Groundwater Quality Research Active
Groundwater—Our Invisible, Vital Resource
What’s in Our Groundwater?—Current Conditions and Changes
Learn about groundwater quality in Principal Aquifers across the Nation and how it's changed over time
Predicting Groundwater Quality in Unmonitored Areas
See where a contaminant is likely to occur and at what concentration
Is Groundwater Quality Getting Better or Worse?
Use the web-based tool to see how groundwater quality across the Nation has changed over the decades
Every day, millions of gallons of groundwater are pumped to supply drinking water for about 140 million people, almost one-half of the Nation’s population. Learn about the quality and availability of groundwater for drinking, where and why groundwater quality is degraded, and where groundwater quality is changing.
Featured: 3-D Models of As and Mn in the Glacial Aquifer System
New 3-D models from the USGS National Water Quality Program predict where high concentrations of arsenic and manganese likely occur in the glacial aquifer system, groundwater supply for 30 million. Redox conditions and pH are controlling factors.
Groundwater is our invisible, vital resource. The USGS National Water Quality Program (NWQP) is focusing on studies of principal aquifers, regionally extensive aquifers that are critical sources of groundwater used for public supply. The studies have two main thrusts:
- Current conditions and changes through time. These assessments characterize groundwater quality in principal aquifers, comparing concentrations of inorganic constituents, such as arsenic and nitrate, and organic constituents, such as pesticides and volatile organic compounds, to benchmarks established for the protection of human health. Tracking changes in groundwater quality through time and investigating the reasons for these changes is crucial for informing management decisions to protect and sustain our valuable groundwater resources. See how concentrations of metals, nutrients, pesticides, and organic contaminants in groundwater are changing during decadal periods across the Nation, and view real-time fluctuations in groundwater quality.
- Predicting groundwater quality. Statistical models and 3-D characterizations predict where a contaminant is likely to occur in groundwater, at what depth, and at what concentration. These forecasts anticipate water quality in areas where groundwater has not been sampled.
From 1991 to 2010, about 6,600 wells were sampled by the NWQP to document where contaminants occur and to develop an understanding of the natural and human factors that affect the occurrence of contaminants in the Nation’s groundwater. Learn about groundwater quality in the Nation’s principal aquifers, 1991–2010.
Explore USGS science on topics related to groundwater quality:
National Water Quality Assessment (NAWQA) Project
Contaminants in groundwater
Arsenic and Drinking Water
Chloride, Salinity, and Dissolved Solids
Emerging Contaminants
Metals and Other Trace Elements
Nutrients and Eutrophication
Pesticides and Water Quality
Radionuclides
Volatile organic compounds (VOCs)
Hydraulic Fracturing
Drinking and source-water quality
Corrosivity
Domestic (private) supply wells
Public-supply wells
Drinking-water taste and odor
Water-Quality Benchmarks for Contaminants
Processes affecting groundwater quality
Groundwater Age
Oxidation/Reduction (Redox)
How do we do it? Access USGS publications and manuals on National Water-Quality Project sampling methods.
Looking for information on surface-water quality as well? Explore these links:
Surface-Water Quality and Ecology
Groundwater/Surface-Water Interaction
Radionuclides
Groundwater Quality in Principal Aquifers of the Nation, 1991–2010
Rapid Fluctuations in Groundwater Quality
Predicting Groundwater Quality in Unmonitored Areas
Factors Affecting Vulnerability of Public-Supply Wells to Contamination
Volatile Organic Compounds (VOCs)
Oxidation/Reduction (Redox)
Water-Quality Trends
Access our most recent groundwater-quality data.
Location and population served by domestic wells in the conterminous U.S.: 1990
Depth to 50 percent probability of oxic conditions, Chesapeake Bay Watershed
Ascii grids of predicted pH in depth zones used by domestic and public drinking water supply depths, Central Valley, California
Groundwater Quality Data from the National Water Quality Assessment Project, May 2012 through December 2013
Langelier Saturation Indices Computed for U.S. Groundwater, 1991-2015; Water Well Data and Characteristic Values for States
Below, you’ll find the latest in peer-reviewed journal articles and USGS reports on groundwater water-quality issues.
