Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Ground Water”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,513 records · Page 84Linked to original sources
USGS1995

Simulated ground-water flow and sources of water in the Killbuck Creek Valley near Wooster, Wayne County, Ohio

The stratified-drift aquifer in the 3,000-ft (feet)-wide and 100-ft-deep buried valley of Killbuck Creek near Wooster in northeastern Ohio was studied. The stratified drift with adjacent sandstone and shale bedrock produce a system of ground-water flow representative of the western part of the glaciated north-eastern United States. The stratified-drift aquifer is an excellent source of water for municipal and industrial wells. The aquifer is recharged locally by water from precipitation on the valley floor and uplands, by infiltration from streams, and by lateral flow to the valley from the uplands. As a result, the aquifer is vulnerable to surface or subsurface spills of contaminants in the valley or the adjacent uplands. Quality of water in the stratified drift is affected by influx of water from bedrock lateral to or beneath the valley. This influx is controlled, in part, by the pumping stress placed on the stratified-drift aquifer. Hydrogeologic and aqueous-geochemical data were analyzed to establish the framework necessary for stead-state and transient simulations of ground-water flow in stratified drift and bedrock with a three-layer ground-water-flow model. A new model routine, the Variable-Recharge procedure, was developed to simulate areal recharge and the contribution of the uplands to the drift system. This procedure allows for water applied to land surface to infiltrate or to be rejected. Rejected recharge and ground water discharged when the water table is at land surface form surface runoff-this excess upland water can be redirected as runoff to other parts of the model. Infiltration of streamwater, areal recharge to uplands and valley, and lateral subsurface flow from the uplands to the valley are sources of water to the stratufued0druft aquifer. Water is removed from the stratified-drift aquifer at Wooster primarily by production wells pumping at a rate of approximately 8.5 ft3/s (cubic feet per second). The ground-water budget resulting from two types of simulations of ground-water flow in this study indicates the primary sources of water to the wells are recharge at or near land surface and lateral subsurface flow from the shale and sandstone bedrock. Components of recharge at land surface include induced infiltration from streams, precipitation on the valley floor, and infiltration of unchanneled upland runoff that reaches the valley floor. The steady-state simulation was designed to represent conditions during the fall of 1984. The transient simulation was designed to represent an 11-day snowmelt event, 23 February to 5 March 1985, that caused water levels to rise significantly throughout the valley. Areal recharge to the valley and flow from the uplands to the valley were determined through the Variable-Recharge procedure. The total steady-state recharge to the valley was 12.5 ft3/s. Upland sources, areal valley recharge, and induced infiltration from Killnuck Creek accounted for 63, 23, and 8 percent, respectively, of the valley recharge. An analysis of the simulated vertical flow to the buried stratified drift through surficial slit, clay, and fine sand indicates that about 75 percent of the total recharge to the buried deposits is the sum of areally extensive, relatively small flows less than about 0.01 ft? /s per model node), whereas about 25 percent of the recharge results from a really restricted, relatively large flows (greater than about 0.01 ft? /s per model node). The large-magnitude flows are located primarily beneath Clear and Little Killbuck Creeks where seepage provides abundant recharge and the surficial sediments grade into coarser alluvial-fan deposits. Chemical and isotopic studies of ground water and streamwater combined with measurements of stream infiltration provide independent support for the conclusions derived from computer simulation of ground-water flow. In addition, the chemical and isotopic studies helped quantity the rate and pathways of infiltrating water from

