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At least 1,441 records · Page 80Linked to original sources
USGS1982

Ground-water quality in east-central Idaho valleys

From May through November 1978, water quality, geologic, and hydrologic data were collected for 108 wells in the Lemhi, Pahsimeroi, Salman River (Stanley to Salmon), Big Lost River, and Little Lost River valleys in east-central Idaho. Data were assembled to define, on a reconnaissance level, water-quality conditions in major aquifers and to develop an understanding of factors that affected conditions in 1978 and could affect future ground-water quality. Water-quality characteristics determined include specific conductance, pH, water temperature, major dissolved cations, major dissolved anions, and coliform bacteria. Concentrations of hardness, nitrite plus nitrate, coliform bacteria, dissolved solids, sulfate, chloride, fluoride , iron, calcium, magnesium, sodium, potassium or bicarbonate exceed public drinking water regulation limits or were anomalously high in some water samples. Highly mineralized ground water probably is due to the natural composition of the aquifers and not to surface contamination. Concentrations of coliform bacteria that exceed public drinking water limits and anomalously high dissolved nitrite-plus-nitrite concentrations are from 15- to 20-year old irrigation wells in heavily irrigated or more densely populated areas of the valleys. Ground-water quality and quantity in most of the study area are sufficient to meet current (1978) population and economic demands. Ground water in all valleys is characterized by significant concentrations of calcium, magnesium, and bicarbonate plus carbonate ions. Variations in the general trend of ground-water composition (especially in the Lemhi Valley) probably are most directly related to variability in aquifer lithology and proximity of sampling site to source of recharge. (USGS)

Open-File Report↗
USGS2001

User interface for ground-water modeling: Arcview extension

Numerical simulation for ground-water modeling often involves handling large input and output data sets. A geographic information system (GIS) provides an integrated platform to manage, analyze, and display disparate data and can greatly facilitate modeling efforts in data compilation, model calibration, and display of model parameters and results. Furthermore, GIS can be used to generate information for decision making through spatial overlay and processing of model results. Arc View is the most widely used Windows-based GIS software that provides a robust user-friendly interface to facilitate data handling and display. An extension is an add-on program to Arc View that provides additional specialized functions. An Arc View interface for the ground-water flow and transport models MODFLOW and MT3D was built as an extension for facilitating modeling. The extension includes preprocessing of spatially distributed (point, line, and polygon) data for model input and postprocessing of model output. An object database is used for linking user dialogs and model input files. The Arc View interface utilizes the capabilities of the 3D Analyst extension. Models can be automatically calibrated through the Arc View interface by external linking to such programs as PEST. The efficient pre- and postprocessing capabilities and calibration link were demonstrated for ground-water modeling in southwest Kansas.

Journal of Hydrologic Engineering↗
USGS1963

Geology and ground-water conditions in southern Nassau and southeastern Queens Counties, Long Island, N.Y.

