Search USGS⌕ Search

SEARCH · Search USGS

Results for “Hydrology”

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

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

At least 901 records · Page 50Linked to original sources
USGS1985

Background hydrologic information in potential lignite mining areas in north-central Mississippi, August 1984

The U.S. Geological Survey, in cooperation with the Mississippi Department of Natural Resources, Bureau of Geology, is conducting a hydrologic data collection program in potential lignite-producing areas in Mississippi. During the last two weeks of August 1984, hydrologic data were collected at 15 stream sites that drain potential lignite mining areas in Lafayette, Calhoun, and Yalobusha Counties. Main channel widths ranged from approximately 60 feet at three streams (Coon Creek near Toccopula, Muckaloon Creek near Tula, and Hurricane Creek near Velma) to approximately 120 feet at two streams (Potlockney Creek near Tula, and Savannah Creek near Bruce). Maximum water depths ranged from less than 1.0 foot at most streams to over 5.0 feet at sites on Potlockney Creek near Tula and McGill Creek near Sarepta. Stream discharge ranged from 0.32 cubic feet per second in Persimmon Creek near Bruce to 18.5 cubic feet per second in Puskus Creek near Etta. The specific conductance of stream water ranged from 25 to 160 microsiemens and dissolved solids concentrations ranged from 22 to 91 mg/L (milligrams per liter). Most major ion concentrations were less than 10 mg/L with the exception of calcium (11 mg/L), sodium (12 mg/L) and sulfate (18 mg/L) in the water of Persimmon Creek near Bruce. Dissolved oxygen concentrations were greater than 5.0 mg/L at all but one site. Turbidity values were generally less than 50 units. Nitrate plus nitrite concentrations were equal to or less than 0.10 mg/L in all streams except in Potlockney Creek near Tula where the concentration was 0.11 mg/L. Copper and selenium concentrations in the water at all sampling sites ranged from below the detection limits (1 microgram/g) to 4 micrograms/g (micrograms per gram) and mercury concentrations in bottom material samples ranged from less than 0.01 microgram/g to 0.15 microgram/g. (USGS)

Open-File Report↗
USGS1985

Potential hydrologic effects of ground-water withdrawals from the Dakota Aquifer, southwestern Kansas

A study was conducted to evaluate the effects of potential development of the Dakota aquifer on the layered aquifer system above Permian rocks in a 5,000 sq mi area of southwestern Kansas. Transmissivity of the Dakota aquifer, determined from analyses of pumping tests, ranges from 100 to 7,100 sq ft/day. Water in the Dakota aquifer is a calcium bicarbonate type water, similar to water in the High Plains aquifer, in the subcrop area. However, in areas distant from the subcrop, water in the Dakota aquifer is a sodium bicarbonate type water with dissolved solids concentrations in excess of 500 mg/L. Gradual declines in the potentiometric surface of the Dakota aquifer have occurred since the onset of pumpage in the 1960's; however, water levels in some wells have risen during the late 1970's. A digital computer model of 3-D groundwater flow was developed to simulate hydrologic conditions of a five-layer hydrologic system for 1975-82 conditions. The major components of the simulated 1975-82 water budget were well discharge from the High Plains aquifer and loss of ground water from storage in the High Plains aquifer. Although downward leakage from the High Plains aquifer in the study area represented only 18,000 acre-ft of the 1,365 ,000 acre-ft discharged from the High Plains aquifer during 1982 , it was a major source of inflow to the Dakota aquifer. Changes in storage in the Dakota aquifer in the study area during 1982 were about 5,000 acre-ft. A base-line projection was made using 1982 simulated hydraulic heads from the calibrated model and 1982 rates of pumpage from both the High Plains and the Dakota aquifers for comparison with eight additional projection simulations in which maximum pumpage from the Dakota aquifer at the end of the projections ranged from about 78,000 to 294,000 acre-ft/yr. The results from the projections indicate that: (1) pumpage from the Dakota aquifer will have a limited effect on hydraulic heads in the High Plains aquifer, (2) drawdown in the hydraulic heads in the Dakota aquifer will result in conversion of much of the Dakota aquifer to unconfined conditions, (3) change in storage will become the major water-budget component for the Dakota aquifer, (4) continuation of 1982 rates of withdrawal from the High Plains aquifer will result in dewatering of a substantial part of the aquifer in the study area. (Lantz-PTT)

