimized iterative process between field data collection and analysis, interpretation, and the application of forward, inverse, and statistical modeling tools. Advances are anticipated from microbiological investigations, the characterization of natural organics, isotopic fingerprinting, applications of dissolved gas measurements, and the fields of reaction kinetics and coupled processes. A thermodynamic perspective is offered that could facilitate the comparison and understanding of the multiple physical, chemical, and biological processes affecting ground-water systems.

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, Niel; 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−1. 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.

Hydrology of the coastal springs ground-water basin and adjacent parts of Pasco, Hernando, and Citrus Counties, Florida

USGS Publications Warehouse

Knochenmus, Lari A.; Yobbi, Dann K.

2001-01-01

The coastal springs in Pasco, Hernando, and Citrus Counties, Florida consist of three first-order magnitude springs and numerous smaller springs, which are points of substantial ground-water discharge from the Upper Floridan aquifer. Spring flow is proportional to the water-level altitude in the aquifer and is affected primarily by the magnitude and timing of rainfall. Ground-water levels in 206 Upper Floridan aquifer wells, and surface-water stage, flow, and specific conductance of water from springs at 10 gaging stations were measured to define the hydrologic variability (temporally and spatially) in the Coastal Springs Ground-Water Basin and adjacent parts of Pasco, Hernando, and Citrus Counties. Rainfall at 46 stations and ground-water withdrawals for three counties, were used to calculate water budgets, to evaluate long-term changes in hydrologic conditions, and to evaluate relations among the hydrologic components. Predictive equations to estimate daily spring flow were developed for eight gaging stations using regression techniques. Regression techniques included ordinary least squares and multiple linear regression techniques. The predictive equations indicate that ground-water levels in the Upper Floridan aquifer are directly related to spring flow. At tidally affected gaging stations, spring flow is inversely related to spring-pool altitude. The springs have similar seasonal flow patterns throughout the area. Water-budget analysis provided insight into the relative importance of the hydrologic components expected to influence spring flow. Four water budgets were constructed for small ground-water basins that form the Coastal Springs Ground-Water Basin. Rainfall averaged 55 inches per year and was the only source of inflow to the Basin. The pathways for outflow were evapotranspiration (34 inches per year), runoff by spring flow (8 inches per year), ground-water outflow from upward leakage (11 inches per year), and ground-water withdrawal (2 inches per year

Simulation of ground-water flow, surface-water flow, and a deep sewer tunnel system in the Menomonee Valley, Milwaukee, Wisconsin

USGS Publications Warehouse

Dunning, C.P.; Feinstein, D.T.; Hunt, R.J.; Krohelski, J.T.

2004-01-01

Numerical models were constructed for simulation of ground-water flow in the Menomonee Valley Brownfield, in Milwaukee, Wisconsin. An understanding of ground-water flow is necessary to develop an efficient program to sample ground water for contaminants. Models were constructed in a stepwise fashion, beginning with a regional, single-layer, analytic-element model (GFLOW code) that provided boundary conditions for a local, eight layer, finite-difference model (MODFLOW code) centered on the Menomonee Valley Brownfield. The primary source of ground water to the models is recharge over the model domains; primary sinks for ground water within the models are surface-water features and the Milwaukee Metropolitan Sewerage District Inline Storage System (ISS). Calibration targets were hydraulic heads, surface-water fluxes, vertical gradients, and ground-water infiltration to the ISS. Simulation of ground-water flow by use of the MODFLOW model indicates that about 73 percent of recharge within the MODFLOW domain circulates to the ISS and 27 percent discharges to gaining surface-water bodies. In addition, infiltration to the ISS comes from the following sources: 36 percent from recharge within the model domain, 45 percent from lateral flow into the domain, 15 percent from Lake Michigan, and 4 percent from other surface-water bodies. Particle tracking reveals that the median traveltime from the recharge point to surface-water features is 8 years; the median time to the ISS is 255 years. The traveltimes to the ISS are least over the northern part of the valley, where dolomite is near the land surface. The distribution of traveltimes in the MODFLOW simulation is greatly influenced by the effective porosity values assigned to the various lithologies.

Using Self Potential and Multiphase Flow Modeling to Optimize Groundwater Pumping

NASA Astrophysics Data System (ADS)

Gasperikova, E.; Zhang, Y.; Hubbard, S.

2008-12-01

Numerical and field hydrological and geophysical studies have been conducted to investigate the impact of groundwater pumping on near-river hydrology for a segment of the Russian River at the Wohler Site, California, which is a riverbed filtration system managed by the Sonoma County Water Agency. Groundwater pumping near streams can cause a creation of unsaturated regions and hence reduce the pumping capacity and change the flow paths. A three-dimensional multiphase flow and transport model can be calibrated to the temperature, and water levels at monitoring wells based on known pumping rates, and the river stage. Streaming (self) potential (SP) is one of the electrokinetic processes that describes the coupled behavior of hydraulic and electrical flow within a porous medium, and is easily measured on the surface or in boreholes. Observing temporal and spatial variations in geophysical signatures provides a powerful approach for monitoring changes in the natural systems due to natural or forced (pumping) system perturbations. Geophysical and hydrological data were collected before, during and after a pumping experiment at the Wohler Site. Using this monitoring dataset, we illustrate how loose coupling between hydrogeological and geophysical (SP) processes and data can be used to calibrate the flow model and to optimize pumping schedules as needed to guide sustainable water resource development.