Tritium as an indicator of modern, mixed, and premodern groundwater age
Groundwater quality in the Biscayne aquifer, Florida
Groundwater quality in the Ozark Plateaus aquifer system, central United States
Time scales of arsenic variability and the role of high-frequency monitoring at three water-supply wells in New Hampshire, USA
Using age tracers and decadal sampling to discern trends in nitrate, arsenic and uranium in groundwater beneath irrigated cropland
Guidelines and standard procedures for high-frequency groundwater-quality monitoring stations—Design, operation, and record computation
Arsenic variability and groundwater age in three water supply wells in southeast New Hampshire
Drinking water quality in the glacial aquifer system, northern USA
Timescales of water-quality change in a karst aquifer, south-central Texas
Hydrocarbons in upland groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
Estimating domestic well locations and populations served in the contiguous U.S. for years 2000 and 2010
Assessing the lead solubility potential of untreated groundwater of the United States
Hormones and pharmaceuticals in groundwater used as a source of drinking water across the United States
Contaminants present in many parts of the Glacial aquifer system
Are you one of 30 million Americans whose drinking-water supply relies on groundwater from the glacial aquifer system? A new USGS study assesses the quality of untreated groundwater from this critical water resource, which underlies parts of 25 northern U.S. states.
- Overview
Every day, millions of gallons of groundwater are pumped to supply drinking water for about 140 million people, almost one-half of the Nation’s population. Learn about the quality and availability of groundwater for drinking, where and why groundwater quality is degraded, and where groundwater quality is changing.
Featured: 3-D Models of As and Mn in the Glacial Aquifer SystemNew 3-D models from the USGS National Water Quality Program predict where high concentrations of arsenic and manganese likely occur in the glacial aquifer system, groundwater supply for 30 million. Redox conditions and pH are controlling factors.
Groundwater is our invisible, vital resource. The USGS National Water Quality Program (NWQP) is focusing on studies of principal aquifers, regionally extensive aquifers that are critical sources of groundwater used for public supply. The studies have two main thrusts:
- Current conditions and changes through time. These assessments characterize groundwater quality in principal aquifers, comparing concentrations of inorganic constituents, such as arsenic and nitrate, and organic constituents, such as pesticides and volatile organic compounds, to benchmarks established for the protection of human health. Tracking changes in groundwater quality through time and investigating the reasons for these changes is crucial for informing management decisions to protect and sustain our valuable groundwater resources. See how concentrations of metals, nutrients, pesticides, and organic contaminants in groundwater are changing during decadal periods across the Nation, and view real-time fluctuations in groundwater quality.
- Predicting groundwater quality. Statistical models and 3-D characterizations predict where a contaminant is likely to occur in groundwater, at what depth, and at what concentration. These forecasts anticipate water quality in areas where groundwater has not been sampled.
From 1991 to 2010, about 6,600 wells were sampled by the NWQP to document where contaminants occur and to develop an understanding of the natural and human factors that affect the occurrence of contaminants in the Nation’s groundwater. Learn about groundwater quality in the Nation’s principal aquifers, 1991–2010.
Explore USGS science on topics related to groundwater quality:
National Water Quality Assessment (NAWQA) Project
Contaminants in groundwater
Arsenic and Drinking Water
Chloride, Salinity, and Dissolved Solids
Emerging Contaminants
Metals and Other Trace Elements
Nutrients and Eutrophication
Pesticides and Water Quality
Radionuclides
Volatile organic compounds (VOCs)
Hydraulic FracturingDrinking and source-water quality
Corrosivity
Domestic (private) supply wells
Public-supply wells
Drinking-water taste and odor
Water-Quality Benchmarks for ContaminantsProcesses affecting groundwater quality
Groundwater Age
Oxidation/Reduction (Redox)How do we do it? Access USGS publications and manuals on National Water-Quality Project sampling methods.
