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
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Transport of nitrate in the Mississippi river in July-August 1999
Lagrangian sampling was conducted on the Mississippi River in late July through early August 1999 to test the hypothesis that nitrate (NO3-) is transported conservatively in the Mississippi River. Three different approaches were pursued to test the hypothesis: (1) a mass balance for NO3- was evaluated for evidence of net gains and losses, (2) stable isotopes of NO3- were measured (δ15N and δ18O) t
Authors
Richard H. Coupe, Donald A. Goolsby, William A. Battaglin, John Karl Böhlke, Peter B. McMahon, Carol Kendall
Overview of groundwater quality in the Piceance Basin, western Colorado, 1946--2009
Groundwater-quality data from public and private sources for the period 1946 to 2009 were compiled and put into a common data repository for the Piceance Basin. The data repository is available on the web at http://rmgsc.cr.usgs.gov/cwqdr/Piceance/index.shtml. A subset of groundwater-quality data from the repository was compiled, reviewed, and checked for quality assurance for this report. The res
Authors
J.C. Thomas, P. B. McMahon
Assessing the relative bioavailability of DOC in regional groundwater systems
It has been hypothesized that the degree to which a hyperbolic relationship exists between concentrations of dissolved organic carbon (DOC) and dissolved oxygen (DO) in groundwater may indicate the relative bioavailability of DOC. This hypothesis was examined for 73 different regional aquifers of the United States using 7745 analyses of groundwater compiled by the National Water Assessment (NAWQA)
Authors
Francis H. Chapelle, Paul M. Bradley, Celeste A. Journey, Peter B. McMahon
Use of classes based on redox and groundwater age to characterize the susceptibility of principal aquifers to changes in nitrate concentrations, 1991 to 2010
The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey is using multiple approaches to measure and explain trends in concentrations of nitrate in principal aquifers of the United States. Near decadal sampling of selected well networks is providing information on where long-term changes in nitrate concentrations have occurred. Because those studies do not include all th
Authors
P. B. McMahon
Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley
Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results i
Authors
Bridget R. Scanlon, Claudia C. Faunt, Laurent Longuevergne, Robert C. Reedy, William M. Alley, Virginia L. McGuire, Peter B. McMahon
Preliminary assessment of sources of nitrogen in groundwater at a biosolids-application area near Deer Trail
Concentrations of dissolved nitrite plus nitrate increased fairly steadily in samples from four shallow groundwater monitoring wells after biosolids applications to nonirrigated farmland began in 1993. The U.S. Geological Survey began a preliminary assessment of sources of nitrogen in shallow groundwater at part of the biosolids-application area near Deer Trail, Colorado, in 2005 in cooperation wi
Authors
Tracy J.B. Yager, Peter B. McMahon
Groundwater-quality and quality-control data for two monitoring wells near Pavillion, Wyoming, April and May 2012
In June 2010, the U.S. Environmental Protection Agency installed two deep monitoring wells (MW01 and MW02) near Pavillion, Wyoming, to study groundwater quality. During April and May 2012, the U.S Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, collected groundwater-quality data and quality-control data from monitoring well MW01 and, following well redevelop
Authors
Peter R. Wright, Peter B. McMahon, David K. Mueller, Melanie L. Clark
Sampling and analysis plan for the characterization of groundwater quality in two monitoring wells near Pavillion, Wyoming
In June 2010, the U.S. Environmental Protection Agency installed two deep monitoring wells (MW01 and MW02) near Pavillion, Wyoming to study groundwater quality. The U.S Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, designed a plan to collect groundwater data from these monitoring wells. This sampling and analysis plan describes the sampling equipment that
Authors
Peter R. Wright, Peter B. McMahon
Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater
Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in t
Authors
Francis H. Chapelle, Paul M. Bradley, Peter B. McMahon, Karl Kaiser, Ron Benner
Evolution of redox processes in groundwater
No abstract available.
