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At least 1,135 records · Page 63Linked to original sources
USGS2002

Simulation of Ground-Water Flow in the Middle Rio Grande Basin Between Cochiti and San Acacia, New Mexico

This report describes a three-dimensional, finite difference, ground-water-flow model of the Santa Fe Group aquifer system within the Middle Rio Grande Basin between Cochiti and San Acacia, New Mexico. The aquifer system is composed of the Santa Fe Group of middle Tertiary to Quaternary age and post-Santa Fe Group valley and basin-fill deposits of Quaternary age. Population increases in the basin since the 1940's have caused dramatic increases in ground-water withdrawals from the aquifer system, resulting in large ground-water-level declines. Because the Rio Grande is hydraulically connected to the aquifer system, these ground-water withdrawals have also decreased flow in the Rio Grande. Concern about water resources in the basin led to the development of a research plan for the basin focused on the hydrologic interaction of ground water and surface water (McAda, D.P., 1996, Plan of study to quantify the hydrologic relation between the Rio Grande and the Santa Fe Group aquifer system near Albuquerque, central New Mexico: U.S. Geological Survey Water-Resources Investigations Report 96-4006, 58 p.). A multiyear research effort followed, funded and conducted by the U.S. Geological Survey and other agencies (Bartolino, J.R., and Cole, J.C., 2002, Ground-water resources of the Middle Rio Grande Basin, New Mexico: U.S. Geological Survey Circular 1222, 132 p.). The modeling work described in this report incorporates the results of much of this work and is the culmination of this multiyear study. The purpose of the model is (1) to integrate the components of the ground-water-flow system, including the hydrologic interaction between the surface-water systems in the basin, to better understand the geohydrology of the basin and (2) to provide a tool to help water managers plan for and administer the use of basin water resources. The aquifer system is represented by nine model layers extending from the water table to the pre-Santa Fe Group basement rocks, as much as 9,000 feet below the NGVD 29. The horizontal grid contains 156 rows and 80 columns, each spaced 3,281 feet (1 kilometer) apart. The model simulates predevelopment steady-state conditions and historical transient conditions from 1900 to March 2000 in 1 steady-state and 52 historical stress periods. Average annual conditions are simulated prior to 1990, and seasonal (winter and irrigation season) conditions are simulated from 1990 to March 2000. The model simulates mountain-front, tributary, and subsurface recharge; canal, irrigation, and septic-field seepage; and ground-water withdrawal as specified-flow boundaries. The model simulates the Rio Grande, riverside drains, Jemez River, Jemez Canyon Reservoir, Cochiti Lake, riparian evapotranspiration, and interior drains as head-dependent flow boundaries. Hydrologic properties representing the Santa Fe Group aquifer system in the ground-water-flow model are horizontal hydraulic conductivity, vertical hydraulic conductivity, specific storage, and specific yield. Variable horizontal anisotropy is applied to the model so that hydraulic conductivity in the north-south direction (along model columns) is greater than hydraulic conductivity in the east-west direction (along model rows) over much of the model. This pattern of horizontal anisotropy was simulated to reflect the generally north-south orientation of faulting over much of the modeled area. With variable horizontal anisotropy, horizontal hydraulic conductivities in the model range from 0.05 to 60 feet per day. Vertical hydraulic conductivity is specified in the model as a horizontal to vertical anisotropy ratio (calculated to be 150:1 in the model) multiplied by the horizontal hydraulic conductivity along rows. Specific storage was estimated to be 2 x 10-6 per foot in the model. Specific yield was estimated to be 0.2 (dimensionless). A ground-water-flow model is a tool that can integrate the complex interactions of hydrologic boundary conditions, aquifer materials

