Skip to main content
U.S. flag

An official website of the United States government

Judith C Thomas

Judith Thomas has been a hydrologist with the U.S. Geological Survey for almost 20 years with expertise in groundwater and water quality. Judith is currently the ​section chief for Groundwater and Geophysics in the Central Midwest Water Science Center.

Judith has a B.S. from Purdue University and a M.S. from Indiana University.  Judith started her career with the USGS in July 2000 in Middleton, Wisconsin where she worked on various projects in groundwater, surface water, and water quality.  In 2006, Judith headed west to join the USGS in Grand Junction, Colorado.  Some of Judith's Colorado projects included working in northwest Colorado characterizing groundwater resources in areas of significant energy development for the Bureau of Land Management as well as installing and monitoring a groundwater well network in areas of irrigated Mancos Shale in Delta and Montrose, Colorado.

Science and Products

link
Image Collage of Landsat, pollinator, and volcanologist

Groundwater Monitoring in McHenry County, Illinois

Groundwater Monitoring in McHenry County, Illinois
By
Central Midwest Water Science Center
link

Groundwater Monitoring in McHenry County, Illinois

Groundwater Monitoring in McHenry County, Illinois
Learn More
link
Photo of a survey helicopter

Airborne Electromagnetic (AEM) Survey 2023 - Illinois River Basin

The U.S. Geological Survey (USGS) is conducting an Airborne ElectroMagnetic (AEM) Survey starting in late January 2023 and lasting three to four weeks. A helicopter towing a large hoop from a cable will begin making low-level flights over the Illinois River Basin, covering much of central Illinois and parts of northwest Indiana.
By
Central Midwest Water Science Center
link

Airborne Electromagnetic (AEM) Survey 2023 - Illinois River Basin

The U.S. Geological Survey (USGS) is conducting an Airborne ElectroMagnetic (AEM) Survey starting in late January 2023 and lasting three to four weeks. A helicopter towing a large hoop from a cable will begin making low-level flights over the Illinois River Basin, covering much of central Illinois and parts of northwest Indiana.
Learn More
link
USGS

Lower Gunnison River Basin Groundwater Selenium

The east side of the Uncompahgre River Basin has been a known contributor of dissolved selenium to recipient streams. Discharge of groundwater containing dissolved selenium contributes to surface-water selenium concentrations and loads; however, the groundwater system on the east side of the Uncompahgre River Basin is not well characterized.
By
Colorado Water Science Center
link

Lower Gunnison River Basin Groundwater Selenium

The east side of the Uncompahgre River Basin has been a known contributor of dissolved selenium to recipient streams. Discharge of groundwater containing dissolved selenium contributes to surface-water selenium concentrations and loads; however, the groundwater system on the east side of the Uncompahgre River Basin is not well characterized.
Learn More
link
Piceance Valley

Piceance Basin Water-Quality Data

As large-scale energy development continues in the Piceance Basin, there is potential for changes in surface-water and groundwater resources. In the southern Piceance Basin, a water task force consisting of numerous local governments, municipalities, and energy companies collectively identified the need for a common data repository. In the northern Piceance Basin, similar efforts were underway in...
By
Colorado Water Science Center
link

Piceance Basin Water-Quality Data

As large-scale energy development continues in the Piceance Basin, there is potential for changes in surface-water and groundwater resources. In the southern Piceance Basin, a water task force consisting of numerous local governments, municipalities, and energy companies collectively identified the need for a common data repository. In the northern Piceance Basin, similar efforts were underway in...
Learn More
link
Photo of a ranch near Mt. Sopris, Colorado

Roaring Fork Watershed Water-Quality Data

The Roaring Fork Watershed, located in the Rocky Mountains 150 miles west of Denver, Colorado, has seen rapid development and population growth in recent years. The USGS, in cooperation with Pitkin County, Colorado Water Conservation District, Ruedi Water and Power Authority, and other local entities, conducted a comprehensive surface- and ground-water resource assessment in the Roaring Fork River...
By
Colorado Water Science Center
link

