Charles Crawford is a Scientist Emeritus (Hydrologist) with the U.S. Geological Survey (USGS), Ohio-Kentucky-Indiana Water Science Center (OKI WSC)
As a Scientist Emeritus he advises staff from the OKI WSC and USGS Water Mission Area on use of statistical methods for data analysis and is developing an approach for estimating uncertainty in stream temperature measurements. Charles joined the USGS in 1978 and has worked on a variety of water-quality investigations since. Prior to his retirement he was the Coordinator for Data Analysis and Statistics in the USGS Water Resources Mission Area, Earth System Processes Division, Water Resources Assessment Branch. Prior to that position he managed the USGS National Water Quality Assessment Project (NAWQA) and National Stream Quality Accounting Network (NASQAN) stream quality monitoring networks, a position he held from 2005 to 2015. From 2000 to 2005 he was a member of the NAWQA Pesticide National Synthesis Project Team where he helped develop the Watershed Regressions for Pesticide (WARP) model approach for estimating pesticide concentrations in streams. Before working for the NAWQA National Synthesis project, he was Chief of the NAWQA White River Basin Study for 10 years. He has served on the Indianapolis Department of Capital Asset Management Wet Weather Technical Advisory Committee, a work group organized by the International Life Sciences Institute for the U.S. Environmental Protection Agency (EPA) to provide input on strategies for determining pesticide exposure in drinking water, and an EPA lead interagency scientific working group charged with using National Water Quality Assessment Project pesticide data to help meet the goals of the Food Quality Protection Act. He is the author or co-author of over 60 articles and technical reports. He is also a co-author of the U.S. Geological Survey LOADEST program for estimating constituent loads in streams. Charles received the U.S. Department of the Interior (DOI) Superior Service Award in 1999 and the Department’s Meritorious Service Award in 2008. He was also a co-recipient of the USGS Eugene M. Shoemaker Communication Award in 2007. Charles has a B.A. degree in Biology from the University of Indianapolis and M.S. and Ph.D. degrees in Environmental Science from Indiana University.
Science and Products
Datasets for the Report Entitled: "A Method for Addressing Differences in Concentrations of Fipronil and Three Degradates Obtained by Two Different Laboratory Methods"
This report provides data input and computation results for a method developed by Crawford and Martin (2017) to address differences in concentrations of fipronil and three degradates obtained by two different laboratory methods. Data are arranged in 9 tables that include water-quality site information, laboratory recovery data, laboratory analyses results and measured water-sample concentrations a
Filter Total Items: 68
Comparison of surrogate models to estimate pesticide concentrations at six U.S. Geological Survey National Water Quality Network sites during water years 2013–18
During water years 2013–18, the U.S. Geological Survey National Water-Quality Assessment Project sampled the National Water Quality Network for Rivers and Streams year-round and reported on 221 pesticides at 72 sites across the United States. Pesticides are difficult to measure, their concentrations often represent discrete snapshots in time, and capturing peak concentrations is expensive. Three t
Development of an approach for integrating components of the U.S. Geological Survey Biomonitoring of Environmental Status and Trends (BEST) and National Stream Quantity Accounting Network (NASQAN) programs for large U.S. rivers
A national-scale framework for monitoring environmental contaminants in fish and effects of contaminant exposure on fish in large U.S. rivers has been proposed by the Biomonitoring of Environmental Status and Trends (BEST) Program of the U.S. Geological Survey (USGS). The framework shares many features and objectives with the USGS National Stream Quantity Accounting Network (NASQAN) Program, which
Methods for computing water-quality loads at sites in the U.S. Geological Survey National Water Quality Network
The U.S. Geological Survey currently (2020) publishes information on concentrations and loads of water-quality constituents at 110 sites across the United States as part of the U.S. Geological Survey National Water Quality Network (NWQN). This report details historical and updated methods for computing water-quality loads at NWQN sites. The primary updates to historical load estimation methods inc
An evaluation of methods for computing annual water-quality loads
The U.S. Geological Survey publishes information on the mass, or load, of water-quality constituents transported through rivers and streams sampled as part of the operation of the National Water Quality Network (NWQN). This study evaluates methods for computing annual water-quality loads, specifically with respect to procedures currently (2019) used at sites in the NWQN. Near-daily datasets of chl
A method for addressing differences in concentrations of fipronil and three degradates obtained by two different laboratory methods
