Public Supply Wells Active
What’s in the Groundwater Used for Public Supply?
USGS studies the quality of this key source of drinking water
Are you among the more than 100 million people in the U.S. who relies on a public-supply well for your drinking water? Although the quality of finished drinking water from public water systems is regulated by the EPA, long-term protection and management of the raw groundwater tapped by public-supply wells requires an understanding of the occurrence of contaminants in this invisible, vital resource.
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.
Updated Information on Groundwater Quality in Public-Supply Wells
Three new USGS fact sheets update information on groundwater quality in the nation's most heavily used aquifers. Fact sheets are now available for the Edwards-Trinity aquifer system, the Stream Valley aquifers, and the Colorado Plateau aquifers.
The USGS National Water Quality Program investigates the quality of water pumped from public-supply wells across the United States. These wells are the source of drinking water and water for other household needs for more than one-third of the U.S. population. There are about 140,000 public water systems that use groundwater as their source.
Although the quality of finished drinking water (after treatment and before distribution) from these public water systems is regulated by the EPA under the Safe Drinking Water Act (SDWA), long-term protection and management of groundwater, a vital source of drinking water, requires an understanding of the occurrence of contaminants in untreated source water. Sources of drinking water are potentially vulnerable to a wide range of manmade and naturally occurring contaminants, including many that are not regulated in drinking water under the SDWA.
Water Quality of Public Supply Wells
In a study of 932 U.S. public-supply wells, water pumped from about one in five source-water samples (that is, before treatment) contained one or more contaminants at a concentration greater than a human-health benchmark for drinking water. Supporting information and summary data for the study can be found here.
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Naturally occurring trace elements and radionuclides accounted for about three-quarters of contaminant concentrations greater than human-health benchmarks in source-water samples.
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Manmade organic compounds, such as pesticides and solvents, were detected in nearly two-thirds of samples, but typically at a concentration that did not exceed a human-health benchmark.
-
Many organic (manmade) contaminants detected in source water also were detected in treated water at similar concentrations.
-
Human-health benchmarks are not yet available for many manmade contaminants, including some that were frequently detected in source water.
-
Contaminants found in groundwater used as a source of public supply usually co-occurred with other contaminants as mixtures, rather than alone, which is a potential concern because the total toxicity of a mixture can be greater than that of any single contaminant.
Read informative fact sheets about current water-quality conditions in public supply wells that pump water from Principal Aquifers across the country. More detailed information on the quality of water from public-supply wells is provided in USGS publications that summarize the quality of water in Principal Aquifers in nine regions of the United States.
What causes public-supply wells to be vulnerable to contamination?
Public-supply-well vulnerability to contamination starts with groundwater vulnerability to contamination. The vulnerability of the water from public-supply wells to contamination depends on contaminant input in the area that contributes water to a well, the mobility and persistence of a contaminant once released to the groundwater, and the ease of groundwater and contaminant movement from the point of recharge to the well. Wells within a single aquifer, however, may not be equally vulnerable to contaminants in the aquifer because individual wells produce unique mixtures of the groundwater from different depths in the aquifer and with different ages (time since recharge).
A study done from 2001 to 2011 sheds light on factors that affect the vulnerability of water from public-supply wells to contamination. The study also identified measures that can be used to determine which factor (or factors) plays a dominant role at an individual public-supply well. These measures are particularly useful for indicating which contaminants in an aquifer might reach an individual public-supply well and when, how, and at what concentration they might arrive. Case-study examples show how such information can be used to improve water quality.
Interested in the water quality of domestic (private) wells?
Find information on USGS studies of domestic water-supply wells used for drinking water by thousands of people in rural areas.
Explore these topics related to groundwater quality:
The links below are a gateway to web pages that describe USGS science on groundwater-quality topics.
Follow the links below to access data on water quality of public-supply wells and tools for exploring groundwater quality.
Learn about USGS research on the water quality of public-supply wells and other groundwater quality issues at the publications listed below.
