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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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USGS2023

One Ranney well can make a difference: The impacts of a radial collector well on groundwater level and quality in the Cedar River alluvial aquifer

The City of Cedar Rapids, Iowa, depends on groundwater from the Cedar River alluvial aquifer for residential and industrial use. In 2020, the city completed an additional radial collector well, or Ranney well, and was concerned that pumping from the well at high rates may lower water level elevations in the aquifer, reduce yields from nearby production wells, and change the quality of produced water. During an operational test of the well's pumps, the U.S. Geological Survey and the city collected water level and water quality data to evaluate the effects of increased pumping rates on the aquifer and nearby production wells. Results indicated that a high rate of pumping from the new well caused sustained declines in water levels near the well and other nearby production wells, and, if maintained, the aquifer water level in the vicinity would continue to decline to levels observed during the 2012 drought. Aquifer specific conductance and temperature were altered and matched trends and values of the river, and river-to-well travel time was shortened from 7-17 days to about 3 days. Results may also provide insights to other municipal water resource managers when considering wellfield design, production expectations, and long-term management strategies for radial collector well production during drought, low streamflow, and times when high concentrations of nitrate-N or organic pesticide compounds in the river may limit production options.

Iowa↗

USGS2008

Inverse geochemical modeling of groundwater evolution with emphasis on arsenic in the Mississippi River Valley alluvial aquifer, Arkansas (USA)

Inverse geochemical modeling (PHREEQC) was used to identify the evolution of groundwater with emphasis on arsenic (As) release under reducing conditions in the shallow (25-30 m) Mississippi River Valley Alluvial aquifer, Arkansas, USA. The modeling was based on flow paths defined by high-precision (??2 cm) water level contour map; X-ray diffraction (XRD), scanning electron microscopic (SEM), and chemical analysis of boring-sediments for minerals; and detailed chemical analysis of groundwater along the flow paths. Potential phases were constrained using general trends in chemical analyses data of groundwater and sediments, and saturation indices data (MINTEQA2) of minerals in groundwater. Modeling results show that calcite, halite, fluorite, Fe oxyhydroxide, organic matter, H2S (gas) were dissolving with mole transfers of 1.40E - 03, 2.13E - 04, 4.15E - 06, 1.25E + 01, 3.11, and 9.34, respectively along the dominant flow line. Along the same flow line, FeS, siderite, and vivianite were precipitating with mole transfers of 9.34, 3.11, and 2.64E - 07, respectively. Cation exchange reactions of Ca2+ (4.93E - 04 mol) for Na+ (2.51E - 04 mol) on exchange sites occurred along the dominant flow line. Gypsum dissolution reactions were dominant over calcite dissolution in some of the flow lines due to the common ion effect. The concentration of As in groundwater ranged from <0.5 to 77 ??g/L. Twenty percent total As was complexed with Fe and Mn oxyhydroxides. The redox environment, chemical data of sediments and groundwater, and the results of inverse geochemical modeling indicate that reductive dissolution of Fe oxyhydroxide is the dominant process of As release in the groundwater. The relative rate of reduction of Fe oxyhydroxide over SO42 - with co-precipitation of As into sulfide is the limiting factor controlling dissolved As in groundwater. ?? 2007 Elsevier B.V. All rights reserved.

Journal of Hydrology↗

USGS2016

Sustainability of groundwater supplies in the Northern Atlantic Coastal Plain aquifer system

Groundwater is the Nation’s principal reserve of freshwater. It provides about half our drinking water, is essential to food production, and facilitates business and industry in developing economic well-being. Groundwater is also an important source of water for sustaining the ecosystem health of rivers, wetlands, and estuaries throughout the country. The decreases in groundwater levels and other effects of pumping that result from large-scale development of groundwater resources have led to concerns about the future availability of groundwater to meet all our Nation’s needs. Assessments of groundwater availability provide the science and information needed by the public and decision makers to manage water resources and use them responsibly. The U.S. Geological Survey (USGS) is conducting large-scale multidisciplinary regional studies of groundwater availability as part of its ongoing assessments of the principal aquifers of the Nation. These regional studies are intended to provide citizens, communities, and natural resource managers with knowledge of the status of the Nation’s groundwater resources and how changes in land use, water use, and climate have affected and are likely to affect those resources now and in the future.

