Geology topics

Groundwater & aquifers

Find USGS groundwater and aquifer publications. Search an aquifer name or place, compare source-supplied dates and open reports for hydrogeology, recharge and water-level studies.

Follow this topic with RSS

At least 757 records · Page 42Linked to original sources

USGS2025

A geospatial analysis of water-quality threats from orphan wells in principal and secondary aquifers of the United States

Throughout the history of oil and gas production in the United States, millions of wells have been drilled for exploration and energy production. Hundreds of thousands of unplugged wells are no longer actively producing and are currently under orphan status, with no responsible party obligated for plugging. Orphan wells can pose threats to water resources by providing pathways for contaminants such as hydrocarbons and brines to migrate into water-supply aquifers. In this study, we investigate the potential threats to groundwater resources posed by orphan wells at the national scale. Water-quality data is extremely sparse in relation to orphan wells nationally and may not be suitable for identifying contamination from oil and gas development. We used geospatial and statistical methods to evaluate which principal and secondary aquifer systems may be most susceptible to contamination from orphan wells. Analysis involved three sets of susceptibility factors including: 1) factors related to the number and density of orphan wells; 2) factors that can threaten well integrity and contribute to transport of contaminants; and 3) factors related to groundwater withdrawal rates and the affected populations/communities in the event of water quality disturbances. From a dataset of 117,672 documented orphan wells, 64,203 fall within a principal aquifer system, while the remainder fall within a secondary aquifer system. By assessing the combination of well integrity and hydrogeologic factors within these aquifer systems, five groupings of principal aquifers were identified, where groups ranged from aquifer systems with high numbers of orphan wells, multiple well integrity threats and high withdrawals, to aquifers with a relatively low number of orphan wells, limited well integrity threats and minimal water use. Three regions of the country emerge containing aquifers with higher susceptibility to contamination from orphan oil and gas wells. These regions include 1) The Appalachian Basin (including the Pennsylvanian Aquifer System), 2) The Gulf Coast Aquifers (including the Coastal Lowlands Aquifer system) and 3) The California Aquifers (including the California Coastal Basin Aquifer system). This work is the first multivariate geospatial investigation of orphan wells and groundwater resources on a national scale, and sheds light on which aquifers are most susceptible to groundwater contamination from orphan wells.

Science of the Total Environment↗

USGS2014

Groundwater-quality data in the Klamath Mountains study unit, 2010: results from the California GAMA Program

Groundwater quality in the 8,806-square-mile Klamath Mountains (KLAM) study unit was investigated by the U.S. Geological Survey (USGS) from October to December 2010, as part of the California State Water Resources Control Board (SWRCB) Groundwater Ambient Monitoring and Assessment (GAMA) Program’s Priority Basin Project (PBP). The GAMA-PBP was developed in response to the California Groundwater Quality Monitoring Act of 2001 and is being conducted in collaboration with the SWRCB and Lawrence Livermore National Laboratory (LLNL). The KLAM study unit was the thirty-third study unit to be sampled as part of the GAMA-PBP. The GAMA Klamath Mountains study was designed to provide a spatially unbiased assessment of untreated-groundwater quality in the primary aquifer system and to facilitate statistically consistent comparisons of untreated-groundwater quality throughout California. The primary aquifer system is defined by the perforation intervals of wells listed in the California Department of Public Health (CDPH) database for the KLAM study unit. Groundwater quality in the primary aquifer system may differ from the quality in the shallower or deeper water-bearing zones; shallower groundwater may be more vulnerable to surficial contamination. In the KLAM study unit, groundwater samples were collected from sites in Del Norte, Siskiyou, Humboldt, Trinity, Tehama, and Shasta Counties, California. Of the 39 sites sampled, 38 were selected by using a spatially distributed, randomized grid-based method to provide statistical representation of the primary aquifer system in the study unit (grid sites), and the remaining site was non-randomized (understanding site). The groundwater samples were analyzed for basic field parameters, organic constituents (volatile organic compounds [VOCs] and pesticides and pesticide degradates), inorganic constituents (trace elements, nutrients, major and minor ions, total dissolved solids [TDS]), radon-222, gross alpha and gross beta radioactivity, and microbial indicators (total coliform and Escherichia coli [E. coli]). Isotopic tracers (stable isotopes of hydrogen and oxygen in water, isotopic ratios of dissolved strontium in water, and stable isotopes of carbon in dissolved inorganic carbon), dissolved noble gases, and age-dating tracers (tritium and carbon-14) were measured to help identify sources and ages of sampled groundwater. Quality-control samples (field blanks, replicate sample pairs, and matrix spikes) were collected at 13 percent of the sites in the KLAM study unit, and the results were used to evaluate the quality of the data from the groundwater samples. Field blank samples rarely contained detectable concentrations of any constituent, indicating that contamination from sample collection or analysis was not a significant source of bias in the data for the groundwater samples. More than 99 percent of the replicate pair samples were within acceptable limits of variability. Matrix-spike sample recoveries were within the acceptable range (70 to 130 percent) for approximately 91 percent of the compounds. This study did not evaluate the quality of water delivered to consumers. After withdrawal, groundwater typically is treated, disinfected, and (or) blended with other waters to maintain water quality. Regulatory benchmarks apply to water that is delivered to the consumer, not to untreated groundwater. However, to provide some context for the results, concentrations of constituents measured in the untreated groundwater were compared with regulatory and non-regulatory health-based benchmarks established by the U.S. Environmental Protection Agency (USEPA) and CDPH, and to non-health-based benchmarks established for aesthetic concerns by the CDPH. Comparisons between data collected for this study and benchmarks for drinking water are for illustrative purposes only and are not indicative of compliance or non-compliance with those benchmarks. All concentrations of organic constituents from grid sites sampled in the KLAM study unit were less than health-based benchmarks. In total, VOCs were detected in 16 of the 38 grid sites sampled (approximately 42 percent), pesticides and pesticide degradates were detected in 8 grid sites (about 21 percent), and microbial indicators were detected in 14 grid sites (approximately 37 percent). Inorganic constituents (trace elements, major and minor ions, nutrients, and uranium and other radioactive constituents) and microbial indicators were sampled for at 38 grid sites, and all concentrations were less than health-based benchmarks, with the exception of one detection of boron greater than the CDPH notification level of 1,000 micrograms per liter (μg/L). Generally, concentrations of inorganic constituents with non-health-based benchmarks (iron, manganese, chloride, and TDS) were less than the CDPH secondary maximum contaminant level (SMCL-CA). Exceptions include three detections of iron greater than the SMCL-CA of 300 μg/L, four detections of manganese greater than the SMCL-CA of 50 μg/L, one detection of chloride greater than the recommended SMCL-CA of 250 μg/L, and one detection of TDS greater than the recommended SMCL-CA of 500 μg/L.

