Zachary C. Johnson
Research Hydrologist for the Washington Water Science Center
My research interests are at the intersection of watershed hydrology, ecology, biogeochemistry, water and land management, and fluvial geomorphology using field measurements, remote sensing, laboratory, and modeling techniques. I am particularly passionate about topics such as surface-subsurface exchanges, terrestrial-aquatic linkages, anthropogenic interactions, statistical and deterministic modeling, and the importance of spatial and temporal scale for watershed processes.
Professional Experience
2023 to present – Research Hydrologist, US Geological Survey, Washington Water Science Center
2020 to 2023 – Hydrologist, US Geological Survey, Washington Water Science Center
2018 to 2020 – Research Associate/Scientist, University of Washington
2016 to 2017 – ORISE Postdoctoral Fellow, US Environmental Protection Agency
2014 to 2016 – Contractor/Research Ecologist, US Geological Survey, Leetown Science Center
Education and Certifications
Ph.D. 2014. Hydrology, University of Nevada, Reno, NV
M.S. 2010. Hydrology, University of Nevada, Reno, NV
B.A. 2007. ACS Chemistry (Mathematics minor), Concordia College, Moorhead, MN
Science and Products
Filter Total Items: 15
Long-term monotonic trends in annual groundwater metrics in the United States through 2020 (ver. 4.0, May 2025) Long-term monotonic trends in annual groundwater metrics in the United States through 2020 (ver. 4.0, May 2025)
The U.S. Geological Survey (USGS) Water Resources Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand by delivering routine assessments of water supply and demand. A key part of these national assessments is identifying long-term trends in water availability, including groundwater and surface...
Long-term water-quality trends for rivers and streams within the contiguous United States using Weighted Regressions on Time, Discharge, and Season (WRTDS) (ver. 1.1, March 2025) Long-term water-quality trends for rivers and streams within the contiguous United States using Weighted Regressions on Time, Discharge, and Season (WRTDS) (ver. 1.1, March 2025)
The U.S. Geological Survey (USGS) Water Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand for water need by delivering routine assessments of water supply and demand. It is also improving understanding of the natural and human factors affecting the balance between supply and demand. A key...
Long-term monotonic trends in annual and monthly streamflow metrics at streamgages in the United States (ver. 2.0, October 2024) Long-term monotonic trends in annual and monthly streamflow metrics at streamgages in the United States (ver. 2.0, October 2024)
The U.S. Geological Survey (USGS) Water Resources Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand for water need by delivering routine assessments of water supply and demand and an understanding of the natural and human factors affecting the balance between supply and demand. A key part of...
Long-term monotonic trends in annual and monthly stream temperature metrics at multi-source monitoring locations in the United States (ver. 2.0, June 2025) Long-term monotonic trends in annual and monthly stream temperature metrics at multi-source monitoring locations in the United States (ver. 2.0, June 2025)
The U.S. Geological Survey (USGS) Water Resources Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand for water need by delivering routine assessments of water supply and demand and an understanding of the natural and human factors affecting the balance between supply and demand. A key part of...
Passive seismic data collected along headwater stream corridors in Shenandoah National Park in 2016 - 2020 Passive seismic data collected along headwater stream corridors in Shenandoah National Park in 2016 - 2020
In July 2016, July 2019, and March 2020, 318 seismic recordings were acquired at locations within Shenandoah National Park, Virginia, using MOHO Tromino Model TEP-3C three-component seismometers to assess depth to bedrock using the HVSR method. This method requires a measurement of estimate of shear wave velocity, which depends on the regolith sediment composition and density, for the...
Spatial patterns of dewatering within watersheds of Shenandoah National Park, Virginia 2016 - 2021 (ver. 2.0, December 2021) Spatial patterns of dewatering within watersheds of Shenandoah National Park, Virginia 2016 - 2021 (ver. 2.0, December 2021)
These data describe longitudinal (upstream to downstream) patterns of dewatering during summer baseflow (July-September) conditions in nine watersheds in Shenandoah National park. In July-August of 2016 all nine watersheds (Jeremy's Run, Hazel River, Piney River, Hughes River, Staunton River, Whiteoak Canyon Run, Paine Run, Meadow Run, and Big Run) were evaluated for dewatering. In...
