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, climate change and other 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
Puget Sound, WA Nutrient SPARROW Model
The Issue: Puget Sound watershed nutrient loads are known to have an impact on marine water quality along with wastewater treatment plants discharging to Puget Sound. To effectively reduce and control nutrient loads to the Sound, the Washington State Department of Ecology needs a regional watershed model that fits within their Puget Sound Nutrient Source Reduction Project’s management framework...
Stream heat budget model input and scripts for simulating groundwater and thermal equilibrium controls on annual paired air-water temperature signal transport in headwater streams
We investigated the relative importance of groundwater (GW) and other local heat budget processes on downstream annual stream temperature signal characteristics using deterministic heat budget model (HFLUX) scenarios within an idealized stream reach representative of mountainous forested conditions. The purpose of this data release is to provide additional supplemental information for a published
Long-term monotonic trends in annual groundwater metrics in the United States through 2020
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 water quant
Long-term water-quality trends for rivers and streams within the contiguous United States using Weighted Regressions on Time, Discharge, and Season (WRTDS)
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 part of these
Long-term monotonic trends in annual and monthly streamflow metrics at streamgages in the United States
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 these nati
Long-term monotonic trends in annual and monthly stream temperature metrics at multi-source monitoring locations in the United States
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 the Integr
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 conversion o
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 September of 20
Seismic data for study of shallow mountain bedrock limits seepage-based headwater climate refugia, Shenandoah National Park, Virginia
A combination of long-term daily temperature records and depth to bedrock measurements were used to parametrize one-dimensional models of shallow aquifer vertical heat transport in Shenandoah National Park, VA, USA. Depth to bedrock can directly influence shallow aquifer flow and thermal sensitivity, but is typically ill-defined along the stream corridor in steep mountain catchments. We employed r
Temperature data for study of shallow mountain bedrock limits seepage-based headwater climate refugia, Shenandoah National Park, Virginia
A combination of long-term daily temperature records and depth to bedrock measurements were used to parameterize one-dimensional models of shallow aquifer vertical heat transport in Shenandoah National Park, VA, USA. Spatially discontinuous roving water surface and bank temperatures surveys were performed with a handheld thermal infrared camera in September and December 2015 along the main channel
Air-water temperature data for the study of groundwater influence on stream thermal regimes in Shenandoah National Park, Virginia (ver. 2.0, May 3, 2018)
USGS Leetown Science Center scientists collected hourly air and water temperature data at 79 site locations within nine watersheds in Shenandoah National Park, Virginia over four water years (2012-2015). Data were collected using HOBO Pro V2 thermographs (accuracy = 0.2 degrees Celsius, drift = less than 0.1 degrees Celsius per year per year).
Opportunities and challenges for precipitation forcing data in post-wildfire hydrologic modeling applications
The frequency and extent of wildfires have increased in recent decades with immediate and cascading effects on water availability in many regions of the world. Precipitation is used as primary input to hydrologic models and is a critical driver of post-wildfire hydrologic hazards including debris flows, flash floods, water-quality effects, and reservoir sedimentation. These models are valuable too
Authors
Trevor Fuess Partridge, Zachary Johnson, Rachel Sleeter, Sharon L. Qi, Michelle A. Walvoord, Sheila F. Murphy, Cara L. Peterman-Phipps, Brian A. Ebel
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, cohesive man
Authors
Francine H. Mejia, Valerie Ouellet, Martin 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
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 years ago?”