Looking for information on surface-water quality as well? Explore these links:
Surface-Water Quality and Ecology
Groundwater/Surface-Water Interaction
- Science
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Radionuclides
Many people might be surprised to learn that drinking-water sources, especially groundwater, can contain radioactive elements (radionuclides). Radionuclides in water can be a concern for human health because several are toxic or carcinogenic. Other radionuclides are useful tools for determining the age of groundwater in an aquifer or of sediment deposited at the bottom of a water body.Groundwater Quality in Principal Aquifers of the Nation, 1991–2010
What’s in your groundwater? Learn about groundwater quality in the Principal Aquifers of nine regions across the United States in informative circulars filled with figures, photos, and water-quality information.Rapid Fluctuations in Groundwater Quality
We think of groundwater as moving slowly, and groundwater quality as changing slowly—over decades or even centuries. But in some parts of some aquifers, groundwater quality can fluctuate rapidly, sometimes over just a few hours. Are such changes part of a long-term trend, or just part of a short-term cycle? And what does that mean for suitability for drinking?Predicting Groundwater Quality in Unmonitored Areas
Groundwater provides nearly one-half of the Nation’s drinking water, and sustains the steady flow of streams and rivers and the ecological systems that depend on that flow. Unless we drill a well, how can we know the quality of the groundwater below? Learn about how the USGS is using sophisticated techniques to predict groundwater quality and view national maps of groundwater quality.Factors Affecting Vulnerability of Public-Supply Wells to Contamination
More than 100 million people in the United States—about 35 percent of the population—receive their drinking water from public-supply wells. These systems can be vulnerable to contamination from naturally occurring constituents, such as radon, uranium and arsenic, and from commonly used manmade chemicals, such as fertilizers, pesticides, solvents, and gasoline hydrocarbons. Learn about the...Volatile Organic Compounds (VOCs)
Volatile organic compounds (VOCs) are chemicals that both vaporize into air and dissolve in water. VOCs are pervasive in daily life, because they’re used in industry, agriculture, transportation, and day-to-day activities around the home. Once released into groundwater, many VOCs are persistent and can migrate to drinking-water supply wells.Oxidation/Reduction (Redox)
The redox state of groundwater—whether the groundwater is oxic (oxidized) or anoxic (reduced)—has profound implications for groundwater quality. Knowing the redox conditions of groundwater can help determine whether it contains elevated levels of many contaminants, including arsenic, nitrate, and even some manmade contaminants.Water-Quality Trends
Is water quality getting better or worse? Answering this deceptively simple question has been a fundamental objective of the USGS National Water-Quality Assessment Project’s research. Learn about trends in contaminants in the nation’s streams and rivers, trends in contaminants that collect in the bed sediment of streams and lakes, and changes in the quality of the nation’s groundwater. - Data
Access our most recent groundwater-quality data.
