Search USGS⌕ Search

SEARCH · Search USGS

Results for “Ground Water”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources
USGS2002

Ground-water quality beneath an urban residential and commercial area, Montgomery, Alabama, 1999-2000

The Black Warrior River aquifer, which is composed of the Coker, Gordo, and Eutaw Formations, supplies more than 50 percent of the ground water used for public water supply in the Mobile River Basin. The city of Montgomery, Alabama, is partially built upon a recharge area for the Black Warrior River aquifer, and is one of many major population centers that depend on the Black Warrior River aquifer for public water supply. To represent the baseline ground-water quality in the Black Warrior River aquifer, water samples were collected from 30 wells located in a low-density residential or rural setting; 9 wells were completed in the Coker Formation, 9 wells in the Gordo Formation, and 12 wells in the Eutaw Formation. To describe the ground-water quality beneath Montgomery, Alabama, water samples also were collected from 30 wells located in residential and commercial areas of Montgomery, Alabama; 16 wells were completed in the Eutaw Formation, 8 wells in alluvial deposits, and 6 wells in terrace deposits. The alluvial and terrace deposits directly overlie the Eutaw Formation with little or no hydraulic separation. Ground-water samples collected from both the rural and urban wells were analyzed for physical properties, major ions, nutrients, metals, volatile organic compounds, and pesticides. Samples from the urban wells also were analyzed for bacteria, chlorofluorocarbons, dissolved gases, and sulfur hexafluoride. Ground-water quality beneath the urban area was compared to baseline water quality in the Black Warrior River aquifer.Compared to the rural wells, ground-water samples from urban wells contained greater concentrations or more frequent detections of chloride and nitrate, and the trace metals aluminium, chromium, cobalt, copper, nickel, and zinc. Pesticides and volatile organic compounds were detected more frequently and in greater concentrations in ground-water samples collected from urban wells than in ground-water samples from rural wells.The Spearman rho test was used to check for statistically significant covariance among urban ground-water quality and land-use type. The number of pesticides and volatile organic compounds detected and concentrations of nickel increased as the percentage of residential land use increased. Greater nickel concentrations also were associated with a greater number of volatile organic compounds detected. As the percentage of commercial land use increased, the numbers of pesticides and volatile organic compounds detected decreased. The number of pesticides detected in the urban ground-water samples increased as concentrations of nitrite plus nitrate increased; the number of pesticides detected and the concentrations of nitrite plus nitrate decreased as the age of the ground water increased. These correlations may indicate that, with time, pesticides and nitrate are removed from the ground-water system by physical, chemical, or biological processes.The effects of surficial geology on the occurrence of pesticides and volatile organic compounds was investigated by calculating frequencies of detection. The detection frequency for pesticides was greater for urban samples collected from wells where the surficial geology is sand than for urban samples collected from wells where the surficial geology is clay. The frequency of detection of volatile organic compounds did not show this relation.

Water-Resources Investigations Report↗
USGS2006

Characterization of surface-water resources in the Great Basin National Park area and their susceptibility to ground-water withdrawals in adjacent valleys, White Pine County, Nevada

Eight drainage basins and one spring within the Great Basin National Park area were monitored continually from October 2002 to September 2004 to quantify stream discharge and assess the natural variability in flow. Mean annual discharge for the stream drainages ranged from 0 cubic feet per second at Decathon Canyon to 9.08 cubic feet per second at Baker Creek. Seasonal variability in streamflow generally was uniform throughout the network. Minimum and maximum mean monthly discharges occurred in February and June, respectively, at all but one of the perennial streamflow sites. Synoptic-discharge, specific-conductance, and water- and air-temperature measurements were collected during the spring, summer, and autumn of 2003 along selected reaches of Strawberry, Shingle, Lehman, Baker, and Snake Creeks, and Big Wash to determine areas where surface-water resources would be susceptible to ground-water withdrawals in adjacent valleys. Comparison of streamflow and water-property data to the geology along each stream indicated areas where surface-water resources likely or potentially would be susceptible to ground-water withdrawals. These areas consist of reaches where streams (1) are in contact with permeable rocks or sediments, or (2) receive water from either spring discharge or ground-water inflow.