Water-Resources Investigations Report↗
USGS1976

Water resources of Lincoln County coastal area, Oregon

The Lincoln County coastal area is underlain by Tertiary volcanic and sedimentary rocks of low permeability that store only a small volume of the annual precipitation which averages 68 inches (1,730 millimeters). Consequently, the Tertiary units yield small quantities of water to wells and furnish little ground-water discharge to maintain the base flow of streams. Although streamflow is normally abundant during the wet season, flow decreases greatly during summer when needed most. Quaternary marine terrace deposits of semiconsolidated sand border the western part of the area and are the most productive aquifers. Several wells drilled into the Quaternary deposits are among the highest producing wells of the area, with yields of 25 to 60 gallons per minute (1.6 to 3.8 liters per second). The Siletz River Volcanics is one of the better aquifers in the area and generally yields water in volumes sufficient for domestic use. The average well drilled into these rocks yields 5 to 10 gallons per minute (0.3 to 0.6 liters per second). Locally, this formation is quite permeable and has a producing well in the study area, with a yield of 120 gallons per minute (7.6 liters per second). Other volcanic rocks of small areal extent and largely untested, are the basalts near Depoe Bay, Cape Foulweather, Yachats, and Cape Perpetua. Wells drilled in January 1976 near Depoe Bay indicate that as much as 125 gal/min (10 L/s) of water can be obtained from wells drilled into the basalt. Tertiary marine sedimentary rocks of siltstone and sandstone are widespread throughout the area. Yields of wells drilled in these rocks are generally low (less than 5 gallons per minute, or 0.3 liters per second), and many wells in these formations produce no usable quantities of ground water. Approximately 5,000,000 acre-feet (6,000 cubic hectometers) of water discharges annually into the Pacific Ocean from all streams along the Lincoln County coast. About 85 percent of the annual streamflow occurs from November through April. Minimum streamflaws occur from August through October when, at times, as little as 450 acre-feet (55 hectometers) per day flows from all streams. Most of the ground water, with the exception of water from some wells drilled in the marine siltstone and sandstone, contains relatively small concentrations of dissolved minerals. Wells that tap the marine deposits at low altitudes have high concentrations of dissolved minerals, particularly sodium and chloride. In general, analyses of water from the 14 streams sampled in Lincoln County show very good chemical quality. The iron content of Depoe and Thiel Creeks is above the Environmental Protection Agency's recommended limit of 0.3 milligrams per liter for drinking water. Annual water use totals 6.7 billion gallons, which is less than 0.5 percent of runoff. About 70 percent of the use is for industrial purposes at one lumber products mill, about 25 percent is for public supplies, and less than 5 percent for irrigation. Water supplies for all municipalities in Lincoln County currently (1975) are obtained from surface-water sources. Because of rapid economic development of the coastal area, it is expected that additional water will be needed in the future. Additional water can be supplied (1) by reservoirs on major streams; (2) by the expansion, in some locations, of present surface-water facilities on small streams; and (3) locally, by an additional small volume of supplemental water from ground-water sources.

Oregon↗
USGS1977

Water resources of the Umatilla Indian Reservation, Oregon

Water resources of the Umatilla Indian Reservation are poorly distributed both geographically and in time. On the reservation, only the Umatilla River and one of its principal tributaries, Meacham Creek, have significant perennial flows. Runoff of the principal streams is largely from snowmelt in the Blue Mountains and is highly variable. The principal aquifers are the Columbia River Basalt Group and the Quaternary alluvium. The basalt underlies the entire reservation to a depth of a few thousand feet, and most wells tap this source. The Quaternary alluvium is present only in the valleys of the principal streams. The alluvium averages about 12 feet (ft) in thickness in the Umatilla River valley, where it has the greatest extent; elsewhere it is generally thinner. Surface-water outflow from the reservation averages about 600 cubic feet per second (ft 3 /s), and the total stream inflow is about 540 ft 3 /s. About 480 ft 3 /s of the outflow is in the Umatilla River, 106 ft 3 /s is in McKay Creek, and 14 ft 3 /s is in other streams. Dependable streamflow, defined here as the 7-day mean low flow that will occur once every 50 years, on the average, is 30 ft 3 /s in Umatilla River above Meacham Creek near Gibbon, 5 ft 3 /s in Meacham Creek below Line Creek at the east boundary, 33 ft 3 /s in Umatilla River at Cayuse, and 14 ft 3 /s in Umatilla River at Pendleton. Monthly mean flows in Umatilla River above Meacham Creek near Gibbon in summer and fall frequently are less than the published recommended minimum flows for spawning and rearing of trout; in the reach of the Umatilla River near Pendleton the summer and fall flows generally are below those recommended minimum flows. Wells in the Columbia River Basalt Group range in depth from a few to 1,910 ft, and their yields range from less than 1 to more than 1,200 gallons per minute (gal/min). Small yields adequate for domestic needs can generally be obtained from the basalt. The depths required for successful wells may be extremely variable. Evaluation of specific-capacity data from wells in the basalt in four geographic areas suggests that the basalt is more permeable beneath the south reservation and the Umatilla River valley, that the permeability decreases on the north reservation, and that it is least in the Blue Mountains. Surface and ground waters generally are of good quality and suitable for most uses. Surface water is soft and generally contains less than 120 milligrams per liter (ug/L) of dissolved solids. Dissolved oxygen in streams is generally at or close to saturation levels at most stream temperatures and discharge rates. Ground water ranges from soft to very hard (28 to 280 mg/L), but it generally ranges between moderately hard to hard (61 to 180 mg/L). Dissolved solids in ground water range from 88 to 561 mg/L, but generally are between 200 and about 250 mg/L. During 1975, an estimated 11 million gallons per day (Mgal/d) of surface and ground water was withdrawn from the reservation for all uses. About 4 Mgal/d was from surface-water sources and 60 percent, or 7 Mgal/d, was from ground-water sources. About 7.2 Mgal/d was used for irrigation, 3.6 Mgal/d for public supply, and the remainder was for domestic and industrial use. About 4 Mgal/d, or 40 percent of the total water withdrawn, was for public supply and for irrigation use outside the reservation boundaries. Local seasonal declines of ground-water levels of 100 ft or more occur in shallow basalt wells in the Umatilla River valley between Mission and the west boundary. The declines are due chiefly to pumping from many small-capacity shallow wells in the basalt for irrigation of lawns and small acreages of pasture or hay. Future potential problems on the reservation include regional decline of ground-water levels in the basalt aquifer and local contamination of surface and ground water from accidental spills of deleterious substances.

