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At least 631 records · Page 35Linked to original sources
USGS1999

Water resources data, Pennsylvania, water year 1998. Volume 3. Ohio River and St. Lawrence River basins

Water resources data for the 1998 water year for Pennsylvania consists of records of discharge and water quality of streams; contents and elevations of lakes and reservoirs; and water levels of ground-water wells. This report, Volume 3, includes records from the Ohio and St. Lawrence River Basins. Specifically, it contains: (1) discharge records for 62 continuous record streamflow-gaging stations and 18 partial-record and miscellaneous streamflow stations; (2) elevation and contents records for 11 lakes and reservoirs; (3) water-quality records for 10 streamflow-gaging stations; and (4) water-level records for 15 network observations wells. Additional water data were collected at various sites not involved in the systematic data-collection program and are published as miscellaneous measurements and analyses. These data, together with the data in Volume 1 and 2, represent that part of the National Water Data System operated by the U.S. Geological Survey and cooperating State, Municipal, Local, and Federal agencies in Pennsylvania.

Pennsylvania↗
USGS2001

Water resources data, South Carolina, water year 2001

Water resources data for the 2001 water year for South Carolina consist of records of stage, discharge, and water quality of streams; stage and contents of lakes and reservoirs; and ground-water levels. This report contains discharge records for 121 gaging stations; stage-only records for 44 gaging stations; stage and co ntents for 14 lakes and reservoirs; water quality for 47 gaging stations; and water levels for 43 observation wells. Als o included are data for 52 crest-stage partial-record stations and discharge measurements at 7 miscellaneous sites. Add itional water data were collected at various sites, not part of the systematic data collection program, and are publish ed as miscellaneous investigations of water quality. These data represent that part of the National Water Data System co llected by the U.S. Geological Survey and cooperating State and Federal agencies in South Carolina.

South Carolina↗
USGS1996

Water-quality assessment of southern Florida: An overview of available information on surface- and ground-water quality and ecology

This report summarizes water-quality conditions, issues of concern, and management efforts underway in southern Florida. The report is designed to provide a conceptual framework for the Southern Florida National Water Quality Assessment (NAWQA) study that began in 1994. The report makes reference to the most important water-quality literature pertaining to southern Florida, to water-quality studies that are underway or planned, and to topics which are of high priority in the study unit. These topics include: the availability and suit ability of water for competing demands; nutrient enrichment of the Everglades; transport, degradation, and effects of pesticides; and the sources and cycling of mercury in the ecosystem. The report also includes a retrospective analysis and conceptual presentation of nutrient loading, which is a high priority for the national NAWQA Program and for regional water-quality managers. Nutrient contributions from point and nonpoint sources are estimated for nine basins in the study area and are discussed in relation to land use. Fertilizer is the dominant source of phosphorus in eight basins and the dominant source of nitrogen in at least five basins. Atmospheric sources of nitrogen contribute more than 20 percent of the total nitrogen input to all basins and are the dominant source of nitrogen input to Lake Okeechobee and the Everglades. Nutrient loads are also estimated in selected canal and river outflows in southern Florida to provide a spatial overview of the magnitude of nutrient loading to coastal waters. Annual phosphorus loads from the Peace River are the highest in the study unit; annual phosphorus loads from the Caloosahatchee River and the major Palm Beach canals are also high, compared to other parts of southern Florida. Estimated annual loads of phosphorus from parts of the Big Cypress Basin and the S-12 water-control structures of the Tamiami Canal are low compared with estimated phosphorus loads in outflows in the northern part of the study unit. Annual nitrogen loads in southern Florida were highest in outflows from the Caloosahatchee River Basin and the major Palm Beach canals. Nitrogen loads in outflows from parts of the Big Cypress subbasin were lower than those estimated to the north.