Scientific Investigations Report↗
USGS2003

Historical ground-water-flow patterns and trends in iron concentrations in the Potomac-Raritan-Magothy aquifer system in parts of Philadelphia, Pennsylvania, and Camden and Gloucester Counties, New Jersey

The Potomac-Raritan-Magothy (PRM) aquifer system is an important sole-source ground-water supply in Camden and Gloucester Counties, N.J. Elevated iron concentrations are a persistent water-quality problem associated with ground water from the PRM. In Philadelphia, the PRM no longer is usable as a water supply because of highly elevated concentrations of iron (as high as 429 mg/L [milligrams per liter]), manganese (as high as 4 mg/L), and sulfate (as high as 1,720 mg/L). A strongly reducing environment in the PRM in south Philadelphia causes these constituents to be remobilized by reductive dissolution of the aquifer matrix. By the 1920s, ground-water pumping changed the natural ground-water-flow patterns, and ground water flowed toward pumping centers in Philadelphia. By 1940, recharge areas changed from the topographically high areas east of Trenton, N.J., to the outcrop area of the PRM in Philadelphia, and the Delaware River became a source of recharge instead of a point of ground-water discharge. By 1954, the cone of depression caused by pumping at the former Philadelphia Naval Ship Yard (PNSY) exceeded 50 feet below NGVD 29, and the direction of ground-water flow was from New Jersey toward Philadelphia. Because of highly elevated concentrations of iron and manganese, pumping at the former PNSY ceased in the mid-1960s. Beginning about 1951, increased ground-water withdrawals from the PRM in New Jersey reversed the hydraulic gradient so that ground-water flow was from Philadelphia toward New Jersey under the Delaware River, making Philadelphia a recharge area for the PRM aquifer system in parts of Camden and Gloucester Counties. By 1988, water levels in the lower aquifer of the PRM in New Jersey had declined to 103 feet below NAVD 88. In 1943, dissolved iron concentrations ranged from 0.07 to 0.6 mg/L at the former PNSY. By 1967 when the wells at the PNSY were abandoned, dissolved iron concentrations had reached 46 mg/L. Dissolved iron concentrations in water from industrial wells in Philadelphia increased from 0.17 mg/L in 1949 to 19 mg/L in 1979. The concentration of dissolved iron in water from wells screened in the lower aquifer in New Jersey also increased with time. By 1985, dissolved iron concentrations were as high as 16 mg/L for Eagle Point refinery wells.

New Jersey, Pennsylvania↗
USGS2007

Effect of on-site wastewater disposal on quality of ground water and base flow: A pilot study in Chester County, southeastern Pennsylvania, 2005

On-site wastewater disposal has the potential to introduce contaminants into ground water and subsequently, by ground-water discharge, to streams. A pilot study was conducted during 2005 by the U.S. Geological Survey in cooperation with the Chester County Health Department and the Chester County Water Resources Authority to determine if wastewater components, including inorganic constituents and selected organic wastewater compounds, such as detergents, considered to be emerging contaminants, were present in ground water and stream base flow in areas with on-site wastewater disposal. The study area was a small watershed (about 7.1 square miles) of mixed land use drained by Broad Run in central Chester County, Pa. The area is underlain by fractured metamorphic rocks that form aquifers recharged by precipitation. Surface- and ground-water sampling was done in areas with and without on-site wastewater disposal for comparison, including a relatively densely populated village with cesspools and septic systems, a residential area with septic systems, a residential area served by sewers, and agricultural land. Samples were collected in May-June and September 2005 from eight headwater stream sites under base-flow conditions and in June 2005 from eight wells and two springs. Samples were analyzed for major ions, nutrients, boron, bacteria, and a suite of organic wastewater compounds. Several emerging contaminant wastewater compounds, including detergent components, insect repellents, and flame retardants, were detected in base-flow and ground-water samples. Stream base-flow samples generally contained more compounds and higher concentrations of those compounds than did ground-water samples, and of the ground-water samples, samples from springs contained more compounds and higher concentrations than samples from wells. Concentrations of nitrate, chloride, and boron (inorganic constituents associated with wastewater) generally were all elevated in base-flow and ground-water samples in areas with relatively high densities of on-site wastewater disposal (septic systems or cesspools) compared to other areas sampled. Results of this pilot study should be considered preliminary because of limited data.

Pennsylvania↗
USGS2001

Simulation of ground-water flow and transport of chlorinated hydrocarbons at Graces Quarters, Aberdeen Proving Ground, Maryland

Military activity at Graces Quarters, a former open-air chemical-agent facility at Aberdeen Proving Ground, Maryland, has resulted in ground-water contamination by chlorinated hydrocarbons. As part of a ground-water remediation feasibility study, a three-dimensional model was constructed to simulate transport of four chlorinated hydrocarbons (1,1,2,2-tetrachloroethane, trichloroethene, carbon tetrachloride, and chloroform) that are components of a contaminant plume in the surficial and middle aquifers underlying the east-central part of Graces Quarters. The model was calibrated to steady-state hydraulic head at 58 observation wells and to the concentration of 1,1,2,2-tetrachloroethane in 58 observation wells and 101direct-push probe samples from the mid-1990s. Simulations using the same basic model with minor adjustments were then run for each of the other plume constituents. The error statistics between the simulated and measured concentrations of each of the constituents compared favorably to the error statisticst,1,2,2-tetrachloroethane calibration. Model simulations were used in conjunction with contaminant concentration data to examine the sources and degradation of the plume constituents. It was determined from this that mixed contaminant sources with no ambient degradation was the best approach for simulating multi-species solute transport at the site. Forward simulations were run to show potential solute transport 30 years and 100 years into the future with and without source removal. Although forward simulations are subject to uncertainty, they can be useful for illustrating various aspects of the conceptual model and its implementation. The forward simulation with no source removal indicates that contaminants would spread throughout various parts of the surficial and middle aquifers, with the100-year simulation showing potential discharge areas in either the marshes at the end of the Graces Quarters peninsula or just offshore in the estuaries. The simulation with source removal indicates that if the modeling assumptions are reasonable and ground-water cleanup within30 years is important, source removal alone is not a sufficient remedy, and cleanup might not even occur within 100 years.

