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USGS1998

Optimization of ground-water withdrawal in the lower Fox River communities, Wisconsin

Pumping from closely spaced wells in the Central Brown County area and the Fox Cities area near the north shore of Lake Winnebago has resulted in the formation of deep cones of depression in the vicinity of the two pumping centers. Water-level measurements indicate there has been a steady decline in water levels in the vicinity of these two pumping centers for the past 50 years. This report describes the use of ground-water optimization modeling to efficiently allocate the ground-water resources in the Lower Fox River Valley. A 3-dimensional ground-water flow model was used along with optimization techniques to determine the optimal withdrawal rates for a variety of management alternatives. The simulations were conducted separately for the Central Brown County area and the Fox Cities area. For all simulations, the objective of the optimization was to maximize total ground-water withdrawals. The results indicate that ground water can supply nearly all of the projected 2030 demand for Central Brown County municipalities if all of the wells are managed (including the city of Green Bay), 8 new wells are installed, and the water-levels are allowed to decline to 100 ft below the bottom of the confining unit. Ground water can supply nearly all of the projected 2030 demand for the Fox Cities if the municipalities in Central Brown County convert to surface water; if Central Brown County municipalities follow the optimized strategy described above, there will be a considerable shortfall of available ground water for the Fox Cities communities. Relaxing the water-level constraint in a few wells, however, would likely result in increased availability of water. In all cases examined, optimization alternatives result in a rebound of the steady-state water levels due to projected 2030 withdrawal rates to levels at or near the bottom of the confining unit, resulting in increased well capacity. Because the simulations are steady-state, if all of the conditions of the model remain the same these withdrawal rates would be sustainable in perpetuity.

Wisconsin↗

USGS2003

Numerical simulation of ground-water flow in La Crosse County, Wisconsin, and into nearby pools of the Mississippi River

This report describes a two-dimensional regional screening model and two associated three-dimensional ground-water flow models that were developed to simulate the ground-water flow systems in La Crosse County, Wisconsin, and Pool 8 of the Mississippi River. Although the geographic extents of the three-dimensional models were slightly different, both were derived from the same geologic interpretation and regional screening model, and their calibrations were performed concurrently. The objectives of the La Crosse County (LCC) model were to assess the effects of recent (1990s) and potential future ground-water withdrawals and to provide a tool suitable to evaluate the effects of proposed water-management programs. The Pool 8 model objectives were to quantify the magnitude and distribution of ground-water flow into the Pool. The Wisconsin Geological and Natural History Survey and the U.S. Geological Survey developed the models cooperatively. The report describes: 1) the conceptual hydrogeologic model; 2) the methods used in simulating flow; 3) model calibration and sensitivity analysis; and 4) model results, such as simulation of predevelopment conditions and location and magnitude of ground-water discharge into Pool 8 of the Mississippi. Three aquifer units underlie the model area: 1) a shallow unconsolidated sand and gravel aquifer; 2) an upper bedrock aquifer, composed of Cambrian and Ordovician sandstone and dolomite; and 3) a lower bedrock aquifer composed of Cambrian sandstone of the Eau Claire Formation and the Mount Simon Formation. A shale layer that is part of the Eau Claire Formation forms a confining unit separating the upper and lower bedrock aquifers. This confining unit is absent in the Black River and parts of the La Crosse and Mississippi River valleys. Precambrian crystalline basement rock forms the lower base of the ground-water flow system. The U.S. Geological Survey ground-water flow model code, MODFLOW, was used to develop the La Crosse County (LCC) and Pool 8 ground-water flow models. Boundary conditions for the MODFLOW model were extracted from an analytic element screening model of the regional flow system surrounding La Crosse County. Model input was obtained from previously published and unpublished geologic and hydrologic data. Pumpages from municipal and high-capacity wells were also simulated. Model calibration included a comparison of modeled and field-measured water levels and field-measured base flows to simulated stream flows. At calibration, most measured water levels compared favorably to model-calculated water levels. Simulated streamflows at two targets were within 3 percent of estimated measured base flows. Mass balance results from the LCC and Pool 8 models indicated that 63 to 74 percent of ground water was from recharge and 19 to 26 percent was from surface-water sources. Ground-water flow out of the model was to rivers and streams (85 to 87 percent) and pumping wells (11 and 13 percent). The model demonstrates the effects of development on ground water in the study area. The maximum simulated water-level decline in the city of La Crosse metropolitan area is 9.3 feet. Simulated stream losses are similar to the amount of ground water pumped by wells. This indicates that ground water withdrawn by La Crosse County wells is water that under predevelopment conditions discharged to streams and lakes. The models provide estimates of the locations and amount of ground-water flow into Pool 8 and the southern portion of Pool 7 of the Mississippi River. Ground-water discharges into all areas of the pools, except along the eastern shore in the vicinity of the city of La Crosse and immediately downgradient from lock and dam 7 and 8. Ground-water flow into the pools is generally greatest around the perimeter with decreasing amounts away from the perimeter. An area of relatively high ground-water discharge extends out towards the center of Pool 7 from the upper reaches of the pool and may