Water-Resources Investigations Report↗
USGS1966

Availability of ground water upper Pawcatuck River basin Rhode Island

The upper Pawcatuck River basin is a 70-square-mile area in southcentral Rhode Island consisting of broad, rolling hills and narrow valleys in the north and fiat-floored plains in the south. It is drained by the Pawcatuck River and its two major tributaries, the Usquepaug-Queen River and the Chipuxet River. Analysis of the water budget for the basin shows that approximately 94 mgd (million gallons per day) or about 63 percent of the precipitation flows out of the basin as streamflow. Of this amount, about 66 mgd is from ground-water seepage. Two ground-water reservoirs composed of glacial deposits of sand and gravel and capable of substantial yields are in the basin. The larger reservoir underlies the central part of the Usquepaug-Queen River valley. This reservoir ranges in width from 3,000 to 4,000 feet and is 32,000 feet long. A large part of the reservoir contains sand and gravel more than 100 feet thick, having a permeability of more than 1,000 gallons per day per square foot. The yield of this reservoir is estimated to be about 17 mgd. The smaller ground-water reservoir is in the Chipuxet River valley. It is about 4,000 feet wide and 16,000 feet long. A large part of this reservoir contains sand and gravel more than 150 feet thick having a permeability of more than 1,000 gallons per day per square foot. The yield of the Chipuxet reservoir is estimated to be about 8.6 mgd. Mineral content of water from both of the reservoirs is generally less than 200 parts per million of dissolved solids. However, in the Chipuxet groundwater reservoir the dissolved solids are somewhat higher, and the iron content is a problem. Only about 1.5 mgd of water is used in the basin. Most of it is used for public supplies and is obtained from wells not tapping the Usquepaug-Queen or Chipuxet ground-water reservoirs. Estimates of the 25 mgd of ground water potentially available are believed to be conservative, and substantially larger quantities may actually be available when development takes place.

Rhode Island↗
USGS1981

Ground-water quality in the vicinity of landfill sites, southern Franklin County, Ohio

The hydrogeology and ground-water quality in the vicinity of five landfills in southern Franklin County, Ohio, were investigated by use of data obtained from 46 existing wells, 1 seep, 1 surface-water site, and 1 leachate-collection site. Interpretation was based on data from the wells, a potentiometric-surface map, and chemical analyses. Four of the five landfills are in abandoned sand and gravel pits. Pumping of water from a quarry near the landfills has modified the local ground-water flow pattern, increased the hydraulic gradient, and lowered the water table. Ground water unaffected by the landfills is a hard, calcium bicarbonate type with concentrations of dissolved iron and dissolved sulfate as great as 3.0 milligrams per liter and 200 milligrams per liter, respectively. Water sampled from wells downgradient from two landfills shows an increase in sodium, chloride, and other constituents. The change in water quality cannot be traced directly to the landfills, however, because of well location and the presence of other potential sources of contamination. Chemical analysis of leachate from a collection unit at one landfill shows significant amounts of zinc, chromium, copper, and nickel, in addition to high total organic carbon, biochemical oxygen demand, and organic nitrogen. Concentrations of chloride, iron, lead, manganese and phenolic compounds exceed Ohio Environmental Protection Agency Water Quality Standards for drinking water. Water from unaffected wells within the study area have relatively small amounts of these constituents. (USGS)

Open-File Report↗
USGS2006

Estimates of ground-water pumpage from the Yakima River Basin aquifer system, Washington, 1960-2000

Ground-water pumpage in the Yakima River Basin, Washington, was estimated for eight categories of use for 1960-2000 as part of an investigation to assess groundwater availability in the basin. Methods used, pumpage estimates, reliability of the estimates, and a comparison with appropriated quantities are described. The eight categories of pumpage were public water supply, self-supplied domestic (exempt wells), irrigation, frost protection, livestock and dairy operations, industrial and commercial, fish and wildlife propagation, and ground-water claims. Pumpage estimates were based on methods that varied by the category and primarily represent pumpage for groundwater rights. Washington State Department of Ecology’s digital database has 2,874 active ground-water rights in the basin that can withdraw an annual quantity of about 529,231 acre-feet during dry years. Irrigation rights are for irrigation of about 129,570 acres. All but 220 of the rights were associated with well drillers’ logs, allowing for a spatial representation of the pumpage. Five-hundred and sixty of the irrigation rights were estimated to be standby/reserve rights. During this study, another 30 rights were identified that were not in the digital database. These rights can withdraw an annual quantity of about 20,969 acre-feet; about 6,700 acre-feet of these rights are near but outside the basin. In 1960, total annual pumpage in the basin, excluding standby/reserve pumpage, was about 115,776 acre-feet. By 2000, total annual pumpage was estimated to be 395,096 acre-feet, and excluding the standby/reserve rights, the total was 312,284 acre-feet. Irrigation accounts for about 60 percent of the pumpage, followed by public water supply at about 12 percent. The smallest category of pumpage was for livestock use with pumpage estimated to be 6,726 acre-feet. Total annual pumpage in 2000 was about 430 cubic feet per second, which is about 11 percent of the surface-water demand. Maximum pumpage is in July and August and during 2000, was about 100 cubic feet per second each month averaged over the Yakima River Basin aquifer system. During 2000, non-standby/reserve pumpage associated with ground-water rights was estimated to total 253,454 acre-feet, or about 198,290 acre-feet less than the appropriated quantity. The unused part of the appropriated value is about equivalent to the irrigation pumpage for primary rights.