Open-File Report↗
USGS1985

Delineation of the outcrop of the Edwards Aquifer hydrologically associated with Barton Springs in the Austin area, Texas

This report, prepared in cooperation with the City of Austin, delineates the outcrop of the Edwards aquifer that is hydrologically associated with Barton Springs. The Edwards is a regional aquifer system in central Texas that extends in a narrow belt from Kinney County to Bell County (index map) and lies within an area locally known as the Balcones fault zone. Hydrologic boundaries separate the Edwards auifer into several parts. Barton Springs is the major discharge point of the part of the Edwards aquifer in the Austin area (southern Travis and northern Hays Counties).

Open-File Report↗
USGS1986

Annotated bibliography of the hydrology, geology, and geothermal research of the Jemez Mountains and vicinity, north-central New Mexico

The Jemez Mountains volcanic complex, located in north-central New Mexico at the intersection of the Rio Grande rift and Jemez lineament, is a potential location for geothermal energy exploration. This bibliography lists selected papers pertaining to the geology, hydrology, geochemistry, geothermometry, geophysics, ecology, and geothermal and hydrologic modeling aspects of the Jemez region. The bibliography is composed of 795 citations with annotations and a subject and author index. (USGS)

New Mexico↗
USGS1986

Hydrologic reconnaissance and summary of existing data on surface and ground-water resources in the Missouri River valley in Woodbury and Monona counties, Iowa, 1985

A hydrologic reconnaissance of the Missouri River valley in western Iowa was begun in 1985. The study area is about 400 sq mi of Missouri River flood plain used mainly for agricultural purposes and is located mostly in parts of Woodbury and Monona Counties, Iowa. The reconnaissance was conducted to determine the extent of hydrologic information available for the study area and to determine if the existing data base is sufficient to support an interpretive investigation to quantify the groundwater/surface water relationships in the area. Extensive information concerning the surface water resources of the area, particularly the Missouri River, is available. Very little information concerning the geometry, hydraulic characteristics and groundwater flow relationships in the alluvial aquifer is available. Information needs to be collected to create an adequate data base for future simulation of groundwater flow and to calibrate any estimates of flow. (USGS)

Open-File Report↗
USGS1986

Selected hydrologic data for Salt Lake Valley, Utah, October 1968 to October 1985

This report contains hydrologic data collected in Salt Lake Valley from October 1968 to October 1985. The report area is bounded by the Wasatch Range on the east, the Oquirrh Mountains on the west, the Traverse Mountains on the south, and the boundary between Davis and Salt Lake Counties on the north. Hely and others (1971) defined two aquifers of major importance in the valley the principal aquifer and the shallow aquifer. The principal aquifer is a source of water for public supply and industry, whereas the shallow aquifer in many places contains water that is contaminated and is unsuitable for public supply (Seiler and Waddell, 1984). Most of the data in this report were collected by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights, Salt Lake County Water Conservancy District, Central Utah Water Conservancy District, Granger-Hunter Improvement District, Magna Water Co. and Improvement District, City of Midvale, Salt Lake City Department of Public Utilities, City of Sandyr City of South Salt Lake, Taylorsville Bennion Improvement District, City of West Jordan, Holladay Water Company, and White City Water Co. Some of the data were published previously by Hely, Mower, and Horr (1967, 1968, and 1969), lorns, Mower, and Horr (1966a and b), Marine and Price (1963), and Seiler and Waddell (1984). The purpose of this report is to provide hydrologic data for use by the general public and by officials who manage water resources and to supplement interpretive reports for the area. Information about wells, water levels in wells, and the chemical and physical properties of ground water is given in tables 1-4, and the well locations are shown on plate 1.