Wisconsin↗

USGS1959

Ground-water resources of the lower Niobrara River and Ponca Creek basins, Nebraska and South Dakota

This report describes the area in north-central Nebraska and south-central South Dakota drained by Ponca Creek and by the Niobrara River below Valentine, Nebr. The Niobrara River and Ponca Creek are neighboring eastward flowing tributaries of the Missouri River. The Dakota sandstone of Cretaceous age is the oldest formation tapped by wells; the water it yields to wells in small to moderate quantities is rather highly mineralized and very hard; it is unsuitable for irrigation and most domestic uses. Overlying the Dakota, in ascending order, are the following formations of Cretaceous age: the Graneros shale, Greenhorn limestone, Carlile shale, Niobrara formation, and Pierre shale. None of these is a source of water supply. The Niobrara is the oldest formation exposed, cropping out in only the deeper valleys at the eastern end of the area. The Pierre shale, which is exposed much more extensively, crops out in the deeper valleys throughout nearly all the area. Except where the Niobrara River, its major tributaries, and Ponca Creek have cut their valleys into them, the Cretaceous rocks are overlain by semiconsolidated rocks of Tertiary age. Two Tertiary formations, the Brule and the Ogallala, are present in the area. The Brule formation underlies all the western part of the area and is exposed in the valleys of both the Niobrara and Keya Paha Rivers. The Ogallala formation, which overlaps the Brule, forms the upland on both sides of the river and is exposed in many places. The Brule is not a source of water supply, whereas the Ogallala yields small to moderately large quantities of water to many wells on the upland. The water in the Ogallala is of the calcium bicarbonate type and is moderately mineralized and hard. Unconsolidated deposits of Quaternary age mantle the Tertiary rocks throughout nearly all the upland area south of the Niobrara River and in parts of the upland area north of the river. They also floor the Niobrara River valley. Where saturated, these sediments, which consist of stream-deposited sand and gravel and wind-deposited sand, yield small to large amounts of water to wells. The water in the Quaternary deposits is of the calcium bicarbonate type but is less mineralized and softer than that in the Ogallala. The only significant source of recharge to the Dakota sandstone in the report area is underflow from the west. Except for waiter yielded to wells tapping the Dakota, water in the formation is discharged from the area by underflow to the east. In the upland part of the area, the Ogallala formation and the overlying deposits of Quaternary age constitute a single aquifer, water moving from one Into the other without apparent hindrance. This aquifer is recharged principally by the direct infiltration of precipitation but in part also by underflow from the west and south and by seepage from intermittent streams and ponds. Water is discharged from the upland aquifer by outflow through springs or seepage into streams, through the process of evapotranspiration, and by wells when they are pumped. Ground water leaves the report area by underflow where the Quaternary deposits in the valleys of the Niobrara River and Ponca Creek merge with the Quaternary deposits in the Missouri River valley. In places where the Niobrara formation, the Pierre shale, or the Brule formation is at the surface or is mantled by thin deposits of the Ogallala or thin deposits of Quaternary age, only meager amounts of ground water can be obtained unless wells are deep enough to tap the Dakota sandstone. Elsewhere the Ogallala formation and the deposits of Quaternary age generally yield ample water for domestic and stock supplies, and in some places, notably in the vicinity of Ainsworth, they yield enough water for irrigation. Additional large supplies of ground water could be obtained on the upland in the southwestern and west-central parts of the area. The report contains an annotated bibliography of previous publications on the geology and ground-water resources of the area, brief descriptions of the Cretaceous, Tertiary, and Quaternary rocks, a map showing the contour of the water table, logs of test holes and wells not published elsewhere, results of analyses of ground- and surface-water samples, and records of all wells of large discharge and representative wells of small discharge.