Washington↗
USGS2007

Ground-Water Flow Model of the Sierra Vista Subwatershed and Sonoran Portions of the Upper San Pedro Basin, Southeastern Arizona, United States, and Northern Sonora, Mexico

A numerical ground-water model was developed to simulate seasonal and long-term variations in ground-water flow in the Sierra Vista subwatershed, Arizona, United States, and Sonora, Mexico, portions of the Upper San Pedro Basin. This model includes the simulation of details of the groundwater flow system that were not simulated by previous models, such as ground-water flow in the sedimentary rocks that surround and underlie the alluvial basin deposits, withdrawals for dewatering purposes at the Tombstone mine, discharge to springs in the Huachuca Mountains, thick low-permeability intervals of silt and clay that separate the ground-water flow system into deep-confined and shallow-unconfined systems, ephemeral-channel recharge, and seasonal variations in ground-water discharge by wells and evapotranspiration. Steady-state and transient conditions during 1902-2003 were simulated by using a five-layer numerical ground- water flow model representing multiple hydrogeologic units. Hydraulic properties of model layers, streamflow, and evapotranspiration rates were estimated as part of the calibration process by using observed water levels, vertical hydraulic gradients, streamflow, and estimated evapotranspiration rates as constraints. Simulations approximate observed water-level trends throughout most of the model area and streamflow trends at the Charleston streamflow-gaging station on the San Pedro River. Differences in observed and simulated water levels, streamflow, and evapotranspiration could be reduced through simulation of climate-related variations in recharge rates and recharge from flood-flow infiltration.

Scientific Investigations Report↗
USGS1980

The effects of using ground water to maintain water levels of Cedar Lake, Wisconsin

Cedar Lake, a kettle lake with no surface inlet or outlet, was studied to evaluate the feasibility of maintaining water levels of lakes in the glaciated kettle moraine area of eastern Wisconsin by pumping ground water into them. The general hydrogeology of the area around the lake was defined and the hydrology of the lake was studied in detail. There are two aquifer systems in the Cedar Lake area, and in general, throughout eastern Wisconsin. The shallow aquifer system is composed of unconsolidated glacial drift of Quaternary age and consolidated bedrock of Silurian age. Cedar Lake is located in a local recharge area within this system. The saturated thicknesses of the glacial drift and Silurian dolomite beneath the lake are approximately 100 feet and 500 feet, respectively. This aquifer system is separated from an underlying aquifer system by a layer of shale approximately '200 feet thick that forms an effective barrier to water movement. The deep aquifer system is composed of dolomites and sandstones of Ordovician and Cambrian age whose composite thickness is 600 to 650 feet. A water budget was prepared to quantify the components of the hydrologic system of Cedar Lake. Inflow to the lake averaged approximately ^5 inches per water year for the 2-year period October 197^ through September 1976. Inflow consisted of precipitation on the lake surface (28 inches), groundwater seepage to the lake (2 inches), and overland flow (15 inches) to the lake. Outflow averaged approximately U9 inches per year for the same 2- year period. Outflow consisted of evaporation (31 inches) from the lake surface and ground-water seepage from the lake (18 inches). A volume of water equivalent to that needed to raise the lake level 1*7 inches was pumped from the shallow aquifer system into Cedar Lake between February 1 and September 30, 1977. The water budget for the lake during this period indicated that approximately 90 percent of pumped water was either recycled from the lake to the well or otherwise lost as seepage from the lake. Selected physical and chemical characteristics of the lake water were measured periodically between October 197^ and September 1977- The water temperature ranged between 26°C in August to approximately 2°C in December during each year of the study. The dissolved-oxygen concentration of the water ranged from 13 milligrams per liter at the time ice cover first developed in December to h milligrams per liter at the time ice cover broke up the following April. The total nitrogen concentration of the water varied from 1.0 milligrams per liter during winter to 0.5 milligrams per liter during summer. The total phosphorus concentration of the water was fairly uniform throughout the year, averaging 0.01 milligrams per liter. The phytoplankton population was sampled periodically. The total phytoplankton count was small during winter, generally less than 250 cells per milliliter. These phytoplankton were composed of euglenoids, diatoms, green algae, and blue-green algae. The count increased to 50,000 to 100,000 cells per milliliter during summer. One or two species of blue-green algae dominated during these times. There were no identifiable changes in measured physical and chemical characteristics of lake water during sustained pumping of ground water into the lake, nor were there identifiable changes in the number or makeup of the phytoplankton community. Differences in physical and chemical characteristics of lake water and ground water added to the lake probably were not great enough to cause changes within the lake.