Oregon↗
USGS1981

Designation of principal water-supply aquifers in Minnesota

Fourteen aquifers, ranging from Quaternary to Precambrian in age, have been identified as the principal sources of water to wells in Minnesota. Half the municipal population anc nearly all the rural population depend on water from these aquifers. Buried and surficial sand and gravel aquifers of Quaternary age occur in nearly all areas of the State and are composed of outwash, beach-ridge, valley-train, and ice-contact deposits. Cretaceous aquifers, absent in the northeast, are nearly continuous in the western half, and are thin or discontinuous in the central and southeast areas. Sandstone and carbonate rocks of Paleozoic and late Precambrian age in southeastern and northwestern Minnesota comprise the Cedar Valley-Maquoketa-Dubuque-Galena, Red River-Winnipeg, St. Peter, Prairie du Chien-Jordan, Franconia-Ironton-Galesville, and Mount Simon-Hinckley-Fond du Lac aquifers. Aquifers of early Precambrian age occur in all but southeastern Minnesota and include the North Shore Volcanic Group, Sioux Quartzite, Proterozoic metasedimentary rocks, Biwabik Iron-formatIon, and undifferentiated Precambrian rocks. The State's ground water generally contains less than 1,000 milligrams per liter of dissolved solids, except in the extreme southwest, northeast, and western areas. Mineralized water is present at depth throughout the State. Freshwater extends to depths of about 1,000 feet in the center of the Hollandale embayment and in the Twin Cities basin. Six principal water-quality types are present in the .aquifers. Calcium magnesium bicarbonate type water, the most common, is generally present throughout the upper part of the ground-water system.

Minnesota↗
USGS1982

Nitrate-nitrogen concentrations in ground water from three selected areas in Kansas

Nitrate-nitrogen data collected during 1976-79 from 333 wells in western, central, and eastern Kansas were summarized and statistically analyzed on the basis of area, aquifer, and well depth. Concentrations exceeding 10 milligrams per liter occurred generally in wells less than 100 feet in depth, indicating that nitrate-nitrogen concentrations in ground water greater than 10 milligrams per liter commonly are derived from nitrogen sources at or near the land surface, although soluble nitrogen may be derived from fine-grained sediments in some aquifers. Water from shales in central and eastern Kansas and from limestone in eastern Kansas exhibited the highest median concentrations and highest incidence of concentrations above 10 milligrams per liter. Water from 10 percent of the wells in unconsolidated Quaternary deposits in western Kansas and almost 30 percent of the wells in eastern Kansas had nitrate-nitrogen concentrations that exceeded 10 milligrams per liter. Shallow wells in shales, limestones, and unconsolidated Quaternary deposits are highly susceptible to nitrate contamination. Water from unconsolidated Tertiary deposits produced a low incidence of nitrate-nitrogen concentrations greater than 10 milligrams per liter, indicating minimal nitrate contamination from sources at or near the land surface. Sandstones in all areas exhibited the lowest median and lowest incidence of nitratenitrogen concentrations above 10 milligrams per liter.