Filter Total Items: 17Location and population served by domestic wells in the conterminous U.S.: 1990
In this dataset we present two maps that estimate the location and population served by domestic wells in the contiguous United States. The first methodology, called the Block Group Method or BGM, builds upon the original block-group data from the 1990 census (the last time the U.S. Census queried the population regarding their source of water) by incorporating higher resolution census block data.Depth to 50 percent probability of oxic conditions, Chesapeake Bay Watershed
Defining the oxic-suboxic interface is often critical for determining pathways for nitrate transport in groundwater and to streams at the local scale. Defining this interface on a regional scale is complicated by the spatial variability of reaction rates. The probability of oxic groundwater in the Chesapeake Bay watershed was predicted by relating dissolved O2 concentrations in groundwater samplesAscii grids of predicted pH in depth zones used by domestic and public drinking water supply depths, Central Valley, California
The ascii grids associated with this data release are predicted distributions of continuous pH at the drinking water depth zones in the groundwater of Central Valley, California. The two prediction grids produced in this work represent predicted pH at the domestic supply and public supply drinking water depths, respectively and are bound by the alluvial boundary that defines the Central Valley. AGroundwater Quality Data from the National Water Quality Assessment Project, May 2012 through December 2013
Groundwater-quality data were collected from 748 wells as part of the National Water-Quality Assessment Project of the U.S. Geological Survey National Water-Quality Program from May 2012 through December 2013. The data were collected from four types of well networks: principal aquifer study networks, which assess the quality of groundwater used for public water supply; land-use study networks, whiLangelier Saturation Indices Computed for U.S. Groundwater, 1991-2015; Water Well Data and Characteristic Values for States
The occurrence of metals, such as lead and copper, in household drinking supplies can often be a result of the corrosion of pipes and joints in water distribution systems. One measure of the potential for water to cause corrosion is the Langelier Saturation Index (LSI) (Langelier, 1936). The LSI is a measure of the potential for water to deposit a mineral layer (scale) within a water distribution - Multimedia
- Publications
Below, you’ll find the latest in peer-reviewed journal articles and USGS reports on groundwater water-quality issues.
Tritium as an indicator of modern, mixed, and premodern groundwater age
Categorical classification of groundwater age is often used for the assessment and understanding of groundwater resources. This report presents a tritium-based age classification system for the conterminous United States based on tritium (3H) thresholds that vary in space and time: modern (recharged in 1953 or later), if the measured value is larger than an upper threshold; premodern (recharged prAuthorsBruce D. Lindsey, Bryant C. Jurgens, Kenneth BelitzFilter Total Items: 45Groundwater 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.AuthorsJames A. KingsburyGroundwater 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 evaluatAuthorsJames A. KingsburyTime scales of arsenic variability and the role of high-frequency monitoring at three water-supply wells in New Hampshire, USA
Groundwater geochemistry, redox process classification, high-frequency physicochemical and hydrologic measurements, and climate data were analyzed to identify controls on arsenic (As) concentration changes. Groundwater was monitored in two public-supply wells (one glacial aquifer and one bedrock aquifer), and one bedrock-aquifer domestic well in New Hampshire, USA, from 2014 to 2018 to identify tiAuthorsJames R. Degnan, Joseph P. Levitt, Melinda Erickson, Bryant C. Jurgens, Bruce D. Lindsey, Joseph D. AyotteUsing age tracers and decadal sampling to discern trends in nitrate, arsenic and uranium in groundwater beneath irrigated cropland
Repeat sampling and age tracers were used to examine trends in nitrate, arsenic and uranium concentrations in groundwater beneath irrigated cropland. Much higher nitrate concentrations in shallow modern groundwater were observed at both the Columbia Plateau and High Plains sites (median values of 10.2 and 15.4 mg/L as N, respectively) than in groundwater that recharged prior to the onset of intensAuthorsAnthony J. Tesoriero, Karen R. Burow, Lonna Frans, Jonathan V. Haynes, Christopher M. Hobza, Bruce D. Lindsey, John E. SolderGuidelines and standard procedures for high-frequency groundwater-quality monitoring stations—Design, operation, and record computation
