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At least 1,531 records · Page 85Linked to original sources
USGS1997

Flood-hydrology data for the Potomac River and selected tributaries in the vicinity of the Chesapeake and Ohio Canal National Historical Park, Maryland, West Virginia, and the District of Columbia

This report presents flood-hydrology data for the Potomac River and selected tributaries in the vicinity of the Chesapeake and Ohio Canal National Park (C & O Canal NHP). Data were compiled for the floods of (1) March 17-19, 1936; (2) June 22-24, 1972; (3) November 4-7, 1985; (4) January 19-21, 1996; (5) September 6-8, 1996; and (6) the peak of record for 6 U.S. Geological Survey (USGS) streamflow-gaging stations on the Potomac River and 10 streamflow-gaging stations on selected tributaries to the Potomac River. Peak discharge, peak gage height, the date and time of the peak, and approximate recurrence interval are presented for each flood event at these streamflow-gaging stations.Data compiled from selected high-flow discharge measurements on the six Potomac River streamflow- gaging stations are presented. The gage height, top width, cross-sectional area, mean velocity, maximum velocity, and discharge are presented for each selected discharge measurement. Any corresponding discharge on the C & O Canal that was measured or estimated for these dischrge measurements is presented. Ranges of Manning's roughness coefficient were computed for the range of selected discharge measurements, based on estimates of water-surface slope or the channel-bed slope. These data will be used for subsequent hydraulic studies by engineers for maintenance, protection, or restoration of the C & O Canal. An inventory of selected references, flood studies, and additional USGS data along the Potomac River and the C & O Canal NHP also are presented. Included are (1) a listing of selected flood studies and reports, and (2) a listing of USGS indirect flood-discharge measurements that have been made at the six Potomac River streamflow-gaging stations in the vicinity of the C & O Canal NHP. Information on historical streamflow-gaging station records and discharge measurements on the C & O Canal also is presented.

Open-File Report↗
USGS1998

Geologic, hydrologic, and water-quality data from selected boreholes and wells in and near Belvidere, Illinois, 1989-96

This report presents selected geologic, hydrologic, and water-quality data collected in and near Belvidere, Ill., during 1989-96. The data were collected primarily by the U.S. Geological Survey and U.S. Environmental Protection Agency in support of an ongoing ground-water study of the glacial drift aquifer and bedrock aquifers of Ordovician and Cambrian age underlying the area. These data were collected from 8 boreholes and 52 wells within a 4 square-mile urbanized part of the 80 square-mile study area. Data include stratigraphic, lithologic, and physical descriptions of rock cores from 5 boreholes; geophysical logs of 23 boreholes; surface-geophysical surveys at 3 sites; ground-water levels at 46 wells; horizontal hydraulic conductivity estimated from slug tests at 32 boreholes and wells; and ground-water-quality information at 26 boreholes and wells. Ground-water-quality information include field characteristics and laboratory analyses of inorganic constituents, tritium, volatile organic compounds, and semivolatile organic compounds. Also included are construction logs for 11 monitoring wells and descriptions of the methods used for data collection.

Illinois↗
USGS1997

Hydrologic data from the study of acidic contamination in the Miami Wash-Pinal Creek area, Arizona, water years 1994-96

Since 1984, hydrologic data have been collected as part of a U.S. Geological Survey study of the occurrence and movement of acidic contamination in the aquifer and streams of the Pinal Creek drainage basin near Globe, Arizona. Ground-water data from that study are presented for water years 1994, 1995, and 1996 and include location, construction information, site plans, water levels, chemical and physical field measurements, and selected chemical analyses of water samples for nine monitoring well groups. Monthly precipitation data and long-term precipitation statistics are presented for two sites.

Arizona↗
USGS1997

Hydrologic data, Colorado River and major tributaries, Glen Canyon Dam to Diamond Creek, Arizona, water years 1990-95

The U.S. Geological Survey collected hydrologic data at 12 continuous-record stations along the Colorado River and its major tributaries between Glen Canyon Dam and Diamond Creek. The data were collected from October 1989 through September 1995 as part of the Bureau of Reclamation's Glen Canyon Environmental Studies. The data include daily values for streamflow discharge, suspended-sediment discharge, temperature, specific conductance, pH, and dissolved-oxygen concentrations, and discrete values for physical properties and chemical constituents of water. All data are presented in tabular form.