The quality of our Nation’s waters: Quality of water from public-supply wells in the United States, 1993–2007: Overview of major findings
Time scales of arsenic variability and the role of high-frequency monitoring at three water-supply wells in New Hampshire, USA
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
Radium mobility and the age of groundwater in public-drinking-water supplies from the Cambrian-Ordovician aquifer system, north-central USA
Domestic well locations and populations served in the contiguous U.S.: 1990
The quality of our nation's waters: water quality in the Principal Aquifers of the Piedmont, Blue Ridge, and Valley and Ridge regions, eastern United States, 1993-2009
The quality of our Nation's waters: water quality in the glacial aquifer system, northern United States, 1993-2009
The quality of our Nation's waters: water quality in the Upper Floridan aquifer and overlying surficial aquifers, southeastern United States, 1993-2010
The quality of our Nation's waters: water quality in the Northern Atlantic Coastal Plain surficial aquifer system, Delaware, Maryland, New Jersey, New York, North Carolina, and Virginia, 1988-2009
The quality of our Nation's waters: groundwater quality in the Columbia Plateau and Snake River Plain basin-fill and basaltic-rock aquifers and the Hawaiian volcanic-rock aquifers, Washington, Idaho, and Hawaii, 1993-2005
The quality of our Nation's waters: Water quality in basin-fill aquifers of the southwestern United States: Arizona, California, Colorado, Nevada, New Mexico, and Utah, 1993-2009
Modeling nitrate at domestic and public-supply well depths in the Central Valley, California
Follow the links below to access data on water quality of public-supply wells and tools for exploring groundwater quality.
Groundwater Quality: Decadal Change
Almost one-half of the U.S. population rely on groundwater for their water supply, and demand for groundwater for public supply, irrigation, and agriculture continues to increase. This mapper shows how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater are changing during decadal periods across the Nation.
- Overview
Are you among the more than 100 million people in the U.S. who relies on a public-supply well for your drinking water? Although the quality of finished drinking water from public water systems is regulated by the EPA, long-term protection and management of the raw groundwater tapped by public-supply wells requires an understanding of the occurrence of contaminants in this invisible, vital resource.
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.
Updated Information on Groundwater Quality in Public-Supply WellsThree new USGS fact sheets update information on groundwater quality in the nation's most heavily used aquifers. Fact sheets are now available for the Edwards-Trinity aquifer system, the Stream Valley aquifers, and the Colorado Plateau aquifers.
The USGS National Water Quality Program investigates the quality of water pumped from public-supply wells across the United States. These wells are the source of drinking water and water for other household needs for more than one-third of the U.S. population. There are about 140,000 public water systems that use groundwater as their source.
Although the quality of finished drinking water (after treatment and before distribution) from these public water systems is regulated by the EPA under the Safe Drinking Water Act (SDWA), long-term protection and management of groundwater, a vital source of drinking water, requires an understanding of the occurrence of contaminants in untreated source water. Sources of drinking water are potentially vulnerable to a wide range of manmade and naturally occurring contaminants, including many that are not regulated in drinking water under the SDWA.
Water Quality of Public Supply Wells
In a study of 932 U.S. public-supply wells, water pumped from about one in five source-water samples (that is, before treatment) contained one or more contaminants at a concentration greater than a human-health benchmark for drinking water. Supporting information and summary data for the study can be found here.
-
Naturally occurring trace elements and radionuclides accounted for about three-quarters of contaminant concentrations greater than human-health benchmarks in source-water samples.
-
Manmade organic compounds, such as pesticides and solvents, were detected in nearly two-thirds of samples, but typically at a concentration that did not exceed a human-health benchmark.
-
Many organic (manmade) contaminants detected in source water also were detected in treated water at similar concentrations.
-
Human-health benchmarks are not yet available for many manmade contaminants, including some that were frequently detected in source water.
-
Contaminants found in groundwater used as a source of public supply usually co-occurred with other contaminants as mixtures, rather than alone, which is a potential concern because the total toxicity of a mixture can be greater than that of any single contaminant.
