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At least 1,135 records · Page 63Linked to original sources
USGS1974

Summary appraisals of the nation's ground-water resources – Upper Colorado region

The Upper Colorado Region covers about 113,500 square miles (293,965 km 2 ) in parts of Arizona, Colorado, New Mexico, Utah, and Wyoming. Drainage from about 97 percent of the region is to the Colorado River. About 60 percent of the land is owned or administered by the Federal Government, and another 15 percent is in Indian trust. The predominantly arid to semiarid region is sparsely populated (averaging about three persons per square mile, or about two and one-half persons per km 2 ) and is used chiefly for grazing, recreation, and mineral development. The water supply for the region comes from precipitation within the region, which averages about 95 million acre-feet (117,182.5 hm 3 ) per year. Development of the region's water supply has been limited almost entirely to surface water. Only about 2 percent of the total estimated volume of water withdrawn (about 5.7 million acre-ft, or 7,030.9 hm 3 ) and consumed (about 3.6 million acre-ft, or 4,440.6 hm 3 ) in the region in 1970 came directly from ground-water sources. By the year 2020 consumptive use of water within the region and water exports to adjacent regions are expected to total more than 6.5 million acre-feet (8,017.8 hm 3 ) per year. Use of the ground-water resources of the Upper Colorado Region in water-resources management can help to meet these water needs. A tremendous amount of water is stored in the rocks (ground-water reservoirs) of the Upper Colorado Region. Recoverable water in just the upper 100 feet (30.5 m) of saturated rocks is estimated to be as much as 115 million acre-feet (141,852.5 hm 3 ). That amount is nearly four times the total active storage capacity of all surface-water reservoirs in the region. The average annual replenishable supply of the ground-water reservoir is about 4 million acre-feet (4,934 hm 3 ). This amount of water could irrigate about 1.3 million acres (526,1,10 ha) of crops having an annual water requirement of 3 feet per acre (0.9 m/ha), or it could provide about 3,600 million gallons (13,627,440 m 3 ) per day for industrial use. Most of the ground water is in consolidated rocks, which generally yield water to wells slowly. Much of the ground water is saline and, in some places, occurs at great depths. Nevertheless, the ground water is more uniformly distributed than is surface water, both areally and with time; therefore, it can be used advantageously in overall waterresources management. Recent advancements in the field of demineralization and in evaluation and development of ground water make this possible. Options available for use of ground water in water-resources management·in the·region include conjunctive use with surface water or development of ground water as an independent supply. The latter option could be for & perennial supply or for a time-limited supply (mining ground water), depending on the need and the existing ground-water conditions. All options can be carried out so as to meet the requirements of the Colorado River Compact. The options could be implemented to optimally develop the Upper Colorado River Basin's allocation of Colorado River water while meeting the Compact commitments to the Lower Basin.

Arizona, Colorado, New Mexico, Utah, Wyoming↗
USGS1955

Ground-water and drainage problems in the Whitney terrace area, Boise, Idaho

Ground-water levels in the Whitney terrace area, after many years of rise owing to downward percolation of water from irrigated land, became nearly stabilized by 1935. Strong seasonal water-level fluctuations of 8 to 10 feet, however, are common in the Boise Valley. In recent years, the Whitney terrace has been changing rapidly from a farming to an urban community. The 3,200-acre area now has about 15,000 inhabitants and the land area is about 35-percent occupied by urban developments. Population trends indicate that urban expansion will continue. Coincident with the change from rural to urban conditions on the Whitney terrace, the patterns of water use were drastically altered. The amount of irrigated land has decreased but the amount of ground-water recharge from irrigation and yard water may have increased. Liquid sewage effluent disposed in the ground also has increased the yearly volume of recharge. The estimated average yearly amount of recharge from all sources now is about 2.4 acre-feet per acre. Full urban development of the area may increase recharge from all sources to about 3.3 acre-feet per acre. Ground-water and drainage problems can be relieved by reducing excessive recharge to the ground-water reservoir. Reduction can be accomplished by economical use of water by individuals, establishment of a water-tight public sewage system to transport all sewage to a central plant outside of the area, and by drainage works. These measures would cause a net decline of ground-water levels in the area. They can be undertaken separately or collectively.

Idaho↗
USGS1994

Ground-water levels and directions of flow near the Industrial Excess Landfill, Uniontown, Ohio, March 1994

Industrial Excess Landfill (IEL), a U.S. Environmental Protection Agency Superfund site, is a closed landfill in northeastern Ohio. In March 1994, personnel from the U.S. Geological Survey, Ohio Environmental Protection Agency, and PRC Environmental Management, Inc., measured water levels in 149 wells in the area. Surface-water altitudes were measured at 13 staff gages, and water levels were measured in 9 piezometers associated with the gages. The data show that the regional pattern of ground-water flow generally is from east to west, but it is locally altered by ground-water mounds that reflect the hummocky terrain. At the landfill, regional flow is altered by two ground-water mounds one in the southeastern corner of the site and one just to the north. The relatively small ground-water mound at the landfill causes ground water to flow radially away from the southeastern corner of the landfill. Ground water that flows to the east and south flows toward Metzger Ditch, whereas flow to the west is consistent with the regional direction of ground-water flow. Ground-water flow northward from IEL is diverted east or west by the southerly component of flow from the larger ground-water mound north of IEL.