Wisconsin↗
USGS1982

Reconnaissance of ground-water quality, eastern Snake River basin, Idaho

Water-quality, geologic, and hydrologic data were collected for 165 wells in the eastern Snake River basin, Idaho. Water-quality characteristics analyzed include specific conductance, pH, water temperature, major dissolved cations and anions, and coliform bacteria. Ground water from aquifers in all rock units is generally composed of calcium, magnesium, and bicarbonate type and contains carbonate ions. Changes in area trends of ground-water composition probably are most directly related to variability in aquifer composition and proximity to varying sources of recharge, especially those related to man 's land- and water-use activities. In the uplands subareas, median values for selected ground-water characteristics from current analyses are 2000 mg/l hardness; 7.6, pH; 200 mg/l alkalinity; 13C; 0.2 mg/l fluoride; 15 mg/l silica; 0.51 mg/l nitrite (as nitrogen); less than 1 colony per 100 milliliters of water coliform bacteria; 0.02 mg/l phosphorus (total); and 25 mg/l hardness; 7.7, pH; 180 mg/l alkalinity; 11C; 0.4 mg/l fluoride; 26 mg/l silica; 1.2 mg/l nitrite plus nitrate; less than 1 colony per 100 milliliters of water coliform bacteria; 0.01 amg/l phosphorus; and 283 mg/l dissolved solids. Ground-water quality in most of the study area meets recommended standards or criteria for most uses. (USGS)

Water-Resources Investigations Report↗
USGS2004

Evaluation of ground-water contribution to streamflow in coastal Georgia and adjacent parts of Florida and South Carolina

Stream-aquifer relations in the coastal area of Georgia and adjacent parts of Florida and South Carolina were evaluated as part of the Coastal Georgia Sound Science Initiative, the Georgia Environmental Protection Division's strategy to protect the Upper Floridan aquifer from saltwater intrusion. Ground-water discharge to streams was estimated using three methods: hydrograph separation, drought-streamflow measurements, and linear-regression analysis of streamflow duration. Ground-water discharge during the drought years of 1954, 1981, and 2000 was analyzed for minimum ground-water contribution to streamflow. Hydrograph separation was used to estimate baseflow at eight streamflow gaging stations during the 31-year period 1971?2001. Six additional streamflow gaging stations were evaluated using linear-regression analysis of flow duration to determine mean annual baseflow. The study area centers on three major river systems ? the Salkehatchie?Savannah?Ogeechee, Altamaha?Satilla?St Marys, and Suwannee ? that interact with the underlying ground-water system to varying degrees, largely based on the degree of incision of the river into the aquifer and on the topography. Results presented in this report are being used to calibrate a regional ground-water flow model to evaluate ground-water flow and stream-aquifer relations of the Upper Floridan aquifer. Hydrograph separation indicated decreased baseflow to streams during drought periods as water levels declined in the aquifer. Average mean annual baseflow ranged from 39 to 74 percent of mean annual streamflow, with a mean contribution of 58 percent for the period 1971?2001. In a wet year (1997), baseflow composed from 33 to 70 percent of mean annual streamflow. Drought-streamflow analysis estimated baseflow contribution to streamflow ranged from 0 to 24 percent of mean annual streamflow. Linear-regression analysis of streamflow duration estimated the Q35 (flow that is equaled or exceeded 35 percent of the time) as the most reasonable estimate of baseflow. The Q35, when compared to mean annual streamflow, estimated a baseflow contribution ranging from 65 to 102 percent of streamflow. The Q35 estimate tends to overestimate baseflow as evidenced by the baseflow contribution greater than 100 percent. Ground-water contributions to streamflow are greatest during winter when evapotranspiration is low, and least during summer when evapotranspiration is high. Baseflow accounted for a larger percentage of streamflow at gaging stations in the Salkehatchie?Savannah?Ogeechee River Basin than in the other two basins. This difference is due largely to the availability of data, proximity to the Piedmont physiographic province where the major rivers originate and are by supplied ground water, and proximity to the upper Coastal Plain where there is greater topographic relief and interconnection between streams and aquifers.

