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At least 631 records · Page 35Linked to original sources
USGS2005

Water-quality assessment of part of the Upper Mississippi River Basin, Minnesota and Wisconsin — Ground-water quality along a flow system in the Twin Cities metropolitan area, Minnesota, 1997-98

As part of a national analysis of the effects of land use on ground-water quality for the National Water-Quality Assessment Program, the U.S. Geological Survey sampled wells along a flow system in surficial glacial aquifers in the northwestern part of the Twin Cities metropolitan area during 1997 and 1998. In addition, a reconnaissance steady-state ground-water model was developed to estimate flowpaths and dates of ground-water recharge using a particle-tracking routine. Sediment samples collected during drilling had high horizontal hydraulic conductivities (ranging from about 3.1 to about 190 feet per day, based on sediment-size analysis of well cuttings), small organic carbon concentrations (ranging from less than 0.2 to 160 grams per kilogram), and pH values that were mostly alkaline (ranging from 4.9 to 8.2). Water samples were analyzed for physical properties, major ions, iron, manganese, nutrients, organic carbon, radon, pesticides, volatile organic compounds (VOCs), chlorofluorocarbons, tritium, and isotopes of nitrogen, hydrogen, and oxygen. Most of the water samples had small dissolved-oxygen concentrations (less than 1 milligram per liter). Calcium, magnesium, sodium, bicarbonate, sulfate, and chloride were the primary dissolved constituents in water samples. Nitrite plus nitrate as nitrogen (nitrate) concentrations were less than the U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Level of 10 mg/L. Nitrogen isotope ratios indicated that the sources of nitrate primarily were soils, animal waste, or denitrification that increased nitrogen isotope ratios in nitrate. Small concentrations of pesticides were detected in the shallow parts of the aquifer. The herbicide prometon was the most frequently detected pesticide. Herbicides applied to control grasses and weeds in corn (atrazine, simazine, and metolachlor) also were frequently detected in water samples. All pesticide and VOCs detected were below USEPA Maximum Contaminant Levels or Health Advisory Limits. Chlorofluorocarbon compounds and tritium concentrations were used to estimate dates of recharge of ground-water samples. In general, shallower ground-water samples were more recently recharged although most water sampled from the aquifer was recharged after 1955. Although land use had substantial effects on ground-water quality, the distribution of contaminants in the aquifer also is affected by complex combinations of factors and processes that include sources of natural and anthropogenic contaminants, three-dimensional advective flow, physical and hydrologic settings, age and evolution of ground water, and transformation of chemical compounds along the flow system. Compounds such as nitrate and dissolved oxygen were greatest in water samples from the upgradient end of the flow system and near the water table. Specific conductance and dissolved solids increased along the flow system and with depth due to increase in residence time in the flow system and dissolution of aquifer materials.

Minnesota↗
USGS2000

Hydrogeology and simulation of ground-water flow at the Gettysburg Elevator Plant Superfund Site, Adams County, Pennsylvania

Ground water in Triassic-age sedimentary fractured-rock aquifers in the area of Gettysburg, Pa., is used as drinking water and for industrial and commercial supply. In 1983, ground water at the Gettysburg Elevator Plant was found by the Pennsylvania Department of Environmental Resources to be contaminated with trichloroethene, 1,1,1-trichloroethane, and other synthetic organic compounds. As part of the U.S. Environmental Protection Agency?s Comprehensive Environmental Response, Compensation, and Liability Act, 1980 process, a Remedial Investigation was completed in July 1991, a method of site remediation was issued in the Record of Decision dated June 1992, and a Final Design Report was completed in May 1997. In cooperation with the U.S. Environmental Protection Agency in the hydrogeologic assessment of the site remediation, the U.S. Geological Survey began a study in 1997 to determine the effects of the onsite and offsite extraction wells on ground-water flow and contaminant migration from the Gettysburg Elevator Plant. This determination is based on hydrologic and geophysical data collected from 1991 to 1998 and on results of numerical model simulations of the local ground-water flow-system. The Gettysburg Elevator Site is underlain by red, green, gray, and black shales of the Heidlersburg Member of the Gettysburg Formation. Correlation of natural-gamma logs indicates the sedimentary rock strike about N. 23 degrees E. and dip about 23 degrees NW. Depth to bedrock onsite commonly is about 6 feet but offsite may be as deep as 40 feet. The ground-water system consists of two zones?a thin, shallow zone composed of soil, clay, and highly weathered bedrock and a thicker, nonweathered or fractured bedrock zone. The shallow zone overlies the bedrock zone and truncates the dipping beds parallel to land surface. Diabase dikes are barriers to ground-water flow in the bedrock zone. The ground-water system is generally confined or semi-confined, even at shallow depths. Depth to water can range from flowing at land surface to more than 71 feet below land surface. Potentiometric maps based on measured water levels at the Gettysburg Elevator Plant indicate ground water flows from west to east, towards Rock Creek. Multiple-well aquifer tests indicate the system is heterogeneous and flow is primarily in dipping beds that contain discrete secondary openings separated by less permeable beds. Water levels in wells open to the pumped bed, as projected along the dipping stratigraphy, are drawn down more than water levels in wells not open to the pumped bed. Ground-water flow was simulated for steady-state conditions prior to pumping and long-term average pumping conditions. The three-dimensional numerical flow model (MODFLOW) was calibrated by use of a parameter estimation program (MODFLOWP). Steady-state conditions were assumed for the calibration period of 1996. An effective areal recharge rate of 7 inches was used in model calibration. The calibrated flow model was used to evaluate the effectiveness of the current onsite and offsite extraction well system. The simulation results generally indicate that the extraction system effectively captures much of the ground-water recharge at the Gettysburg Elevator Plant and, hence, contaminated ground-water migrating from the site. Some of the extraction wells pump at low rates and have very small contributing areas. Results indicate some areal recharge onsite will move to offsite extraction wells.

