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At least 991 records · Page 55Linked to original sources
USGS2003

Natural background concentrations of nutrients in streams and rivers of the conterminous United States

Determining natural background concentrations of nutrients in watersheds in the developed world has been hampered by a lack of pristine sampling sites covering a range of climatic conditions and basin sizes. Using data from 63 minimally impacted U.S. Geological Survey reference basins, we developed empirical models of the background yield of total nitrogen (TN) and total phosphorus (TP) from small watersheds as functions of annual runoff, basin size, atmospheric nitrogen deposition rate, and region-specific factors. We applied previously estimated in-stream loss rates to yields from the small watershed models to obtain estimates of background TN and TP yield and concentration throughout the stream/river network in 14 ecoregions of the conterminous United States. Background TN concentration varies from less than 0.02 mg L-1 in the xeric west to more than 0.5 mg L-1 along the southeastern coastal plain. Background TP concentration varies from less than 0.006 mg L-1 in the xeric west to more than 0.08 mg L-1 in the great plains. TN concentrations in U.S. streams and rivers currently exceed natural background levels by a much larger factor (6.4) than do TP concentrations (2.0). Because of local variation in runoff and other factors, the range of background nutrient concentrations is very large within some nutrient ecoregions. It is likely that background concentrations in some streams in these regions exceed proposed nutrient criteria.

Environmental Science & Technology↗
USGS1997

Water resources of Bannock Creek basin, southeastern Idaho

The potential for development of water resources in the Bannock Creek Basin is limited by water supply. Bannock Creek Basin covers 475 square miles in southeastern Idaho. Shoshone-Bannock tribal lands on the Fort Hall Indian Reservation occupy the northern part of the basin; the remainder of the basin is privately owned. Only a small amount of information on the hydrologic and water-quality characteristics of Bannock Creek Basin is available, and two previous estimates of water yield from the basin ranged widely from 45,000 to 132,500 acre-feet per year. The Shoshone-Bannock Tribes need an accurate determination of water yield and baseline water-quality characteristics to plan and implement a sustainable level of water use in the basin. Geologic setting, quantities of precipitation, evapotranspiration, surface-water runoff, recharge, and ground-water underflow were used to determine water yield in the basin. Water yield is the annual amount of surface and ground water available in excess of evapotranspiration by crops and native vegetation. Water yield from Bannock Creek Basin was affected by completion of irrigation projects in 1964. Average 1965-89 water yield from five subbasins in Bannock Creek Basin determined from water budgets was 60,600 acre-feet per year. Water yield from the Fort Hall Indian Reservation part of Bannock Creek Basin was estimated to be 37,700 acre-feet per year. Water from wells, springs, and streams is a calcium bicarbonate type. Concentrations of dissolved nitrite plus nitrate as nitrogen and fluoride were less than Maximum Contaminant Levels for public drinking-water supplies established by the U.S. Environmental Protection Agency. Large concentrations of chloride and nitrogen in water from several wells, springs, and streams likely are due to waste from septic tanks or stock animals. Estimated suspended-sediment load near the mouth of Bannock Creek was 13,300 tons from December 1988 through July 1989. Suspended-sediment discharge was greatest during periods of high streamflow.

Idaho↗
USGS2006

Geohydrology of the lower Apalachicola-Chattahoochee-Flint River basin, southwestern Georgia, northwestern Florida, and southeastern Alabama

The lower Apalachicola-Chattahoochee-Flint (ACF) River Basin contains about 4,600 square miles of karstic and fluvial plains and nearly 100,000 cubic miles of predominantly karst limestone connected hydraulically to the principal rivers and lakes in the Coastal Plain of southwestern Georgia, northwestern Florida, and southwestern Alabama. Sediments of late-middle Eocene to Holocene in hydraulic connection with lakes, streams, and land surface comprise the surficial aquifer system, upper semiconfining unit, Upper Floridan aquifer, and lower semiconfining unit and contribute to the exchange of ground water and surface water in the stream-lake-aquifer flow system. Karst processes, hydraulic properties, and stratigraphic relations limit ground-water and surface-water interaction to the following hydrologic units of the stream-lake-aquifer flow system: the surficial aquifer system, upper semiconfining unit, Upper Floridan aquifer, and lower confining unit. Geologic units corresponding to these hydrologic units are, in ascending order: Lisbon Formation; Clinchfield Sand; Ocala, Marianna, Suwannee, and Tampa Limestones; Hawthorn Group; undifferentiated overburden (residuum); and terrace and undifferentiated (surficial) deposits. Similarities in hydraulic properties and direct or indirect interaction with surface water allow grouping sediments within these geologic units into the aforementioned hydrologic units, which transcend time-stratigraphic classifications and define the geohydrologic framework for the lower ACF River Basin. The low water-transmitting properties of the lower confining unit, principally the Lisbon Formation, allow it to act as a nearly impermeable base to the stream-lake-aquifer flow system. Hydraulic connection of the surficial aquifer system with surface water and the Upper Floridan aquifer is direct where sandy deposits overlie the limestone, or indirect where fluvial deposits overlie clayey limestone residuum. The water level in perched zones within the surficial aquifer system fluctuates independently of water-level changes in the underlying aquifer, adjacent streams, or lakes. Where the surficial aquifer system is connected with surface water and the Upper Floridan aquifer, water-table fluctuations parallel those in adjacent streams or the underlying aquifer. More...