Utah↗
USGS1987

Preliminary hydrologic data for wells tested in Nash Draw, near the proposed Waste Isolation Pilot Plant site, southeastern New Mexico

Hydrologic testing was conducted at wells WIPP-25, WIPP-26, WIPP-27, WIPP-28, WIPP-29, and WIPP-30 in Nash Draw near the Waste Isolation Pilot Plant site in southeastern New Mexico. The three water-bearing zones tested were the Magenta Dolomite Member of the Rustler Formation, Culebra Dolomite Member of the Rustler Formation, and the Rustler Formation-Salado Formation contact zone. Inflatable packers were used in a variety of test configurations. Tests conducted include bailing, recovery after perforation, shut in, slug, flow, and pressure pulse. Water pressure response in the tested zone was monitored by a pressure-transducer system. Preliminary hydrologic-test data are tabulated in chronological order for each well. (Lantz-PTT)

Open-File Report↗
USGS1989

Indexes of hydrologic data from selected coal-mining areas in northwestern Colorado

Currently (1988), data from hydrologic studies related to coal mining that have been done in northwestern Colorado since the early 1970 's are stored in the files of private companies and government offices and in various computer systems. To compile these data for additional research, a trip to each office would have to be made to determine the availability and acceptability of the data. The U.S. Geological Survey, in cooperation with the U.S. Bureau of Land Management and the Colorado Mined Land Reclamation Division, has created a database (COALDATA) that includes stream discharge, groundwater levels, and chemical analysis of water samples that were collected by private companies and government agencies other than the U.S. Geological Survey in and near selected coal mines in northwestern Colorado. Indexes in this report list 93 surface water sites and 95 groundwater sites where hydrologic data are available in the COALDATA data base. The indexes also list 62 surface water sites and 480 groundwater sites in the U.S. Geological Survey data base, which is separate from the COALDATA data base and contains only data collected by the U.S. Geological Survey. The combined output of the COALDATA data base and the U.S. Geological Survey data base provides surface water and groundwater data that include most of the study area. (USGS)

Open-File Report↗
USGS1989

Hydrologic data for Indian Creek basin, Fayette and Westmoreland counties, Pennsylvania, 1985-87

Hydrologic data were collected in the Indian Creek basin, Fayette and Westmoreland Counties, Pennsylvania. Since the early 1900's, coal in the basin has been extensively mined by both underground and surface-mining techniques. Data-collection sites were located in mined and unmined areas of the basin. The hydrologic data presented are from 5 continuous-record surfacewater data-collection sites, 1 ground-water well, 23 partial-record surfacewater sites, and 2 continuous-record precipitation gages. Data from the five continuous-record surface-water sites include discharge, specific conductance, temperature, pH, and suspended-sediment concentration. Results of laboratory analyses are reported. Benthic macroinvertebrates collected at 23 sites are listed.

Open-File Report↗
USGS1988

Hydrologic data for the Salt Bayou estuary near Sabine Pass, Texas, October 1984 to March 1986

The Salt Bayou estuary, located in extreme southeast Texas near Sabine Pass, has been altered by construction of the Gulf Intracoastal Waterway. The waterway has interrupted the historical saltwater-freshwater exchange in this important estuary. This alteration may have had a detrimental effect on fish production because of increased salinity, and on waterfowl production because of lower water levels. There have been proposals to develop water control structures in the major channels that would enable some regulation of the saltwater in order to restore the estuary to its approximate historic state. A cooperative effort was initiated by the Louisiana Cooperative Fish and Wildlife Research Unit, the U.S. Fish and Wildlife Service, the Texas Parks and Wildlife Department, and the U.S. Geological Survey to identify the fish species and their transport mechanisms. The U.S. Geological Survey's part of this effort was to describe the present hydrology of Salt Bayou. The purpose of this report is to present the hydrologic data that were collected during October 1984 through March 1986. The initial data-collection network consisted of stage gages at Keith Lake Pass, the mouth of Salt Bayou, Ten Mile Cut, the Intracoastal Waterway, and Star Lake. A stage gage at the Alligator Bayou pumping plant became available later in the study. After 6 months of data were collected, the Ten Mile Cut gage was moved to Wildcow Bayou. The gages at Keith Lake Pass, the mouth of Salt Bayou, Ten Mile Cut, and Wildcow Bayou were equipped with water-velocity recording equipment. The Keith Lake Pass gage also had temperature and specific-conductance recording equipment. Six 24-hour flow investigations were performed to calibrate the velocity recording equipment and to determine the flow at ungaged sites. Before and after these investigations, specific conductance was measured at 43 sites within the estuary. Precipitation data were obtained from National Oceanic and Atmospheric Administration stations at Port Arthur, Anahuac, and Sea Rim State Park and were used to estimate the contribution of freshwater from rainfall. Evaporation data were obtained from Beaumont Research Station and were used to make estimates of water consumption from evapotranspiration. Wind speed and direction were obtained from the National Oceanic and Atmospheric Administration weather station at Sea Rim State Park.