Nebraska, North Dakota↗

USGS1979

Ground-water quality in Bannock, Bear Lake, Caribou, and part of Power counties, southeastern Idaho

This report provides information about the current quality of ground waters in southeastern Idaho and discusses the natural and manmade environmental controls on that quality. This information will be useful in planning and monitoring the development and use of the ground-water resources of southeastern Idaho. The southeastern corner of Idaho, as described in this report, encompasses an area of about 4,000 mil in Bannock, Bear Lake, Caribou, and part of Power Counties. The popu- lation of the area in 1975, based on best estimates by the Idaho Division of Budget, Policy Planning, and Coordination (1976) was 75,200. About 80 percent of the population is in and near the city of Pocatello, which is the second largest population center in the State. Pocatello's economy depends largely on manufacturing and industrial processing, which includes chemicalfertilizer plants. The econ- omy in the rural areas depends largely on agriculture--both dry and irrigated farming are practiced. Mining is important and expected to dominate the economy in the eastcentral part of the area in the future. Natural resources include phosphate ore, which makes up about 35 percent of the U.S. reserves (U.S. Department of Interior and U.S. Department of Agriculture, 1977); ground water, which mostly underlies the several intermontane valleys that dissect the area; and hot springs, which indicate that geothermal energy sources may underlie part of the area. Also, current (1978) speculation is that petroleum reserves may be present in the vicinity of Bear Lake. Development of more sprink- ler-irrigated lands, increases in population, and growth of phosphate mining are expected to place stress on the ground-water resources, both in quality and quantity. The purpose of this report is to present the results of a study whose primary objectives were (1) to provide current waterquality data representative of the water in several different aquifers (water- bearing formations) in the study area, and (2) to relate these data to natural and manmade environmental controls. The wells sampled during this study establish a quasi-network, which could be resampled in the future to document and analyze changes (if any) in ground-water quality. Based on this information, planners and water managers could better understand the causeand-effect relations controlling water quality and could better manage land and water-resource development. The report is designed for ease of reading and presentation. It uses maps, tables, and abbreviated text to describe geology, hydrology, and ground-water quality and how they are interrelated. Some practical ways for improving water quality are discussed for the benefit of individual water users. The field data collected in making the study are contained in the Data Section of this report. The authors gratefully acknowledge the many individual well owners, municipal officials, and private industries that provided well information and allowed access to their properties and collection of water samples. Without their help, this work could not have been done. Water samples were collected at 103 well sites. Waterlevel measurements were made at 98 of these sites during July, August, and September of 1976. This study was made by the U.S. Geological Survey in cooperation with the Idaho Department of Water Resources. A similar study is being made (1978) in north Idaho. Other studies are planned, specifically to obtain ground-water-quality data in areas where land and water-resource development is expected or accelerating.

Idaho↗

USGS1978

Summary appraisals of the nation's ground-water resources – Great Lakes region

The Great Lakes Regions, as a whole, has abundant supplies of water. Nearly 805,000 billion cubic feet of water is contained in the Great Lakes. An additional 35,000 billion cubic feet of potable ground water is available from storage in the region. Estimated ground-water discharge to the streams and lakes of the region is 26 billion gallons per day. Despite this abundance of water, the United States part of the Great Lakes basin is faced with many water-related problems, most of which involve water quality and water supply. Other problems concern periods of low flow in streams, preservation of wetlands, detrimental effects of erosion, and flooding. The significance of ground water in these problems is often overlooked. Ground water can be an alternative to surface water as a source of supply, or it can be used conjunctively with surface water to provide flexibility in water-supply management. Ground water supplied approximately 1,800 million gallons per day of the 39,900 million gallons. per day used in the Great Lakes Region in 1970. The ground-water contribution was only 4.5 percent of the water used. Thus, ground water represents a potential source of supply for much of the region. It also can be used, where conditions permit, to maintain lake levels and flow in streams, to dilute poor quality surface water, and to maintain or create wetlands and ponds. In managing water resources, ground water and surface water should be considered parts of a single system. Management includes not only planning and controlling the development but also monitoring the effects of this development. Recent advances in ground-water hydrology have provided methods to resolve some of the development and management questions that formerly slowed the development of ground water. All of the States in the Great Lakes Region have some regulations to control the development or protect the quality of the ground water. These regulations, however, are not as comprehensive as those governing surface water. Future legislation could be designed to encourage the development of ground water and, at the same time, to protect the resource. Efficient development and management of ground-water resources requires a through knowledge of the system. Reports on ground water are available for about 80 percent of tbe Great Lakes Region. Most of these reports, however, are not sufficiently detailed to be useful in comprehensive planning. As ground-water development continues, quantitative groundwater studies, utilizing models as predictive tools, will enable this development to proceed in an efficient manner.