Ohio↗
USGS2003

MTBE concentrations in ground water in Pennsylvania

The distribution, concentrations, and detection frequency of methyl tert-butyl-ether (MTBE), a gasoline additive used in reformulated gasoline to improve air quality, were characterized in Pennsylvania's ground water. Two sources of MTBE in ground water, the atmosphere and storage-tank release sites, were examined. An analysis of atmospheric MTBE concentrations shows that MTBE detections (MTBE greater than or equal to 0.2 micrograms per liter) in ground water are more likely the result of storage-tank releases than atmospheric deposition. A comparison of 86 ground-water samples near storage-tank releases and 359 samples from ambient ground water (not thought to be affected by point-source releases of MTBE or BTEX compounds) shows that samples within about 0.5 mile downgradient of storagetank release sites have significantly greater MTBE detection frequency than ambient ground-water samples. Aquifer type, land use, and the use of Reformulated Gasoline (RFG) are associated with high rates of occurrence of MTBE in ground water in Pennsylvania. Ground-water samples from wells in crystalline-rock aquifers near storage- tank release sites have a significantly greater MTBE detection frequency (57 percent) compared to other aquifers. Samples from wells in urban areas have a significantly greater MTBE detection frequency compared to ambient samples in agricultural and forested areas. Samples from the RFG-use areas in the five southeastern counties of Pennsylvania have a significantly greater MTBE detection frequency than samples outside of the RFG-use area. MTBE detection frequency of samples near storage-tank release sites in the RFG-use area (45 percent) are significantly greater than ambient samples in the RFG-use area.

Pennsylvania↗
USGS1983

Ground water in north Monterey County, California, 1980

Present ground-water demands exceed long-term recharge throughout much of North Monterey County in the shallow Quaternary deposits--principally the upper part of the Aromas Sand--and the overlying alluvium. Recharge occurs largely from local precipitation, although small quantities of potable ground water from outside areas also recharge these aquifers. Water levels in the Pajaro and Salinas River valleys north and south of the study area are lower than most of the intervening area, and recharge from the east is blocked by faults and impervious rock. Ocean water moves in from the west to replace depleted freshwater storage in the upper part of the Aromas Sand, alluvium, and terrace deposits. The North County area was divided into subareas to estimate pumpage demands and to evaluate ground-water yields. Pumpage near the granitic ridge, an area of limited storage, nearly matches local recharge. West of the granitic ridge, pumpage exceeds available recharge but draws upon a large storage potential. Deeper units than those now tapped by wells in the Aromas Sand and the underlying Purisima Formation may have substantial water-bearing potential for additional ground-water development. Extensive development of water from these formations might be limited, however, by the remoteness of the recharge source and by the proximity to the ocean. (USGS)

Water-Resources Investigations Report↗
USGS2007

Ground-Water Quality of the Northern High Plains Aquifer, 1997, 2002-04

An assessment of ground-water quality in the northern High Plains aquifer was completed during 1997 and 2002-04. Ground-water samples were collected at 192 low-capacity, primarily domestic wells in four major hydrogeologic units of the northern High Plains aquifer-Ogallala Formation, Eastern Nebraska, Sand Hills, and Platte River Valley. Each well was sampled once, and water samples were analyzed for physical properties and concentrations of nitrogen and phosphorus compounds, pesticides and pesticide degradates, dissolved solids, major ions, trace elements, dissolved organic carbon (DOC), radon, and volatile organic compounds (VOCs). Tritium and microbiology were analyzed at selected sites. The results of this assessment were used to determine the current water-quality conditions in this subregion of the High Plains aquifer and to relate ground-water quality to natural and human factors affecting water quality. Water-quality analyses indicated that water samples rarely exceeded established U.S. Environmental Protection Agency public drinking-water standards for those constituents sampled; 13 of the constituents measured or analyzed exceeded their respective standards in at least one sample. The constituents that most often failed to meet drinking-water standards were dissolved solids (13 percent of samples exceeded the U.S. Environmental Protection Agency Secondary Drinking-Water Regulation) and arsenic (8 percent of samples exceeded the U.S. Environmental Protection Agency Maximum Contaminant Level). Nitrate, uranium, iron, and manganese concentrations were larger than drinking-water standards in 6 percent of the samples. Ground-water chemistry varied among hydrogeologic units. Wells sampled in the Platte River Valley and Eastern Nebraska units exceeded water-quality standards more often than the Ogallala Formation and Sand Hills units. Thirty-one percent of the samples collected in the Platte River Valley unit had nitrate concentrations greater than the standard, 22 percent exceeded the manganese standard, 19 percent exceeded the sulfate standard, 26 percent exceeded the uranium standard, and 38 percent exceeded the dissolved-solids standard. In addition, 78 percent of samples had at least one detectable pesticide and 22 percent of samples had at least one detectable VOC. In the Eastern Nebraska unit, 30 percent of the samples collected had dissolved-solids concentrations larger than the standard, 23 percent exceeded the iron standard, 13 percent exceeded the manganese standard, 10 percent exceeded the arsenic standard, 7 percent exceeded the sulfate standard, 7 percent exceeded the uranium standard, and 7 percent exceeded the selenium standard. No samples exceeded the nitrate standard. Thirty percent of samples had at least one detectable pesticide compound and 10 percent of samples had at least one detectable VOC. In contrast, the Sand Hills and Ogallala Formation units had fewer detections of anthropogenic compounds and drinking-water exceedances. In the Sand Hills unit, 15 percent of the samples exceeded the arsenic standard, 4 percent exceeded the nitrate standard, 4 percent exceeded the uranium standard, 4 percent exceeded the iron standard, and 4 percent exceeded the dissolved-solids standard. Fifteen percent of samples had at least one pesticide compound detected and 4 percent had at least one VOC detected. In the Ogallala Formation unit, 6 percent of water samples exceeded the arsenic standard, 4 percent exceeded the dissolved-solids standard, 3 percent exceeded the nitrate standard, 2 percent exceeded the manganese standard, 1 percent exceeded the iron standard, 1 percent exceeded the sulfate standard, and 1 percent exceeded the uranium standard. Eight percent of samples collected in the Ogallala Formation unit had at least one pesticide detected and 6 percent had at least one VOC detected. Differences in ground-water chemistry among the hydrogeologic units were attributed to variable depth to water, depth of the well screen below the water table, reduction-oxidation conditions, ground-water residence time, interactions with surface water, composition of aquifer sediments, extent of cropland, extent of irrigated land, and fertilizer application rates.

