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At least 1,711 records · Page 95Linked to original sources
USGS2003

Simulated ground-water flow in the Hueco Bolson, an alluvial-basin aquifer system near El Paso, Texas

The neighboring cities of El Paso, Texas, and Ciudad Juarez, Chihuahua, Mexico, have historically relied on ground-water withdrawals from the Hueco Bolson, an alluvial-aquifer system, to supply water to their growing populations. By 1996, ground-water drawdown exceeded 60 meters in some areas under Ciudad Juarez and El Paso. A simulation of steady-state and transient ground-water flow in the Hueco Bolson in westernmost Texas, south-central New Mexico, and northern Chihuahua, Mexico, was developed using MODFLOW-96. The model is needed by El Paso Water Utilities to evaluate strategies for obtaining the most beneficial use of the Hueco Bolson aquifer system. The transient simulation represents a period of 100 years beginning in 1903 and ending in 2002. The period 1903 through 1968 was represented with 66 annual stress periods, and the period 1969 through 2002 was represented with 408 monthly stress periods. The ground-water flow model was calibrated using MODFLOWP and UCODE. Parameter values representing aquifer properties and boundary conditions were adjusted through nonlinear regression in a transient-state simulation with 96 annual time steps to produce a model that approximated (1) 4,352 water levels measured in 292 wells from 1912 to 1995, (2) three seepage-loss rates from a reach of the Rio Grande during periods from 1979 to 1981, (3) three seepage-loss rates from a reach of the Franklin Canal during periods from 1990 to 1992, and (4) 24 seepage rates into irrigation drains from 1961 to 1983. Once a calibrated model was obtained with MODFLOWP and UCODE, the optimal parameter set was used to create an equivalent MODFLOW-96 simulation with monthly temporal discretization to improve computations of seepage from the Rio Grande and to define the flow field for a chloride-transport simulation. Model boundary conditions were modified at appropriate times during the simulation to represent changes in well pumpage, drainage of agricultural fields, and channel modifications of the Rio Grande. The model input was generated from geographic information system databases, which facilitated rapid model construction and enabled testing of several conceptualizations of hydrogeologic facies boundaries. Specific yield of unconfined layers and hydraulic conductance of Quaternary faults in the fluvial facies were the most sensitive model parameters, suggesting that ground-water flow is impeded across the fault planes.

Water-Resources Investigations Report↗
USGS2002

Delineation of the Troy Bedrock Valley and particle-tracking analysis of ground-water flow underlying Belvidere, Illinois

The U.S. Geological Survey, U.S. Environmental Protection Agency, and Illinois Environmental Protection Agency began a study of the hydrogeology, flow system, and distribution of contaminants in the aquifers underlying Belvidere, Ill., and vicinity in 1992. As part of the study, the ancestral Troy Bedrock Valley, located about 1.5 miles west of Belvidere, was identified as an important part of the ground-water-flow system. In the deepest parts of the valley, the basal Glenwood confining unit may be absent; thick deposits of sand and gravel that infill part of the valley may directly overlie the sandstone St. Peter aquifer, a regionally important source of water for public supply. With few deep wells open to the St. Peter aquifer present in the valley to provide necessary geologic information, tritium and other water-chemistry data were collected from eight wells to possibly delineate areas where the confining unit may be absent; the data also provide baseline water-quality information for an area expecting changes in land use and increases in water withdrawal. Also as part of the study, particle-tracking analysis was done using an available flow model to (1) identify possible discharge locations of ground water and contaminants and (2) delineate areas contributing recharge to the Belvidere municipal wells. This report presents and interprets water-chemistry data collected during December 2000 and presents results of particle-tracking analysis. Ground water in samples from two of four wells open to the St. Peter aquifer appears to have recharged after 1954, suggesting that the Glenwood confining unit may be absent near the wells. Other hydrogeologic and water-chemistry data, however, were inconclusive or contradictory. Concentrations of iron, manganese, and lead exceeded maximum contaminant levels in five or less samples, but materials associated with the water-distribution systems appear to contribute to the elevated concentrations above natural levels. Particle-tracking analysis indicates that most ground-water flow beneath possible contaminant-source areas discharges from the glacial drift aquifer to the Kishwaukee River. Most of the source areas are in or near Belvidere and are within 1,500 feet of the river. The analysis also indicates the possibility that in parts of the study area, some ground water does not discharge to the river, but flows beneath the Kishwaukee River in the underlying carbonate Galena-Platteville aquifer. Ground water that discharges to the one municipal well open to the glacial drift aquifer is estimated to travel over 1 mile in less than 25 years. Simulated residence (travel) times of ground water from the base of the glacial drift aquifer to the six municipal wells open, in part, to the Galena-Platteville aquifer, are estimated at less than about 40 years. Because fractures in this aquifer are unaccounted for in the flow model, actual areas contributing recharge are likely larger and travel times faster than those simulated for most of the municipal wells. Tritium data indicate that, in general, travel times from the land surface to the deepest parts of the Galena-Platteville aquifer are less than 46 years. Methyl tertiary-butyl ether data indicate that travel times to the upper part of the aquifer may be less than 16 years. The water-quality-based estimates of travel time generally are consistent with the estimates from particle-tracking analysis.