California↗

USGS2010

Water levels in aquifers in the Nacatoch Sand of southwestern and northeastern Arkansas and the Tokio Formation of southwestern Arkansas, spring 2008

The Nacatoch Sand and Tokio Formation aquifers in southwestern Arkansas and the Nacatoch Sand in northeastern Arkansas are sources of water for industrial, public supply, domestic, and agricultural uses. Potentiometric-surface maps were constructed from water-level measurements made in 61 wells completed in the Nacatoch Sand and in 50 wells completed in the Tokio Formation during spring 2008. Aquifers in the Nacatoch Sand and Tokio Formation are hereafter referred to as the Nacatoch aquifer and the Tokio aquifer, respectively. The direction of groundwater flow in the Nacatoch aquifer in northeastern Arkansas generally is towards the southeast. A potentiometric high is located along the north and northwestern boundaries of the area. The direction of groundwater flow in the Nacatoch aquifer in southwestern Arkansas is towards the south-southeast in Little River, Miller, and Hempstead Counties and to the east-southeast in Nevada and Clark Counties. A potentiometric high is located within the outcrop area in north-central Hempstead County. A cone of depression exists in the Nacatoch aquifer at Hope in southeastern Hempstead County. The direction of groundwater flow in the Tokio aquifer in southwestern Arkansas generally is towards the south or southeast. A potentiometric high is located within the outcrop area. Artesian conditions exist in southeastern Pike, northeastern Hempstead, and northwestern Nevada Counties. One apparent cone of depression might exist northwest of Hope in Hempstead County. In northeastern Arkansas, groundwater withdrawals from the Nacatoch aquifer increased by 480 percent from 1965 to 2005. In southwestern Arkansas, withdrawals from the Nacatoch aquifer and Tokio aquifer increased by 125 percent and 201 percent, respectively, from 1965 to 1980 and decreased by 93 percent and 80 percent, respectively, from 1980 to 2000. Withdrawals from Nacatoch aquifer and Tokio aquifer increased by 690 percent and 291 percent, respectively, from 2000 to 2005. Long-term hydrographs were prepared for 10 wells in the study areas. Changes in water levels in some wells may be associated with changes in withdrawals from the respective aquifers.

Scientific Investigations Report↗

USGS2017

Hydrogeologic framework and hydrologic conditions of the Piney Point aquifer in Virginia