Scientific Investigations Report↗
USGS1996

Hydrogeology and simulation of ground-water flow, Picatinny Arsenal and vicinity, Morris County, New Jersey

Ground-water flow in glacial sediments and bedrock at Picatinny Arsenal, N.J., was simulated by use of a three-dimensional finite-difference ground- water-flow model. The modeled area includes a 4.3-square-mile area that extends from Picatinny Lake to the Rockaway River. Most of the study area is bounded by the natural hydrologic boundaries of the ground-water system. eophysical logs, lithologic logs, particle-size data, and core data from selected wells and surface geophysical data were analyzed to define the hydrogeologic framework. Hydrogeologic sections and thickness maps define six permeable and three low-permeability layers that are represented in the model as aquifers and confining units, respectively. Hydrologic data incorporated in the model include a rate of recharge from precipitation of 22 inches per year, estimated from long-term precipitation records and estimates of evapotranspiration. Additional recharge from infiltration along valleys was estimated from measured discharge of springs along the adjacent valley walls and from estimates of runoff from upland drainage that flows to the valley floor. Horizontal and vertical hydraulic conductivities of permeable and low-permeability layers were estimated from examination of aquifer-test data, gamma-ray logs, borehole cuttings, and previously published data. Horizontal hydraulic conductivities in glacial sediments range from 10 to 380 feet per day. Vertical hydraulic conductivities of the low-permeability layers range from 0.01 to 0.7 feet per day. The model was calibrated by simulating steady-state conditions during 1989-93 and by closely matching simulated and measured ground-water levels, vertical ground-water-head differences, and streamflow gain and loss. Simulated steady-state potentiometric- surface maps produced for the six permeable layers indicate that ground water in the unconfined material within Picatinny Arsenal flows predominantly toward the center of the valley, where it discharges to Green Pond Brook. Beneath the upper confining unit, ground water flows southwestward, down the valley. Between First Street and Farley Avenue, the upper confining unit pinches out near the valley walls, resulting in a major input of water to, and causing a local potentiometric high in, the underlying aquifer layers. Ground-water-flow directions southwest of the southern arsenal boundary are predominantly to the Rockaway River.

New Jersey↗
USGS2000

Ground Water Atlas of the United States

Preface The Ground Water Atlas of the United States presents a comprehensive summary of the Nation's ground-water resources and is a basic reference for the location, geography, geology, and hydrologic characteristics of the major aquifers in the Nation. The information was collected by the U.S. Geological Survey and other agencies during the course of many years of study. Results of the Regional Aquifer-System Analysis Program, a systematic study of the Nation's major aquifers by the U.S. Geological Survey, were used as a major, but not exclusive, source of information of the Atlas. The Atlas, which is designed in a graphical format that is supported by descriptive discussions, includes 13 chapters, each representing areas that collectively cover the 50 States and Puerto Rico, as well as the U.S. Virgin Islands. Each chapter of the Atlas presents and describes hydrogeologic and hydrologic conditions for the major aquifers in each regional area. The scale of the Atlas does not allow portrayal of minor features of the geology or hydrology of each aquifer presented, nor does it include detailed discussion of minor aquifers. Those readers who seek detailed local information for the aquifers will find extensive lists of references at the end of each chapter. The introductory chapter in this volume presents an overview of ground-water conditions Nationwide and gives an example of an aquifer in each of six hydrogeologic settings.