In October 2012, the U.S. Geological Survey (USGS) began measuring the concentration of the pesticide fipronil and three of its degradates (desulfinylfipronil, fipronil sulfide, and fipronil sulfone) by a new laboratory method using direct aqueous-injection liquid chromatography tandem mass spectrometry (DAI LC–MS/MS). This method replaced the previous method—in use since 2002—that used gas chroma
Long-term changes in nitrate conditions over the 20th century in two Midwestern Corn Belt streams
Long-term changes in nitrate concentration and flux between the middle of the 20th century and the first decade of the 21st century were estimated for the Des Moines River and the Middle Illinois River, two Midwestern Corn Belt streams, using a novel weighted regression approach that is able to detect subtle changes in solute transport behavior over time. The results show that the largest changes
An evaluation of methods for estimating decadal stream loads
Effective management of water resources requires accurate information on the mass, or load of water-quality constituents transported from upstream watersheds to downstream receiving waters. Despite this need, no single method has been shown to consistently provide accurate load estimates among different water-quality constituents, sampling sites, and sampling regimes. We evaluate the accuracy of s
Regional and temporal differences in nitrate trends discerned from long-term water quality monitoring data
Riverine nitrate (NO3) is a well-documented driver of eutrophication and hypoxia in coastal areas. The development of the elevated river NO3 concentration is linked to anthropogenic inputs from municipal, agricultural, and atmospheric sources. The intensity of these sources has varied regionally, through time, and in response to multiple causes such as economic drivers and policy responses. This s
Mississippi River nitrate loads from high frequency sensor measurements and regression-based load estimation
Accurately quantifying nitrate (NO3–) loading from the Mississippi River is important for predicting summer hypoxia in the Gulf of Mexico and targeting nutrient reduction within the basin. Loads have historically been modeled with regression-based techniques, but recent advances with high frequency NO3– sensors allowed us to evaluate model performance relative to measured loads in the lower Missis
Long-term trends in alkalinity in large rivers of the conterminous US in relation to acidification, agriculture, and hydrologic modification
Alkalinity increases in large rivers of the conterminous US are well known, but less is understood about the processes leading to these trends as compared with headwater systems more intensively examined in conjunction with acid deposition studies. Nevertheless, large rivers are important conduits of inorganic carbon and other solutes to coastal areas and may have substantial influence on coastal
Watershed Regressions for Pesticides (WARP) models for predicting stream concentrations of multiple pesticides
Watershed Regressions for Pesticides for multiple pesticides (WARP-MP) are statistical models developed to predict concentration statistics for a wide range of pesticides in unmonitored streams. The WARP-MP models use the national atrazine WARP models in conjunction with an adjustment factor for each additional pesticide. The WARP-MP models perform best for pesticides with application timing and m
Assessing total nitrogen in surface-water samples--precision and bias of analytical and computational methods
The characterization of total-nitrogen (TN) concentrations is an important component of many surface-water-quality programs. However, three widely used methods for the determination of total nitrogen—(1) derived from the alkaline-persulfate digestion of whole-water samples (TN-A); (2) calculated as the sum of total Kjeldahl nitrogen and dissolved nitrate plus nitrite (TN-K); and (3) calculated as
Science and Products
- Data
Datasets for the Report Entitled: "A Method for Addressing Differences in Concentrations of Fipronil and Three Degradates Obtained by Two Different Laboratory Methods"
This report provides data input and computation results for a method developed by Crawford and Martin (2017) to address differences in concentrations of fipronil and three degradates obtained by two different laboratory methods. Data are arranged in 9 tables that include water-quality site information, laboratory recovery data, laboratory analyses results and measured water-sample concentrations a - Publications
Filter Total Items: 68
Comparison of surrogate models to estimate pesticide concentrations at six U.S. Geological Survey National Water Quality Network sites during water years 2013–18
During water years 2013–18, the U.S. Geological Survey National Water-Quality Assessment Project sampled the National Water Quality Network for Rivers and Streams year-round and reported on 221 pesticides at 72 sites across the United States. Pesticides are difficult to measure, their concentrations often represent discrete snapshots in time, and capturing peak concentrations is expensive. Three tDevelopment of an approach for integrating components of the U.S. Geological Survey Biomonitoring of Environmental Status and Trends (BEST) and National Stream Quantity Accounting Network (NASQAN) programs for large U.S. rivers