Water-Resources Investigations Report↗
USGS2005

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

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

Data Series↗
USGS1986

Distribution and mobility of selenium and other trace elements in shallow ground water of the western San Joaquin Valley, California

Samples of shallow ground water that underlies much of the irrigated area in the western San Joaquin Valley of California were analyzed for various major ions and trace elements, including selenium. Concentrations of the major ions generally were similar for ground water collected in the two primary geologic zones--the alluvial fan and basin trough. Soils in the alluvial-fan zone are derived from Coast Range rocks, and soils in the basin-trough zone are from a mixture of Sierra Nevada and Coast Range sources. Most of the variance in concentrations of major ions, as determined by principal components analysis, was associated with ground-water salinity and the dominant ions--magnesium, sodium, sulfate, and chloride. Most of the variance in trace elements was associated with concentrations of boron, molybdenum, selenium, and vanadium, which are present as mobile oxyanions. The concentrations of oxyanions trace elements were significantly correlated (a=0.05) with groundwater salinity, but the correlations between selenium and salinity and molybdenum and salinity were significantly different (a=0.05) in the alluvial-fan geologic zone compared with the basin-trough geologic zone. In addition, selenium concentrations are significantly (a=0.05) higher in the ground water of the alluvial-fan zone than in the basin-trough zone. The evidence suggests that the main factors influencing selenium concentrations in the shallow ground water are the degree of ground-water salinity and the geologic source of the alluvial soil material.

California↗
USGS2007

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

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

Scientific Investigations Report↗
USGS2000

Ground-water microbiology and geochemistry

Up-to-date coverage and a unique, multidisciplinary approach The ongoing effort to protect our valuable ground-water resources necessarily involves scientists and engineers from many disciplines. Ground-Water Microbiology and Geochemistry, Second Edition is designed to bridge the historical lack of communication among these disciplines by detailing-in language that cuts across specialties-the impact of microorganisms and microbial processes on ground-water systems. Carefully revised to reflect the many recent discoveries that have been made in the field, the Second Edition begins with an overview of microbiology, ideal for hydrologists and others who may lack formal training in the field. These initial chapters systematically cover the kinds of microorganisms found in subsurface environments, focusing on their growth, metabolism, genetics, and ecology. The second part of the book offers a hydrologic perspective on how microbial processes affect ground-water geochemistry in pristine systems. It also introduces the different classes of ground-water systems, and gives an overview of techniques for sampling subsurface environments. Readers gain an understanding of biogeochemical cycling in ground-water systems-in coverage unique to this book-and how ground-water chemistry can be used to study microbial processes in aquifer systems. The final section of the book deals with the biodegradation of human-introduced contaminants in ground-water systems, with an up-to-date review of the physiology, biochemistry, and redox conditions that favor biodegradation processes. Ground-Water Microbiology and Geochemistry, Second Edition is important reading for geoscientists, hydrologists, and environmental engineers, as well as for water planners and lawyers involved in environmental issues. It also serves as a compelling text for upper-level undergraduate and graduate courses in ground-water chemistry.

Book↗
USGS2000

Effects of ground-water withdrawals on the Rock River and associated valley aquifer, eastern Rock County, Minnesota