The Piney Point aquifer in Virginia is newly described and delineated as being composed of six geologic units, in a study conducted by the U.S. Geological Survey in cooperation with the Virginia Department of Environmental Quality (VA DEQ). The eastward-dipping geologic units include, in stratigraphically ascending order, the sand of the Nanjemoy Formation Woodstock Member, interbedded limestone and sand of the Piney Point Formation, silty and clayey sand of the Gosport Formation equivalent sediments, silty sand of the Oligocene-age sediments, silty fine-grained sand of the Old Church Formation, and silty sand of the Calvert Formation, Newport News unit and basal Plum Point Member. Identification of geologic units is based on typical sediment lithologies of geologic formations. Fine-grained sediments that compose confining units positioned immediately above and below the Piney Point aquifer are also described. The Piney Point aquifer is one of several confined aquifers within the Virginia Coastal Plain and includes a highly porous and solution-channeled indurated limestone within the Piney Point Formation from which withdrawals are made. The limestone is relatively continuous laterally across central parts of the Northern Neck, Middle Peninsula, and York-James Peninsula. Other geologic units are of variable extent. The configurations of most of the geologic units are further affected by newly identified faults that are aligned radially from the Chesapeake Bay impact crater and create constrictions or barriers to groundwater flow. Some geologic units are also truncated beneath the lower Rappahannock River by a resurge channel associated with the impact crater. Groundwater withdrawals from the Piney Point aquifer increased from approximately 1 million gallons per day (Mgal/d) during 1900 to 7.35 Mgal/d during 2004. As a result, a water-level cone of depression in James City and northern York Counties was estimated to be as low as 70 feet (ft) below the National Geodetic Vertical Datum of 1929 (NGVD 29) by 2005. Withdrawals decreased to 5.01 Mgal/d by 2009 as withdrawals were shifted toward other sources, and by 2015 water levels had recovered to approximately 50 ft below NGVD 29. The mean estimated transmissivity of the Piney Point aquifer in York and James City Counties is 16,300 feet squared per day (ft 2 /d), but farther north it is only 925 ft 2 /d. The mean well specific capacity in York and James City Counties is 11.4 gallons per minute per foot (gal/min/ft). Farther north in Virginia, mean specific capacity is only 2.26 gal/min/ft, and in Maryland it is 0.99 gal/min/ft. The northward decrease in specific capacity probably reflects the northward decrease in transmissivity, which results from poor development of the solution-channeled limestone. An aquifer test in northern York County induced vertical leakage to the solution-channeled limestone from overlying silty sand and a change in response of the aquifer to pumping from a single layer to two layers. Transmissivity of the limestone of approximately 19,800 ft 2 /d was distinguished from the silty sand of approximately 2,500 ft 2 /d. Most of the water in the Piney Point aquifer is slightly alkaline with moderate concentrations primarily of sodium and bicarbonate that are slightly undersaturated with respect to calcite. Iron concentrations are generally less than 0.3 milligrams per liter (mg/L). Mixing of freshwater with seawater has elevated chloride concentrations to the southeast to as much as 7,120 mg/L. Information on the Piney Point aquifer can benefit water-resource management in siting production wells, predicting likely well yield, and anticipating water-level response to withdrawals. Models that vertically discretize individual geologic units can potentially be used to evaluate groundwater flow in greater detail by representing lateral flow and vertical leakage among the geologic units. Because groundwater withdrawals are made primarily from the limestone and sand of the Piney Point Formation, the VA DEQ has considered regarding the limestone and sand singly as a regulated aquifer apart from the other geologic units. Under current policy in Virginia, if only the limestone and sand were regarded as a regulated aquifer, a greater amount of drawdown would be allowed than is allowed for the Piney Point aquifer consisting of six geologic units. Some production wells intercept multiple geologic units, and the units can undergo water-level decline and vertical leakage induced by pumping from the limestone and sand. Whether the other geologic units are to be regarded as regulated aquifers is an additional consideration for the VA DEQ.

Virginia↗

USGS2021

The occurrence and distribution of strontium in U.S. groundwater

Groundwater samples from 32 principal aquifers across the United States (U.S.) provide a broad spatial scope of the occurrence and distribution of strontium (Sr) and are used to assess environments and factors that influence Sr concentration. Strontium is a common trace element in soils, rocks, and water and is ubiquitous in groundwater with detectable concentrations in 99.8% of samples (n=4,824; median = 225 μg/L). Concentrations in 2.3% of samples exceeded the 4,000 μg/L health-based screening level. The relative importance of controlling factors on Sr concentration are spatially variable and partly dependent on the type of groundwater well. Three case settings illustrate controls on Sr concentration. For drinking-water supply wells, most high concentrations (>4,000 μg/L) were measured in samples from carbonate aquifers that resulted from water-rock interaction with Sr-bearing rocks and minerals. High Sr concentrations from monitoring wells were more common in unconsolidated sand and gravel aquifers in arid or semi-arid setting where shallow groundwater is affected by irrigation and evaporative concentration of dissolved constituents in combination with lithologic or applied Sr sources. Upwelling saline groundwater is also a source of Sr source in some locations. Total dissolved solids concentration is an indicator of high Sr in all settings. An estimated 2.2 million people in the conterminous U.S. are potentially supplied water from public-supply wells with high Sr concentration, ∼86% of whom use carbonate aquifers (with > half supplied by the Floridan aquifer system). An additional 120,000 people are potentially supplied high-Sr-concentration water from domestic wells, >half of whom (∼58%) are in Texas. This study markedly expands the coverage of previous surveys of Sr in groundwater and is of interest given potential adverse human-health effects related to elevated concentrations of Sr and consideration of Sr for drinking-water regulation. Case settings with elevated Sr described for U.S. groundwater are likely indicative of settings and processes affecting Sr concentration in groundwater globally.