Florida, Georgia, South Carolina↗
USGS1994

Local point sources that affect ground-water quality in the East Meadow area, Long Island, New York

The extent and chemical characteristics of ground water affected by three local point sources--a stormwater basin, uncovered road-salt-storage piles, and an abandoned sewage-treatment plant--were delineated during a 3-year study of the chemical characteristics and migration of a body of reclaimed wastewater that was applied to the watertable aquifer during recharge experiments from October 1982 through January 1984 in East Meadow. The timing, magnitude, and chemical quality of recharge from these point sources is highly variable, and all sources have the potential to skew determinations of the quality of ambient ground-water and of the reclaimed-wastewater plume if they are not taken into account. Ground water affected by recharge from the stormwater basin is characterized by low concentrations of nitrate + nitrite (less than 5 mg/L [milligrams per liter] as N) and sulfate (less than 40 mg/L) and is almost entirely within the upper glacial aquifer. The plume derived from road-salt piles is narrow, has high concentrations of chloride (greater than 50 mg/L) and sodium (greater than 75 mg/L), and also is limited to the upper glacial aquifer. The sodium, in high concentrations, could react with aquifer material and exchange for sorbed cations such as calcium, potassium, and magnesium. Water affected by secondary-treated sewage from the abandoned treatment plant extends 152 feet below land surface into the upper part of the Magothy aquifer and longitudinally beyond the southern edge of the study area, 7,750 feet south of the recharge site. Ground water affected by secondary-treated sewage within the study area typically contains elevated concentrations of reactive chemical constituents, such as potassium and ammonium, and low concentrations of dissolved oxygen. Conservative or minimally reactive constituents such as chloride and sodium have been transported out of the study area in the upper glacial aquifer and the intermediate (transitional) zone but remain in the less permeable upper part of the Magothy aquifer. Identification of the three point sources and delineation of their areas of influence improved definition of ambient ground-water quality and delineation of the reclaimed-wastewater plume.

Water-Resources Investigations Report↗
USGS1986

Hydrogeology and ground-water use and quality, Brown County, Wisconsin

The Paleozoic rock of Brown County includes formations of Cambrian, Ordovician, and Silurian age. These formations are eastward-dipping sedimentary rock that rest on Precambrian crystalline rock and are overlain by Pleistocene deposits. The units that are the principal sources of ground water were grouped into three aquifers (upper, St. Peter, and Elk Mound), and the less permeable units are grouped into three confining units (Maquoketa-Sinnipee, St. Lawrence, and Precambrian). The geologic and hydraulic characteristics of the aquifers and confining units are estimated from logs of more than 1,000 Brown County wells, from results of a packer test, and from published values. Recharge to the water table, which was estimated at five monitored sites, ranges from 1 to 6 inches a year; most recharge is contributed by spring snowmelt and rainfall. A cone of depression caused by pumping the deeper aquifers in the Green Bay metropolitan area induces flow from the upper aquifer to the underlying st. Peter aquifer throughout most of the county. Several reaches of Duck Creek and the Suamico River also contribute water to the aquifers. A bout 13 million gallons per day of ground water was pumped in Brown County during 1979, 63 percent of which was from wells open to both the St. Peter and Elk Mound aquifers. Municipal and industrial water users pumped 9.44 million gallons per day or 72 percent of the ground water withdrawn in 1979. Most ground :water in the county is a calcium magnesium bicarbonate type. However, water from wells sampled in an area between the Fox River and Silurian escarpment have elevated levels of sodium (44 milligrams per liter) and sulfate (226 milligrams per liter). Water from wells that tap rocks older than Silurian dolomite contains high concentrations of strontium (more than 2.4 milligrams per liter) and fluoride (more than 0.85 milligrams per liter). A three-dimensional digital model was used to simulate flow in the ground-water system. Model results indicate that sources of ground water pumped from wells tapping the St. Peter and Elk Mound aquifers in Brown County, 1979, include 4.8 million gallons per day of underflow, most of which enters the county across the west border; 1.9 million gallons per day of flow from vertical leakage within the county; and 1.5 million gallons per day from storage. The model is most sensitive to the horizontal hydraulic conductivity of the upper aquifer. Vertical hydraulic conductivity of the confining units and recharge rates to the water-table aquifer are the least well-defined model parameters.

