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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.

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USGS2011

Assessment of groundwater/surface-water interaction and simulation of potential streamflow depletion induced by groundwater withdrawal, Uinta River near Roosevelt, Utah

Roosevelt City, Utah, asserts a need for an additional supply of water to meet municipal demands and has identified a potential location for additional groundwater development at the Sprouse well field near the West Channel of the Uinta River. Groundwater is commonly hydraulically linked to surface water and, under some conditions, the pumpage of groundwater can deplete water in streams and other water bodies. In 2008, the U.S. Geological Survey, in cooperation with Roosevelt City, the Utah Department of Natural Resources, and the Ute Indian Tribe, began a study to improve understanding of the local interconnection between groundwater and surface water and to assess the potential for streamflow depletion from future groundwater withdrawals at a potential Roosevelt City development location—the Sprouse well field near the West Channel of the Uinta River. In the study, streamflow gains and losses at the river/aquifer boundary near the well field and changes in those conditions over time were assessed through (1) synoptic measurement of discharge in the stream at multiple sites using tracer-dilution methods, (2) periodic measurement of the vertical hydraulic gradient across the streambed, and (3) continuous measurement of stream and streambed water temperature using heat as a tracer of flow across the streambed. Although some contradictions among the results of the three assessment methods were observed, results of the approaches generally indicated (1) losing streamflow conditions on the West Channel of the Uinta River north of and upstream from the Sprouse well field within the study area, (2) gaining streamflow conditions south of and downstream from the well field, and (3) some seasonal changes in those conditions that correspond with seasonal changes in stream stage and local water-table altitudes. A numerical groundwater flow model was developed on the basis of previously reported observations and observations made during this study, and was used to estimate potential streamflow depletion that might result from future groundwater withdrawals at the Sprouse well field. The model incorporates concepts of transient groundwater flow conditions including fluctuations in groundwater levels and storage, and the distribution of and temporal variations in gains to and losses from streamflow in the West Channel of the Uinta River near the Sprouse well field. Two predictive model simulations incorporated additional future discharge from the Sprouse well field totaling 325 acre-feet annually and biennially during summer months. Results of the predictive model simulations indicate that the water withdrawn by the additional pumping was derived initially from aquifer storage and then, with time, predominantly from streamflow depletion. By the 10th year of the predictive simulation incorporating annual summer pumping from an additional public-supply well in the Sprouse well field, the simulation results indicate that 89 percent of a future annual 325 acre-feet of discharge is derived from depletion of streamflow in the West Channel of the Uinta River. A similar result was observed in a predictive model simulating the same discharge rate but with the new well being pumped every other year.

Utah↗

USGS2011

Effects of experimental passive artificial recharge of treated surface water on water quality in the Equus Beds Aquifer, 2009-2010

Declining water levels and concerns about the migration of a known saltwater plume upgradient from public supply wells prompted the City of Wichita to investigate the feasibility of using artificial recharge to replenish the water supply in the Equus Beds aquifer. After preliminary testing, the City of Wichita began Phase I of the Equus Beds Aquifer Storage and Recovery Project in 2006. In 2009, the City of Wichita installed an experimental passive gravity recharge well and trench system to increase artificial recharge at Recharge Basin 1, one of the six Phase ? recharge sites. The U.S. Geological Survey collected water samples from 13 sites and maintained 8 continuous monitors to test the recharge capacity of the experimental passive recharge system, the effect of the recharge on geochemistry of the aquifer, and the fate of bacteria and viruses present in the recharge water. About 576,000 gallons of treated surface water from the Little Arkansas River were recharged through the passive recharge well and trench system into the Equus Beds aquifer during April 2009. In May 2009, U.S. Geological Survey tests detected that bacterial and viral indicators (total coliform, fecal coliform, Escherichia coli, coliphage virus, and Clostridium perfringens) were entering the Recharge Basin 1 wells through the recharge system and recharge was discontinued. The City of Wichita disconnected the trench collection system from the passive gravity recharge well in July 2009, and in July and August 2009 withdrew 1,825,000 gallons of water from the aquifer at Recharge Basin 1 to remove the recharged water and avoid contamination of the aquifer. The original recharge rate in Recharge Basin 1 was about 10.8 gallons per day per square foot. After installation of the passive recharge system, recharge water entered the aquifer through the passive well at a rate of about 19.2 gallons per day per square foot, a per unit area increase of about 78 percent. During artificial recharge, continuous monitors recorded rising water-level altitudes in the passive gravity recharge well and nearby monitoring wells as water flowed at about 10 feet per day from the passive recharge well toward nearby downgradient monitoring wells. The increase in water level in this area would have the effect of temporarily slowing the eastward migration of saltwater from the nearby Burrton plume. Bacterial and viral indicators were detected in water samples from Recharge Basin 1 sites before and immediately after the installation of the passive gravity recharge well and trench system, during artificial recharge, and after artificial recharge. After water withdrawal in August 2009 and through the end of data collection in March 2010, detections of bacterial and viral indicators in groundwater decreased to densities similar to those before installation of the passive recharge system. Concentrations of chloride in samples collected from the trench, passive gravity recharge well, and nearby monitoring wells increased from an average of 34 milligrams per liter before artificial recharge to an average of 64 milligrams per liter during artificial recharge, reflecting the addition of recharge water with measured chloride concentrations of 62 to 94 milligrams per liter. When water was being pumped out of the aquifer through the passive gravity recharge well, chloride concentrations increased to 94 milligrams per liter in the removed water and increased to 150 milligrams per liter in the deep monitoring well nearest the passive gravity recharge well, indicating that, as water was being pumped from the passive well, water with a large chloride concentration from elsewhere in the aquifer was flowing toward the passive well. Chloride concentrations did not exceed the U.S. Environmental Protection Agency Secondary Drinking Water Regulation of 250 milligrams per liter in any Recharge Basin 1 samples collected as part of the study. Iron concentrations exceeded the U.S. Environmental Protection Agency