Filter Total Items: 19
Closing the gap between science and management of cold-water refuges in rivers and streams Closing the gap between science and management of cold-water refuges in rivers and streams
Human activities and climate change threaten coldwater organisms in freshwater ecosystems by causing rivers and streams to warm, increasing the intensity and frequency of warm temperature events, and reducing thermal heterogeneity. Cold-water refuges are discrete patches of relatively cool water that are used by coldwater organisms for thermal relief and short-term survival. Globally...
Authors
Francine H. Mejia, Valerie Ouellet, Martin A. Briggs, Stephanie M. Carlson, Rose Casas-Mulet, Mollie Chapman, Matthias J. Collins, Stephen J. Dugdale, Joseph L. Ebersole, Danielle M. Frechette, Aimee H. Fullerton, Carol-Anne Gillis, Zachary Johnson, Christa Kelleher, Barret L. Kurylyk, Rebecca Lave, Benjamin Letcher, Knut M. Myrvold, Tracie-Lynn Nadeau, Helen Neville, Herve Piégay, Kathryn E. Smith, Diego Tonolla, Christian E. Torgersen
Integrated water resources trend assessments: State of the science, challenges, and opportunities for advancement Integrated water resources trend assessments: State of the science, challenges, and opportunities for advancement
Water is vital to human life and healthy ecosystems. Here we outline the current state of national-scale water resources trend assessments, identify key gaps, and suggest advancements to better address critical issues related to changes in water resources that may threaten human development or the environment. Questions like, “Do we have less suitable drinking water now than we had 20...
Authors
Sarah M. Stackpoole, Gretchen P. Oelsner, Edward G. Stets, Jory Seth Hecht, Zachary Johnson, Anthony J. Tesoriero, Michelle A. Walvoord, Jeffrey G. Chanat, Krista A. Dunne, Phillip J. Goodling, Bruce D. Lindsey, Michael R. Meador, Sarah A. Spaulding
Paired Air and Stream Temperature Analysis (PASTA) to evaluate groundwater influence on streams Paired Air and Stream Temperature Analysis (PASTA) to evaluate groundwater influence on streams
Groundwater is critical for maintaining stream baseflow and thermal stability; however, the influence of groundwater on streamflow has been difficult to evaluate at broad spatial scales. Techniques such as baseflow separation necessitate streamflow records and do not directly indicate whether groundwater inflow may be sourced from more dynamic shallow flowpaths. We present a web tool...
Authors
Danielle K. Hare, Susanne A. Benz, Barret L. Kurylyk, Zachary Johnson, Neil C. Terry, Ashley M. Helton
Puget Sound Spatially Referenced Regression on Watershed Attributes (SPARROW) Puget Sound Spatially Referenced Regression on Watershed Attributes (SPARROW)
The United States Geological Survey (USGS) and the Washington State Department of Ecology (Ecology) are collaborating on the development of refined, seasonal load estimates of total nitrogen and total phosphorus within watersheds draining to Washington waters of the Salish Sea for the period 2005-2020. The modeling approach for this work is based on SPARROW (Spatially Referenced...
Authors
Cristiana Figueroa-Kaminsky, Jamie K. Wasielewski, Sheelagh McCarthy, Noah M. Schmadel, Daniel R. Wise, Zachary Johnson, Robert W. Black
Bedrock depth influences spatial patterns of summer baseflow, temperature and flow disconnection for mountainous headwater streams Bedrock depth influences spatial patterns of summer baseflow, temperature and flow disconnection for mountainous headwater streams
In mountain headwater streams, the quality and resilience of summer cold-water habitat is generally regulated by stream discharge, longitudinal stream channel connectivity and groundwater exchange. These critical hydrologic processes are thought to be influenced by the stream corridor bedrock contact depth (sediment thickness), a parameter often inferred from sparse hillslope borehole...
Authors
Martin A. Briggs, Phillip J. Goodling, Zachary Johnson, Karli M. Rogers, Nathaniel P. Hitt, Jennifer H. Fair, Craig D. Snyder
Continental-scale analysis of shallow and deep groundwater contributions to streams Continental-scale analysis of shallow and deep groundwater contributions to streams
Groundwater discharge generates streamflow and influences stream thermal regimes. However, the water quality and thermal buffering capacity of groundwater depends on the aquifer source-depth. Here, we pair multi-year air and stream temperature signals to categorize 1729 sites across the continental United States as having major dam influence, shallow or deep groundwater signatures, or...
