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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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USGS2018

Mechanisms of earthquake‐induced chemical and fluid transport to carbonate groundwater springs after earthquakes

Mechanisms by which hydrochemical changes occur after earthquakes are not well documented. We use the 2016–2017 central Italy seismic sequence, which caused notable hydrochemical transient variations in groundwater springs to address this topic, with special reference to effects on fractured carbonate aquifers. Hydrochemistry measured before and after the earthquakes at four springs at varying distances from the epicenters all showed immediate postmainshock peaks in trace element concentrations but little change in major elements. Most parameters returned to preearthquake values before the last events of the seismic sequence. The source of solutes, particularly trace elements, is longer residence time pore water stored in slow‐moving fractures or abandoned karstic flow paths. These fluids were expelled into the main flow paths after an increase in pore pressure, hydraulic conductivity, and shaking from coseismic aquifer stress. The weak response to the later earthquakes is explained by progressive depletion of high solute fluids as earlier shocks flushed out the stored fluids in the fractures. Spring δ 13 C DIC values closest to a deep magma source to the west became enriched relative to preearthquake values following the 24 August event. This enrichment indicates input from deeply sourced dissolved CO 2 gas after dilation of specific fault conduits. Differences in carbon isotopic responses between springs are attributed to proximity to the deep gaseous CO 2 source. Most of the transient chemical changes seen in the three fractured carbonate aquifers are attributed to local shaking and emptying of isolated pores and fractures and are not from rapid upward movement of deep fluids.

Water Resources Research↗

USGS1996

Analysis of nitrate in near-surface aquifers in the midcontinental United States: An application of the inverse hyperbolic sine Tobit model

A nonnormal and heteroscedastic Tobit model is used to determine the primary factors that affect nitrate concentrations in near-surface aquifers, using data from the U.S. Geological Survey collected in 1991. Both normality and homoscedasticity of errors are rejected, justifying the use of a nonnormal and heteroscedastic model. The following factors are found to have significant impacts on nitrate concentrations in groundwater: well screen interval, depth to top of aquifers, percentages of urban residential, forest land, and pasture within 3.2 km, dissolved oxygen concentration level, and presence of a chemical facility and feedlot. The effects of explanatory variables on nitrate concentration are explored further by calculating elasticities. Dissolved oxygen concentration level has more notable effects on nitrate concentrations in groundwater than other variables.

Water Resources Research↗

USGS2010

Relation of carbon 14 concentrations to saline water contamination of coastal aquifers

Naturally occurring stable or radioactive isotopes may be used in some places to identify the origin of saline water that contaminates some coastal aquifers. In a recent study to determine the origin of saline water in the Ocala Limestone aquifer near Brunswick, Georgia, the following sources were analyzed for C 14 and deuterium concentrations: potable water from the Ocala Limestone, contaminated water from the Ocala Limestone, saune water from the underlying Claiborne Group, and nearby ocean water. The chloride concentration of the groundwater ranges from about 25 ppm in the potable water to more than 2000 ppm in the deeper part of the Claiborne Group. From an interpretation of piezometric maps and other hydrologic data, previous investigators had concluded that the source of the contaminating water was the Claiborne Group and not the nearby ocean. The essentially uniform range of low values of −965 to −987‰ of the modern standard (National Bureau Standard C 14 oxalic acid) for the C 14 activity of the groundwater samples (regardless of the degree of contamination) is in agreement with this conclusion. If recent ocean water, which had a C 14 value of +285‰, were the source of contamination, the contaminated water would have had a C 14 activity higher than the activity of the fresh water. Deuterium analyses are not inconsistent with the interpretation that water from the Claiborne Group, rather than recent ocean water, is the source of the contaminating water. The concurrence of the hydrologic and the isotopic data in this area where the hydrology is well known suggests that isotopic analysis may be used to identify the origin of water in different portions of a hydrologic environment.