Florida↗
USGS1997

Assessment of the water resources of the Grand Ronde area, Oregon

Stream hydrographs show that throughout the Grand Ronde area most precipitation follows surface or shallow subsurface pathways to streams, resulting in rapid runoff and little natural water storage within the basin. Limited storage and low aquifer permeability restrict base flow to streams, and streamflows therefore decline rapidly once precipitation ceases. Shallow ground water and springs occur throughout the area, but because of the low permeability of aquifer materials, nearly all wells and springs have low yields. Water quality in streams, wells, and springs is generally good, but saline ground water has been reported on a number of drillers' logs for the study area and in several previous investigations of nearby areas. Further development of water resources in the Grand Ronde area is likely to be constrained by existing downstream water rights, the low permeability of geologic materials throughout the area, and possibly the intrusion of saline water. However, construction of facilities to store available water and thus compensate for low yields could provide a reliable, sustainable water supply for the Grand Ronde area.

Oregon↗
USGS1984

Appraisal of data for ground-water quality in Nebraska

This report summarizes existing data for groundwater quality in Nebraska and indicates their adequacy as a data base. Analyses have been made of water from nearly 10,000 wells by 8 agencies. Those analyses that meet reliability criteria have been aggregated by geologic source of water into four principal aquifer groupings--Holocene-Pleistocene aquifers, Tertiary aquifers, Mesozoic aquifers, and Paleozoic aquifers. For each aquifer grouping, data for specific conductance and 24 constituents in the water are summarized statistically. Also, diagrams are presented showing differences in statistical parameters, or in chemical composition, of water from the different aquifer groupings. Additionally, for each grouping except Paleozoic aquifers, maps show ranges in concentration of dissolved solids, calcium, alkalinity, and sulfate. In areas where data are insufficient to delimit, ranges in concentration also are shown on the maps. Point-source contamination has been identified at 41 locations and nonpoint-source contamination in 3 areas, namely, the central Platte Valley, Holt County, and Boyd County. Potential for nonpoint-source contamination exists in 10 major areas, which together comprise more than one-third of the State. Existing data are mostly from specific projects having limited areas and objectives. Consequently, a lack of data exists for other areas and for certain geologic units, particularly the Mesozoic and Paleozoic aquifers. Specific data needs for each of the four principal aquifer groupings are indicated in a matrix table.

Water Supply Paper↗
USGS1972

Ground-water conditions in the central Virgin River basin, Utah

Water-rights problems have occurred in the central Virgin River basin and are expected to increase as development of the water resources increases. The Utah State Engineer needs a basic knowledge of ground-water conditions and of the relation of ground water to surface water as a first step to understanding and resolving the problems. Accordingly, the State Engineer requested the U. S. Geological Survey to make a ground-water investigation of the central Virgin River basin as part of the Statewide cooperative agreement with the Utah Department of Natural Resources. The investigation was begun July 1, 1968, and fieldwork was completed in August 1970. Detailed information was obtained for the principal aquifers and for recharge, movement, discharge, storage, utilization, and chemical quality of ground water. A progress report (Cordova, Sandberg, and McConkie, 1970) describes the general findings in the first year of the investigation.