Numerical simulation of the groundwater-flow system of the Kitsap Peninsula, west-central Washington

USGS Publications Warehouse

Frans, Lonna M.; Olsen, Theresa D.

2016-05-05

A groundwater-flow model was developed to improve understanding of water resources on the Kitsap Peninsula. The Kitsap Peninsula is in the Puget Sound lowland of west-central Washington, is bounded by Puget Sound on the east and by Hood Canal on the west, and covers an area of about 575 square miles. The peninsula encompasses all of Kitsap County, Mason County north of Hood Canal, and part of Pierce County west of Puget Sound. The peninsula is surrounded by saltwater, and the hydrologic setting is similar to that of an island. The study area is underlain by a thick sequence of unconsolidated glacial and interglacial deposits that overlie sedimentary and volcanic bedrock units that crop out in the central part of the study area. Twelve hydrogeologic units consisting of aquifers, confining units, and an underlying bedrock unit form the basis of the groundwater-flow model.Groundwater flow on the Kitsap Peninsula was simulated using the groundwater-flow model, MODFLOW‑NWT. The finite difference model grid comprises 536 rows, 362 columns, and 14 layers. Each model cell has a horizontal dimension of 500 by 500 feet, and the model contains a total of 1,227,772 active cells. Groundwater flow was simulated for transient conditions. Transient conditions were simulated for January 1985–December 2012 using annual stress periods for 1985–2004 and monthly stress periods for 2005–2012. During model calibration, variables were adjusted within probable ranges to minimize differences between measured and simulated groundwater levels and stream baseflows. As calibrated to transient conditions, the model has a standard deviation for heads and flows of 47.04 feet and 2.46 cubic feet per second, respectively.Simulated inflow to the model area for the 2005–2012 period from precipitation and secondary recharge was 585,323 acre-feet per year (acre-ft/yr) (93 percent of total simulated inflow ignoring changes in storage), and simulated inflow from stream and lake leakage was 43

Linking fault pattern with groundwater flow in crystalline rocks at the Grimsel Test Site (Switzerland)

NASA Astrophysics Data System (ADS)

Schneeberger, Raphael; Berger, Alfons; Mäder, Urs K.; Niklaus Waber, H.; Kober, Florian; Herwegh, Marco

2017-04-01

Water flow across crystalline bedrock is of major interest for deep-seated geothermal energy projects as well as for underground disposal of radioactive waste. In crystalline rocks enhanced fluid flow is related to zones of increased permeability, i.e. to fractures that are associated to fault zones. The flow regime around the Grimsel Test Site (GTS, Central Aar massif) was assessed by establishing a 3D fault zone pattern on a local scale in the GTS underground facility (deca-meter scale) and on a regional scale at the surface (km-scale). The study reveals the existence of a dense fault zone network consisting of several km long and few tens of cm to meter wide, sub-vertically oriented major faults that are connected by tens to hundreds of meters long minor bridging faults. This geometrical information was used as input for the generation of a 3D fault zone network model. The faults originate from ductile shear zones that were reactivated as brittle faults under retrograde conditions during exhumation. Embrittlement and associated dilatancy along the faults provide the pathways for today's groundwater flow. Detection of the actual 3D flow paths is, however, challenging since flow seem to be not planar but rather tube-like. Two strategies are applied to constrain the 3D geometry of the flow tubes: (i) Characterization of the groundwater infiltrating into the GTS (location, yield, hydraulic head, and chemical composition) and (ii) stress modelling on the base of the 3D structural model to unravel potential domains of enhanced fluid flow such as fault plane intersections and domains of dilatancy. At the Grimsel Test Site, hydraulic and structural data demonstrate that the groundwater flow is head-driven from the surface towards the GTS located some 450 m below the surface. The residence time of the groundwater in this surface-near section is >60 years as evidenced by absence of detectable tritium. However, hydraulic heads obtained from interval pressure measurements

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

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.

Ground-water geochemistry of the Albuquerque-Belen Basin, central New Mexico

USGS Publications Warehouse

Anderholm, S.K.

1988-01-01

The purpose of this study was to define the areal distribution of different water types, use the distribution to help define the groundwater flow system, and identify processes resulting in differences in groundwater quality in the Albuquerque-Belen Basin in central New Mexico. The chemistry of surface water inflow from adjacent areas, which infiltrates and recharges the aquifer along the basin margin, affects the groundwater quality in the eastern and southeastern areas of the basin. Groundwater in the eastern area generally has a specific conductance less than 400 microsiemens, and calcium and bicarbonate are the dominant ions. Mixing of recharge, groundwater inflow, and surface inflow from adjacent areas, which have different chemical compositions, is the major process affecting groundwater quality in the southwestern, western, and northern areas of the basin. In these areas, there is a large range in specific conductance and distribution of dissolved ions. Groundwater quality in the Rio Grande valley is affected by the infiltration of excess irrigation water. The excess irrigation water generally has a larger specific conductance than other groundwater in the valley, so mixing of these waters results in shallow groundwater generally having larger specific conductance than the deeper groundwater. (USGS)

Numerical Analysis of Ground-Water Flow and Salinity in the Ewa Area, Oahu, Hawaii