Test drilling, electrical logging, and water sampling of 'outpost' and other wells have revealed the existence of a deep confined body of salt water in the Magothy(?) formation beneath southwestern Nassau and southeastern Queens Counties, Long Island, N.Y. In connection with a test-drilling program, cooperatively sponsored by the U.S. Geological Survey, the Nassau County Department of Public Works, and the New York State Water Resources Commission (formerly Water Power and Control Commission), 13 wells ranging in depth from about 130 to 800 feet were drilled during 1952 and 1953 and screened at various depths in the Magothy(?) formation and Jameco gravel. On the basis of the preliminary geologic, hydrologic, and chemical data from these wells, a detailed investigation of ground-water conditions from the water table to the bedrock was begun in a 200-square-mile area in southern Nassau and southeastern Queens Counties. The Inain purposes of the investigation were to delineate the bodies of fresh and salty ground water in the project area, to relate their occurrence and movement to geologic and hydrologic conditions, to estimate the rate of encroachment, if any, of the salty water, and to evaluate the effectiveness of the existing network of outpost wells as detectors of salt-water encroachment. About a million people in the report area, residing mainly in southern Nassau County, are completely dependent on ground water as a source of supply. Fortunately, precipitation averages about 44 inches per year, of which approximately half is estimated to percolate into the ground-water reservoir. The ground water is contained in and moves through eight differentiated geologic units composed of unconsolidated gravel, sand, and clay, of Late Cretaceous, Pleistocene, and Recent age, having a maximum total thickness of about 1,700 feet. The underlying metamorphic and igneous crystalline basement rocks are of Precambrian age and are not water bearing. The water-yielding units from the surface down are (1) the upper Pleistocene deposits, (2) the principal artesian aquifer, composed of the Jameco gravel and Magothy(?) formation, and (3) the Lloyd sand member of the Raritar formation. The confining units are the '20-foot' clay, the Gardiners clay, and the clay member of the Raritan formation. The upper Pleistocene deposits contain an extensive unconfined body of fresh water. Fresh water under artesian conditions is contained in the principal artesian aquifer and the Lloyd sand member. The piezometric surface of the principal artesian aquifer is similar in shape to the south-ward-sloping water table; it ranges in altitude from about sea level to 55 feet above. The chemical quality of the fresh ground water in most of the area in all aquifers is good to excellent, and concentrations of dissolved solids and of chloride generally are below 100 ppm (parts per million) and 10 ppm, respectively. Analyses of water samples from selected wells show no progressive increase in concentration of chloride in most of the area. The data on quality of water have been used to delineate one major and several minor bodies of salty ground water. The wedgeshaped main confined salt-water body, in which the concentration of chloride reaches about 17,000 ppm, is in the Magothy(?) formation and Jameco gravel in extreme southwestern Nassau County and southeastern Queens County. The base of the salt-water wedge is about at the top of the clay member of the Raritan formation. Beneath the barrier beach in south-central and southeastern Nassau County a shallow extension of the main confined salt-water body contains as much as 4,000 ppm of chloride and is separated from the lower main salt-water body by fresh ground water. Shallow, thin bodies of unconfined salty ground water are common in the upper Pleistocene and Recent deposits adjacent to salty surface water in tidal creeks, bays, and the Atlantic

New York↗
USGS1981

Effects of effluents from a coal-fired, electric-generating powerplant on local ground water near Hayden, Colorado

Data were collected at the Hayden, Colo., powerplant for about a year during 1978-79 to monitor the effects of effluent and raw-water storage ponds on the local ground water, Sage Creek, and the Yampa River. The concentration of boron in wells downgradient from the effluent ponds indicated that the ponds were leaking, increasing the average boron concentrations in the ground water to a level in excess of the standards for agricultural use of water. Water from seeps, probably the best indicators of downgradient water quality, had average concentrations of boron two times that of the Colorado Department of Health (1977) standard for agricultural use of water. Chemical analyses of water from wells and the discharge weir downgradient from the raw-water storage ponds indicated these ponds are leaking. The effect of this leakage is that the water in wells downgradient from these ponds has a lower specific conductance and a lower boron concentration than the water in wells downgradient from the effluent ponds. The concentration of trace elements in the water from the wells and the discharge weir generally declined during the study, probably because the ground water was recovering from the effects of a plume from the raw-water pond previously used for fly-ash disposal. The effluents from the Hayden powerplant lowered the specific conductance and the iron and manganese concentrations, increased the concentration of boron, and had little or no effect on the selenium concentration in Sage Creek. Sage Creek had no discernible effect on the Yampa River because the volume of water in the Yampa River was so much greater. The effluents from the powerplant also had no discernible effect on the Yampa River. (USGS)

Open-File Report↗
USGS1993

Distribution of stable isotopes in ground water in the Rialto-Colton basin, California