Wisconsin↗
USGS1995

Sources of geologic and hydrologic information pertinent to ground-water resources in Rhode Island

This report summarizes sources of geologic and hydrologic information useful to water managers and others involved in the investigation, appraisal, development, and protection of ground-water resources in Rhode Island. The geographic scope of the report includes Rhode Island and small adjoining areas of Massachusetts and Connecticut, where drainage basins are shared with these States. The information summarized is found in maps and reports prepared by the U.S. Geological Survey and published by either the U.S. Geological Survey or by the State of Rhode Island. Information sources are presented in maps and tables. Reference maps show drainage divides, town lines, and the 7.5-minute grid of latitude and longitude for the State. Maps show availability of surficial geologic maps, bedrock geologic maps, and ground-water studies by 7.5-minute quadrangle, and show availability of ground-water studies by drainage basin, subbasin, and special study area. Sources of geologic and hydrologic information for the thirty-seven 7.5-minute quadrangles covering Rhode Island have been compiled based on the following information categories: surficial geology, bedrock geology, subsurface materials, altitude of bedrock surface, water-table altitudes, water-table contours, saturated thickness, hydraulic conductivity, transmissivity, drainage divides, recharge areas, ground-water reservoirs, induced infiltration, and ground-water quality. A table for each of the 37 quadrangles lists the major categories of information available for that quadrangle, provides references to the publications in which the information can be found, and indicates the format, scale, and other pertinent attributes of the information. A table organized by report series gives full citations for publications prepared by the U.S. Geological Survey pertaining to the geology and hydrology of Rhode Island. To facilitate location of information for particular municipalities, a table lists cities and towns in the State and the quadrangles that cover each municipality.

Rhode Island↗
USGS1996

Hydrogeology and ground-water resources of Kahlap Island, Mwoakilloa Atoll, State of Pohnpei, Federated States of Micronesia

The lens of fresh ground water on Kahlap Island contains about 21.3 million gallons of potable water. Recharge to the freshwater lens is estimated to be 125,000 gallons per day on the basis of a mean annual rainfall of 120 inches. The long-term average sustainable yield is estimated to be about 17,300 gallons per day. The estimated demand for water is about 13,500 gallons per day. Shallow-vertical-tube wells or horizontal- infiltration wells could be used to develop the freshwater lens. The effect of development on the lens can be determined by monitoring the chloride concentration of water from a network of shallow- water-table and deep driven wells. The ground- water resource on Kahlap can be used in conjunc- tion with individual rainwater-catchment systems: rainwater can be used for drinking and cooking, and ground water can be used for sanitary uses. When rainwater-catchment systems fail during extended dry periods, ground water would be available to meet the total demand.

Water-Resources Investigations Report↗
USGS2005

Bioremediation of petroleum hydrocarbon-contaminated ground water: The perspectives of history and hydrology

Bioremediation, the use of microbial degradation processes to detoxify environmental contamination, was first applied to petroleum hydrocarbon-contaminated ground water systems in the early 1970s. Since that time, these technologies have evolved in some ways that were clearly anticipated early investigators, and in other ways that were not foreseen. The expectation that adding oxidants and nutrients to contaminated aquifers would enhance biodegradation, for example, has been born out subsequent experience. Many of the technologies now in common use such as air sparging, hydrogen peroxide addition, nitrate addition, and bioslurping, are conceptually similar to the first bioremediation systems put into operation. More unexpected, however, were the considerable technical problems associated with delivering oxidants and nutrients to heterogeneous ground water systems. Experience has shown that the success of engineered bioremediation systems depends largely on how effectively directions and rates of ground water flow can be controlled, and thus how efficiently oxidants and nutrients can be delivered to contaminated aquifer sediments. The early expectation that injecting laboratory-selected or genetically engineered cultures of hydrocarbon-degrading bacteria into aquifers would be a useful bioremediation technology has not been born out subsequent experience. Rather, it appears that petroleum hydrocarbon-degrading bacteria are ubiquitous in ground water systems and that bacterial addition is usually unnecessary. Perhaps the technology that was least anticipated early investigators was the development of intrinsic bioremediation. Experience has shown that natural attenuation mechanisms - biodegradation, dilution, and sorption - limit the migration of contaminants to some degree in all ground water systems. Intrinsic bioremediation is the deliberate use of natural attenuation processes to treat contaminated ground water to specified concentration levels at predetermined points in the aquifer. In current practice, intrinsic bioremediation of petroleum hydrocarbons requires a systematic assessment to show that ambient natural attenuation mechanisms are efficient enough to meet regulatory requirements and a monitoring program to verify that performance requirements are met in the future.

