Groundwater is an important source of drinking water in the United States. In order to assess the status and long-term sustainability of this important resource, I use environmental tracers, geochemical modeling, and statistical methods to understand the age structure, geochemical processes, and trends affecting water-quality in aquifers.
Science and Products
Groundwater Age
The age of groundwater is key in predicting which contaminants it might contain. There are many tracers and techniques that allow us to estimate the age—or mix of ages—of the groundwater we depend on as a drinking water supply.
Inverse Model Data for: Salinity trends in a groundwater system supplemented by 50 years of imported Colorado River water
Data provided here describe the contribution of up to 7 different water sources to the major ion geochemistry of U.S. Geological Survey (USGS) and California State Water Resources Control Board Division of Drinking Water (CA-DDW) groundwater samples within the Indio Subbasin of the Coachella Valley, California. The Inverse Geochemical Modeling was performed in the USGS's PHREEQC ver. 3 program and
Data for karst groundwater vulnerability determined by modeled age and residence time tracers
Groundwater samples collected from the Edwards aquifer in south-central Texas were analyzed for water-quality data to assess aquifer susceptibility to contaminants. Water-quality data included environmental tracers of groundwater age (tritium, tritiogenic helium-3, sulfur hexafluoride, carbon-14, and radiogenic helium-4), calibrated to lumped parameter models (LPMs). Groundwater samples were colle
Data for Per- and Polyfluoroalkyl Substances (PFAS) in groundwater samples collected by the California Groundwater Ambient Monitoring and Assessment Priority Basin Project, 2019-2023
The California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) analyzed for per-and polyfluoroalkyl substances (PFAS) in groundwater samples collected from domestic and public drinking water supply wells in California. GAMA-PBP is a cooperative program between the U.S. Geological Survey and the California State Water Resources Control Board.
This data relea
Data for Distribution of Groundwater Age in Aquifers Used for Public Supply in the Continental United States, 2004 - 2017 (Version 1.1: June 2022)
This data release documents seven tables that contain environmental tracer data and lumped parameter model (LPM) results that are used for assessing the distribution of groundwater age in 21 Principal Aquifers of the continental United States. Groundwater samples were collected from 1,279 sites and analyzed for environmental tracers: tritium, tritiogenic helium-3, sulfur hexafluoride, carbon-14, a
Data for assessing the penetration depth post-1950s water in the Central Valley aquifer system, California (July 2022)
This dataset provides groundwater ages estimates that were used in an assessment of the penetration depth of modern groundwater in the Central Valley aquifer system (CVAL). Groundwater ages were estimated by calibration of environmental tracers (tritium, tritiogenic helium-3, chlorofluorocarbons, sulfur hexafluoride, carbon-14 and radiogenic helium-4) to lumped parameter models (LPMs) for samples
Data for Time Scales of Arsenic Variability and the Role of High-Frequency Monitoring at Three Water-Supply Wells in New Hampshire, USA
This data release consists of data (in four tables) for assessing the time scales of arsenic variability in three production wells in New Hampshire; tables that describe the data fields in the data tables are also included in the data release. High-frequency (every 5 to 15 minutes) and bi-monthly water-quality monitoring of a bedrock-aquifer domestic well (425651070573701), a bedrock-aquifer publi
Data for Assessing the Lead Solubility Potential of Untreated Groundwater of the United States
Groundwater chemistry data used for assessing the lead (Pb) solubility potential of untreated groundwater of the United States were compiled from the USGS National Water Information System (NWIS) database for groundwater sites sampled between January 1, 2000 and January 1, 2016. Two datasets were compiled: one dataset having 13,324 groundwater sites was used to assess Pb occurrence in untreated gr