Georgia↗

USGS2010

Aquifer reclamation design: The use of contaminant transport simulation combined with nonlinear programing

A simulation-management methodology is demonstrated for the rehabilitation of aquifers that have been subjected to chemical contamination. Finite element groundwater flow and contaminant transport simulation are combined with nonlinear optimization. The model is capable of determining well locations plus pumping and injection rates for groundwater quality control. Examples demonstrate linear or nonlinear objective functions subject to linear and nonlinear simulation and water management constraints. Restrictions can be placed on hydraulic heads, stresses, and gradients, in addition to contaminant concentrations and fluxes. These restrictions can be distributed over space and time. Three design strategies are demonstrated for an aquifer that is polluted by a constant contaminant source: they are pumping for contaminant removal, water injection for in-ground dilution, and a pumping, treatment, and injection cycle. A transient model designs either contaminant plume interception or in-ground dilution so that water quality standards are met. The method is not limited to these cases. It is generally applicable to the optimization of many types of distributed parameter systems.

Water Resources Research↗

USGS2009

Fractionation of stable isotopes in perchlorate and nitrate during in situ biodegradation in a sandy aquifer

An in situ experiment was performed in a shallow alluvial aquifer in Maryland to quantify the fractionation of stable isotopes in perchlorate (Cl and O) and nitrate (N and O) during biodegradation. An emulsified soybean oil substrate that was previously injected into this aquifer provided the electron donor necessary for biological perchlorate reduction and denitrification. During the field experiment, groundwater extracted from an upgradient well was pumped into an injection well located within the in situ oil barrier, and then groundwater samples were withdrawn for the next 30 h. After correction for dilution (using Br– as a conservative tracer of the injectate), perchlorate concentrations decreased by 78% and nitrate concentrations decreased by 82% during the initial 8.6 h after the injection. The observed ratio of fractionation effects of O and Cl isotopes in perchlorate (e18O/e37Cl) was 2.6, which is similar to that observed in the laboratory using pure cultures (2.5). Denitrification by indigenous bacteria fractionated O and N isotopes in nitrate at a ratio of ~0.8 (e18O/e15N), which is within the range of values reported previously for denitrification. However, the magnitudes of the individual apparent in situ isotope fractionation effects for perchlorate and nitrate were appreciably smaller than those reported in homogeneous closed systems (0.2 to 0.6 times), even after adjustment for dilution. These results indicate that (1) isotope fractionation factor ratios (e18O/e37Cl, e18O/e15N) derived from homogeneous laboratory systems (e.g. pure culture studies) can be used qualitatively to confirm the occurrence of in situ biodegradation of both perchlorate and nitrate, but (2) the magnitudes of the individual apparent e values cannot be used quantitatively to estimate the in situ extent of biodegradation of either anion.

Environmental Chemistry↗

USGS2013

Impacts on groundwater recharge areas of megacity pumping: analysis of potential contamination of Kolkata, India, water supply

Water supply to the world's megacities is a problem of quantity and quality that will be a priority in the coming decades. Heavy pumping of groundwater beneath these urban centres, particularly in regions with low natural topographic gradients, such as deltas and floodplains, can fundamentally alter the hydrological system. These changes affect recharge area locations, which may shift closer to the city centre than before development, thereby increasing the potential for contamination. Hydrogeological simulation analysis allows evaluation of the impact on past, present and future pumping for the region of Kolkata, India, on recharge area locations in an aquifer that supplies water to over 13 million people. Relocated recharge areas are compared with known surface contamination sources, with a focus on sustainable management of this urban groundwater resource. The study highlights the impacts of pumping on water sources for long-term development of stressed city aquifers and for future water supply in deltaic and floodplain regions of the world.

West Bengal↗

USGS2004

Chemical and carbon isotopic composition of dissolved organic carbon in a regional confined methanogenic aquifer

This study demonstrates the advantage of a combined use of chemical and isotopic tools to understand the dissolved organic carbon (DOC) cycle in a regional confined methanogenic aquifer. DOC concentration and carbon isotopic data demonstrate that the soil zone is a primary carbon source of groundwater DOC in areas close to recharge zones. An in-situ DOC source linked to organic rich sediments present in the aquifer matrix is controlling the DOC pool in the central part of the groundwater flow system. DOC fractions, 13C-NMR on fulvic acids and 14C data on DOC and CH4 support the hypothesis that the in-situ DOC source is a terrestrial organic matter and discard the Ordovician bedrock as a source of DOC. ?? 2004 Taylor and Francis Ltd.

