Factors Affecting Vulnerability of Public-Supply Wells to Contamination Completed
Insights into Water Quality at Public-Supply Wells
Understanding observed water quality and anticipating future water quality
Groundwater Age Mixtures and Contaminant Trends Tool
Explore the effects of groundwater age mixtures on contaminant trends
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 Transport of Anthropogenic and Naturally Occurring Contaminants (TANC) study.
Public-supply-well vulnerability to contamination starts with groundwater vulnerability to contamination. Even wells within a single aquifer, however, may not be equally vulnerable to contamination because individual wells produce unique mixtures of the groundwater from different parts of the aquifer.
A study done from 2001 to 2011 (Transport of Anthropogenic Contaminants, or TANC study) 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. Case-study examples show how such information can be used to improve water quality.
In general, 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. The following 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:
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Sources of recharge—Information on the sources of recharge for a well provides insight into contaminants that might enter the aquifer with the recharge water and potentially reach the well.
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Geochemical conditions—Information on the geochemical conditions encountered by groundwater traveling to a well provides insight into contaminants that might persist in the water all the way to the well. Use the Redox Framework Tool to determine the redox conditions associated with water from a public-supply well.
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Groundwater-age mixtures—Information on the ages of the different waters that mix in a well provides insight into the time lag between contaminant input at the water table and contaminant arrival at the well. It also provides insight into the potential for in-well dilution of contaminated water by unaffected groundwater of a different age that simultaneously enters the well. Use the web-based Groundwater Age Mixtures and Contaminant Trends Tool to explore the effects of basic aquifer properties and well configurations on groundwater age mixtures in groundwater discharge and on contaminant trends from different nonpoint-source contaminant input scenarios.
Preferential flow pathways—pathways that provide little resistance to flow—can influence how all other factors affect public-supply-well vulnerability to contamination. For example, preferential flow pathways can influence whether a contaminant source is physically linked to a well, whether contaminant concentrations are substantially altered before contaminated groundwater reaches a well, and whether contaminated groundwater can arrive at a well within a timeframe of concern to the well owner. Methods for recognizing the influence of preferential flow pathways on the quality of water from a public-supply well are presented in this circular and can provide opportunities to prevent or mitigate the deterioration of a water supply.
Knowing what water-quality variables to measure, what spatial and temporal scales on which to measure them, and how to interpret the resulting data makes it possible for samples from public-supply wells to provide a broad window into a well’s past and present water quality—and possibly future water quality. Such insight can enable resource managers to prioritize actions for sustaining a high-quality groundwater source of drinking water.
Learn more about the USGS National Water Quality Assessment Project and research on the Nation’s groundwater and surface-water quality.
Look down the list below for additional web resources describing USGS research on groundwater quality.
Public Supply Wells
Access publication on groundwater vulnerability to contamination below. For more publications on groundwater quality, search the USGS Publications Warehouse. Look here for help using the Pubs Warehouse.
The quality of our Nation's waters: factors affecting public-supply-well vulnerability to contamination: understanding observed water quality and anticipating future water quality
Statistical evaluation of variables affecting occurrence of hydrocarbons in aquifers used for public supply, California
Modeling the effects of naturally occurring organic carbon on chlorinated ethene transport to a public supply well
Hydrothermal contamination of public supply wells in Napa and Sonoma Valleys, California
Geogenic sources of benzene in aquifers used for public supply, California
TracerLPM (Version 1): An Excel® workbook for interpreting groundwater age distributions from environmental tracer data
Comparison of particle-tracking and lumped-parameter age-distribution models for evaluating vulnerability of production wells to contamination
Chemical mixtures in untreated water from public-supply wells in the U.S. — Occurrence, composition, and potential toxicity
Assessing the vulnerability of public-supply wells to contamination: Rio Grande aquifer system in Albuquerque, New Mexico
Assessing the vulnerability of public-supply wells to contamination—Edwards aquifer near San Antonio, Texas
Modeling the potential impact of seasonal and inactive multi-aquifer wells on contaminant movement to public water-supply wells
Occurrence and concentrations of pharmaceutical compounds in groundwater used for public drinking-water supply in California
Effects of human-induced alteration of groundwater flow on concentrations of naturally-occurring trace elements at water-supply wells
- Overview
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 Transport of Anthropogenic and Naturally Occurring Contaminants (TANC) study.
Public-supply-well vulnerability to contamination starts with groundwater vulnerability to contamination. Even wells within a single aquifer, however, may not be equally vulnerable to contamination because individual wells produce unique mixtures of the groundwater from different parts of the aquifer.