Illinois, Indiana, Michigan, Minnesota, New York, ↗

USGS1963

Ground-water data: Beaver, Escalante, Cedar City, and Parowan Valleys; parts of Washington, Iron, Beaver, and Millard Counties, Utah

This report is intended to serve two purposes: (1) to make available to the public basic ground-water data useful in planning and studying development of water resources, and (2) to supplement an interpretive report that will be published later. Records were collected during the period 1935-62 by the U.S. Geological Survey in cooperation with the Utah State Engineer as part of the investigation of ground-water conditions in the Beaver, Escalante, Cedar City, and Parowan Walleys. This report will include records collected subsequent to data published in earlier reports listed in the bibliography. The interpretive material will be published in a companion report by George W. Sandberg. This report is most useful in predicting conditions likely to be found in areas that are being considered as well sites. The person considering the new well can spot the proposed site on plate 1 and examine the records of nearby wells as shown in the tables and figure 2. From table 1 he can note such things as diameter, depth, water level, yield, use of water, and depth to aquifers in wells in the vicinity, and from the well logs in table 3 he can note the type of material that yields water to the wells. Table 2 gives several years record of yields and pumping levels of irrigation wells, and in table 4 are the chemical analyses of water from wells and springs. Figure 2 shows the historic fluctuations and trends of water levels in the four valleys. If the reader decides from his examination that conditions are favorable, he can place an application to drill a well with the State Engineer. During the past several years, however, the State Engineer has rejected new applications to appropriate water in major portions of Beaver Valley, Milford and Beryl-Enterprise districts in Escalante Valley, and Cedar City Valley. Anyone seeking to initiate a new ground-water right in any of these areas should obtain information from the State Engineer's Office in either Salt Lake City or Cedar City to determine the likelihood of approval of the required application. The report is also useful when planning large-scale developments of water supply. This and other uses of the report will be helped by use of the interpretive report upon its release.

Utah↗

USGS1995

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1992 through June 1994

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data are presented from January 1992 through June 1994. This report concentrates on data from 1994, and references historic data from 1992 and 1993. Total rainfall for the first half of 1994 was 51 inches which is 48 percent of the mean annual rainfall of 106 inches. In comparison, total rainfall for the first six months of 1993 and 1992 was 56 inches and 51 inches, respectively. Annual rainfall totals in 1993 and 1992 were 95 inches and 93 inches, respectively. Ground-water withdrawal has averaged 975,000 gallons per day through June 1994, while withdrawals in 1993 and 1992 averaged 954,000 gallons per day and 936,000 gallons per day, respectively. In each of the five areas of ground- water production, withdrawals have remained steady since 1991. At the end of June 1994, the chloride concentration of the composite water supply was 68 milligrams per liter, well below the 250 milligrams per liter secondary drinking water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from January through June 1994 ranged between 37 and 90 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations have increased very slightly since March 1994 coinciding with the start of the dry season. There has been a general trend of increasing chloride concentrations in the deeper monitoring wells since the 1992 dry season, which began in March 1992. A fuel spill at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water-supply purposes in April 1992. The remaining six wells are being used to hydraulically contain and divert fuel migration.