Illinois↗
USGS1998

Proposed expansion of the City of Albuquerque/U.S. Geological Survey ground-water-level monitoring network for the middle Rio Grande Basin, New Mexico

The Middle Rio Grande Basin in central New Mexico, extending from Cochiti Lake on the north to San Acacia on the south, covers an area of about 3,060 square miles. Ground-water withdrawals in the basin are concentrated in and around the city of Albuquerque. Because of rapid increases in population and associated ground-water pumpage, a network of wells was established cooperatively by the City of and the U.S. Geological Survey between April 1982 and September 1983 to monitor changes in ground-water levels throughout the basin. Expansion of this network has been identified as an essential element in plans to study the relation between surface water and ground water in the basin. An inventory of existing wells in the Albuquerque metropolitan area has brought together information on about 400 wells that either are being monitored for water levels or would be good candidates for monitoring. About 115 wells or well sites are proposed as additions to the current 128-well ground-water-level monitoring network for the Middle Rio Grande Basin. Despite the extensive network that would be created by the addition of the proposed existing wells, however, certain parts of the Albuquerque metropolitan area would remain without adequate coverage areally and/or with depth in the Santa Fe Group aquifer until the installation of the proposed new monitoring wells.

Open-File Report↗
USGS1962

Ground-Water Reconnaissance at Pinnacles National Monument, California

Ground-water supplies at Pinnacles National Monument have been obtained from springs that occur in fractures and along bedding planes of volcanic flows and deposits, and from springs discharged from perched water in a sedimentary fanglomerate formation. The spring-water yield is barely adequate to supply existing camp facilities, and therefore a supplemental water supply is necessary before existing campgrounds can be expanded. This supplemental water can be supplied by good-quality ground water obtained from shallow wells drilled in the alluvium of Chalone Creek. The yield of properly constructed wells in this area should exceed 10 gallons per minute.

Water Supply Paper↗
USGS2001

Use of borehole and surface geophysics to investigate ground-water quality near a road-deicing salt-storage facility, Valparaiso, Indiana