Open-File Report↗
USGS1990

Hydrologic data collected in the vicinity of the proposed gamma-ray and neutrino detector site, Hot Spring County, Arkansas, 1988-89

An abandoned barite mine in Hot Spring County, Arkansas, has been selected as the location for a proposed gamma-ray and neutrino detector site. As part of the hydrologic evaluation of the site, the U.S. Geological Survey in cooperation with the Arkansas Geological Commission collected hydrologic data at selected locations in the vicinity of the abandoned barite mine. Data collected as part of the project included water quality, pond-evaluation, and precipitation data within the abandoned barite mine and flow and water quality data at selected sites in the vicinity of the mine. Water quality samples from within the abandoned mine were collected at three locations in the pond at selected depths. These data included field measurements of specific conductance, pH, water temperature, dissolved oxygen, major ions, and trace metals. Major ion and trace-metal samples were collected at six stream sites, one lake site, and two wastewater pond sites. Pond elevation and precipitation data from within the abandoned barite mine were measured during the period between July 1, 1988 and June 30, 1989. Twevle discharge measurements during the period between June 21, 1988, and June 26, 1989, were collected at six sites in the vicinity of the abandoned barite mine. (USGS)

Open-File Report↗
USGS1990

Hydrologic activities of the U.S. Geological Survey in support of the Radionuclide Migration Program, Nevada Test Site and vicinity, Nye County, Nevada, fiscal year 1987

Hydrologic activities during the 1987 fiscal year by the U.S. Geological Survey in support of the Radionuclide Migration Program at the Nevada Test Site are summarized. These activities included monitoring groundwater levels; compiling and entering geohydrologic data into the U.S. Geological Survey computerized groundwater database; providing technical support to the Radionuclide Migration Committee and the Containment Evaluation Panel; and the planning, drilling, and sampling of the UE20n-1 hole. Groundwater levels were monitored continuously at 2 wells and intermittently at 36 selected wells, test holes, and emplacement holes. Selected monthly water-level measurements are listed for the continuously monitored wells and intermittent measurements are listed for the selected wells, test holes, and emplacement holes. Progress continued on four groundwater hydrology reports of the Nevada Test Site area. (Thacker-USGS, WRD)

Open-File Report↗
USGS1990

Surface-water hydrology of Honey Lake Valley, Lassen County, California, and Washoe County, Nevada

Honey Lake Valley straddles the state line of California and Nevada, about 35 miles north of Reno; about three-fourths of the area is in California. In this report, Honey Lake Valley (also referred to as the "basin") includes the entire area within the hydrographic boundary (fig. 1). Susanville, Calif., in the northwest part of the basin, is the largest town. Population is increasing rapidly both in the Susanville area and in the Reno area of adjacent Washoe County, Nev. Both Lassen and Washoe Counties have identified water resources in Honey Lake Valley as a possible source to meet their needs for future development. An important component of an assessment of the availability of additional long-term supply is an appraisal of surface-water resources. The U.S. Geological Survey, in cooperation with the California Department of Water Resources and the Nevada Division of Water Resources, began a hydrologic assessment of the area in 1987. The study was primarily an appraisal of ground-water resources, but it also included an assessment of surface-water resources. The purpose of this map report is to present the results of the surface-water assessment, including (1) a broad overview of surface-water conditions in the basin, (2) an estimate of mean annual streamflow to the valley floor, and (3) an evaluation of the characteristics of Honey Lake. This report will be republished by the U.S. Geological Survey as a Hydrologic-Investigations Atlas. Results of this study related to ground-water resources of the basin are discussed in a separate report (Handman and others, 1990) and are summarized in a short "Water Fact Sheet" by Handman (1990).