Scientific Investigations Report↗

USGS2014

Groundwater and surface-water interaction and potential for underground water storage in the Buena Vista-Salida Basin, Chaffee County, Colorado, 2011

By 2030, the population of the Arkansas Headwaters Region, which includes all of Chaffee and Lake Counties and parts of Custer, Fremont, and Park Counties, Colorado, is forecast to increase about 73 percent. As the region’s population increases, it is anticipated that groundwater will be used to meet much of the increased demand. In September 2009, the U.S. Geological Survey, in cooperation with the Upper Arkansas Water Conservancy District and with support from the Colorado Water Conservation Board; Chaffee, Custer, and Fremont Counties; Buena Vista, Cañon City, Poncha Springs, and Salida; and Round Mountain Water and Sanitation District, began a 3-year study of groundwater and surface-water conditions in the Buena Vista-Salida Basin. This report presents results from the study of the Buena Vista-Salida Basin including synoptic gain-loss measurements and water budgets of Cottonwood, Chalk, and Browns Creeks, changes in groundwater storage, estimates of specific yield, transmissivity and hydraulic conductivity from aquifer tests and slug tests, an evaluation of areas with potential for underground water storage, and estimates of stream-accretion response-time factors for hypothetical recharge and selected streams in the basin. The four synoptic measurements of flow of Cottonwood, Chalk, and Browns Creeks, suggest quantifiable groundwater gains and losses in selected segments in all three perennial streams. The synoptic measurements of flow of Cottonwood and Browns Creeks suggest a seasonal variability, where positive later-irrigation season values in these creeks suggest groundwater discharge, possibly as infiltrated irrigation water. The overall sum of gains and losses on Chalk Creek does not indicate a seasonal variability but indicates a gaining stream in April and August/September. Gains and losses in the measured upper segments of Chalk Creek likely are affected by the Chalk Cliffs Rearing Unit (fish hatchery). Monthly water budgets were estimated for selected segments of five perennial streams (Cottonwood, North Cottonwood, Chalk, and Browns Creeks, and South Arkansas River) in the Buena Vista-Salida Basin for calendar year 2011. Differences between reported diversions and estimated crop irrigation requirements were used to estimate groundwater recharge in the areas irrigated by water supplied from the diversions. The amount of groundwater recharge in all the basins varied monthly; however, the greatest amount of recharge was during June and July for Cottonwood, North Cottonwood, and Chalk Creeks and South Arkansas River. The greatest amount of recharge in 2011 in Browns Creek occurred in July and August. The large seasonal fluctuations of groundwater near irrigated areas in the Buena Vista-Salida Basin indicate that the increased groundwater storage resulting from infiltration of surface-water diversions has dissipated by the following spring. Areas within the Buena Vista-Salida Basin with the potential for underground storage were identified using geographic information system data, including topographic, geologic, and hydrologic data, excluding the mountainous areas that border the Buena Vista-Salida Basin and igneous and metamorphic rock outcrop areas. The areas that met the selection criteria for underground water storage are located on terrace deposits near the Arkansas River and adjacent to its major tributaries. The selected areas also contain much of the irrigated land within the basin; consequently, irrigation ditches and canals could provide a means of conveying water to potential recharge sites.