Since 1982, imported water originating in the Sierra Nevada has been used to recharge the Rialto-Colton ground-water basin, about 100 km east of Los Angeles. Stable isotopes of oxygen (oxygen-18) and hydrogen (deuterium) were used to determine the disposition of artificially recharged, imported water within the basin. Delta oxygen-18 ratios in water from wells sampled in spring and summer 1992 ranged from -7.65 to -10 permil. Delta deuterium ratios ranged from -46.5 to -65.0 permil. The imported water is isotopically lighter than the native ground water in the basin. For the imported water, delta oxygen- 18 ratios ranged from -8.6 to -10.1 permil, and delta deuterium ratios ranged from -65 to -75 permil. The isotope data show no evidence of mixing between the imported water and the native ground water in the sampled wells. Statistical analyses show that the difference in the isotopic composition of the imported water and the native ground water is highly significant and that the stable isotopes of oxygen and hydrogen can be used to determine the fate and movement of the imported water in the Rialto-Colton basin.

Conference Paper↗
USGS1972

Ground-water quality in Wisconsin through 1972

Ground water, a plentiful and largely underdeveloped resource of Wisconsin, has good to excellent chemical quality in most places. This resource is readily available in most parts of the State for municipal, industrial, and rural uses. In 1970, about 0.5 billion gallons of ground water a day was pumped in Wisconsin for all uses (Murray and Reeves, 1972). In addition, underground reservoirs discharge an average of 16 billion gallons per day of water of relatively constant temperature and uniform quality, which maintains the base flow of streams and the level of lakes (Holt, 1964).

Wisconsin↗
USGS1975

Summary appraisals of the nation's ground-water resources – Rio Grande region

The Rio Grande is an interstate and international stream which begins in high mountains of Colorado, flows across New Mexico, and forms the boundary between Texas and Mexico. Precipitation ranges from 8 inches (20 em) to more than 30 inches (76 em), but irrigation is required for growing crops throughout the region. The population of the region has been increasing rapidly, from 750,000 in 1929 to 1,700,000 in 1970, and it is expected to increase to 2,500,000 by 2020. The basic economy of the region was agricultural until recent years. Since 1950, the mining and petroleum industries have increased much more rapidly than agriculture. Annual precipitation on the region is about 86 million acre-feet (110,000 hm 3 ); however, all but 4 million acre-feet (4,900 hm 3 ) is returned to the atmosphere by evapotranspiration. The ground-water reservoirs contain an aggregate of 5,800 million acre-feet (7,200,000 hm 3 ) of fresh and slightly saline water in storage, which could be withdrawn through wells. In contrast, the surface reservoirs have a combined storage capacity of only 18 million acre-feet (22,000 hm 3 ). Thick deposits of valley fill in stream and intermontane valleys comprise the principal ground-water reservoirs. In most areas they are capable of yielding large supplies of water to wells. In some areas, limestone constitutes major aquifers. Withdrawal of ground water in the region in 1970 was 2.7 million acre-feet (3,300 hm 3 ), of which 88 percent was used for irrigation. About 53 percent of the water withdrawn was consumed. Ground water has been "mined" in some areas, and severe declines in water levels have resulted. The loss of water by evapotranspiration in wetlands and phreatophyte areas is 2.5 million acre-feet (3,100 hm 3 ) per year. In comparison, about 3. 7 million acre-feet (4,600 hm 3 ) per year of surface water and ground water is consumed by man's activities. Salvage of water lost to noneconomic evapotranspiration in wet and phreatophyte-infested areas offers the greatest possibility of improving the effective water supply in the region. Salvage of half the water lost would increase the effective supply by 1.2 million acre-feet (1,500 hm 3 ) per year. The usable water supply could be increased tremendously by drawing on the large reserve of ground water in storage, but this withdrawal could affect the flow of streams in some areas. The region appears to offer several possibilities for utilizing underground space for purposes other than the withdrawal of water, such as waste disposal, artificial recharge, water-quality control, and development of geothermal energy. Planners for ground-water management should have detailed information on the physical parameters that affect ground water, so improved management would be possible.