Utah↗
USGS1972

Shallow ground water in the Zamin Dawar area, Helmand Province, Afghanistan

The Zamin Dawar area lies between Kajakai Reservoir and Musa Qala Rud (river) in southcentral Afghanistan, about 90 km (kilometers) northeast of Lashkar Gab. The area comprises two main stream drainage areas: that of Gulmesh Mandeh (ephemeral stream) to the east which includes mostly plains with low hills on the east and north slopes and a high limestone scarp on the west slope; and Baghni Rud to the west which drains a mountainous area to the north and spreads onto a large alluvial fan with distributaries leading both to Helmand Rud to the southeast and Musa Qala Rud to the west. Most of the cultivated lands in the Zamin Dawar area lie in the southern part of the Gulmesh plains and in the Baghni alluvial fan, as well as a ribbon of cultivation on the flood plain of Baghni Rud in the mountains. The southern end of the Zamin Dawar area with high terraces and sharply incised ephemeral stream valleys is uninhabited. Karezes provide the chief source of water in the plains. Some 80 were examined and inventoried during the course of the present investigation. Several springs and one large-yield well also contribute to the water supply on the plains. In Baghni valley, developed springs provide the main source of water supply. During the present investigation, conducted in 1971,. it was found that the karezes yield a total of about 20,000 ac-ft (acre-feet) (25 million cu m (cubic meters)) of water The springs on the plains yield about 3,000 ac-ft (4 million cu m) per year, and the wells yield about 300 ac-ft (375,000 cu m) per year. The inventoried springs in Baghni valley yield about 6,500 ac-ft (8 million cu m) per year, and probably supply about 70 percent of the total water used in the valley. Therefore,the total amount of water used in the Zamin Dawar area in 1971 was about 32,000 ac-ft (40 million cu m). This amount of water was used to irrigate about i0,000 jiribs (approximately 5,000 acres or 2,000 hectares) of cultivated land and served a population of about 40,000 people. Twenty years ago the water supply was more than double the 1971 flow from karezes and springs, and the population of the area was probably 60,000 to 70,000 people. During the past 10 years and particularly during the last 3 years, the water table has been declining as a direct result of a dry-weather cycle which has affected much of Afghanistan. Concurrently, the population of the area has declined. Rainfall, based on data from the Kajakai Camp weather station, has declined from a 27-year annual average of about 200 mm (millimeters) to about 160 mm per year, which is the annual average for the last 5 years and equivalent to a reduction of approximately 70,000 ac-ft (88 million cu m) of precipitation per year over the entire area. To compensate for the declining water levels many karezes have been deepened or lengthened at great financial cost to the people. This report evaluates present ground-water conditions in the area and suggests ways-and means by which more water can be obtained for local requirements.

Open-File Report↗
USGS2001

Hydraulic and mechanical properties affecting ground-water flow and aquifer-system compaction, San Joaquin Valley, California

This report summarizes hydraulic and mechanical properties affecting ground-water flow and aquifer-system compaction in the San Joaquin Valley, a broad alluviated intermontane structural trough that constitutes the southern two-thirds of the Central Valley of California. These values will be used to constrain a coupled ground-water flow and aquifer-system compaction model of the western San Joaquin Valley called WESTSIM. A main objective of the WESTSIM model is to evaluate potential future land subsidence that might occur under conditions in which deliveries of imported surface water for agricultural use are reduced and ground-water pumping is increased. Storage values generally are components of the total aquifer-system storage and include inelastic and elastic skeletal storage values of the aquifers and the aquitards that primarily govern the potential amount of land subsidence. Vertical hydraulic conductivity values generally are for discrete thicknesses of sediments, usually aquitards, that primarily govern the rate of land subsidence. The data were compiled from published sources and include results of aquifer tests, stress-strain analyses of borehole extensometer observations, laboratory consolidation tests, and calibrated models of aquifer-system compaction.

