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At least 1,027 records · Page 57Linked to original sources
USGS2008

Distribution and migration of ordnance-related compounds and oxygen and hydrogen stable isotopes in ground water near Snake Pond, Sandwich, Massachusetts

Explosive compounds, such as RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), and the propellant compound perchlorate are present in ground water near Snake Pond, a ground-water flow-through glacial kettle pond in the glacial sand and gravel aquifer on western Cape Cod near Camp Edwards on the Massachusetts Military Reservation. The contaminants originate from the J-3 Range ordnance training and testing area. Ground-water samples were collected at 10 sites near the pond to determine the paths of the contaminants as they underflow or completely or partially discharge into the pond. Water-quality profiles were developed for sites on opposite ends of a 200-foot-long intermittent island near the northern, upgradient end of the pond by collecting water samples from two temporary drive-point borings. RDX was detected at both locations between 60 and 90 feet below the pond level. The highest RDX concentration was 0.99 micrograms per liter. Perchlorate was detected at only one location on the island, between 95 and 100 feet below the pond level at a concentration of 0.61 micrograms per liter. Profiles of oxygen and hydrogen stable isotopes were developed for seven sites spaced 300 to 600 feet apart along the southern, downgradient shore of the pond. A transition from heavier to lighter oxygen and hydrogen isotopes was observed at an altitude of about -50 feet. This transition most likely is the boundary between evaporation-affected pond water that is seeping into the aquifer and ground water that has passed beneath the pond. RDX was not detected in the ground-water samples collected south of the pond. Perchlorate was detected only in one sample from a shallow depth in one boring. The results of these analyses indicate that the J-3 Range plume contains low concentrations of RDX and perchlorate (less than 1 microgram per liter) as it passes beneath the northern end of Snake Pond. Results of ground-water-flow modeling indicate that ground water containing these low levels of RDX and perchlorate discharges into the pond south of the island. If the contaminated ground water should travel as far as the southern shore of the pond, it would be overlain near the shore by a zone of pond water seeping into the aquifer that is about 100 feet thick.

Massachusetts↗
USGS1998

Simulation of ground-water flow and stream-aquifer relations in the vicinity of the Savannah River Site, Georgia and South Carolina, predevelopment through 1992

Ground-water flow and stream-aquifer relations were simulated for seven aquifers in Coastal Plain sediments in the vicinity of the U.S. Department of Energy, Savannah River Site (SRS), in Georgia and South Carolina to evaluate the potential for ground water containing hazardous materials to migrate from the SRS into Georgia through aquifers underlying the Savannah River (trans-river flow). The work was completed as part of a cooperative study between the U.S. Geological Survey, the U.S. Department of Energy, and Georgia Department of Natural Resources. The U.S. Geological Survey three-dimensional finite-difference ground-water flow model, MODFLOW, was used to simulate ground-water flow in three aquifer systems containing seven discrete aquifers: (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, and upper and lower Dublin aquifers in sediments of Paleocene and Late Cretaceous age; and (3) the Midville aquifer system, consisting of the upper and lower Midville aquifers of sediments in Late Cretaceous age. Ground-water flow was simulated using a series of steady-state simulations of predevelopment (pre-1953) conditions and six pumping periods--1953-60, 1961-70, 1971-75, 1976-80, 1981-86, and 1987-92--results are presented for predevelopment (prior to 1953) and modern-day (1987-92) conditions. Total simulated predevelopment inflow is 1,023 million gallons per day (Mgal/d), of which 76 percent is contributed by leakage from the Upper Three Runs aquifer. Over most of the study area, pumpage induced changes in ground-water levels, ground-water discharge to streams, and water-budget components were small during 1953-92, and changes in aquifer storage were insignificant. Simulated drawdown between predevelopment and modern-day conditions is small (less than 7 feet) and of limited areal extent--the largest simulated declines occur in the upper and lower Dublin aquifers in the vicinity of the Sandoz plant site in South Carolina. These declines extend beneath the Savannah River and change the configuration of the simulated potentiometric surface and flow paths near the river. Predevelopment and modern-day flowpaths were simulated near the Savannah River by using the U.S. Geological Survey particle-tracking code MODPATH. Eastward and westward zones of trans-river flow were identified in three principal areas as follows: --zone 1-from the Fall Line southward to the confluence of Hollow Creek and the Savannah River; --zone 2-from the zone 1 boundary southward to the southern border of the SRS (not including the Lower Three Runs Creek section); and --zone 3-from the zone 2 boundary, southward into the northern part of Screven County, Ga. All zones for all model layers were located within or immediately adjacent to the Savannah River alluvial valley and most were located in the immediate vicinity of the Savannah River. Recharge areas for each of the zones of trans-river flow generally are in the vicinity of major interstream drainage divides. Mean time-of-travel simulated for predevelopment conditions ranges from 300 to 24,000 years for westward trans-river flow zones; and from 550 to 41,000 years for eastward zones. Corresponding travel times under modern-day conditions range from 300 to 34,000 years for westward zones and from 580 to 31,000 years for eastward zones. Differences in travel times between predevelopment and modern-day simulations result from changes in hydraulic gradients due to ground-water pumpage that alter flow paths in the vicinity of the river. Recharge to Georgia trans-river flow zones originating on the SRS was simulated for the Gordon and upper Dublin aquifers during predevelopment, and in the Gordon aquifer during 1987-92. During 1987-92, SRS recharge was simulated in 6 model cells covering a 2-square mile area, located away from areas of ground-water contamination. Si