Colorado, New Mexico, Texas↗
USGS2007

Atrazine and metolachlor occurrence in shallow ground water of the United States, 1993 to 1995: Relations to explanatory factors

Since 1991, the U.S. Geological Survey has been conducting the National Water Quality Assessment (NAWQA) Program to determine the quality of the Nation's water resources. In an effort to obtain a better understanding of why pesticides are found in shallow ground water on a national scale, a set of factors likely to affect the fate and transport of two herbicides in the subsurface were examined. Atrazine and metolachlor were selected for this discussion because they were among the most frequently detected pesticides in ground water during the first phase of the NAWQA Program (1993 to 1995), and each was the most frequently detected compound in its chemical class (triazines and acetanilides, respectively). The factors that most strongly correlated with the frequencies of atrazine detection in shallow ground-water networks were those that provided either: (1) an indication of the potential susceptibility of ground water to atrazine contamination, or (2) an indication of relative ground-water age. The factors most closely related to the frequencies of metolachlor detection in ground water, however, were those that estimated or indicated the intensity of the agricultural use of metolachlor. This difference is probably the result of detailed use estimates for these compounds being available only for agricultural settings. While atrazine use is relatively extensive in nonagricultural settings, in addition to its widespread agricultural use, metolachlor is used almost exclusively for agricultural purposes. As a result, estimates of agricultural applications provide a less reliable indication of total chemical use for atrazine than for metolachlor. A multivariate analysis demonstrated that the factors of interest explained about 50 percent of the variance in atrazine and metolachlor detection frequencies among the NAWQA land-use studies examined. The inclusion of other factors related to pesticide fate and transport in ground water, or improvements in the quality and accuracy of the data employed for the factors examined, may help explain more of the remaining variance in the frequencies of atrazine and metolachlor detection.

Journal of the American Water Resources Associatio↗
USGS2005

Effects of urban storm-runoff control on ground-water recharge in Nassau County, New York

Before urban development, most ground-water recharge on Long Island, New York, occurred during the dormant season, when evapotranspiration is low. The use of recharge basins for collection and disposal of urban storm runoff in Nassau County has enabled ground-water recharge to occur also during the growing season. In contrast, the use of storm sewers to route storm runoff to streams and coastal waters has resulted in a decrease in ground-water recharge during the dormant season. The net result of these two forms of urban storm-runoff control has been an increase in annual recharge of about 12 percent in areas served by recharge basins and a decrease of about 10 percent in areas where storm runoff is routed to streams and tidewater. On a countywide basis, annual ground-water recharge has remained nearly the same as under predevelopment conditions, but its distribution pattern has changed. Redistribution resulted in increased recharge in the eastern and central parts of the county, and decreased recharge in the western and nearshore areas. Model simulation of recharge indicates that the water-table altitude has increased by as much as 5 ft above predevelopment levels in areas served by recharge basins and declined by as much as 3 feet in areas where stormwater is discharged to streams and tidewater.

Groundwater↗
USGS1996

Assessment of severity and distribution of corrosive ground water in Pennsylvania

Relations between corrosive ground water, water chemistry, and geology in Pennsylvania were evaluated by use of a modified version of the Langelier Saturation Index (LSIsn) and a geologic contact dataset in a Geographic Information System. Water-chemistry information for water samples collected from 4,839 combined private and public-supply wells from 1900 to 1993 was used to calculate the LSIsn. Thirty-eight lithologic subgroups within four major rock types-carbonate, siliciclastic, crystalline, and unconsolidated-in Pennsylvania were grouped together if the mean of ranked LSIsn values were not significantly different. A water is considered corrosive if the LSIsn value is negative, preventing the precipitation of calcium carbonate, therefore, allowing corrosive reactions with the interior of piping systems. Statistical tests of the LSIsn values show the least corrosive waters are in the carbonate lithologic subgroup, and the most corrosive waters are in the quartzite lithologic subgroup. Approximately 58 percent of the 4,839 LSIsn values were considered moderately to extremely corrosive. A map showing the location of 4,839 wells and associated corrosivity range within 11 lithologic subgroups will aid in identifying potential areas of corrosive ground water in Pennsylvania.