Open-File Report↗

USGS1995

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1992 through September 1994

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data are presented from January 1992 through September 1994. This report concentrates on data from July through September 1994, and references historic data from 1992 through June 1994. Total rainfall for the first nine months of 1994 was about 77 inches which is 72 percent of the mean annual rainfall of 106 inches. In comparison, total rainfall for the first nine months of 1992 and 1993 was 67 inches and 69 inches, respectively. Annual rainfall totals in 1992 and 1993 were 93 inches and 95 inches, respectively. Ground-water withdrawal during July through September 1994 has averaged 919,400 gallons per day, while annual withdrawals in 1992 and 1993 averaged 935,900 gallons per day and 953,800 gallons per day, respectively. At the end of September 1994, the chloride concentration of the composite water supply was 56 milligrams per liter, well below the 250 milligrams per liter secondary drinking-water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from July through September 1994 ranged between 51 and 78 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations increased in July and August, but have leveled off or decreased in September. There has been a general trend of increasing chloride concentrations in the deeper monitoring wells since the 1992 dry season, which began in March 1992. A fuel leak at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water-supply purposes in April 1992. The remaining six wells are being used to hydraulically contain and divert fuel migration by recirculating 150,000 gallons of water each day.

Open-File Report↗

USGS1995

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1992 through December 1994

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data presented are from January 1992 through December 1994. This report concentrates on data from October through December 1994, and references previous data from 1992 through 1994. Cumulative rainfall for October through December 1994 was 55 inches which is higher than the mean cumulative rainfall of about 31 inches for the same 3 months. Total rainfall for 1994 was 131 inches which is 24 percent higher than the mean annual rainfall of 106 inches. In com- parison, total rainfall in 1992 and 1993 were 93 inches and 95 inches, respectively. Ground-water withdrawal during October through December 1994 averaged 903,000 gallons per day, while the annual withdrawal in 1994 was 942,700 gallons per day. Annual withdrawals in 1992 and 1993 averaged 935,900 gallons per day and 953,800 gallons per day, respectively. At the end of December 1994, the chloride concentration of the composite water supply was 28 milligrams per liter, well below the 250 milligrams per liter secondary drinking-water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from October through December 1994 ranged between 28 and 86 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations decreased in November and December, and seems to have leveled off by the end of the year. Although chloride concen- trations have decreased during the fourth quarter of 1994, there has been a general trend of increasing chloride concentrations in the deeper monitoring wells since the 1992 dry season, which began in March 1992. A fuel leak at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water-supply purposes in April 1992. The remaining six wells are being used to hydraulically contain and divert fuel migration by recirculating 150,000 gallons of water each day.

Open-File Report↗

USGS1996

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1993 through September 1995

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data presented are from January 1993 through September 1995, although the report focuses on hydrologic events from July through September 1995. Cumulative rainfall for July through September 1995 was about 15 inches which is 32 percent less than the mean cumulative rainfall of about 22 inches for July through September. July and August are within the annual dry season, while September is the start of the annual wet season. Mean cumulative rainfall is calculated for the fixed base period 1951-90. Ground-water withdrawal during July through September 1995 averaged 888,500 gallons per day. Withdrawal for the same 3 months in 1994 averaged 919,400 gallons per day. Patterns of withdrawal during the third quarter of 1995 did not change significantly since 1993 at all five ground-water production areas. At the end of September 1995, the chloride concentration of the composite water supply was 51 milligrams per liter, well below the 250 milligrams per liter secondary drinking-water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from July through September 1995 ranged between 42 and 68 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations continued to increase since April 1995, with water from the deepest monitoring wells increasing in chloride concentration by as much as 2,000 milligrams per liter. A fuel leak at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water-supply purposes in April 1992. The remaining six wells are being used to hydraulically divert fuel migration away from water-supply wells by recirculating about 150,000 gallons of water each day.

Open-File Report↗

USGS1995

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1993 through June 1995

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data presented are from January 1993 through June 1995, although the report focuses on hydrologic events from April through June 1995. Cumulative rainfall for April through June 1995 was about 14 inches which is 70 percent of the mean cumulative rainfall of about 20 inches for the same 3 months in a year. April through June is within the annual dry season. Rainfall for each month was below average from the respective mean monthly rainfall. All mean rainfall values are calculated for the fixed base period 1951-90. Ground-water withdrawal during April through June 1995 averaged 833,700 gallons per day. Withdrawal for the same 3 months in 1994 averaged 950,000 gallons per day. At the end of June 1995, the chloride concentration of the composite water supply was 57 milligrams per liter, well below the 250 milligrams per liter secondary drinking-water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from April through June 1995 ranged between 26 and 62 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations increased since April 1995, with water from the deepest monitoring wells increasing in chloride concentra- tion by about 1000 milligrams per liter. A fuel leak at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water-supply purposes in April 1992. The remaining six wells are being used to hydraulically contain and divert fuel migration away from water-supply wells by recirculating about 150,000 gallons of water each day.