Open-File Report↗
USGS1998

Hydrogeology and water quality in the Cedar Rapids area, Iowa, 1992-96

The U.S. Geological Survey (USGS) and the city of Cedar Rapids conducted a cooperative study from 1992 to 1996 to assess the hydrogeology and water quality in the Cedar River, Cedar River alluvial aquifer, Devonian aquifer, and Silurian aquifer in a 231-square-mile area of Benton and Linn Counties near Cedar Rapids, Iowa. The city of Cedar Rapids withdrew an average of 34 million gallons per day between July 1,1995, and June 30, 1996, from the Cedar River alluvial aquifer for its drinking-water supply. The ground-water flow system in the 231-square-mile area was simulated using a modular, three-dimensional, finite-difference groundwater flow model (MODFLOW) under steady-state conditions. The three-layer groundwater flow model simulates ground-water flow in layer 1 for unconsolidated deposits that include the Cedar River alluvial aquifer; in layer 2 for the Devonian aquifer and buried-channel aquifer; and in layer 3 for the Silurian aquifer. Primary sources of inflow to the ground-water flow system in the model area include infiltration of precipitation (63.5 percent) and leakage from the Cedar River (34.7 percent). Pumpage from municipal, industrial, and private wells accounts for about 48.3 percent of system outflow. Primary sources of inflow to the Cedar River alluvial aquifer include leakage from the Cedar River (74.2 percent), leakage from adjacent or underlying hydrogeologic units (20.9 percent), and infiltration of precipitation (4.9 percent). Pumpage by municipal water-supply wells from the alluvial aquifer accounts for about 78.0 percent of system outflow. Simulations of two hypothetical conditions using the steady-state ground-water flow model were conducted to evaluate quantitative changes on sources of water to the Cedar River alluvial aquifer. Results for the scenario representing a period of less-than-average annual precipitation for 1961-90 indicate a 32.0-percent reduction of total ground-water flow and a 5.7-percent increase in river leakage to the Cedar River alluvial aquifer. Results for the scenario representing increased pumping from the Cedar River alluvial aquifer, with pumping increased 68.3 percent from about 41 million gallons per day (for the calibrated model) to about 70 million gallons per day, indicate a 70.9-percent increase in simulated river leakage. Commonly used herbicides in Iowa such as atrazine (and the metabolite products deethylatrazine and deisopropylatrazine), cyanazine, and metolachlor, when detected in the Cedar River alluvial aquifer, were typically at small concentrations (less than 1.0 microgram per liter). Atrazine concentrations in 26 of the 64 wells sampled were less than the 0.05 microgram per liter minimum reporting level. Most ground-water samples collected from the Devonian and Silurian aquifers had herbicide concentrations less than 0.05 microgram per liter. Nitrite-plus-nitrate nitrogen (nitrate) concentrations in ground-water samples varied from less than the minimum reporting level (0.05 milligram per liter) to 15.0 milligrams per liter. Nitrate was not detected in samples from 18 wells, and nitrate concentrations greater than the Maximum Contaminant Level for nitrate as nitrogen (10 milligrams per liter) were detected in samples from 4 wells. Several areas in the Cedar River alluvial aquifer with large iron and manganese concentrations could be related to the original depositional environment of the sediment. In general, large iron and manganese concentrations in ground water are often associated with abundant organic and argillaceous material in sediment near old meander channels and sloughs.

Iowa↗
USGS1941

Contamination of Lake Wewoka and fresh-water sands by disposal of oil-well brines near Wewoka, Seminole County, Oklahoma

This report deals with ground-water conditions in an area about 5 miles wide from east to west and 8 miles long from north to south, in Tps. 8 and 9 N., Rs. 7 and 8 E., in Seminole County, Oklahoma, including the town of Wewoka and Lake Wewoka. The possible contamination of the lake waters from oil-well brines disposed through a well 3.75 miles north of the lake, and other effects of brine disposal, are considered. The investigation was made at the request of Frank Raab, member of the Oklahoma Planning and Resources Board, and Don McBride, Chief Engineer of the Division of Water Resources who has the responsibility of preventing contamination of water supplies in Oklahoma. Field work was done July 5 and 6, 1941, by Robert H. Dott, Director of the Oklahoma Geological Survey; C.G. Lalicker, Department of Geology, University of Oklahoma; and S.L. Schoff, Assistant Geologist in the Ground Water Division, Water Resources Branch, of the U.S. Geological Survey. Lalicker spent both days studying the rocks exposed in the vicinity and measuring their thickness. A copy of the composite section measured by him is attached. Dott and Schoff spent one day collecting the well information summarized in Table 1, and one day with Lalicker on the stratigraphy.

Oklahoma↗
USGS1955

Test drilling and aquifer test in the Marburg schist near Mount Airy, Frederick County, Maryland