Georgia, South Carolina↗
USGS2006

Sources of High-Chloride Water to Wells, Eastern San Joaquin Ground-Water Subbasin, California

As a result of pumping and subsequent declines in water levels, chloride concentrations have increased in water from wells in the Eastern San Joaquin Ground-Water Subbasin, about 80 miles east of San Francisco (Montgomery Watson, Inc., 2000). Water from a number of public-supply, agricultural, and domestic wells in the western part of the subbasin adjacent to the San Joaquin Delta exceeds the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (SMCL) for chloride of 250 milligrams per liter (mg/L) (fig. 1) (link to animation showing chloride concentrations in water from wells, 1984 to 2004). Some of these wells have been removed from service. High-chloride water from delta surface water, delta sediments, saline aquifers that underlie freshwater aquifers, and irrigation return are possible sources of high-chloride water to wells (fig. 2). It is possible that different sources contribute high-chloride water to wells in different parts of the subbasin or even to different depths within the same well.

Open-File Report↗
USGS2006

Well logging in ground‐water hydrology

In 1966 more than 50 billion gallons of water was pumped daily from an estimated 10 to 15 million water wells in the United States. This was more than one‐sixth of the national withdrawal of water . On the basis of past rates of increase, a much greater future use of ground water is suggested. Our annual investment in water wells is one‐half to three‐quarter billion dollars, not including pumps and plumbing. In 1964 approximately 436,000 new wells were drilled; however, less than 1 percent of these wells were logged by any geophysical means. The application of _ge_o.phy.sical well logging to ground‐water hydrology is comparable to its use in petroleum exploration in the 1930's; however, we can take advantage of equipment and interpretation techniques developed in the oil industry that are available now for use in ground‐water investigations. Although most petroleum well logging techniques may be utilized in hydrology ; modifications in equipment and interpretation are necessary because of basic economic and environmental differences between petroleum and ground‐water evaluation. If logging is to be widely applied to ground‐water exploration and evaluation, the expense of equipment and services must be reduced. Fortunately, this can be accomplished, because most water wells are not as deep as oil wells and the temperatures and pressures are lower. The Water Resources Division of the U. S. Geological Survey is conducting research on the application of borehole geophysics to ground‐water hydrology . The following logging devices are utilized in the evaluation of ground‐water environments: spontaneous potential, resistivity, gamma, gamma‐gamma, neutron, radioactive tracer, flowmeter, caliper, fluid resistivity, gradient and differential temperature, and sonic velocity. Lightweight logging sondes and control modules are operated by one man, either on a vehicle‐mounted 6,000‐foot logger or on a suitcase‐mounted 500‐foot logger. An inexpensive magnetic tape system has been developed and is used routinely for log recording and playback. If commercial well logging service is to be widely used in ground‐water exploration and development, water well contractors, and State and municipal agencies must be educated on the advantages of obtaining more information from each hole drilled. It will be necessary also to demonstrate how well logging can provide much of this information. In addition, the well logging industry must adapt their equipment and services to the requirements of ground‐water hydrology . The need for additional logging capability in this field exists at the present time and is expected to increase. Hopefully industry will be able to fill the gap.

Groundwater↗
USGS1996

Ground-water flow and the potential effects of remediation at Graces Quarters, Aberdeen Proving Ground, Maryland

Ground water in the east-central part of Graces Quarters, a former open-air chemical-agent test facility at Aberdeen Proving Ground, Maryland, is contaminated with chlorinated volatile organic compounds. The U.S. Geological Survey's finite- difference model was used to help understand ground-water flow and simulate the effects of alternative remedial actions to clean up the ground water. Scenarios to simulate unstressed conditions and three extraction well con- figurations were used to compare alternative remedial actions on the contaminant plume. The scenarios indicate that contaminants could migrate from their present location to wetland areas within 10 years under unstressed conditions. Pumping 7 gal/min (gallons per minute) from one well upgradient of the plume will not result in containment or removal of the highest contaminant concentrations. Pumping 7 gal/min from three wells along the central axis of the plume should result in containment and removal of dissolved contami- nants, as should pumping 7 gal/min from three wells at the leading edge of the plume while injecting 7 gal/min back into an upgradient well.

Water-Resources Investigations Report↗
USGS1997

Ground-water geochemistry of Kwajalein Island, Republic of the Marshall Islands, 1991

