Skip to main content
U.S. flag

An official website of the United States government

Gregory Daniel Clark

Greg is a project chief in the groundwater and water quality section at the Wyoming-Montana Water Science Center.

Greg’s training is in hydrologic response to landscape disturbance and his work typically focuses on the linkages between water chemistry and watershed characteristics. He works with local, state, and federal partners to develop a scientific understanding of watershed response to significant landscape disturbances that can be used in future decision making. This work primarily centers on, but is not limited to, water quality response to wildfire, mining, and logging. Greg has a particular interest in using continuous water quality sensing to characterize event-based response in these landscapes.

Professional Experience

  • 2019 - present Hydrologist [Project Chief], U.S. Geological Survey Wyoming-Montana Water Science Center.

  • 2018 - 2019 Terrestrial Field Ecologist, NSF-Batelle, National Ecological Observatory Network, Front Royal, Virginia.

Education and Certifications

  • M.S. Environmental Science (Soils), Washington State University, 2018.

  • B.S. Environmental Resource Management (Water Science), Pennsylvania State University, 2016.

Science and Products

link
Mule Creek, tributary to Camas Creek (Meagher, Co) at Mule Creek Met Station

Wildfires and Water Quality in Montana

The WY-MT WSC is collaborating with the USGS Water Mission Area and other federal and state partners to quantify and understand the effects wildfires have on water quality. These findings provide high value datasets to researchers and assist resource managers with decision making in fire-prone landscapes throughout Wyoming and Montana. Two watersheds are currently being studied in Montana. Each...
By
Wyoming-Montana Water Science Center
link

Wildfires and Water Quality in Montana

The WY-MT WSC is collaborating with the USGS Water Mission Area and other federal and state partners to quantify and understand the effects wildfires have on water quality. These findings provide high value datasets to researchers and assist resource managers with decision making in fire-prone landscapes throughout Wyoming and Montana. Two watersheds are currently being studied in Montana. Each...
Learn More
link
Clark Fork 4

Long-Term Surface-Water Monitoring in the Upper Clark Fork River Basin

The U.S. Geological Survey (USGS) has collected water-quality samples from selected stream sites upstream from Missoula since 1985.
By
Wyoming-Montana Water Science Center
link

Long-Term Surface-Water Monitoring in the Upper Clark Fork River Basin

The U.S. Geological Survey (USGS) has collected water-quality samples from selected stream sites upstream from Missoula since 1985.
Learn More
No results found.
Filter Total Items: 23

Hysteretic response of suspended-sediment in wildfire affected watersheds of the Pacific Northwest and Southern Rocky Mountains

Wildfires can have a profound impact on hydrosedimentary interactions, or the relationship between sediment and runoff, in forested headwater streams. Quantification of sediment-runoff dynamics at the event scale is integral for understanding source areas and transport of suspended-sediment through a watershed following wildfire. Here we used high-frequency turbidity and stream discharge...
Authors
Gregory D. Clark, Sheila F. Murphy, Katherine Skalak, David Clow, Garrett Alexander Akie, Kurt D. Carpenter, Sean E. Payne, Brian Ebel
By
Wyoming-Montana Water Science Center

An intercomparison of DOC estimated from fDOM sensors in wildfire affected streams of the western United States

Wildfires in the western United States (US) have been demonstrated to affect water quality, including dissolved organic carbon (DOC), in streams. Elevated post-wildfire DOC concentration poses a potential risk to drinking water treatment systems. In-stream measurements of fluorescent dissolved organic matter (fDOM), a proxy for DOC, have shown potential to detect dynamic changes in DOC...
Authors
Garrett Alexander Akie, David Clow, Sheila F. Murphy, Gregory D. Clark, Michael Meador, Brian Ebel
By
Colorado Water Science Center

A call for strategic water-quality monitoring to advance assessment and prediction of wildfire impacts on water supplies