A study done from 2001 to 2011 (Transport of Anthropogenic Contaminants, or TANC study) 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. Case-study examples show how such information can be used to improve water quality.
In general, 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. The following 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:
-
Sources of recharge—Information on the sources of recharge for a well provides insight into contaminants that might enter the aquifer with the recharge water and potentially reach the well.
-
Geochemical conditions—Information on the geochemical conditions encountered by groundwater traveling to a well provides insight into contaminants that might persist in the water all the way to the well. Use the Redox Framework Tool to determine the redox conditions associated with water from a public-supply well.
-
Groundwater-age mixtures—Information on the ages of the different waters that mix in a well provides insight into the time lag between contaminant input at the water table and contaminant arrival at the well. It also provides insight into the potential for in-well dilution of contaminated water by unaffected groundwater of a different age that simultaneously enters the well. Use the web-based Groundwater Age Mixtures and Contaminant Trends Tool to explore the effects of basic aquifer properties and well configurations on groundwater age mixtures in groundwater discharge and on contaminant trends from different nonpoint-source contaminant input scenarios.
Preferential flow pathways—pathways that provide little resistance to flow—can influence how all other factors affect public-supply-well vulnerability to contamination. For example, preferential flow pathways can influence whether a contaminant source is physically linked to a well, whether contaminant concentrations are substantially altered before contaminated groundwater reaches a well, and whether contaminated groundwater can arrive at a well within a timeframe of concern to the well owner. Methods for recognizing the influence of preferential flow pathways on the quality of water from a public-supply well are presented in this circular and can provide opportunities to prevent or mitigate the deterioration of a water supply.
Knowing what water-quality variables to measure, what spatial and temporal scales on which to measure them, and how to interpret the resulting data makes it possible for samples from public-supply wells to provide a broad window into a well’s past and present water quality—and possibly future water quality. Such insight can enable resource managers to prioritize actions for sustaining a high-quality groundwater source of drinking water.
Learn more about the USGS National Water Quality Assessment Project and research on the Nation’s groundwater and surface-water quality.
-
- Science
Look down the list below for additional web resources describing USGS research on groundwater quality.
Public Supply Wells
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... - Publications
Access publication on groundwater vulnerability to contamination below. For more publications on groundwater quality, search the USGS Publications Warehouse. Look here for help using the Pubs Warehouse.
The quality of our Nation's waters: factors affecting public-supply-well vulnerability to contamination: understanding observed water quality and anticipating future water quality
As part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program, a study was conducted from 2001 to 2011 to shed light on factors that affect the vulnerability of water from public-supply wells to contamination (referred to hereafter as “public-supply-well vulnerability”). The study was designed as a follow-up to earlier NAWQA studies that found mixtures of contaminants atAuthorsSandra M. Eberts, Mary Ann Thomas, Martha L. JaguckiFilter Total Items: 34Statistical evaluation of variables affecting occurrence of hydrocarbons in aquifers used for public supply, California
The variables affecting the occurrence of hydrocarbons in aquifers used for public supply in California were assessed based on statistical evaluation of three large statewide datasets; gasoline oxygenates also were analyzed for comparison with hydrocarbons. Benzene is the most frequently detected (1.7%) compound among 17 hydrocarbons analyzed at generally low concentrations (median detected concenAuthorsMatthew K. Landon, Carmen A. Burton, Tracy A. Davis, Kenneth Belitz, Tyler D. JohnsonModeling the effects of naturally occurring organic carbon on chlorinated ethene transport to a public supply well
The vulnerability of public supply wells to chlorinated ethene (CE) contamination in part depends on the availability of naturally occurring organic carbon to consume dissolved oxygen (DO) and initiate reductive dechlorination. This was quantified by building a mass balance model of the Kirkwood-Cohansey aquifer, which is widely used for public water supply in New Jersey. This model was built by tAuthorsFrancis H. Chapelle, Leon J. Kauffman, Mark A. WiddowsonHydrothermal contamination of public supply wells in Napa and Sonoma Valleys, California