Alabama, Florida, Georgia↗
USGS1988

Acoustic stratigraphy and hydrothermal activity within Epi Submarine Caldera, Vanuatu, New Hebrides Arc

Geological and geophysical surveys of active submarine volcanoes offshore and southeast of Epi Island, Vanuatu, New Hebrides Arc, have delineated details of the structure and acoustic stratigraphy of three volcanic cones. These submarine cones, named Epia, Epib, and Epic, are aligned east-west and spaced 3.5 km apart on the rim of a submerged caldera. At least three acoustic sequences, of presumed Quaternary age, can be identified on single-channel seismic-reflection profiles. Rocks dredged from these cones include basalt, dacite, and cognate gabbroic inclusions with magmatic affinities similar to those of the Karua (an active submarine volcano off the southeastern tip of Epi) lavas. ?? 1988 Springer-Verlag New York Inc.

Geo-Marine Letters↗
USGS1990

Geology and geochemistry of epithermal precious metal vein systems in the intra-oceanic arcs of Palau and Yap, western Pacific

The Palau and Yap arcs are part of an intra-oceanic island-arc-trench system which separates the Pacific and Philippine plates in the western Pacific Ocean. The 350-km-long Palau arc consists of over 200 islands while the 400-km-long Yap arc located to the north has only four major islands exposed. Four of the largest islands in Palau are composed primarily of early Eocene to mid-Miocene volcanic rocks and the four islands comprising Yap contain only Miocene volcanic rocks. Basalt and basaltic andesites of the Babelthuap Formation are the oldest volcanic rocks in Palau and are characterized by high MgO, Ni and Cr and low TiO 2 and have a boninitic affinity. They form the central and southeastern parts of Babelthuap Island. Oligocene arc tholeiite flows having an age of 34–35.5 Ma comprise most of the three smaller volcanic islands in Palau and the western part of Babelthuap. The youngest volcanic rocks are dacitic intrusions having an age of 22.7–23.2 Ma. The Yap arc is unusual in that metamorphic rocks up to amphibolite grade form most of the islands. These are underlain by a melange composed of igneous and volcanic clasts as well as clasts from a dismembered copper-gold skarn deposit. Miocene volcanic rocks consisting of flows and volcaniclastic deposits overlie the melange and metamorphic complex.

Journal of Geochemical Exploration↗
USGS1975

Water availability of Choctaw County, Alabama

Large quantities of ground water and surface water are available in Choctaw County. Major sources of ground water are the Nanafalia Formation, Tuscahoma Sand, Hatchetigbee Formation, and Gosport Sand and Lisbon Formation. The Nanafalia Formation is the most productive source of ground water, and individual wells will yield as much as 1.0 mgd (million gallons per day). The depths to aquifers and the quality of ground water in the south half of the county are governed in part by geologic structures. The average flow of the Tombigbee River at the southeast corner of the county is 16,500 mgd and the 7-day Q2 exceeds 1,000 mgd. Kinterbish, Tuckabum, and Okatuppa Creeks have average flows that range from 115 to 265 mgd at their confluences with the Tombigbee River and 7-day Q2's that exceed 10 mgd in their downstream reaches. Average runoff originating in the county is about 786 mgd or 0.8 mgd per square mile. Water in aquifers tapped by wells generally contains less than 500 mg/1 (milligrams per liter) dissolved solids and is soft to moderately hard. In southeastern parts of the county, in the vicinity of the Hatchetigbee anticline, wells have been abandoned because of the poor quality of water. Water in streams, with the exception of that in Okatuppa Creek and some of its tributaries near Gilbertown and Barrytown, is generally soft and contains less than 140 mg/1 dissolved solids. The quality of water in Okatuppa Creek and some of its tributaries reflects contamination by oil-field brines. Biweekly samples collected from Okatuppa Creek from September 1965 to May 1967 show an average chloride content of 312 mg/1 and specific conductances indicate an average dissolved solids content of 630 mg/ 1.