Ground water on Kwajalein Island is an important source of drinking water, particularly during periods of low rainfall. Fresh ground water is found as a thin lens underlain by saltwater. The concentration of dissolved ions increases with depth below the water table and proximity to the shoreline as high-salinity seawater mixes with fresh ground water. The maximum depth of the freshwater lens is 37 ft. Chloride is assumed to be non-reactive under the range of geochemical conditions on the atoll. The concentration of chloride thus is used as a conservative constituent to evaluate freshwater-saltwater mixing within the aquifer. Concentrations of sodium and for the most part, potassium and sulfate, also appear to be determined by conservative mixing between saltwater and rain. Concentrations of calcium, magnesium, and strontium are higher than expected from conservative mixing; these higher concentrations are a result of the dissolution of carbonate minerals. An excess in dissolved inorganic carbon results from carbonate-mineral dissolution and from the oxidation of organic matter in the aquifer; the stoichiometric difference between excess dissolved inorganic carbon and excess bivalent cations is used as a measure of the amount of organic-matter oxidation. Organic-matter oxidation also is indicated by the low concentration of dissolved oxygen, high concentrations of nutrients, and the presence of hydrogen sulfide in many of the water samples. Low levels of dissolved oxygen indicate oxic respiration, and sulfate reduction is indicated by hydrogen sulfide. The amount of dissolved inorganic carbon released during organic-matter oxidation is nearly equivalent to the amount of carbonate-mineral dissolution. Organic-matter oxidation and carbonate-mineral dissolution seem to be most active either in the unsaturated zone or near the top of the water table. The most plausible explanation is that high amounts of oxic respiration in the unsaturated zone generate carbon dioxide, which causes carbonate minerals to dissolve. Ground water contaminated by petroleum hydrocarbons had the highest levels of mineral dissolution and organic respiration (including sulfate reduction), indicating that bacteria are oxidizing the contaminants.

Kwajalein Island↗
USGS2005

Chemistry of runoff and shallow ground water at the Cattlemans Detention basin site, South Lake Tahoe, California, August 2000-November 2001

A study at the Cattlemans detention basin site began in November 2000. The site is adjacent to Cold Creek in South Lake Tahoe, California. The purpose of the study is to evaluate the effects of the detention basin on ground-water discharge and changes in nutrient loads to Cold Creek, a tributary to Trout Creek and Lake Tahoe. The study is being done in cooperation with the Tahoe Engineering Division of the El Dorado County Department of Transportation. This report summarizes data collected prior to and during construction of the detention basin and includes: (1) nutrient and total suspended solid concentrations of urban runoff; (2) distribution of unconsolidated deposits; (3) direction of ground-water flow; and (4) chemistry of shallow ground water and Cold Creek. Unconsolidated deposits in the area of the detention basin were categorized into three classes: fill material consisting of a red-brown loamy sand with some gravel and an occasional cobble that was placed on top of the meadow; meadow deposits consisting of gray silt and sand with stringers of coarse sand and fine gravel; and a deeper brown to yellow-brown sand and gravel with lenses of silt and sand. Prior to construction of the detention basin, ground water flowed west-northwest across the area of the detention basin toward Cold Creek. The direction of ground-water flow did not change during construction of the detention basin. Median concentrations of dissolved iron and chloride were 500 and 30 times higher, respectively, in ground water from the meadow deposits than dissolved concentrations in Cold Creek. Median concentration of sulfate in ground water from the meadow deposits was 0.4 milligrams per liter and dissolved oxygen was below the detection level of 0.3 milligrams per liter. The relatively high concentrations of iron and the lack of sulfate in the shallow ground water likely are caused by chemical reactions and biological microbial oxidation of organic matter in the unconsolidated deposits that result in little to no dissolved oxygen in the ground water. The higher chloride concentrations in ground water compared with Cold Creek likely are caused from the application of salt on Pioneer Trail and streets in Montgomery Estates subdivision during the winter. Runoff from these roads contributes to the recharge of the shallow ground water. The range of dissolved constituents generally was greater in the meadow deposits than in the deeper sand and gravel. Ammonia plus organic nitrogen were the dominant forms of dissolved nitrogen and concentrations ranged from 0.04 to 18 milligrams per liter as nitrogen. Highest concentration was beneath the middle of the detention basin. Nitrate plus nitrite concentrations were low (<0.33 milligrams per liter as nitrogen) throughout the area and dissolved phosphorus concentrations ranged from 0.001 to 0.34 milligrams per liter. Nitrogen and dissolved organic carbon showed no consistent pattern in the direction of ground-water flow, which suggests that, similar to iron and sulfate, local variations in the chemical and biological reactions within the meadow deposits controlled the variation in nitrogen concentrations. The gradual increase in dissolved phosphorus along the direction of ground-water flow suggest that phosphorus may be slowly dissolving into ground water. Dissolved phosphorus was consistently low in July, which may be the result of greater microbial activity in the unconsolidated deposits or from uptake by roots during the summer.

Scientific Investigations Report↗
USGS2000

A Retrospective Analysis on the Occurrence of Arsenic in Ground-Water Resources of the United States and Limitations in Drinking-Water-Supply Characterizations