Colorado↗

USGS2022

Application of a soil-water-balance model to estimate annual groundwater recharge for Long Island, New York, 1900–2019

A soil-water-balance (SWB) model was developed for Long Island, New York, to estimate the potential amount of annual groundwater recharge to the Long Island aquifer system from 1900 to 2019. The SWB model program is a computer code based on a modified Thornthwaite-Mather SWB approach and uses spatially and temporally distributed meteorological, land-cover, and soil properties as input to compute potential daily groundwater recharge. Simulated outputs indicate that island-wide potential groundwater recharge trends, as a percentage of precipitation, have increased approximately 3 percent during the 120-year period. The simulated results account for both climatic and land-cover changes that have occurred during the period. A change from undeveloped (forested land cover) to low- and medium-density residential land cover or land use increased potential groundwater recharge because of a decrease in evapotranspiration. During the 30-year period from 1900 to 1930, the simulated potential average groundwater recharge rate on Long Island was estimated to be 18.50 inches per year (in/yr), or a total of 1,243 million gallons per day, during the 30-year period from 1985 to 2015, the simulated potential average groundwater recharge rate estimate increased to 20.73 in/yr (a total of around 1,393 million gallons per day). During the 1900–2019 simulation period, the potential average annual groundwater recharge rate was about 19.24 in/yr. The data for that period included values for a 3-year meteorological drought from 1963 to 1965, where the mean precipitation was about 26.5 percent lower than the long-term average of 46.7 in/yr, and the potential groundwater recharge rate was about 12.3 in/yr. During a 3-year wet period from 1982 to 1984, where mean precipitation was about 19.6 percent higher than the long-term average, the estimated potential groundwater recharge rate was about 26.8 in/yr.

New York↗

USGS2024

Status of water quality in groundwater resources used for drinking-water supply in the southeastern San Joaquin Valley, 2013–15—California GAMA Priority Basin Project

The California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) investigated water quality of groundwater resources used for drinking-water supplies in the Madera-Chowchilla, Kings, Kaweah, Tule, and Tulare Lake groundwater subbasins of the southeastern San Joaquin Valley during 2013–15. The study focused primarily on groundwater resources used for domestic-supply wells in the southeastern San Joaquin Valley (SESJV-D), which correspond mostly to shallower parts of aquifer systems, compared to the groundwater resources used for public-supply wells in the southeastern San Joaquin Valley (SESJV-P). The investigation had three components: (1) characterization of the status of water quality in the SESJV-D, (2) comparison between water quality in the SESJV-D and SESJV-P, and (3) identification of natural and anthropogenic factors that potentially could affect water quality in these resources. The characterization of water quality in the SESJV-D was based on data collected from 198 domestic wells sampled during 2013–15 by the U.S. Geological Survey (USGS); characterization of water quality in the SESJV-P was based on data collected from 124 wells sampled by the USGS during 2005–18 and an additional 1,577 wells with publicly available data reported to the California State Water Resources Control Board Division of Drinking Water (SWRCB-DDW). Measured concentrations were compared to regulatory and non-regulatory drinking-water quality benchmarks. A grid-based method was used to estimate the areal proportions of each study area and the whole southeastern San Joaquin Valley with high (greater than benchmark concentration), moderate (greater than half of the benchmark for inorganic and one-tenth of the benchmark for organic), and low concentrations relative to those benchmarks. Natural and anthropogenic factors that could affect groundwater quality for the SESJV-D were identified in the context of the hydrogeologic setting of the southeastern San Joaquin Valley. The considered factors represented hydrologic conditions and position in the groundwater flow system (well depth, lateral position, presence of hydric soils, percentage of coarse-grained sediment, and aridity index), land-use characteristics (percentages of agricultural, urban, and natural land use, percentage of orchard or vineyard land use, and densities of septic tanks and underground storage tanks near the wells), and geochemical conditions (groundwater age class, oxidation-reduction class, pH, and dissolved oxygen and bicarbonate concentrations). Factors are compared between SESJV-D and SESJV-P at the scale of the five study areas. One or more inorganic constituents with U.S. Environmental Protection Agency (EPA) or California maximum contaminant levels (MCLs) were detected at high concentrations in 47 percent of the SESJV-D and in 32 percent of the SESJV-P. The inorganic constituents most commonly present at high concentrations in the SESJV-D were nitrate, uranium, and arsenic. Within the SESJV-D, the proportion of the study area with high concentrations of inorganic constituents ranged from 19 percent in Madera-Chowchilla to 60 percent in Kings and Tulare Lake. One or more inorganic constituents with California State Water Resources Control Board Division of Drinking Water secondary maximum contaminant levels (SMCL-CAs) were detected at high concentrations in 14 percent of the SESJV-D and in 19 percent of the SESJV-P. The constituents most commonly present at high concentrations were manganese, iron, and total dissolved solids (TDS). Although the proportion of SESJV-D and SESJV-P with high concentrations of TDS greater than the upper SMCL were similar at 4 percent, the proportion of the SESJV-D with moderate concentrations (between the recommended and upper SMCL-CA), 30 percent, was greater than the proportion of the SESJV-P with moderate concentrations, 12 percent. One or more organic constituents with MCLs were present at high concentrations in 19 percent of the SESJV-D and in 12 percent of the SESJV-P. All the constituents detected at high concentrations in the SESJV-D were fumigants, primarily 1,2,3-trichloropropane (1,2,3-TCP) and 1,2-dibromo-3-chloropropane (DBCP). Fumigants also were the constituents most commonly detected at high concentrations in the SESJV-P, although high concentrations of solvents also were detected. The SESJV-D dataset included analysis of many organic constituents without MCL benchmarks and with detection levels far below drinking water benchmark concentrations; detections at these low concentrations can be used as tracers of anthropogenic influence on groundwater. Pesticides and degradates of pesticides were detected in 60 percent of the SESJV-D; the most frequently detected pesticides were the herbicides simazine, didealkylatrazine (CAAT, a degradate of simazine and atrazine), diuron, and bromacil.