Roaring Fork Watershed Water-Quality Data

The Roaring Fork Watershed, located in the Rocky Mountains 150 miles west of Denver, Colorado, has seen rapid development and population growth in recent years. The USGS, in cooperation with Pitkin County, Colorado Water Conservation District, Ruedi Water and Power Authority, and other local entities, conducted a comprehensive surface- and ground-water resource assessment in the Roaring Fork River...
Learn More

Datasets of depth to water, spring 2016, 2018, and 2020, and spring-to-spring water-level change 2016-18, 2018-20, and 2016-20, Mississippi River Valley alluvial aquifer

This data release consists of 4 data sets--rasters of generalized depth to water in the Mississippi River Valley alluvial aquifer (MRVA) in spring 2016, 2018, and 2020 and a point file of the wells with water-level measurements used to create the depth to water rasters and, for each well with applicable data, the values of water-level change from spring 2016 to spring 2018, spring 2018 to spring 2
By
Nebraska Water Science Center

Datasets used to map the potentiometric surface, Mississippi River Valley alluvial aquifer, spring 2020

A potentiometric-surface map for spring 2020 was created for the Mississippi River Valley alluvial aquifer (MRVA), which was referenced to the North American Vertical Datum of 1988 (NAVD 88), using most of the available groundwater-altitude data from wells and surface-water-altitude data from streamgages. The location and water-level altitude in feet for these wells and streamgages in spring 2020
By
Lower Mississippi-Gulf Water Science Center

Analysis of Escherichia coli, total recoverable iron, and dissolved selenium concentrations and loads for 303(d) listed segments in the Grand Valley, Colorado, 1991-2018

The U.S. Geological Survey, in cooperation with Grand Valley Drainage District, Colorado Water Conservation Board, Colorado Department of Public Health and Environment, and Colorado River Water Conservation District, conducted a loading analysis for selected constituents and tributaries in the Grand Valley, Colorado, to support the development of total maximum daily loads (TMDL) at monitoring loca
By
Colorado Water Science Center

Altitude of the potentiometric surface in the Mississippi River Valley alluvial aquifer, spring 2020

The purpose of this report is to present a potentiometric-surface map for the Mississippi River Valley alluvial aquifer (MRVA). The source data for the map were groundwater-altitude data from wells measured manually or continuously generally in spring 2020 and from the altitude of the top of the water surface measured generally on April 9, 2020, in rivers in the area.
By
Water Resources Mission Area, Nebraska Water Science Center
Video thumbnail reads: NGWOS AEMs for Illinois. Aerially Mapping The Illinois River Basin link
NGWOS AEMs For Illinois - Aerially Mapping the Illinois River Basin
Video thumbnail reads: NGWOS AEMs for Illinois. Aerially Mapping The Illinois River Basin. Audio Description. link
NGWOS AEMs For Illinois - Aerially Mapping the Illinois River Basin (AD)
Person viewed from behind, talking to a group of people facing towards camera, snowy ground and everyone wearing winter gear
link
Burke Minsley speaking to group of USGS employees and Cooperators at AEM survey in southwest Wisconsin 2022
A hydrologist uses a meter to check groundwater parameters in a domestic supply well, with mountains in the background
link
Measuring water-quality parameters in a domestic-supply well
Filter Total Items: 21

Application of geophysical methods to enhance aquifer characterization and groundwater-flow model development, Des Moines River alluvial aquifer, Des Moines, Iowa, 2022

Des Moines Water Works (DMWW) is one of the largest water providers in Iowa and as population growth continues, demand for drinking water is increasing. DMWW uses groundwater and surface water as raw water sources to supply the City of Des Moines and surrounding communities. In response to current and future demands, DMWW is in need of a thorough understanding of local groundwater resources, speci
Authors
Judith C. Thomas, Morgan A. Spring, Lance R. Gruhn, Emilia L. Bristow
By
Central Midwest Water Science Center

Analysis of Escherichia coli, total recoverable iron, and dissolved selenium concentrations, loading, and identifying data gaps for selected 303(d) listed streams, Grand Valley, western Colorado, 1980–2018