Authors
D. Hare, A. M. Helton, Zachary C. Johnson, John W. Lane, Martin A. Briggs
Non-USGS Publications**
Johnson, Z.C., B.G. Johnson, M.A. Briggs, W.D. Devine, C.D. Snyder, N.P. Hitt, D.K. Hare, and T.V. Minkova (2020). “Paired air-water annual temperature patterns reveal hydrogeological controls on stream thermal regimes at watershed to continental scales”, J. Hydrology, 587, 124929.
Aho, K., J. Flotemersch, R. Hill, Z.C. Johnson, S.G. Leibowitz, and M. Weber (2020). “Adapting the Index of Watershed Integrity for watershed managers in the Western Balkans Region”, Environmental Management, 65, 602-617.
Johnson, Z.C., S.G. Leibowitz, and R.A. Hill (2019). “Revising the national maps of watershed integrity,” Sci. Total Environ., 651(2), 2615-2630.
Kuhn, A., S.G. Leibowitz, Z.C. Johnson, J. Lin, J.A. Massie, J.W. Hollister, J.L. Ebersole, J.L. Lake, J.R. Serbst, J. James, M.G. Bennett, J.R. Brooks, C.T. Nietch, N.J. Smucker, J.E. Flotemersch, L.C. Alexander, and J.E. Compton (2018). “Performance of national maps of watershed integrity at watershed scales,” Water, 10(5), 604.
Thornbrugh, D.J., S.G. Leibowitz, R.A. Hill, M.H. Weber, Z.C. Johnson, A.R. Olsen, J.E. Flotemersch, J.L. Stoddard, and D.V. Peck (2018). “Mapping watershed integrity for the conterminous United States,” Ecol. Ind., 85, 1133-1148.
Johnson, Z.C., J.J. Warwick, and R. Schumer (2015). “A numerical investigation of the potential impact of stream restoration on in-stream N removal,” Ecological Engineering 83, 96-107.
Johnson, Z.C., J.J. Warwick, and R. Schumer (2015). “Nitrogen retention in the main channel and two transient storage zones during nutrient addition experiments,” Limnology and Oceanography 60, 57-77.
Johnson, Z.C., J.J. Warwick, and R. Schumer (2014). “Factors affecting hyporheic and surface transient storage in a western U.S. river,” J. Hydrology 510, 325-339.
Booth, E.C., B.G. Berger, Z.C. Johnson, T.M. Ta, L.R. Weisel, D.J. Ulness (2006). "Analysis of Raman-enhanced nondegenerate four-wave mixing with factorized time correlator diagrams," J. Opt. Soc. Am. B 23, 885-892.
**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
Filter Total Items: 15
Long-term monotonic trends in annual groundwater metrics in the United States through 2020 (ver. 4.0, May 2025) Long-term monotonic trends in annual groundwater metrics in the United States through 2020 (ver. 4.0, May 2025)
The U.S. Geological Survey (USGS) Water Resources Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand by delivering routine assessments of water supply and demand. A key part of these national assessments is identifying long-term trends in water availability, including groundwater and surface...
Long-term water-quality trends for rivers and streams within the contiguous United States using Weighted Regressions on Time, Discharge, and Season (WRTDS) (ver. 1.1, March 2025) Long-term water-quality trends for rivers and streams within the contiguous United States using Weighted Regressions on Time, Discharge, and Season (WRTDS) (ver. 1.1, March 2025)
The U.S. Geological Survey (USGS) Water Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand for water need by delivering routine assessments of water supply and demand. It is also improving understanding of the natural and human factors affecting the balance between supply and demand. A key...
Long-term monotonic trends in annual and monthly streamflow metrics at streamgages in the United States (ver. 2.0, October 2024) Long-term monotonic trends in annual and monthly streamflow metrics at streamgages in the United States (ver. 2.0, October 2024)
The U.S. Geological Survey (USGS) Water Resources Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand for water need by delivering routine assessments of water supply and demand and an understanding of the natural and human factors affecting the balance between supply and demand. A key part of...