California↗

USGS2024

Comparison of water quality in shallow groundwater near agricultural areas in the Delaware Coastal Plain, 2014 and 2019

The State of Delaware has encouraged agricultural conservation practices to improve nutrient uptake by crops and mitigate nutrient transport to groundwater in the surficial aquifer. To study recent changes in groundwater quality, the U.S. Geological Survey and the Delaware Department of Agriculture (DDA) developed a network of shallow wells near agricultural areas throughout the Delaware Coastal Plain. This network was designed to characterize water quality related to agricultural practices and to detect any recent changes in shallow groundwater quality, in particular groundwater nitrate concentrations. The shallow well network was first sampled in 2014 and resampled in 2019. In 2019, field parameters (including dissolved oxygen, pH, specific conductance, and temperature), major ions, nutrients, stable isotopes of water, and isotopes of nitrate were measured in groundwater samples collected between October and December. Wells were organized into three groups based on their geochemical characteristics measured in 2014: the Agricultural, Urban, and Mixed Groups. Results from the 2019 sampling showed little change in water quality from the 2014 sampling. Land-use factors continued to be the driving influence between groups. Groundwater moves slowly and changes in groundwater quality are likely to respond slowly to changes in conservation practices. Continued sampling of both groundwater quality in this network and monitoring land management practices can help detect groundwater quality trends in the future.

Delaware↗

USGS2003

Effects of Aquifer Development and Changes in Irrigation Practices on Ground-Water Availability in the Santa Isabel Area, Puerto Rico