Continemtal United States↗

USGS2026

Hydrogeology and water quality of the unconsolidated aquifer system in the Lower Fall Creek Valley, Tompkins County, New York

The U.S. Geological Survey, in cooperation with Tompkins County and the Town of Dryden, conducted a hydrogeologic investigation of the lower Fall Creek unconsolidated aquifer system in Tompkins County, New York. This study is part of an ongoing effort to characterize major valley-fill aquifers in the region to support sustainable groundwater management. The lower Fall Creek valley, encompassing the Village of Freeville, the unincorporated communities of Etna, and the hamlets of McLean and Varna, has experienced moderate development and relies heavily on groundwater for residential, agricultural, and commercial use. The study area spans approximately 51 square miles along the boundary of the Allegheny Plateau and North Rim of the Allegheny Plateau physiographic provinces. The aquifer system, composed primarily of glacially derived sand and gravel deposits, includes both unconfined and confined aquifer units. For the approximately 2,300 people who live over the aquifers, groundwater is the sole source of drinking water. In some areas, such as the Village of Freeville, artesian conditions exist, with potentiometric heads exceeding 25 feet above land surface. This report describes the hydrogeologic framework, aquifer distribution, groundwater-flow dynamics, and water quality of the lower Fall Creek aquifer system. Groundwater is generally hard and contains elevated concentrations of redox-sensitive constituents, such as iron and manganese relative to U.S. Environmental Protection Agency secondary maximum contaminant levels. Arsenic was not detected above the U.S. Environmental Protection Agency maximum contaminant level during this study but remains a regional concern due to past detections in the study area and nearby aquifers. The findings provide data for local planners and resource managers to use in understanding and protecting this water resource.

EarthArXiv↗

USGS2015

The quality of our Nation's waters: Water quality in the glacial aquifer system, northern United States, 1993-2009

The glacial aquifer system underlies much of the northern United States. About one-sixth (41 million people) of the United States population relies on the glacial aquifer system for drinking water. The primary importance of the glacial aquifer system is as a source of water for public supply to the population centers in the region, but the aquifer system also provides drinking water for domestic use to individual homes and small communities in rural areas. Withdrawals from this aquifer system for public supply are the largest in the Nation and play a key role in the economic development of parts of 26 States. Corn production has increased in the central part of the aquifer system over the last 10 years, and the increased production increases the need for water for agricultural use and the need for increased use of agrochemicals. Additionally, the steady increase in population (15 million people over the last 40 years) in urban and rural areas is resulting in an increased reliance on the glacial aquifer system for high-quality drinking water. The need to monitor, understand, and maintain the water quality of this valuable economic resource continues to grow. Major Findings Contaminants from geologic source—in particular arsenic and manganese—in groundwater used for drinking are a potential concern for human health Concentrations of nitrate and pesticides in groundwater were low in fine-grained sediment even in areas of intensive agriculture Chloride concentrations in groundwater are increasing in urban areas “Nuisance” constituents in groundwater from the glacial aquifer system could limit groundwater use

Circular↗

USGS2011

Groundwater quality in the Santa Clara River Valley, California

The Santa Clara River Valley (SCRV) study unit is located in Los Angeles and Ventura Counties, California, and is bounded by the Santa Monica, San Gabriel, Topatopa, and Santa Ynez Mountains, and the Pacific Ocean. The 460-square-mile study unit includes eight groundwater basins: Ojai Valley, Upper Ojai Valley, Ventura River Valley, Santa Clara River Valley, Pleasant Valley, Arroyo Santa Rosa Valley, Las Posas Valley, and Simi Valley (California Department of Water Resources, 2003; Montrella and Belitz, 2009). The SCRV study unit has hot, dry summers and cool, moist winters. Average annual rainfall ranges from 12 to 28 inches. The study unit is drained by the Ventura and Santa Clara Rivers, and Calleguas Creek. The primary aquifer system in the Ventura River Valley, Ojai Valley, Upper Ojai Valley, and Simi Valley basins is largely unconfined alluvium. The primary aquifer system in the remaining groundwater basins mainly consists of unconfined sands and gravels in the upper portion and partially confined marine and nonmarine deposits in the lower portion. The primary aquifer system in the SCRV study unit is defined as those parts of the aquifers corresponding to the perforated intervals of wells listed in the California Department of Public Health (CDPH) database. Public-supply wells typically are completed in the primary aquifer system to depths of 200 to 1,100 feet below land surface (bls). The wells contain solid casing reaching from the land surface to a depth of about 60-700 feet, and are perforated below the solid casing to allow water into the well. Water quality in the primary aquifer system may differ from the water in the shallower and deeper parts of the aquifer. Land use in the study unit is approximately 40 percent (%) natural (primarily shrubs, grassland, and wetlands), 37% agricultural, and 23% urban. The primary crops are citrus, avocados, alfalfa, pasture, strawberries, and dry beans. The largest urban areas in the study unit are the cities of Ventura, Oxnard, Camarillo, Simi Valley, Newhall, and Santa Clarita. Currently, groundwater pumping for agricultural use accounts for the greatest amount of discharge from the aquifer system in the SCRV study unit, followed by municipal use. Recharge to the groundwater system is through stream-channel infiltration from the three main river systems and by direct infiltration of precipitation and irrigation. Recharge facilities in the Oxnard forebay play an important role in recharging the local aquifer systems.