Borehole and surface geophysics were used to investigate ground-water quality affected by a road-deicing salt-storage facility located near a public water-supply well field. From 1994 through 1998, borehole geophysical logs were made in an existing network of monitoring wells completed near the bottom of a thick sand aquifer. Logs of natural gamma activity indicated a uniform and negligible contribution of clay to the electromagnetic conductivity of the aquifer so that the logs of electromagnetic conductivity primarily measured the amount of dissolved solids in the ground water near the wells. Electromagnetic-conductivity data indicated the presence of a saltwater plume near the bottom of the aquifer. Increases in electromagnetic conductivity, observed from sequential logging of wells, indicated the saltwater plume had moved north about 60 to 100 feet per year between 1994 and 1998. These rates were consistent with estimates of horizontal ground-water flow based on velocity calculations made with hydrologic data from the study area. Ratios of chloride to bromide concentrations in water samples were used to distinguish sources of chloride in the ground water?whether from road-deicing salt, domestic wastewater, or natural occurrences. Water samples identified with the chloride/bromide ratios as being affected by road-deicing salt had concentrations of dissolved solids, chloride, and sodium many times the background levels for the study area. The largest concentrations were in water from wells near the salt-storage facility?12,400 to 12,800 milligrams per liter (mg/L) dissolved solids, 6,730 to 7,230 mg/L chloride, and 3,690 to 4,400 mg/L sodium. A conceptual, multi-layer model was developed to describe the vertical extent of the saltwater plume in the vicinity of the monitoring wells. A relation was derived between average borehole electromagnetic conductivity in the screened interval of the wells in the saltwater plume and concentrations of dissolved solids in water samples from those wells. This relation was used in the model to show borehole electromagnetic conductivity in transects of wells as a zone of saline water overlain by zones of brackish water and freshwater. The thickness and altitude of the zones of saline and brackish water decreased with increased distance from the salt-storage facility. Two surface surveys of terrain electromagnetic conductivity were used to map the horizontal extent of the saltwater plume in areas without monitoring wells. Background values of terrain conductivity were measured in an area where water-quality and borehole geophysical data did not indicate saline or brackish water. Based on a guideline from previous case studies, the boundaries of the saltwater plume were mapped where terrain conductivity was 1.5 times background. The extent of the saltwater plume, based on terrain conductivity, generally was consistent with the available water-quality and borehole electromagnetic-conductivity data and with directions of ground-water flow determined from water-level altitudes.

Indiana↗
USGS1994

Annotated bibliography of selected references on ground-water resources and geohydrology of the Louisville area, Kentucky, 1944-93

Ground water resources in the Louisville area have long been the subject of intense research and investigation. Many investigations have resulted in reports that cover a variety of topics relative to the availability and use of ground water. This bibliography was prepared because of the continued interest in ground water in the Louisville area and the need for a single source of selected references published since 1944. The bibliography is intended to assist interested parties in finding needed information but is not intended to be a complete compilation of all references. The annotated bibliography provides a synopsis of 36 reports and 4 geologic maps.

Open-File Report↗
USGS1993

234U/238U as a ground-water tracer, SW Nevada-SE California

The 234U/238U ratio of uranium in oxidizing ground waters is potentially an excellent ground-water tracer because of its high solubility and insensitivity to chemical reactions. Moreover, recent advances in analytical capability have made possible very precise uranium-isotopic analyses on modest (approx.100 ml) amounts of normal ground water. Preliminary results on waters from SW Nevada/Se California indicate two main mixing trends, but in detail indicate significant complexity requiring three or more main components.

California, Nevada↗
USGS1981

Ground-water quality atlas of Wisconsin

This report summarizes data on ground-water quality stored in the U.S. Geological Survey's computer system (WATSTORE). The summary includes water quality data for 2,443 single-aquifer wells, which tap one of the State's three major aquifers (sand and gravel, Silurian dolomite, and sandstone). Data for dissolved solids, hardness, alkalinity, calcium, magnesium, sodium, potassium, iron, manganese, sulfate, chloride, fluoride, and nitrate are summarized by aquifer and by county, and locations of wells for which data are available 1 are shown for each aquifer. Calcium, magnesium, and bicarbonate (the principal component of alkalinity) are the major dissolved constituents in Wisconsin's ground water. High iron concentrations and hardness cause ground-water quality problems in much of the State. Statewide ,summaries of trace constituent (selected trace metals; arsenic, boron, and organic carbon) concentrations show that these constituents impair water quality in only a few isolated wells.