Pennsylvania↗
USGS1980

Ground water in the Thousand Oaks area, Ventura County, California

The ground-water basin beneath the city of Thousand Oaks, Calif. , corresponds closely in area with the surface-water drainage basin of Conejo Valley. Before World War II there was little ground-water development. After World War II, urban development put a stress on the ground-water basin; many wells were drilled and water levels in wells were drawn down as much as 300 feet in places. Beginning in 1963, imported water replaced domestic and municipal ground-water systems, and water levels rapidly recovered to predevelopment levels or nearly so. Most of the ground water in the Thousand Oaks area is stored in fractured basalt of the middle Miocene Conejo Volcanics. Depending on the degree of occurrence of open fractures and cavities in the basalt, recoverable ground water in the upper 300 to 500 feet of aquifer is estimated to be between 400,000 and 600,000 acre-feet. The yield of water from wells in the area ranges from 17 to 1,080 gallons per minute. Most of the ground-water in the eastern part of the valley is high insulfate and has a dissolved-solids concentration greater than 1,000 milligrams per liter. In the western part of the valley the ground-water is mostly of a bicarbonate type, and the dissolved-solids concentration is less than 800 milligrams per liter. In most areas of Conejo Valley, ground-water is a viable resource for irrigation of public lands and recreation areas. (USGS)

California↗
USGS2005

Problems associated with estimating ground water discharge and recharge from stream-discharge records

Ground water discharge and recharge frequently have been estimated with hydrograph-separation techniques, but the critical assumptions of the techniques have not been investigated. The critical assumptions are that the hydraulic characteristics of the contributing aquifer (recession index) can be estimated from stream-discharge records; that periods of exclusively ground water discharge can be reliably identified; and that stream-discharge peaks approximate the magnitude and tinting of recharge events. The first assumption was tested by estimating the recession index from st earn-discharge hydrographs, ground water hydrographs, and hydraulic diffusivity estimates from aquifer tests in basins throughout the eastern United States and Montana. The recession index frequently could not be estimated reliably from stream-discharge records alone because many of the estimates of the recession index were greater than 1000 days. The ratio of stream discharge during baseflow periods was two to 36 times greater than the maximum expected range of ground water discharge at 12 of the 13 field sites. The identification of the ground water component of stream-discharge records was ambiguous because drainage from bank-storage, wetlands, surface water bodies, soils, and snowpacks frequently exceeded ground water discharge and also decreased exponentially during recession periods. The timing and magnitude of recharge events could not be ascertained from stream-discharge records at any of the sites investigated because recharge events were not directly correlated with stream peaks. When used alone, the recession-curve-displacement method and other hydrograph-separation techniques are poor tools for estimating ground water discharge or recharge because the major assumptions of the methods are commonly and grossly violated. Multiple, alternative methods of estimating ground water discharge and recharge should be used because of the uncertainty associated with any one technique.

Ground Water↗
USGS2007

An Online Interactive Map Service for Displaying Ground-Water Conditions in Arizona

Monitoring the availability of the nation's ground-water supplies is of critical importance to planners and water managers. The general public also has an interest in understanding the status of ground-water conditions, especially in the semi-arid Southwestern United States where much of the water used by municipalities and agriculture comes from the subsurface. Unlike surface-water indicators such as stage or discharge, ground-water conditions may be more difficult to assess and present. Individual well observations may only represent conditions in a limited area surrounding the well and wells may be screened over single or multiple aquifers, further complicating single-well measurement interpretations. Additionally, changes in ground-water conditions may involve time scales ranging from days to many years, depending on recharge, soil properties and depth to the water table. This lack of an easily identifiable ground-water property indicative of current conditions combined with differing time scales of water-level changes makes the presentation of ground-water conditions a difficult task, particularly on a regional basis. One approach is to spatially present several indicators of ground-water conditions that address different time scales and attributes of the aquifer systems. In this report, we describe a publicly-available online interactive map service that presents several different layers of ground-water-conditions information for the alluvial basins in the Lower Colorado River Basin in Arizona (http://montezuma.wr.usgs.gov/website/azgwconditions/). These data layers include wells experiencing water-level decline, wells experiencing water-level rise, recent trends in ground-water levels, change in water level since predevelopment and change in storage since predevelopment. Recent pumpage totals and projected population numbers are also provided for ground-water basins and counties in the region of the Lower Colorado River in Arizona along with a bibliography of U.S. Geological Survey reports for those seeking further information. The methods used to create these data layers are explained with illustrations of example information available on the Web site.