Open-File Report↗
USGS1998

Hydrologic and hydraulic analyses of selected streams in Erie County, Ohio

Hydrologic and hydraulic analyses were done for parts of Abel Ditch, Edson Creek, Maurer Ditch, and Sherod Creek 1 in northeastern Vermilion Township, Erie County, Ohio. For each stream, instantaneous peak discharges for floods having recurrence intervals of 2, 5, 10, 25, 50, and 100 years were estimated using regional regression equations. Factors used in the regression equations were drainage area, a basin development factor, and average annual precipitation. Drainage areas at the selected stream locations ranged from 0.41 to 4.61 square miles. A step-backwater model was used to determine water-surface elevation profiles for the 10- year-recurrence-interval (10-year) flood along a selected reach of each stream. The water-surface profile information was then used to prepare a map of flood-plain boundaries. Hydraulic analyses indicated that the 10-year flood was generally confined within the stream channels. At three locations, however, some of the flood discharge escaped the main channel and flowed overland. In two cases, the overland flow returned to the channel from which it escaped. In the third case, flow drained into an adjacent basin. A separate analysis, in which concurrent flood peaks on the streams studied were assumed, indicated that water would spill over the Sherod Creek and the Maurer Ditch divides and that some of this water would eventually enter the Edson Creek Basin downstream from the study area. 1 Locally the upper reach of Sherod Creek, south of the Conrail Railroad, is known as Japson Ditch. However, for simplicity it will be referred to as Sherod Creek along its entirety.

Ohio↗
USGS1998

Summary statistics and graphical comparisons of historical hydrologic and water-quality data, Seco Creek Watershed, South-Central Texas

The U.S. Geological Survey collected hydrologic (rainfall, streamflow, and reservoir content) and water-quality data in the Seco Creek watershed, south-central Texas. Most of the data from 15 sites were collected as part of a study in cooperation with the U.S. Department of Agriculture and the Texas State Soil and Water Conservation Board to evaluate the effects of agricultural best-management practices on surface- and ground-water quantity and quality in the 255-square-mile watershed. Nearly 400 best-management practices at 58 sites were implemented by landowners in the watershed during March 1990-September 1995. Most of the data are from the early 1990s, the period during and after implementation of best-management practices. Data from five sites include water quality and are summarized in tables and graphics in the text; and data from all 15 sites are summarized on a diskette. Maximum annual rainfall among the sites for which data are presented in the text (excluding one site) for the during-and-after-implementation period (March 1990-September 1995) was 53.27 inches in water year 1992. Maximum annual total streamflow among the sites for the period was 63,400 acre-feet, also in water year 1992. At the one site with water-quality data (under base-flow conditions) for both the before-implementation period and the during-and-after implementation period of best-management practices, percentiles (5, 25, 50, 75, 95) for specific conductance, nitrate concentration, and fecal coliform density were less for the during-and-after-implementation period than for the before-implementation period.

Texas↗
USGS1998

Ground-water hydrology and simulation of ground-water flow at Operable Unit 3 and surrounding region, U.S. Naval Air Station, Jacksonville, Florida