Hydrologic Atlas↗
USGS1996

Shallow ground-water quality beneath a major urban center: Denver, Colorado, USA

A survey of the chemical quality of ground water in the unconsolidated alluvial aquifer beneath a major urban center (Denver, Colorado, USA) was performed in 1993 with the objective of characterizing the quality of shallow ground-water in the urban area and relating water quality to land use. Thirty randomly selected alluvial wells were each sampled once for a broad range of dissolved constituents. The urban land use at each well site was sub- classified into one of three land-use settings: residential, commercial, and industrial. Shallow ground-water quality was highly variable in the urban area and the variability could be related to these land-use setting classifications. Sulfate (SO4) was the predominant anion in most samples from the residential and commercial land-use settings, whereas bicarbonate (HCO3) was the predominant anion in samples from the industrial land-use setting, indicating a possible shift in redox conditions associated with land use. Only three of 30 samples had nitrate concentrations that exceeded the US national drinking-water standard of 10 mg l-1 as nitrogen, indicating that nitrate contamination of shallow ground water may not be a serious problem in this urban area. However, the highest median nitrate concentration (4.2 mg l-1) was in samples from the residential setting, where fertilizer application is assumed to be most intense. Twenty-seven of 30 samples had detectable pesticides and nine of 82 analyzed pesticide compounds were detected at low concentrations, indicating that pesticides are widely distributed in shallow ground water in this urban area. Although the highest median total pesticide concentration (0.17 ??g l-1) was in the commercial setting, the herbicides prometon and atrazine were found in each land-use setting. Similarly, 25 of 29 samples analyzed had detectable volatile organic compounds (VOCs) indicating these compounds are also widely distributed in this urban area. The total VOC concentrations in sampled wells ranged from nondetectable to 23 442 ??g l-1. Widespread detections and occasionally high concentrations point to VOCs as the major anthropogenic ground-water impact in this urban environment. Generally, the highest VOC concentrations occurred in samples from the industrial setting. The most frequently detected VOC was the gasoline additive methyl tertbutyl ether (MTBE, in 23 of 29 wells). Results from this study indicate that the quality of shallow ground water in major urban areas can be related to land-use settings. Moreover, some VOCs and pesticides may be widely distributed at low concentrations in shallow ground water throughout major urban areas. As a result, the differentiation between point and non-point sources for these compounds in urban areas may be difficult.

Journal of Hydrology↗
USGS2014

Investigations of the fluctuations of the ground‐water table in Pennsylvania

Hydraulic engineers are interested in ground ‐ water as a source of water supply and also as it affects stream‐flow. The stream‐flow is especially valuable at low stages and it is at the low stages that it is most closely related to the ground ‐ water conditions. For several years the Pennsylvania Topographic and Geologic Survey and the United States Geological Survey have cooperated in making a comprehensive study of the ground ‐ water resources of Pennsylvania , but no adequate records of ground ‐ water levels have in the past been obtained. Recently, however, a project for obtaining systematic records in Pennsylvania has been started. ©1932. American Geophysical Union.

Pennsylvania↗
USGS2007

Hydrogeology and Simulated Ground-Water Flow in the Salt Pond Region of Southern Rhode Island

The Salt Pond region of southern Rhode Island extends from Westerly to Narragansett Bay and forms the natural boundary between the Atlantic Ocean and the shallow, highly permeable freshwater aquifer of the South Coastal Basin. Large inputs of fresh ground water coupled with the low flushing rates to the open ocean make the salt ponds particularly susceptible to eutrophication and bacterial contamination. Ground-water discharge to the salt ponds is an important though poorly quantified source of contaminants, such as dissolved nutrients. A ground-water-flow model was developed and used to delineate the watersheds to the salt ponds, including the areas that contribute ground water directly to the ponds and the areas that contribute ground water to streams that flow into ponds. The model also was used to calculate ground-water fluxes to these coastal areas for long-term average conditions. As part of the modeling analysis, adjustments were made to model input parameters to assess potential uncertainties in model-calculated watershed delineations and in ground-water discharge to the salt ponds. The results of the simulations indicate that flow to the salt ponds is affected primarily by the ease with which water is transmitted through a glacial moraine deposit near the regional ground-water divide, and by the specified recharge rate used in the model simulations. The distribution of the total freshwater flow between direct ground-water discharge and ground-water-derived surface-water (streamflow) discharge to the salt ponds is affected primarily by simulated stream characteristics, including the streambed-aquifer connection and the stream stage. The simulated position of the ground-water divide and, therefore, the model-calculated watershed delineations for the salt ponds, were affected only by changes in the transmissivity of the glacial moraine. Selected changes in other simulated hydraulic parameters had substantial effects on total freshwater discharge and the distribution of direct ground-water discharge and ground-water-derived surface-water (streamflow) discharge to the salt ponds, but still provided a reasonable match to the hydrologic data available for model calibration. To reduce the uncertainty in predictions of watershed areas and ground-water discharge to the salt ponds, additional hydrogeologic data would be required to constrain the model input parameters that have the greatest effect on the simulation results.