Open-File Report↗
USGS1999

Deep Aquifer Remediation Tools (DARTs): A new technology for ground-water remediation

P otable ground-water supplies throughout the world are contaminated or threatened by advancing plumes containing radionuclides, metals, and organic compounds. Currently (1999), the most widely used method of ground-water remediation is a combination of extraction, ex-situ treatment, and discharge of the treated water, commonly known as pump and treat. Pump-and-treat methods are costly and often ineffective in meeting long-term protection standards (Travis and Doty, 1990; Gillham and Burris, 1992; National Research Council, 1994). This fact sheet describes a new and potentially cost-effective technology for removal of organic and inorganic contaminants from ground water. The U.S. Geological Survey (USGS) is currently exploring the possibilities of obtaining a U.S. Patent for this technology.

Fact Sheet↗
USGS2003

Arsenic in ground water: Geochemistry and occurrence

Interest in arsenic in ground water has greatly increased in the past decade because of the increased awareness of human health effects and the costs of avoidance or treatment of ground water supplies used for consumption. The goal of this book is to provide a description of the basic processes that affect arsenic occurrence and transport by providing sufficient background information on arsenic geochemistry and descriptions of hi- arsenic ground water, both affected and unaffected by human activity. An understanding of thermodynamics, adsorption, and the speciation of arsenic in solid phases, which are described in first three chapters, is needed to predict the fate of arsenic in ground water systems. Large-scale and deep movement of ground water can and has redistributed arsenic in the near surface environment, as described in the next two chapters. These large-scale systems can affect large volumes of both ground water and surface water, such as in the Yellowstone system, and can produce mineralised zones that subsequently release arsenic to ground water supplies. Regional identification of high-arsenic ground water and its consumption as described in the next three chapters clearly demonstrates a need for increased wat- quality monitoring, particularly in south and southeast Asia. Chapters 9-11 provide examples of high arsenic ground water associated with sulfide mineral oxidation and alkaline conditions. Finally, smaller scale studies of the effects of human activities that have produced high-arsenic ground water and methods for attenuation of ground water are presented

Book↗
USGS1996

Age of ground water in basalt aquifers near Spring Creek National Fish Hatchery, Skamania County, Washington

Water samples from four springs and five wells in basalt aquifers near Spring Creek National Fish Hatchery in Skamania County, Washington, were collected and analyzed for selected inorganic ions and stable isotopes. Eight samples were analyzed for carbon-14 (14C), carbon-13 ([3C), and either chlorofluorocarbons (CFCs) or tritium. This work was done to estimate the age (residence time, or time elapsed since recharge) of water issuing from springs at the hatchery. If CFCs are present in ground water, the presence of at least a component of modem (post- 1944) water is indicated. CFC-dating suggests that ground water several hundred feet below land surface in the Underwood Heights area noah of the hatchery, including ground water discharging from the hatchery springs, contains modem water. In contrast, CFC-dating suggests that deeper ground water such as that withdrawn from the Hatchery Well may contain little or no modem water. Concentrations of 14C in water can yield 14C-based ground-water ages, termed 14C-model ages. Unadjusted 14C-model ages (14C-model ages unadjusted for carbon mass transfers) for water discharging from the hatchery springs are on the order of several hundred years. Ground-water samples from three wells in the Underwood Heights area yielded 14C-model ages ranging from modem to several hundred years. Unadjusted 14C-model ages for deep ground water pumped by the Hatchery Well indicate an overall age of several thousand years. However, 14C concentrations may be affected by transfers of carbon into and out of solution. The 13C values of the downgradient ground waters ranged from - 16.4 (per mil) to -18.2 per rail, isotopically heavier than expected for ground water that obtains carbon solely from root respiration in a temperate climate and undergoes no subsequent carbon-isotope fractionation or exchange. Such 13C values in the ground water near the hatchery suggest the possibility of carbon mass transfers during the evolution of these waters. Geochemical mass-transfer modeling suggests that carbon dioxide may degas and calcite may dissolve during the evolution of the modeled ground waters, but that degassing of carbon dioxide is the dominant carbon mass transfer in these ground waters. In addition, modeling results also suggest that, although some calcite may dissolve during the evolution of the water produced by the Hatchery Well, and possibly during the evolution of the shallower ground waters, the amount of calcite dissolution is small. Model testing suggests that the quantity of 14C-dead carbon added from calcite dissolution may not be sufficient to greatly affect the 14C-model ages of these ground waters. In other words, the 14C-model ages that were adjusted for various modeled carbon mass transfers are similar to the unadjusted 14C-model ages. A comparison of CFC data with both adjusted and unadjusted 14C data suggests that water discharging at the hatchery springs contains a mixture of modem and old water, where old water is defined as water recharged prior to 1944. The CFC data support a component of modem water, whereas the 14C data suggest a component of old water. Similar results were obtained from a comparison of CFC data with adjusted and unadjusted 14C data for water collected from Well 3. Well 3 is north of the hatchery springs, on a flow path that appears to be parallel to and similar in length to the flow path leading to the hatchery springs. Water from the Hatchery Well, however, may be devoid of modem water and appears to have an overall age on the order of thousands of years.