Open-File Report↗

USGS1983

Injection of treated wastewater for ground-water recharge in the Palo Alto Baylands, California, hydraulic and chemical interactions — Preliminary report

An injection-extraction well network in the Palo Alto Baylands along the San Francisco Bay, California, was designed to flush the shallow aquifer system of saline water and prevent further inland saline contamination. Clogging processes and solution migration in the vicinity of one injection well were studied. Cyclic evaporative concentration of bay water and infiltration have generated a concentrated ground-water brine. Montmorillonite and illite are the primary clay minerals present in the shallow aquifer system. X-ray diffraction analysis of these clays showed a marked increase in the d-spacing of the crystal lattice when native hypersaline pure water was replaced by injection water. Chloride:magnesium and chloride:potassium ratios in the aquifer system changed during injection, most likely due to ionic exchange reaction. Similar variations in chloride:boron, chloride:iron, and chloride:manganese ratios probably resulted from reduction-oxidation reactions. Ground-water quality appears to have been chiefly affected by the processes of dilution and dispersion. Extraction pump test data yielded a transmissivity value of 960 feet squared per day and a storage coefficient of 0.0005. Vertical permeability of the upper confining layer is 0.08 feet per day.

California↗

USGS1995

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data, January 1993 through March 1995

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data presented are from January 1993 through March 1995, although the report focuses on hydrologic events from January through March 1995. Cumulative rainfall for January through March 1995 was about 42 inches which is higher than the mean cumulative rainfall of about 33 inches for the same 3 months in a year. January and February are part of the annual wet season and March is the start of the annual dry season. Rainfall for each month was above average from the respective mean monthly rainfall. Ground- water withdrawal during January through March 1995 averaged 894,600 gallons per day. Withdrawal for the same 3 months in 1994 averaged 999,600 gallons per day. At the end of March 1995, the chloride concentration of the composite water supply was 26 milligrams per liter, well below the 250 milligrams per liter secondary drinking-water standard established by the U.S. Environmental Protection Agency. Chloride concentrations of the composite water supply from January through March 1995 ranged between 19 and 49 milligrams per liter. Chloride concentration of ground water in monitoring wells at Cantonment and Air Operations decreased since November 1994. The deepest monitoring wells show declines in chloride concentration by as much as 4,000 milligrams per liter. A fuel leak at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells resumed pumping for water- supply purposes in April 1992. The remaining six wells are being used to hydraulically contain and divert fuel migration by recirculating about 150,000 gallons of water each day.

Open-File Report↗

USGS1993

Modifications to the modular three-dimensional finite-difference ground-water flow model used for the Columbia Plateau Regional Aquifer-System Analysis, Washington, Oregon, and Idaho

The report documents modifications to the U.S. Geological Survey's modular three-dimensional finite-difference ground-water flow model used for a regional aquifer-system analysis of the Columbia Plateau. The report, which describes the concepts and mathematical basis for the modifications, is intended for potential users who are familiar with the original modular model. The modifications permit flow from a layer to any adjacent layer, allow the model to retain a cell of a layer that has been cut completely through by a canyon, and allow placing ground-water flow barriers on only specified branch conductances; a special version of the modified model uses a convergent grid. The report describes the data-input items that this modified model must read.

Open-File Report↗

USGS1996

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania: Characterization of surface-runoff and ground-water quantity and quality in a small carbonate basin near Churchtown, Pennsylvania, prior to terracing and implementation of nutrient management: Water-quality study of the Conestoga River headwaters, Pennsylvania