Alabama↗
USGS1985

Chemical and biological quality of selected lakes in Ohio, 1978 and 1979

Twenty-eight Ohio lakes were sampled by the U.S. Geological Survey and the Ohio Environmental Protection Agency for water-quality characteristics during the spring and summer of 1978 and 1979. This report is the third in a series covering a lake-sampling program that began in 1975. Data include water-column profiles of temperature, dissolved oxygen, pH, and specific conductance. Chemical, physical, and biological properties were measured at specific points in the water column, and selected physical and chemical properties also were measured in the principal inflows. The lakes were predominatly hard (120 180 milligrams per liter) to very hard water, although several soft-water lakes were found in southeastern Ohio. Calcium, bicarbonate, and sulfate were the principal dissolved constituents. Specific conductance ranged from 103 micromhos per centimeter (at 25 degrees Celsius) at Tycoon Lake, 1978, to 2,550 micromhos per centimeter at West Fork Mill Creek Lake, 1978. Thirteen lakes had trace-element concentrations that were above the limits for exceptional warm-water habitat recammended by the Ohio Environmental Protection Agency. Seasonal thermal gradients developed in most lakes deeper than 17 feet. Oxygen concentrations were zero or near zero during the summer sampling of the bottom water of all lakes having definite thermal gradients. Most anaerobic zones contained hydrogen sulfide and high concentrations of ammonia. All lakes were evaluated and classified by Carlson's trophic state index. Most of the lakes were classified as eutrophic. Blue-green algae (CyanophytaJ) dominated the summer algal communities. Fecal colifrom counts were within Ohio standards, although high (more than 1,000 colonies per 100 milliliters) fecal colifrom and fecal streptococcus counts were observed in West Fork Mill Creek Lake after significant runoff.

Open-File Report↗
USGS2007

Origin of narrow terranes and adjacent major terranes occurring along the Denali fault in the Eastern and Central Alaska Range, Alaska

Several narrow terranes occur along the Denali fault in the Eastern and Central Alaska Range in Southern Alaska. These terranes are the Aurora Peak, Cottonwood Creek, Maclaren, Pingston, and Windy terranes, and a terrane of ultramafic and associated rocks. Exterior to the narrow terranes to the south is the major Wrangellia island arc composite terrane, and to the north is the major Yukon-Tanana metamorphosed continental margin terrane. Overlying mainly the northern margin of the Wrangellia composite terrane are the Kahiltna overlap assemblage to the west, and the Gravina-Nutzotin-Gambier volcanic-plutonic-sedimentary belt to the east and southeast. The various narrow terranes are interpreted as the result of translation of fragments of larger terranes during two major tectonic events: (1) Late Jurassic to mid-Cretaceous accretion of the Wrangellia island arc composite terrane (or superterrane composed of the Wrangellia, Peninsular, and Alexander terranes) and associated subduction zone complexes; and (2) starting in about the Late Cretaceous, dextral transport of the Wrangellia composite terrane along the Denali fault. These two major tectonic events caused: (1) entrapment of a lens of oceanic lithosphere along the suture belt between the Wrangellia composite terrane and the North American Craton Margin and outboard accreted terranes to form the ultramafic and mafic part of the terrane of ultra-mafic and associated rocks, (2) subsequent dextral translation along the Denali fault of the terrane of ultramafic and associated rocks, (3) dextral translation along the Denali fault of the Aurora Peak, Cottonwood Creek, and Maclaren and continental margin arc terranes from part of the Coast plutonic-metamorphic complex (Coast-North Cascade plutonic belt) in the southwest Yukon Territory or Southeastern Alaska, (4) dextral translation along the Denali fault of the Pingston passive continental margin from a locus along the North American Continental Margin, and (5) formation and dextral transport along the Denali fault of the mélange of the Windy terrane from fragments of the Gravina-Nutzotin-Gambier volcanic-plutonic-sedimentary belt and from the North American Continental Margin.