Geochemical Correction of Carbon-14 in Dissolved Inorganic Carbon used for Groundwater Age Dating in the Glacial Aquifer System, Conterminous United States
Data provided here describe geochemical correction of carbon-14 in dissolved inorganic carbon (DIC) for groundwater age dating. Datasets include major ion chemistry of groundwater samples, model parameter inputs, and final corrected carbon-14 in DIC. Geochemical correction was completed in two phases: determination of reactive phase mole transfers through an inverse geochemical model (PHREEQC; Par
Data for Radium 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 (1 Myr) in the most downgradien
Well characteristics, water quality and age-date tracer data for wells along two regional flow paths in the Memphis aquifer, southwest Tennessee
In 2013, water-quality and age-date tracer samples were collected at wells located along two flow paths in the Memphis aquifer, southwest Tennessee, as part of the National Water Quality Assessment (NAWQA) Project of the National Water-Quality Program to better understand the vulnerability of the aquifer to contamination.. Each flow path began in the aquifer outcrop area (shallow well depths) and
Filter Total Items: 55
Salinity trends in a groundwater system supplemented by 50 years of imported Colorado River water
The Indio subbasin of the Coachella Valley is a desert area of southern California where a growing population depends primarily on groundwater for drinking and agricultural uses. The aquifer system has been supplemented with Colorado River water through managed recharge and widespread irrigation since the mid-20th century. We use a combination of geochemical modeling and trend analysis to identify
Authors
Jennifer S. Harkness, Patrick Michael McCarthy, Bryant Jurgens, Zeno Levy
Karst groundwater vulnerability determined by modeled age and residence time tracers
Karst aquifers are a vital groundwater resource globally, but features such as rapid recharge and conduit flow make them highly vulnerable to land-surface contamination. We apply environmental age tracers to the south-central Texas Edwards aquifer, a karst resource in a rapidly urbanizing and drought-prone region, to assess vulnerability to land-surface contamination and risks unique to karst aqui
Authors
MaryLynn Musgrove, Bryant Jurgens, Stephen P. Opsahl
Modeling the dynamic penetration depth of post-1950s water in unconfined aquifers using environmental tracers: Central Valley, California
The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contamination. Here, we compute D-1950 values at wells, interpolate them in space, and project them across time to map the moving front of modern recharge in four dimensions in the Central Valley aquifer system, California, USA. Tracers
Authors
Kirsten Faulkner, Bryant Jurgens, Stefan Voss, Danielle Dupuy, Zeno Levy
Quality of groundwater used for public supply in the continental United States: A comprehensive assessment
The presence of contaminants in a source water can constrain its suitability for drinking. The quality of groundwater used for public supply was assessed in 25 principal aquifers (PAs) that account for 84% of groundwater pumped for public supply in the U.S. (89.6 million people on a proportional basis). Each PA was sampled across its lateral extent using an equal-area grid, typically with 60 wells
Authors
Kenneth Belitz, Miranda S. Fram, Bruce D. Lindsey, Paul Stackelberg, Laura M. Bexfield, Tyler D. Johnson, Bryant Jurgens, James A. Kingsbury, Peter B. McMahon, Neil M. Dubrovsky
Over a third of groundwater in USA public-supply aquifers is Anthropocene-age and susceptible to surface contamination
The distribution of groundwater age is useful for evaluating the susceptibility and sustainability of groundwater resources. Here, we compute the aquifer-scale cumulative distribution function to characterize the age distribution for 21 Principal Aquifers that account for ~80% of public-supply pumping in the United States. The aquifer-scale cumulative distribution function for each Principal Aquif
Authors
Bryant Jurgens, Kirsten Faulkner, Peter B. McMahon, Andrew Hunt, Gerolamo C. Casile, Megan B. Young, Kenneth Belitz
Effects of imported recharge on fluoride trends in groundwater used for public supply in California