Isotopes in Environmental and Health Studies↗

USGS2023

Temporal trends in agricultural water use and the relationships to hydroclimatic factors in the High Plains aquifer region

The High Plains aquifer (HPA) is the primary water source for agricultural irrigation in the US Great Plains. The water levels in many locations of the aquifer have declined steadily over the past several decades because the rate of water withdrawals exceeds recharge, which has been a serious concern to the water resources management in the region. We evaluated temporal trends and variations in agricultural water use and hydroclimatic variables including precipitation, air temperature, reference evapotranspiration, runoff, groundwater level, and terrestrial water storage across the HPA region for different periods from 1985 to 2020 at the grid, county, or region scale. The results showed that water withdrawals decreased from 21.3 km 3 /year in 1985 to 18.2 km 3 /year in 2015, while irrigated croplands increased from 71,928 km 2 in 1985 to 78,464 km 2 in 2015 in the entire HPA. The hydroclimatic time-series showed wetting trends in most of the northern HPA, but drying and warming trends in the southern region from 1985 to 2020. The groundwater level time-series indicated flat trends in the north, but significant declining in the central and southern HPA. Trends in irrigation water withdrawals and irrigation area across the HPA were controlled by the advancement of irrigation systems and technologies and the management of sustainable water use, but also were affected by dynamical changes in the hydroclimatic conditions.

Journal of the American Water Resources Associatio↗

USGS2009

Flowpath independent monitoring of reductive dechlorination potential in a fractured rock aquifer

The flowpath dependent approaches that are typically employed to assess biodegradation of chloroethene contaminants in unconsolidated aquifers are problematic in fractured rock settings, due to difficulties defining discrete groundwater flowpaths in such systems. In this study, the variation in the potential for chloroethene biodegradation with depth was evaluated in a fractured rock aquifer using two flowpath independent lines of field evidence: (1) the presence of the three biochemical prerequisites [electron donor(s), chloroethene electron acceptor(s), and chlororespiring microorganism(s)] for efficient chloroethene chlororespiration and (2) the in situ accumulation of chloroethene reductive dechlorination daughter products. The validity of this approach was assessed by comparing field results with the results of [1, 2‐ 14 C] cis ‐DCE microcosm experiments. Microcosms were prepared with depth‐specific core material, which was crushed and emplaced in discrete packer intervals for 1 year to allow colonization by the indigenous microbial community. Packer intervals characterized by significant electron donor concentrations, elevated numbers of chlororespiring microorganisms, and high reductive dechlorination product to parent contaminant ratios correlated well with the production of 14 C‐labeled reductive dechlorination products in the microcosm experiments. These results indicate that, in the absence of information on discrete groundwater flowpaths, a modified approach emphasizing flowpath independent lines of evidence can provide insight into the temporal and spatial variability of contaminant biodegradation in fractured rock systems.

Ground Water Monitoring and Remediation↗

USGS1994

Autotrophic, hydrogen-oxidizing, denitrifying bacteria in groundwater, potential agents for bioremediation of nitrate contamination

Addition of hydrogen or formate significantly enhanced the rate of consumption of nitrate in slurried core samples obtained from an active zone of denitrification in a nitrate-contaminated sand and gravel aquifer (Cape Cod, Mass.). Hydrogen uptake by the core material was immediate and rapid, with an apparent K m of 0.45 to 0.60 μM and a V max of 18.7 nmol cm -3 h -1 at 30°C. Nine strains of hydrogen-oxidizing denitrifying bacteria were subsequently isolated from the aquifer. Eight of the strains grew autotrophically on hydrogen with either oxygen or nitrate as the electron acceptor. One strain grew mixotrophically. All of the isolates were capable of heterotrophic growth, but none were similar to Paracoccus denitrificans , a well-characterized hydrogen-oxidizing denitrifier. The kinetics for hydrogen uptake during denitrification were determined for each isolate with substrate depletion progress curves; the K m s ranged from 0.30 to 3.32 μM, with V max s of 1.85 to 13.29 fmol cell -1 h -1 . Because these organisms appear to be common constituents of the in situ population of the aquifer, produce innocuous end products, and could be manipulated to sequentially consume oxygen and then nitrate when both were present, these results suggest that these organisms may have significant potential for in situ bioremediation of nitrate contamination in groundwater.