The U.S. Geological Survey, in cooperation with the Pennsylvania Department of Environmental Protection1 , conducted a study as part of the U.S. Department of Agriculture's Rural Clean Water Program to determine the effects of agricultural best-management practices on surface-water and ground-water quality in the Conestoga River headwaters basin. This report describes Field-Site 1 and characterizes the surface-runoff and ground-water quantity and quality at the site from January 1983 through September 1984, before the implementation of terracing and nutrient-management best-management practices. The 22.1-acre site, part of two dairy farms, was cropland used primarily for the production of corn and alfalfa, and is underlain by carbonate rock. During the 21-month study period, 91.2 inches of precipitation fell, of which 66 percent occurred during the 1984 water year. Of the 169 storms of 0.10 inch or larger, 97 produced measurable runoff. The average annual application of nutrients to the 14.4 acres of cornfields was 410 pounds per acre of nitrogen and 110 pounds per acre of phosphorus. About three times more nutrients were applied during 1984 water year than during the 1983 water year. The approximate soil-nitrate concentration as nitrogen for the study period was 8.2 milligrams per kilogram in the top 8 inches of soil. Runoff for the study period totalled 714,000 cubic feet, or 9.8 percent of total precipitation. Eighty-eight percent of the runoff occurred during the 1984 water year. Regression analyses indicate that total runoff was controlled primarily by total precipitation amounts during storms and by antecedent moisture conditions; mean event and maximum instantaneous discharges are controlled by precipitation intensity and by antecedent moisture conditions. Regression analyses also suggest that crop cover on the corn acreage affected runoff amounts and rates. Mean concentrations in runoff ranged from 24 to 73,000 milligrams per liter for suspended sediment, 0.45 to 24 milligrams per liter for total phosphorus, and 1.5 to 55 milligrams per liter for total nitrogen. Of the total nitrogen in instantaneous runoff samples, a median of 72 percent was total organic nitrogen. Results of multiple regression analyses suggest that mean nitrogen concentrations in runoff (1) increased with increased surface-nitrogen applications made prior to runoff, and (2) were diluted with increased precipitation duration. Runoff from storms on frozen ground produced the highest loads of nitrogen in runoff. Over the 21-month study period, an estimated 258 tons of suspended sediment, 314 pounds of nitrogen, and 176 pounds of phosphorus were transported with runoff from the site. Of this, 88 percent of the nitrogen and phosphorus loads and 94 percent of the suspended-sediment load were discharged during the wet 1984 water year. The loads for the study period represent 2.5 percent of the total nitrogen and 5.5 percent of the total phosphorus applied to the site as manure and commercial fertilizer. The ground-water basin at the site is slightly larger than the surface-water basin. Ground-water levels, except at one well, responded quickly to recharge; water levels peaked several hours to a day after precipitation. Surface-applied materials moved rapidly to the water table through macropores and slowly by transport through micropores in the unsaturated zone. Median concentrations of dissolved nitrate ranged from 9.2 to 13 milligrams per liter as nitrogen for ground-water samples collected monthly from five wells and a spring. Dissolved nitrate comprised 93 percent (median percentage) of the total nitrogen in ground-water samples. The effect of recharge on ground-water nitrate concentrations was affected by variations in nutrient availability at the land surface and in the unsaturated zone. A lag time of 1 to 3 months was observed between the time that nitrogen was applied to the land surface and local maximums in nitrate concentrations were detected in ground water unaffected by recharge events. Approximately 3,187,000 cubic feet of ground water and an associated 2,200 pounds of nitrate-nitrogen discharged from the site during the study period. For the study period, 42 percent of the precipitation recharged to ground water, 10 percent became runoff, and 48 percent evapotranspired. Inputs of nitrogen to the study area were estimated to be 93 percent from manure, 5 percent from commercial fertilizer, and 2 percent from precipitation. Nitrogen outputs from the system were estimated to be 38 percent to crop uptake, 39 percent to volatilization, 20 percent to ground-water discharge, and 3 percent to surface runoff.