The alluvial aquifer in the area of Santa Isabel is located within the South Coastal Plain aquifer of Puerto Rico. Variations in precipitation, changes in irrigation practices, and increasing public-supply water demand have been the primary factors controlling water-level fluctuations within the aquifer. Until the late 1970s, much of the land in the study area was irrigated using inefficient furrow flooding methods that required large volumes of both surface and ground water. A gradual shift in irrigation practices from furrow systems to more efficient micro-drip irrigation systems occurred between the late 1970s and the late 1980s. Irrigation return flow from the furrow-irrigation systems was a major component of recharge to the aquifer. By the early 1990s, furrow-type systems had been replaced by the micro-drip irrigation systems. Water levels declined about 20 feet in the aquifer from 1985 until present (February 2003). The main effect of the changes in agricultural practices is the reduction in recharge to the aquifer and total irrigation withdrawals. Increases in ground-water withdrawals for public supply offset the reduction in ground-water withdrawals for irrigation such that the total estimated pumping rate in 2003 was only 8 percent less than in 1987. Micro-drip irrigation resulted in the loss of irrigation return flow to the aquifer. These changes resulted in lowering the water table below sea level over most of the Santa Isabel area. By 2002, lowering of the water table reversed the natural discharge along the coast and resulted in the inland movement of seawater, which may result in increased salinity of the aquifer, as had occurred in other parts of the South Coastal Plain. Management alternatives for the South Coastal Plain aquifer in the vicinity of Santa Isabel include limiting groundwater withdrawals or implementing artificial recharge measures. Another alternative for the prevention of saltwater intrusion is to inject freshwater or treated sewage effluent into wells along the coast. A digital ground-water flow model was developed to provide information for water managers to evaluate some of these alternatives. After calibration of the ground-water model to historical data, four simulations of ground-water management strategies were performed: ground-water conservation, surface infiltration over existing agricultural fields, or infiltration along streams and canals, or injection wells along the coast. Simulations of four alternative water management strategies indicate that current condition of water levels below sea level near the coast can be reversed to raise water levels above sea level by either: (1) about a 27 percent reduction in 2003 ground-water withdrawal rates; (2) application of about 1,700 million gallons per year of artificial recharge over more than half of the current agricultural areas; (3) injection of about 3 million gallons per day (1,095 million gallons per year) of freshwater or treated wastewater in wells distributed along the coast; (4) injection of about 3.5 million gallons per day (1,280 million gallons per year) of freshwater or treated wastewater in wells distributed along canals and streams.

Water-Resources Investigations Report↗

USGS1985

Preliminary assessment of the ground-water resources of the alluvial aquifer, White River valley, Rio Blanco County, Colorado

A preliminary study of the alluvial aquifer in the White River Valley was conducted to assess aquifer extent and the occurrence , availability, and chemical quality of water in the aquifer. The aquifer in the study area underlies 35 square miles. Aquifer width ranges from 0.1 to 1.5 miles and averages 0.5 miles. Saturated thickness ranges from zero to more than 140 feet and averages 22 feet. The aquifer is unconfined except west of the Grand Hogback, where artesian conditions were observed at several locations. Well yields usually are less than 25 gallons per minute. At the Meeker municipal well field in Agency Park, wells reportedly could yield more than 1,000 gallons per minute each. Based on nine aquifer tests, transmissivity ranges from 860 to 93,000 feet squared per day, and hydraulic conductivity ranges from 70 to 1,550 feet per day. The estimated total volume of water in storage in the aquifer in the study area is 103,000 acre-feet. Groundwater type in the eastern part of the study area is calcium bicarbonate; to the west, water type is sodium sulfate. Water in the aquifer is classified as very hard throughout the study area. Specific conductance generally increases from east to west. (USGS)

Water-Resources Investigations Report↗

USGS1987

Geology and hydrology of the deep bedrock aquifers in eastern Colorado

Deep bedrock aquifers are present in rocks of Cretaceous through Pennsylvanian age in eastern Colorado. These aquifers are the Laramie-Fox Hills (the uppermost aquifer studied), Fort Hays-Codell, Dakota-Cheyenne, Entrada-Dockum, Lyons, and Fountain. Structural mapping indicates the aquifers are 2,000 to 9,000 ft below land surface in most of eastern Colorado but outcrop in local areas in a narrow band along the Front Range of the Rocky Mountains. Recharge primarily occurs in outcrops and produces a northerly or easterly groundwater flow to discharge areas along the South Platte or Arkansas Rivers. Deep aquifers also discharge by underflow to Kansas and Nebraska. Some water-yielding strata in the Dakota-Cheyenne aquifer are not in hydraulic connection with the aquifer, and abnormal fluid pressures, trapped hydrocarbons, and high dissolved-solids concentrations are found in these strata. Temperature and dissolved-solids mapping indicate water temperatures of 100 to 210 in northeastern Colorado and a zone of relatively fresh water extending through a 7,000 sq mi area of the Dakota-Cheyenne aquifer in southeastern Colorado. Water levels in the Laramie-Fox Hills aquifer continue to decline as much as 12 ft/yr in local areas near Denver.