Massachusetts↗

USGS1986

Application of seismic refraction methods in groundwater modeling studies in New England (USA)

Seismic refraction studies were conducted over unconfined glacial aquifers in New England to determine: 1) depth of the underlying bedrock; 2) depth of the water table; 3) saturated thickness of the aquifer in areas not accessible to heavy drilling equipment; 4) areas where thick, unsaturated sediments overlie thickly saturated parts of the aquifer; and 5) locations of test holes and type of drilling equipment needed. These data were used in groundwater models and provided parameter values that required few adjustments during calibration. -from Author

New England↗

USGS2006

Continuous resistivity profiling to delineate submarine groundwater discharge - Examples and limitations

Aquifer-ocean interaction, saline intrusion, and submarine groundwater discharge (SGD) are emerging topics in hydrology and oceanography with important implications for water-resource management and estuarine ecology. Although the threat of saltwater intrusion has long been recognized in coastal areas, SGD has, until recently, received much less attention. It is clear that SGD constitutes a major nutrient flux to coastal waters, with implications for estuarine ecology, eutrophication, and loss of coral reefs; however, fundamental questions regarding SGD remain unanswered: What are the spatial and temporal distributions of SGD offshore? How do seasonal and storm-related variations in aquifer recharge affect SGD flux and nutrient loading? What controls do aquifer structure and heterogeneity impose? How are SGD and saline recirculation related? Geophysical methods can provide insights to help answer these questions and improve the understanding of this intriguing and environmentally relevant hydrologic phenomenon.

Leading Edge (Tulsa, OK)↗

USGS2010

Habitat use by fishes in groundwater-dependent streams of southern Oklahoma

Habitat use by fishes in groundwater-dependent ecosystems with springs and spring-fed creeks is not widely studied or well understood. We evaluated habitat use by three disjunct populations of fish species ( Phoxinus erythrogaster , Nocomis asper and Etheostoma microperca ) and, a widespread species, E. spectabile in spring-fed streams draining the Arbuckle-Simpson aquifer of southern Oklahoma. Habitat preference for each species was classified based on depth, velocity, substrate and cover. Phoxinus erthyrogaster and N. asper were associated with pools with little cover, while E. microperca was found in heavily vegetated areas. Etheostoma spectabile used habitat in riffles with rapid velocity and large substrate types. We classified habitat selection and avoidance with Chesson's α and observed significant differences in habitat use among species in the study sites. Overall differences in habitat use for P. erythrogaster among the three study sites were primarily related to differences in available habitat between springs. Our study provides vital ecological information about disjunct populations of groundwater-dependent fishes in an aquifer that is experiencing development pressure for water abstraction.

Oklahoma↗

USGS2012

Groundwater and surface-water exchange and resultingnNitrate dynamics in the Bogue Phalia Basin in northwestern Mississippi

During April 2007 through September 2008, the USGS collected hydrogeologic and water-quality data from a site on the Bogue Phalia to evaluate the role of groundwater and surface-water interaction on the transport of nitrate to the shallow sand and gravel aquifer underlying the Mississippi Alluvial Plain in northwestern Mississippi. A two-dimensional groundwater/surface-water exchange model was developed using temperature and head data and VS2DH, a variably saturated flow and energy transport model. Results from this model showed that groundwater/surface-water exchange at the site occurred regularly and recharge was laterally extensive into the alluvial aquifer. Nitrate was consistently reported in surface-water samples ( n = 52, median concentration = 39.8 μmol/L) although never detected in samples collected from in-stream piezometers or shallow monitoring wells adjacent to the stream ( n = 46). These two facts, consistent detections of nitrate in surface water and no detections of nitrate in groundwater, coupled with model results that indicate large amounts of surface water moving through an anoxic streambed, support the case for denitrification and nitrate loss through the streambed.

Mississippi↗

USGS2010

Sustainability of natural attenuation of nitrate in agricultural aquifers

Increased concentrations of nitrate in groundwater in agricultural areas, coinciding with increased use of chemical and organic fertilizers, have raised concern because of risks to environmental and human health. At some sites, these problems are mitigated by natural attenuation of nitrate as a result of microbially mediated reactions. Results from U.S. Geological Survey (USGS) research under the National Water-Quality Assessment (NAWQA) program show that reactions of dissolved nitrate with solid aquifer minerals and organic carbon help lower nitrate concentrations in groundwater beneath agricultural fields. However, increased fluxes of nitrate cause ongoing depletion of the finite pool of solid reactants. Consumption of the solid reactants diminishes the capacity of the aquifer to remove nitrate, calling into question the long-term sustainability of these natural attenuation processes.