Kansas↗
USGS1984

Water-resources of western Douglas County, Oregon

In western Douglas County, Quaternary coastal dune sands and marine terrace deposits may have the best potential for ground-water development. Yields of 200 gallons per minute have been reported from wells completed in Quaternary fluvial deposits along the lower Umpqua River. The entire area is underlain by Tertiary marine sediments that yield quantities of water barely adequate for domestic use. On the basis of wells sampled and the constituents analyzed, ground-water quality was generally good, but the recommended criteria level of 300 micrograms per liter for iron was exceeded in about one-third of the samples. Average annual runoff from eight streams in western Douglas County was estimated to range from 2.4 cubic feet per second per square mile for Elk Creek to 6.8 cubic feet per second per square mile for Scholfield Creek. The estimated 7-day , 20-year low flow ranges from 0.01 cubic foot per second per square mile for Weatherly Creek to 3.6 cubic feet per second per square mile for the Smith River. The dissolved-solids of the Umpqua River is small and stable, with little seasonal and yearly variation. Likewise, the eight small streams in the project area have small dissolved-solids but have noticeably higher nitrite plus nitrate nitrogen concentrations than those of the Umpqua River. All the lakes in the project area have dissolved-solids concentrations of less than 100 milligrams per liter and, except for Loon Lake, have limited phosphorus available for algal production. Tahkenitch and Elbow Lakes are considered to be the most active in terms of biological productivity.

Oregon↗
USGS1986

Geohydrology of the southwest alluvial basins regional aquifer- systems analysis, parts of Colorado, New Mexico, and Texas

The Southwest Alluvial Basins study is part of the National Regional Aquifer-Systems Analysis program. Twenty-two structural basins extend from the San Luis Basin in southern Colorado to the Presidio Basin in western Texas. Closed surface-water basins west of the Guadalupe Mountains and east of the Peloncillo Mountains are included in the study. The study area is bounded on the east by predominately Precambrian and Paleozoic rocks. Tertiary and Quaternary volcanics also are present. Tertiary and Quaternary volcanic rocks, and also Mesozoic rocks west of the Espanola and Albuquerque-Belen Basins, form the west boundary. The east and west boundary units converge at the north end of the study area to form the north boundary. The study area extends south to the international border between the United States and Mexico. The Santa Fe Group sediments of late Oligocene to middle Pleistocene age comprise the main aquifer in the area. Estimated maximum depths of sediments in the rift basins range from 8,000 feet in the Tularosa-Hueco Basin to 30,000 feet in the San Luis Basin. The average thickness of sediments in closed basins is about 4,000 feet. Santa Fe deposits are composed of layers of gravel, sand, silt, and clay interbedded with local volcanic flows or tuffs. Lacustrine deposits are more prevalent in the closed basins. Wells produce as much as 2,000 gallons of water per minute. Potentiometric-surface altitudes for 1971-82 indicate that water recharges in the highland areas around the basins and discharges in the center of valleys. Water generally flows from the east and west southward along the axis of the valleys. Ground-water quality for the region has been zoned into calcium sulfate, calcium chloride, magnesium sulfate, magnesium chloride; sodium sulfate, sodium chloride; sodium bicarbonate; and calcium bicarbonate, magnesium bicarbonate types.

Colorado, New Mexico, Texas↗
USGS1985

Evaluation of surface geophysical methods for collection of hydrogeologic data in the Nebraska Sand Hills region

The practicality of using surface geophysical methods for obtaining geohydrologic data in the Nebraska Sand Hills region was studied during the summer of 1984. Seismic refraction and electrical-resistivity equipment were used, because an evaluation of geohydrologic data indicated that results of surveys made with this equipment probably would yield the most useful data. The study area, which included parts of Garfield, Holt, and Wheeler Counties, was selected because it is geohydrologically representative of the eastern part of the Sand Hills region, and because sufficient geohydrologic data were available for use in evaluating the results of geophysical surveys. Geophysical methods were evaluated for their ability to consistently detect selected geohydrologic horizons. These horizons in descending order, are: the water table, the top of Quaternary silt beds, the top of Quaternary sand and gravel beds , the top of the Tertiary Ogallala Formation, and the top of the Cretaceous Pierre Shale. The top of the Pierre Shale generally is the base of the aquifer, which consists of all of the 500 to 700 ft of overlying deposits. Evaluations of the geophysical data indicate that seismic refraction surveys are best suited for determining the depth to the water table, but are not effective in studying beds below the water table. Vertical electrical soundings provided data on the depth to water table and the top of the silt beds. Available geohydrologic data, however, indicate that with some changes in data collection or interpretation techniques, it may be possible to obtain information on the top of the sand and gravel deposits, the top of the Ogallala Formation, and the top of the Pierre Shale with vertical electrical soundings. Use of either geophysical method could enhance the results of geohydrologic investigations in the Nebraska Sand Hills region. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1987