A better understanding of the ground-water and surface-water resources of the Rock River Valley in southwestern Minnesota was needed due to concerns surrounding future reliable sources of water for public supply. The Rock River Valley aquifer consists of a surficial sand and gravel unit that underlies the entire Rock River Valley and a buried sand and gravel unit that is present only in the vicinity of the Luverne Municipal and Airport well fields. The surficial and buried units of the aquifer are separated by a clay and till layer ranging in thickness from 1 to 38 feet. The combined maximum saturated thickness of the aquifer is 52 feet, with a median of 22 feet. The thickness of the buried unit ranges from 3 to 17 feet. Recharge to the Rock River Valley aquifer occurs primarily by infiltration of precipitation to the saturated zone (areal recharge) and by induced infiltration from the Rock River due to withdrawals from supply wells near the river. Discharge from the aquifer occurs primarily as leakage to streams and ground-water evapotranspiration. The water budget for the calibrated steady-state simulation indicated that areal recharge accounts for 38 percent of the sources of water to the Rock River Valley aquifer and leakage from streams contributes 58.7 percent. The largest discharge from the aquifer is leakage to streams, (71.1 percent). The net stream-aquifer leakage is approximately 5 cubic feet per second from the aquifer to the streams. The simulated contributing areas for the wells in the three well fields generally extend to the aquifer boundaries on the west and are generally truncated at the Rock River. The simulated transient water budget for 1996 indicated that the principal sources of water to the aquifer were as follows: (1) winter, spring, and late summer stress periods— leakage from streams and water released from storage and (2) early summer and fall stress periods—areal recharge and leakage from streams. The principal discharges from the aquifer were leakage to streams for all stress periods, ground-water evapotranspiration for the early and late summer stress periods, and addition to storage for the early summer and fall stress periods. The herbicides atrazine, alachlor, metolachlor, acetachlor, and cyanazine, and metabolites of these herbicides, occurred in concentrations of 0.05 to 11.5 micrograms per liter in the Rock River at Luverne during major runoff events following application of herbicides in the spring. Atrazine and metabolites, alachlor ESA (a metabolite of alachlor), metolachlor and metabolites, metolachlor ESA and metolachlor OA, and acetochlor metabolites acetochlor ESA and acetochlor OA, were detected at concentrations of 0.05 to 2.8 micrograms per liter in municipal supply wells less than 500 feet from the river during November 1995 through August 1997. The Rock River is the major source of the herbicides and metabolites. However, concentrations of atrazine and metabolites, alachlor ESA, metolachlor ESA, and metolachlor OA in supply wells may also reflect sources of these herbicides and metabolites in the ground-water contributing areas to the supply wells. Nitrite plus nitrate nitrogen concentrations in supply wells and in the ground-water contributing area to the Luverne Municipal well field were generally less than 1.5 milligrams per liter. Nitrite plus nitrate nitrogen concentrations of 2.4 to 8.5 milligrams per liter in the Rock River in the Rock County Rural Water well field and 14 to 18 milligrams per liter in the ground-water contributing area to the Rock County Rural Water supply wells are not having a substantial affect on nitrite plus nitrate nitrogen concentrations in most supply wells. Isotopic mixing calculations indicate that proportions of river water withdrawn from supply wells less than 500 feet from the river range from 5 to 60 percent of total withdrawals. The Rock River is a gaining stream in most reaches, but is losing water to the aquifer in the vicinity of the Luverne Municipal and Rock County Rural Water well fields, located 150 to 1,500 feet from the river. Simulated streamflow losses due to ground-water withdrawals in the well fields were approximately 2.1 cubic feet per second. Because an average of about 1.5 cubic feet per second of the water pumped by Luverne is returned to the Rock River as wastewater discharge, the net steady-state simulated streamflow loss for the study area is 0.6 cubic feet per second. The streamflow losses as a result of ground-water withdrawals are insignificant in comparison to typical streamflow, and are likely to have a measurable effect on streamflow only during low-flow conditions of less than approximately 10 cubic feet per second. Model results indicate that the additional water withdrawn by wells due to anticipated increased ground-water withdrawals was derived from a decrease in net leakage of ground water from the aquifer to the streams. The simulations indicated that the increased ground-water withdrawals and normal precipitation resulted in an increase in induced infiltration from the Rock River of 0.1 cubic feet per second for the Luverne Municipal well field and 0.3 cubic feet per second for the Rock County Rural Water well field. Maximum drawdowns ranged from 0.5 to 1.4 feet near the three well fields. For drought conditions, the simulated streamflow losses constituted approximately 30 percent and nearly 65 percent of the flows in the Rock River for the Luverne Municipal and Rock County Rural Water well fields, respectively. Maximum drawdowns ranged from 3.8 to 7.0 feet near the three well fields. Transient simulations with anticipated increased ground-water withdrawals and drought conditions indicated declines in hydraulic heads ranging from 0.2 to 0.4 feet per year in the vicinity of the three well fields, except for near the Rock River.

Minnesota↗
USGS1987

Rainfall, ground-water flow, and seasonal movement at Minor Creek landslide, northwestern California: Physical interpretation of empirical relations