California, Nevada↗
USGS1991

Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1990

Hydrologic data for a study of pre-lllinoian glacial till were collected during the 1990 water year at a site in Linn County, Iowa. A hydrologic-data-collection network, consisting of 22 observation wells and a meteorological station, was installed at the site to describe the hydraulic properties of the till. Recorders were installed on 12 of the wells to continuously monitor water levels. Rainfall at the study site from April to October 1990, totaled 35.49 inches. The greatest monthly rainfall (13.15 inches) occurred in June. The greatest daily rainfall (6.00 inches) occurred on June 16. For the 16 wells less than 50 feet in depth, the highest water levels were recorded during the 4 months of greatest rainfall (May-August 1990). Water levels in the four deepest wens, completed in unconsolidated material, rose throughout the data-collection period. One well had water levels greater than the top of the well casing for most of the period from mid-May to mid-September 1990. A water-quality minimonitor was installed on one observation well near the top of the water table to monitor temporal changes in groundwater quality. For April through September 1990, the daily mean specific conductance ranged from 705 to 864 microsiemens per centimeter at 25 degrees Celsius, the daily mean water temperature ranged from 5.2 to 15.6 degrees Celsius, and the daily median pH remained nearly constant at 7.0 to 7.2 standard units. Ten unvented, vibrating-wire, pressure transducers with internal thermistors were buried in two boreholes at upgradient and downgradient locations to record hydraulic pressure arid water temperature at selected depths.

Iowa↗
USGS1991

Hydrologic data for the Big Spring basin, Clayton County, Iowa; water year 1989

Hydrologic data were collected in the Big Spring Basin located in Clayton County, Iowa, during the 1989 water year. The data were collected in cooperation with the Iowa Department of Natural Resources, Geological Survey Bureau, to provide information on variation and movement of agricultural chemicals in the hydrologic cycle in the Big Spring Basin. Precipitation, stream, and ground-water data were collected. Total rainfall in the basin ranged from 20.0 to 24.4 inches. The greatest monthly rainfall was in August. Calcium and sulfate were the predominant ions in the rain and the median nitrate and ammonia concentrations as nitrogen were 0.40 and 0.63 mg/L (milligrams per liter), respectively. Stream discharge, water temperature, specific conductance, and pH were monitored continuously, and monthly water-quality samples were collected at three sites in the basin. The predominant ions in Roberts Creek, at the site where it leaves the basin, were calcium, magnesium, and bicarbonate. Nitrate plus nitrite as nitrogen concentrations ranged from 0.2 to 6.2 mg/L. Pesticide concentrations in 23 samples ranged from less than 0.10 μ /L (micrograms per liter) to 4.4 μ /L. Atrazine was detected in 100 percent of the samples, cyanazine and metolachlor in 43 percent of the samples and alachlor in 35 percent of the samples. At Big Spring, the ground-water discharge point, the daily mean water temperature ranged from 5.1 to 10.6 degrees Celsius, the daily mean specific conductance ranged from 271 to 793 micro Siemens per centimeter at 25 degrees Celsius, and the daily median pH ranged from 63 to 7.1. Calcium, magnesium, and bicarbonate were the predominant ions in solution. Nitrate plus nitrite as nitrogen concentrations ranged from 2.0 to 7.4 mg/L. Atrazine was detected in 95 percent of the samples, cyanazine was detected in 26 percent of the samples, and metolachlor and alachlor were detected in 16 percent of the samples. The maximum atrazine concentration was 3.3 μ /L. Water levels in the unconsolidated aquifers and the Galena aquifer were highest in the spring after snowmelt and in September after the greatest monthly rainfall. Water levels in the Saint Peter aquifer declined by approximately 0 J to 3.0 feet. During a baseflow seepage study, August 16 and 17, the measured discharge lost by streams in the basin was 2.82 cubic feet per second, the measured dissolved nitrogen load lost was 80 pounds per day, and the measured atrazine load lost was 0.002 pound per day. The total measured discharge and total dissolved nitrogen load leaving the basin in streams was 0.07 cubic feet per second and less than 20 pounds per day, respectively.