Fact Sheet↗

USGS1989

Flow of ground water through fractured carbonate rocks in the Prairie du Chien-Jordan Aquifer, southeastern Minnesota

Contamination of groundwater from point and nonpoint sources (such as landfills, feedlots, agricultural chemicals applied to fields, and septic systems) is a recognized problem in the karst area of southeastern Minnesota. The US Geological Survey, in cooperation with the Minnesota Department of Natural Resources and the Legislative Commission on Minnesota Resources, Began a study in October 1987 to improve the understanding of local groundwater flow through karst terrain in southeastern Minnesota. The objectives of the study are to: (1) describe the orientations of systematic rock fractures and solution channels of the Prairie du Chien Group of Ordovician-age carbonate rocks in southeastern Minnesota, and, if possible, to define the principal and minor axes of these orientations; and (2) evaluate the effect of fractures and solution channels in the Prairie du Chien Group on the local flow of groundwater. Groundwater in the Upper Carbonate aquifer regionally flows toward the periphery of the aquifer and locally flows into streams and bedrock valleys. The hydraulic gradient in this aquifer generally is greatest near areas of groundwater seepage to streams. Regional groundwater flow in the Prairie du Chien-Jordan aquifer generally is to the south and east in much of Fillmore and Houston Counties and in the southern parts of Olmsted and Winona Counties. Groundwater seepage to selected streams was evaluated by current-meter measurements of downstream gains or losses of streamflow and by an experimental approach based on radon activity in streams. The activity of radon in groundwater ranges from two to four orders of magnitude greater than the activity in surface water; therefore, groundwater seepage to streams generally increases the in-stream radon activity.

Minnesota↗

USGS2015

Potentiometric surface, 2013, and water-level differences, 1991-2013, of the Carrizo-Wilcox aquifer in northwest Louisiana

The Carrizo-Wilcox aquifer is the primary source of fresh groundwater for public supply as well as industrial, agricultural, and domestic uses in several parishes in northwestern Louisiana, including Bienville, Bossier, Caddo, De Soto, Natchitoches, Red River, Sabine, and Webster. In 2010, about 19 million gallons per day (Mgal/d) were withdrawn from the Carrizo-Wilcox aquifer in Louisiana. This is an increase of over 6 Mgal/d from 1990 withdrawal amounts. The largest increase in withdrawals occurred in Caddo (3.79 Mgal/d) and De Soto Parishes (2.32 Mgal/d), whereas the largest decrease in withdrawals occurred in Natchitoches Parish (1.17 Mgal/d). Groundwater withdrawals from the Carrizo-Wilcox aquifer have caused water-level declines throughout much of the aquifer in the study area. Additional knowledge about the effects of withdrawals on water levels and flow directions in the Carrizo-Wilcox aquifer are needed to assess current conditions in the aquifer. In 2012, the U.S. Geological Survey (USGS) in cooperation with the Louisiana Department of Natural Resources began a study to document current water levels and water-level changes in selected aquifers. This report presents data and maps that illustrate the potentiometric surface of the Carrizo-Wilcox aquifer during March–May 2013 and water-level differences from 1991 to 2013. The potentiometric surface map can be used for determining the direction of groundwater flow, hydraulic gradients, and effects of withdrawals on the groundwater resource. The rate of groundwater movement also can be estimated from the gradient when the hydraulic conductivity is applied. Water-level data collected for this study are stored in the USGS National Water Information System (NWIS) ( http://waterdata.usgs.gov/nwis ) and are on file at the USGS office in Baton Rouge, La.

Louisiana↗

USGS2010

Hydrogeology and numerical simulation of the unconsolidated glacial aquifer in the Pootatuck River Basin, Newtown, Connecticut

A study of the groundwater and stream-aquifer interaction in the Pootatuck River Basin, Newtown, Connecticut, was conducted to analyze the effect of production wells on the groundwater levels and streamflow in the Pootatuck River as part of a cooperative program between the U.S. Geological Survey and Newtown, Connecticut. This study will help address concerns about the increasing competition for water for human uses and protection of aquatic habitat. The groundwater-flow model developed in the study was designed for use as a tool to assist planners in assessing the effects of potential future development, which will change the amount and distribution of recharge available to the groundwater system. Several different techniques were used to investigate the interconnection between the stream and the aquifer. Temperature, groundwater levels, stream stage, and stable-isotope data collected during aquifer tests at the principal production wells in the Pootatuck River Basin, as well as groundwater-flow simulations of the system, indicate that more than half of the water pumped from the wells comes from the Pootatuck River. This finding potentially has a large effect on approaches for protecting the water quality of the pumped water. Increases in the amount of impervious surface from future development will reduce and redistribute recharge to the groundwater system. The simulation of future development scenarios showed a decrease in the simulated base flow in the main stem of the Pootatuck River and in all of the 26 simulated subbasins, with some of the subbasins showing a decrease of more than 20 percent when new development had 85 percent impervious area. The groundwater-flow model and particle tracking were used to determine areas that contribute recharge to the five production wells available for use in the Pootatuck River Basin. These areas included narrow portions of the aquifer that extended beyond the immediate upgradient areas, probably because of deeper groundwater-flow paths.