Scientific Investigations Report↗
USGS2005

A controlled experiment in ground water flow model calibration

Nonlinear regression was introduced to ground water modeling in the 1970s, but has been used very little to calibrate numerical models of complicated ground water systems. Apparently, nonlinear regression is thought by many to be incapable of addressing such complex problems. With what we believe to be the most complicated synthetic test case used for such a study, this work investigates using nonlinear regression in ground water model calibration. Results of the study fall into two categories. First, the study demonstrates how systematic use of a well designed nonlinear regression method can indicate the importance of different types of data and can lead to successive improvement of models and their parameterizations. Our method differs from previous methods presented in the ground water literature in that (1) weighting is more closely related to expected data errors than is usually the case; (2) defined diagnostic statistics allow for more effective evaluation of the available data, the model, and their interaction; and (3) prior information is used more cautiously. Second, our results challenge some commonly held beliefs about model calibration. For the test case considered, we show that (1) field measured values of hydraulic conductivity are not as directly applicable to models as their use in some geostatistical methods imply; (2) a unique model does not necessarily need to be identified to obtain accurate predictions; and (3) in the absence of obvious model bias, model error was normally distributed. The complexity of the test case involved implies that the methods used and conclusions drawn are likely to be powerful in practice.

Groundwater↗
USGS1978

Summary appraisals of the nation's ground-water resources – Missouri basin region

The Missouri Basin Region lies in the north-central part of the United States and southern Canada. It includes parts of Alberta and Saskatchewan in Canada; parts of Montana, Wyoming, North Dakota, South Dakota, Minnesota, Iowa, Colorado, Kansas, and Missouri, and all of Nebraska in the United States. The region includes about one-sixth of the contiguous United States and requires large water supplies for irrigation, industrial, public, and rural uses. Climate ranges from semiarid to subhumid. Normal annual precipitation increases generally eastward in the downstream direction, but precipitation is not a dependable source of supply. The Missouri River and its tributaries furnish water to many users, but surface water is often inadequate to meet large demands. Numerous surface reservoirs help to regulate streamflow and provide storage, but they also allow an increase in evapotranspiration, which in some areas exceeds normal precipitation. Ground water occurs in aquifers classified as alluvial deposits of sand and gravel, glacial deposits, dune-sand deposits, basin-fill deposits of sand and gravel, sandstone, siltstone, fractured sandy clay, limestone, and dolomite. Ground water can be developed and managed in an orderly manner provided adequate geologic and hydrologic data are available to determine aquifer characteristics and response to pumping and other hydraulic stresses. These data and determinations are essential to design, testing, and implementation of water management plans. Unconsolidated and semiconsolidated aquifers include valley-fill alluvium, areally extensive alluvium, glacial deposits, and basin-fill deposits. The aquifers normally consist of alluvial sand and gravel that contain unconfined ground water that lies near the land surface. Many wells completed in the alluvial aquifers have high yields of good-quality water because most alluvial aquifers are highly transmissive and hydraulically connected to streams. Aquifers in glacial deposits may be difficult to locate and in some areas contain saline water; nevertheless, these aquifers are sources of water supply for many users. Basin-fill aquifers are as much as several thousand feet thick, and many contain large ground-water supplies. Ground-water mining has occurred in semiconsolidated aquifers because of withdrawals from wells. Unconsolidated and semiconsolidated aquifers have potential for conjunctive use with surface water, recycling to reuse available supplies, artificial recharge, and salvage of evapotranspired water. Sandstone aquifers lie near the land surface and in structural basins. Interbasin movement of ground water occurs in the Virgelle (Milk River aquifer), Fox Hills-basal Hell Creek, and Dakota aquifers. Sandstone aquifers are less transmissive than unconsolidated and semiconsolidated aquifers in general. Confined sandstone aquifers are common, and flowing wells are obtained in many areas. However, flowing wells may cause large declines in water levels if uncontrolled. Water quality is variable in sandstone aquifers but is adequate for most needs. Sandstone aquifers have potential for artificial recharge, induced interaquifer leakage, conjunctive use with surface water, and mining of ground water. Limestone and dolomite aquifers are extensive in the region, but in some areas they lie deep below the land surface. The occurrence of ground water in small pores, fractures, or large caverns causes yields from wells to range widely. Large flows through cavern systems in the aquifers are indicated by large springs in some areas. Water quality is extremely variable and must be considered in any water-development plan. Limestone and dolomite aquifers have potential for development of large water supplies in some areas. The development may be aided by induced recharge and interaquifer leakage. Saline ground water occurs throughout the Missouri Basin Region. Dissolved-solids concentration as much as 30,000 milligrams per liter has been measured in aquifers in glacial deposits in Montana. Saline water is common in sandstone aquifers in Wyoming, North Dakota, and South Dakota; maximum reported concentration is 280,000 milligrams per liter in water from the Tensleep Sandstone in Wyoming. Limestone contains saline water in many areas; maximum dissolved-solids concentration is about 350,000 milligrams per liter for the Madison Group in the Williston Basin in North Dakota. Comprehensive water-management planning in the Missouri Basin Region will require periodic or continuing inventory of precipitation, streamflow, surface-water storage, and ground water. Water demands for irrigation, industrial, public supply, and rural use are increasing rapidly. Reliance on ground-water supplies is increasing even though in many areas the ground water is still mostly undeveloped. Optimal use of water supplies will require the establishment of realistic goals and carefully conceived water-management plans, each of which will necessarily be based on an adequate baseline of hydrologic data and knowledge of the highly variable hydrologic systems in the region.