Wildfires pose a risk to water supplies in the western U.S. and many other parts of the world, due to the potential for degradation of water quality. However, a lack of adequate data hinders prediction and assessment of post-wildfire impacts and recovery. The dearth of such data is related to lack of funding for monitoring extreme events and the challenge of measuring the outsized...
Authors
Sheila F. Murphy, Charles N. Alpers, Chauncey W. Anderson, John R. Banta, Johanna Blake, Kurt D. Carpenter, Gregory D. Clark, David Clow, Laura A. Hempel, Deborah A. Martin, Michael Meador, Gregory Mendez, Anke Mueller-Solger, Marc A. Stewart, Sean E. Payne, Cara L. Peterman-Phipps, Brian Ebel
By
Water Resources Mission Area, California Water Science Center, Colorado Water Science Center, Kansas Water Science Center, New Mexico Water Science Center, Oregon Water Science Center, Oklahoma-Texas Water Science Center

Water-quality, bed-sediment, and invertebrate tissue trace-element concentrations for tributaries in the Clark Fork Basin, Montana, October 2019–September 2020

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and monitor trace elements associated...
Authors
Gregory D. Clark, Michelle I. Hornberger, Eric J. Hepler, Terry L. Heinert
By
Water Resources Mission Area, Wyoming-Montana Water Science Center

Sediment transport in the Yankee Fork of the Salmon River near Stanley, Idaho, water years 2012–19

Placer and dredging operations in the Yankee Fork Basin, Idaho, have left more than 5 miles of the lower Yankee Fork of the Salmon River (Yankee Fork) in a highly altered fluvial condition, resulting in poor habitat quantity and quality for native fish species. Since 2011, the Bureau of Reclamation and other stakeholders have implemented a series of restoration efforts to improve the...
Authors
Gregory D. Clark, Scott D. Ducar
By
Water Resources Mission Area, Idaho Water Science Center

Water-quality, bed-sediment, and invertebrate tissue trace-element concentrations for tributaries in the Clark Fork Basin, Montana, October 2018–September 2019

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and monitor trace elements associated...
Authors
Gregory D. Clark, Michelle I. Hornberger, Eric J. Hepler, Tom E. Cleasby, Terry L. Heinert
By
Water Resources Mission Area, Wyoming-Montana Water Science Center

Seasonal dynamics and interannual variability in mercury concentrations and loads through a three-reservoir complex

The Hells Canyon Complex (HCC) along the Snake River (Idaho-Oregon border, USA) encompasses three successive reservoirs that seasonally stratify, creating anoxic conditions in the hypolimnion that promote methylmercury (MeHg) production. This study quantified seasonal dynamics and interannual variability in mercury concentrations (inorganic divalent mercury (IHg) and MeHg) and loads at...
Authors
Austin K. Baldwin, Brett Poulin, Jesse Naymik, Charles Hoovestol, Gregory D. Clark, David Krabbenhoft
By
Water Resources Mission Area, Idaho Water Science Center, Upper Midwest Water Science Center, Mercury Research Laboratory

Water-quality, bed-sediment, and invertebrate tissue trace-element concentrations for tributaries in the Clark Fork Basin, Montana, October 2017–September 2018

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and monitor trace elements associated...
Authors
Gregory D. Clark, Michelle I. Hornberger, Tom E. Cleasby, Terry L. Heinert, Matthew A. Turner
By
Water Resources Mission Area, Wyoming-Montana Water Science Center

Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon

Introduction The Hells Canyon Complex (HCC) is a hydroelectric project built and operated by the Idaho Power Company (IPC) that consists of three dams on the Snake River along the Oregon and Idaho border (fig. 1). The dams have resulted in the creation of Brownlee, Oxbow, and Hells Canyon Reservoirs, which have a combined storage capacity of more than 1.5 million acre-feet and span about...
Authors
Gregory D. Clark, Jesse Naymik, David Krabbenhoft, Collin Eagles-Smith, George R. Aiken, Mark C. Marvin-DiPasquale, Reed C. Harris, Ralph Myers
By
Ecosystems Mission Area, Water Resources Mission Area, Forest and Rangeland Ecosystem Science Center, Idaho Water Science Center, Upper Midwest Water Science Center, Mercury Research Laboratory