Washington↗
USGS2004

Simulation of regional ground-water flow in the Upper Deschutes Basin, Oregon

This report describes a numerical model that simulates regional ground-water flow in the upper Deschutes Basin of central Oregon. Ground water and surface water are intimately connected in the upper Deschutes Basin and most of the flow of the Deschutes River is supplied by ground water. Because of this connection, ground-water pumping and reduction of artificial recharge by lining leaking irrigation canals can reduce the amount of ground water discharging to streams and, consequently, streamflow. The model described in this report is intended to help water-management agencies and the public evaluate how the regional ground-water system and streamflow will respond to ground-water pumping, canal lining, drought, and other stresses. Ground-water flow is simulated in the model by the finite-difference method using MODFLOW and MODFLOWP. The finite-difference grid consists of 8 layers, 127 rows, and 87 columns. All major streams and most principal tributaries in the upper Deschutes Basin are included. Ground-water recharge from precipitation was estimated using a daily water-balance approach. Artificial recharge from leaking irrigation canals and on-farm losses was estimated from diversion and delivery records, seepage studies, and crop data. Ground-water pumpage for irrigation and public water supplies, and evapotranspiration are also included in the model. The model was calibrated to mean annual (1993-95) steady-state conditions using parameter-estimation techniques employing nonlinear regression. Fourteen hydraulic-conductivity parameters and two vertical conductance parameters were determined using nonlinear regression. Final parameter values are all within expected ranges. The general shape and slope of the simulated water-table surface and overall hydraulic-head distribution match the geometry determined from field measurements. The fitted standard deviation for hydraulic head is about 76 feet. The general magnitude and distribution of ground-water discharge to streams is also well simulated throughout the model. Ground-water discharge to streams in the area of the confluence of the Deschutes, Crooked, and Metolius Rivers is closely matched. The model was also calibrated to transient conditions from 1978 to 1997 using traditional trial-and-error methods. Climatic cycles during this period provided an excellent regional hydrologic signal for calibration. Climate-driven water-level fluctuations are simulated with reasonable accuracy over most of the model area. The timing and magnitude of simulated water-level fluctuations caused by annual pulses of recharge from precipitation match those observed reasonably well, given the limitations of the time discretization in the model. Water-level fluctuations caused by annual canal leakage are simulated very well over most of the area where such fluctuations occur. The transient model also simulates the volumetric distribution and temporal variations in ground-water discharge reasonably well. The match between simulated and measured volume of and variations in ground-water discharge is, however, somewhat dependent on geographic scale. The rates of and variations in ground-water discharge are matched best at regional scales. Example simulations were made to demonstrate the utility of the model for evaluating the effects of ground-water pumping or canal lining. Pumping simulations show that pumped water comes largely from aquifer storage when pumping begins, but as the water table stabilizes, the pumping increasingly diminishes the discharge to streams and, hence, streamflow. The time it takes for pumping to affect streamflow varies spatially depending, in general, on the location of pumping relative to the discharge areas. Canal-lining simulations show similar effects.

Water-Resources Investigations Report↗
USGS2005

Influence of fracture anisotropy on ground water ages and chemistry, Valley and Ridge province, Pennsylvania

Model ground water ages based on chlorofluorocarbons (CFCs) and tritium/helium-3 (3H/3He) data were obtained from two arrays of nested piezometers located on the north limb of an anticline in fractured sedimentary rocks in the Valley and Ridge geologic province of Pennsylvania. The fracture geometry of the gently east plunging fold is very regular and consists predominately of south dipping to subhorizontal to north dipping bedding-plane parting and east striking, steeply dipping axial-plane spaced cleavage. In the area of the piezometer arrays, which trend north-south on the north limb of the fold, north dipping bedding-plane parting is a more dominant fracture set than is steeply south dipping axial-plane cleavage. The dating of ground water from the piezometer arrays reveals that ground water traveling along paths parallel to the dip direction of bedding-plane parting has younger 3H/3He and CFC model ages, or a greater component of young water, than does ground water traveling along paths opposite to the dip direction. In predominantly unmixed samples there is a strong positive correlation between age of the young fraction of water and dissolved sodium concentration. The travel times inferred from the model ages are significantly longer than those previously calculated by a ground water flow model, which assumed isotropically fractured layers parallel to topography. A revised model factors in the directional anisotropy to produce longer travel times. Ground water travel times in the watershed therefore appear to be more influenced by anisotropic fracture geometry than previously realized. This could have significant implications for ground water models in other areas underlain by similarly tilted or folded sedimentary rock, such as elsewhere in the Valley and Ridge or the early Mesozoic basins.