High-frequency water-quality monitoring stations measure and transmit data, often in near real-time, from a wide range of aquatic environments to assess the quality of the Nation’s water resources. Common instrumentation for high-frequency water-quality data collection uses a multi-parameter sonde, which typically has sensors that measure and record water temperature, specific conductance, pH, andAuthorsTimothy M. Mathany, John Franco Saraceno, Justin T. KulongoskiArsenic variability and groundwater age in three water supply wells in southeast New Hampshire
Three wells in New Hampshire were sampled bimonthly over three years to evaluate the temporal variability of arsenic concentrations and groundwater age. All samples had measurable concentrations of arsenic throughout the entire sampling period and concentrations in individual wells varied, on average, by more than 7 µg/L. High arsenic concentrations (>10 µg/L) were measured in bedrock wells KFW-87AuthorsJoseph Levitt, James Degnan, Sarah Flanagan, Bryant JurgensDrinking water quality in the glacial aquifer system, northern USA
Groundwater supplies 50% of drinking water worldwide, but compromised water quality from anthropogenic and geogenic contaminants can limit usage of groundwater as a drinking water source. Groundwater quality in the glacial aquifer system, USA (GLAC), is presented in the context of a hydrogeologic framework that divides the study area into 17 hydrogeologic terranes. Results are reported at aquifer-AuthorsMelinda L. Erickson, Richard M. Yager, Leon J. Kauffman, John T. WilsonTimescales of water-quality change in a karst aquifer, south-central Texas
Understanding the drivers and timescales over which groundwater quality changes informs groundwater management, use, and protection. To better understand timescales of water-quality change over short (daily to monthly) and long (seasonal to decadal) timescales, the U.S. Geological Survey’s National Water-Quality Assessment (NAWQA) Enhanced Trends Network (ETN) program instrumented and sampled threAuthorsMaryLynn Musgrove, John E. Solder, Stephen P. Opsahl, Jennifer T. WilsonHydrocarbons in upland groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
Water samples from 50 domestic wells located <1 km (proximal) and >1 km (distal) from shale-gas wells in upland areas of the Marcellus Shale region were analyzed for chemical, isotopic, and groundwater-age tracers. Uplands were targeted because natural mixing with brine and hydrocarbons from deep formations is less common in those areas compared to valleys. CH4-isotope, predrill CH4-concentration,AuthorsPeter B. McMahon, Bruce D. Lindsey, Matthew D. Conlon, Andrew G. Hunt, Kenneth Belitz, Bryant Jurgens, Brian A. VarelaByWater Resources Mission Area, Energy Resources Program, National Water Quality Program, California Water Science Center, Central Energy Resources Science Center, Colorado Water Science Center, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center, New England Water Science Center, Pennsylvania Water Science CenterEstimating domestic well locations and populations served in the contiguous U.S. for years 2000 and 2010
Domestic wells provide drinking water supply for approximately 40 million people in the United States. Knowing the location of these wells, and the populations they serve, is important for identifying heavily used aquifers, locations susceptible to contamination, and populations potentially impacted by poor-quality groundwater. The 1990 census was the last nationally consistent survey of a home’sAuthorsTyler D. Johnson, Kenneth Belitz, Melissa LombardAssessing the lead solubility potential of untreated groundwater of the United States
In the U.S., about 44 million people rely on self-supplied groundwater for drinking water. Because most self-supplied homeowners do not treat their water to control corrosion, drinking water can be susceptible to lead (Pb) contamination from metal plumbing. To assess the types and locations of susceptible groundwater, a geochemical reaction model that included pure Pb minerals and solid solutionsAuthorsBryant Jurgens, David L. Parkhurst, Kenneth BelitzHormones and pharmaceuticals in groundwater used as a source of drinking water across the United States
This is the first large-scale, systematic assessment of hormone and pharmaceutical occurrence in groundwater used for drinking across the United States. Samples from 1091 sites in Principal Aquifers representing 60% of the volume pumped for drinking-water supply had final data for 21 hormones and 103 pharmaceuticals. At least one compound was detected at 5.9% of 844 sites representing the resourceAuthorsLaura M. Bexfield, Patricia Toccalino, Kenneth Belitz, William T. Foreman, Edward Furlong - Web Tools
- News
Contaminants present in many parts of the Glacial aquifer system
Are you one of 30 million Americans whose drinking-water supply relies on groundwater from the glacial aquifer system? A new USGS study assesses the quality of untreated groundwater from this critical water resource, which underlies parts of 25 northern U.S. states.
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