Sources, transport, and trends for selected trace metals and nutrients in the Coeur d'Alene and Spokane River Basins, Idaho, 1990-2013

Data collected at 18 streamflow-gaging and water-quality sampling sites in the Coeur d’Alene and Spokane River Basins of northern Idaho were used to estimate mean streamflow‑weighted concentrations and annual loads of total and dissolved cadmium, lead, and zinc, and total phosphorus (TP) and nitrogen (TN) for water years (WYs) 2009–13. Chronic Ambient Water Quality Criteria (AWQC) and...
Authors
Gregory D. Clark, Christopher A. Mebane
By
Water Resources Mission Area, Idaho Water Science Center

Sediment transport in the lower Snake and Clearwater River Basins, Idaho and Washington, 2008–11

Sedimentation is an ongoing maintenance problem for reservoirs, limiting reservoir storage capacity and navigation. Because Lower Granite Reservoir in Washington is the most upstream of the four U.S. Army Corps of Engineers reservoirs on the lower Snake River, it receives and retains the largest amount of sediment. In 2008, in cooperation with the U.S. Army Corps of Engineers, the U.S...
Authors
Gregory D. Clark, Ryan L. Fosness, Molly S. Wood
By
Water Resources Mission Area, Idaho Water Science Center

The quality of our nation's waters: Nutrients in the nation's streams and groundwater, 1992-2004

National Findings and Their ImplicationsAlthough the use of artificial fertilizer has supported increasing food production to meet the needs of a growing population, increases in nutrient loadings from agricultural and, to a lesser extent, urban sources have resulted in nutrient concentrations in many streams and parts of aquifers that exceed standards for protection of human health and...
Authors
Neil Dubrovsky, Karen R. Burow, Gregory D. Clark, JoAnn M. Gronberg, Pixie A. Hamilton, Kerie J. Hitt, David S. Mueller, Mark D. Munn, Bernard T. Nolan, Larry Puckett, Michael G. Rupert, Terry M. Short, Norman E. Spahr, Lori A. Sprague, William G. Wilber
By
Water Resources Mission Area, Colorado Water Science Center

Non-USGS Publications**

GD Clark, KB Moffett (2018). Multiple wildfire disturbances amplify seasonal moisture stress in a moist, mixed-conifer montane ecosystem. Washington State University. Pullman, Washington.

**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

link
Mule Creek, tributary to Camas Creek (Meagher, Co) at Mule Creek Met Station

Wildfires and Water Quality in Montana

The WY-MT WSC is collaborating with the USGS Water Mission Area and other federal and state partners to quantify and understand the effects wildfires have on water quality. These findings provide high value datasets to researchers and assist resource managers with decision making in fire-prone landscapes throughout Wyoming and Montana. Two watersheds are currently being studied in Montana. Each...
By
Wyoming-Montana Water Science Center
link

Wildfires and Water Quality in Montana

The WY-MT WSC is collaborating with the USGS Water Mission Area and other federal and state partners to quantify and understand the effects wildfires have on water quality. These findings provide high value datasets to researchers and assist resource managers with decision making in fire-prone landscapes throughout Wyoming and Montana. Two watersheds are currently being studied in Montana. Each...
Learn More
link
Clark Fork 4

Long-Term Surface-Water Monitoring in the Upper Clark Fork River Basin

The U.S. Geological Survey (USGS) has collected water-quality samples from selected stream sites upstream from Missoula since 1985.
By
Wyoming-Montana Water Science Center
link

Long-Term Surface-Water Monitoring in the Upper Clark Fork River Basin

The U.S. Geological Survey (USGS) has collected water-quality samples from selected stream sites upstream from Missoula since 1985.
Learn More
No results found.
Filter Total Items: 23

Hysteretic response of suspended-sediment in wildfire affected watersheds of the Pacific Northwest and Southern Rocky Mountains