Pennsylvania↗
USGS2006

An update of the distribution of selected radiochemical and chemical constituents in perched ground water, Idaho National Laboratory, Idaho, Emphasis 1999-2001

Radiochemical and chemical wastes generated at facilities at the Idaho National Laboratory (INL) were discharged since 1952 to infiltration ponds at the Reactor Technology Complex (RTC) (known as the Test Reactor Area [TRA] until 2005), and the Idaho Nuclear Technology and Engineering Center (INTEC) and buried at the Radioactive Waste Management Complex (RWMC). Disposal of wastewater to infiltration ponds and infiltration of surface water at waste burial sites resulted in formation of perched ground water in basalts and in sedimentary interbeds above the Snake River Plain aquifer. Perched ground water is an integral part of the pathway for waste-constituent migration to the aquifer. The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, maintains ground-water monitoring networks at the INL to determine hydrologic trends, and to monitor the movement of radiochemical and chemical constituents in wastewater discharged from facilities to both perched ground water and the aquifer. This report presents an analysis of water-quality and water-level data collected from wells completed in perched ground water at the INL during 1999-2001, and summarizes historical disposal data and water-level-and water-quality trends. At the RTC, tritium, strontium-90, cesium-137, dissolved chromium, chloride, sodium, and sulfate were monitored in shallow and deep perched ground water. In shallow perched ground water, no tritium was detected above the reporting level. In deep perched ground water, tritium concentrations generally decreased or varied randomly during 1999-2001. During October 2001, tritium concentrations ranged from less than the reporting level to 39.4?1.4 picocuries per milliliter (pCi/mL). Reportable concentrations of tritium during July-October 2001 were smaller than the reported concentrations measured during July-December 1998. Tritium concentrations in water from wells at the RTC were likely affected by: well's distance from the radioactive-waste infiltration ponds (commonly referred to as the warm-waste ponds); water depth below the ponds; the amount of tritium discharged to radioactive-waste infiltration ponds in the past; discontinued use of radioactive-waste infiltration ponds; radioactive decay; and dilution from disposal of nonradioactive water. During 1999-2001, the strontium-90 concentrations in two wells completed in shallow perched water near the RTC exceeded the reporting level. Strontium-90 concentrations in water from wells completed in deep perched ground water at the RTC varied randomly with time. During October 2001, concentrations in water from five wells exceeded the reporting level and ranged from 2.8?0.7 picocuries per liter (pCi/L) in well USGS 63 to 83.8?2.1 pCi/L in well USGS 54. No reportable concentrations of cesium-137, chromium-51, or cobalt-60 were present in water samples from any of the shallow or deep wells at the RTC during 1999-2001. Dissolved chromium was not detected in shallow perched ground water at the RTC during 1999-2001. Concentrations of dissolved chromium during July-October 2001 in deep perched ground water near the RTC ranged from 10 micrograms per liter (?g/L) in well USGS 61 to 82 ?g/L in well USGS 55. The largest concentrations were in water from wells north and west of the radioactive-waste infiltration ponds. During July-October 2001, dissolved sodium concentrations ranged from 7 milligrams per liter (mg/L) in well USGS 78 to 20 mg/L in all wells except well USGS 68 (413 mg/L). Dissolved chloride concentrations in shallow perched ground water ranged from 10 mg/L in wells CWP 1, 3, and 4 to 53 mg/L in well TRA A 13 during 1999-2001. Dissolved chloride concentrations in deep perched ground water ranged from 5 mg/L in well USGS 78 to 91 mg/L in well USGS 73. The maximum dissolved sulfate concentration in shallow perched ground water was 419 mg/L in well CWP 1 during July 2000. Concentrations of dissolved sulfate in water from wells USGS 54, 60

Scientific Investigations Report↗
USGS1998

Radon-222 in the ground water of Chester County, Pennsylvania

Radon-222 concentrations in ground water in 31 geologic units in Chester County, Pa., were measured in 665 samples collected from 534 wells from 1986 to 1997. Chester County is underlain by schists, gneisses, quartzites, carbonates, sandstones, shales, and other rocks of the Piedmont Physiographic Province. On average, radon concentration was measured in water from one well per 1.4 square miles, throughout the 759 square-mile county, although the distribution of wells was not even areally or among geologic units. The median concentration of radon-222 in ground water from the 534 wells was 1,400 pCi/L (picocuries per liter). About 89 percent of the wells sampled contained radon-222 at concentrations greater than 300 pCi/L, and about 11 percent of the wells sampled contained radon-222 at concentrations greater than 5,000 pCi/L. The highest concentration measured was 53,000 pCi/L. Of the geologic units sampled, the median radon-222 concentration in ground water was greatest (4,400 pCi/L) in the Peters Creek Schist, the second most areally extensive formation in the county. Significant differences in the radon-222 concentrations in ground water among geologic units were observed. Generally, concentrations in ground water in schists, quartzites, and gneisses were greater than in ground water in anorthosite, carbonates, and ultramafic rocks. The distribution of radon-222 in ground water is related to the distribution of uranium in aquifer materials of the various rock types. Temporal variability in radon-222 concentrations in ground water does not appear to be greater than about a factor of two for most (75 percent) of wells sampled more than once but was observed to range up to almost a factor of three in water from one well. In water samples from this well, seasonal variations were observed; the maximum concentrations were measured in the fall and the minimum in the spring.