Authors
Peter B. McMahon, Francis H. Chapelle, Paul M. Bradley
Use of diverse geochemical data sets to determine sources and sinks of nitrate and methane in groundwater, Garfield County, Colorado, 2009
Previous water-quality assessments reported elevated concentrations of nitrate and methane in water from domestic wells screened in shallow zones of the Wasatch Formation, Garfield County, Colorado. In 2009, the U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, analyzed samples collected from 26 domestic wells for a diverse set of geochemical tra
Authors
P. B. McMahon, J.C. Thomas, A.G. Hunt
A comparison of recharge rates in aquifers of the United States based on groundwater-age data
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater rec
Authors
P. B. McMahon, Niel Plummer, J.K. Böhlke, S.D. Shapiro, S.R. Hinkle
Science and Products
Filter Total Items: 14
No Result Found
Filter Total Items: 112
Transport of nitrate in the Mississippi river in July-August 1999
Lagrangian sampling was conducted on the Mississippi River in late July through early August 1999 to test the hypothesis that nitrate (NO3-) is transported conservatively in the Mississippi River. Three different approaches were pursued to test the hypothesis: (1) a mass balance for NO3- was evaluated for evidence of net gains and losses, (2) stable isotopes of NO3- were measured (δ15N and δ18O) t
Authors
Richard H. Coupe, Donald A. Goolsby, William A. Battaglin, John Karl Böhlke, Peter B. McMahon, Carol Kendall
Overview of groundwater quality in the Piceance Basin, western Colorado, 1946--2009
Groundwater-quality data from public and private sources for the period 1946 to 2009 were compiled and put into a common data repository for the Piceance Basin. The data repository is available on the web at http://rmgsc.cr.usgs.gov/cwqdr/Piceance/index.shtml. A subset of groundwater-quality data from the repository was compiled, reviewed, and checked for quality assurance for this report. The res
Authors
J.C. Thomas, P. B. McMahon
Assessing the relative bioavailability of DOC in regional groundwater systems
It has been hypothesized that the degree to which a hyperbolic relationship exists between concentrations of dissolved organic carbon (DOC) and dissolved oxygen (DO) in groundwater may indicate the relative bioavailability of DOC. This hypothesis was examined for 73 different regional aquifers of the United States using 7745 analyses of groundwater compiled by the National Water Assessment (NAWQA)
Authors
Francis H. Chapelle, Paul M. Bradley, Celeste A. Journey, Peter B. McMahon
Use of classes based on redox and groundwater age to characterize the susceptibility of principal aquifers to changes in nitrate concentrations, 1991 to 2010
The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey is using multiple approaches to measure and explain trends in concentrations of nitrate in principal aquifers of the United States. Near decadal sampling of selected well networks is providing information on where long-term changes in nitrate concentrations have occurred. Because those studies do not include all th
Authors
P. B. McMahon
Groundwater depletion and sustainability of irrigation in the US High Plains and Central Valley
Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results i
Authors
Bridget R. Scanlon, Claudia C. Faunt, Laurent Longuevergne, Robert C. Reedy, William M. Alley, Virginia L. McGuire, Peter B. McMahon
Preliminary assessment of sources of nitrogen in groundwater at a biosolids-application area near Deer Trail
Concentrations of dissolved nitrite plus nitrate increased fairly steadily in samples from four shallow groundwater monitoring wells after biosolids applications to nonirrigated farmland began in 1993. The U.S. Geological Survey began a preliminary assessment of sources of nitrogen in shallow groundwater at part of the biosolids-application area near Deer Trail, Colorado, in 2005 in cooperation wi
Authors
Tracy J.B. Yager, Peter B. McMahon
Groundwater-quality and quality-control data for two monitoring wells near Pavillion, Wyoming, April and May 2012
In June 2010, the U.S. Environmental Protection Agency installed two deep monitoring wells (MW01 and MW02) near Pavillion, Wyoming, to study groundwater quality. During April and May 2012, the U.S Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, collected groundwater-quality data and quality-control data from monitoring well MW01 and, following well redevelop
Authors
Peter R. Wright, Peter B. McMahon, David K. Mueller, Melanie L. Clark
Sampling and analysis plan for the characterization of groundwater quality in two monitoring wells near Pavillion, Wyoming
In June 2010, the U.S. Environmental Protection Agency installed two deep monitoring wells (MW01 and MW02) near Pavillion, Wyoming to study groundwater quality. The U.S Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, designed a plan to collect groundwater data from these monitoring wells. This sampling and analysis plan describes the sampling equipment that
Authors
Peter R. Wright, Peter B. McMahon
Dissolved oxygen as an indicator of bioavailable dissolved organic carbon in groundwater
Concentrations of dissolved oxygen (DO) plotted vs. dissolved organic carbon (DOC) in groundwater samples taken from a coastal plain aquifer of South Carolina (SC) showed a statistically significant hyperbolic relationship. In contrast, DO-DOC plots of groundwater samples taken from the eastern San Joaquin Valley of California (CA) showed a random scatter. It was hypothesized that differences in t
Authors
Francis H. Chapelle, Paul M. Bradley, Peter B. McMahon, Karl Kaiser, Ron Benner
Evolution of redox processes in groundwater
No abstract available.
Authors
Peter B. McMahon, Francis H. Chapelle, Paul M. Bradley
Use of diverse geochemical data sets to determine sources and sinks of nitrate and methane in groundwater, Garfield County, Colorado, 2009
Previous water-quality assessments reported elevated concentrations of nitrate and methane in water from domestic wells screened in shallow zones of the Wasatch Formation, Garfield County, Colorado. In 2009, the U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, analyzed samples collected from 26 domestic wells for a diverse set of geochemical tra
Authors
P. B. McMahon, J.C. Thomas, A.G. Hunt
A comparison of recharge rates in aquifers of the United States based on groundwater-age data
An overview is presented of existing groundwater-age data and their implications for assessing rates and timescales of recharge in selected unconfined aquifer systems of the United States. Apparent age distributions in aquifers determined from chlorofluorocarbon, sulfur hexafluoride, tritium/helium-3, and radiocarbon measurements from 565 wells in 45 networks were used to calculate groundwater rec
Authors
P. B. McMahon, Niel Plummer, J.K. Böhlke, S.D. Shapiro, S.R. Hinkle