Colorado↗

USGS1986

Planning report for the Edwards-Trinity Regional Aquifer-System analysis in central Texas, southeast Oklahoma, and southwest Arkansas

The Edwards-Trinity regional aquifer system supplies more than 0.78 million acre-feet per year (700 million gallons per day) of water for central Texas and small adjacent parts of southeast Oklahoma and southwest Arkansas. The system consists of three major aquifers and at least three minor aquifers in predominantly Cretaceous rocks, which together have an areal extent of about 80,000 square miles. The major aquifers are the Edwards-Trinity (Plateau) in west-central Texas, the Edwards (Balcones Fault Zone) in south-central Texas, and the Trinity in north-central Texas, southeast Oklahoma, and southwest Arkansas. Current (1986) and future concerns about the aquifer system involve the ever-increasing demand for water, most of which is associated with rapid population increase. Decreases in or elimination of spring discharges and encroachment of water from downdip salinewater zones into updip freshwater zones are of primary concern in the area underlain by ttie Edwards (Balcones Fault Zone) aquifer. Water-level declines of several hundred feet in the Trinity aquifer are a serious concern in some metropolitan areas. The Edwards-Trinity regional aquifer-system analysis project, begun in October 1985 and scheduled to be completed by October 1991, is one of a series of similar projects being conducted nationwide. The project is intended to define the hydrogeologic framework, and to describe the geochemistry and groundwater flow of the aquifer system in order to provide a better understanding of the system's long-term water-yielding potential. A multidisciplinary approach will be used in which computer-based digital simulation of flow in the system will be the principal method of hydrogeologic investigation.

Arkansas, Oklahoma, Texas↗

USGS1998

Hydrogeology and simulation of ground-water flow in the Sandstone Aquifer, northeastern Wisconsin

Municipalities in the lower Fox River Valley in northeastern Wisconsin obtain their water supply from a series of permeable sandstones and carbonates of Cambrian to Ordovician age. Withdrawals from this "sandstone aquifer" have resulted in water levels declining at a rate of more than 2 feet per year. The U.S. Geological Survey, in cooperation with the major water utilities in the Fox Cities area, the East Central Wisconsin Regional Planning Commission and the Wisconsin Geological and Natural History Survey, collected hydrogeological data and constructed a quasithree- dimensional, transient ground-water-flow model for use as a tool in assessing the water resources of the sandstone aquifer. The rocks of the Sinnipee Group and Maquoketa Shale form the Maquoketa-Sinnipee confining unit that separates the sandstone aquifer from the overlying upper aquifer, which consists of unconsolidated deposits and permeable dolomite of Silurian age. The confining unit is present in the eastern part of the study area, but is absent in the western part, where the upper aquifer directly overlies the sandstone aquifer. The ground-water-flow model simulates water levels in the two aquifers and vertical flow across the confining unit. Streams and lakes are simulated in the upper aquifer as head-dependent boundaries where the confining unit is absent and as constant head boundaries where the confining unit is present. The sandstone aquifer has constant heads assigned to the southern boundary, which is far from the lower Fox River Valley and coincident with a ground-water divide. The model was calibrated to predevelopment, 1957, and 1990 water levels, and used to simulate steady-state predevelopment conditions and transient conditions from 1880 to 1990. The trend in simulated water levels over time was similar to trends in measured water levels. Simulated base flow to streams was within the calculated range of base flow at gaged streams. A groundwater divide that separates westerly ground-water flow to the Wolf River from easterly flow to the lower Fox River Valley and Lake Michigan was simulated.

Wisconsin↗

USGS2024

Insight into sources of benzene, TCE, and PFOA/PFAS in groundwater at Naval Air Station Whiting Field, Florida, through numerical particle-tracking simulations

Past waste-disposal activities at Naval Air Station Whiting Field (NASWF) have led to elevated concentrations of contaminants in the underlying sand and gravel aquifer. Contaminants include two of the most commonly detected chemicals in groundwater in many countries (benzene and trichloroethylene (TCE)) and the “forever chemicals” per- and poly-fluoroalkyl substances (PFAS) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). A MODFLOW model (the Whiting Field Groundwater Model (WFGM)) was previously developed for NASWF and the surrounding area to simulate groundwater flow. To obtain insight into groundwater flow pathways for the identification of potential source areas, the MODPATH particle-tracking application was applied to the WFGM for three public supply wells and three monitoring wells at NASWF. The travel time to recharge areas was estimated using concentrations of the groundwater age-dating solutes tritium (as helium ingrowth) and chlorofluorocarbons detected in the monitoring wells. Simulated travel times agree with the groundwater ages and indicate that the calibrated WFGM reasonably represents groundwater flow velocities and pathways. The MODPATH simulations confirm suspected on-base source areas to explain chemical detection in the monitoring wells. In contrast, the particle-tracking simulations indicate that potential source areas to the public supply wells include both on- and off-base sources. This is important because PFAS chemicals can have multiple sources, including land application of sludge-based fertilizers. This approach that combines groundwater age dating with particle-tracking simulations can be applied at similar sites characterized by benzene-, TCE-, and PFAS-contaminated groundwater.