Special Paper of the Geological Society of America↗
USGS2006

Deep-water antipatharians: Proxies of environmental change

Deep-water (307-697 m) antipatharian (black coral) specimens were collected from the southeastern continental slope of the United States and the north-central Gulf of Mexico. The sclerochronology of the specimens indicates that skeletal growth takes place by formation of concentric coeval layers. We used 210Pb to estimate radial growth rate of two specimens, and to establish that they were several centuries old. Bands were delaminated in KOH and analyzed for carbon and nitrogen stable isotopes. Carbon values ranged from -16.4??? to -15.7???; oldest specimen displayed the largest range in values. Nitrogen values ranged from 7.7??? to 8.6???. Two specimens from the same location and depth had similar 15N signatures, indicating good reproducibility between specimens. ?? 2006 Geological Society of America.

Geology↗
USGS2023

Roles of regional structures and country-rock facies in defining mineral belts in central Idaho mineral province with detail for Yellow Pine and Thunder Mountain mining districts

The central Idaho metallogenic province hosts numerous mineral deposit types. These include Late Cretaceous precious-polymetallic vein deposits, amagmatic Paleocene–Eocene breccia-hosted gold-tungsten-antimony deposits, and Eocene mercury deposits in metasedimentary roof pendants and in Late Cretaceous granitoids. Hot-springs gold deposits in Eocene volcanic rocks are also included in the central Idaho province. New sensitive high mass-resolution ion microprobe (SHRIMP) uranium-lead (U-Pb) ages for igneous rocks and for detrital zircon analyses of metasedimentary rocks along with geologic mapping clarify the geologic framework of the mineral deposits. This framework includes (1) structural controls for regional distribution of mining districts, (2) progressive structural development of individual districts, (3) regional sedimentary facies and their control of metals associations resulting in regional belts, and (4) influences of the several regional magmatic events. In central Idaho, 15 mining districts form two clusters that are grouped about a 200-kilometer (km) long system of normal faults. The northwestern cluster is in the regional hanging wall west of large, west-side-down faults, and the mineral deposits are located along smaller faults and fractures that cut the regional hanging wall. The southeastern cluster is in the regional hanging wall east of a linked large east-side-down fault and along and controlled by related hanging wall faults. At the southern extent of the regional fault system, the Yellow Pine-Thunder Mountain districts span a nearly 24-km-wide, east-tilted crustal block of normal-fault dominoes, exposing original crustal depths from 5 to 10 km deep on the west in the Late Cretaceous to shallow-surface depths on the east in the Eocene. Ore deposition in the northwestern district cluster was primarily Late Cretaceous and related to Idaho batholith plutons with only a single deposit related to a small Eocene intrusion; in the southeastern cluster, most deposits were initiated in the Late Cretaceous but with varying manifestations of overprinted Eocene mineralization activity. In the Yellow Pine-Thunder Mountain districts at the southern extent of the southern cluster, several mineralizing pulses occurred during hanging-wall collapse, such that (1) early deposits were multiply overprinted and (2) deposit depths, ages, and structural characteristics change progressively eastward. Originally deep-seated western Yellow Pine district deposits are Late Cretaceous viscoplastic mesothermal veins overprinted by Paleocene and Eocene breccia-hosted epithermal deposits. Central Yellow Pine district deposits contain early deeper vein systems but are primarily Paleocene and Eocene breccia-hosted epithermal deposits in Late Cretaceous plutonic rocks and Proterozoic–Paleozoic roof pendant rocks. Eastern district deposits are Eocene hot-springs-related deposits in the roof pendant. Thunder Mountain deposits farthest east are near-surface hot-springs deposits in Eocene volcanic and volcaniclastic rocks that overlie buried Cretaceous igneous and older roof pendant rocks. The mining district clusters are sited across several northwest-striking paleostratigraphic belts that are exposed in roof pendants and are offset by the regional normal fault system. A northeastern belt is Mesoproterozoic strata associated with gold-silver-copper±cobalt deposits. A central belt of Neoproterozoic rocks is not associated with mineral deposits in the central Idaho mineral province. A southwestern belt composed of probable Paleozoic deep-water miogeoclinal slope rocks and late Paleozoic epicratonic basinal rocks is thin and narrowly exposed but associated with gold-silver-antimony-tungsten±mercury deposits. These metasedimentary rocks (and their metal associations) are parts of regional mineral belts in which metal endowments are related to particular sedimentary facies belts and their Cretaceous thrust-fault juxtaposition and where these features have proximity to Late Cretaceous or Eocene igneous rocks. Offset and preservation or erosional stripping of these facies belts, thrust plates, igneous settings, and the associated regional mineral belts were controlled by the sense and magnitude of displacements across the regional normal-fault system.