Simple ground-water flow analyses can clarify complex empirical relations between rainfall and landslide motion. Here we present detailed data on rainfall, ground-water flow, and repetitive seasonal motion that occurred from 1982 to 1985 at Minor Creek landslide in northwestern California, and we interpret these data in the context of physically based theories. We find that landslide motion is closely regulated by the direction and magnitude of near-surface hydraulic gradients and by waves of pore pressure caused by intermittent rainfall. Diffusive propagation of pore-pressure waves accompanies downward ground-water flow along nearly vertical hydraulic gradients that exist in most of the landslide. Field data combined with a pore-pressure diffusion analysis show that single rainstorms typically produce short-period waves that attenuate before reaching the landslide base. In contrast, seasonal rainfall cycles produce long-period waves that modify basal pore pressures, but only after time lags that range from weeks to months. Such tune lags can depend on antecedent moisture storage and can explain variable delays between the onset of the wet season and seasonal landslide motion. Limit-equilibrium analysis shows that when seasonal pressure waves reach the landslide base, they establish a critical distribution of effective stress that delicately triggers landslide motion. The critical effective-stress balance is extremely sensitive to the direction and magnitude of hydraulic gradients. Although pervasively downward gradients instigate seasonal motion, we infer from theory and limited data that ground water also may circulate locally in near-surface cells. The circulation can further reduce the landslide's frictional strength, particularly in areas of nearly horizontal ground-water flow that occur beneath steep faces of hummocks. Hummocky topography that results from slope instability may therefore cause ground-water flow that perpetuates instability. Diffusive propagation of pore-pressure waves accompanies downward ground-water flow along nearly vertical hydraulic gradients that exist in most of the landslide. Field data combined with a pore-pressure diffusion analysis show that single rainstorms typically produce short-period waves that attenuate before reaching the landslide base. In contrast, seasonal rainfall cycles produce long-period waves that modify basal pore pressures, but only after time lags that range from weeks to months. Such tune lags can depend on antecedent moisture storage and can explain variable delays between the onset of the wet season and seasonal landslide motion. Limit-equilibrium analysis shows that when seasonal pressure waves reach the landslide base, they establish a critical distribution of effective stress that delicately triggers landslide motion. The critical effective-stress balance is extremely sensitive to the direction and magnitude of hydraulic gradients. Although pervasively downward gradients instigate seasonal motion, we infer from theory and limited data that ground water also may circulate locally in near-surface cells. The circulation can further reduce the landslide's frictional strength, particularly in areas of nearly horizontal ground-water flow that occur beneath steep faces of hummocks. Hummocky topography that results from slope instability may therefore cause ground-water flow that perpetuates instability.

California↗
USGS2005

Ground-water availability from surficial aquifers in the Red River of the North Basin, Minnesota

Population growth and commercial and industrial development in the Red River of the North Basin in Minnesota, North Dakota, and South Dakota have prompted the Bureau of Reclamation, U.S. Department of the Interior, to evaluate sources of water to sustain this growth. Nine surficial-glacial (surficial) aquifers (Buffalo, Middle River, Two Rivers, Beach Ridges, Pelican River, Otter Tail, Wadena, Pineland Sands, and Bemidji-Bagley) within the Minnesota part of the basin were identified and evaluated for their ground-water resources. Information was compiled and summarized from published studies to evaluate the availability of ground water. Published information reviewed for each of the aquifers included location and extent, physical characteristics, hydraulic properties, ground-water and surface-water interactions, estimates of water budgets (sources of recharge and discharge) and aquifer storage, theoretical well yields and actual ground-water pumping data, recent (2003) ground-water use data, and baseline ground-water-quality data. Water-budget estimates for the aquifers were compiled from steady-state aquifer simulations, precipitation data and hydrograph analysis, and recharge and discharge information. Major sources of recharge to the aquifers are areal recharge, flow from surface water, and flow across aquifer boundaries from adjacent geologic units. Losses of water from the aquifers include evapotranspiration, flow to surface water, flow across aquifer boundaries, and withdrawals by pumping wells. The Bemidji-Bagley, Otter Tail, Pineland Sands, and Wadena surficial aquifers have the highest rates of water inflow and outflow of the nine aquifers in the study area, and the Middle River surficial aquifer has the lowest rates of total water inflow and outflow. Maximum storage volumes of five of the surficial aquifers were calculated using areal extent and published saturated thickness and porosity data. Storage estimates from published studies were included for three of the surficial aquifers. Maximum theoretical well yields for the aquifers generally occur in areas with more abundant, well-sorted, coarse-grained sediment. In 2003, 28 billion gallons of ground water were withdrawn from the aquifers, not including water used for private supply. In 2003, the largest volume of ground water was withdrawn from the Otter Tail surficial aquifer, and the smallest volume was withdrawn from the the Middle River surficial aquifer. Agricultural irrigation and public supply totaled 95 percent of the volume of ground water withdrawn from the aquifers in 2003. Ground-water-quality data indicate that the Buffalo aquifer contained the largest specific conductance and concentrations of dissolved solids, calcium, magnesium, sodium, sulfate, and iron. Ground water from the Bemidji-Bagley, Otter Tail, Pineland Sands, and Wadena surficial aquifers contained the largest concentrations of nitrate (as nitrogen). In general, the nine aquifers are hydraulically connected to local surface water. Simulations of ground-water development for some of the aquifers describe correlations between increased ground-water withdrawals and declining lake levels and streamflows, lower water-table altitudes, and variations in ground-water quality. On the basis of data and methods presented to evaluate ground-water availability, the Otter Tail and Pineland Sands surficial aquifers and Pelican River sand-plain aquifer have the greatest potential for additional development of ground-water resources in the study area.