Cenozoic stratigraphy and geologic history of the Tucson Basin, Pima County, Arizona

This report was prepared as part of a geohydrologic study of the Tucson basin conducted by the U.S. Geological Survey in cooperation with the city of Tucson. Geologic data from more than 500 water supply and test wells were analyzed to define characteristics of the basin sediments that may affect the potential for land subsidence induced by groundwater withdrawal. The Tucson basin is a structural depression within the Basin and Range physiographic province. The basin is 1,000 sq mi in units area and trends north to northwest. Three Cenozoic stratigraphic unit--the Pantano Formation of Oligocene age, the Tinaja beds (informal usage) of Miocene and Pliocene age, and the Fort Lowell Formation of Pleistocene age--fill the basin. The Tinaja beds include lower, middle, and upper unconformable units. A thin veneer of stream alluvium of late Quaternary age overlies the Fort Lowell Formation. The Pantano Formation and the lower Tinaja beds accumulated during a time of widespread continental sedimentation, volcanism, plutonism, uplift, and complex faulting and tilting of rock units that began during the Oligocene and continued until the middle Miocene. Overlying sediments of the middle and upper Tinaja beds were deposited in response to two subsequent episodes of post-12-million-year block faulting, the latter of which was accompanied by renewed uplift. The Fort Lowell Formation accumulated during the Quaternary development of modern through-flowing the maturation of the drainage. The composite Cenozoic stratigraphic section of the Tucson basin is at least 20,000 ft thick. The steeply tilted to flat-lying section is composed of indurated to unconsolidated clastic sediments, evaporites, and volcanic rocks that are lithologically and structurally complex. The lithology and structures of the section was greatly affected by the uplift and exhumation of adjacent metamorphic core-complex rocks. Similar Cenozoic geologic relations have been identified in other parts of southern Arizona. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1989

Ground-water-quality-monitoring program in Iowa: Nitrate and pesticides in shallow aquifers

Concern exists about the occurrence of agricultural chemicals, primarily nitrate and pesticides, in shallow ground water. In response to this concern, the focus of the Iowa ground-water-quality-monitoring program has shifted to emphasize nonpoint contaminants. The program, which began in 1982, is operated by the U.S. Geological Survey in cooperation with the University of Iowa Hygienic Laboratory and the Iowa Department of Natural Resources, Geological Survey Bureau and Environmental Protection Division. The objectives are to describe and assess the long-term chemical quality of the principal aquifers in Iowa and to direct water-quality assessment and sampling toward regional ground-water-quality concerns. In the spring of 1985, emphasis was placed on the analysis of pesticides in water samples collected from wells completed in surficial aquifers in Quaternary deposits or from wells less than 200 feet deep or both. Samples from these wells were analyzed for nitrate and selected pesticides. In water samples collected from 515 individual shallow wells, 6 percent had nitrate concentrations larger than the maximum contaminant level for public drinking water of 10 milligrams per liter as nitrogen. The concentrations ranged from less than 0.1 to 53 milligrams per liter as nitrogen. Eighteen percent of the samples had concentrations of nitrate between 5 and 10 milligrams per liter as nitrogen. Water samples from 355 individual municipal wells less than 200 feet deep have been analyzed for pesticides at least once. Detectable concentrations of at least one pesticide, including alachlor, atrazine, cyanazine, dicamba, metolachlor, or metribuzin, were detected in 20 percent of the samples. Atrazine was the most prevalent pesticide; concentrations, which ranged from 0.10 to 21 micrograms per liter, were detected in 18 percent of the samples. The results of the monitoring program indicate a relation between decreasing well depth and the presence of detectable concentrations of nitrate and pesticides. Most nitrate and pesticide detection was in areas where surficial aquifers in Quaternary deposits are the principal source of ground water. Pesticides were detected in samples collected throughout the year; samples collected in late spring and early summer more frequently contained pesticides than the other samples.