Fluoride is a naturally occurring element in groundwater that supports bone and dental health at low concentrations but can cause health problems at elevated concentrations in drinking water. This study investigates spatial and temporal trends for fluoride concentrations in untreated groundwater from over 20,000 public supply wells in California. The presence of a significant temporal trend in flu
Authors
Jennifer S. Harkness, Bryant Jurgens
Critical aquifer overdraft accelerates degradation of groundwater quality in California’s Central Valley during drought
Drought-induced pumpage has precipitated dramatic groundwater-level declines in California’s Central Valley over the past 30 years, but the impacts of aquifer overdraft on water quality are poorly understood. This study coupled over 160,000 measurements of nitrate from ∼6,000 public-supply wells with a 30-year reconstruction of groundwater levels throughout the Central Valley to evaluate dynamic r
Authors
Zeno Levy, Bryant Jurgens, Karen R. Burow, Stefan Voss, Kirsten Faulkner, Jose Alfredo Arroyo-Lopez, Miranda S. Fram
A multi-tracer and well-bore flow profile approach to determine occurrence, movement, and sources of perchlorate in groundwater
The purpose of this study is to determine the occurrence, movement and sources of perchlorate in groundwater using a comprehensive set of environmental tracers coupled with discreet borehole data. Potential sources of perchlorate to groundwater at the study site have been attributed to waste disposal and industrial activities as well as to past agricultural operations. Perchlorate concentrations i
Authors
Michael Wright, John A. Izbicki, Bryant C. Jurgens
Groundwater residence time estimates obscured by anthropogenic carbonate
Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers (14C, 3H, 39Ar, and 85Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California’s San Joaquin Valley (SJV), an agricultural region that is heavil
Authors
Alan Seltzer, David Bekaert, Peter H. Barry, Kathryn Durkin, Emily Mace, Craig E. Aaselth, Jake Zappala, Peter Mueller, Bryant Jurgens, Justin T. Kulongoski
Groundwater development leads to decreasing arsenic concentrations in the San Joaquin Valley, California
In the San Joaquin Valley (SJV), California, about 10% of drinking water wells since 2010 had arsenic concentrations above the US maximum contaminant level of 10 μg/L. High concentrations of arsenic are often associated with high pH (greater than 7.8) or reduced geochemical conditions. Although most wells have low arsenic (<3 μg/L) and do not have changing arsenic concentrations, this study found
Authors
Emily A. Haugen, Bryant Jurgens, Jose Alfredo Arroyo-Lopez, George L. Bennett V
DGMETA (version 1)—Dissolved gas modeling and environmental tracer analysis computer program
DGMETA (Dissolved Gas Modeling and Environmental Tracer Analysis) is a Microsoft Excel-based computer program that is used for modeling air-water equilibrium conditions from measurements of dissolved gases and for computing concentrations of environmental tracers that rely on air-water equilibrium model results. DGMETA can solve for the temperature, salinity, excess air, fractionation of gases, or
Authors
Bryant C. Jurgens, J. K. Böhlke, Karl Haase, Eurybiades Busenberg, Andrew G. Hunt, Jeffrey A. Hansen
Geochemistry and age of groundwater in the Williston Basin, USA: Assessing potential effects of shale-oil production on groundwater quality
Thirty water wells were sampled in 2018 to understand the geochemistry and age of groundwater in the Williston Basin and assess potential effects of shale-oil production from the Three Forks-Bakken petroleum system (TBPS) on groundwater quality. Two geochemical groups are identified using hierarchical cluster analysis. Group 1 represents the younger (median 4He = 21.49 × 10−8 cm3 STP/g), less chem
Authors
Peter B. McMahon, Joel M. Galloway, Andrew Hunt, Kenneth Belitz, Bryant Jurgens, Tyler D. Johnson
Groundwater Age Mixtures & Contaminant Trends Tool (GAMACTT)
Use this Groundwater Age Mixtures and Contaminant Trends Tool (GAMACTT) to explore the effects of basic aquifer properties and well configurations on groundwater age mixtures in groundwater discharge and on contaminant trends from varying nonpoint-source contaminant input scenarios.