Scientific Investigations Report↗

USGS2012

A comparison of U.S. Geological Survey three-dimensional model estimates of groundwater source areas and velocities to independently derived estimates, Idaho National Laboratory and vicinity, Idaho

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, evaluated a three-dimensional model of groundwater flow in the fractured basalts and interbedded sediments of the eastern Snake River Plain aquifer at and near the Idaho National Laboratory to determine if model-derived estimates of groundwater movement are consistent with (1) results from previous studies on water chemistry type, (2) the geochemical mixing at an example well, and (3) independently derived estimates of the average linear groundwater velocity. Simulated steady-state flow fields were analyzed using backward particle-tracking simulations that were based on a modified version of the particle tracking program MODPATH. Model results were compared to the 5-microgram-per-liter lithium contour interpreted to represent the transition from a water type that is primarily composed of tributary valley underflow and streamflow-infiltration recharge to a water type primarily composed of regional aquifer water. This comparison indicates several shortcomings in the way the model represents flow in the aquifer. The eastward movement of tributary valley underflow and streamflow-infiltration recharge is overestimated in the north-central part of the model area and underestimated in the central part of the model area. Model inconsistencies can be attributed to large contrasts in hydraulic conductivity between hydrogeologic zones. Sources of water at well NPR-W01 were identified using backward particle tracking, and they were compared to the relative percentages of source water chemistry determined using geochemical mass balance and mixing models. The particle tracking results compare reasonably well with the chemistry results for groundwater derived from surface-water sources (-28 percent error), but overpredict the proportion of groundwater derived from regional aquifer water (108 percent error) and underpredict the proportion of groundwater derived from tributary valley underflow from the Little Lost River valley (-74 percent error). These large discrepancies may be attributed to large contrasts in hydraulic conductivity between hydrogeologic zones and (or) a short-circuiting of underflow from the Little Lost River valley to an area of high hydraulic conductivity. Independently derived estimates of the average groundwater velocity at 12 well locations within the upper 100 feet of the aquifer were compared to model-derived estimates. Agreement between velocity estimates was good at wells with travel paths located in areas of sediment-rich rock (root-mean-square error [RMSE] = 5.2 feet per day [ft/d]) and poor in areas of sediment-poor rock (RMSE = 26.2 ft/d); simulated velocities in sediment-poor rock were 2.5 to 4.5 times larger than independently derived estimates at wells USGS 1 (less than 14 ft/d) and USGS 100 (less than 21 ft/d). The models overprediction of groundwater velocities in sediment-poor rock may be attributed to large contrasts in hydraulic conductivity and a very large, model-wide estimate of vertical anisotropy (14,800).

Idaho↗

USGS2012

A comparison of U.S. Geological Survey three-dimensional model estimates of groundwater source areas and velocities to independently derived estimates, Idaho National Laboratory and vicinity, Idaho

Idaho↗

USGS2019

Groundwater and surface-water resources near Red Fleet Reservoir, Uintah County, Utah

Red Fleet Reservoir in Uintah County, Utah, is an approximately 26,000 acre-foot (acre-ft) on-channel reservoir in the Big Brush Creek drainage on the south slopes of the Uinta Mountains. It is operated primarily for irrigation needs while providing a supplemental drinking-water supply to the Vernal, Utah area. Red Fleet Reservoir, which was operated by the Bureau of Reclamation and the Uintah Water Conservancy District through 2015, began storing water in May 1980. The reservoir is on southward dipping Mesozoic lithologies ranging from Jurassic to Cretaceous in age. The Nugget and Frontier Sandstone aquifers are the targeted units in this investigation, which is to characterize groundwater conditions that exist in each sandstone aquifer and how they interact with Red Fleet Reservoir. Groundwater levels were measured in six wells and one spring in the Nugget Sandstone and the Frontier Sandstone aquifers. Water levels in the Nugget Sandstone aquifer were 35–70 feet above the maximum stage of Red Fleet Reservoir on the west and east banks. Water levels in the Frontier Sandstone aquifer were 15–30 feet below the observed stage of Red Fleet Reservoir on the west bank during the study period. A water budget was calculated for Red Fleet Reservoir between May 1980 and December 2015. During this period, 1,050,000 acre-ft of water from Big Brush Creek discharged into the reservoir, while 993,000 acre-ft of water was released downstream of Red Fleet Dam. Total evaporation from May 1980 through December 2015 was about 52,000 acre-ft, while total precipitation over the same period was about 12,000 acre-ft. From May 1980 through December 2015, the total pumped volume of water from the Tyzack Pump Station, at the base of Red Fleet Dam, was about 42,000 acre-ft. Total groundwater discharge to Red Fleet Reservoir from 1980 through 2015 was about 40,000 acre-ft. Water was sampled from four wells and from the inflow arm of Red Fleet Reservoir, and analyzed for major-ion chemistry, select trace metals, nutrients, and environmental tracers. Water sampled from the Nugget Sandstone aquifer yielded good-quality water with dissolved-solids concentrations of less than 200 milligram per liter, and no trace elements above the Environmental Protection Agency drinking-water standards. Water sampled from the Frontier Sandstone aquifer yielded poor-quality water with dissolved-solids concentrations of about 2,150 milligrams per liter with trace elements approaching drinking-water standards for arsenic. Dissolved noble gases used to identify recharge elevations and temperatures for groundwater indicate that water in the Nugget Sandstone aquifer likely recharged at a high altitude and low temperature, and not locally because of interaction with Red Fleet Reservoir. The Frontier Sandstone aquifer is likely recharged at low elevation and at temperatures similar to those observed at Red Fleet Reservoir.