Pennsylvania↗
USGS2004

Quality of ground water for selected municipal water supplies in Iowa, 1997–2002 water years

The Iowa ground-water-quality monitoring program has been conducted cooperatively since 1982 by the Iowa Department of Natural Resources, Iowa Geological Survey; the University of Iowa Hygienic Laboratory; and the U.S. Geological Survey. The original objectives of the program were to provide baseline ground-water-quality data throughout the State for the major aquifers and to address any new areas of water-quality concern. Since the program began, the emphasis and objectives of the program have changed several times. As of 1992, greater emphasis has been placed on determining trends in ground-water quality and correlating water quality with possible contributing factors such as location, land use, aquifer, aquifer depth, and precipitation. From 1997 through 2002, a total of 471 samples of untreated water have been collected from 154 municipal wells throughout Iowa. The samples, collected from six different aquifers, consisted of 192 alluvial aquifer samples (36 wells), 79 Pleistocene aquifer samples (16 wells), 52 Cretaceous aquifer samples (35 wells), 48 Carboniferous aquifer samples (30 wells), 54 Silurian-Devonian aquifer samples (19 wells), and 46 Cambrian-Ordovician aquifer samples (18 wells). Some samples had concentrations greater than or equal to the respective Maximum Contaminant Levels for drinking water established by the U.S. Environmental Protection Agency. Of 471 samples analyzed, 19 samples had concentrations greater than or equal to the Maximum Contaminant Level for sulfate; 31 samples had concentrations greater than or equal to the Maximum Contaminant Level for nitrite plus nitrate; 257 samples had concentrations greater than or equal to the Secondary Maximum Contaminant Level for iron; and 249 samples had concentrations greater than or equal to the Secondary Maximum Contaminant Level for manganese. Of the 443 samples analyzed for pesticides, 87 samples had concentrations greater than or equal to the respective minimum reporting levels for the parent compounds, 30 samples had concentrations greater than or equal to the respective minimum reporting levels for pesticide metabolites, and 26 samples had detectable concentrations (censored values) less than the minimum reporting levels. Concentrations of alachlor, atrazine, cyanazine, and metolachlor accounted for about 90 percent of the samples equal to or exceeding the respective minimum reporting levels for pesticides. No samples had pesticide concentrations greater than the respective Maximum Contaminant or Health Advisory Levels. The compact disc included with this report has information about water-quality properties and concentrations of dissolved solids, major ions, nutrients, trace elements, radionuclides, total organic carbon, pesticides, and synthetic organic compounds for water years 1997 through 2002.

Iowa↗
USGS2004

Simulation of the ground-water-flow system in the Kalamazoo County area, Michigan

A ground-water-flow model was developed to investigate the ground-water resources of Kalamazoo County. Ground water is widely used as a source of water for drinking and industry in Kalamazoo County and the surrounding area. Additionally, lakes and streams are valued for their recreational and aesthetic uses. Stresses on the ground-water system, both natural and human-induced, have raised concerns about the long-term availability of ground water for people to use and for replenishment of lakes and streams. Potential changes in these stresses, including withdrawals and recharge, were simulated using a ground-water-flow model. Simulations included steady-state conditions (in which stresses remained constant and changes in storage were not included) and transient conditions (in which stresses changed in seasonal and monthly time scales and storage within the system was included). Steady-state simulations were used to investigate the long-term effects on water levels and streamflow of a reduction in recharge or an increase in pumping to projected 2010 withdrawal rates, withdrawal and application of water for irrigation, and a reduction in recharge in urban areas caused by impervious surfaces. Transient simulations were used to investigate changes in withdrawals to match seasonal and monthly patterns under various recharge conditions, and the potential effects of the use of water for irrigation over the summer months. With a reduction in recharge, simulated water levels declined over most of the model area in Kalamazoo County; with an increase in pumping, water levels declined primarily near pumping centers. Because withdrawals by wells intercept water that would have discharged possibly to a stream or lake, model simulations indicated that streamflow was reduced with increased withdrawals. With withdrawal and consumption of water for irrigation, simulated water levels declined. Assuming a reduction in recharge due to urbanization, water levels declined and flow to streams was reduced based on steady-state simulation results. Transient results indicated a reduction of water levels with the simulated use of water for irrigation over the summer months. Generally the transient simulation with recharge only in the winter provided the best fit to observed water levels collected during synoptic water-level measurements in some wells and to the trends observed in water levels for other wells. Analysis of the regional hydrologic budgets provides an increased understanding of water movement within the ground-water-flow system in Kalamazoo County. Budgets for the steady-state simulations indicated that with reduced recharge, less water was available for streamflow and less water left the model area through the model boundaries. Similarly, with an increase in pumping rates, less water was available to enter streams and become streamflow. When recharge was assumed to remain constant and when it was allowed to vary throughout the year, the amount of water that entered storage was greater than that which left storage. However, when recharge was distributed through October?May only or when recharge rates were reduced from October to May, the amount of water that entered storage was less than that which left storage. Thus, on the basis of model simulations, with reduced recharge or increased withdrawals, water must come from storage, rivers, or from ground-flow-system boundaries to meet withdrawal demands.