Tributaries to the Colorado River in the Grand Valley in western Colorado (segment COLCLC13b) have been placed on the State of Colorado 303(d) list as impaired for Escherichia coli (E. coli), total recoverable iron, and dissolved selenium. The Colorado Department of Public Health and Environment Water Quality Control Division is required to develop total maximum daily loads for these constituents
Authors
Lisa D. Miller, Rachel G. Gidley, Natalie K. Day, Judith C. Thomas
By
Ecosystems Mission Area, Water Resources Mission Area, Colorado Water Science Center, Southwest Biological Science Center

Groundwater quality and hydrology with emphasis on selenium mobilization and transport in the Lower Gunnison River Basin, Colorado, 2012–16

Dissolved selenium is a contaminant of concern in the lower Gunnison River Basin, Colorado. Selenium is naturally present in the Cretaceous Mancos Shale and is leached to groundwater and surface water by irrigation. The groundwater on the east side of the Uncompahgre River in Delta and Montrose Counties is one of the primary sources of selenium concentration and load to surface water in the lower
Authors
Judith C. Thomas, Peter B. McMahon, L. R. Arnold
By
Water Resources Mission Area, Colorado Water Science Center

Groundwater chemistry and water-level elevations in bedrock aquifers of the Piceance and Yellow Creek watersheds, Rio Blanco County, Colorado, 2013–16

The Piceance and Yellow Creek watersheds in Rio Blanco County, Colorado, are known to contain important energy resources (oil shale and natural gas) and mineral resources (nahcolite). The primary sources of fresh groundwater in the Piceance and Yellow Creek watersheds are bedrock aquifers in the Uinta and Green River Formations. The aquifers are divided into an upper and lower aquifer separated by
Authors
Judith C. Thomas, Peter B. McMahon
By
Water Resources Mission Area, Colorado Water Science Center

Streamflow and selenium loads during synoptic sampling of the Gunnison River and its tributaries near Delta, Colorado, November 2015

In response to the need for more information about selenium (Se) sources and transport, the U.S. Geological Survey, in cooperation with the Colorado Water Conservation Board, completed a study that characterized Se loads in a reach of the Gunnison River between Delta and Grand Junction, Colo. This report identifies where possible dissolved Se loading is occurring in a study reach in the Lower Gunn
Authors
Michael R. Stevens, Kenneth J. Leib, Judith C. Thomas, Nancy J. Bauch, Rodney J. Richards
By
Water Resources Mission Area, Colorado Water Science Center

Methane in groundwater from a leaking gas well, Piceance Basin, Colorado, USA

Site-specific and regional analysis of time-series hydrologic and geochemical data collected from 15 monitoring wells in the Piceance Basin indicated that a leaking gas well contaminated shallow groundwater with thermogenic methane. The gas well was drilled in 1956 and plugged and abandoned in 1990. Chemical and isotopic data showed the thermogenic methane was not from mixing of gas-rich formation
Authors
Peter B. McMahon, Judith C. Thomas, John T. Crawford, Mark M. Dornblaser, Andrew G. Hunt
By
Water Resources Mission Area, Colorado Water Science Center

Controls on selenium distribution and mobilization in an irrigated shallow groundwater system underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA

Elevated selenium (Se) concentrations in surface water and groundwater have become a concern in areas of the Western United States due to the deleterious effects of Se on aquatic ecosystems. Elevated Se concentrations are most prevalent in irrigated alluvial valleys underlain by Se-bearing marine shales where Se can be leached from geologic materials into the shallow groundwater and surface water
Authors
Taylor J. Mills, Alisa Mast, Judith C. Thomas, Gabrielle L. Keith
By
Water Resources Mission Area, Colorado Water Science Center

Response of selenium concentrations in groundwater to seasonal canal leakage, lower Gunnison River Basin, Colorado, 2013