The Safe Drinking Water Act, as amended in 1996, requires the U.S. Environmental Protection Agency (USEPA) to review current drinking-water standards for arsenic, propose a maximum contaminant level for arsenic by January 1, 2000, and issue a final regulation by January, 2001. Quantification of the national occurrence of targeted ranges in arsenic concentration in ground water used for public drinking-water supplies is an important component of USEPA's regulatory process. Data from the U.S. Geological Survey (USGS) National Water Information System (NWIS) were used in a retrospective analysis of arsenic in the ground-water resources of the United States. The analysis augments other existing sources of data on the occurrence of arsenic collected in ground water at public water-supply systems.The USGS, through its District offices and national programs, has been compiling data for many years on arsenic concentrations collected from wells used for public water supply, research, agriculture, industry, and domestic water supply throughout the United States. These data have been collected for a variety of purposes ranging from simple descriptions of the occurrence of arsenic in local or regional ground-water resources to detailed studies on arsenic geochemistry associated with contamination sites. A total of 18,864 sample locations were selected from the USGS NWIS data base regardless of well type, of which 2,262 were taken from public water-supply sources. Samples with non-potable water (dissolved-solids concentration greater than 2,000 milligrams per liter and water temperature greater than 50o Celsius) were not selected for the retrospective analysis and other criteria for selection included the amount and type of ancillary data available for each sample. The 1,528 counties with sufficient data included 76 percent of all large public water-supply systems (serving more than 10,000 people) and 61 percent of all small public water-supply systems (serving more than 1,000 and less than 10,000 people) in the United States. The arsenic data were summarized for the selected counties by associating the arsenic concentrations measured in the ground-water resource with the numbers and sizes of public water-supply systems using ground water in those counties. Targeted arsenic concentrations of 1, 2, 5, 10, 20, and 50 ug/L were exceeded in the ground-water resource associated with 36, 25, 14, 8, 3, and 1 percent respectively of all public water-supply systems accounted for in the analysis.Contributions to uncertainty such as changes in sampling methods and changes in laboratory reporting appear to be less important to the national occurrence estimates than other factors such as temporal variability in arsenic concentrations at a given well, the types of wells sampled, and density and types of sampling locations. In addition, no attempt was made to quantify arsenic concentrations in relation to depth within aquifers. With these qualifications, the USGS data represent the ground-water resource in general and are not restricted to wells currently used for public drinking-water sources. In this way, the broad spatial extent, large number of water samples, and low detection limits used for the USGS data provide a unique source of information to determine where targeted concentrations of arsenic are likely to occur in the ground-water resources within much of the United States.These results indicate USGS data can be effectively used to augment national estimates of arsenic occurrence in the nation's ground-water resources if limitations are recognized. Existing estimates of the occurrence of arsenic in ground water that are used as a source of drinking water can be supplemented with the USGS arsenic concentration data when associated with the public water-supply data base. One such supplementary application is the additional insight gained by establishing relations between arsenic concentration data in the ground-water resource and small public wat

Water-Resources Investigations Report↗
USGS1998

Hydrology and geochemistry of a slag-affected aquifer and chemical characteristics of slag-affected ground water, northwestern Indiana and northeastern Illinois

Slag is a by-product of steel manufacturing and a ubiquitous fill material in northwestern Indiana. Ground water associated with slag deposits generally is characterized by high pH and elevated concentrations of many inorganic water-quality constituents. The U.S. Geological Survey, in cooperation with the Indiana Department of Environmental Management, conducted a study in northwestern Indiana from June 1995 to September 1996 to improve understanding of the effects of slag deposits on the water quality of a glacial-outwash aquifer. The Bairstow Landfill, a slag-fill deposit overlying the Calumet aquifer near Hammond, Indiana, was studied to represent conditions in slag-deposit settings that are common in northwestern Indiana. Ground water from 10 observation wells, located in four nests at the site, and surface water from the adjacent Lake George were analyzed for values of field-measured parameters and concentrations of major ions, nutrients, trace elements, and bulk properties. Solid-phase samples of slag and aquifer sediment collected during drilling were examined with X-ray diffraction and geochemical digestion and analysis. Concentrations of calcium, potassium, sodium, and sulfate were highest in wells screened partly or fully in slag. Potassium concentrations in ground water ranged from 2.9 to 120 milligrams per liter (mg/L), were highest in water from slag deposits, and decreased with depth. The highest concentrations for aluminum, barium, molybdenum, nickel, and selenium were in water from the slag. Silica concentrations were highest in wells screened directly beneath the slag-aquifer interface, and magnesium concentrations were highest in intermediate and deep aquifer wells. Silica concentrations in shallow and intermediate aquifer wells ranged from 27 to 41 mg/L and were about 10 times greater than those in water from slag deposits. The highest concentrations for chromium, lead, and zinc were in ground water from immediately below the slag-aquifer interface. The solid-phase analyses indicated that calcite, dolomite, and quartz generally were present throughout the slag-aquifer system; barian celestite, cristobalite, manganese-bearing calcite, and minrecordite were present in fewer samples. Trace elements that are liberated from the slag may be incorporated as impurities during precipitation of major minerals, sorbed onto clays and other grainsize fractions not analyzed as part of this study, or present in low-abundance minerals that were not detected by the X-ray analysis. Mass-balance and speciation programs were used to identify geochemical processes that may be occurring as water infiltrates through the slag, flows into the aquifer, and discharges into Lake George. The geochemical models indicate that precipitation of calcite may be occurring where slag-affected water enters the aquifer. Models also indicate that dolomite precipitation and clay-mineral dissolution may be occurring at the slag-aquifer interface; however, dolomite precipitation is generally believed to require geologically long time periods. Silica may be dissolving where slag-affected ground water enters the aquifer and may be precipitating where slag-affected ground water discharges to the lakebed of Lake George. In addition to the site-specific study, a statistical analysis of regional water quality was done to compare ground water in wells affected and unaffected by slag. When com-pared to wells in background locations in the Calumet aquifer, wells screened in slag across northwestern Indiana and northeastern Illinois generally had relatively higher pH and specific-conductance values and relatively higher concentrations of alkalinity, dissolved solids, suspended solids, total organic carbon, calcium, potassium, sodium, chloride, aluminum, barium, and possibly magnesium, sulfate, chromium, cobalt, copper, cyanide, manganese, mercury, nickel, and vanadium. When compared to wells in slag and wells in background locations, ground water from immediately beneath or immediately downgradient from slag had relatively high concentrations of arsenic and silica. Water-quality characteristics in ground water at the Bairstow Landfill were similar to water-quality characteristics in slag-contact and slag-affected wells throughout northwestern Indiana.