Michigan↗
USGS1995

Quantity and quality of ground-water discharge to the South Platte River, Denver to Fort Lupton, Colorado, August 1992 through July 1993

Water-quality studies conducted by the Metro Wastewater Reclamation District have indicated that during low flow in segments of the South Platte River between Denver and Fort Lupton, concentrations of dissolved oxygen are less than minimum concen- trations set by the State of Colorado. Low dissolved-oxygen concentrations are observed in two reaches of the river-they are about 3.3 to 6.4 miles and 17 to 25 miles downstream from the Metro Waste- water Reclamation District effluent outfalls. Concentrations of dissolved oxygen recover between these two reaches. Studies conducted by the U.S. Geological Survey have indicated that ground-water discharge to the river may contribute to these low dissolved-oxygen concentrations. As a result, an assessment was made of the quantity and quality of ground-water discharge to the South Platte River from Denver to Fort Lupton. Measurements of surface- water and ground-water discharge and collections of surface water and ground water for water-quality analyses were made from August 1992 through January 1993 and in May and July 1993. The quantity of ground-water discharge to the South Platte River was determined indirectly by mass balance of surface-water inflows and outflows and directly by instantaneous measurements of ground-water discharge across the sediment/water interface in the river channel. The quality of surface water and ground water was determined by sampling and analysis of water from the river and monitoring wells screened in the alluvial aquifer adjacent to the river and by sampling and analysis of water from piezometers screened in sediments underlying the river channel. The ground-water flow system was subdivided into a large-area and a small-area flow system. The precise boundaries of the two flow systems are not known. However, the large-area flow system is considered to incorporate all alluvial sediments in hydrologic connection with the South Platte River. The small- area flow system is considered to incorporate the alluvial aquifer in the vicinity of the river. Flow-path lengths in the large-area flow system were considered to be on the order of hundreds of feet to more than a mile, whereas in the small-area flow system, they were considered to be on the order of feet to hundreds of feet. Mass-balance estimates of incremental ground-water discharge from the large- area flow system ranged from -27 to 17 cubic feet per second per mile in three reaches of the river; the median rate was 4.6 cubic feet per second per mile. The median percentage of surface-water discharge derived from ground-water discharge in the river reaches studied was 13 percent. Instantaneous measurements of ground-water discharge from the small-area flow system ranged from -1,360 to 1,000 cubic feet per second per mile, with a median value of -5.8 cubic feet per second per mile. Hourly measurements of discharge from the small-area flow system indicated that the high rates of discharge were transient and may have been caused by daily fluctuations in river stage due to changing effluent-discharge rates from the Metro Wastewater Reclamation District treatment plant. Higher river stages caused surface water to infiltrate bed sediments underlying the river channel, and lower river stages allowed ground water to discharge into the river. Although stage changes apparently cycled large quantities of water in and out of the small- area flow system, the process probably provided no net gain or loss of water to the river. In general, mass balance and instantaneous measurements of ground-water discharge indicated that the ground- water flow system in the vicinity of the river consisted of a large-area flow system that provided a net addition of water to the river and a small- area flow system that cycled water in and out of the riverbed sediments, but provided no net addition of water to the river. The small-area flow system was superimposed on the large-area flow system. The median values of pH and dissolved oxygen

Water-Resources Investigations Report↗
USGS1974

Availability of ground water in the lower Pawcatuck River basin, Rhode Island

The lower Pawcatuck River basin in southwestern Rhode Island is an area of about 169 square miles underlain by crystalline bedrock over which lies a relatively thin mantle of glacial till and stratified drift. Stratified drift, consisting dominantly of sand and gravel, occurs in irregularly shaped linear deposits that are generally less than a mile wide and less than 125 feet thick; these deposits are found along the Pawcatuck River, its tributaries, and abandoned preglacial channels. Deposits of stratified sand and gravel constitute the principal aquifer in the lower Pawcatuck basin and the only one capable of sustaining yields of 100 gallons per minute or more to individual wells. Water available for development in this aquifer consists of water in storage--potential ground-water runoff to streams--plus infiltration that can be induced from streams. Minimum annual ground-water runoff from the sand and gravel aquifer is calculated to be at least 1.17 cubic feet per second per square mile, or 0.76 million gallons per day per square mile. Potential recharge by induced infiltration is estimated to range from about 250 to 600 gallons per day per linear foot of streambed for the principal streams. In most areas, induced infiltration from streams constitutes the major source of water potentially available for development by wells. Because subsurface hydraulic connection in the sand and gravel aquifer is poor in several places, the deposits are conveniently divisible into several ground-water reservoirs. The potential yield from five of the most promising ground-water reservoirs is evaluated by means of mathematical models. Results indicate that continuous withdrawals ranging from 1.3 to 10.3 million gallons per day, and totaling 31 million gallons per day, are obtainable from these reservoirs. Larger yields may be recovered by different well placement, spacing, construction and development, pumping practice, and so forth. Withdrawals at the rates indicated will reduce streamflow downstream from pumping centers but generally will not result in streams going dry, provided the water is returned to the basin. Export of water from the basin will require careful consideration of the effects of such withdrawals on low streamflow. Export from the Pawcatuck basin of 27 million gallons per day, estimated to be available from ground-water reservoirs in the upper Pawcatuck basin, in addition to 37.5 million gallons per day available in the lower Pawcatuck basin, will markedly reduce low streamflow. The 90-percent duration flow of the Pawcatuck River at Westerly would be reduced from 75 million gallons per day to perhaps as little as 21 million gallons per day. The chemical quality of water from both the sand and gravel aquifer and associated streams is suitable for most purposes. The water is soft, slightly acidic, and typically has a dissolved-solids content of less than 75 milligrams per liter. Some treatment may be required locally for removal of iron and manganese to meet recommended standards of the U.S. Public Health Service for drinking water.