TracerLPM
An Excel® Workbook for Interpreting Groundwater Age Distributions from Environmental Tracer Data
Science and Products
- Science
Groundwater Age
The age of groundwater is key in predicting which contaminants it might contain. There are many tracers and techniques that allow us to estimate the age—or mix of ages—of the groundwater we depend on as a drinking water supply. - Data
Inverse Model Data for: Salinity trends in a groundwater system supplemented by 50 years of imported Colorado River water
Data provided here describe the contribution of up to 7 different water sources to the major ion geochemistry of U.S. Geological Survey (USGS) and California State Water Resources Control Board Division of Drinking Water (CA-DDW) groundwater samples within the Indio Subbasin of the Coachella Valley, California. The Inverse Geochemical Modeling was performed in the USGS's PHREEQC ver. 3 program andData for karst groundwater vulnerability determined by modeled age and residence time tracers
Groundwater samples collected from the Edwards aquifer in south-central Texas were analyzed for water-quality data to assess aquifer susceptibility to contaminants. Water-quality data included environmental tracers of groundwater age (tritium, tritiogenic helium-3, sulfur hexafluoride, carbon-14, and radiogenic helium-4), calibrated to lumped parameter models (LPMs). Groundwater samples were colleData for Per- and Polyfluoroalkyl Substances (PFAS) in groundwater samples collected by the California Groundwater Ambient Monitoring and Assessment Priority Basin Project, 2019-2023
The California Groundwater Ambient Monitoring and Assessment Program Priority Basin Project (GAMA-PBP) analyzed for per-and polyfluoroalkyl substances (PFAS) in groundwater samples collected from domestic and public drinking water supply wells in California. GAMA-PBP is a cooperative program between the U.S. Geological Survey and the California State Water Resources Control Board. This data releaData for Distribution of Groundwater Age in Aquifers Used for Public Supply in the Continental United States, 2004 - 2017 (Version 1.1: June 2022)
This data release documents seven tables that contain environmental tracer data and lumped parameter model (LPM) results that are used for assessing the distribution of groundwater age in 21 Principal Aquifers of the continental United States. Groundwater samples were collected from 1,279 sites and analyzed for environmental tracers: tritium, tritiogenic helium-3, sulfur hexafluoride, carbon-14, aData for assessing the penetration depth post-1950s water in the Central Valley aquifer system, California (July 2022)
This dataset provides groundwater ages estimates that were used in an assessment of the penetration depth of modern groundwater in the Central Valley aquifer system (CVAL). Groundwater ages were estimated by calibration of environmental tracers (tritium, tritiogenic helium-3, chlorofluorocarbons, sulfur hexafluoride, carbon-14 and radiogenic helium-4) to lumped parameter models (LPMs) for samplesData for Time Scales of Arsenic Variability and the Role of High-Frequency Monitoring at Three Water-Supply Wells in New Hampshire, USA
This data release consists of data (in four tables) for assessing the time scales of arsenic variability in three production wells in New Hampshire; tables that describe the data fields in the data tables are also included in the data release. High-frequency (every 5 to 15 minutes) and bi-monthly water-quality monitoring of a bedrock-aquifer domestic well (425651070573701), a bedrock-aquifer publiData for Assessing the Lead Solubility Potential of Untreated Groundwater of the United States
Groundwater chemistry data used for assessing the lead (Pb) solubility potential of untreated groundwater of the United States were compiled from the USGS National Water Information System (NWIS) database for groundwater sites sampled between January 1, 2000 and January 1, 2016. Two datasets were compiled: one dataset having 13,324 groundwater sites was used to assess Pb occurrence in untreated grGeochemical Correction of Carbon-14 in Dissolved Inorganic Carbon used for Groundwater Age Dating in the Glacial Aquifer System, Conterminous United States