Iowa↗
USGS1990

Altitude of potentiometric surface, fall 1985, and historic water-level changes in the Memphis aquifer in western Tennessee

Recharge to the Memphis aquifer of Tertiary age is from precipitation on the outcrop, which forms a broad belt across western Tennessee, or by downward infiltration of water from the overlying fluvial deposits of Tertiary(?) and Quaternary age and alluvium of Quaternary age. In the outcrop-recharge belt, where the Memphis aquifer is under water-table conditions, the potentiometic surface is complex and generally conforms to the topography. To the west of the outcrop-recharge belt where the Memphis aquifer is confined, the potentiometric surface gently slopes westward, and water moves slowly in that direction. A major cone of depression in the potentiometric surface in the Memphis area is the result of long-term (1886-present) pumping at municipal and industrial well fields. Data from five observation wells in the Memphis aquifer indicate that water levels have declined at average rates ranging from less than 0.1 to 1.3 feet per year during the period 1928-85. The largest declines have been in the Memphis area, where withdrawals averaged about 191 million gallons per day in 1985. The record from an observation well located near the center of the major cone of depression in the Memphis area indicates that water levels ceased to decline in about 1975 and that the center of the cone essentially has stabilized. The record from another well away from the center of the cone indicates that water levels are still declining at a low rate, and that the cone is still expanding as a result of the effects of pumping. Water levels in large areas of western Tennessee, away from the effects of pumping, have fluctuated only in response to long-term variations in precipitation on the outcrop-recharge belt. Long-term changes in water levels in these areas have been small.

Tennessee↗
USGS1990

Geology and ground-water resources of the Cockfield Formation in western Tennessee

The Cockfield Formation of the Claiborne Group of Tertiary age underlies approximately 4,000 sq mi in western Tennessee. The formation consists primarily of lenticular beds of very fine to coarse sand, silt, clay, and lignite. The Cockfield Formation has been extensively eroded, and the original thickness is preserved only in a few areas where the formation ranges from 235 to 270 ft in thickness. Recharge to the Cockfield aquifer is from precipitation on sparse outcrops or by downward infiltration of water from the overlying fluvial deposits of Tertiary and Quaternary age and alluvium of Quaternary age or, where present, the overlying Jackson Formation of Tertiary age. Data from two observation wells indicate that water levels have risen at average rates of about 0.5 and 0.7 ft/year during the period 1980-85. Water from the Cockfield aquifer is a calcium bicarbonate type that contains low concentrations of most major constituents, and generally is suitable for most uses. Dissolved-solids concentrations range from 44 to 218 mg/L. Data from two aquifer tests indicate transmissivities of 2,500 and 6 ,000 sq ft/day and storage coefficients of 0.0003 and 0.0007, respectively. The Cockfield aquifer presently provides small to moderate quantities of water for several public and industrial water supplies and small quantities to numerous domestic and farm wells. Withdrawals for public and industrial supplies in 1983 averaged about 3.3 million gal/day. (USGS)

Tennessee↗
USGS1990

Altitude of potentiometric surface, fall 1985, and historic water-level changes in the Fort Pillow aquifer in western Tennessee

Recharge to the Fort Pillow aquifer of Tertiary age is from precipitation on the outcrop, which forms a narrow belt across western Tennessee, and by downward infiltration of water from the overlying fluvial deposits of Tertiary(?) and Quaternary age and alluvium of Quaternary age or, where the upper confining unit is absent, from the overlying Memphis aquifer of Tertiary age. The potentiometric surface in the Fort Pillow aquifer slopes gently westward from the outcrop-recharge area, and the water moves slowly in that direction. A depression in the potentiometric surface in the Memphis area is the result of past pumping at Memphis Light, Gas and Water Division well fields (1924-74), past and present pumping at an industrial well field at Memphis, and the municipal well field at West Memphis, Ark. Withdrawals from the Fort Pillow aquifer in western Tennessee in 1985 averaged about 12 million gallons per day. Water-level data from four observation wells, all in areas affected by pumping, indicate that water levels have declined at average rates ranging from about 0.4 to 0.9footperyearduring the past 40years (1945-85). The greatest rate of decline was as much as 4.0 feet per year between 1945 and 1954 in an observation well in a well field of Memphis Light, Gas and Water Division at Memphis. In 1971, Memphis Light, Gas and Water Division ceased pumping from the Fort Pillow aquifer at this well field, and between 1971 and 1976, water levels rose about 28 feet in this well. Water levels in the Fort Pillow aquifer in large areas of western Tennessee away from the effects of pumping have fluctuated only in response to long-term variations in precipitation on the outcrop-recharge belt. Long-term changes in water levels in these areas have been small.