Florida↗

USGS2015

Geostatistical borehole image-based mapping of karst-carbonate aquifer pores

Quantification of the character and spatial distribution of porosity in carbonate aquifers is important as input into computer models used in the calculation of intrinsic permeability and for next-generation, high-resolution groundwater flow simulations. Digital, optical, borehole-wall image data from three closely spaced boreholes in the karst-carbonate Biscayne aquifer in southeastern Florida are used in geostatistical experiments to assess the capabilities of various methods to create realistic two-dimensional models of vuggy megaporosity and matrix-porosity distribution in the limestone that composes the aquifer. When the borehole image data alone were used as the model training image, multiple-point geostatistics failed to detect the known spatial autocorrelation of vuggy megaporosity and matrix porosity among the three boreholes, which were only 10 m apart. Variogram analysis and subsequent Gaussian simulation produced results that showed a realistic conceptualization of horizontal continuity of strata dominated by vuggy megaporosity and matrix porosity among the three boreholes.

Groundwater↗

USGS2021

Migration of injected wastewater with high levels of ammonia in a saline aquifer in south Florida

Treated wastewater with high levels of ammonia has been injected, since March 1983 into the deep saline units of the Lower Floridan aquifer (LFA) from a treatment plant near the east coast of Miami-Dade County in southeastern Florida. Monitoring wells in the plant recorded ammonia concentrations above ambient levels at hydrogeologic units located about 1000 ft (304.8 m) above injection depths between 2500 and 2800 ft (762 and 853 m) below sea level. A solute-transport model was developed to assess the horizontal and vertical extent of the injected ammonia, with ammonia moving from the injected zone into the overlying units: the upper semiconfining unit, the uppermost permeable zone of the LFA, and the middle semiconfining units of the Avon Park Formation. Ammonia is assumed to be transported under the effects of local heterogeneity in a porous limestone aquifer with high-salinity ambient groundwater and via upward migration through quasi-vertical pathways. A flow model of the migration of the injected ammonia was calibrated with PEST using head, salinity, and ammonia concentration data measured from 1983 to 2013. Borehole geophysical data support the high permeability of the uppermost permeable zone in the LFA. Average simulated head, normalized salinity, and ammonia concentration residuals over all monitoring wells were −1.37 ft, 0.01, and −0.67 mg/L, respectively. Model results are consistent with undetectable ammonia concentrations in the Upper Floridan aquifer.

Florida↗

USGS2014

Origins and bioavailability of dissolved organic matter in groundwater

Dissolved organic matter (DOM) in groundwater influences water quality and fuels microbial metabolism, but its origins, bioavailability and chemical composition are poorly understood. The origins and concentrations of dissolved organic carbon (DOC) and bioavailable DOM were monitored during a long-term (2-year) study of groundwater in a fractured-rock aquifer in the Carolina slate belt. Surface precipitation was significantly correlated with groundwater concentrations of DOC, bioavailable DOM and chromophoric DOM, indicating strong hydrological connections between surface and ground waters. The physicochemical and biological processes shaping the concentrations and compositions of DOM during its passage through the soil column to the saturated zone are conceptualized in the regional chromatography model. The model provides a framework for linking hydrology with the processes affecting the transformation, remineralization and microbial production of DOM during passage through the soil column. Lignin-derived phenols were relatively depleted in groundwater DOM indicating substantial removal in the unsaturated zone, and optical properties of chromophoric DOM indicated lower molecular weight DOM in groundwater relative to surface water. The prevalence of glycine, γ -aminobutyric acid, and d -enantiomers of amino acids indicated the DOM was highly diagenetically altered. Bioassay experiments were used to establish DOC-normalized yields of amino acids as molecular indicators of DOM bioavailability in groundwater. A relatively small fraction (8 ± 4 %) of DOC in groundwater was bioavailable. The relatively high yields of specific d -enantiomers of amino acids indicated a substantial fraction (15–34 %) of groundwater DOC was of bacterial origin.