Wisconsin↗
USGS1993

Hydrogeology, ground-water quality, and potential for water-supply contamination near an abandoned wood-preserving plant site at Jackson, Tennessee

Hydrogeologic and ground-water-quality data were collected near an abandoned wood-preserving plant site at Jackson, Tennessee to determine the extent and magnitude of ground-water contamination in offsite areas and to assess the potential for contamination of nearby water-supply wells. New methods were used to collect ground-water samples from the alluvial aquifer at six offsite stations at depths of less than about 40 feet below land surface. In addition, 36 offsite wells were installed at these stations to collect samples from the alluvial aquifer and to depths of about 150 feet in the deeper Fort Pillow aquifer. Ground-water samples collected by the new methods and from the 36 offsite wells were analyzed for selected volatile and semi-volatile compounds. The samples collected from the 36 wells also were analyzed for major and trace inorganic constituents. Naphthalene and some volatile organic compounds were detected at low concentrations in samples from both the alluvial aquifer and the Fort Pillow aquifer. To assess the potential for water-supply contamination from the site, four water-supply wells to the east (upgradient) and three wells to the west (down- gradient) of the abandoned plant site were sampled. These samples were analyzed for the same analytes as the samples from the 36 wells. Although volatile organic compounds and elevated concentrations of trace and major inorganic constituents were measured in samples from some wells east of the site, no organic compounds associated with the wood- preserving process were detected. No contaminants from the site were detected in samples from wells west of the site.

Water-Resources Investigations Report↗
USGS1983

Ground-water contamination at Wurtsmith Air Force Base, Michigan

A sand and gravel aquifer of glacial origin underlies Wurtsmith Air Force Base in northeastern lower Michigan. The aquifer overlies a thick clay layer at an average depth of 65 feet. The water table is about 10 feet below land surface in the western part of the Base and about 25 feet below land surface in the eastern part. A ground-water divide cuts diagonally across the Base from northwest to southeast. South of the divide, ground water flows to the Au Sable River; north of the divide, it flows to Van Etten Creek and Van Etten Lake. Mathematical models were used to aid in calculating rates of groundwater flow. Rates range from about 0.8 feet per day in the eastern part of the Base to about 0.3 feet per day in the western part. Models also were used as an aid in making decisions regarding purging of contaminated water from the aquifer. In 1977, trichloroethylene was detected in the Air Force Base water-supply system. It had leaked from a buried storage tank near Building 43 in the southeastern part of the Base and moved northeastward under the influence of the natural ground-water gradient and the pumping of Base water-supply wells. In the most highly contaminated part of the plume, concentrations are greater than 1,000 micrograms per liter. Current purge pumping is removing some of the trichloroethylene, and seems to have arrested its eastward movement. Pumping of additional purge wells could increase the rate of removal. Trichloroethylene has also been detected in ground water in the vicinity of the Base alert apron, where a plume from an unknown source extends northeastward off Base. A smaller, less well-defined area of contamination also occurs just north of the larger plume. Trichloroethylene, identified near the waste-treatment plant, seepage lagoons, and the northern landfill area, is related to activities and operations in these areas. Dichloroethylene and trichloroethylene occur in significant quantities westward of Building 43, upgradient from the major spill site. Benzene, indicative of ground-water contamination by a fuel substance, occurs in an area northeast of the bulk-fuel storage area. Analysis of a variety of chemical, physical, and biologic characteristics of water on the Base indicate that there is a measurable affect on ground-water quality from landfills, the seepage lagoon, and the waste-treatment plant.

Michigan↗
USGS1997

Monitoring for pesticides in ground water in Nevada

Many pesticides designed to control weed encroachment, plant disease, and insect predation are used in agricultural and urban areas in the United States. Contamination of ground water by pesticides has increased over the last 20 years (U.S. Environmental Protection Agency, 1992). In 1985, the U.S. Environmental Protection Agency (USEPA) estimated the detection of at least 17 agricultural pesticides in the ground water of 23 states. By 1988, pesticides identified in ground water had increased to 46 in 26 states. To protect ground water from pesticide contamination, USEPA, through the Federal Fungicide Insecticide and Rodenticide Act (FIFRA), requires all states to institute a ground-water protection program.