The Naval Air Station, Jacksonville (herein referred to as the Station), occupies 3,800 acres adjacent to the St. Johns River in Duval County, Florida. Operable Unit 3 (OU3) occupies 134 acres on the eastern side of the Station and has been used for industrial and commercial purposes since World War II. Ground water contaminated by chlorinated organic compounds has been detected in the surficial aquifer at OU3. The U.S. Navy and U.S. Geological Survey (USGS) conducted a cooperative hydrologic study to evaluate the potential for ground water discharge to the neighboring St. Johns River. A ground-water flow model, previously developed for the area, was recalibrated for use in this study. At the Station, the surficial aquifer is exposed at land surface and forms the uppermost permeable unit. The aquifer ranges in thickness from 30 to 100 feet and consists of unconsolidated silty sands interbedded with local beds of clay. The low-permeability clays of the Hawthorn Group form the base of the aquifer. The USGS previously conducted a ground-water investigation at the Station that included the development and calibration of a 1-layer regional ground-water flow model. For this investigation, the regional model was recalibrated using additional data collected after the original calibration. The recalibrated model was then used to establish the boundaries for a smaller subregional model roughly centered on OU3. Within the subregional model, the surficial aquifer is composed of distinct upper and intermediate layers. The upper layer extends from land surface to a depth of approximately 15 feet below sea level; the intermediate layer extends from the upper layer down to the top of the Hawthorn Group. In the northern and central parts of OU3, the upper and intermediate layers are separated by a low-permeability clay layer. Horizontal hydraulic conductivities in the upper layer, determined from aquifer tests, range from 0.19 to 3.8 feet per day. The horizontal hydraulic conductivity in the intermediate layer, determined from one aquifer test, is 20 feet per day. An extensive stormwater drainage system is present at OU3 and the surrounding area. Some of the stormwater drains have been documented to be draining ground water from the upper layer of the surficial aquifer, whereas other drains are only suspected to be draining ground water. The subregional model contained 78 rows and 148 columns of square model cells that were 100 feet on each side. Vertically, the surficial aquifer was divided into two layers; layer 1 represented the upper layer and layer 2 represented the intermediate layer. Steady-state ground-water flow conditions were assumed. The model was calibrated to head data collected on October 29 and 30, 1996. After calibration, the model matched all 67 measured heads to within the calibration criterion of 1 foot; and 48 of 67 simulated heads (72 percent) were within 0.5 foot. Model simulated recharge rates ranged from 0.4 inch per year in areas that were largely paved to 13.0 inches per year in irrigated areas. Simulated hydraulic conductivities in the upper layer at OU3 ranged from 0.5 foot per day in the north to 1.0 foot per day in the south. Simulated vertical leakance between the upper and intermediate layers ranged from 1.0x10-6 per day in an area with low-permeability clays to 4.3x10-2 per day in an area that had been dredged. Simulated transmissivities in the intermediate layer ranged from 25 feet squared per day in an area of low-permeability channel-fill deposits to a high of 1,200 feet squared per day in areas covering most of OU3. Simulated riverbed conductances ranged from 4 to 60 feet squared per day and simulated bottom conductances of leaking stormwater drains ranged from 5 to 20 feet squared per day. The direction and velocity of ground-water flow was determined using particle-tracking techniques. Ground-water flow in the upper layer was generally eastward toward the St. Johns River. However, leaking stormwater drains locally modified the flow system to create small areas with flow that was diverted to the drains. The flow velocities in the upper layer at OU3 were slow, averaging about 2 feet per year. The slow velocities were primarily the result of the low horizontal hydraulic conductivity and, secondarily, the result of the low recharge rate. The simulated rate at which ground water leaked into the stormwater drains was low, averaging about 0.0011 cubic feet per second per 100 feet of stormwater drainage conduit. Ground-water flow in the intermediate layer moved eastward toward and discharged into the St. Johns River. Flow velocities were significantly higher in this layer than in the upper layer. The velocity was about 35 and 12 feet per year in the northern and southern parts of OU3, respectively.

Florida↗
USGS1996

Geochemistry and isotope hydrology of representative aquifers in the Great Basin region of Nevada, Utah, and adjacent states

This report briefly describes the general quality and chemical character of the ground water, discusses in detail the geochemical and hydrologic processes that produce the chemical and isotopic compositions of water in the two principal types of aquifers (basin fill and carbonate rock), delineates flow systems in carbonate-rock aquifers of southern Nevada, and discusses ground-water ages and flow velocities within the carbonate-rock systems.

Professional Paper↗
USGS1996

Hydrology of the southeastern Coastal Plain aquifer system in South Carolina and parts of Georgia and North Carolina