Read informative fact sheets about current water-quality conditions in public supply wells that pump water from Principal Aquifers across the country. More detailed information on the quality of water from public-supply wells is provided in USGS publications that summarize the quality of water in Principal Aquifers in nine regions of the United States.
What causes public-supply wells to be vulnerable to contamination?
Public-supply-well vulnerability to contamination starts with groundwater vulnerability to contamination. The vulnerability of the water from public-supply wells to contamination depends on contaminant input in the area that contributes water to a well, the mobility and persistence of a contaminant once released to the groundwater, and the ease of groundwater and contaminant movement from the point of recharge to the well. Wells within a single aquifer, however, may not be equally vulnerable to contaminants in the aquifer because individual wells produce unique mixtures of the groundwater from different depths in the aquifer and with different ages (time since recharge).
A study done from 2001 to 2011 sheds light on factors that affect the vulnerability of water from public-supply wells to contamination. The study also identified measures that can be used to determine which factor (or factors) plays a dominant role at an individual public-supply well. These measures are particularly useful for indicating which contaminants in an aquifer might reach an individual public-supply well and when, how, and at what concentration they might arrive. Case-study examples show how such information can be used to improve water quality.
Interested in the water quality of domestic (private) wells?
Find information on USGS studies of domestic water-supply wells used for drinking water by thousands of people in rural areas.
Explore these topics related to groundwater quality:
-
- Science
The links below are a gateway to web pages that describe USGS science on groundwater-quality topics.
- Data
Follow the links below to access data on water quality of public-supply wells and tools for exploring groundwater quality.
- Publications
Learn about USGS research on the water quality of public-supply wells and other groundwater quality issues at the publications listed below.
The quality of our Nation’s waters: Quality of water from public-supply wells in the United States, 1993–2007: Overview of major findings
Summary of Major Findings and Implications About 105 million people in the United States-more than one-third of the Nation's population-receive their drinking water from about 140,000 public water systems that use groundwater as their source. Although the quality of finished drinking water (after treatment and before distribution) from these public water systems is regulated by the U.S. EnvironmeAuthorsPatricia L. Toccalino, Jessica A. HoppleFilter Total Items: 30Time 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. AyotteAssessing 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 FurlongRadium mobility and the age of groundwater in public-drinking-water supplies from the Cambrian-Ordovician aquifer system, north-central USA
High radium (Ra) concentrations in potable portions of the Cambrian-Ordovician (C-O) aquifer system were investigated using water-quality data and environmental tracers (3H, 3Hetrit, SF6, 14C and 4Herad) of groundwater age from 80 public-supply wells (PSWs). Groundwater ages were estimated by calibration of tracers to lumped parameter models and ranged from modern (<50 yr) in upgradient, regionallAuthorsPaul E. Stackelberg, Zoltan Szabo, Bryant C. JurgensDomestic well locations and populations served in the contiguous U.S.: 1990
We estimate the location and population served by domestic wells in the contiguous United States in two ways: (1) the “Block Group Method” or BGM, uses data from the 1990 census, and (2) the “Road-Enhanced Method” or REM, refines the locations by using a buffer expansion and shrinkage technique along roadways to define areas where domestic wells exist. The fundamental assumption is that houses (anAuthorsTyler Johnson, Kenneth BelitzThe quality of our nation's waters: water quality in the Principal Aquifers of the Piedmont, Blue Ridge, and Valley and Ridge regions, eastern United States, 1993-2009