This memorandum summarizes briefly the data obtained by test drilling and in an aquifer test at Mount Airy, Md. The tests were a part of the State - Federal cooperative study of the ground-water resources of Frederick County, and it is intended that a more complete analysis of the test data will be included in a future report describing the ground-water resource of Frederick County. The purpose of this memorandum is to make the test data immediately available to the general public. Mount Airy is located along the Carroll-Frederick County boundary bout 2 miles north of the intersection of U.S. Highway 40 with the county boundary. Its population is approximately 1,000. The municipal well field, consisting of two drilled wells (fig. 1) is in a valley about one-half mile west of the center of Mount Airy, within about 400 feet of a small stream, and north of Prospect Road. Well 1, about 40 feet north of Prospect Road, is 125 feet deep, 8 inches in diameter, and reportedly yielded 265 gallons per minute (gpm) in 1947 and 201 gpm in a half hour test in March 1955. The writer determined during the tests described in this memorandum that the well has about 34 feet of casing. Well 2, 85 feet north of well 1, is 96 feet deep, 8 inches in diameter, and reportedly yielded 120 gpm in 1947 and 127 gpm in a half hour test in March 1955. The wells are equipped with deep-well turbine pumps powered by electric motors. Cenorally only well 1 is used, and it is pumped for only a few short intervals each day to meet the water requirements of the town (about 75,000 - 80,000 gallons daily). The reported yields of these wells are considerably higher than the average for crystalline-rock wells in the Piedmont of Maryland. The test drilling was done under contract with Edward I. Brown, well driller, between May 3 and May 12, 1955. Water-supply facilities of the town of Mount Airy were kindly made available for the aquifer tests from May 22 to May 30, 1955. The pumping tests consisted of a step-drawdown and interference test on the public-supply wells on May 30, 1955, and aquifer test in which public-supply well 1 was pumped constantly for 48 hours and the effect of this pumpage was measured in all the wells and test holes on May 23-25.

Maryl↗
USGS2007

Ground-Water Quality in the Delaware River Basin, New York, 2001 and 2005-2006

The Federal Clean Water Act Amendments of 1977 require that States monitor and report on the quality of ground water and surface water. To satisfy part of these requirements, the U.S. Geological Survey and New York State Department of Environmental Conservation have developed a program in which ground-water quality is assessed in 2 to 3 of New York State's 14 major basins each year. To characterize the quality of ground water in the Delaware River Basin in New York, water samples were collected from December 2005 to February 2006 from 10 wells finished in bedrock. Data from 9 samples collected from wells finished in sand and gravel in July and August 2001 for the National Water Quality Assessment Program also are included. Ground-water samples were collected and processed using standard U.S. Geological Survey procedures. Samples were analyzed for more than 230 properties and compounds, including physical properties, major ions, nutrients, trace elements, radon-222, pesticides and pesticide degradates, volatile organic compounds, and bacteria. Concentrations of most compounds were less than drinking-water standards established by the U.S. Environmental Protection Agency and New York State Department of Health; many of the organic analytes were not detected in any sample. Drinking-water standards that were exceeded at some sites include those for color, turbidity, pH, aluminum, arsenic, iron, manganese, radon-222, and bacteria. pH ranged from 5.6 to 8.3; the pH of nine samples was less than the U.S. Environmental Protection Agency secondary drinking-water standard range of 6.5 to 8.5. Water in the basin is generally soft to moderately hard (hardness 120 milligrams per liter as CaCO3 or less). The cation with the highest median concentration was calcium; the anion with the highest median concentrations was bicarbonate. Nitrate was the predominant nutrient detected but no sample exceeded the 10 mg/L U.S. Environmental Protection Agency maximum contaminant level. The trace elements detected with the highest median concentrations were strontium and iron in unfiltered water and strontium and barium in filtered water. Concentrations of trace elements in several samples exceeded U.S. Environmental Protection Agency secondary drinking-water standards, including aluminum (50-200 micrograms per liter, three wells), arsenic (10 micrograms per liter, one well), iron (300 micrograms per liter, three wells), and manganese (50 micrograms per liter, four wells). The median concentration of radon-222 was 1,580 picoCuries per liter. Radon-222 is not currently regulated, but the U.S. Environmental Protection Agency has proposed a maximum contaminant level of 300 picoCuries per liter along with an alternative maximum contaminant level of 4,000 picoCuries per liter, to be in effect in states that have programs to address radon in indoor air. Concentrations of radon-222 exceeded the proposed maximum contaminant level in all 19 of the samples and exceeded the proposed alternative maximum contaminant level in 1 sample. Eleven pesticides and pesticide degradates were detected in samples from ten wells; all were herbicides or herbicide degradates. Three volatile organic compounds were detected, including disinfection byproducts such as trichloromethane and gasoline components or additives such as methyl tert-butyl ether. No pesticides, pesticide degradates, or volatile organic compounds were detected above established limits. Coliform bacteria were detected in samples from five wells, four of which were finished in sand and gravel; Escherichia coli was not detected in any sample.