Long-term monotonic trends in annual and monthly stream temperature metrics at multi-source monitoring locations in the United States (ver. 2.0, June 2025) Long-term monotonic trends in annual and monthly stream temperature metrics at multi-source monitoring locations in the United States (ver. 2.0, June 2025)
The U.S. Geological Survey (USGS) Water Resources Mission Area (WMA) is working to address a need to understand where the Nation is experiencing water shortages or surpluses relative to the demand for water need by delivering routine assessments of water supply and demand and an understanding of the natural and human factors affecting the balance between supply and demand. A key part of...
Passive seismic data collected along headwater stream corridors in Shenandoah National Park in 2016 - 2020 Passive seismic data collected along headwater stream corridors in Shenandoah National Park in 2016 - 2020
In July 2016, July 2019, and March 2020, 318 seismic recordings were acquired at locations within Shenandoah National Park, Virginia, using MOHO Tromino Model TEP-3C three-component seismometers to assess depth to bedrock using the HVSR method. This method requires a measurement of estimate of shear wave velocity, which depends on the regolith sediment composition and density, for the...
Spatial patterns of dewatering within watersheds of Shenandoah National Park, Virginia 2016 - 2021 (ver. 2.0, December 2021) Spatial patterns of dewatering within watersheds of Shenandoah National Park, Virginia 2016 - 2021 (ver. 2.0, December 2021)
These data describe longitudinal (upstream to downstream) patterns of dewatering during summer baseflow (July-September) conditions in nine watersheds in Shenandoah National park. In July-August of 2016 all nine watersheds (Jeremy's Run, Hazel River, Piney River, Hughes River, Staunton River, Whiteoak Canyon Run, Paine Run, Meadow Run, and Big Run) were evaluated for dewatering. In...
Filter Total Items: 19
Closing the gap between science and management of cold-water refuges in rivers and streams Closing the gap between science and management of cold-water refuges in rivers and streams
Human activities and climate change threaten coldwater organisms in freshwater ecosystems by causing rivers and streams to warm, increasing the intensity and frequency of warm temperature events, and reducing thermal heterogeneity. Cold-water refuges are discrete patches of relatively cool water that are used by coldwater organisms for thermal relief and short-term survival. Globally...
Authors
Francine H. Mejia, Valerie Ouellet, Martin A. Briggs, Stephanie M. Carlson, Rose Casas-Mulet, Mollie Chapman, Matthias J. Collins, Stephen J. Dugdale, Joseph L. Ebersole, Danielle M. Frechette, Aimee H. Fullerton, Carol-Anne Gillis, Zachary Johnson, Christa Kelleher, Barret L. Kurylyk, Rebecca Lave, Benjamin Letcher, Knut M. Myrvold, Tracie-Lynn Nadeau, Helen Neville, Herve Piégay, Kathryn E. Smith, Diego Tonolla, Christian E. Torgersen
Integrated water resources trend assessments: State of the science, challenges, and opportunities for advancement Integrated water resources trend assessments: State of the science, challenges, and opportunities for advancement
Water is vital to human life and healthy ecosystems. Here we outline the current state of national-scale water resources trend assessments, identify key gaps, and suggest advancements to better address critical issues related to changes in water resources that may threaten human development or the environment. Questions like, “Do we have less suitable drinking water now than we had 20...
Authors
Sarah M. Stackpoole, Gretchen P. Oelsner, Edward G. Stets, Jory Seth Hecht, Zachary Johnson, Anthony J. Tesoriero, Michelle A. Walvoord, Jeffrey G. Chanat, Krista A. Dunne, Phillip J. Goodling, Bruce D. Lindsey, Michael R. Meador, Sarah A. Spaulding
Paired Air and Stream Temperature Analysis (PASTA) to evaluate groundwater influence on streams Paired Air and Stream Temperature Analysis (PASTA) to evaluate groundwater influence on streams
Groundwater is critical for maintaining stream baseflow and thermal stability; however, the influence of groundwater on streamflow has been difficult to evaluate at broad spatial scales. Techniques such as baseflow separation necessitate streamflow records and do not directly indicate whether groundwater inflow may be sourced from more dynamic shallow flowpaths. We present a web tool...
Authors
Danielle K. Hare, Susanne A. Benz, Barret L. Kurylyk, Zachary Johnson, Neil C. Terry, Ashley M. Helton
Puget Sound Spatially Referenced Regression on Watershed Attributes (SPARROW) Puget Sound Spatially Referenced Regression on Watershed Attributes (SPARROW)
The United States Geological Survey (USGS) and the Washington State Department of Ecology (Ecology) are collaborating on the development of refined, seasonal load estimates of total nitrogen and total phosphorus within watersheds draining to Washington waters of the Salish Sea for the period 2005-2020. The modeling approach for this work is based on SPARROW (Spatially Referenced...