Ground Water↗
USGS2004

A theory for modeling ground-water flow in heterogeneous media

Construction of a ground-water model for a field area is not a straightforward process. Data are virtually never complete or detailed enough to allow substitution into the model equations and direct computation of the results of interest. Formal model calibration through optimization, statistical, and geostatistical methods is being applied to an increasing extent to deal with this problem and provide for quantitative evaluation and uncertainty analysis of the model. However, these approaches are hampered by two pervasive problems: 1) nonlinearity of the solution of the model equations with respect to some of the model (or hydrogeologic) input variables (termed in this report system characteristics) and 2) detailed and generally unknown spatial variability (heterogeneity) of some of the system characteristics such as log hydraulic conductivity, specific storage, recharge and discharge, and boundary conditions. A theory is developed in this report to address these problems. The theory allows construction and analysis of a ground-water model of flow (and, by extension, transport) in heterogeneous media using a small number of lumped or smoothed system characteristics (termed parameters). The theory fully addresses both nonlinearity and heterogeneity in such a way that the parameters are not assumed to be effective values. The ground-water flow system is assumed to be adequately characterized by a set of spatially and temporally distributed discrete values, ?, of the system characteristics. This set contains both small-scale variability that cannot be described in a model and large-scale variability that can. The spatial and temporal variability in ? are accounted for by imagining ? to be generated by a stochastic process wherein ? is normally distributed, although normality is not essential. Because ? has too large a dimension to be estimated using the data normally available, for modeling purposes ? is replaced by a smoothed or lumped approximation y?. (where y is a spatial and temporal interpolation matrix). Set y?. has the same form as the expected value of ?, y 'line' ? , where 'line' ? is the set of drift parameters of the stochastic process; ?. is a best-fit vector to ?. A model function f(?), such as a computed hydraulic head or flux, is assumed to accurately represent an actual field quantity, but the same function written using y?., f(y?.), contains error from lumping or smoothing of ? using y?.. Thus, the replacement of ? by y?. yields nonzero mean model errors of the form E(f(?)-f(y?.)) throughout the model and covariances between model errors at points throughout the model. These nonzero means and covariances are evaluated through third and fifth-order accuracy, respectively, using Taylor series expansions. They can have a significant effect on construction and interpretation of a model that is calibrated by estimating ?.. Vector ?.. is estimated as 'hat' ? using weighted nonlinear least squares techniques to fit a set of model functions f(y'hat' ?) to a. corresponding set of observations of f(?), Y. These observations are assumed to be corrupted by zero-mean, normally distributed observation errors, although, as for ?, normality is not essential. An analytical approximation of the nonlinear least squares solution is obtained using Taylor series expansions and perturbation techniques that assume model and observation errors to be small. This solution is used to evaluate biases and other results to second-order accuracy in the errors. The correct weight matrix to use in the analysis is shown to be the inverse of the second-moment matrix E(Y-f(y?.))(Y-f(y?.))', but the weight matrix is assumed to be arbitrary in most developments. The best diagonal approximation is the inverse of the matrix of diagonal elements of E(Y-f(y?.))(Y-f(y?.))', and a method of estimating this diagonal matrix when it is unknown is developed using a special objective function to compute 'hat' ?. When considered to be an estimate of f

Professional Paper↗
USGS2002

Soil chemistry and ground-water quality of the water-table zone of the surficial aquifer, Naval Submarine Base Kings Bay, Camden County, Georgia, 1998 and 1999