Open-File Report↗
USGS1996

Hydrogeology and simulation of ground-water flow at the South Well Field, Columbus, Ohio

The City of Columbus, Ohio, operates four radial collector wells in southern Franklin County. The 'South Well Field' is completed in permeable outwash and ice-contact deposits, upon which flow the Scioto River and Big Walnut Creek. The wells are designed to yield approximately 42 million gallons per day; part of that yield results from induced infiltration of surface water from the Scioto River and Big Walnut Creek. The well field supplied up to 30 percent of the water supply of southern Columbus and its suburbs in 1991. This report describes the hydrogeology of southern Franklin County and a tran sient three-dimensional, numerical ground-water- flow model of the South Well Field. The primary source of ground water in the study area is the glacial drift aquifer. The glacial drift is composed of sand, gravel, and clay depos ited during the Illinoian and Wisconsinan glaciations. In general, thick deposits of till containing lenses of sand and gravel dominate the drift in the area west of the Scioto River. The thickest and most productive parts of the glacial drift aquifer are in the buried valleys in the central and eastern parts of the study area underlying the Scioto River and Big Walnut Creek. Horizontal hydraulic conductivity of the glacial drift aquifer differs spa tially and ranges from 30 to 375 feet per day. The specific yield ranges from 0.12 to 0.30. The secondary source of ground water within the study area is the underlying carbonate bedrock aquifer, which consists of Silurian and Devonian limestones, dolomites, and shales. The horizontal hydraulic conductivity of the carbonate bedrock aquifer ranges from 10 to 15 feet per day. The storage coefficient is about 0.0002. The ground-water-flow system in the South Well Field area is recharged by precipitation, regional ground-water flow, and induced stream infiltration. Yearly recharge rates varied spatially and ranged from 4.0 to 12.0 inches. The three-dimensional, ground-water-flow model was constructed by use of the U.S. Geological Survey three-dimensional finite-difference ground-water-flow code. Recharge, boundary flux, and river leakage are the principal sources of water to the flow system. The study area is bounded on the north and south by streamlines, with flow entering the area from the east and west. Areal recharge is contributed throughout the study area, although a comparatively high percentage of precipitation reaches the water table in the area east of the Scioto River where little surface drain age exists. Ground-water flow is downward in the uplands of the Scioto River, and upward near the river in the glacial drift and carbonate bedrock aquifers. The numerical model contains 53 rows, 45 columns, and 3 layers. The uppermost two layers represent the glacial drift. The bottom layer represents the carbonate bedrock. The horizontal model grid is variably spaced to account for differences in available data and to simulate heads accurately in specific areas of interest. The length and width of grid cells range from 200 to 2,000 feet; the finer spacings are designed to increase detail in the areas near the collector wells. The model uses 7,155 active nodes. Measurements of water levels from October 1979 were used to represent steady-state conditions before municipal pumping at the well field began. Measurements made during March 1986 were used to represent steady-state conditions after commencement of pumping at the well field. Water levels measured during March 1986 - June 1991 were used for calibration targets in the transient simulations. The transient model was discretized into eight stress periods of 93 to 487 days on the basis of recharge, well-field pumpage, and available water-level data. Transient model calibration was based on seven sets of hydraulic-head measure ments made during March 1986 - June 1991. This time period includes large-scale increases in well- field production associated with a drought in the summer of 1988, an

Water-Resources Investigations Report↗
USGS2005

Use of chemical and isotopic tracers to characterize the interactions between ground water and surface water in mantled karst