Minnesota, North Dakota, South Dakota↗
USGS2006

Ground-Water Contributions to Reservoir Storage and the Effect on Estimates of Firm Yield for Reservoirs in Massachusetts

Potential ground-water contributions to reservoir storage were determined for nine reservoirs in Massachusetts that had shorelines in contact with sand and gravel aquifers. The effect of ground water on firm yield was not only substantial, but furthermore, the firm yield of a reservoir in contact with a sand and gravel aquifer was always greater when the ground-water contribution was included in the water balance. Increases in firm yield ranged from 2 to 113 percent, with a median increase in firm yield of 10 percent. Additionally, the increase in firm yield in two reservoirs was greater than 85 percent. This study identified a set of equations that are based on an analytical solution to the ground-water-flow equation for the case of one-dimensional flow in a finite-width aquifer bounded by a linear surface-water feature such as a stream. These equations, which require only five input variables, were incorporated into an existing firm-yield-estimator (FYE) model, and the potential effect of ground water on firm yield was evaluated. To apply the FYE model to a reservoir in Massachusetts, the model requires that the drainage area to the reservoir be clearly defined and that some surface water flows into the reservoir. For surface-water-body shapes having a more realistic representation of a reservoir shoreline than a stream, a comparison of ground-water-flow rates simulated by the ground-water equations with flow rates simulated by a two-dimensional, finite-difference ground-water-flow model indicate that the agreement between the simulated flow rates is within ?10 percent when the ratio of the distance from the reservoir shoreline to the aquifer boundary to the length of shoreline in contact with the aquifer is between values of 0.5 and 3.5. Idealized reservoir-aquifer systems were assumed to verify that the ground-water-flow equations were implemented correctly into the existing FYE model; however, the modified FYE model has not been validated through a comparison of simulated and observed data. A comparison of simulated and observed reservoir water levels would further define limitations to the applicability of the ground-water-flow equations to reservoirs in Massachusetts whose shorelines are in contact with a sand and gravel aquifer.

Scientific Investigations Report↗
USGS1977

Reconnaissance of ground-water resources in the Mountain Home plateau area, southwest Idaho

The Mountain Home plateau area occupies approximately 1,220 square miles of the western Snake River Plain in southwestern Idaho. About 40,000 acres are presently (1977) irrigated with ground water, about 30,000 acres with surface water. An estimated 450,000 acres are potentially irrigable, if water is available. Development of ground-water re- sources has caused water-level declines in several places. Largest declines are south of Mountain Home, where water levels dropped more than 20 feet in the last 9 years. Ground water in the area occurs primarily under water-table conditions. Perched-water zones are present in several locations. The most productive aquifer in the eastern part of the plateau is basalt of the Bureau Formation of the Idaho Group. In the western part, the most productive aquifers are sand and gravel of the older terrace gravel lithologic unit and the Idaho Group. Recharge to the ground-water system is water from the Boise River drainage basin, precipitation on the plateau and adjacent mountains, and leakage from irrigation structures. Ground-water movement is generally south or southwest. Natural ground-water discharge from the plateau is about 18,000 acre-feet annually. The chemical composition of the ground water generally reflects water characteristics in the area of the source of recharge and, for the most part, is good. Deuterium and oxygen-18 isotope analyses suggest that the water at the lower end of the ground-water flow system underlying the plateau was recharged a long time ago, although climatic conditions then were similar to current conditions in the Boise River basin. Additional large-scale ground-water development will probably result in economically prohibitive pumping lifts, which also would consume excessive amounts of energy. Therefore, large-scale new agricultural development would depend heavily on the availability of surface water. However, one or several deep test holes, in selected places, could help answer some questions about the occurrence of ground water and perhaps encourage further exploration for untapped deep artesian aquifers. The occurrence of perched-water zones beneath lands irrigated by surface water suggests that more zones of this type could develop if water is imported into the area to irrigate additional lands, and if the efficiency of the present distribution systems remains unchanged.