Tennessee↗
USGS1993

Geohydrology of the Mesilla ground-water basin, Dona Ana County, New Mexico, and El Paso County, Texas

The aquifer system of the Mesilla ground-water basin is the Quaternary flood-plain alluvium and the Quaternary and Tertiary Santa Fe Group. The hydraulic gradient in the shallow flood-plain alluvium within the Mesilla Valley is generally between 4 and 6 feet per mile. The hydraulic gradient in the Santa Fe Group ranges from 100 feet per mile in the northwestern part of the study area to less than 2 feet per mile in the southwestern part of the study area. Ground-water levels in nearby observation wells correspond to increases in river stage and indicate significant recharge to the aquifer at the Rio Grande. Water in storage within the Rio Grande flood-plain alluvium/Santa Fe Group aquifer system occurs under unconfined and semi- confined conditions. Horizontal permeability usually exceeds vertical permeability by several orders of magnitude. The thickness and extent of finer grained, less permeable material increase with depth and horizontally toward the southern end of the basin. Seasonal trends in the shallow water table generally correspond to recharge during the irrigation season. Freshwater zones are overlain by zones of slightly saline to saline water in the Mesilla Valley. Geohydrologic data indicate that the thickness of the freshwater zone is significantly less than previously estimated in the vicinity of the proposed West Mesa well field. Lithologic data, borehole-geophysical logs, water-quality data, and potentiometric contours of ground-water in the upper Santa Fe Group indicate a hydraulic connection between the Mesilla Valley and West Mesa.

New Mexico, Texas↗
USGS1993

Reconnaissance investigation of the geology and hydrogeology of Lackland Air Force Base, San Antonio, Texas

An investigation at Lackland Air Force Base and Lackland Air Force Base Training Annex (Medina Base) was conducted from May to September 1988 to delineate the subsurface geology, to describe the hydrogeology within the study area, and to determine possible migration pathways for contaminants. Data from this investigation supplement data collected in conjunction with other Air Training Command studies conducted under the Installation Restoration Program. The geologic formations in the vicinity of Lackland Air Force Base and Medina Base consist of sedimentary rocks of Cretaceous, Tertiary, and Quaternary age. The lithology of these formations consists primarily of limestone and marl, with lesser amounts of gravel, sand, silt, shale, and clay. The formations that comprise the geologic setting at Lackland Air Force Base and Medina Base include the Navarro Group of Late Cretaceous age, the Midway Group and Uvalde Gravel of Tertiary age, and the Leona Formation and fluviatile terrace deposits of Quaternary age. The age of the faulting within the study area has not been determined accurately, but the faulting might have occurred during intervals from Early Cretaceous to Holocene time. During these tectonic episodes, uplift of the Edwards Plateau might have occurred. This uplift could have enhanced erosion of the Cretaceous age Edwards Group, which is north of the study area, causing deposition of alluvial deposits south of this tectonic activity. The Leona Formation is composed of limestone gravel deposits forming terraces in the valleys of present streams. In general, these terraces are topographically lower than those formed by the Uvalde Gravel. In contrast, the fluviatile terrace deposits are above flood level along entrenched streams such as Leon and Medio Creeks. The Leona Formation is generally above the level of these fluviatile terrace deposits. A review of the hydrogeologic literature indicated that the Navarro and Midway Groups do not yield water to wells in Bexar County. However, recent studies by the U.S. Geological Survey at Kelly Air Force Base indicate that the uppermost beds of the Navarro Group can be saturated but yield little or no water to wells. Each stream terrace deposit of the Leona Formation and the fluviatile terrace deposits are separate water-bearing units. At Lackland Air Force Base, shallow ground water is present in the Leona Formation and the flow probably is toward Leon Creek. At Medina Base, the fluviatile terrace deposits are present along both banks of Medio Creek and probably are separate water-bearing units. Furthermore, ground-water flow in each of these units probably is toward Medio Creek. The Uvalde Gravel, present only at and west of Medina Base, is not a source of shallow ground water. However, during periods of precipitation, the formation can readily absorb precipitation and surface runoff. Water drains quickly through the formation because of its topographically high position and substantial hydraulic conductivity. Major pathways of potential contaminant migration off the bases include the local streams of Medio and Leon Creeks, and to a lesser extent, the shallow ground water beneath the bases. Although the Uvalde Gravel is not a source of shallow ground water at Medina Base, it drains water quickly, and wastes that might be buried in the gravel could be a potential source of contamination during brief ground-water recharge periods resulting from major precipitation.