Nevada↗
USGS1994

Hydrogeology and ground-water quality of northern Bucks County, Pennsylvania

The 187-square mile study area is in the Triassic-Jurassic Newark Basin. Most of the area is underlain by sedimentary rocks of Upper Triassic age (74 percent) and intrusive diabase of Jurassic age (12 percent) and includes two southwest-northeast trending valleys underlain by carbonate and crystalline rock. Ground water in the sedimentary rocks of Triassic age moves through a network of interconnecting secondary openings fractures, bedding planes, and joints. The ground-water system consists of beds with a relatively high transmissivity separated by beds with a relatively low transmissivity that form a leaky, multiaquifer system. Ground water is unconfined in the shallower part of the aquifer and confined or semiconfined in the deeper part of the aquifer. Most deep wells are open to several water-bearing zones and are multiaquifer wells. The frequency of occurrence of water-bearing zones decreases with depth. Sixty-five percent of water-bearing zones for all hydrogeologic units are within 200 feet of land surface, and 85 percent are within 300 feet of land surface. On the basis of the median specific capacity of nondomestic wells, carbonate rocks, the Brunswick Group, and the Stockton Formation are the most productive hydrogeologic units. Carbonate rocks and the Stockton Formation have the highest median nondomestic well yields (156 and 120 gallons per minute, respectively) among the hydrogeologic units. Thirty-four percent of domestic wells drilled in diabase, 30 percent in the Lockatong Formation, and 21 percent in carbonate rock yield less than 5 gallons per minute. Average water budgets for the Cooks, Tinicum, Paunnacussing, and Mill Creek Basins weighted by drainage area were calculated for 1991-92. Average annual precipitation was 41.7 in. (inches); average annual evapotranspiration (ET) and other losses were 26.2 in. or 63 percent of precipitation; average annual streamflow was 15.9 in., or 38 percent of the average precipitation; and the average annual change in ground-water storage was a decrease of 0.3 in., or less than 1 percent of the average annual precipitation. Average estimated recharge for 1991-92 weighted by drainage area was 10.1 in. [0.485 (Mgal/d)/mi 2 (million gallons per day per square mile)]; this is equal to a recharge rate of 758 gallons per day per acre. Water budgets for the Tohickon Creek Basin were calculated for 1968-91 (prior to regulation of the stream by Lake Nockamixon). The average annual precipitation was 47.2 in.; average annual ET and other losses were 24.3 in., or 51 percent of the average annual precipitation; and annual streamflow was 22.6 in., or 48 percent of the average annual precipitation. Streamflow hydrographs for 1991-92 for Cooks, Tinicum, Paunnacussing, and Mill Creeks were separated into baseflow and surface-runoff components. Average annual ground-water discharge to streams weighted by drainage area was 8.4 in. [0.403 (Mgal/d)/mi 2 ], which was 20 percent of the average annual precipitation and 53 percent of the average annual streamflow. Average annual surface runoff weighted by drainage area was 7.4 in., which was 18 percent of the average annual precipitation and 47 percent of the average annual streamflow. Annual base flow for 1936-71 for Tohickon Creek ranged from 2.5 in. [0.12 (Mgal/d)/mi 2 ] in 1965 to 8.4 in. [0.40 (Mgal/d)/mi 2 ] in 1945. The median base flow was 5.3 in. [0.25 (Mgal/d)/mi 2 ]. Water from wells in the crystalline rocks has the lowest median pH (5.8), the lowest median specific conductance (139 microsiemens per centimeter), the lowest median alkalinity [16 mg/L (milligrams per liter) as CaCOg], and the highest dissolved oxygen concentration (9.0 mg/L) of the hydrogeologic units. Water from wells in carbonate rocks has the highest median pH (7.8) and the highest median alkalinity (195 mg/L as CaCO3) of the hydrogeologic units. Water from wells in the Lockatong Formation has the highest median specific conductance (428 microsiemens per centimeter) and the lowest dissolved oxygen concentration (0.8 mg/L) of the hydrogeologic units. Water from wells in crystalline rocks contains the lowest concentrations of total dissolved solids (TDS) of the hydrogeologic units. Water from the Lockatong Formation contains the highest concentration of TDS of the hydrogeologic units. Water from only 1 of 83 wells sampled exceeded the U.S. Environmental Protection Agency (USEPA) secondary maximum contaminant level (SMCL) for TDS; the well is in the Lockatong Formation. Five of 86 samples (6 percent) and 6 of 75 samples (8 percent) exceed the USEPA SMCL for iron and manganese, respectively. Nitrate is the most prevalent nitrogen species in ground water. The median nitrate concentration for all hydrogeologic units is 2.3 mg/L. Of 71 water samples from wells, no concentrations of nitrate exceed the USEPA maximum contaminant level. The median dissolved radon-222 activity was highest for water samples from wells in crystalline rock [3,600 pCi/L (picocuries per liter)] and lowest for water samples from wells in the Lockatong Formation (340 pCi/L) and diabase (350 pCi/L). Water samples for analysis for volatile organic compounds (VOC's) were collected from 34 wells in areas where the potential existed for the presence of VOC's in ground water. VOC's were detected in 23 percent of the 34 wells sampled. The most commonly detected compound was trichloroethylene (13 percent of sampled wells).