Selenium is a water-quality concern in the lower Gunnison River Basin because irrigation water interacting with seleniferous soils derived from the Mancos Shale Formation has mobilized selenium and increased its concentrations in surface water. Understanding the occurrence of elevated selenium concentrations in groundwater is necessary because groundwater discharge is an important source of seleni
Authors
J.I. Linard, P. B. McMahon, L. R. Arnold, J.C. Thomas
By
Water Resources Mission Area, Colorado Water Science Center

Characterization of hydrology and water quality of Piceance Creek in the Alkali Flat area, Rio Blanco County, Colorado, March 2012

Previous studies by the U.S. Geological Survey identified Alkali Flat as an area of groundwater upwelling, with increases in concentrations of total dissolved solids, and streamflow loss, but additional study was needed to better characterize these observations. The U.S. Geological Survey, in cooperation with the Bureau of Land Management, White River Field Office, conducted a study to characteriz
Authors
Judith C. Thomas
By
Water Resources Mission Area, Colorado Water Science Center

Installation of a groundwater monitoring-well network on the east side of the Uncompahgre River in the Lower Gunnison River Basin, Colorado, 2014

The east side of the Uncompahgre River Basin has been a known contributor of dissolved selenium to recipient streams. Discharge of groundwater containing dissolved selenium contributes to surface-water selenium concentrations and loads; however, the groundwater system on the east side of the Uncompahgre River Basin is not well characterized. The U.S. Geological Survey, in cooperation with the Colo
Authors
Judith C. Thomas
By
Water Resources Mission Area, Colorado Water Science Center

Installation of a groundwater monitoring-well network on the east side of the Uncompahgre River in the Lower Gunnison River Basin, Colorado, 2012

The east side of the Uncompahgre River Basin has been a known contributor of dissolved selenium to recipient streams. Discharge of groundwater containing dissolved selenium contributes to surface-water selenium concentrations and loads; however, the groundwater system on the east side of the Uncompahgre River Basin is not well characterized. The U.S. Geological Survey, in cooperation with the Colo
Authors
Judith C. Thomas, L. R. Arnold
By
Water Resources Mission Area, Colorado Water Science Center

Groundwater ages and mixing in the Piceance Basin natural gas province, Colorado

Reliably identifying the effects of energy development on groundwater quality can be difficult because baseline assessments of water quality completed before the onset of energy development are rare and because interactions between hydrocarbon reservoirs and aquifers can be complex, involving both natural and human processes. Groundwater age and mixing data can strengthen interpretations of monito
Authors
Peter B. McMahon, Judith C. Thomas, Andrew G. Hunt
By
Water Resources Mission Area, Colorado Water Science Center

Non-USGS Publications**

Mills, T.J., Mast, M.A., Thomas, J., Keith, G., 2016, Controls on Selenium Distribution and Mobilization in an Irrigated Shallow Groundwater System Underlain by Mancos Shale, Uncompahgre River Basin, Colorado, USA, Science of the Total Environment 566–567 (2016) 1621–1631, http://dx.doi.org/10.1016/j.scitotenv.2016.06.063.
McMahon, P.B., J.C. Thomas, and A.G. Hunt. 2013b. Groundwater ages and mixing in the Piceance Basin natural gas province, Colorado. Environmental Science & Technology 47, no. 4: 13250–13257.
Olyphant, G.A., Thomas, J.C., Whitman, R. L., Harper, D. Characterization and Statistical Modeling of Bacterial (Escherichia Coli) Outflows from Watersheds that Discharge into Southern Lake Michigan; Environmental Monitoring and Assessment 81: 289–300; 2003
Gotkowitz, M. Zeiler, K.K., Dunning, C.P., Thomas, J.C.; Delineation of zones of Contribution for Municipal Wells in Sauk County, Wisconsin; Wisconsin Open File Report 2002-05; 2002
Thomas, J.C.; Monitoring and Statistical Modeling of Bacterially Contaminated Stream-flow at the Outlet of Burns Ditch, South Shore, Lake Michigan, Indiana; unpublished Master’s Thesis, Indiana University, Bloomington, IN; June 2001

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

Science and Products