Fact Sheet↗

USGS2021

Effect of groundwater withdrawals, river stage, and precipitation on water-table elevations in the Iowa River alluvial aquifer near Tama, Iowa, 2017–20

The Sac and Fox Tribe of the Mississippi in Iowa is the only federally recognized Tribe in the State of Iowa and is commonly known as the Meskwaki Nation. The Tribe owns more than 8,100 acres, referred to as the “Meskwaki Settlement.” The Meskwaki Settlement uses a well field that withdraws water from the Iowa River alluvial aquifer (IRAA) to supply drinking water to members of the Tribe. Increased severity and timing of flooding and drought conditions, coupled with water-quality concerns in the Iowa River, have prompted the Meskwaki Nation to start identifying tools to provide a better understanding of how extreme climate events (changes in streamflow, flood frequency, and magnitude and persistence of drought conditions), increasing water-supply demands, and groundwater storage depletion will affect water availability in the IRAA. From June 2017 through September 2020, the U.S. Geological Survey, in cooperation with the Meskwaki Nation, collected continuous and discrete groundwater level data from 11 wells in a U.S. Geological Survey monitoring-well network. Groundwater level data collected at these wells were assessed with daily precipitation data and compared to changes in stream level elevations and daily groundwater withdrawals to determine how these changes affect groundwater-table elevations. Results from this study could be used to guide the development of a conceptual model for groundwater flow and a groundwater flow model for the IRAA to quantify and forecast the effect of groundwater withdrawals, Iowa River streamflow, and local precipitation on the water table in the IRAA.

Iowa↗

USGS2013

The effects of withdrawals and drought on groundwater availability in the Northern Guam Lens Aquifer, Guam

Owing to population growth, freshwater demand on Guam has increased in the past and will likely increase in the future. During the early 1970s to 2010, groundwater withdrawals from the limestone Northern Guam Lens Aquifer, the main source of freshwater on the island, tripled from about 15 to 45 million gallons per day. Because of proposed military relocation to Guam and expected population growth, freshwater demand on Guam is projected to increase further. The expected increased demand for groundwater has led to concern over the long-term sustainability of withdrawals from existing and proposed wells. A three-dimensional numerical groundwater flow and transport model was developed to simulate the effects of hypothetical withdrawal and recharge scenarios on water levels and on the transition zone between freshwater and saltwater. The model was constructed by using average recharge during 1961–2005 and withdrawals from 2010. Hydraulic properties used to construct the model were initially based on published estimates but ultimately were adjusted to obtain better agreement between simulated and measured water levels and salinity profiles in the modeled area. Two hypothetical groundwater withdrawal scenarios were simulated: no withdrawal to simulate predevelopment conditions and withdrawal at 2010 rates under a 5-year drought. Simulation results indicate that prior to pumping; the fresh-water lens was 10 to 50 feet thicker in the Yigo-Tumon basin and more than 50 feet thicker in the Hagåtña basin. Results also indicate that continuing the 2010 withdrawal distribution during a 5-year drought would result in decreased water levels, a thinner freshwater lens, and increased salinity of water pumped from wells. The available water with an acceptable salinity (chloride concentration less than 200 milligrams per liter) would decrease from about 34 million gallons per day to 11.5 million gallons per day after 5 years but recover to pre-drought levels 5 years after the return of average recharge conditions. Five additional scenarios were simulated to assess groundwater demand projections and proposed new well sites for the Department of Defense and Guam Water Authority wells under average and drought conditions. Simulation results from these projected withdrawal scenarios indicate decreased water levels, a thinner freshwater lens, increased water salinity, and unacceptable salinity at several current withdrawal sites. However, for the scenario including projected U.S. Marine Corps demands (46.62 million gallons per day, including 10 proposed wells) more than 40 million gallons per day of the withdrawn groundwater remains in the acceptable category. During a 5-year drought, this same pumping distribution results in only about 15 million gallons per day of withdrawn groundwater having acceptable salinity. A scenario in which groundwater withdrawal was redistributed in an attempt to maximize withdrawal while maintaining acceptable salinities in the withdrawn water was simulated. The redistributed withdrawal simulates about 47 million gallons per day of withdrawal with more than 41 million gallons per day of withdrawal with acceptable salinity.

Guam;Northern Guam Lens Aquifer↗

USGS2019

Estimation of groundwater flow through Yucca Flat based on a multiple-well aquifer test at well ER-6–1–2 main , Nevada National Security Site, southern Nevada

The rate of groundwater flow past underground nuclear testing areas in Yucca Flat at the Nevada National Security Site, southern Nevada, was estimated using results from the ER-6-1-2 main multiple-well aquifer test (MWAT), done during February 5–July 23, 2004. Drawdowns in 13 observation wells were evaluated from pumping in well ER-6-1-2 main and used as observations in a regional groundwater-flow model to estimate the groundwater-flow rate. Flow from southern Yucca Flat regionally was constrained by detecting drawdown in Tracer Well 3 , which is 33 miles south-southwest of pumping well ER-6-1-2 main . Predevelopment flow, the ER-6-1-2 main MWAT, and regional groundwater pumping were simulated in separate models that jointly informed estimates of transmissivity and specific-yield distributions. Predevelopment flow constrained groundwater-flow estimates from southern Yucca Flat because the steady-state model correctly simulated regional groundwater discharges in the Ash Meadows groundwater basin and the surrounding basins. Less than 600 acre-feet per year of groundwater moves from underground nuclear testing areas and flows south of well ER-6-1-2 main in southern Yucca Flat.