Pennsylvania↗
USGS2006

Simulated Effects of Seasonal Ground-Water Pumpage for Irrigation on Hydrologic Conditions in the Lower Apalachicola-Chattahoochee-Flint River Basin, Southwestern Georgia and Parts of Alabama and Florida, 1999-2002

To determine the effects of seasonal ground-water pumpage for irrigation, a finite-element ground-water flow model was developed for the Upper Floridan aquifer in the lower Flint River Basin area, including adjacent parts of the Chattahoochee and Apalachicola River Basins. The model simulates withdrawal from the aquifer at 3,280 irrigation, municipal, and industrial wells; stream-aquifer flow between the aquifer and 36 area streams; leakage to and from the overlying upper semiconfining unit; regional ground-water flow at the lateral boundaries of the model; and water-table recharge in areas where the aquifer is at or near land surface. Steady-state calibration to drought conditions of October 1999 indicated that the model could adequately simulate measured groundwater levels at 275 well locations and streamflow gains and losses along 53 reaches of area streams. A transient simulation having 12 monthly stress periods from March 2001 to February 2002 incorporated time-varying stress from irrigation pumpage, stream and lake stage, head in the overlying upper semiconfining unit, and infiltration rates. Analysis of simulated water budgets of the Upper Floridan aquifer provides estimates of the source of water pumped for irrigation. During October 1999, an estimated 127 million gallons per day (Mgal/d) of irrigation pumpage from the Upper Floridan aquifer in the model area were simulated to be derived from changes in: stream-aquifer flux (about 56 Mgal/d, or 44 percent); leakage to or from the upper semiconfining unit (about 49 Mgal/d, or 39 percent); regional flow (about 18 Mgal/d, or 14 percent); leakage to or from Lakes Seminole and Blackshear (about 2.7 Mgal/d, or 2 percent); and flux at the Upper Floridan aquifer updip boundary (about 1.8 Mgal/d, or 1 percent). During the 2001 growing season (May-August), estimated irrigation pumpage ranged from about 310 to 830 Mgal/ d, about 79 percent of the 12-month total. During the growing season, irrigation pumpage was derived from decreased discharge or increased recharge of stream-aquifer flux (from about 23 to 39 percent), leakage to or from the upper semiconfining unit (from about 30 to 36 percent), regional flow (from about 8 to 11 percent), Lakes Seminole and Blackshear (about 2 percent), and flux at the Upper Floridan aquifer updip boundary (about 1 percent). Storage effects (decreased storage gain or increased storage loss) contributed from about 11 to 36 percent of irrigation pumpage during the growing season. Water managers can use the model to determine where and how much additional ground-water pumpage for irrigation should be permitted based on a variety of hydrologic constraints. For example, the model results may indicate that in some critical locations, additional ground-water pumpage during a prolonged drought might reduce stream-aquifer flux enough to cause noncompliance of established minimum instream flow conditions.