In 1998, the U.S. Geological Survey, in cooperation with the U.S. Department of the Navy, began an investigation to determine background ground-water quality of the water-table zone of the surficial aquifer and soil chemistry at Naval Submarine Base Kings Bay, Camden County, Georgia, and to compare these data to two abandoned solid- waste disposal areas (referred to by the U.S. Navy as Sites 5 and 16). The quality of water in the water-table zone generally is within the U.S. Environmental Protection Agency (USEPA) drinking-water regulation. The pH of ground water in the study area ranged from 4.0 to 7.6 standard units, with a median value of 5.4. Water from 29 wells is above the pH range and 3 wells are within the range of the USEPA secondary drinking-water regulation (formerly known as the Secondary Maximum Contaminant Level or SMCL) of 6.5 to 8.5 standard units. Also, water from one well at Site 5 had a chloride concentration of 570 milligrams per liter (mg/L,), which is above the USEPA secondary drinking-water regulation of 250 mg/L. Sulfate concentrations in water from two wells at Site 5 are above the USEPA secondary drinking-water regulation of 250 mg/L. Of 22 soil-sampling locations for this study, 4 locations had concentrations above the detection limit for either volatile organic compounds (VOCs), base-neutral acids (BNAs), or pesticides. VOCs detected in the study area include toluene in one background sample; and acetone in one background sample and one sample from Site 16--however, detection of these two compounds may be a laboratory artifact. Pesticides detected in soil at the Submarine Base include two degradates of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT): 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (4,4'-DDD) in one background sample, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (4,4'-DDE) in one background sample and one sample from Site 16; and dibenzofuran in one sample from Site 16. BNAs were detected in one background sample and in two samples from Site 16. Hypothesis testing, using the Wilcoxon rank-sum test (also known as the Mann-Whitney test), indicates no statistical difference between ground-water constituent concentrations from Sites 5 and 16, and background concentrations. Hypothesis testing, however, indicates the concentration of barium in background ground-water samples is greater than in ground-water samples collected at Site 16.

Georgia↗
USGS2002

Ground-water-quality data for Albany and surrounding areas, Southwest Georgia, 1951-99

This report presents ground-water-quality data from the surficial, Upper Floridan, Claiborne, Clayton, and Upper Cretaceous aquifers in the Albany and surrounding areas of southwest Georgia. Water-quality data from about 186 wells in Baker, Calhoun, Dougherty, Lee, Mitchell, Terrell, and Worth Counties are presented for the period from 1951 through 1999. The data include field water-quality parameters collected during 1951-99, volatile and semi-volatile organic compounds collected during 1981-97, inorganic compounds collected during 1951-99, trace metals collected during 1964-99, radiochemicals collected during 1993-95, herbicides and insecticides collected during 1980-97, and recovery data for laboratory surrogate compounds (used for quality control and quality assurance for organic samples) collected during 1993-97. Ground-water quality data are presented in tables by data type and arranged by well number. Illustrations in this report contain information about study area location, well location, stratigraphy, and formation water-bearing properties. Ground-water-quality data are presented in text files and in a data base that includes geographic and tabular data. Data presented in this report provide a base with which to better define and interpret the quality of ground water in Albany, Ga., and surrounding areas. Although some of these data may have been published in previous reports associated with water-resources investigations, water-quality data are compiled as a useful resource.

Georgia↗
USGS1990

Ground-water conditions in Utah, spring of 1990

This is the twenty-seventh in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawal from wells, water-level changes, related changes in precipitation and streamflow, and chemical quality of water. Supplementary data such as graphs showing chemical quality of water and maps showing water-level contours are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions. This report includes individual discussions of selected major areas of ground-water development in the State for the calendar year 1989. Water-level fluctuations and selected related data, however, are described from the spring of 1989 to the spring of 1990. Much of the data used in this report were collected by the U.S. Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.

Utah↗
USGS1991

Ground-water conditions in Utah, spring of 1991

This is the twenty-eighth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series, published cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources, provide data to enable interested parties to keep abreast of changing ground-water conditions. This report, like the others in the series, contains information on well construction, ground-water withdrawal from wells, water-level changes, related changes in precipitation and streamflow, and chemical quality of water. Supplementary data, such as maps showing water-level contours, are included in reports of this series only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions. This report includes individual discussions of selected major areas of ground-water development in the State for the calendar year 1990. Water-level fluctuations and selected related data, however, are described from the spring of 1986 to the spring of 1991. Much of the data used in this report were collected by the U.S. Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.

Utah↗