Open-File Report↗
USGS2003

Hydrologic Resources of Guam

Introduction The U.S. Territory of Guam, which lies in the western Pacific Ocean near latitude 13?28'N and longitude 144?45'E, is the largest (211 mi2) and southernmost of the islands in the Mariana chain. Ground water supplies about 80 percent of the drinking water for the island's 150,000 residents and nearly one million visitors per year. In northern Guam, water is obtained from wells that tap the upper part of a fresh ground-water lens in an aquifer composed mainly of limestone. About 180 wells, nearly all in the north, withdraw about 35 Mgal/d of water with chloride concentrations ranging from 6 to 585 mg/L. In southern Guam, the main source of freshwater is from surface water that runs off the weathered volcanic rocks that are exposed over much of the area. About 9.9 Mgal/d of freshwater is obtained using surface reservoirs. The island's freshwater resources are adequate to meet current (2003) needs, but future demands will eventually be higher. To better understand the hydrology of the island, the U.S. Geological Survey (USGS) entered into a cooperative study with the Water and Environmental Research Institute of the Western Pacific (WERI) at the University of Guam. The objective of the study was to provide a better understanding of the water resources of the island through analysis of data collected by the USGS on Guam. This report provides a description of the general hydrologic principles of the island's ground-water systems, as well as of the rainfall and geology of Guam. Hydrologic data described in the report include water levels, chloride concentrations, and pumpage from ground-water wells and streamflow data from southern Guam.

Water-Resources Investigations Report↗
USGS1993

Water Resources Data, Florida, Water Year 1992. Volume 2B. South Florida Ground Water

This volume of the annual hydrologic data report of Florida is one of a series of annual reports that document hydrologic data gathered from the U.S. Geological Survey's surface- and ground-water data-collection networks in each State, Puerto Rico, and the Trust Territories. These records of streamflow, ground-water levels, and quality of water provide the hydrologic information needed by State, local, and Federal agencies, and the private sector for developing and managing our Nation's land and water resources. Hydrologic data for Florida are contained in four volumes.

Florida↗
USGS1992

Ground-water-quality assessment of the central Oklahoma aquifer, Oklahoma: Hydrologic, water-quality, and quality-assurance data 1987-90

This report presents data collected from 202 wells between June 1987 and September 1990 as part of the Central Oklahoma aquifer pilot study of the National Water-Quality Assessment Program. The report describes the sampling networks, the sampling procedures, and the results of the ground-water quality and quality-assurance sample analyses. The data tables consist of information about the wells sampled and the results of the chemical analyses of ground water and quality-assurance sampling. Chemical analyses of ground-water samples in four sampling networks are presented: A geochemical network, a low-density survey bedrock network, a low-density survey alluvium and terrace deposits network, and a targeted urban network. The analyses generally included physical properties, major ions, nutrients, trace substances, radionuclides, and organic constituents. The chemical analyses of the ground-water samples are presented in five tables: (1) Physical properties and concentrations of major ions, nutrients, and trace substances; (2) concentrations of radionuclides and radioactivities; (3) carbon isotope ratios and delta values (d-values) of selected isotopes; (4) concentrations of organic constituents; and (5) organic constituents not reported in ground-water samples. The quality of the ground water sampled varied substantially. The sum of constituents (dissolved solids) concentrations ranged from 71 to 5,610 milligrams per liter, with 38 percent of the wells sampled exceeding the Secondary Maximum Contaminant Level of 500 milligrams per liter established under the Safe Drinking Water Act. Values of pH ranged from 5.7 to 9.2 units with 20 percent of the wells outside the Secondary Maximum Contaminant Level of 6.5 to 8.5 units. Nitrite plus nitrate concentrations ranged from less than 0.1 to 85 milligrams per liter with 8 percent of the wells exceeding the proposed Maximum Contaminant Level of 10 milligrams per liter. Concentrations of trace substances were highly variable, ranging from below the reporting level to concentrations over the Maximum Contaminant Levels for several constituents (arsenic, barium, cadmium, chromium, lead, and selenium). Radionuclide activities also were highly variable. Gross alpha radioactivity ranged from 0.1 to 210 picocuries per liter as 230thorium. Of the wells sampled, 20 percent exceeded the proposed Maximum Contaminant Level of 15 picocuries per liter for gross alpha radioactivity. Organic constituents were detected in 39 percent of the 170 wells sampled for organic constituents; in most cases concentrations were at or near the laboratory minimum reporting levels. Ten of the wells sampled for organic constituents had one or more constituents (chlordane, dieldrin, heptachlor epoxide, trichloroethylene, 1,1-dichloroethylene, 1,1,1-trichloroethane) at concentrations equal to or greater than the Maximum Contaminant Level or acceptable concentrations as suggested in the Environmental Protection Agency's Health Advisory Summaries. Quality-assurance sampling included duplicate samples, repeated samples, blanks, spikes, and blind samples. These samples proved to be essential in evaluating the accuracy of the data, particularly in the case of volatile organic constituents.