Colorado, Iowa, Kansas, Minnesota, Missouri, Monta↗
USGS2005

Patterns and rates of ground-water flow on Long Island, New York

Increased ground-water contamination from human activities on Long Island has prompted studies to define the pattern and rate of ground-water movement. A two-dimensional, fine-mesh, finite-element model consisting of 11,969 nodes and 22,880 elements was constructed to represent ground-water flow along a north-south section through central Long Island. The model represents average hydrologic conditions within a corridor approximately 15 miles wide. The model solves discrete approximations of both the potential and stream functions. The resulting flownet depicts flow paths and defines the vertical distribution of flow within the section. Ground-water flow rates decrease with depth. Sixty-two percent of the water flows no deeper than the upper glacial (water-table) aquifer, 38 percent enters the underlying Magothy aquifer, and only 3.1 percent enters the Lloyd aquifer. The limiting streamlines for flow to the Magothy and Lloyd aquifers indicate that aquifer recharge areas are narrow east-west bands through the center of the island. The recharge area of the Magothy aquifer is only 5.4 miles wide; that of the Lloyd aquifer is less than 0.5 miles.

Groundwater↗
USGS1983

Ground water in the southeastern Uinta Basin, Utah and Colorado

The potential for developing oil-shale resources in the southeastern Uinta Basin of Utah and Colorado has created the need for information on the quantity and quality of water available in the area. This report describes the availability and chemical quality of ground water, which might provide a source or supplement of water supply for an oil-shale industry. Ground water in the southeastern Uinta Basin occurs in three major aquifers. Alluvial aquifers of small areal extent are present in valley-fill deposits of six major drainages. Consolidated-rock aquifers include the bird's-nest aquifer in the Parachute Creek Member of the Green River Formation, which is limited to the central part of the study area; and the Douglas Creek aquifer, which includes parts of the Douglas Creek Member of the Green River Formation and parts of the intertonguing Renegade Tongue of the Wasatch Formation; this aquifer underlies most of the study area. The alluvial aquifers are recharged by infiltration of streamflow and leakage from consolidated-rock aquifers. Recharge is estimated to average about 32,000 acre-feet per year. Discharge from alluvial aquifers, primarily by evapotranspiration, also averages about 32,000 acre-feet per year. The estimated volume of recoverable water in storage in alluvial aquifers is about 200,000 acre-feet. Maximum yields to individual wells are less than 1,000 gallons per minute. Recharge to the bird's-nest aquifer, primarily from stream infiltration and downward leakage from the overlying Uinta Formation, is estimated to average 670 acre-feet per year. Discharge from the bird's-nest aquifer, which is primarily by seepage to Bitter Creek and the White River, is estimated to be 670 acre-feet per year. The estimated volume of recoverable water in storage in the bird's-nest aquifer is 1.9 million acre-feet. Maximum yields to individual wells in some areas may be as much as 5,000 gallons per minute. A digital-computer model of the flow system was used to evaluate the effects of oil-shale development on the bird's-nest aquifer at the Federal lease tracts Ua and Ub. Results of model simulations indicate that during construction of a vertical access shaft, a pumping rate of about 900 gallons per minute would be required to dewater the aquifer. The model also indicates that the construction of a proposed reservoir on the White River may raise water levels in the bird's-nest aquifer near the reservoir site by as much as 45 feet. The flow model was used to evaluate the potential ground-water supply available for oil-shale development in the vicinity of the Federal lease tracts Ua and Ub. The results of the simulation indicate that the bird's-nest aquifer could supply about 10,000 acre-feet of water per year at that site, for a period of 20 years. Drawdown after 20 years of pumping would exceed 250 feet near the simulated well field. Based on the results of the model simulation, it is estimated that the aquifer could simultaneously supply another 10,000 acre-feet of water per year in the northern part of the study area, but some interference between well fields could be expected. The Douglas Creek aquifer is recharged by precipitation and stream infiltration at an average rate of about 20,000 acre-feet per year. Discharge is estimated to be about the same and is primarily through springs and diffuse seepage. The estimated volume of recoverable water in storage is 16 million acre-feet. Maximum yields to individual wells are estimated to be less than 500 gallons per minute. A model of the flow system in the Douglas Creek aquifer indicates that the aquifer could supply about 700 acre-feet of water per year for oil-shale development at Federal lease tracts Ua and Ub and at the TOSCO Corp. site. After 20 years of pumping, water levels in production wells would be near the base of the aquifer. Based on the results of the model simulation, it is estimated that the aquifer could supply another 700 acre-feet of water per year in the southern part of the modeled area, but some interference between wells could be expected. Chemical quality of the ground water in the southeastern Uinta Basin varies considerably. Water from alluvial wells ranges from about 440 to 27,800 milligrams per liter of dissolved solids. Water from two consolidated- rock aquifers has dissolved-solids concentrations ranging from 870 to 5,810 milligrams per liter in the bird's-nest aquifer, and from 640 to 6,100 milligrams per liter in the Douglas Creek aquifer. Water from alluvial wells generally is a sodium sulfate type, whereas water in both the consolidated- rock aquifers generally changes from a sodium sulfate type to a sodium bicarbonate type. All ground water is very alkaline, and the alluvial aquifers contain very hard water. None of the water is suitable for public supply, but all the water could be used for industrial purposes such as washing and cooling. Changes in chemical composition of the ground water can be attributed to several physiochemical processes, including mineral precipitation and dissolution, oxidation and reduction, mixing, ion exchange, and evaporative concentration. Mass-transfer modeling of these processes shows how they can account for the variability in the ground-water quality. The mass-transfer model of the Bitter Creek alluvial aquifer shows that evaporative concentration, combined with precipitation of calcite, dolomite, gypsum, and release of carbon dioxide to the atmosphere results in the documented changes in pH and dissolved solids in the water. The water-quality changes in the consolidated-rock aquifers are a result of precipitation of calcium carbonate and perhaps dolomite (calcium magnesium carbonate) with the reduction of sulfate by organic carbon, as well as ion exchange of magnesium for sodium. These processes result in large values of pH and alkalinity in the water.