Illinois, Indiana↗
USGS1997

Ground-water resources of the lower-middle Chattahoochee River basin in Georgia and Alabama, and middle Flint River basin in Georgia - Subarea 3 of the Apalachicola-Chattahoochee-Flint and Alabama-Coosa-Tallapoosa River basins

Drought conditions in the 1980's focused attention on the multiple uses of the surface- and ground-water resources in the Apalachicola-Chattahoochee-Flint (ACF) and Alabama-Coosa-Tallapoosa (ACT) River basins in Georgia, Alabama, and Florida. State and Federal agencies also have proposed projects that would require additional water resources and revise operating practices within the river basins. The existing and proposed water projects create conflicting demands for water by the States and emphasize the problem of water-resource allocation. This study was initiated to describe ground-water availability in the lower-middle Chattahoochee River basin of Georgia and Alabama; and middle Flint River basin of Georgia, Subarea 3 of the ACF and ACT River basins, and to estimate the possible effects of increased ground-water use within the basin. Subarea 3 encompasses about 6,180 square miles (mi 2) of the Coastal Plain Province in southwestern Georgia and southeastern Alabama. About 55 percent of the area is drained by the Chattahoochee River, with the remainder drained by the Flint River. The drainage area of the Chattahoochee River is divided almost equally between Alabama and Georgia. Subarea 3 is underlain by complexly interbedded sedimentary strata that dip gently to the southeast, underlying the Floridan aquifer system to the south. The strata comprise numerous porous-media aquifers and confining units that crop out in the northern part of Subarea 3 in generally northeast-trending bands. The conceptual model described for this study qualitatively subdivides the ground-water flow system into local (shallow), intermediate, and regional (deep) flow regimes. Ground-water discharge to tributaries mainly is from local and intermediate flow regimes and varies seasonally. The regional flow regime probably approximates steady-state conditions and discharges chiefly to major drains such as the Chattahoochee River. Ground-water discharge to major drains originates from all flow regimes. Mean-annual baseflow is about 1,618 cubic feet per second (ft 3 /s) in the Chattahoochee River; and about 1,812 ft 3 /s in the Flint River. Of the 1,618 ft 3 /s baseflow in the Chattahoochee, about 37 percent is discharge from Alabama and 63 percent is discharge from Georgia. Near the end of the drought of 1954, baseflow was about 579 ft 3 /s in the Chattahoochee River; and about 963 ft 3 /s in the Flint River. Of the 579 ft 3 /s drought baseflow in the Chattahoochee River, about 15 percent was from Alabama and 85 percent from Georgia. Baseflow in Subarea 3 during the drought of 1954 was about 45 percent of mean-annual baseflow. Near the end of the drought of 1986, baseflow was about 449 ft 3 /s in the Chattahoochee River and about 498 ft 3 /s in the Flint River. Of the 449 ft 3 /s baseflow in the Chattahoochee River, about 16 percent was discharge from Alabama and 84 percent was discharge from Georgia. Baseflow in Subarea 3 during the 1986 drought was about 28 percent of mean-annual baseflow. The potential exists for the development of ground-water resources on a regional scale throughout Subarea 3. Estimated ground-water use in 1990 was about 2.2 percent of the estimated mean-annual baseflow, and ranged from about 4.9 to 8.0 percent of baseflows near the end of the droughts of 1954 and 1986, respectively. Because groundwater use in Subarea 3 represents a relatively minor percentage of ground-water recharge, even a large increase in ground-water use in Subarea 3 in one State is likely to have little effect on ground-water and surface-water occurrence in the other. Indications of long-term ground-water level declines were not observed; however, the number and distribution of observation wells having long-term water-level measurements in Subarea 3 are insufficient to draw conclusions.

Alabama, Georgia↗
USGS1999

Induced infiltration from the Rockaway River and water chemistry in a stratified-drift aquifer at Dover, New Jersey, with a section on modeling ground-water flow in the Rockaway River Valley