Iowa↗
USGS1991

Hydrology of the Texas Gulf Coast aquifer systems

A complex, multilayered ground-water flow system exists in the Coastal Plain sediments of Texas. The Tertiary and Quaternary clastic deposits have an areal extent of 114,000 square miles onshore and in the Gulf of Mexico. Two distinct aquifer systems are recognized within the sediments, which range in thickness from a few feet to more than 12,000 feet The older system--the Texas coastal uplands aquifer system-consists of four aquifers and two confining units in the Claiborne and Wilcox Groups. It is underlain by the practically impermeable Midway confining unit or by the top of the geopressured zone. It is overlain by the nearly impermeable Vicksburg-Jackson confining unit, which separates it from the younger coastal lowlands aquifer system. The coastal lowlands aquifer system consists of five permeable zones and two confining units that range in age from Oligocene to Holocene. The hydrogeologic units of both systems are exposed in bands that parallel the coastline. The units dip and thicken toward the Gulf. Quality of water in the aquifer systems is highly variable, with dissolved solids ranging from less than 500 to 150,000 milligrams per liter. Substantial withdrawal from the aquifer systems began in the early 1900's and increased nearly continuously into the 1970's. The increase in withdrawal was relatively rapid from about 1940 to 1970. Adverse hydrologic effects, such as saltwater encroachment in coastal areas, land-surface subsidence in the Houston-Galveston area, and long-term dewatering in the Whiter Garden area, were among some of the factors that caused pumping increases to slow or to cease in the 1970's and 1980's. Ground-water withdrawals in the study area in 1980 were about 1.7 billion gallons per day. Nearly all of the withdrawal was from four units: Permeable zones A, B, and C of Miocene age and younger, and the lower Claiborae-upper Wilcox aquifer. Ground-water levels have declined hundreds of feet in the intensively pumped areas of Houston-Galveston, Kingsville, Winter Garden, and Lufkin-Nacogdoches. Water-level declines have caused inelastic compaction of clays which, in turn, has resulted in land-surface subsidence of more than one foot in an area of about 2,000 square miles. Maximum subsidence of nearly 10 feet occurs in the Pasadena area east of Houston. A three-dimensional, variable-density digital model was developed to simulate predevelopment and transient flow in the aquifer systems. The modeled area is larger than the study area, and includes adjacent parts of Louisiana and Mexico. The transient model calibration period was from 1910 (predevelopment) to 1982. Model-generated head distributions, water-level hydrographs, and land-surface subsidence were matched to measured data in selected, intensively pumped areas. For the study area, mean horizontal hydraulic conductivity in the calibrated model ranges from 10 feet per day for the middle Wilcox aquifer to 25 feet per day for permeable zone A. Mean transmissivity ranges from about 4,600 feet squared per day for the middle Claiborne aquifer to about 10,400 feet squared per day for permeable zone D. Mean vertical hydraulic conductivity ranges from 1.1x10 -5 feet per day for the Vicksburg-Jackson confining unit, to 3.8x10 -3 feet per day for permeable zone A. Mean values of calibrated storage coefficient range from 52x10 -4 for the middle Claiborne aquifer to 1.7x10 -3 for the middle Wilcox aquifer and permeable zone C. Calibrated inelastic specific storage values for clay beds in permeable zones A, B, and C in the Houston-Galveston area are 8.5x10 -5 , 8.0x10 -5 , and 8.0x10 -6 feet -1 , respectively. These values are 85, 80, and 8 times greater than the estimated elastic specific storage value for the clays in permeable zones A, B, and C, respectively. Recharge rates were mapped for predevelopment conditions as determined from a steady-state model calibration. A maximum rate of 3 inches per year was simulated in small areas, and the average rate for the study area was 034 inch per year. Total simulated recharge was 85 million cubic feet per day in the outcrop area. Recharge was equal to discharge in outcrop areas (79 million cubic feet per day) plus net lateral flow out of the study area (6 million cubic feet per day). Rates of inflow and outflow to the ground-water system have nearly tripled from predevelopment to 1982 (85 to 276 million cubic feet per day) based on model simulation. Withdrawal of 231 million cubic feet per day was supplied principally by an increase in outcrop recharge and, to a lesser extent, from a decrease in natural discharge and release of water from storage in aquifers and compacting clay beds. The average simulated 1982 recharge rate for the study area was 0.52 inch per year, with a maximum simulated rate of 6 inches per year in Jackson and Wharton Counties. Because withdrawal has caused problems such as saltwater intrusion, land-surface subsidence, and aquifer dewatering, the Texas Department of Water Resources has projected that ground-water use will decline substantially in most of the study area by the year 2030. Some areas remain favorable for development of additional ground-water supplies. Pumping from older units that are farther inland and in areas where potential recharge is greater will minimize adverse hydrologic effects.