Idaho↗
USGS2008

Comparisons of Simulated Hydrodynamics and Water Quality for Projected Demands in 2046, Pueblo Reservoir, Southeastern Colorado

Pueblo Reservoir is one of southeastern Colorado's most valuable water resources. The reservoir provides irrigation, municipal, and industrial water to various entities throughout the region. The reservoir also provides flood control, recreational activities, sport fishing, and wildlife enhancement to the region. The Bureau of Reclamation is working to meet its goal to issue a Final Environmental Impact Statement (EIS) on the Southern Delivery System project (SDS). SDS is a regional water-delivery project that has been proposed to provide a safe, reliable, and sustainable water supply through the foreseeable future (2046) for Colorado Springs, Fountain, Security, and Pueblo West. Discussions with the Bureau of Reclamation and the U.S. Geological Survey led to a cooperative agreement to simulate the hydrodynamics and water quality of Pueblo Reservoir. This work has been completed and described in a previously published report, U.S. Geological Survey Scientific Investigations Report 2008-5056. Additionally, there was a need to make comparisons of simulated hydrodynamics and water quality for projected demands associated with the various EIS alternatives and plans by Pueblo West to discharge treated water into the reservoir. Plans by Pueblo West are fully independent of the SDS project. This report compares simulated hydrodynamics and water quality for projected demands in Pueblo Reservoir resulting from changes in inflow and water quality entering the reservoir, and from changes to withdrawals from the reservoir as projected for the year 2046. Four of the seven EIS alternatives were selected for scenario simulations. The four U.S. Geological Survey simulation scenarios were the No Action scenario (EIS Alternative 1), the Downstream Diversion scenario (EIS Alternative 2), the Upstream Return-Flow scenario (EIS Alternative 4), and the Upstream Diversion scenario (EIS Alternative 7). Additionally, the results of an Existing Conditions scenario (water years 2000 through 2002) were compared to the No Action scenario (projected demands in 2046) to assess changes in water quality over time. All scenario modeling used an external nutrient-decay model to simulate degradation and assimilation of nutrients along the riverine reach upstream from Pueblo Reservoir. Reservoir modeling was conducted using the U.S. Army Corps of Engineers CE-QUAL-W2 two-dimensional water-quality model. Lake hydrodynamics, water temperature, dissolved oxygen, dissolved solids, dissolved ammonia, dissolved nitrate, total phosphorus, algal biomass, and total iron were simulated. Two reservoir site locations were selected for comparison. Results of simulations at site 3B were characteristic of a riverine environment in the reservoir while results at site 7B (near the dam) were characteristic of the main body of the reservoir. Simulation results for the epilimnion and hypolimnion at these two sites also were evaluated and compared. The simulation results in the hypolimnion at site 7B were indicative of the water quality leaving the reservoir. Comparisons of the different scenario results were conducted to assess if substantial differences were observed between selected scenarios. Each of the scenarios was simulated for three contiguous years representing a wet, average, and dry annual hydrologic cycle (water years 2000 through 2002). Additionally, each selected simulation scenario was evaluated for differences in direct- and cumulative-effects on a particular scenario. Direct effects are intended to isolate the future effects of the scenarios. Cumulative effects are intended to evaluate the effects of the scenarios in conjunction with all reasonably foreseeable future activities in the study area. Comparisons between the direct- and cumulative-effects analyses indicated that there were not large differences in the results between most of the simulation scenarios and, as such, the focus of this report was on results for the direct-effects analysis. Addi

Scientific Investigations Report↗
USGS2024

Conceptual hydrogeologic framework and groundwater budget near the southeastern part of Puget Sound, Washington

More than 1 million people live within the active model area (AMA) in the southeastern part of the lowlands surrounding Puget Sound, or Puget Lowland, Washington, and groundwater is the source for approximately one-half of their public, domestic, and irrigation water demands. The 887-square-mile AMA, located in King and Pierce Counties, represents the area of analysis for the conceptual hydrogeologic framework and numerical groundwater-flow models within the study area and includes the Puyallup River and Chambers-Clover Creek watersheds. To assess the potential hydrologic and anthropogenic impacts to groundwater and the connected surface-water resources, conceptual and numerical groundwater-flow models of groundwater flow were developed by the U.S. Geological Survey Washington Water Science Center in close cooperation with 18 water-resource agencies and stakeholders. This report presents information used to characterize the groundwater-flow system and the development of a numerical model in the AMA. Included are descriptions of the geology and conceptual hydrogeologic framework, groundwater levels and flow directions, groundwater recharge and discharge, numerical groundwater-flow model construction and results, and model limitations. The study area encompasses the western part of Pierce County and the southwestern part of King County, Washington. The study area extends south to the Nisqually River, southwest to Tanwax Creek, northeast to the Green River, and north through the valley near Auburn and adjacent uplands. It is bounded on the east by foothills of the Cascade Range, and on the northwest by Puget Sound.