Authors
Cristiana Figueroa-Kaminsky, Jamie K. Wasielewski, Sheelagh McCarthy, Noah M. Schmadel, Daniel R. Wise, Zachary Johnson, Robert W. Black
Bedrock depth influences spatial patterns of summer baseflow, temperature and flow disconnection for mountainous headwater streams Bedrock depth influences spatial patterns of summer baseflow, temperature and flow disconnection for mountainous headwater streams
In mountain headwater streams, the quality and resilience of summer cold-water habitat is generally regulated by stream discharge, longitudinal stream channel connectivity and groundwater exchange. These critical hydrologic processes are thought to be influenced by the stream corridor bedrock contact depth (sediment thickness), a parameter often inferred from sparse hillslope borehole...
Authors
Martin A. Briggs, Phillip J. Goodling, Zachary Johnson, Karli M. Rogers, Nathaniel P. Hitt, Jennifer H. Fair, Craig D. Snyder
Continental-scale analysis of shallow and deep groundwater contributions to streams Continental-scale analysis of shallow and deep groundwater contributions to streams
Groundwater discharge generates streamflow and influences stream thermal regimes. However, the water quality and thermal buffering capacity of groundwater depends on the aquifer source-depth. Here, we pair multi-year air and stream temperature signals to categorize 1729 sites across the continental United States as having major dam influence, shallow or deep groundwater signatures, or...
Authors
D. Hare, A. M. Helton, Zachary C. Johnson, John W. Lane, Martin A. Briggs
Non-USGS Publications**
Johnson, Z.C., B.G. Johnson, M.A. Briggs, W.D. Devine, C.D. Snyder, N.P. Hitt, D.K. Hare, and T.V. Minkova (2020). “Paired air-water annual temperature patterns reveal hydrogeological controls on stream thermal regimes at watershed to continental scales”, J. Hydrology, 587, 124929.
Aho, K., J. Flotemersch, R. Hill, Z.C. Johnson, S.G. Leibowitz, and M. Weber (2020). “Adapting the Index of Watershed Integrity for watershed managers in the Western Balkans Region”, Environmental Management, 65, 602-617.
Johnson, Z.C., S.G. Leibowitz, and R.A. Hill (2019). “Revising the national maps of watershed integrity,” Sci. Total Environ., 651(2), 2615-2630.
Kuhn, A., S.G. Leibowitz, Z.C. Johnson, J. Lin, J.A. Massie, J.W. Hollister, J.L. Ebersole, J.L. Lake, J.R. Serbst, J. James, M.G. Bennett, J.R. Brooks, C.T. Nietch, N.J. Smucker, J.E. Flotemersch, L.C. Alexander, and J.E. Compton (2018). “Performance of national maps of watershed integrity at watershed scales,” Water, 10(5), 604.
Thornbrugh, D.J., S.G. Leibowitz, R.A. Hill, M.H. Weber, Z.C. Johnson, A.R. Olsen, J.E. Flotemersch, J.L. Stoddard, and D.V. Peck (2018). “Mapping watershed integrity for the conterminous United States,” Ecol. Ind., 85, 1133-1148.
Johnson, Z.C., J.J. Warwick, and R. Schumer (2015). “A numerical investigation of the potential impact of stream restoration on in-stream N removal,” Ecological Engineering 83, 96-107.
Johnson, Z.C., J.J. Warwick, and R. Schumer (2015). “Nitrogen retention in the main channel and two transient storage zones during nutrient addition experiments,” Limnology and Oceanography 60, 57-77.
Johnson, Z.C., J.J. Warwick, and R. Schumer (2014). “Factors affecting hyporheic and surface transient storage in a western U.S. river,” J. Hydrology 510, 325-339.
Booth, E.C., B.G. Berger, Z.C. Johnson, T.M. Ta, L.R. Weisel, D.J. Ulness (2006). "Analysis of Raman-enhanced nondegenerate four-wave mixing with factorized time correlator diagrams," J. Opt. Soc. Am. B 23, 885-892.
**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.