Peter B McMahon
Peter is a Research Hydrologist with the USGS Colorado Water Science Center in Lakewood, CO.
Pete McMahon’s current research interests include understanding the effects of hydrocarbon production activities on groundwater quality and identifying natural and human processes that create regional- and national-scale patterns in the chemistry of groundwater. He uses geochemical, isotope, noble-gas, and groundwater-age tracers to understand the origin and fate of chemicals of concern in groundwater.
Education and Certifications
Ph.D., 1990, Geology, University of South Carolina at Columbia
M.A., 1984, Geology, University of Texas at Austin
B.S., 1981, Geology, University of Missouri at Columbia
Science and Products
Oxidation/Reduction (Redox)
Groundwater Quality in Principal Aquifers of the United States, 1991—2010
Developing the next generation of USGS resource assessments
NAWQA High Plains Regional Groundwater Study
NAWQA South Platte River Basin Study
Produced water chemistry data collected from the Poso Creek, Midway-Sunset, and Buena Vista Oil Fields, 2020-21, Kern County, California
Water Chemistry data for samples collected at groundwater sites in the Poso Creek Oil Field study area, February 2020-December 2021, Kern County, California
Oil well annular cement and casing damage data in mature oil fields undergoing hydraulic fracturing, South Belridge and Lost Hills Oil Fields, California
Groundwater elevation data and models in and around select California oil fields (ver. 2.0, May 2024)
Data for Distribution of Groundwater Age in Aquifers Used for Public Supply in the Continental United States, 2004 - 2017 (Version 1.1: June 2022)
Geochemical and Geospatial Data for Per- and Polyfluoroalkyl Substances (PFAS) in Groundwater Used As a Source of Drinking Water in the Eastern United States
Quality-Control Data for Volatile Organic Compounds and Environmental Sulfur-Hexafluoride Data for Groundwater Samples from the Williston Basin, USA
Data for Fluoride Occurrence in United States Groundwater
Data Release for Hydrocarbons in Upland Groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
Data for Elevated Manganese Concentrations in United States Groundwater, Role of Land Surface-Soil-Aquifer Connections
Well characteristics, water quality and age-date tracer data for wells along two regional flow paths in the Memphis aquifer, southwest Tennessee
Data from Methane in Aquifers Used for Public Supply in the United States
Groundwater quality near the Placerita Oil Field, California, 2018
Assessing potential effects of oil and gas development activities on groundwater quality near and overlying the Elk Hills and North Coles Levee Oil Fields, San Joaquin Valley, California
Land-use interactions, Oil-Field infrastructure, and natural processes control hydrocarbon and arsenic concentrations in groundwater, Poso Creek Oil Field, California, USA
Spectral characterization of dissolved organic matter in groundwater to assess mixing with oil-field water near selected oil fields, southern California
Fluid migration pathways to groundwater in mature oil fields: Exploring the roles of water injection/production and oil-well integrity in California, USA
Multiple-well monitoring site within the Poso Creek Oil Field, Kern County, California
Groundwater quality near the Montebello Oil Field, Los Angeles County, California
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
Over a third of groundwater in USA public-supply aquifers is Anthropocene-age and susceptible to surface contamination
Occurrence of water and thermogenic gas from oil-bearing formations in groundwater near the Orcutt Oil Field, California, USA
Perfluoroalkyl and polyfluoroalkyl substances in groundwater used as a source of drinking water in the eastern United States
In 2019, 254 samples were collected from five aquifer systems to evaluate per- and polyfluoroalkyl substance (PFAS) occurrence in groundwater used as a source of drinking water in the eastern United States. The samples were analyzed for 24 PFAS, major ions, nutrients, trace elements, dissolved organic carbon (DOC), volatile organic compounds (VOCs), pharmaceuticals, and tritium. Fourteen of the 24
Predicting regional fluoride concentrations at public and domestic supply depths in basin-fill aquifers of the western United States using a random forest model
Science and Products
Oxidation/Reduction (Redox)
Groundwater Quality in Principal Aquifers of the United States, 1991—2010
Developing the next generation of USGS resource assessments
NAWQA High Plains Regional Groundwater Study
NAWQA South Platte River Basin Study
Produced water chemistry data collected from the Poso Creek, Midway-Sunset, and Buena Vista Oil Fields, 2020-21, Kern County, California
Water Chemistry data for samples collected at groundwater sites in the Poso Creek Oil Field study area, February 2020-December 2021, Kern County, California
Oil well annular cement and casing damage data in mature oil fields undergoing hydraulic fracturing, South Belridge and Lost Hills Oil Fields, California
Groundwater elevation data and models in and around select California oil fields (ver. 2.0, May 2024)
Data for Distribution of Groundwater Age in Aquifers Used for Public Supply in the Continental United States, 2004 - 2017 (Version 1.1: June 2022)
Geochemical and Geospatial Data for Per- and Polyfluoroalkyl Substances (PFAS) in Groundwater Used As a Source of Drinking Water in the Eastern United States
Quality-Control Data for Volatile Organic Compounds and Environmental Sulfur-Hexafluoride Data for Groundwater Samples from the Williston Basin, USA
Data for Fluoride Occurrence in United States Groundwater
Data Release for Hydrocarbons in Upland Groundwater, Marcellus Shale Region, Northeastern Pennsylvania and Southern New York, USA
Data for Elevated Manganese Concentrations in United States Groundwater, Role of Land Surface-Soil-Aquifer Connections
Well characteristics, water quality and age-date tracer data for wells along two regional flow paths in the Memphis aquifer, southwest Tennessee
Data from Methane in Aquifers Used for Public Supply in the United States
Groundwater quality near the Placerita Oil Field, California, 2018
Assessing potential effects of oil and gas development activities on groundwater quality near and overlying the Elk Hills and North Coles Levee Oil Fields, San Joaquin Valley, California
Land-use interactions, Oil-Field infrastructure, and natural processes control hydrocarbon and arsenic concentrations in groundwater, Poso Creek Oil Field, California, USA
Spectral characterization of dissolved organic matter in groundwater to assess mixing with oil-field water near selected oil fields, southern California
Fluid migration pathways to groundwater in mature oil fields: Exploring the roles of water injection/production and oil-well integrity in California, USA
Multiple-well monitoring site within the Poso Creek Oil Field, Kern County, California
Groundwater quality near the Montebello Oil Field, Los Angeles County, California
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
Over a third of groundwater in USA public-supply aquifers is Anthropocene-age and susceptible to surface contamination
Occurrence of water and thermogenic gas from oil-bearing formations in groundwater near the Orcutt Oil Field, California, USA
Perfluoroalkyl and polyfluoroalkyl substances in groundwater used as a source of drinking water in the eastern United States
In 2019, 254 samples were collected from five aquifer systems to evaluate per- and polyfluoroalkyl substance (PFAS) occurrence in groundwater used as a source of drinking water in the eastern United States. The samples were analyzed for 24 PFAS, major ions, nutrients, trace elements, dissolved organic carbon (DOC), volatile organic compounds (VOCs), pharmaceuticals, and tritium. Fourteen of the 24