The wedge of sediments present beneath the Coastal Plain of South Carolina and adjacent parts of Georgia and North Carolina consists of sand, silt, clay, and limestone. These strata have been subdivided into six regional aquifers: the surficial aquifer, the Floridan aquifer system, the Tertiary sand aquifer, the Black Creek aquifer, the Middendorf aquifer, and the Cape Fear aquifer. Intervening confining units separate the aquifers, except for the Floridan aquifer system and the Tertiary sand aquifer, which together function as a single hydrologic unit. The quality of ground water from the Coastal Plain aquifers of South Carolina generally is acceptable for most uses in most areas. The water in most aquifers under most of the Coastal Plain contains low concentrations of dissolved solids (less than 500 milligrams per liter) and no dominant constituents in the recharge areas. Downgradient, the water is a calcium bicarbonate or sodium bicarbonate type throughout most of the Coastal Plain. Sodium-chloride-type water is present still farther downgradient, near the coast. A quasi-three-dimensional, finite-difference digital ground-water flow model was constructed to simulate flow in the Coastal Plain aquifers prior to development. The model also was used to evaluate the hydraulic responses to pumping that have occurred up to November 1982. The model consisted of five layers and a 48 by 63 node grid with a uniform square grid cell of 4 miles on a side. The Coastal Plain aquifers are recharged primarily by precipitation in their outcrop areas. Discharge is primarily as base flow to upper Coastal Plain rivers, to overlying aquifers by leakage through confining units, and to wells. Total simulated flow in the deep ground-water system was 967 cubic feet per second at the end of the transient simulation (1982). Recharge to the deep flow system simulated by the model was 793 cubic feet per second in the study area in 1982. Simulated aquifer discharge to large rivers was 660 cubic feet per second. Discharge to smaller rivers was not simulated because of the scale of the model. Changes resulting from ground-water pumping were significant as of 1982. The simulated water budget indicates that in 1982, 249 cubic feet per second were discharged from the aquifer system by wells. This pumping was balanced by the following changes from predevelopment conditions: 110 cubic feet per second derived from storage, 67 cubic feet per second decrease in aquifer-to-river discharge, 44 cubic feet per second increase in net inflow from source-sinks, and a net increase in inflow of 28 cubic feet per second across boundaries. Head declines in the Black Creek and Middendorf aquifers have occurred throughout much of the eastern part of the Coastal Plain of South Carolina as a result of pumping in the Myrtle Beach and Florence areas. Simulation indicates that the dominant sources of water for upper Coastal Plain pumping centers such as the city of Florence are decrease in flow to rivers in the upper Coastal Plain and water derived from storage. The dominant sources of water for pumping centers in the Myrtle Beach area are water derived from storage, leakage from overlying aquifers, and net increases in inflow across boundaries. Transmissivity values used in the flow simulation range from less than 1,000 feet squared per day near the updip limit of most aquifers to about 30,000 feet squared per day in the Middendorf aquifer in the Savannah River Plant area. Vertical hydraulic conductivity values used in simulation of confining units range from about 6x10 -7 feet per day for the confining unit between the Middendorf and Black Creek aquifers in coastal areas to 3x10 -2 feet per day for most of the confining units near their updip limits. Storage coefficients used in transient simulations were 0.15 where unconfined conditions exist and 0.0005 where confined conditions exist.

Georgia, North Carolina, South Carolina↗
USGS2023

Determining three-dimensional hydrologic processes in the eastern Snake River Plain aquifer using geochemical mass-balance modeling, Idaho National Laboratory, eastern Idaho, with contributions by Treinen, K.C.

Waste constituents discharged to the eastern Snake River Plain aquifer at the U.S. Department of Energy (DOE) Idaho National Laboratory (INL) pose risks to the water quality of the aquifer. To understand these risks, the U.S. Geological Survey, in cooperation with the DOE, used geochemical mass-balance modeling to identify three-dimensional hydrologic processes in that portion of the aquifer underlying the southwestern part of the INL that affect the movement of groundwater and waste constituents. Modeling was performed using water chemistry of 74 water samples collected from 30 wells. Fifty-four of the water samples were collected from 11 wells equipped with multilevel monitoring systems with vertically discrete sampling zones that encompass the upper 750 feet of the aquifer. Water samples from these multilevel wells were collected during 2007‒13, a period when conditions in the aquifer were approximately steady-state because there was little or no recharge from the Big Lost River. The primary source of water in groundwater at the multilevel wells during 2007‒13 was the Big Lost River. Other sources of water include groundwater from the Little Lost River valley, precipitation, and wastewater. Horizontal groundwater-flow directions appear to be similar in both the shallow and deep parts of the aquifer, and surface-water sources of water in most deep groundwater shows that groundwater moves downward. Surface-water sources of water in deep groundwater noticeably decrease within and below the Matuyama flow and associated sedimentary interbeds, which indicates that these units are semi-impermeable and retard the downward movement of groundwater.