Utah↗

USGS2026

Hydrogeology and water quality of the unconsolidated aquifer system in the lower Fall Creek valley, Tompkins County, New York

New York↗

USGS1985

Simulation of the effects of management alternatives on the stream-aquifer system, South Fork Solomon River Valley between Webster Reservoir and Waconda Lake, north-central Kansas

With extensive irrigation use of both surface water and groundwater in the South Fork Solomon River valley shortages of these water supplies have been created. A two-dimensional digital model of transient groundwater flow was applied to investigate the potential effects on the stream aquifer system of seven management alternatives. These alternatives included proposals to conserve surface water supplies by lining the Osborne Irrigation Canal with clay, replacing the lateral canals with pipe, removing phreatophytes, decreasing surface water use by 75%, 50%, or 25% and replacing it with groundwater sources, and continuing 1978 groundwater use and 1970-78 average surface water use until the end of the 20th century. Results were assessed by comparison of drawdowns of hydraulic head in the alluvial aquifer and base flow for each simulation. As listed in order of the smallest to the greatest potential effects on the system relative to drawdown and base flow the alternatives are: (1) removal of one-half of the phreatophytes; (2) continuation of 1978 groundwater withdrawals and average 1970-78 surface water supply; (3) replacement of the lateral canals with pipe; (4) lining the Osborne Irrigation Canal with clay; (5) decrease of surface water use by 25% and replacement of it with groundwater; (6) decrease of surface water use by 50% and replacement of it with groundwater; and (7) decrease of surface water use by 75% and replacement of it with groundwater. The removal of one-half of the phreatophytes would result in a decrease in average drawdown in the alluvial aquifer to about 1.74 ft and an increase in base flow of the Solomon River to about 12.3 cu ft/sec. The decrease of surface water supply by 75 % and a corresponding increase in groundwater withdrawal would result in an increase in drawdown in the aquifer to about 2.5 ft and a decrease in base flow to about 6.8 cu ft/sec. (Lantz-PTT)

Water-Resources Investigations Report↗

USGS1989

Simulated effects of future withdrawals on water levels in the northeastern coastal plain aquifers of New Jersey

In the northeastern Coastal Plain of New Jersey, groundwater withdrawals have produced large cones of depression in all four major regional aquifers. Prior to development, water levels in the four aquifers were 20 to 120 ft above sea level and natural groundwater flow was towards Raritan Bay. In 1983, when total withdrawals exceeded 90 million gal/day, water levels were as low as 185 ft below sea level in the Wenonah-Mount Laurel aquifer, 225 ft below sea leval in the Englishtown aquifer system and 52 and 82 ft below sea level in the upper and middle aquifers of the Potomac-Raritan-Magothy aquifer system, respectively. With development, the natural direction of groundwater flow has been reversed, resulting in the movement of saltwater into parts of the upper and middle aquifers of the Potomac-Raritan-Magothy aquifer system. An 11-layer finite-difference model of the entire New Jersey Coastal Plain was used to simulate the effects of six scenarios of future groundwater withdrawals on water levels in the northeastern Coastal Plain of New Jersey through the year 2020. In the simulation with the most severe reduction, most of the groundwater withdrawals in the northeastern and west-central areas of the Coastal Plain were limited to 50% of 1983 withdrawals after 1990. Even with such restrictions, the lowest simulated water levels in the northeastern part of the Coastal Plain for 2010 are still well below sea level. (USGS)