The aquifers of the Piedmont, Blue Ridge, and Valley and Ridge regions underlie an area with a population of more than 40 million people in 10 states. The suburban and rural population is large, growing rapidly, and increasingly dependent on groundwater as a source of supply, with more than 550 million gallons per day withdrawn from domestic wells for household use. Water from some of these aquifeAuthorsBruce D. Lindsey, Tammy M. Zimmerman, Melinda J. Chapman, Charles A. Cravotta, Zoltan SzaboThe quality of our Nation's waters: water quality in the glacial aquifer system, northern United States, 1993-2009
The glacial aquifer system underlies much of the northern United States. About one-sixth (41 million people) of the United States population relies on the glacial aquifer system for drinking water. The primary importance of the glacial aquifer system is as a source of water for public supply to the population centers in the region, but the aquifer system also provides drinking water for domestic uAuthorsKelly L. Warner, Joseph D. AyotteThe quality of our Nation's waters: water quality in the Upper Floridan aquifer and overlying surficial aquifers, southeastern United States, 1993-2010
About 10 million people rely on groundwater from the Upper Floridan and surficial aquifers for drinking water. The Upper Floridan aquifer also is of primary importance to the region as a source of water for irrigation and as a source of crystal clear water that discharges to springs and streams providing recreational and tourist destinations and unique aquatic habitats. The reliance of the regionAuthorsMarian P. Berndt, Brian G. Katz, James A. Kingsbury, Christy A. CrandallThe quality of our Nation's waters: water quality in the Northern Atlantic Coastal Plain surficial aquifer system, Delaware, Maryland, New Jersey, New York, North Carolina, and Virginia, 1988-2009
The surficial aquifer system of the Northern Atlantic Coastal Plain is made up of unconfined aquifers that underlie most of the area. This aquifer system is a critical renewable source of drinking water and is the source of most flow to streams and of recharge to underlying confined aquifers. Millions of people rely on the surficial aquifer system for public and domestic water supply, in particulaAuthorsJudith M. Denver, Scott W. Ator, Jeffrey M. Fischer, Douglas C. Harned, Christopher Schubert, Zoltan SzaboThe quality of our Nation's waters: groundwater quality in the Columbia Plateau and Snake River Plain basin-fill and basaltic-rock aquifers and the Hawaiian volcanic-rock aquifers, Washington, Idaho, and Hawaii, 1993-2005
The Columbia Plateau, Snake River Plain, and Hawaii are large volcanic areas in the western United States and mid-Pacific ocean that contain extensive regional aquifers of a hard, gray, volcanic rock called basalt. Residents of the Columbia Plateau, the Snake River Plain, and the island of Oahu depend on groundwater as their primary source of drinking water. Although the depth to the water table cAuthorsMichael G. Rupert, Charles D. Hunt, Kenneth D. Skinner, Lonna M. Frans, Barbara MahlerThe quality of our Nation's waters: Water quality in basin-fill aquifers of the southwestern United States: Arizona, California, Colorado, Nevada, New Mexico, and Utah, 1993-2009
The Southwest Principal Aquifers consist of many basin-fill aquifers in California, Nevada, Utah, Arizona, New Mexico, and Colorado. Demands for irrigation and drinking water have substantially increased groundwater withdrawals and irrigation return flow to some of these aquifers. These changes have increased the movement of contaminants from geologic and human sources to depths used to supply driAuthorsSusan A. Thiros, Angela P. Paul, Laura M. Bexfield, David W. AnningModeling nitrate at domestic and public-supply well depths in the Central Valley, California
Aquifer vulnerability models were developed to map groundwater nitrate concentration at domestic and public-supply well depths in the Central Valley, California. We compared three modeling methods for ability to predict nitrate concentration >4 mg/L: logistic regression (LR), random forest classification (RFC), and random forest regression (RFR). All three models indicated processes of nitrogen feAuthorsBernard T. Nolan, JoAnn M. Gronberg, Claudia C. Faunt, Sandra M. Eberts, Ken Belitz - Web Tools
Follow the links below to access data on water quality of public-supply wells and tools for exploring groundwater quality.
Groundwater Quality: Decadal Change
Almost one-half of the U.S. population rely on groundwater for their water supply, and demand for groundwater for public supply, irrigation, and agriculture continues to increase. This mapper shows how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater are changing during decadal periods across the Nation.