Colorado, Utah↗
USGS1987

Ground water in the southeastern Uinta Basin, Utah and Colorado

The potential for developing oil-shale resources in the southeastern Uinta Basin of Utah and Colorado has created the need for information on the quantity and quality of water available in the area. This report describes the availability and chemical quality of ground water, which might provide a source or supplement of water supply for an oil-shale industry. Ground water in the southeastern Uinta Basin occurs in three major aquifers. Alluvial aquifers of small areal extent are present i n val ley-f i 11 deposits of six major drainages. Consolidated-rock aquifers include the birds's-nest aquifer i n the Parachute Creek Member of the G reen River Formation, which is limited to the central part of the study area; and the Douglas Creek aquifer, which includes parts of the Douglas Creek Member of the Green River Formation and parts of the intertonguing Renegade Tongue of the Wasatch Formation; this aquifer underlies most of the study area. The alluvial aquifers are recharged by infiltration of streamflow and leakage from consolidated-rock aquifers. Recharge is estimated to average about 32,000 acre-feet per year. Discharge from alluvial aquifers, primarily by evapotranspiration, also averages about 32,000 acre-feet per year. The estimated volume of recoverable water in storage in alluvial aquifers is about 200,000 acre-feet. Maximum yields to individual wells are less than 1,000 gallons per minute. Recharge to the bird's-nest aquifer, primarily from stream infiltration and downward leakage from the overlying Uinta Formation, is estimated to average 670 acre-feet per year. Discharge from the bird's-nest aquifer, which is primarily by seepage to Bitter Creek and the White River, is estimated to be at 670 acre-feet per year. The estimated volume of recoverable water in storage in the bird's-nest aquifer is 1.9 million acre-feet. Maximum yields to individual wells in some areas may be as much as 5,000 gallons per minute. A digital-computer model of the flow system was used to evaluate the effects of oil-shale development on the bird's-nest aquifer at the Federal lease tracts Ua and Ub. Results of model simulations indicate that during construction of a vertical access shaft, a pumping rate of about 900 gallons per minute would be required to dewaterthe aquifer. The model also indicates that the construction of a proposed reservoir on the White River may raise water levels in the bird's-nest aquifer near the reservoir site by as much as 45 feet. The flow model was used to evaluate the potential ground-water supply available for oil-shale development in the vicinity of the Federal lease tracts Ua and Ub. The results of the simulation indicate that bird's-nest aquifer could supply about 10,000 acre-feet of water per year at that site, for a period of 20 years. Downdraw after 20 years of pumping would exceed 250 feet near the simulated well field. Based on the results of the model simulation, it is estimated that the aquifer could simultaneously supply another 10,000 acre-feet of water per year in the northern part of the study area, but some interference between well fields could be expected. The Douglas Creek aquifer is recharged by precipitation and stream infiltration at an average rate of about 20.000 acre-feet per year. Discharge is estimated to be about the same and is primarily through springs and diffuse seepage. The estimated volume of recoverable water in storage is 16 million acre-feet. Maximum yields to individual wells are estimated to be less than 500 gallons per minute. A model of the flow system in the Douglas Creek aquifer indicates that the aquifer could supply about 700 acre-feet of water per year for oil-shale development at Federal lease tracts Ua and Ub and at the TOSCO Corp. site. After 20 years of pumping, water levels in production wells would be near the base of the aquifer. Based on the results of the model simulation, it is estimated that the aquifer could supply another 700 acre-feet of water per year in the southern part of the modeled area, but some interference between wells could be expected. Chemical quality of the ground water in the southeastern Uinta Basin varies considerably. Water from alluvial wells ranges from about 440 to 27,800 milligrams per liter of dissolved solids. Water from two consolidated-rock aquifers has dissolved-solids concentrations ranging from 870 to 5,810 milligrams per liter in the bird's-nest aquifer, and from 640 to 6,100 milligrams per liter in the Douglas Creek aquifer. Water from alluvial wells generally is a sodium sulfate type, whereas water in both the consolidated-rock aquifers generally changes from a sodium sulfate type to a sodium bicarbonate type. All ground water is very alkaline, and the alluvial aquifers contain very hard water. None of the water is suitable for public supply, but all the water could be used for industrial purposes such as washing and cooling. Changes in chemical composition of the ground water can be attributed to several physiochemical processes, including mineral precipitation and dissolution, oxidation and reduction, mixing, ion exchange, and evaporative concentration. Mass-transfer modeling of these processes shows how they can account for the variability in the ground-water quality. The mass-transfer model of the Bitter Creek alluvial aquifer shows that evaporative concentration, combined with precipitation of calcite, dolomite, gypsum, and release of carbon dioxide to the atmosphere results in the documented changes in the pH and dissolved solids in the water. The water-quality changes in the consolidated-rock aquifers are a result of precipitation of calcium carbonate and perhaps dolomite (calcium magnesium carbonate) with the reduction of sulfate by organic carbon, as well as ion exchange of magnesium for sodium. These processes result in large values of pH and alkalinity in the water.