Wildfires can have a profound impact on hydrosedimentary interactions, or the relationship between sediment and runoff, in forested headwater streams. Quantification of sediment-runoff dynamics at the event scale is integral for understanding source areas and transport of suspended-sediment through a watershed following wildfire. Here we used high-frequency turbidity and stream discharge...
Authors
Gregory D. Clark, Sheila F. Murphy, Katherine Skalak, David Clow, Garrett Alexander Akie, Kurt D. Carpenter, Sean E. Payne, Brian Ebel
By
Wyoming-Montana Water Science Center

An intercomparison of DOC estimated from fDOM sensors in wildfire affected streams of the western United States

Wildfires in the western United States (US) have been demonstrated to affect water quality, including dissolved organic carbon (DOC), in streams. Elevated post-wildfire DOC concentration poses a potential risk to drinking water treatment systems. In-stream measurements of fluorescent dissolved organic matter (fDOM), a proxy for DOC, have shown potential to detect dynamic changes in DOC...
Authors
Garrett Alexander Akie, David Clow, Sheila F. Murphy, Gregory D. Clark, Michael Meador, Brian Ebel
By
Colorado Water Science Center

A call for strategic water-quality monitoring to advance assessment and prediction of wildfire impacts on water supplies

Wildfires pose a risk to water supplies in the western U.S. and many other parts of the world, due to the potential for degradation of water quality. However, a lack of adequate data hinders prediction and assessment of post-wildfire impacts and recovery. The dearth of such data is related to lack of funding for monitoring extreme events and the challenge of measuring the outsized...
Authors
Sheila F. Murphy, Charles N. Alpers, Chauncey W. Anderson, John R. Banta, Johanna Blake, Kurt D. Carpenter, Gregory D. Clark, David Clow, Laura A. Hempel, Deborah A. Martin, Michael Meador, Gregory Mendez, Anke Mueller-Solger, Marc A. Stewart, Sean E. Payne, Cara L. Peterman-Phipps, Brian Ebel
By
Water Resources Mission Area, California Water Science Center, Colorado Water Science Center, Kansas Water Science Center, New Mexico Water Science Center, Oregon Water Science Center, Oklahoma-Texas Water Science Center

Water-quality, bed-sediment, and invertebrate tissue trace-element concentrations for tributaries in the Clark Fork Basin, Montana, October 2019–September 2020

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and monitor trace elements associated...
Authors
Gregory D. Clark, Michelle I. Hornberger, Eric J. Hepler, Terry L. Heinert
By
Water Resources Mission Area, Wyoming-Montana Water Science Center

Sediment transport in the Yankee Fork of the Salmon River near Stanley, Idaho, water years 2012–19

Placer and dredging operations in the Yankee Fork Basin, Idaho, have left more than 5 miles of the lower Yankee Fork of the Salmon River (Yankee Fork) in a highly altered fluvial condition, resulting in poor habitat quantity and quality for native fish species. Since 2011, the Bureau of Reclamation and other stakeholders have implemented a series of restoration efforts to improve the...
Authors
Gregory D. Clark, Scott D. Ducar
By
Water Resources Mission Area, Idaho Water Science Center

Water-quality, bed-sediment, and invertebrate tissue trace-element concentrations for tributaries in the Clark Fork Basin, Montana, October 2018–September 2019

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and monitor trace elements associated...
Authors
Gregory D. Clark, Michelle I. Hornberger, Eric J. Hepler, Tom E. Cleasby, Terry L. Heinert
By
Water Resources Mission Area, Wyoming-Montana Water Science Center

Seasonal dynamics and interannual variability in mercury concentrations and loads through a three-reservoir complex

The Hells Canyon Complex (HCC) along the Snake River (Idaho-Oregon border, USA) encompasses three successive reservoirs that seasonally stratify, creating anoxic conditions in the hypolimnion that promote methylmercury (MeHg) production. This study quantified seasonal dynamics and interannual variability in mercury concentrations (inorganic divalent mercury (IHg) and MeHg) and loads at...
Authors
Austin K. Baldwin, Brett Poulin, Jesse Naymik, Charles Hoovestol, Gregory D. Clark, David Krabbenhoft
By
Water Resources Mission Area, Idaho Water Science Center, Upper Midwest Water Science Center, Mercury Research Laboratory