The vertical hydraulic conductivity per unit thickness (streambed leakance) of unconsolidated sediment immediately beneath the channel of the Rockaway River near a municipal well field at Dover, N.J., is between 0.2 and 0.6 feet per day per foot and is probably near the low end of this range. This estimate is based on evaluation of three lines of evidence: (1) Streamflow measurements, which indicated that induced infiltration of river water near the well field averaged 0.67 cubic feet per second; (2) measurements of the rate of downward propagation of diurnal fluctuations in dissolved oxygen and water temperature at three piezometers, which indicated vertical Darcian flow velocities of 0.6 and 1.5 feet per day, respectively; and (3) chemical mixing models based on stable isotopes of oxygen and hydrogen, which indicated that 30 percent of the water reaching a well near the center of the well field was derived from the river. The estimated streambed-leakance values are compatible with other aquifer properties and with hydraulic stresses observed over a 2-year period, as demonstrated by a set of six alternative groundwater flow models of the Rockaway River valley. Simulated water levels rose 0.5 to 1.7 feet near the well field when simulated streambed leakance was changed from 0.2 to 0.6 feet per day per foot, or when a former reach of the Rockaway River valley that is now blocked by glacial drift was simulated as containing a continuous sand aquifer (rather than impermeable till). Model recalibration to observed water levels could accommodate either of these changes, however, by plausible adjustments in hydraulic conductivity of 35 percent or less. The ground-water flow models incorporate a new procedure for simulating areal recharge, in which water available for recharge in any time interval is accepted as recharge only where the water level in the uppermost model layer is below land surface. Water rejected as recharge on upland hillsides is allowed to recharge aquifers at the base of the hillsides. Inclusion of uplands in models of valley-fill aquifers and use of the new procedure increases model complexity and data requirements, but automates the simulation of recharge to those aquifers from the uplands, even in transient-state simulations with multiple periods of varied stresses, and facilitates delineation of upland areas that contribute water to well fields. The area from which ground water flowed toward the Dover well field decreased with an increase in simulated streambed leakance or an increase in simulated hydraulic conductivity of upland till. Concentrations of solutes in ground water near the Dover well field reflect the mixing of native ground water with water infiltrated from the Rockaway River. Chemical reactions in the aquifer, chiefly the weathering of carbonate minerals by dissolved carbon dioxide, affect the pH and the concentrations of both solutes and dissolved gases. Concentrations of sodium, chloride, and sulfate appear to be related to man's activities, such as road deicing, or to decay of organic matter in the aquifer.

New Jersey↗
USGS2002

Ground-water quality in the West Salt River Valley, Arizona, 1996–98 — Relations to hydrogeology, water use, and land use

The U.S. Geological Survey collected and analyzed ground-water samples in the West Salt River Valley from 64 existing wells selected by a stratified-random procedure. Samples from an areally distributed group of 35 of these wells were used to characterize overall ground-water quality in the basin-fill aquifer. Analytes included the principal inorganic constituents, trace constituents, pesticides, and volatile organic compounds. Additional analytes were tritium, radon, and stable isotopes of hydrogen and oxygen. Analyses of replicate samples and blank samples provided evidence that the analyses of the ground-water samples were adequate for interpretation. The median concentration of dissolved solids in samples from the 35 wells was 560 milligrams per liter, which exceeded the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level for drinking water. Eleven of the 35 samples had a nitrate concentration (as nitrogen) that exceeded the U.S. Environmental Protection Agency Maximum Contaminant Level for drinking water of 10 milligrams per liter. Pesticides were detected in eight samples; concentrations were below the Maximum Contaminant Levels. Deethylatrazine was most commonly detected. The pesticides were detected in samples from wells in agricultural or urban areas that have been irrigated. Concentrations of all trace constituents, except arsenic, were less than the Maximum Contaminant Levels. The concentration of arsenic exceeded the Maximum Contaminant Level of 50 micrograms per liter in two samples. Nine monitoring wells were constructed in an area near Buckeye to assess the effects of agricultural land use on shallow ground water. The median concentration of dissolved solids was 3,340 milligrams per liter in samples collected from these wells in August 1997. The nitrate concentration (as nitrogen) exceeded the Maximum Contaminant Level (10 milligrams per liter) in samples from eight of the nine monitoring wells in August 1997 and again in February 1998. Analyses of all samples collected from the monitoring wells indicated low concentrations of pesticides and volatile organic compounds. The most frequently detected pesticides were deethylatrazine and atrazine. Trichloromethane (chloroform) and tetrachloroethene (PCE) were the most frequently detected volatile organic compounds in the monitoring wells. Two compounds [dieldrin and 1,1-dichloro-2,2-bis(p-dichlorodiphenyl)ethylene (DDE)], decomposition products of two banned pesticides, aldrin and dichlorodiphenylethylene (DDT), were detected at low concentrations in samples analyzed for the agricultural land-use study. In the West Salt River Valley, a high concentration of the heavier oxygen isotope?oxygen-18?in ground water generally indicates effects of evaporation on recharge water from irrigation. Wells in undeveloped areas and wells that have openings beneath a confining bed generally yield ground water that is free of the effects of irrigation seepage. Samples from these wells did not contain detectable concentrations of pesticides. The median concentrations of nitrate (as nitrogen) and dissolved solids in samples from wells in undeveloped areas were 1.7 milligrams per liter and 257 milligrams per liter, respectively. The median concentrations of nitrate (as nitrogen) and dissolved solids in samples from wells that yield water from below confining beds were 2.0 and 747 milligrams per liter, respectively.

Arizona↗
USGS1966

Hydrochemical facies and ground-water flow patterns in northern part of Atlantic Coastal Plain