Rhode Island↗
USGS1995

Radium and radon in ground water in the Chickies Quartzite, southeastern Pennsylvania

The Chickies Quartzite, a Lower Cambrian-age formation compromised of quartzite and slate overlying a basal conglomerate, forms a narrow ridges and crops out discontinuously over 112 square miles in the Piedmont physiographic province of southeastern Pennsylvania. The formation is a low-yielding, fractured- rock, water-table aquifer recharged primarily by local precipitation. It is the sole source of water supply for thousands of domestic users. Ground water in the Chickies Quartzite generally is soft and acidic. During 1986-88, the U.S. Geological Survey sampled water from 160 wells that penetrate the Chickies Quartzite to determine the magnitude and distribution of radium-226 (Ra-226), radium-228 (Ra-228), and radon-222 (Rn-222) activities in ground water in the formation and to characterize the geochemical environmental associated with elevated activities of radium (Ra). In addition, 28 wells penetrating adjacent geologic units and 1 well in the Hardyston Quartzite were sampled to determine relative background Ra and RN-222 activities in ground water. Analyses included determination of activities of dissolved Ra-226, Ra-228, and RN-222, and concentrations of dissolved uranium (U), dissolved organic carbon (DOC), and major and minor dissolved inorganic ions. Rock samples were analyzed for U and thorium (Th) and geophysical logs were run to determine sources of Ra and RN-222 in the Chickies Quartzite. Activities of up to 41 pCi/L (picocuries per liter) for Ra-226, 160 pCi/L for Ra-228, and 32,300 pCi/L for RN-222 were measured in ground water in the Chickies Quartzite. Forty-seven percent of the samples contained Ra-226 and Ra-228 activities greater than 5 pCi/L. Median activities measured were 1.2 pCi/L for Ra-226, 2.6 pCi/L for Ra-228, 4.2 pCi/L for combined Ra-226 and Ra-228, and 2,400 pCi/L for RN-222 Ra-228 activity exceeded Ra-226 activity in about 92 percent of 100 water samples; the median Ra-228/Ra226 activity ratio was 2.4. Ra-228/Ra-226 activity ratios commonly were greater in ground water than calculated Th/U ratios in rock samples, suggesting perferential leaching of Ra-228 from aquifer solids. Of ground water in the adjacent geologic units, the highest activities (up to 2.9 pCi/L for Ra-226, 12 pCi/L for Ra-228, and 25,300 pCi/L for RN-222) were measured in ground water in the Harpers Phyllite and Antietam Quartzite. Nonparametric (Spearman rho test) statistical correlations show that the activity of dissolved Ra is inversely related to pH and directly related to concentrations of total dissolved solids, DOC, barium, and sulfate. Low pH decreases absorption of Ra onto the aquifer matrix. The other factors may favor Ra mobility by enhancing complexation or increasing solubility. RN-222 activity does not correlate with and is not supported by the activity of its parent, Ra-226, in solution. Ra-226 activity correlates positively, but weakly, with U concentrations. Ra-226 does not appear to be supported by its parent, U-238, in solution. Observed distributions of Ra-228, Ra-226, and RN-222 activities in ground water in different lithologies of the Chickies Quartzite reflect different geochemical controls on absorption and distribution of parent thorium-232 (Th-232) and uranium-238 (U-238) in the formation. Radium activities were greatest in acidic ground water in the conglomerate and quartzite (median pH of 5.0 and 5.2, respectively) and least in the more neutral water in the slate (median pH of 6.4). For ground water in the conglomerate, quartzite, and slate, respectively, median activities measured were 1.3, 1.5, and .02 pCi/L for Ra-226; and 3.7, 2.5, and 1.0 pCi/L for Ra-228. Natural-gamma-ray geophysical logs and results of rock analyses indicate that the conglomerate may contain more Th and U than the quartzite and that the conglomerate may be more enriched in Th with respect to U than the quartzite; Th and U distribution in both lithogies is variable. Median RN-222 activities in gro

Water-Resources Investigations Report↗