Pennsylvania↗

USGS2001

Ground-Water Hydrology of the Upper Deschutes Basin, Oregon

The upper Deschutes Basin is among the fastest growing regions in Oregon. The rapid population growth has been accompanied by increased demand for water. Surface streams, however, have been administratively closed to additional appropriation for many years, and surface water is not generally available to support new development. Consequently, ground water is being relied upon to satisfy the growth in water demand. Oregon water law requires that the potential effects of ground-water development on streamflow be evaluated when considering applications for new ground-water rights. Prior to this study, hydrologic understanding has been insufficient to quantitatively evaluate the connection between ground water and streamflow, and the behavior of the regional ground-water flow system in general. This report describes the results of a hydrologic investigation undertaken to provide that understanding. The investigation encompasses about 4,500 square miles of the upper Deschutes River drainage basin.A large proportion of the precipitation in the upper Deschutes Basin falls in the Cascade Range, making it the principal ground-water recharge area for the basin. Water-balance calculations indicate that the average annual rate of ground- water recharge from precipitation is about 3,500 ft3/s (cubic feet per second). Water-budget calculations indicate that in addition to recharge from precipitation, water enters the ground-water system through interbasin flow. Approximately 800 ft3/s flows into the Metolius River drainage from the west and about 50 ft3/s flows into the southeastern part of the study area from the Fort Rock Basin. East of the Cascade Range, there is little or no ground-water recharge from precipitation, but leaking irrigation canals are a significant source of artificial recharge north of Bend. The average annual rate of canal leakage during 1994 was estimated to be about 490 ft3/s. Ground water flows from the Cascade Range through permeable volcanic rocks eastward out into the basin and then generally northward. About one-half the ground water flowing from the Cascade Range discharges to spring-fed streams along the margins of the range, including the upper Metolius River and its tributaries. The remaining ground water flows through the subsurface, primarily through rocks of the Deschutes Formation, and eventually discharges to streams near the confluence of the Deschutes, Crooked, and Metolius Rivers. Substantial ground-water discharge occurs along the lower 2 miles of Squaw Creek, the Deschutes River between Lower Bridge and Pelton Dam, the lower Crooked River between Osborne Canyon and the mouth, and in Lake Billy Chinook (a reservoir that inundates the confluence of the Deschutes, Crooked, and Metolius Rivers).The large amount of ground-water discharge in the confluence area is primarily caused by geologic factors. North (downstream) of the confluence area, the upper Deschutes Basin is transected by a broad region of low-permeability rock of the John Day Formation. The Deschutes River flows north across the low-permeability region, but the permeable Deschutes Formation, through which most of the regional ground water flows, ends against this rampart of low-permeability rock. The northward-flowing ground water discharges to the streams in this area because the permeable strata through which it flows terminate, forcing the water to discharge to the surface. Virtually all of the regional ground water in the upper Deschutes Basin discharges to surface streams south of the area where the Deschutes River enters this low-permeability terrane, at roughly the location of Pelton Dam.The effects of ground-water withdrawal on streamflow cannot presently be measured because of measurement error and the large amount of natural variability in ground-water discharge. The summer streamflow near Madras, which is made up largely of ground-water discharge, is approximately 4,000 ft3/s. Estimated consumptive ground-water use in the basin i

Water-Resources Investigations Report↗

USGS1996

Documentation of model input and output values for the simulation of the ground-water flow system in the Cretaceous-age Coastal Plain aquifers of South Carolina

This report and the attached 3 1/2-inch diskette contain, in compressed format, the data sets for the model of ground-water flow in the Cretaceous-age Coastal Plain aquifers of South Carolina. The data sets can be uncompressed using a program provided with this report. The uncompressed files require approximately 3.7 megabytes of disk space on an IBM-compatible microcomputer1 using the MS-DOS operating system. All files are in American Standard Code for Information Interchange format.

South Carolina↗

USGS1995

Status of ground-water resources at U.S. Navy Support Facility, Diego Garcia; summary of hydrologic and climatic data through September 1993

This report contains hydrologic and climatic data that describe the status of ground-water resources at U.S. Navy Support Facility, Diego Garcia. Data are presented through September 1993, one month into the annual wet season. At the end of September 1993, the chloride concentration of the composite water supply was 66 milligrams per liter, well below the 250 milligrams per liter secondary drinking water standard established by the U.S. Environmental Protection Agency. Most of the production wells appeared to be operating at levels consistent with past operations. Several wells at Air Operations remain out of service while they are being used to hydraulically divert the nearby fuel spill. Rainfall thus far in 1993 is 8 percent below the mean annual rainfall of 106 inches. This follows a year when rainfall was 12 percent below the mean annual rainfall. Withdrawal has averaged 856,000 gallons per day during 1993, a decrease from the 1992 average of 936,000 gallons per day. The chloride concentration of pumped water rose during the current quarter (July through September 1993) in most areas, coincident with the annual dry season (March through August). This continues a general trend of increasing chloride concentration that has persisted for more than a year, beginning in the 1992 dry season. Chloride concentration rose progressively during the current quarter in monitoring wells at Cantonment and Air Operations. Chloride concentrations in the deeper monitoring wells have generally been increasing since 1992. A fuel spill at Air Operations caused the shutdown of ten wells in May 1991. Four of the wells have resumed pumping to the water supply, but water from the remaining six wells is being used to hydraulically contain and divert fuel migration.

Open-File Report↗