In the mantled karst terrane of northern Florida, the water quality of the Upper Floridan aquifer is influenced by the degree of connectivity between the aquifer and the surface. Chemical and isotopic analyses [ 18 O/ 16 O (δ 18 O), 2 H/ 1 H (δD), 13 C/ 12 C (δ 13 C), tritium ( 3 H), and strontium‐87/strontium‐86 ( 87 Sr/ 86 Sr)] along with geochemical mass‐balance modeling were used to identify the dominant hydrochemical processes that control the composition of ground water as it evolves downgradient in two systems. In one system, surface water enters the Upper Floridan aquifer through a sinkhole located in the Northern Highlands physiographic unit. In the other system, surface water enters the aquifer through a sinkhole lake (Lake Bradford) in the Woodville Karst Plain. Differences in the composition of water isotopes (δ 18 O and <δD) in rainfall, ground water, and surface water were used to develop mixing models of surface water (leakage of water to the Upper Floridan aquifer from a sinkhole lake and a sinkhole) and ground water. Using mass‐balance calculations, based on differences in δ 18 O and δD, the proportion of lake water that mixed with meteoric water ranged from 7 to 86% in water from wells located in close proximity to Lake Bradford. In deeper parts of the Upper Floridan aquifer, water enriched in 18 O and D from five of 12 sampled municipal wells indicated that recharge from a sinkhole (1 to 24%) and surface water with an evaporated isotopic signature (2 to 32%) was mixing with ground water. The solute isotopes, δ 13 C and 87 Sr/ 86 Sr, were used to test the sensitivity of binary and ternary mixing models, and to estimate the amount of mass transfer of carbon and other dissolved species in geochemical reactions. In ground water downgradient from Lake Bradford, the dominant processes controlling carbon cycling in ground water were dissolution of carbonate minerals, aerobic degradation of organic matter, and hydrolysis of silicate minerals. In the deeper parts of the Upper Floridan aquifer, the major processes controlling the concentrations of major dissolved species included dissolution of calcite and dolomite, and degradation of organic matter under oxic conditions. The Upper Floridan aquifer is highly susceptible to contamination from activities at the land surface in the Tallahassee area. The presence of post‐ 1950s concentrations of 3 H in ground water from depths greater than 100 m below land surface indicates that water throughout much of the Upper Floridan aquifer has been recharged during the last 40 years. Even though mixing is likely between ground water and surface water in many parts of the study area, the Upper Floridan aquifer produces good quality water, which due to dilution effects shows little if any impact from trace elements or nutrients that are present in surface waters.

Ground Water↗
USGS1983

Ground-water quality data for Oklahoma, 1981

The U.S. Geological Survey has collected data on Oklahoma's ground-water resources since 1934. Most of these data were collected as part of specific ground-water studies conducted in cooperation with various Federal, State, and local agencies. Ground-water quality data, as well as data on construction, yield, water levels, and other physical well parameters collected prior to 1981 are available from the U.S. Geological Survey, Oklahoma District Office. Although water-quality data for wells, test holes, and springs have been published, they are scattered though a variety of reports and are not readily available on a statewide basis. The purpose of this report is to make available, annually, all of the ground-water quality data collected by the U.S. Geological Survey in the Sate of Oklahoma. This report contains ground-water quality data collected in 1981 from 524 sites in 15 counties, predominately in eastern Oklahoma.

Open-File Report↗
USGS2004

Simulated effects of impoundment of lake seminole on ground-water flow in the upper Floridan Aquifer in southwestern Georgia and adjacent parts of Alabama and Florida

Hydrologic implications of the impoundment of Lake Seminole in southwest Georgia and its effect on components of the surface- and ground-water flow systems of the lower Apalachicola?Chattahoochee?Flint (ACF) River Basin were investigated using a ground-water model. Comparison of simulation results of postimpoundment drought conditions (October 1986) with results of hypothetical preimpoundment conditions (a similar drought prior to 1955) provides a qualitative measure of the changes in hydraulic head and ground-water flow to and from streams and Lake Seminole, and across State lines caused by the impoundment. Based on the simulation results, the impoundment of Lake Seminole changed ground-water flow directions within about 20?30 miles of the lake, reducing the amount of ground water flowing from Florida to Georgia southeast of the lake. Ground-water storage was increased by the impoundment, as indicated by a simulated increase of as much as 26 feet in the water level in the Upper Floridan aquifer. The impoundment of Lake Seminole caused changes to simulated components of the ground-water budget, including reduced discharge from the Upper Floridan aquifer to streams (315 million gallons per day); reduced recharge from or increased discharge to regional ground-water flow at external model boundaries (totaling 183 million gallons per day); and reduced recharge from or increased discharge to the undifferentiated overburden (totaling 129 million gallons per day).