The part of the Atlantic Coastal Plain that extends from New Jersey through Virginia was selected as a suitable field model in which to study the relationships between geology, hydrology, and chemical character of ground water. The ground-water flow pattern is the principal hydrologic control on the chemical character of the water. Within the Coastal Plain sediments, the proportions of clay, glauconitic sand, and calcareous material are the principal lithologic controls over the chemistry of the water. A subsurface body of salt water extends from southern New Jersey through southern Virginia and occupies the deposits deeper than about 500 feet below land surface in the eastern part of the Coastal Plain. The position of its top is determined by the relative head, which in turn is influenced by topography, drainage density, and the thickness and permeability of the Coastal Plain sediments. Hydrochemical facies is a term used in this paper to denote the diagnostic chemical aspect of ground-water solutions occurring in hydrologic systems. The facies reflect the response of chemical processes operating within the lithologic framework and also the pattern of flow of the water. The distribution of these facies is shown in trilinear diagrams and isometric fence diagrams and on maps showing isopleths of chemical constituents within certain formations. The occurrence of the various facies within one formation or within a group of formations of uniform mineralogy indicates that the ground-water flow through the aquifer system modifies the distribution of the facies. Flow patterns of fresh ground water shown on maps and in cross sections have been deduced from available water-level data. These patterns are controlled by the distribution of the higher landmasses and by the depth to either bedrock or to the salt-water interface. The mapping of hydrochemical facies shows that at shallow depths within the Coastal Plain (less than about 200 ft) the calcium-magnesium cation facies generally predominates. The bicarbonate anion facies occurs within more of the shallow Coastal Plain sediments than does the sulfate or the chloride facies. In deeper formations, the sodium chloride character predominates. The lower dissolved-solids content of the ground water in New Jersey indicates less upward vertical leakage than in Maryland and Virginia, where the shallow formations contain solutions of higher concentration.

Delaware, Maryland, New Jersey, Pennsylvania, Virg↗
USGS1997

Statistical analysis of nitrate in ground water, West Salt River Valley, Arizona

Accurate estimates of the nitrate concentrations in ground water in west Salt River Valley are needed to better manage ground water affected by nitrate. Statistical analyses were done to establish the best statistical method to produce these estimates. Three sets of ground-water data for different time periods --1975-77, 1980-85, and 1986-90--were used to analyze spatial and temporal variations in concentrations of nitrate in ground water. The use of inverse-distance squared weighting, radial-basis function, kriging, and cokriging were evaluated for estimating nitrate concentrations in ground water. From an analysis of the cross-validation results, cokriging maps resulted in the best estimates, and they were accepted as being the most reliable. Cross-validation results also indicated that nitrate cokriged best with magnesium for 1975-77 and 1986-90 and with calcium for 1980-85. Kriging results consistently were almost as reliable as any of the cokriging results. Because of the difficulties inherent in the cokriging process, kriging, although not optimal, was the fastest way to obtain reasonably good results. In 1980-85, cokriged nitrate concentrations exceeded 20 milligrams per liter in a 12-square-kilometer area in Phoenix and Glendale and exceeded 10 milligrams per liter in a 280-square-kilometer area that extended to the Salt River. In 1986-90, nitrate concentrations along the entire reach of the Salt River in west Salt River Valley were less than 10 milligrams per liter and were smaller probably as a result of recharge from the Salt and Gila Rivers in 1982. Farther north in Phoenix and Glendale, the area in which nitrate concentrations exceeded 10 milligrams per liter expanded to 490 square kilometers for 1986-90. In Buckeye Valley, nitrate concentrations exceeded 10 milligrams per liter in an area of 300 square milometers for 1980-85 from the Gila River in the early 1980's but possibly could be an artifact of the different data distributions associated with each data set. In the Phoenix area, cokriged nitrate concentrations for 1975-77 exceeded 10 milligrams per liter in a 290-square-kilometer area and exceeded 20 milligrams per liter in a 1.4-square- kilometer area.

Water-Resources Investigations Report↗
USGS1984

Synopsis of ground-water and surface-water resources of North Dakota

This report describes the surface- and ground-water resources of North Dakota and the limitations of our understanding of these resources. Ground water and surface water are actually one resource, because they are often hydraulically interconnected. They are discussed separately for convenience. In general, the surface-water resources of the mainstem of the Missouri river are abundant and suitable for most uses. Other rivers may be important locally as water-supply sources, but the quantities of flow are small, quite variable in time, and generally of an unsuitable quality for most uses. Streamflow characteristics of North Dakota reflect its arid to semiarid climate (annual precipitation varies from 13 to 20 inches from west to east across the State), cold winters (usually including a significant snowpack available for spring snowmelt runoff), and the seasonal distribution of annual precipitation (almost 50 percent falls from Nky to July). Significant volumes of shallow ground water, of variable quality are found in the glacial-drift aquifers in parts of central, northern, and eastern North Dakota. Existing information provides only a limited capability to assess the long-term reliability of these scattered aquifers. There are significant indications, however, of water-quality problems related to sustained production of wells if long-term utilization of these aquifers is planned. A summary of the general suitability for use of surface water and ground water is given in Table E1.

Open-File Report↗
USGS1981

Approximate ground-water-level contours, April 1981, for the Soquel-Aptos area, Santa Cruz County, California

Ground-water levels in selected wells were measured in the Soquel-Aptos, Calif., area in April 1981. On the basis of these measurements approximate ground-water-level contours were constructed. The general direction of ground-water movement in the Soquell-Aptos area is from the ridges in the northern part of the area, toward the adjacent canyons, and then southward toward the ocean. Ground-water pumping has caused ground-water levels to decline below sea level in the Capitola area, in the area just to the west and northwest of aptos, and in isolated local areas southwest of Rio Del Mar. Ground-water levels in the northern part of the area away from the seacoast have not declined much over time. (USGS)

California↗
USGS1992

Streamflow gains and losses in the Snake River and ground-water budgets for the Snake River Plain, Idaho and eastern Oregon