Alabama, Florida, Georgia↗
USGS1987

Hydrogeology and ground-water quality at a land reclamation site, Neshaminy State Park, Pennsylvania

At Neshaminy State park, the most important aquifer is the informally named 'Trenton gravel' of Pleistocene age, which consists of poorly sorted sand and gravel. This is underlain by less permeable crystalline rock that limits the downward movement of water. Up to 5 feet of Holocene (or perhaps Pleistocene) alluvium consisting of clay and silt was deposited above the Trenton gravel, but much of the surficial material is dredge spoil, mostly sand and silt from the Delaware River. Normally, ground water discharges to the Delaware River and Neshaminy Creek. However, because the Trenton gravel is confined by the alluvium and is hydraulically connected to the Delaware River throughout its entire thickness due to channel dredging, hydraulic-head variations in the river are readily transmitted to wells. Thus, flow is toward the Delaware River and Neshaminy Creek at low tide, but the river and and creek recharge the aquifer as the tide rises. In September 1981 and October 1983, infertile dredge spoil from the Delaware River at Neshaminy State Park was mixed with composted sewage sludge and seeded to grasses to produce a soil product that has not adversely affected ground-water quality as of March 1985. Analyses for pH, specific conductance, nutrients, and heavy metals in ground water at the beginning of the study indicate that the chemistry of the ground water in the dredge spoil at the site differs from that in the Trenton gravel. Analyses of ground-water samples collected after the first two sludge applications (120 tons per acre and 450 tons per acre), indicate that no significant change occurred in the chemistry of the samples from the Trenton gravel, whereas organic nitrogen increased temporarily in ground water from the dredge spoil 6 months after the larger of the two sludge applications, but quickly returned to background levels. The lack of chemical change with time in the ground water implies either that little of the more than 100 inches of precipitation that fell from April 1983 through March 1985 reached the water table or, more likely, that a mechanism exists beneath the soil- factory site that retards or prevents the downard migration of contaminants.

Pennsylvania↗
USGS2005

Bibliography of ground-water references for all 254 counties in Texas, 1886-2001

Preface This bibliography comprises more than 10,000 citations of ground-water references involving all 254 counties in Texas. The reference citations date from 1886 and extend into 2001. Publications and reports from more than 30 agencies, universities, water districts, geological societies, cities, consultants, and private publication outlets are included in the bibliography. The bibliographic listing is, first, alphabetical by county and, second, chronological by date of the report, from oldest to most recent. The passing years have seen a proliferation in both published and unpublished reports, and such proliferation continues to expand at an accelerating pace. All 254 counties have had groundwater studies, either cursory or detailed. Investigation and development of the ground-water resources of the State of Texas resulted in reports that appear in a variety of formats, including Federal, State, and local agency reports; scholarly, professional, and trade journals; conference proceedings; guidebooks; maps; and theses and dissertations. The end result for the person seeking ground-water information about specific Texas counties is the increasing difficulty in locating pertinent data among the many and diverse ground-water reports in which the information is recorded. This bibliography, covering a span of 115 years, should have considerable utility in guiding those individuals seeking ground-water information.

Texas↗
USGS2004

Analytical results from ground-water sampling using a direct-push technique at the Dover National Test Site, Dover Air Force Base, Delaware, June-July 2001

A joint study by the Dover National Test Site and the U.S. Geological Survey was conducted from June 27 through July 18, 2001 to determine the spatial distribution of the gasoline oxygenate additive methyl tert-butyl ether and selected water-quality constituents in the surficial aquifer underlying the Dover National Test Site at Dover Air Force Base, Delaware. The study was conducted to support a planned enhanced bio-remediation demonstration and to assist the Dover National Test Site in identifying possible locations for future methyl tert-butyl ether remediation demonstrations. This report presents the analytical results from ground-water samples collected during the direct-push ground-water sampling study. A direct-push drill rig was used to quickly collect 115 ground-water samples over a large area at varying depths. The ground-water samples and associated quality-control samples were analyzed for volatile organic compounds and methyl tert-butyl ether by the Dover National Test Site analytical laboratory. Volatile organic compounds were above the method reporting limits in 59 of the 115 ground-water samples. The concentrations ranged from below detection limits to maximum values of 12.4 micrograms per liter of cis-1,2-dichloroethene, 1.14 micrograms per liter of trichloroethene, 2.65 micrograms per liter of tetrachloroethene, 1,070 micrograms per liter of methyl tert-butyl ether, 4.36 micrograms per liter of benzene, and 1.8 micrograms per liter of toluene. Vinyl chloride, ethylbenzene, p,m-xylene, and o-xylene were not detected in any of the samples collected during this investigation. Methyl tert-butyl ether was detected in 47 of the 115 ground-water samples. The highest methyl tert-butyl ether concentrations were found in the surficial aquifer from -4.6 to 6.4 feet mean sea level, however, methyl tert-butyl ether was detected as deep as -9.5 feet mean sea level. Increased methane concentrations and decreased dissolved oxygen concentrations were found in samples that contained methyl tert-butyl ether.