Alabama, Florida, Georgia↗
USGS1992

Ground-water levels and directions of flow in the vicinity of a well field, Elkhart, Indiana, December 1989

Water levels were measured in 51 observation wells in the vicinity of the Elkhart Water Works Main Street well field during 5 days of normal pumping at the well field and little or no recharge to the ground water from precipitation. Water levels were measured once each day during December 18-22, 1989. Water-level altitudes were plotted and contoured on maps to determine the distribution of ground-water levels and directions of flow in the unconfined sand and gravel aquifer tapped by the well field. Measured ground-water levels ranged from about 7.5 to 30 feet below land surface. Ground-water levels were highest north and northwest of the Main Street well field and lowest at the Main Street well field and near the St. Joseph River. Regional ground-water flow is toward the south or southeast. Ground-water levels near the river are higher than the river stage, indicating that ground water discharges to the river. As a result of pumping, three cones of depression have formed in the water table in the mapped area. A small cone of depression northwest of the Main Street well field is caused by industrial pumping. Two cones of depression have formed at the Main Street well field-one in the eastern part of the well field and one in the western part of the well field. Horizontal hydraulic gradients are variable in the study area but are largest in the eastern part of the Main Street well field and near the St. Joseph River. In general, water levels measured in seven sets of paired wells do not indicate a vertical hydraulic gradient; however, a downward gradient was measured in one set of paired wells near a pumped area at the Main Street well field.

Indiana↗
USGS1964

Geology and ground-water resources of Washington County, Colorado

Washington County, in northeastern Colorado, has an area of 2,520 square miles. The eastern two-thirds of the county, part of the High Plains physiographic section, is relatively flat and has been moderately altered by the deposition of loess and dune sand, and by stream erosion. The western one-third is a part of the South Platte River basin and has been deeply dissected by tributary streams. The soils and climate of the county are generally suited for agriculture, which is the principal industry. The rocks that crop out in the county influence the availability of ground water. The Pierre Shale, of Late Cretaceous age, underlies the entire area and ranges in thickness from 2,000 to 4,500 feet. This dense shale is a barrier to the downward movement of water and yields little or no water to wells. The Chadron Formation, of Oligocene age, overlies the Pierre Shale in the northern and central parts of the area. The thickness of the formation ranges from a few feet to about 300 feet. Small to moderate quantities of water are available from the scattered sand lenses and from the highly fractured zones of the siltstone. The Ogallala Formation, of Pliocene age, overlies the Chadron Formation and in Washington County forms the High Plains section of the Great Plains province. The thickness of the Ogallala Formation ranges from 0 to about 400 feet, and the yield from wells ranges from a few gallons per hour to about 1,500 gpm. Peorian loess, of Pleistocene age, and dune sand, of Pleistocene to Recent age, mantle a large pan of the county and range in thickness from a few inches to about 120 feet Although the loess and dune sand yield little water to wells, they absorb much of the precipitation and conduct the water to underlying formations. Alluvium, of Pleistocene and Recent age, occupies most of the major stream valleys in thicknesses of a few feet to about 250 feet. The yield of wells tapping the alluvium ranges from a few gallons per minute to about 3,000 gpm, according to the thickness of saturated material. Development of ground water for irrigation has been generally restricted to the South Platte, Arikaree, and Beaver valleys. There were 134 irrigation wells, 3 industrial wells, and 10 municipal wells in the county in 1959. The annual ground-water pumpage from Washington County is estimated to be 18,000 acre-ft; about 10,000 acre-ft is from the High Plains ground-water province. Although some ground water enters the county as underflow, most of the recharge to ground-water reservoirs is from precipitation on the land surface. Recharge to the Ogallala Formation in the county is assumed to be approximately equal to the natural discharge from the county by underflow because ground-water withdrawals are from storage, and no other significant amount of natural discharge is apparent. Undertow in the Ogallala was calculated to be 83,000 acre-ft per year and the rate of recharge from precipitation to be about 0.95 inch per year. Neither recharge nor discharge was calculated for that part of the county in the South Platte River basin. All ground water in Washington County has a high proportion of carbonate and is classed as hard to very hard. The sodium-adsorption-ratio for all samples analyzed was below the limit recommended for irrigation water. All the water from the Ogallala Formation and most of the water from the Chadron Formation is suitable for domestic use. Some water from the alluvial deposits overlying the Pierre Shale was exceptionally high in calcium, magnesium, and sodium sulfates. Ground water has been heavily developed for irrigation in the South Platte valley and in some parts of the Beaver and Arikaree valleys. Some additional areas, however, could be developed in the latter two valleys. Large quantities of ground water in the Ogallala Formation are available for future development. The quantity of water in storage in the High Plains ground-water province in Washington County is about 6.5 million acre-f