Nevada↗

USGS2012

Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO 3- ), iron (Fe 2+ ), manganese (Mn 2+ ), and sulfate (SO 4 2- ). Redox conditions were evaluated also based on methane (CH 4 ), excess nitrogen gas (N 2 ) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.

New Hampshire↗

USGS1984

Groundwater-flow parameter estimation and quality modeling of the Equus Beds aquifer in Kansas, U.S.A.

The salinity problems created in the Burrton area as a result of poor oil-field brine disposal practices of the past continue to be a major concern to the area depending on the Equus Beds aquifer for water, including the City of Wichita, Kansas. In this paper, an attempt is made to predict where and how fast the brine plume will move in this area, and what the average chloride concentrations in different parts of the aquifer are. In order to make such predictions, it was necessary to get a calibrated model of the groundwater-flow velocity field. Multiple regression analysis is used for parameter estimation of the steady-state groundwater-flow equation applied in the most critical area of the Equus Beds aquifer. Results of such an analysis produced a correlation coefficient of 0.992 between calculated and observed values of hydraulic head. A chloride transport modeling effort is then carried out despite some serious data deficiencies, the significance of which are evaluated through sensitivity analysis. Thus, starting with the quasi steady-state conditions of the early 1940's, it was possible to match the present chloride distribution satisfactorily. Chloride concentration predictions made for the year 2000 indicate that the quality of the Wichita well-field waters will not generally deteriorate from their present condition by that time.

Kansas↗

USGS2014

Flow and sorption controls of groundwater arsenic in individual boreholes from bedrock aquifers in central Maine, USA

To understand the hydrogeochemical processes regulating well water arsenic (As) evolution in fractured bedrock aquifers, three domestic wells with [As] up to 478 μg/L are investigated in central Maine. Geophysical logging reveals that fractures near the borehole bottom contribute 70-100% of flow. Borehole and fracture water samples from various depths show significant proportions of As (up to 69%) and Fe (93-99%) in particulates (>0.45 μm). These particulates and those settled after a 16-day batch experiment contain 560-13,000 g/kg of As and 14-35% weight/weight of Fe. As/Fe ratios (2.5-20 mmol/mol) and As partitioning ratios (adsorbed/dissolved [As], 20,000-100,000 L/kg) suggest that As is sorbed onto amorphous hydrous ferric oxides. Newly drilled cores also show enrichment of As (up to 1300 mg/kg) sorbed onto secondary iron minerals on the fracture surfaces. Pumping at high flow rates induces large decreases in particulate As and Fe, a moderate increase in dissolved [As] and As(III)/As ratio, while little change in major ion chemistry. The δD and δ 18 O are similar for the borehole and fracture waters, suggesting a same source of recharge from atmospheric precipitation. Results support a conceptual model invoking flow and sorption controls on groundwater [As] in fractured bedrock aquifers whereby oxygen infiltration promotes the oxidation of As-bearing sulfides at shallower depths in the oxic portion of the flow path releasing As and Fe; followed by Fe oxidation to form Fe oxyhydroxide particulates, which are transported in fractures and sorb As along the flow path until intercepted by boreholes. In the anoxic portions of the flow path, reductive dissolution of As-sorbed iron particulates could re-mobilize As. For exposure assessment, we recommend sampling of groundwater without filtration to obtain total As concentration in groundwater.

Maine↗

USGS2024

Beyond the wedge: Impact of tidal streams on salinization of groundwater in a coastal aquifer stressed by pumping and sea-level rise

Saltwater intrusion (SWI) is a well-studied phenomenon that threatens the freshwater supplies of coastal communities around the world. The development and advancement of numerical models has led to improved assessment of the risk of salinization. However, these studies often fail to include the impact of surface waters as potential sources of aquifer salinity and how they may impact SWI. Based on field-collected data, we developed a regional, variable-density groundwater model using SEAWAT for east Dover, Delaware. In this location, major users of groundwater from the surficial aquifer are the City of Dover and irrigation for agriculture. Our model includes salinized marshland and tidal streams, along with irrigation and municipal pumping wells. Model scenarios were run for 100 years and included changes in pumping rates and sea-level rise (SLR). We examined how these drivers of SWI affect the extent and location of salinization in the surficial aquifer by evaluating differences in chloride concentration near surface waters and the subsurface freshwater-saltwater interface. We found the presence of the marsh inverts the typical freshwater-saltwater wedge interface and that the edge of the interface did not migrate farther inland. Additionally, we found that tidal streams are the dominant pathways of SWI at our site with salinization from streams being exacerbated by SLR. Our results also show that spatial distribution of pumping affects both the magnitude and extent of salinization, with an increase in concentrated pumping leading to more intensive salinization than a more widely distributed increase of the same total pumping volume.