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 Meador, Sarah Spaulding
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 application P
Authors
Danielle K. Hare, Susanne A. Benz, Barret L. Kurylyk, Zachary Johnson, Neil Terry, Ashley M. Helton
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 information,
Authors
Martin Briggs, Phillip J. Goodling, Zachary Johnson, Karli M. Rogers, Nathaniel P. Hitt, Jennifer Burlingame Hoyle Fair, Craig D. Snyder
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 lack of pron
Authors
D. Hare, A. M. Helton, Zachary C. Johnson, John W. Lane, Martin A. Briggs
Heed the data gap: Guidelines for using incomplete datasets in annual stream temperature analyses
Stream temperature data are useful for deciphering watershed processes important for aquatic ecosystems. Accurately extracting signal trends from stream temperature is essential for predicting responses of environmental and ecological indicators to change. Missing data periods are common for various reasons, and pose a challenge for scientists using temperature signal analysis to support stream re
Authors
Zachary C. Johnson, Brittany G. Johnson, Martin A. Briggs, Craig D. Snyder, Nathaniel P. Hitt, Warren Devine
Inferring watershed hydraulics and cold-water habitat persistence using multi-year air and stream temperature signals
Streams strongly influenced by groundwater discharge may serve as “climate refugia” for sensitive species in regions of increasingly marginal thermal conditions. The main goal of this study is to develop paired air and stream water annual temperature signal analysis techniques to elucidate the relative groundwater contribution to stream water and the effective groundwater flowpath depth. Groundwat
Authors
Martin A. Briggs, Zachary C. Johnson, Craig D. Snyder, Nathaniel P. Hitt, Barret L. Kurylyk, Laura K. Lautz, Dylan J. Irvine, Stephen T. Hurley, John W. Lane
Forecasting stream habitat and Brook Trout responses to climate change in Catoctin Mountain Park
Anticipating and mitigating the effects of climate change is a fundamental challenge for natural resource conservation. In this report, we respond to research needs identified by Catoctin Mountain Park (CATO) for native Brook Trout (Salvelinus fontinalis) conservation and management as part of the US Geological Survey (USGS) Natural Resources Preservation Program in FY15-16. We addressed three ove
Authors
Nathaniel P. Hitt, Craig D. Snyder, Erin Snook, Zachary Johnson, Matthew Morgan
Landform features and seasonal precipitation predict shallow groundwater influence on temperature in headwater streams
Headwater stream responses to climate change will depend in part on groundwater‐surface water exchanges. We used linear modeling techniques to partition likely effects of shallow groundwater seepage and air temperature on stream temperatures for 79 sites in nine focal watersheds using hourly air and water temperature measurements collected during summer months from 2012 to 2015 in Shenandoah Natio
Authors
Zachary C. Johnson, Craig D. Snyder, Nathaniel P. Hitt
Shallow bedrock limits groundwater seepage-based headwater climate refugia
Groundwater/surface-water exchanges in streams are inexorably linked to adjacent aquifer dynamics. As surface-water temperatures continue to increase with climate warming, refugia created by groundwater connectivity is expected to enable cold water fish species to survive. The shallow alluvial aquifers that source groundwater seepage to headwater streams, however, may also be sensitive to seasonal
Authors
Martin A. Briggs, John W. Lane, Craig D. Snyder, Eric A. White, Zachary Johnson, David L. Nelms, Nathaniel P. Hitt
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
- Science
Puget Sound, WA Nutrient SPARROW Model
The Issue: Puget Sound watershed nutrient loads are known to have an impact on marine water quality along with wastewater treatment plants discharging to Puget Sound. To effectively reduce and control nutrient loads to the Sound, the Washington State Department of Ecology needs a regional watershed model that fits within their Puget Sound Nutrient Source Reduction Project’s management framework... - Data
Stream heat budget model input and scripts for simulating groundwater and thermal equilibrium controls on annual paired air-water temperature signal transport in headwater streams
We investigated the relative importance of groundwater (GW) and other local heat budget processes on downstream annual stream temperature signal characteristics using deterministic heat budget model (HFLUX) scenarios within an idealized stream reach representative of mountainous forested conditions. The purpose of this data release is to provide additional supplemental information for a publishedLong-term monotonic trends in annual groundwater metrics in the United States through 2020
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 water quantLong-term water-quality trends for rivers and streams within the contiguous United States using Weighted Regressions on Time, Discharge, and Season (WRTDS)
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 part of theseLong-term monotonic trends in annual and monthly streamflow metrics at streamgages in the United States
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 these natiLong-term monotonic trends in annual and monthly stream temperature metrics at multi-source monitoring locations in the United States
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 the IntegrPassive 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 conversion oSpatial 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 September of 20Seismic data for study of shallow mountain bedrock limits seepage-based headwater climate refugia, Shenandoah National Park, Virginia