Idaho↗
USGS1952

Preliminary report on ground water in the Michaud Flats Project, Power County, Idaho

The Michaud Flats Project area, as here described, includes about 65 square miles in central Power County, south of the Snake River in the southeastern Snake River Plain of Idaho. The principal town and commercial center of the area is American Falls. The immediate purpose of work in the area by the U.S. Geological Survey was to investigate the possibility of developing substantial quantities of ground water for irrigating high and outlying lands in the proposed Michaud Flats Project area of the U.S. Bureau of Reclamation. Initial findings are sufficiently favorable to warrant comprehensive further investigation. Advanced study would assist proper utilization of ground-water resources and would aid ultimate evaluation of total water resources available in the area. About 10,000 acres of low-lying lands in the Michaud Flats project could be irrigated with water from the Snake River under a low-line distribution system involving a maximum pumping lift of about 200 feet above the river. An additional larger area of high and outlying lands is suitable for irrigation with water pumped from wells. If sufficient ground water is economically available, the expense of constructing and operating a costly highline distribution system for surface water could be saved. Reconnaissance of the ground-water geology of the area disclosed surface outcrops of late Cenozoic sedimentary, pyroclastic, and volcanic rocks. Well logs and test borings show that similar materials are present beneath the land surface in the zone of saturation. Ground water occurs under perched, unconfined, and confined (artesian) conditions, but the aquifers have not been adequately explored. Existing irrigation wells, 300 feet or less in depth, yield several hundred to 1,400 gallons of water a minute, with pumping drawdowns of 6 to 50 feet, and perhaps more. A few wells have been pumped out at rates of less than 800 gallons a minute. Scientific well-construction and development methods would lead to more efficient well performance. A generalized water-table contour map of the area shows that the principal general direction of ground-water movement is toward the west and northwest. The southwestern part of the American Falls Reservoir, and a segment of the Snake River below the dam, may be perched above the water table. Ground water appears to move beneath this segment of the river to the Snake River Plain on the northwest side. So far as is known, recharge to the ground-water reservoir is chiefly from local sources and from the runoff from the mountain area southeast of the project. Seepage losses from surface water spread for irrigation would contribute a substantial amount of new recharge to the ground water, but the amount of such recharge might be less than the depletion of ground water by pumping. Therefore, with ground-water irrigation a part of the project, return flow to the American Falls Reservoir might be less than it is in the existing regimen. Ground-water pumping where the ground water is not tributary to the reservoir might not deplete the reservoir appreciably, but would reduce the net supply of water available west of Neeley. Evidence indicates that at least moderate supplies of ground water can be obtained in low-lying areas southwest and northeast of American Falls, but the safe perennial yields of the aquifers cannot now be estimated. The ground-water potential in high and outlying lands is not known. It is unlikely that this potential is sufficient to supply all high and outlying lands, but the supply may be adequate for a substantial part of these lands. Thorough investigation appears to be warranted.

Open-File Report↗
USGS1977

Elements needed in design of a ground-water-quality monitoring network in the Hawaiian Islands

The elements needed in the design of a ground-water-quality monitoring network in the Hawaiian Islands are described and summarized. The elements are given by geohydrologie units which represent areas where there are similarities in the occurrence of ground water or in the geology pertinent to the occurrence of ground water. The goal is to establish a network of observation points to inventory and maintain surveillance of existing and potential sources of pollution of ground water. Of principal concern to Hawaii's environment is pollution of the potable ground-water supplies and of the near-shore recreational waters, the latter by the discharge of polluted ground water. Existing monitoring efforts, although intensive in many areas, are not adequate because they are geared more toward (1) the detection and surveillance of pollutants in the conveyances of ground water instead of in the sources of ground water and (2) the monitoring of extensive nonpoint sources of pollution instead of from discrete point sources.

Water Supply Paper↗
USGS2007

Hydrogeologic characteristics of the St. Croix River basin, Minnesota and Wisconsin: Implications for the susceptibility of ground water to potential contamination

Population growth in the St. Croix River Basin in Minnesota and Wisconsin has intensified concerns of county resource managers and the National Park Service, which is charged with protecting the St. Croix National Scenic Riverway, about the potential for ground-water contamination in the basin. This report describes a previously developed method that was adapted to illustrate potential ground-water-contamination susceptibility in the St. Croix River Basin. The report also gives an estimate of ground-water-residence time and surface-water/ground-water interaction as related to natural attenuation and movement of contaminants in five tributary basins. A ground-water-contamination-susceptibility map was adapted from a state-wide map of Wisconsin to the St. Croix River Basin by use of well-driller construction records and regional maps of aquifer properties in Minnesota and Wisconsin. Measures of various subsurface properties were combined to generate a spatial index of susceptibility. The subjective index method developed for the State of Wisconsin by Schmidt (1987) 1 was not derived from analyses of water-quality data or physical processes. Nonetheless, it was adapted for this report to furnish a seamless map across state boundaries that would be familiar to many resource managers. Following this method, areas most susceptible to contamination appear to have coarse-grained sediments (sands or gravels) and shallow water tables or are underlain by carbonate-bedrock aquifers. The least susceptible areas appear to have fine-grained sediments and deep water tables. If an aquifer becomes contaminated, the ground-water-residence time can affect potential natural attenuation along the ground-water-flow path. Mean basin ground-water-residence times were computed for the Apple, Kettle, Kinnickinnic, Snake and Sunrise River Basins, which are tributary basins to the St. Croix Basin, by use of average aquifer properties of saturated thickness, porosity, and recharge rates. The Apple River Basin had the shortest mean ground-water-residence times (20–120 years), owing largely to the moderate saturated thickness and high recharge rate in the basin. The Kinnickinnic and Sunrise River Basins had the longest mean residence times (60–350 and 70–390 years, respectively) chiefly because of the relatively large saturated thickness of the basins. Owing to limitations of the residence-time calculations, actual ground-water-residence times will vary around the mean values within each basin and may range from days or weeks in karst carbonate aquifers to millennia in deep confined sandstone aquifers. Areas of relatively short residence time (less than the median residence time in each basin) were identified by use of ground-water-flow models for each of the five tributary basins. Results of simulations show that these areas, in which contaminants may have relatively less time for natural attenuation along the short flow paths, generally occur near streams and rivers where ground water discharges to the surface. Finally, the ground-water-flow models were used to simulate ground-water/surface-water interaction in the five tributary basins. Results of simulations show that some lakes and reservoirs leak surface water into the ground-water-flow system on their downgradient side, where the surface-water outflow has been restricted by a dam or a naturally constricted outlet. These locations are noteworthy because contaminated surface waters could potentially enter the ground-water-flow system at these locations.