Groundwater chemistry and isotope data from 44 public supply wells in the Napa and Sonoma Valleys, California were determined to investigate mixing of relatively shallow groundwater with deeper hydrothermal fluids. Multivariate analyses including Cluster Analyses, Multidimensional Scaling (MDS), Principal Components Analyses (PCA), Analysis of Similarities (ANOSIM), and Similarity Percentage AnalyAuthorsMatthew J. Forrest, Justin T. Kulongoski, Matthew S. Edwards, Christopher D. Farrar, Kenneth Belitz, Richard D. NorrisGeogenic sources of benzene in aquifers used for public supply, California
Statistical evaluation of two large statewide data sets from the California State Water Board's Groundwater Ambient Monitoring and Assessment Program (1973 wells) and the California Department of Public Health (12417 wells) reveals that benzene occurs infrequently (1.7%) and at generally low concentrations (median detected concentration of 0.024 μg/L) in groundwater used for public supply in CalifAuthorsMatthew K. Landon, Kenneth BelitzTracerLPM (Version 1): An Excel® workbook for interpreting groundwater age distributions from environmental tracer data
TracerLPM is an interactive Excel® (2007 or later) workbook program for evaluating groundwater age distributions from environmental tracer data by using lumped parameter models (LPMs). Lumped parameter models are mathematical models of transport based on simplified aquifer geometry and flow configurations that account for effects of hydrodynamic dispersion or mixing within the aquifer, well bore,AuthorsBryant C. Jurgens, J.K. Böhlke, Sandra M. EbertsComparison of particle-tracking and lumped-parameter age-distribution models for evaluating vulnerability of production wells to contamination
Environmental age tracers have been used in various ways to help assess vulnerability of drinking-water production wells to contamination. The most appropriate approach will depend on the information that is available and that which is desired. To understand how the well will respond to changing nonpoint-source contaminant inputs at the water table, some representation of the distribution of grounAuthorsS. M. Eberts, J.K. Böhlke, L. J. Kauffman, B.C. JurgensChemical mixtures in untreated water from public-supply wells in the U.S. — Occurrence, composition, and potential toxicity
Chemical mixtures are prevalent in groundwater used for public water supply, but little is known about their potential health effects. As part of a large-scale ambient groundwater study, we evaluated chemical mixtures across multiple chemical classes, and included more chemical contaminants than in previous studies of mixtures in public-supply wells. We (1) assessed the occurrence of chemical mixtAuthorsPatricia L. Toccalino, Julia E. Norman, Jonathon C. ScottAssessing the vulnerability of public-supply wells to contamination: Rio Grande aquifer system in Albuquerque, New Mexico
This fact sheet highlights findings from the vulnerability study of a public-supply well in Albuquerque, New Mexico (hereafter referred to as “the study well”). The study well produces about 3,000 gallons of water per minute from the Rio Grande aquifer system. Water samples were collected at the study well, at two other nearby public-supply wells, and at monitoring wells installed in or near the sAuthorsMartha L. Jagucki, Laura M. Bexfield, Charles E. Heywood, Sandra M. EbertsAssessing the vulnerability of public-supply wells to contamination—Edwards aquifer near San Antonio, Texas
This fact sheet highlights findings from the vulnerability study of a public-supply well field in San Antonio, Texas. The well field consists of six production wells that tap the Edwards aquifer. Typically, one or two wells are pumped at a time, yielding an average total of 20-21 million gallons per day. Water samples were collected from public-supply wells in the well field and from monitoring weAuthorsMartha L. Jagucki, MaryLynn Musgrove, Richard J. Lindgren, Lynne Fahlquist, Sandra M. EbertsModeling the potential impact of seasonal and inactive multi-aquifer wells on contaminant movement to public water-supply wells
Wells screened across multiple aquifers can provide pathways for the movement of surprisingly large volumes of groundwater to confined aquifers used for public water supply (PWS). Using a simple numerical model, we examine the impact of several pumping scenarios on leakage from an unconfined aquifer to a confined aquifer and conclude that a single inactive multi-aquifer well can contribute nearlyAuthorsR.L. Johnson, B.R. Clark, M.K. Landon, L. J. Kauffman, S. M. EbertsOccurrence and concentrations of pharmaceutical compounds in groundwater used for public drinking-water supply in California
Pharmaceutical compounds were detected at low concentrations in 2.3% of 1231 samples of groundwater (median depth to top of screened interval in wells = 61 m) used for public drinking-water supply in California. Samples were collected statewide for the California State Water Resources Control Board's Groundwater Ambient Monitoring and Assessment (GAMA) Program. Of 14 pharmaceutical compounds analyAuthorsMiranda S. Fram, Kenneth BelitzEffects of human-induced alteration of groundwater flow on concentrations of naturally-occurring trace elements at water-supply wells
The effects of human-induced alteration of groundwater flow patterns on concentrations of naturally-occurring trace elements were examined in five hydrologically distinct aquifer systems in the USA. Although naturally occurring, these trace elements can exceed concentrations that are considered harmful to human health. The results show that pumping-induced hydraulic gradient changes and artificialAuthorsJ. D. Ayotte, Z. Szabo, M. J. Focazio, S. M. Eberts