Water-Resources Investigations Report↗

USGS2015

In-situ arsenic removal during groundwater recharge through unsaturated alluvium

OBJECTIVES The purpose of this study was to determine the feasibility and sustainability of in-situ removal of arsenic from water infiltrated through unsaturated alluvium. BACKGROUND Arsenic is naturally present in aquifers throughout the southwestern United States and elsewhere. In January 2006, the U.S. Environmental Protection Agency (EPA) lowered the Maximum Contaminant Level (MCL) for arsenic from 50 to 10 micrograms per liter (g/L). This raised concerns about naturally-occurring arsenic in groundwater. Although commercially available systems using sorbent iron or aluminum oxide resins are available to treat high-arsenic water, these systems are expensive to build and operate, and may generate hazardous waste. Iron and aluminum oxides occur naturally on the surfaces of mineral grains that compose alluvial aquifers. In areas where alluvial deposits are unsaturated, these oxides may sorb arsenic in the same manner as commercial resins, potentially providing an effective low-cost alternative to commercially engineered treatment systems. APPROACH The Antelope Valley within the Mojave Desert of southern California contains a shallow water-table aquifer with arsenic concentrations of 5 g/L, and a deeper aquifer with arsenic concentrations of 30 g/L. Water was pumped from the deep aquifer into a pond and infiltrated through an 80 m-thick unsaturated zone as part of field-scale and laboratory experiments to treat high-arsenic groundwater and recharge the shallow water table aquifer at the site. The field-scale recharge experiment included the following steps: 1) construction of a recharge pond 2) test drilling for sample collection and instrument installation adjacent to the pond 3) monitoring downward migration of water infiltrated from the pond 4) monitoring changes in selected trace-element concentrations as water infiltrated through the unsaturated zone Data from instruments within the borehole adjacent to the pond were supplemented with borehole and surface geophysical data to evaluate the lateral spreading of water as it moved downward through the unsaturated zone. Three laboratory studies were undertaken. Sequential extraction was used to evaluate the abundance of iron, aluminum, and manganese oxides and selected trace elements on operationally defined sites on the surfaces of mineral grains collected before and after infiltration from the pond. Secondly, radio-labeled arsenic-73 microcosm experiments evaluated the potential for incorporation of arsenic sorbed to exchange sites on mineral grains into less reactive crystalline mineral structures with time. Finally, column studies evaluated arsenic sorption and the pH dependence of sorption for selected unsaturated zone materials. RESULTS/CONCLUSIONS Between December 2010 and July 2012, more than 120,000 cubic meters (m3 ) (about 97 acre-feet) of high-arsenic groundwater was pumped from the deep aquifer into a 0.11 hectare (about 0.27 acres) pond and infiltrated though an 80-meter (about 260 feet) thick unsaturated zone to recharge a water-table aquifer. Arsenic concentrations were lowered from 30 to 2 g/L as water infiltrated though the unsaturated zone at the site. Some uranium, possibly associated with past agricultural land use at the site, was mobilized to concentrations as high as 66 g/L within the unsaturated zone during the experiment. Uranium was resorbed and the high uranium concentrations did not reach the water table at the site. Concentrations of other trace elements, including antimony, chromium, vanadium, and selenium were low throughout the study. Infiltration rates from the pond were as high as 0.4 meters per day (1.1 feet per day, ft/d), and the wetting front moved downward about 25 centimeters per day (cm/d) (0.8 ft/d) to a depth of about 50 m (about 165 feet). Clay layers at that depth slowed the downward movement of the wetting front to about 5 cm/d (0.16 ft/d). Lateral movement of the wetting front was monitored using sequential direct-current (DC) surface and sequential electromagnetic (EM) and DC borehole resistivity. Most lateral movement occurred on a clay layer about 50 m (about 165 feet) below land surface. Infiltrated water reached the water table in January 2013. At the water table, the “wetted footprint” of water infiltrated from the pond, indicated by surface resistivity data, was about 13 hectares (about 32 acres). On the basis of data collected at the site, there is enough sorbent material to operate this pond and treat groundwater having an arsenic concentration of 30 g/L to 2 g/L for about 500 years. Toxicity Characteristic Leaching Procedure (TCLP) data showed arsenic concentrations to be below hazardous levels beneath the pond after the experiment. Pond maintenance may be required to keep infiltration rates high, and prevent accumulation of organic material on the pond bottom, although organic material on the pond bottom may increase removal of other trace elements in infiltrated water including chromium, selenium, and vanadium. Laboratory results are consistent with the field data and show sorption of arsenic in 10 cm (0.3 feet) columns to about 2 g/L over a pH range of 6 to 8, and at influent arsenic concentrations as high as 300 g/L, without breakthrough in 50 pore volumes. Column results suggest that the insitu treatment may remove arsenic in a range of hydrogeologic settings, and would not necessarily be restricted to alkaline alluvial aquifers common throughout the southwestern United States. Radiolabeled arsenic-73 experiments show that although arsenic is initially weakly sorbed (and potentially mobile), with time arsenic is incorporated into amorphous materials. One year after sorption onto surface exchange sites, most sorbed arsenic is incorporated into crystalline oxide minerals on the surfaces of primary mineral grains and is less mobile. Results of the study suggest that long-term land use restrictions on sites used for in-situ treatment of arsenic may not be needed to control water applied to surface materials. This minimizes some regulatory concerns about future land use at sites used for in-situ arsenic treatment. However, future land uses that may alter reduction-oxidation conditions in the subsurface should be avoided, such as infiltration of stormwater recharge or recharge with other water having high organic carbon concentrations (including unsewered residential land use, dairy or other confined animal operations).

Report↗