A national-scale framework for monitoring environmental contaminants in fish and effects of contaminant exposure on fish in large U.S. rivers has been proposed by the Biomonitoring of Environmental Status and Trends (BEST) Program of the U.S. Geological Survey (USGS). The framework shares many features and objectives with the USGS National Stream Quantity Accounting Network (NASQAN) Program, whichMethods for computing water-quality loads at sites in the U.S. Geological Survey National Water Quality Network
The U.S. Geological Survey currently (2020) publishes information on concentrations and loads of water-quality constituents at 110 sites across the United States as part of the U.S. Geological Survey National Water Quality Network (NWQN). This report details historical and updated methods for computing water-quality loads at NWQN sites. The primary updates to historical load estimation methods incAn evaluation of methods for computing annual water-quality loads
The U.S. Geological Survey publishes information on the mass, or load, of water-quality constituents transported through rivers and streams sampled as part of the operation of the National Water Quality Network (NWQN). This study evaluates methods for computing annual water-quality loads, specifically with respect to procedures currently (2019) used at sites in the NWQN. Near-daily datasets of chlA method for addressing differences in concentrations of fipronil and three degradates obtained by two different laboratory methods
In October 2012, the U.S. Geological Survey (USGS) began measuring the concentration of the pesticide fipronil and three of its degradates (desulfinylfipronil, fipronil sulfide, and fipronil sulfone) by a new laboratory method using direct aqueous-injection liquid chromatography tandem mass spectrometry (DAI LC–MS/MS). This method replaced the previous method—in use since 2002—that used gas chromaLong-term changes in nitrate conditions over the 20th century in two Midwestern Corn Belt streams
Long-term changes in nitrate concentration and flux between the middle of the 20th century and the first decade of the 21st century were estimated for the Des Moines River and the Middle Illinois River, two Midwestern Corn Belt streams, using a novel weighted regression approach that is able to detect subtle changes in solute transport behavior over time. The results show that the largest changesAn evaluation of methods for estimating decadal stream loads
Effective management of water resources requires accurate information on the mass, or load of water-quality constituents transported from upstream watersheds to downstream receiving waters. Despite this need, no single method has been shown to consistently provide accurate load estimates among different water-quality constituents, sampling sites, and sampling regimes. We evaluate the accuracy of sRegional and temporal differences in nitrate trends discerned from long-term water quality monitoring data
Riverine nitrate (NO3) is a well-documented driver of eutrophication and hypoxia in coastal areas. The development of the elevated river NO3 concentration is linked to anthropogenic inputs from municipal, agricultural, and atmospheric sources. The intensity of these sources has varied regionally, through time, and in response to multiple causes such as economic drivers and policy responses. This sMississippi River nitrate loads from high frequency sensor measurements and regression-based load estimation
Accurately quantifying nitrate (NO3–) loading from the Mississippi River is important for predicting summer hypoxia in the Gulf of Mexico and targeting nutrient reduction within the basin. Loads have historically been modeled with regression-based techniques, but recent advances with high frequency NO3– sensors allowed us to evaluate model performance relative to measured loads in the lower MissisLong-term trends in alkalinity in large rivers of the conterminous US in relation to acidification, agriculture, and hydrologic modification
Alkalinity increases in large rivers of the conterminous US are well known, but less is understood about the processes leading to these trends as compared with headwater systems more intensively examined in conjunction with acid deposition studies. Nevertheless, large rivers are important conduits of inorganic carbon and other solutes to coastal areas and may have substantial influence on coastalWatershed Regressions for Pesticides (WARP) models for predicting stream concentrations of multiple pesticides
Watershed Regressions for Pesticides for multiple pesticides (WARP-MP) are statistical models developed to predict concentration statistics for a wide range of pesticides in unmonitored streams. The WARP-MP models use the national atrazine WARP models in conjunction with an adjustment factor for each additional pesticide. The WARP-MP models perform best for pesticides with application timing and mAssessing total nitrogen in surface-water samples--precision and bias of analytical and computational methods
The characterization of total-nitrogen (TN) concentrations is an important component of many surface-water-quality programs. However, three widely used methods for the determination of total nitrogen—(1) derived from the alkaline-persulfate digestion of whole-water samples (TN-A); (2) calculated as the sum of total Kjeldahl nitrogen and dissolved nitrate plus nitrite (TN-K); and (3) calculated as