Data provided here describe geochemical correction of carbon-14 in dissolved inorganic carbon (DIC) for groundwater age dating. Datasets include major ion chemistry of groundwater samples, model parameter inputs, and final corrected carbon-14 in DIC. Geochemical correction was completed in two phases: determination of reactive phase mole transfers through an inverse geochemical model (PHREEQC; ParData for Radium 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 (1 Myr) in the most downgradienWell characteristics, water quality and age-date tracer data for wells along two regional flow paths in the Memphis aquifer, southwest Tennessee
In 2013, water-quality and age-date tracer samples were collected at wells located along two flow paths in the Memphis aquifer, southwest Tennessee, as part of the National Water Quality Assessment (NAWQA) Project of the National Water-Quality Program to better understand the vulnerability of the aquifer to contamination.. Each flow path began in the aquifer outcrop area (shallow well depths) and - Multimedia
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Filter Total Items: 55
Salinity trends in a groundwater system supplemented by 50 years of imported Colorado River water
The Indio subbasin of the Coachella Valley is a desert area of southern California where a growing population depends primarily on groundwater for drinking and agricultural uses. The aquifer system has been supplemented with Colorado River water through managed recharge and widespread irrigation since the mid-20th century. We use a combination of geochemical modeling and trend analysis to identifyAuthorsJennifer S. Harkness, Patrick Michael McCarthy, Bryant Jurgens, Zeno LevyKarst groundwater vulnerability determined by modeled age and residence time tracers
Karst aquifers are a vital groundwater resource globally, but features such as rapid recharge and conduit flow make them highly vulnerable to land-surface contamination. We apply environmental age tracers to the south-central Texas Edwards aquifer, a karst resource in a rapidly urbanizing and drought-prone region, to assess vulnerability to land-surface contamination and risks unique to karst aquiAuthorsMaryLynn Musgrove, Bryant Jurgens, Stephen P. OpsahlModeling the dynamic penetration depth of post-1950s water in unconfined aquifers using environmental tracers: Central Valley, California
The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contamination. Here, we compute D-1950 values at wells, interpolate them in space, and project them across time to map the moving front of modern recharge in four dimensions in the Central Valley aquifer system, California, USA. TracersAuthorsKirsten Faulkner, Bryant Jurgens, Stefan Voss, Danielle Dupuy, Zeno LevyQuality of groundwater used for public supply in the continental United States: A comprehensive assessment
The presence of contaminants in a source water can constrain its suitability for drinking. The quality of groundwater used for public supply was assessed in 25 principal aquifers (PAs) that account for 84% of groundwater pumped for public supply in the U.S. (89.6 million people on a proportional basis). Each PA was sampled across its lateral extent using an equal-area grid, typically with 60 wells
AuthorsKenneth Belitz, Miranda S. Fram, Bruce D. Lindsey, Paul Stackelberg, Laura M. Bexfield, Tyler D. Johnson, Bryant Jurgens, James A. Kingsbury, Peter B. McMahon, Neil M. DubrovskyOver a third of groundwater in USA public-supply aquifers is Anthropocene-age and susceptible to surface contamination
The distribution of groundwater age is useful for evaluating the susceptibility and sustainability of groundwater resources. Here, we compute the aquifer-scale cumulative distribution function to characterize the age distribution for 21 Principal Aquifers that account for ~80% of public-supply pumping in the United States. The aquifer-scale cumulative distribution function for each Principal AquifAuthorsBryant Jurgens, Kirsten Faulkner, Peter B. McMahon, Andrew Hunt, Gerolamo C. Casile, Megan B. Young, Kenneth BelitzEffects of imported recharge on fluoride trends in groundwater used for public supply in California