Open-File Report↗
USGS1995

Hydrogeology and analysis of ground-water withdrawal from the Catahoula aquifer system in the Natchez area, Adams County, Mississippi

The city of Natchez, located in Adams County, Mississippi, relies on ground water for public supply and industrial needs. Most public supply and industrial wells are developed in Catahoula Formation sands of Miocene age. In 1991, an investigation began to describe the hydrogeology, analyze the effects of ground-water withdrawal from currently pumped wells, and project the possible effects of increased ground-water withdrawals on water levels in the Catahoula aquifer system within the Natchez area. The study area covers about 80 square miles in Adams County, southwestern Mississippi. The study area contains several aquifers; however, the most important aquifers in terms of water supply are the Mississippi River alluvial aquifer and the Catahoula aquifer system. In the Natchez area, the Catahoula aquifer system consists of three main sand intervals that form the upper, middle, and lower Catahoula aquifers. Ground-water withdrawal from the Catahoula aquifer system in the study area currently (March 1995) is from 24 wells screened in the three aquifers. The current daily rate of withdrawal is about 9.2 million gallons of water per day. Analysis of the effect of ground-water withdrawal from these wells was made using the Theis nonequilibrium equation and applying the principle of superposition. The calculated drawdown surfaces under current conditions indicate cones of depression surrounding the principal wells. In the upper Catahoula sand, most of the drawdown is concentrated about 1 mile east of the downtown Natchez area, where a maximum drawdown of 95x11 feet was calculated. Most of the drawdown in the middle Catahoula sand occurred in the same general vicinity as in the upper sand, with a maximum calculated drawdown of about 113 feet. Drawdown in the lower Catahoula sand was concentrated about 4x11 miles northeast of downtown Natchez, with a maximum calculated drawdown of about 31 feet. Drawdown-surface maps were made using calculations based on current pumping rates for 10 years and 20 years beyond March 1995. Planned changes in the pumping configuration were incorporated into these analyses. The drawdown surface calculated for 10 years beyond March 1995 indicates an average total increase in drawdown of about 7.3 feet for the upper Catahoula sand, with a maximum increase of about 28 feet. An average total increase in drawdown of only 1.2 feet was calculated for the middle Catahoula sand due to the planned discontinued pumping of many of the wells. An average total increase in drawdown of about 19 feet was calculated for the lower Catahoula sand, with a maximum increase of about 41 feet. The drawdown surface calculated for 20 years beyond March 1995 indicates an average total additional increase in drawdown over the 10 year drawdown surface of about 1.9, 0.6, and 2.7 feet for the upper, middle, and lower Catahoula sands, respectively.

Water-Resources Investigations Report↗
USGS1989

Oxygen-isotope composition of ground water and secondary minerals in Columbia Plateau basalts: Implications for the paleohydrology of the Pasco Basin

Concentrations of 18 O and deuterium in ground waters beneath the Hanford Reservation, Washington State, suggest that the meteoric waters recharging the basalt aquifers have been progressively depleted in these isotopes since at least Pleistocene time. This conclusion is supported by oxygen-isotope analyses of low-temperature secondary minerals filling vugs and fractures in the basalts, which are used to approximate the 18 O content of ground water at the time the mineral assemblage formed. A fossil profile of δ 18 O values projected for ground water in a 1500 m vertical section beneath the reservation suggests that the vertical mixing of shallow and deep ground water indicated by present-day hydrochemical data was also occurring during Neogene time. These data also suggest that a unidirectional depletion of 18 O and deuterium recorded in Pleistocene ground waters may have extended considerably further back in time. This shift is tentatively attributed to the orographic depletion of 18 O associated with the progressive uplift of the Cascade Range since the middle Miocene.

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