A combination of long-term daily temperature records and depth to bedrock measurements were used to parametrize one-dimensional models of shallow aquifer vertical heat transport in Shenandoah National Park, VA, USA. Depth to bedrock can directly influence shallow aquifer flow and thermal sensitivity, but is typically ill-defined along the stream corridor in steep mountain catchments. We employed rTemperature data for study of shallow mountain bedrock limits seepage-based headwater climate refugia, Shenandoah National Park, Virginia
A combination of long-term daily temperature records and depth to bedrock measurements were used to parameterize one-dimensional models of shallow aquifer vertical heat transport in Shenandoah National Park, VA, USA. Spatially discontinuous roving water surface and bank temperatures surveys were performed with a handheld thermal infrared camera in September and December 2015 along the main channelAir-water temperature data for the study of groundwater influence on stream thermal regimes in Shenandoah National Park, Virginia (ver. 2.0, May 3, 2018)
USGS Leetown Science Center scientists collected hourly air and water temperature data at 79 site locations within nine watersheds in Shenandoah National Park, Virginia over four water years (2012-2015). Data were collected using HOBO Pro V2 thermographs (accuracy = 0.2 degrees Celsius, drift = less than 0.1 degrees Celsius per year per year). - Publications
Opportunities and challenges for precipitation forcing data in post-wildfire hydrologic modeling applications
The frequency and extent of wildfires have increased in recent decades with immediate and cascading effects on water availability in many regions of the world. Precipitation is used as primary input to hydrologic models and is a critical driver of post-wildfire hydrologic hazards including debris flows, flash floods, water-quality effects, and reservoir sedimentation. These models are valuable tooAuthorsTrevor Fuess Partridge, Zachary Johnson, Rachel Sleeter, Sharon L. Qi, Michelle A. Walvoord, Sheila F. Murphy, Cara L. Peterman-Phipps, Brian A. EbelClosing 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, cohesive manAuthorsFrancine H. Mejia, Valerie Ouellet, Martin 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. TorgersenIntegrated 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 years ago?”AuthorsSarah 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 Meador, Sarah SpauldingPaired 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 application PAuthorsDanielle K. Hare, Susanne A. Benz, Barret L. Kurylyk, Zachary Johnson, Neil Terry, Ashley M. HeltonBedrock 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 information,AuthorsMartin Briggs, Phillip J. Goodling, Zachary Johnson, Karli M. Rogers, Nathaniel P. Hitt, Jennifer Burlingame Hoyle Fair, Craig D. SnyderContinental-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 lack of pron
AuthorsD. Hare, A. M. Helton, Zachary C. Johnson, John W. Lane, Martin A. BriggsHeed the data gap: Guidelines for using incomplete datasets in annual stream temperature analyses
Stream temperature data are useful for deciphering watershed processes important for aquatic ecosystems. Accurately extracting signal trends from stream temperature is essential for predicting responses of environmental and ecological indicators to change. Missing data periods are common for various reasons, and pose a challenge for scientists using temperature signal analysis to support stream reAuthorsZachary C. Johnson, Brittany G. Johnson, Martin A. Briggs, Craig D. Snyder, Nathaniel P. Hitt, Warren DevineInferring watershed hydraulics and cold-water habitat persistence using multi-year air and stream temperature signals
Streams strongly influenced by groundwater discharge may serve as “climate refugia” for sensitive species in regions of increasingly marginal thermal conditions. The main goal of this study is to develop paired air and stream water annual temperature signal analysis techniques to elucidate the relative groundwater contribution to stream water and the effective groundwater flowpath depth. GroundwatAuthorsMartin A. Briggs, Zachary C. Johnson, Craig D. Snyder, Nathaniel P. Hitt, Barret L. Kurylyk, Laura K. Lautz, Dylan J. Irvine, Stephen T. Hurley, John W. LaneForecasting stream habitat and Brook Trout responses to climate change in Catoctin Mountain Park
Anticipating and mitigating the effects of climate change is a fundamental challenge for natural resource conservation. In this report, we respond to research needs identified by Catoctin Mountain Park (CATO) for native Brook Trout (Salvelinus fontinalis) conservation and management as part of the US Geological Survey (USGS) Natural Resources Preservation Program in FY15-16. We addressed three oveAuthorsNathaniel P. Hitt, Craig D. Snyder, Erin Snook, Zachary Johnson, Matthew MorganLandform features and seasonal precipitation predict shallow groundwater influence on temperature in headwater streams
Headwater stream responses to climate change will depend in part on groundwater‐surface water exchanges. We used linear modeling techniques to partition likely effects of shallow groundwater seepage and air temperature on stream temperatures for 79 sites in nine focal watersheds using hourly air and water temperature measurements collected during summer months from 2012 to 2015 in Shenandoah NatioAuthorsZachary C. Johnson, Craig D. Snyder, Nathaniel P. HittShallow bedrock limits groundwater seepage-based headwater climate refugia
Groundwater/surface-water exchanges in streams are inexorably linked to adjacent aquifer dynamics. As surface-water temperatures continue to increase with climate warming, refugia created by groundwater connectivity is expected to enable cold water fish species to survive. The shallow alluvial aquifers that source groundwater seepage to headwater streams, however, may also be sensitive to seasonalAuthorsMartin A. Briggs, John W. Lane, Craig D. Snyder, Eric A. White, Zachary Johnson, David L. Nelms, Nathaniel P. HittNon-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.