Delaware↗

USGS2004

The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer

We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As) in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1) the uncontaminated zone above the sewage plume [350 μ M dissolved oxygen (DO), p H 5.9]; (2) the suboxic zone (5 μ M DO, p H 6.2, elevated concentrations of sewage-derived phosphate and nitrate); and (3) the anoxic zone [dissolved iron(II) 100–300 μ M, p H 6.5–6.9, elevated concentrations of sewage-derived phosphate]. Sediments are comprised of greater than 90% quartz but the surfaces of quartz and other mineral grains are coated with nanometer-size iron (Fe) and aluminum (Al) oxides and/or silicates, which control the adsorption properties of the sediments. Uncontaminated groundwater with added phosphate (620 μ M) was pumped into the uncontaminated zone while samples were collected 0.3 m above the injection point. Concentrations of As(V) increased from below detection (0.005 μ M) to a maximum of 0.07 μ M during breakthrough of phosphate at the sampling port; As(III) concentrations remained below detection. These results are consistent with the hypothesis that naturally occurring As(V) adsorbed to constituents of the coatings on grain surfaces was desorbed by phosphate in the injected groundwater. Also consistent with this hypothesis, vertical profiles of groundwater chemistry measured prior to the tracer test showed that dissolved As(V) concentrations increased along with dissolved phosphate from below detection in the uncontaminated zone to approximately 0.07 and 70 μ M, respectively, in the suboxic zone. Concentrations of As(III) were below detection in both zones. The anoxic zone had approximately 0.07 μ M As(V) but also had As(III) concentrations of 0.07–0.14 μ M, suggesting that release of As bound to sediment grains occurred by desorption by phosphate, reductive dissolution of Fe oxides, and reduction of As(V) to As(III), which adsorbs only weakly to the Fe-oxide-depleted material in the coatings. Results of reductive extractions of the sediments suggest that As associated with the coatings was relatively uniformly distributed at approximately 1 nmol/g of sediment (equivalent to 0.075 ppm As) and comprised 20%-50% of the total As in the sediments, determined from oxidative extractions. Quartz sand aquifers provide high-quality drinking water but can become contaminated when naturally occurring arsenic bound to Fe and Al oxides or silicates on sediment surfaces is released by desorption and dissolution of Fe oxides in response to changing chemical conditions.

Geochemical Transactions↗

USGS2018

Groundwater quality in the Floridan aquifer system, Southeastern United States

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Floridan aquifer system constitutes one of the important aquifer systems being evaluated.

Alabama, Florida, Georgia, South Carolina↗

USGS2018

Groundwater quality in the Mississippi embayment–Texas coastal uplands aquifer system, south-central United States

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Mississippi embayment–Texas coastal uplands aquifer system constitutes one of the important aquifer systems being evaluated.

Mississippi Embayment–Texas Coastal Uplands Aquife↗

USGS2020

Groundwater quality in the High Plains aquifer

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The High Plains aquifer constitutes one of the important aquifers being evaluated.

Colorado, Kansas, Nebraska, New Mexico, Oklahoma, ↗

USGS2020

Groundwater quality in the Biscayne aquifer, Florida

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Biscayne aquifer constitutes one of the important aquifers being evaluated.

Florida↗

USGS2020

Groundwater quality in the Ozark Plateaus aquifer system, central United States

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water (Burow and Belitz, 2014). The Ozark Plateaus aquifer system constitutes one of the important aquifer systems being evaluated.

Arkansas, Kansas, Missouri, Oklahoma↗

USGS2021

Groundwater quality in the Edwards-Trinity aquifer system

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Edwards-Trinity aquifer system constitutes one of the important aquifers being evaluated.

Arkansas, Oklahoma, Texas↗

USGS2021

Groundwater quality in selected Stream Valley aquifers, western United States

Groundwater provides nearly 50 percent of the Nation’s drinking water. To help protect this vital resource, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) Project assesses groundwater quality in aquifers that are important sources of drinking water. The Stream Valley aquifers constitute one of the important aquifer systems being evaluated.

Colorado, Kansas, Missouri, Nebraska, Oklahoma↗