Oklahoma↗
USGS1984

Ground-water level data and preliminary potentiometric-surface maps, Yucca Mountain and vicinity, Nye County, Nevada

The report contains a table of ground-water level data and two preliminary potentiometric-surface maps for the Yucca Mountain area. The water-level surface shown on the maps generally represents water-table (unconfined) conditions. The water table in the Yucca Mountain area occurs in ash-flow and air-fall tuffs of tertiary age. West of the crest of Yucca Mountain, water-level altitudes are about 775 meters above sea level. Along the eastern edge and southern end of Yucca Mountain, the potentiometic surface generally is nearly flat, is about 728 to 730 meters above sea level, and has a southeastward slope. (USGS)

Water-Resources Investigations Report↗
USGS2001

MODFLOW-2000 : the U.S. Geological Survey modular ground-water model--documentation of the Advective-Transport Observation (ADV2) Package

Observations of the advective component of contaminant transport in steady-state flow fields can provide important information for the calibration of ground-water flow models. This report documents the Advective-Transport Observation (ADV2) Package, version 2, which allows advective-transport observations to be used in the three-dimensional ground-water flow parameter-estimation model MODFLOW-2000. The ADV2 Package is compatible with some of the features in the Layer-Property Flow and Hydrogeologic-Unit Flow Packages, but is not compatible with the Block-Centered Flow or Generalized Finite-Difference Packages. The particle-tracking routine used in the ADV2 Package duplicates the semi-analytical method of MODPATH, as shown in a sample problem. Particles can be tracked in a forward or backward direction, and effects such as retardation can be simulated through manipulation of the effective-porosity value used to calculate velocity. Particles can be discharged at cells that are considered to be weak sinks, in which the sink applied does not capture all the water flowing into the cell, using one of two criteria: (1) if there is any outflow to a boundary condition such as a well or surface-water feature, or (2) if the outflow exceeds a user specified fraction of the cell budget. Although effective porosity could be included as a parameter in the regression, this capability is not included in this package. The weighted sum-of-squares objective function, which is minimized in the Parameter-Estimation Process, was augmented to include the square of the weighted x-, y-, and z-components of the differences between the simulated and observed advective-front locations at defined times, thereby including the direction of travel as well as the overall travel distance in the calibration process. The sensitivities of the particle movement to the parameters needed to minimize the objective function are calculated for any particle location using the exact sensitivity-equation approach; the equations are derived by taking the partial derivatives of the semi-analytical particle-tracking equation with respect to the parameters. The ADV2 Package is verified by showing that parameter estimation using advective-transport observations produces the true parameter values in a small but complicated test case when exact observations are used. To demonstrate how the ADV2 Package can be used in practice, a field application is presented. In this application, the ADV2 Package is used first in the Sensitivity-Analysis mode of MODFLOW-2000 to calculate measures of the importance of advective-transport observations relative to head-dependent flow observations when either or both are used in conjunction with hydraulic-head observations in a simulation of the sewage-discharge plume at Cape Cod, Massachusetts. The ADV2 Package is then used in the Parameter-Estimation mode of MODFLOW-2000 to determine best-fit parameter values. It is concluded that, for this problem, advective-transport observations improved the calibration of the model and the estimation of ground-water flow parameters, and the use of formal parameter-estimation methods and related techniques produced significant insight into the physical system.

Open-File Report↗