Water Supply Paper↗
USGS1997

Pesticides in surface and ground water of the San Joaquin-Tulare basins, California: Analysis of available data, 1966 Through 1992

Available pesticide data (1966-92) for surface and ground water were analyzed for the San Joaquin-Tulare Basins, California, one of 60 large hydrologic systems being studied as part of the National Water-Quality Assessment Program of the U.S. Geological Survey. Most of the pesticide data were for the San Joaquin Valley, one of the most intensively farmed and irrigated areas of the United States. Data were obtained from the Storage and Retrieval data base of the U.S. Environmental Protection Agency, the water-quality data base of the U.S. Geological Survey, and from data files of State agencies. Pesticides detected in surface water include organochlorine pesticides, organophosphate pesticides, carbamate pesticides, and triazine herbicides. Pesticides detected in ground water include triazine and other organonitrogen herbicides and soil fumi gants. Surface-water data indicate seasonal patterns for the detection of organophosphate and carbamate pesticides, which are attributed to their use on almond orchards and alfafa fields. Organochlorine pesticides were detected primarily in river-bed sediments. Concentrations detected in bed sediments of the San Joaquin River near Vernalis are among the highest of any major river system in the United States. Patterns and timing of pesticide use indicate that pesticides might be present in surface-water systems during most months of a year. The most commonly detected pesticide in ground water is the soil fumigant, dibromochloropropane. Dibromochloropropane, used primarily on vineyards and orchards, was detected in ground water near the city of Fresno. Triazine and other organonitrogen herbicides were detected near vineyards and orchards in the same general locations as the detections of dibromochloropropane. Pesticides were detected in ground water of the east side of the valley floor, where the soils are sandy or coarsegrained, and water-soluble pesticides with long environmental half-lives were used. In contrast, fewer pesticides were detected in ground water of the west side of the valley, where soils generally are finer grained.

California↗
USGS1998

Technology Transfer Opportunities: Automated Ground-Water Monitoring, A Proven Technology

Introduction The U.S. Geological Survey (USGS) has developed and tested an automated ground-water monitoring system that measures and records values of selected water-quality properties and constituents using protocols approved for manual sampling. Prototypes using the automated process have demonstrated the ability to increase the quantity and quality of data collected and have shown the potential for reducing labor and material costs for ground-water quality data collection. Automated ground-water monitoring systems can be used to monitor known or potential contaminant sites, such as near landfills, underground storage tanks, or other facilities where potential contaminants are stored, to serve as early warning systems monitoring ground-water quality near public water-supply wells, and for ground-water quality research.

Fact Sheet↗