Idaho↗
USGS1961

Short papers in the geologic and hydrologic sciences; Articles 1-146

The scientific and economic results of work by the United States Geological Survey during the fiscal year 1961, the 12 months ending June 30, 1961, will be summarized in four volumes of which this is the first. This volume includes 146 short papers on a variety of subjects in the fields of geology, hydrology, and related sciences, prepared by members of the Geologic, Water Resources, and Conservation Divisions of the Survey. These papers are of two kinds. Some are announcements of new discoveries or observations on problems of limited scope, which may or may not be described in greater detail subsequently. Others summarize conclusions drawn from more extensive or continuing investigations, which in large part will be described in greater detail in reports to be published at a· later date. Professional Papers 424-C and -D include additional short papers of the same character as those in the present volume. Professional Paper 424-A provides a synopsis of the more important new findings resulting from work during the fiscal year.

Professional Paper↗
USGS1962

Short papers in geology, hydrology, and topography; Articles 1-59: Geological Survey Research 1962

This collection of 59 short papers on subjects in the fields of geology, hydrology, topography, and related sciences is one of a, series to be relea~ed during the year as chapters of Professional Paper 450. The papers in this chapter report on the scientific and economic· results of current work by members of the Geologic, Topographic, and 'Vater Resources Division of the United States Geological Survey. Some of the pa.pers annom1ce new discoveries or present observations on problems of limited scope; other papers draw conclusions from more extensive or continuing investigations that in large part will be discussed in greater detail in reports to be published in the future.

Professional Paper↗
USGS1962

Short papers in geology, hydrology, and topography; articles 120-179

This collection of 60 short papers on subjects in the fields of geology, hydrology, topography, and related sciences is the third of a series to be released during the year as chapters of Professional Paper 450. The papers in this chapter report on the scientific and economic results of current work by members of the Geologic, Water Resources, and Topographic Divisions of the United States Geologicai Survey. Some of the papers announce new discoveries or present observations on problems of limited scope; other papers draw conclusions from more extensive or continuing investigations that in large part will be discussed in greater detail in reports to be published in the future. Chapter A of this series, to be published later in the year, will present a synopsis of results from a wide range of work done during the present fiscal year.

Professional Paper↗
USGS1963

Short papers in geology, hydrology, and topography: Articles 180-239

This collection of 60 short papers on subjects in the fields of geology, hydrology, topography, and related sciences is the last of a series released as chapters of Professional Paper 450. The papers in this chapter report on the scientific and economic results of current work by members of the Conservation, Geologic, Topographic, and Water Resources Divisions of the United States Geological Survey. Some of the papers announce new discoveries or present observations on problems of limited scope; other papers draw conclusions from more extensive or continuing investigations that in large part will be discussed in greater detail in reports to be published in the future. Chapter A of this series presents a synopsis of results from a wide range of work done during the 1962 fiscal year.

Professional Paper↗
USGS1966

The Alaska earthquake, March 27, 1964: effects on hydrologic regimen

This is the fourth in a series of six reports that the U.S. Geological Survey published on the results of a comprehensive geologic study that began, as a reconnaissance survey, within 24 hours after the March 27, 1964, Magnitude 9.2 Great Alaska Earthquake and extended, as detailed investigations, through several field seasons. The 1964 Great Alaska earthquake was the largest earthquake in the U.S. since 1700. Professional Paper 544, in 5 parts, describes the effects on hydrologic regimen.

Alaska↗
USGS1966

Effects of the March 1964 Alaska earthquake on the hydrology of the Anchorage area, Alaska

The Anchorage hydrologic system was greatly affected by the seismic shock. Immediate but temporary effects included increased stream discharge, seiche action on lakes, and fluctuations in ground-water levels. Generally, ground-water levels were residually lowered after the initial period of fluctuation. This lowering is attributed either to changes in the discharge zones offshore or to a change in the permeability of the aquifers by seismically induced strain. Water supplies were disrupted temporarily by snowslides on streams and by sanding or turbidity in wells. Salt-water encroachment to wells on Fire Island seems to have increased. The approximate 3.7-foot lowering of land level and the diminished artesian head may permit further salt-water encroachment. Increased pore pressure in the Pleistocene Bootlegger Cove Clay led to liquefaction in silt and sand lenses that contributed to the disastrous bluff landslides. Measurements after the earthquake indicate that most pore pressures are declining, whereas some remain high or are increasing. Subsidence in the area was caused principally by tectonic readjustment, but differential compaction within the Bootlegger Cove Clay contributed to subsidences estimated to be as much as 0.6 foot beneath Anchorage.