Washington↗
USGS1999

Hydrogeology of the upper Floridan Aquifer in the vicinity of the Marine Corps Logistics Base near Albany, Georgia

In 1995, the U.S. Navy requested that the U.S. Geological Survey conduct an investigation to describe the hydrogeology of the Upper Floridan aquifer in the vicinity of the Marine Corps Logistics Base, southeast and adjacent to Albany, Georgia. The study area encompasses about 90 square miles in the Dougherty Plain District of the Coastal Plain physiographic province, in Dougherty and Worth Counties-the Marine Corps Logistics Base encompasses about 3,600 acres in the central part of the study area. The Upper Floridan aquifer is the shallowest, most widely used source of drinking water for domestic use in the Albany area. The hydrogeologic framework of this aquifer was delineated by description of the geologic and hydrogeologic units that compose the aquifer; evaluation of the lithologic and hydrologic heterogeneity of the aquifer; comparison of the geologic and hydrogeologic setting beneath the base with those of the surrounding area; and determination of ground-water-flow directions, and vertical hydraulic conductivities and gradients in the aquifer. The Upper Floridan aquifer is composed of the Suwannee Limestone and Ocala Limestone and is divided into an upper and lower water-bearing zone. The aquifer is confined below by the Lisbon Formation and is semi-confined above by a low-permeability clay layer in the undifferentiated overburden. The thickness of the aquifer ranges from about 165 feet in the northeastern part of the study area, to about 325 feet in the southeastern part of the study area. Based on slug tests conducted by a U.S. Navy contractor, the upper water-bearing zone has low horizontal hydraulic conductivity (0.0224 to 2.07 feet per day) and a low vertical hydraulic conductivity (0.0000227 to 0.510 feet per day); the lower water-bearing zone has a horizontal hydraulic conductivity that ranges from 0.0134 to 2.95 feet per day. Water-level hydrographs of continuously monitored wells on the Marine Corps Logistics Base show excellent correlation between ground-water level and stage of the Flint River. Ground-water-flow direction in the southwestern part of the base generally is southeast to northwest; whereas, in the northeastern part of the base, flow directions generally are east to west, as well as from west to east, thus creating a ground-water low. Ground-water flow in the larger study area generally is east to west towards the Flint River, with a major ground-water-flow path existing from the Pelham Escarpment to the Flint River and a seasonal cone of depression the size of which is dependent upon the magnitude of irrigation pumping during the summer months. Calculated vertical hydraulic gradients (based upon data from 11 well-cluster sites on the Marine Corps Logistics Base) range from 0.0016 to 0.1770 foot per foot, and generally are highest in the central and eastern parts of the base. The vertical gradient is downward at all well-cluster sites.

Georgia↗
USGS1993

Historical saturated thickness of the Edwards-Trinity aquifer system and selected contiguous hydraulically connected units, west-central Texas