Texas↗
USGS1992

Hydrologic data for a study of pre-Illinoian glacial till in Linn County, Iowa, water year 1991

Hydrologic data for a study of pre-lllinoian glacial till were collected during the 1991 water year at a site in Linn County, east-central Iowa. A hydrologic-data-collection network, consisting of a meteorological station, 22 observation wells, and a water-quality minimonitor, was installed at the site to investigate the hydraulic properties of the till. Recorders were installed on 12 of the observation wells to continuously monitor water levels. Rainfall at the study site from October 1990 to September 1991 was 17.86 inches. The greatest monthly rainfall (4.07 inches) occurred in March. The smallest monthly rainfall (0.06 and 0.04 inch) occurred in June and July, respectively. The highest water levels measured in 22 observation wells were recorded from March through May 1991. Water levels in three of the deeper wells, completed in the unweathered glacial till, continued to rise from the time the wells were initially installed in November 1989 until they were bailed for water-quality sampling in May 1991. One well had water levels greater than the top of the well casing for most of the period from March to mid-July. Ten unvented, vibrating-wire pressure transducers with internal thermistors were buried in two boreholes at upgradient and downgradient locations to record hydraulic pressure and water temperature at selected depths. A water-quality minimonitor was installed near the top of the water table to monitor temporal changes in ground-water quality. For October 1990 through September 1991, the daily mean water temperatures ranged from 7.3 to 14.9 degrees Celsius, and the daily median pH values ranged from 6.9 to 7.5 standard units. Herbicide concentrations in rainfall ranged from 0.05 to 1.3 micrograms per liter. Herbicides detected in the largest concentrations included alachlor, atrazine, and metolachlor. Metribuzin was the only herbicide detected in ground-water samples at a concentration of 0.10 micrograms per liter in water from one observation well.

Iowa↗
USGS1992

Selected hydrologic data for Salt Lake Valley, Utah, 1990-92, with emphasis on data from the shallow unconfined aquifer and confining layers

Hydrologic data were collected from wells in the Salt Lake Valley, Utah, from 1990 to 1992, to better understand the hydrologic system in the valley. Most of the data collected are from 36 monitoring wells drilled in June and July 1990 and March and May 1991 using a hollow-stem auger. These wells range from 15.0 to 129.5 feet deep and are completed in the shallow unconfined aquifer, an underlying confining layer, or both. Data from public supply wells and other existing wells completed in aquifers below the confining layers near these monitoring wells are presented in order to compare data from those wells with data from the shallow unconfined aquifer and the underlying confining layers. Field data collected from selected wells and drill holes include well-completion information, lithologic logs, and water-level and field water-quality measurements. Water samples collected from monitoring wells drilled in 1990 and 1991 and from selected existing wells were analyzed for inorganic constituents, trace metals in unfiltered water, volatile organic compounds, organochlorine pesticides, polychlorinated biphenyls, and radionuclides. Core samples were collected from selected monitoring wells drilled in 1990 and 1991 and analyzed for geochemical and geotechnical properties. Cation exchange capacity, carbon concentration, and the concentration of selected elements in core material are presented. Particle size, dry density, moisture content, porosity, hydraulic conductivity, initial void ratio, specific storage, and other properties determined for material in cores from selected monitoring wells also are listed.

Utah↗