Alaska↗
USGS2020

Potentiometric surface and hydrologic conditions of the South Coast aquifer, Santa Isabel area, Puerto Rico, March–April, 2014

A potentiometric surface map of the South Coast aquifer near Santa Isabel, Puerto Rico, was created from data collected during a synoptic survey of groundwater levels at 55 wells from March 31 to April 17, 2014. Measured groundwater level values ranged from −22.8 to 185.4 feet above mean sea level. During the study period, cumulative rainfall of 0.65 inch was recorded in the study area. Measurements of instantaneous streamflow at 15 locations in streams and irrigation canals, and locations of irrigation ponds, provide additional information about the hydrologic setting. Results of the study indicate a cone of depression was present near the center and eastern parts of the Santa Isabel area of southern Puerto Rico, and a small, deeper cone of depression existed west of Santa Isabel and Rio Coamo. These cones of depression represent areas where the potentiometric surface was below mean sea level. The long-term persistence of such conditions could result in seawater intrusion and an increase in concentrations of total dissolved solids within the South Coast aquifer.

Puerto Rico↗
USGS2004

Hydrology and ground-water quality in the mine workings within the Picher Mining District, Northeastern Oklahoma, 2002-03

The Picher mining district of northeastern Ottawa County, Oklahoma, was a major site of mining for lead and zinc ores in the first half of the 20th century. The primary source of lead and zinc were sulfide minerals disseminated in the cherty limestones and dolomites of the Boone Formation of Mississippian age, which comprises the Boone aquifer. Ground water in the aquifer and seeping to surface water in the district has been contaminated by sulfate, iron, lead, zinc, and several other metals. The U.S. Geological Survey, in cooperation with the Oklahoma Department of Environmental Quality, investigated hydrology and ground-water quality in the mine workings in the mining district, as part of the process to aid water managers and planners in designing remediation measures that may restore the environmental quality of the district to pre-mining conditions. Most ground-water levels underlying the mining district had similar altitudes, indicating a large degree of hydraulic connection in the mine workings and overlying aquifer materials. Recharge-age dates derived from concentrations of chlorofluorocarbons and other dissolved gases indicated that water in the Boone aquifer may flow slowly from the northeast and southeast portions of the mining district. However, recharge-age dates may have been affected by the types of sites sampled, with more recent recharge-age dates being associated with mine-shafts, which are more prone to atmospheric interactions and surface runoff than the sampled airshafts. Water levels in streams upstream from the confluence of Tar and Lytle Creeks were several feet higher than those in adjacent portions of the Boone aquifer, perhaps due to low-permeability streambed sediments and indicating the streams may be losing water to the aquifer in this area. From just upstream to downstream from the confluence of Tar and Lytle Creeks, surface-water elevations in these streams were less than those in the surrounding Boone aquifer, indicating that seepage from the aquifer to downstream portions of Tar Creek was much more likely. Water properties and major-ion concentrations indicate that water in the mining area was very hard, with large concentrations of dissolved solids that increased from areas of presumed recharge toward areas with older ground water. Most of the ground-water samples, particularly those from the airshafts, had dissolved-oxygen concentrations less than 1.0 milligram per liter. Small concentrations of dissolved oxygen may have been introduced during the sampling process. The small dissolved-oxygen concentrations were associated with samples containing large iron concentrations that indicates possible anoxic conditions in much of the aquifer. Ground water in the mining district was dominated by calcium, magnesium, and sulfate. Sodium concentrations tended to increase relative to calcium and magnesium concentrations. Ground-water samples collected in 2002-03 had large concentrations of many trace elements. Larger concentrations of metals and sulfate occurred in ground water with smaller pHs and dissolved-oxygen concentrations. Iron was the metal with the largest concentrations in the ground-water samples, occurring at concentrations up to 115,000 micrograms per liter. Cadmium, lead, manganese, zinc, and the other analyzed metals occurred in smaller concentrations in ground water than iron. However, larger cadmium concentrations appeared to be associated with sites that have small iron concentrations and more oxygenated waters. This is noteworthy because the small sulfate and iron concentrations in these waters could lead to conclusions that the waters are less contaminated than waters with large sulfate and iron concentrations. Ground-water quality in the mining district was compared with subsets of samples collected in 1983-85 and in 2002.

Oklahoma↗