Fluoride is a naturally occurring element in groundwater that supports bone and dental health at low concentrations but can cause health problems at elevated concentrations in drinking water. This study investigates spatial and temporal trends for fluoride concentrations in untreated groundwater from over 20,000 public supply wells in California. The presence of a significant temporal trend in fluAuthorsJennifer S. Harkness, Bryant JurgensCritical aquifer overdraft accelerates degradation of groundwater quality in California’s Central Valley during drought
Drought-induced pumpage has precipitated dramatic groundwater-level declines in California’s Central Valley over the past 30 years, but the impacts of aquifer overdraft on water quality are poorly understood. This study coupled over 160,000 measurements of nitrate from ∼6,000 public-supply wells with a 30-year reconstruction of groundwater levels throughout the Central Valley to evaluate dynamic rAuthorsZeno Levy, Bryant Jurgens, Karen R. Burow, Stefan Voss, Kirsten Faulkner, Jose Alfredo Arroyo-Lopez, Miranda S. FramA multi-tracer and well-bore flow profile approach to determine occurrence, movement, and sources of perchlorate in groundwater
The purpose of this study is to determine the occurrence, movement and sources of perchlorate in groundwater using a comprehensive set of environmental tracers coupled with discreet borehole data. Potential sources of perchlorate to groundwater at the study site have been attributed to waste disposal and industrial activities as well as to past agricultural operations. Perchlorate concentrations iAuthorsMichael Wright, John A. Izbicki, Bryant C. JurgensGroundwater residence time estimates obscured by anthropogenic carbonate
Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers (14C, 3H, 39Ar, and 85Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California’s San Joaquin Valley (SJV), an agricultural region that is heavilAuthorsAlan Seltzer, David Bekaert, Peter H. Barry, Kathryn Durkin, Emily Mace, Craig E. Aaselth, Jake Zappala, Peter Mueller, Bryant Jurgens, Justin T. KulongoskiGroundwater development leads to decreasing arsenic concentrations in the San Joaquin Valley, California
In the San Joaquin Valley (SJV), California, about 10% of drinking water wells since 2010 had arsenic concentrations above the US maximum contaminant level of 10 μg/L. High concentrations of arsenic are often associated with high pH (greater than 7.8) or reduced geochemical conditions. Although most wells have low arsenic (<3 μg/L) and do not have changing arsenic concentrations, this study foundAuthorsEmily A. Haugen, Bryant Jurgens, Jose Alfredo Arroyo-Lopez, George L. Bennett VDGMETA (version 1)—Dissolved gas modeling and environmental tracer analysis computer program
DGMETA (Dissolved Gas Modeling and Environmental Tracer Analysis) is a Microsoft Excel-based computer program that is used for modeling air-water equilibrium conditions from measurements of dissolved gases and for computing concentrations of environmental tracers that rely on air-water equilibrium model results. DGMETA can solve for the temperature, salinity, excess air, fractionation of gases, orAuthorsBryant C. Jurgens, J. K. Böhlke, Karl Haase, Eurybiades Busenberg, Andrew G. Hunt, Jeffrey A. HansenGeochemistry and age of groundwater in the Williston Basin, USA: Assessing potential effects of shale-oil production on groundwater quality
Thirty water wells were sampled in 2018 to understand the geochemistry and age of groundwater in the Williston Basin and assess potential effects of shale-oil production from the Three Forks-Bakken petroleum system (TBPS) on groundwater quality. Two geochemical groups are identified using hierarchical cluster analysis. Group 1 represents the younger (median 4He = 21.49 × 10−8 cm3 STP/g), less chemAuthorsPeter B. McMahon, Joel M. Galloway, Andrew Hunt, Kenneth Belitz, Bryant Jurgens, Tyler D. Johnson - Software
Groundwater Age Mixtures & Contaminant Trends Tool (GAMACTT)
Use this Groundwater Age Mixtures and Contaminant Trends Tool (GAMACTT) to explore the effects of basic aquifer properties and well configurations on groundwater age mixtures in groundwater discharge and on contaminant trends from varying nonpoint-source contaminant input scenarios.
TracerLPM
An Excel® Workbook for Interpreting Groundwater Age Distributions from Environmental Tracer Data
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