Biogeochemistry↗

USGS2015

A comparison of thermal infrared to fiber-optic distributed temperature sensing for evaluation of groundwater discharge to surface water

Groundwater has a predictable thermal signature that can be used to locate discrete zones of discharge to surface water. As climate warms, surface water with strong groundwater influence will provide habitat stability and refuge for thermally stressed aquatic species, and is therefore critical to locate and protect. Alternatively, these discrete seepage locations may serve as potential point sources of contaminants from polluted aquifers. This study compares two increasingly common heat tracing methods to locate discrete groundwater discharge: direct-contact measurements made with fiber-optic distributed temperature sensing (FO-DTS) and remote sensing measurements collected with thermal infrared (TIR) cameras. FO-DTS is used to make high spatial resolution (typically m) thermal measurements through time within the water column using temperature-sensitive cables. The spatialtemporal data can be analyzed with statistical measures to reveal zones of groundwater influence, however, the personnel requirements, time to install, and time to georeference the cables can be burdensome, and the control units need constant calibration. In contrast, TIR data collection, either from handheld, airborne, or satellite platforms, can quickly capture point-in-time evaluations of groundwater seepage zones across large scales. However the remote nature of TIR measurements means they can be adversely influenced by a number of environmental and physical factors, and the measurements are limited to the surface skin temperature of water features. We present case studies from a range of lentic to lotic aquatic systems to identify capabilities and limitations of both technologies and highlight situations in which one or the other might be a better instrument choice for locating groundwater discharge. FO-DTS performs well in all systems across seasons, but data collection was limited spatially by practical considerations of cable installation. TIR is found to consistently locate groundwater seepage zones above and along the streambank, but submerged seepage zones are only well identified in shallow systems (e.g. <0.5 m depth) with moderate flow. Winter data collection, when groundwater is relatively warm and buoyant, increases the water surface expression of discharge zones in shallow systems.

Massachusetts, Michigan, Montana, New York, Pennsy↗

USGS2023

Long short-term memory models to quantify long-term evolution of streamflow discharge and groundwater depth in Alabama

Long short-term memory (LSTM) models have been shown to be efficient for rainfall-runoff modeling, and to a lesser extent, for groundwater depth forecasting. In this study, LSTMs were applied to quantify the spatiotemporal evolution of surface and subsurface hydrographs in Alabama in the Southeastern United States, where water sustainability has not been fully quantified across spatiotemporal scales. First, the surface water LSTM model with extensive dynamic (precipitation and other weather variables) and static (basin characteristics) inputs predicted the main characteristics of streamflow for six years at 19 gauged basins in Alabama. The model tended to underestimate extremely high streamflow but adding drainage density as an input feature slightly improved the predictions of extreme events. Second, to predict the groundwater depth evolution, a groundwater LSTM (GW-LSTM) model was proposed and applied using static inputs capturing the aquifers' hydrogeological properties and dynamic inputs of meteorological information. Three precipitation scenarios were also explored to evaluate the groundwater hydrograph evolution in the next two decades. The GW-LSTM model predicted the general trend of daily groundwater depth fluctuations (at 21 wells distributed across Alabama from 1990 to 2021) including most extremely high groundwater levels, and recovered groundwater depth for locations withheld from model training and validation. This study, therefore, extended the application of LSTMs in quantifying the spatiotemporal evolution of surface water and groundwater, two manifestations of a single integrated resource.

Alabama↗

USGS1998

Application of the top specified boundary layer (TSBL) approximation to initial characterization of an inland aquifer mineralization: 2. Seepage of saltwater through semi-confining layers

This paper presents a generalized basic study that addresses practical needs for an understanding of the major mechanisms involved in the mineralization of groundwater in the Great Bend Prairie aquifer in south- central Kansas. This Quaternary alluvial aquifer and associated surface waters are subject to contamination by saltwater, which in some areas seeps from the deeper Permian bedrock formation into the overlying freshwater aquifer through semiconfining layers. A simplified conceptual model is adopted. It incorporates the freshwater aquifer whose bottom is comprised of a semiconfining layer through which a hydrologically minor but geochemically important saline water discharge seeps into the aquifer. A hierarchy of approximate approaches is considered to analyze the mineralization processes taking place in the aquifer. The recently developed top specified boundary layer (TSBL) approach is very convenient to use for the initial characterization of these processes, and is further adapted to characterization of head-driven seepage through semi-confining layers. TSBL calculations indicate that the seeping saline water may create two distinct new zones in the aquifer: (1) a completely saline zone (CSZ) adjacent to the semiconfining bottom of the aquifer, and (2) a transition zone (TZ) which develops between the CSZ and the freshwater zone. Some possible scenarios associated with the various mineralization patterns are analyzed and discussed.

Journal of Contaminant Hydrology↗