The Edwards-Trinity Regional Aquifer-System Analysis (RASA) is one of 25 completed or ongoing studies conducted by the U.S. Geological Survey on regional aquifer systems that individually provide essential quantities of ground water to large parts of the country. Underlying about 42,000 mi 2 of west-central Texas, the Edwards-Trinity aquifer system extends approximately from Atascosa County in the southeast to Culberson County in the northwest and from the Rio Grande in the southwest to the Colorado River in the northeast (sheet 2). The Edwards-Trinity aquifer system spans four geographic subareas: Trans-Pecos, Edwards Plateau, Hill Country, and Balcones fault zone (fig. 1). The names of all aquifers in the study area were adopted for RASA purposes directly from nomenclature mandated by the Texas Water Plan (Texas Water Development Board, 1990). The Cretaceous rocks that compose the Edwards-Trinity aquifer system are primarily limestone and dolomite rock, with lesser quantities of terrigenous sand. Although the lithology varies locally and the rocks are not everywhere permeable in all directions, they combine to form a single regional aquifer system. The aquifer system comprises three aquifers and two confining units (figs. 2 and 3). The water-yielding units are the Edwards aquifer of the Balcones fault zone, the Trinity aquifer of the Balcones fault zone and Hill Country, and the Edwards-Trinity aquifer of the Edwards Plateau and Trans-Pecos. The confining units are the Hammett confining unit, which confines basal parts of the Trinity aquifer in the Hill Country and the Edwards-Trinity aquifer in the eastern part of the Edwards Plateau, and the Navarro-Del Rio confining unit, which confines the Edwards and Trinity aquifers along the southeastern margin of the Balcones fault zone. Parts of the aquifer system not overlain by one of these confining units are unconfined, or nearly so. The purposes of this report are to illustrate the historical distribution of saturated thickness (hereafter referred to as the saturated thickness) in the Edwards-Trinity aquifer system, summarize the reasons for the variation in the saturated thickness, and relate the regional effects of this variation to the distribution of transmissivity. The saturated thickness map (sheet 2) was determined for most of the area by subtracting the altitude of the base of the aquifer system (Barker and Ardis, 1992) from the altitude of the historical potentiometric surface (Bush and others, 1993). Where the Edwards and Trinity aquifers are confined in the Balcones fault zone, the saturated thickness is defined by the thickness of the aquifer system, which was determined by subtracting the altitude of the base of the aquifer system from the altitude of the base of the Navarro-Del Rio confining unit (G.E. Groschen and W.G. Stein, U.S. Geological Survey, written commun, 1990).

Texas↗
USGS1980

Hydrogeologic data for the Mississippi Embayment of southeastern Missouri

The Mississippi embayment of southeastern Missouri is a 4 ,000-square-mile agricultural area that is presently (1979) undergoing rapid development for irrigation. In July 1974, a project was initiated to evaluate the water resources of the area, determine the extent of irrigation, and to assess the future potential for irrigation supplies. This report provides well drillers, well owners, water users, and potential irrigators with the basic hydrologic data collected during the project. The 10 tables and eight figures show the location of irrigation wells, water-level networks to monitor ground-water and surface-water conditions, a pumpage network to estimate amounts of water used for irrigation, geologic data, municipal-well data, and water-quality data for selected wells. (USGS)

Open-File Report↗
USGS2013

Groundwater withdrawals 1976, 1990, and 2000--10 and land-surface-elevation changes 2000--10 in Harris, Galveston, Fort Bend, Montgomery, and Brazoria Counties, Texas

The study area comprising Harris County and parts of Galveston, Fort Bend, Montgomery, and Brazoria Counties in southeastern Texas forms part of one of the largest areas of land-surface-elevation change in the United States. Land-surface-elevation change in the study area primarily is caused by the withdrawal of groundwater. Groundwater withdrawn from the Chicot and Evangeline aquifers has been the primary source of water for municipal supply, industrial and commercial use, and irrigation in the study area. Groundwater withdrawals cause compaction of clay and silt layers abundant in the aquifers, which has in turn resulted in the widespread, substantial land-surface-elevation changes in the region with increased flooding. To estimate land-surface-elevation changes, the U.S. Geological Survey (USGS), in cooperation with the Harris-Galveston Subsidence District (HGSD), documented land-surface-elevation changes in the study area that occurred during 2000–10 and 2005–10 based on elevation data measured by 11 USGS borehole-extensometer sites, a National Geodetic Survey Continuously Operating Reference Station, and Global Positioning System Port-A-Measure (PAM) sites operated by the HGSD and the Fort Bend Subsidence District. Groundwater withdrawals in the study area also were documented for 1976, 1990, and 2000–10. In 1976, about 428.9 million gallons per day (Mgal/d) were withdrawn from the aquifer system in Harris County, but by 2000, because of HGSD regulation, withdrawals had decreased to about 337.8 Mgal/d, or about a 21-percent reduction since 1976. By 2010, withdrawals had decreased to about 227.1 Mgal/d, or about a 47-percent reduction since 1976. Among the counties in the study area, the largest decrease in groundwater withdrawals has occurred in Galveston County since 1976. In 1976, about 27.4 Mgal/d were withdrawn from the aquifer system, and by 2000, withdrawals had decreased to about 4.12 Mgal/d, or about an 85-percent reduction since 1976. By 2010, withdrawals had decreased to about 0.626 Mgal/d, or about a 98-percent decrease since 1976. Since the mid-1970s, Fort Bend and Montgomery Counties have undergone extensive urban development and corresponding large increases in groundwater withdrawals. Total groundwater withdrawal for Fort Bend County in 1976 was about 16.0 Mgal/d, and by 2000, withdrawals had increased to about 86.5 Mgal/d, or about a 441-percent increase since 1976. By 2010, withdrawals in Fort Bend County had increased to about 99.8 Mgal/d, or about a 524-percent increase since 1976. Total groundwater withdrawal for Montgomery County in 1976 was about 7.84 Mgal/d, and by 2000, withdrawals had increased to about 43.6 Mgal/d, or about a 456-percent increase since 1976. By 2010, withdrawals in Montgomery County had increased to about 64.2 Mgal/d, or about a 719-percent increase since 1976. Total groundwater withdrawal in Brazoria County in 1976 was about 18.0 Mgal/d, and by 2000, withdrawals had increased to about 26.0 Mgal/d, or about a 44-percent increase. By 2010, withdrawals in Brazoria County had increased to about 24.7 Mgal/d, or about a 37-percent increase since 1976. Measured land-surface-elevation changes from December 31, 2000, to December 31, 2010, ranged from an elevation increase of 0.06 feet (ft), or an average increase in elevation of 0.006 ft per year, at the Seabrook borehole extensometer located near Seabrook, Tex., to an elevation decrease of 1.28 ft, or an average decrease in elevation of 0.128 ft per year, at a PAM station north of Jersey Village, Tex. (PAM 07). Measured land-surface-elevation changes from December 31, 2005, to December 31, 2010, ranged from an elevation increase of 0.07 ft, or an average increase in elevation of 0.014 ft per year, at PAM 09 in far northeastern Harris County to an elevation decrease of 0.51 ft, or an average decrease in elevation of 0.102 ft per year, at PAM 07.