Fact Sheet↗

USGS2010

Potentiometric Surface of the Lower Patapsco Aquifer in Southern Maryland, September 2009

This report presents a map showing the potentiometric surface of the lower Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2009. The map is based on water-level measurements in 64 wells. The highest measured water level was 110 feet above sea level near the northwestern boundary and outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined towards well fields at Severndale, Broad Creek, and Arnold. The measured groundwater levels were 99 feet below sea level at Severndale, 50 feet below sea level at Broad Creek, and 36 feet below sea level at Arnold. There was also a cone of depression in Charles County that includes Waldorf, La Plata, Indian Head, and the Morgantown power plant. The groundwater levels measured were as low as 215 feet below sea level at Waldorf, 149 feet below sea level at La Plata, 121 feet below sea level at Indian Head, and 96 feet below sea level at the Morgantown power plant. The map also shows well yield in gallons per day for 2008 at wells or well fields.

Open-File Report↗

USGS2013

Effect of simulated tree canopy removal on a municipal wellfield in the Puget Sound aquifer system, Thurston County, Washington

Effects of tree canopy removal on a wellfield were simulated using a groundwater flow model characteristic of hydrogeologic settings in the Puget Sound aquifer system. Effects were estimated according to simulated changes in flow patterns that may result from tree canopy removal associated with varying degrees of residential development. The flow model used was a modified version of a model of the hydrogeologic setting in Thurston County, Washington; the wellfield was one planned for Olympia, Washington, and the canopy modifications spanned a range of possible land use change scenarios. The relative effects of tree canopy removal were estimated in terms of potential changes in capture zones for the wellfield and groundwater levels. Because of the depth of the wellfield and the dispersal of the effects from changes in recharge at ground surface, potential changes in wellfield capture zones and groundwater levels were discernible but small compared to other possible influences.

Washington↗

USGS2023

Groundwater quality in the Mohawk and western New York River Basins, New York, 2016

Water samples were collected from July through December 2016 from 9 production wells and 13 domestic wells in the Mohawk River Basin, and from 17 production wells and 17 domestic wells in the western New York River Basins. The samples were collected and processed by using standard U.S. Geological Survey methods and were analyzed for 320 physicochemical properties and constituents, including dissolved gases, major ions, nutrients, trace elements, pesticides, volatile organic compounds, radionuclides, and indicator bacteria, to characterize groundwater quality in the basins. Analytical results are provided in the companion U.S. Geological Survey data release titled “Groundwater Quality Data From the Mohawk and Western New York River Basins, New York, 2016.” The Mohawk River Basin study area covers 3,500 square miles in New York. Of the 22 wells sampled in the Mohawk River Basin, 8 are completed in sand and gravel, and 14 are completed in bedrock aquifers. Most constituents in the samples from the Mohawk River Basin were present in concentrations below the maximum contaminant levels used in public supply drinking-water regulations by the New York State Department of Health and the U.S. Environmental Protection Agency. Values for some of the properties and concentrations of some constituents—pH, color, iron, manganese, aluminum, sodium, chloride, dissolved solids, radon-222, and heterotrophic plate count—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards. The western New York River Basins study area covers 5,340 square miles in western New York and includes parts of the Lake Erie and Niagara River Basins, the western Lake Ontario Basin (between the Niagara River and Genesee River Basins), and the Allegheny River Basin. Of the 34 wells sampled in the western New York River Basins, 16 are completed in sand and gravel, and 18 are completed in bedrock aquifers. Most constituents in the samples from the western New York River Basins were present in concentrations below the maximum contaminant levels used in public supply drinking-water regulations by the New York State Department of Health and the U.S. Environmental Protection Agency. Values for some of the properties and concentrations of some constituents—color, chloride, sodium, dissolved solids, iron, manganese, aluminum, arsenic, barium, radon-222, methane, total coliform bacteria, fecal coliform bacteria, and Escherichia coli bacteria—sometimes equaled or exceeded primary, secondary, or proposed drinking-water standards.

New York↗