Colorado, Utah↗
USGS2002

Occurrence and distribution of pesticides and volatile organic compounds in ground water and surface water in Central Arizona Basins, 1996-98, and their relation to land use

Samples of ground water and surface water from the Sierra Vista subbasin, the Upper Santa Cruz Basin, and the West Salt River Valley were collected and analyzed to determine the occurrence and distribution of pesticides and volatile organic compounds in central Arizona. The study was done during 1996-98 within the Central Arizona Basins study unit of the National Water-Quality Assessment program. This study included 121 wells and 4 surface-water sites in the 3 basins and the analyses of samples from 4 sites along the Santa Cruz River that were part of a separate study. Samples were collected from 121 wells and 3 surface-water sites for pesticide analyses, and samples were collected from 109 wells and 3 surface-water sites for volatile organic compound analyses. Certain pesticides detected in ground water and surface water can be related specifically to agricultural or urban uses; others can be related to multiple land uses. Effects from historical agriculture are made evident by detections of DDE in ground-water and surface-water samples collected in the West Salt River Valley and detections of atrazine and deethylatrazine in the ground water in the Upper Santa Cruz Basin. Effects from present agriculture are evident in the seasonal variability in concentrations of pre-emergent pesticides in surface-water samples from the West Salt River Valley. Several detections of DDE and dieldrin in surface water were higher than established water-quality limits. Effects of urban land use are made evident by detections of volatile organic compounds in ground water and surface water from the West Salt River Valley. Detections of volatile organic compounds in surface water from the Santa Cruz River near Nogales, Arizona, also are indications of the effects of urban land use. One detection of tetrachloroethene in ground water was higher than established water-quality limits. Water reuse is an important conservation technique in the Southwest; however, the reuse of water provides a transport mechanism for pesticides and volatile organic compounds to reach areas that are not normally affected by manmade compounds from specific land-use activities. The most complex mixture of pesticides and volatile organic compounds is in the West Salt River Valley and is the result of water-management practices and the combination of land uses in this basin throughout history.

Arizona↗
USGS2000

Interaction between ground water and surface water in Taylor Slough and vicinity, Everglades National Park, South Florida: Study methods and appendixes

The data presented in this report are products of an investigation that quantified interactions between ground water and surface water in Taylor Slough in Everglades National Park. Determining the extent of hydrologic interactions between wetland surface water and ground water in Taylor Slough is important because the balance of freshwater flow in the lower part of the Slough is uncertain. Although freshwater flows through Taylor Slough are quite small in comparison to Shark Slough (the larger of the two major sloughs in Everglades National Park), flows through Taylor Slough are especially important to the ecology of estuarine mangrove embayments of northeastern Florida Bay. Also, wetland and ground- water interactions must be quantified if their role in affecting water quality is to be determined. In order to define basic hydrologic characteristics of the wetland, depth of wetland peat was mapped, and hydraulic conductivity and vertical hydraulic gradients in peat were determined. During specific time periods representing both wet and dry conditions in the area, the distribution of major ions, nutrients, and water stable isotopes throughout the slough were determined. The purpose of chemical measurements was to identify an environmental tracer could be used to quantify ground-water discharge.

Florida↗