Texas↗
USGS1996

Water-quality data for the Arkansas River Basin, southeastern Colorado, 1990-93

Water-quality data were collected and compiled for 59 surface-water stations in the Arkansas River Basin of Colorado. The purpose of the data collection was to describe selected water-quality characteristics of the Arkansas River from the headwaters downstream to the Colorado-Kansas State line. Data are presented for 19 Arkansas River stations, 31 tributary stations, 2 mine-drainage stations, and 7 transmountain diversion stations. Water-quality data presented in this report include instantaneous discharge; onsite measurements of specific conductance, pH, water temperature, and dissolved oxygen; analytical concentrations of bacteria, dissolved solids, major nutrients, trace elements, pesticides, radiochemicals, and suspended sediment; and quality-assurance data for selected water-quality constituents. Sampling began in April 1990 and continued through March 1993 at the 59 surface-water stations. The basinwide water-quality study was initiated in 1988 by the U.S. Geological Survey in cooperation with 14 local agencies and the Bureau of Reclamation.

Colorado↗
USGS2025

Hydrogeologic investigation, framework, and conceptual flow model of the Antlers aquifer, southeastern Oklahoma, 1980–2022

The 1973 Oklahoma Groundwater Law (Oklahoma Statute §82–1020.5) requires that the Oklahoma Water Resources Board conduct hydrologic investigations of the State’s groundwater basins to support a determination of the maximum annual yield for each groundwater basin. Every 20 years, the Oklahoma Water Resources Board is required to update the hydrologic investigation on which the maximum annual yield determinations were based. The maximum annual yield allocated per acre of land is used to set the equal-proportionate share pumping rate. The maximum annual yield of 5,913,600 acre-feet per year and equal-proportionate-share of 2.1 acre-feet per acre per year currently (2025) in place for the Antlers aquifer were issued by the Oklahoma Water Resources Board on February 14, 1995. Because more than 20 years have elapsed since the 1995 final order for the Antlers aquifer was issued, the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, completed an in-depth hydrologic study that included a hydrogeologic framework and conceptual groundwater-flow model for the 1980–2022 study period. The results of an analysis of land use, long-term climate patterns, streamflow and base-flow patterns, historical groundwater use, as well as groundwater-level fluctuations across the Antlers aquifer are described. In addition, groundwater quality was analyzed for total dissolved solids concentrations and major ions for the Antlers aquifer. An updated hydrogeologic framework was developed that included refining the aquifer boundary in Oklahoma, the creation of new potentiometric surface and saturated thickness of fresh groundwater maps, one multiple-well aquifer test, slug tests, and an analysis of lithologic logs across the aquifer. A conceptual groundwater flow model and water budget were developed by incorporating estimates of recharge from precipitation, saturated-zone evapotranspiration, streambed seepage, lateral groundwater flows, vertical leakage, and withdrawals from groundwater wells.

Oklahoma, Texas↗