Water-quality, bed-sediment, and invertebrate tissue trace-element concentrations for tributaries in the Clark Fork Basin, Montana, October 2017–September 2018

Water, bed sediment, and invertebrate tissue were sampled in streams from Butte to near Missoula, Montana, as part of a monitoring program in the Clark Fork Basin. The sampling program was completed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to characterize aquatic resources in the Clark Fork Basin and monitor trace elements associated...
Authors
Gregory D. Clark, Michelle I. Hornberger, Tom E. Cleasby, Terry L. Heinert, Matthew A. Turner
By
Water Resources Mission Area, Wyoming-Montana Water Science Center

Mercury cycling in the Hells Canyon Complex of the Snake River, Idaho and Oregon

Introduction The Hells Canyon Complex (HCC) is a hydroelectric project built and operated by the Idaho Power Company (IPC) that consists of three dams on the Snake River along the Oregon and Idaho border (fig. 1). The dams have resulted in the creation of Brownlee, Oxbow, and Hells Canyon Reservoirs, which have a combined storage capacity of more than 1.5 million acre-feet and span about...
Authors
Gregory D. Clark, Jesse Naymik, David Krabbenhoft, Collin Eagles-Smith, George R. Aiken, Mark C. Marvin-DiPasquale, Reed C. Harris, Ralph Myers
By
Ecosystems Mission Area, Water Resources Mission Area, Forest and Rangeland Ecosystem Science Center, Idaho Water Science Center, Upper Midwest Water Science Center, Mercury Research Laboratory

Sources, transport, and trends for selected trace metals and nutrients in the Coeur d'Alene and Spokane River Basins, Idaho, 1990-2013

Data collected at 18 streamflow-gaging and water-quality sampling sites in the Coeur d’Alene and Spokane River Basins of northern Idaho were used to estimate mean streamflow‑weighted concentrations and annual loads of total and dissolved cadmium, lead, and zinc, and total phosphorus (TP) and nitrogen (TN) for water years (WYs) 2009–13. Chronic Ambient Water Quality Criteria (AWQC) and...
Authors
Gregory D. Clark, Christopher A. Mebane
By
Water Resources Mission Area, Idaho Water Science Center

Sediment transport in the lower Snake and Clearwater River Basins, Idaho and Washington, 2008–11

Sedimentation is an ongoing maintenance problem for reservoirs, limiting reservoir storage capacity and navigation. Because Lower Granite Reservoir in Washington is the most upstream of the four U.S. Army Corps of Engineers reservoirs on the lower Snake River, it receives and retains the largest amount of sediment. In 2008, in cooperation with the U.S. Army Corps of Engineers, the U.S...
Authors
Gregory D. Clark, Ryan L. Fosness, Molly S. Wood
By
Water Resources Mission Area, Idaho Water Science Center

The quality of our nation's waters: Nutrients in the nation's streams and groundwater, 1992-2004

National Findings and Their ImplicationsAlthough the use of artificial fertilizer has supported increasing food production to meet the needs of a growing population, increases in nutrient loadings from agricultural and, to a lesser extent, urban sources have resulted in nutrient concentrations in many streams and parts of aquifers that exceed standards for protection of human health and...
Authors
Neil Dubrovsky, Karen R. Burow, Gregory D. Clark, JoAnn M. Gronberg, Pixie A. Hamilton, Kerie J. Hitt, David S. Mueller, Mark D. Munn, Bernard T. Nolan, Larry Puckett, Michael G. Rupert, Terry M. Short, Norman E. Spahr, Lori A. Sprague, William G. Wilber
By
Water Resources Mission Area, Colorado Water Science Center

Non-USGS Publications**

GD Clark, KB Moffett (2018). Multiple wildfire disturbances amplify seasonal moisture stress in a moist, mixed-conifer montane ecosystem. Washington State University. Pullman, Washington.

**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.

Was this page helpful?