Texas↗
USGS1995

Hydrology and relation of selected water-quality constituents to selected physical factors in Dakota County, Minnesota, 1990-91

Selected water-quality constituents were determined in water from 5 surface-water sites and 29 wells in Dakota County, Minnesota, to search for possible relations to selected physical factors, including waste-water discharge, agricultural land, Quaternary deposits, bedrock, soil-leaching potential, and water-table depth. All surface-water samples were from the Vermillion River Basin, whose hydrologic setting was studied to determine its relation to the ground-water flow in the surrounding surficial sand aquifer. Each site was sampled from 1 to 12 times during 1990- 91. A total of 198 samples were collected; selected samples were analyzed for major inorganic ions, nutrients, and triazine content. Physical factors within the area of land assumed to be contributing water to each sampling site were determined from existing mapped or digitized sources. Nitrate concentrations in ground water were related to agricultural land and soil-leaching potential. Nitrate concentrations were large (median 13.2 milligrams per liter as nitrogen) where the percentage of agricultural land in the contributing area was large (equal to or greater than 75 percent) and where the soils had a large soil-leaching potential. Nitrate concentrations were small (median 3.2 milligrams per liter as nitrogen) where the soils had a small soil-leaching potential, despite a large percentage of agricultural land. The statistical relation was not particularly strong, however: the null hypothesis that sites with different soil-leaching potentials had the same nitrate concentrations in ground water was rejected by the Kruskal-Wallis test at only the probability P = 0.15 level. Water-table depth was not an important factor in the relation between nitrate concentrations in ground water and agricultural land. Discharge from a waste-water treatment plant provided most of the downstream loading of nitrate into the Vermillion River mainstem. Triazines were found in small concentrations (less than 2 micrograms per liter) in the Vermillion River and its tributaries. No relation was apparent between selected water-quality constituents and either Quaternary deposits or bedrock.

Minnesota↗
USGS1995

Geohydrologic conditions and land use in the Gallatin Valley, southwestern Montana, 1992-93

The Gallatin Valley is part of an intermontane basin in southwestern Montana with an area of about 540 mi2. The valley is drained by the Gallatin River and its tributaries. After formation of the Three Forks structural basin, the Gallatin Valley was filled with as much as 6,000 feet of Tertiary and Quaternary sediments. Depth to water in the study area generally ranges from about 3 feet to about 460 feet below land surface. The median specific capacity of 26 wells completed in alluvium was 4.6 gallons per minute per foot. The median specific capacity of 21 wells completed in Quaternary and Tertiary alluvial-fan deposits in the southern and eastern part of the area was 1.6 gallons per minute per foot. The median specific capacity of 16 wells completed in Tertiary sediments was 0.78 gallon per minute per foot. Water from 38 wells sampled for water-quality analyses generally was a calcium bicarbonate type containing dissolved-solids concentrations ranging from 113 to 551 milligrams per liter. Radon-222 concentrations in water from 16 samples wells ranged from 170 to 1,565 picocuries per liter. Water samples collected from 6 wells were analyzed for a total of 54 pesticides and pesticide- degradation products. No pesticides or related analytes were detected in any of the samples. Agriculture is the primary land use in the Gallatin Valley; however, population growth has resulted in the establishment of numerous rural subdivisions. Water-level measurements made during this study coupled with long-term water-level trends do not indicate any significant water-level changes resulting from increased ground-water withdrawals. The occurrence of larger nitrate concentrations (maximum of 4.5 milligrams per liter) in ground water in more densely developed areas indicates a possible influence of subdivision development on ground-water quality.

Montana↗
USGS1996

Water resources of the Wind River Indian Reservation, Wyoming

Existing data were used in conjunction with onsite measurements to evaluate the water resources on the Wind River Indian Reservation, Wyoming. The reservation is located mainly in the Wind River drainage basin. Ground water is used for public- supply, domestic, agricultural, and industrial purposes, and potentially for irrigation. Deposits of Quaternary age provide water for domestic and public-supply uses. Median well yields from different types of Quaternary deposits ranged from 6 to 20 gallons per minute. The Wind River Formation of Tertiary age is a major source of water for domestic and public-supply uses; well yields ranged from 0.1 to 350 gallons per minute. For the Tensleep Sandstone and Madison Limestone of Paleozoic age, wells might yield as much as 1,000 gallons per minute. The dissolved-solids concentration of water from the Little Wind River and Popo Agie River flood-plain alluvium near mountains was generally less than 400 mg/L (milligrams per liter), but with increasing distance from mountains, the range was about 600 to about 750 mg/L. Dissolved-solids concentrations of water in the Wind River Formation ranged from 211 to 5,110 mg/L. Streams provide most water used for irrigation. Discharge records from streamflow-gaging stations indicate flow characteristics of streams on the reservation are extremely variable. Average annual runoff was 122 to 1,150 acre-feet per square mile on perennial streams with gaging stations. Near the mountains, most perennial streams had dissolved-solids concentrations less than 200 mg/L, and with increasing distance from the mountains, concentrations were about 400 to 600 mg/L.

Water-Resources Investigations Report↗