The Snake River is the regional drain for streams and aquifers in the Snake River basin upstream from Weiser, Idaho. The interaction between the river and ground water was quantified as streamflow gains from and losses to the aquifers. Upstream from Milner, Idaho, the Snake River both gains and loses water. Some reaches gain or lose throughout the year; other reaches gain during the irrigation season when ground-water levels rise as a result of application of surface water for irrigation but lose during the rest of the year. The largest continuous streamflow gain upstream from Milner is from springs between Blackfoot and Neeley, where, in 1980, the Snake River gained 1.9 million acre-feet of ground water. Downstream from Milner, the Snake River is a gaining stream. Gains arc largest between Milner and King Hill where numerous springs discharge to the river. In 1980, the Snake River gained 4.7 million acre-feet of ground water between Milner and King Hill. Although large springs were present in the Blackfoot-to-Neeley and Milner-to-King Hill reaches before irrigation began on the plain, the application of surface water for irrigation increased recharge to the Snake River Plain aquifer; therefore, spring discharge to both reaches also increased. However, despite changes in irrigated acreage and corresponding changes in the amount of water potentially available for recharge, spring discharge between Blackfoot and Neeley has remained relatively stable for 69 years (1912-80). During the same period, discharge from individual springs and total ground-water discharge between Milner and King Hill have increased and decreased substantially in quantities that can be attributed to changes in irrigation. The changes in ground-water recharge and discharge and ground-water storage generally are the net result of 100 successive years of irrigation on the Snake River Plain. Water-budget analyses indicate that the total volume of ground water in storage in the main part of the eastern Snake River Plain increased about 24 million acre-feet from 1880 to 1952, largely as a result of increased recharge in areas irrigated with surface water. The total volume of ground water in storage decreased about 6 million acre-feet from 1952 to 1980 as a result of several years of below-normal precipitation, increased pumping of ground water for irrigation, and other changes in irrigation practices. Ground-water storage in parts of the western plain increased about 3 million acre-feet from 1930 to 1972 but generally has decreased since 1972.

Idaho, Oregon↗
USGS2005

Occurrence and distribution of volatile organic compounds and pesticides in ground water in relation to hydrogeologic characteristics and land use in the Santa Ana basin, southern California

This report presents an evaluation of the occurrence and distribution of VOCs and pesticides in the Santa Ana ground-water basins in relation to two types of explanatory factors: hydrogeologic characteristics and land use. The Santa Ana Basin is subdivided into the San Jacinto, the Inland, and the Coastal ground-water basins. Most wells sampled were deep and used for public supply. Data from regional studies were used to evaluate the occurrence and distribution of pesticides and volatile organic compounds (VOCs) in relation to hydrogeologic characteristics and land uses that could potentially explain variations between basins. Additional data from special studies (flow path and aquifer susceptibility) were used to evaluate potential factors affecting water quality for individual basins. The hydrogeologic characteristics evaluated in this report were hydrogeologic setting, ground-water age, depth to the top of the well screen (top of well perforations), and proximity to engineered recharge facilities. Urban land use, agricultural land use, and population density were characterized within a 500-meter radius of sampled wells and at the basin scale. Aquifers in the San Jacinto Basin are generally unconfined, and major land-use categories are urban (33 percent), agricultural (37 percent), and undeveloped (25 percent). Recharge is primarily from the overlying landscape, but engineered recharge is locally important in the Hemet area. VOCs and pesticides were detected more frequently in younger ground water (less than 50 years old) than in older ground water, and more frequently in shallower wells than deeper wells; the numbers of VOCs and pesticides detected also were significantly higher in the younger ground water and in the shallower wells. In the Hemet area of the San Jacinto Basin, VOCs and pesticides were detected more frequently in wells proximal to engineered recharge facilities than in distal wells. These patterns illustrate the importance of proximity to sources of recharge in relation to the occurrence and distribution of VOCs and pesticides in ground water. Aquifers in the Inland Basin also are generally unconfined, and the major land-use category is urban (58 percent), with lesser amounts of agricultural (13 percent) and undeveloped (28 percent) land. Recharge is from engineered facilities that utilize local runoff and imported water and from vertical infiltration. VOCs and pesticides were detected more frequently in younger ground water than in older ground water, and more frequently in shallower wells than deeper wells. The number of VOCs detected per well also was significantly higher in the younger ground water and in the shallower wells. Several solvent plumes extending between 5 and 10 kilometers illustrate the large distances that contaminants travel in basins with intensive use of ground water. Aquifers in the Coastal Basin, in contrast to the other basins, are generally confined. Land use in the basin is largely urban (80 percent), with lesser amounts of agricultural (7 percent) and undeveloped (12 percent) land. Recharge is primarily from engineered facilities that utilize water diverted from the Santa Ana River and imported water. Consequently, VOCs and pesticides were detected more frequently in wells proximal to engineered recharge facilities than in distal wells. These compounds were also detected more frequently in the unconfined area than in the confined area of the basin. In the confined area, the numbers of VOCs and pesticides detected per well were not significantly different in wells with shallower and deeper screens. This distribution reflects the dominance of lateral flow and insulation from overlying land use in the confined aquifers of the Coastal Basin. In the unconfined area of the Coastal Basin, the numbers of VOCs and pesticides detected per well were significantly higher in shallower wells than in deeper wells. VOC and pesticide detections were not statist

Scientific Investigations Report↗