Minnesota, Wisconsin↗
USGS1997

Influence of evaporation, ground water, and uncertainty in the hydrologic budget of Lake Lucerne, a seepage lake in Polk County, Florida

Evaporation losses and the interaction of ground water with Lake Lucerne were studied to determine the influence of these two processes on the hydrologic budget of a seepage lake. Lake Lucerne is representative of the numerous seepage lakes of sinkhole origin in the karst terrain of central Florida. Because of permeable surficial deposits, ground-water inflow is the only significant contribution from the surrounding watershed. The lake recharges the underlying Upper Floridan aquifer and, as a result, is susceptible to increased leakage induced by pumping from this aquifer. Ground-water fluxes determined in the study were analyzed to define the proportion of the total lake leakage induced by pumping from the Upper Floridan aquifer. A hydrologic budget is analyzed for the 1-year period from October 1985 to September 1986. Ground-water inflow and leakage are significant components of the hydrologic budget. Changes in the quantity of either of these fluxes can substantially alter lake stage. Ground-water inflow contributed from 20 to 37 percent of the total annual inflow to the lake. Leakage from the lake accounted for 18 to 23 percent of the total annual outflow. Water withdrawals from the Upper Floridan aquifer increased annual lake leakage by 22 percent over nonpumping conditions. Most of the increase (92 percent) in leakage occurred during April, May, and June 1986, when local citrus irrigation was highest. For the study year, ground-water inflow and leakage volumes were calculated by flow-net analysis to be equal to 10.5 and 12.6 inches, respectively, of water depth above (or below) the lake surface. These estimates were revised upward on the basis of an analysis of the error in the hydrologic-budget equation. Revised ground water inflow exceeded annual leakage from the lake. Ground-water inflow rates were increased by 120 percent to 23.6 inches, and leakage was increased by 40 percent to 17.5 inches. Differences between the two estimates probably reflect the uncertainty in the hydraulic conductivity estimates of the porous media around the lake and the unaccounted effect of transient ground-water inflow. The geometry of the sinkhole complex beneath Lake Lucerne and pumping in the Upper Floridan aquifer are primary controls on ground water interactions with the lake and, in particular, lake leakage. A numerical ground-water model was used to test the effects of these two factors on ground-water interactions with the lake. Results indicate that the intermediate confining unit below Lake Lucerne has been breached and replaced by materials about two orders of magnitude more conductive. Anisotropy in the surficial aquifer is approximately 100 and controls the depth of the ground-water flow intercepted by the lake. Lake sediments having low permeability may control the distribution of leakage through the lakebed but did not appreciably reduce total leakage rates in these simulations. Evaporation loss was the major outflow component of the hydrologic budget. Annual lake evaporation determined by the energy-budget method was 57.9 inches, about 8 inches greater than long-term estimates for the region. The greater rate was attributed to drier than normal conditions: rainfall totaled 40.9 inches during the study year, about 10 inches less than the long-term average. Similar annual evaporation rates were determined by the energy-budget method, the simpler mass-transfer method, and by corrected pan evaporation from an onsite pan; however, the probable errors associated with these other two methods were greater than for the energy budget. Weekly energy-budget evaporation rates ranged from 0.04 inch per day in early January 1986 to 0.26 inch per day in early May 1986. The largest monthly energy-budget evaporation rates occurred in April and May 1986, 7.16 and 7.12 inches per month, respectively. Monthly evaporation estimated from corrected pan evaporation generally was within 10 percent of the energy-budget estimate but differed by as much as 35 percent. Daily energy-budget evaporation also was computed for 321 days during the year.

Florida↗