Patrick C Longley
Patrick is a Hydrologist with the USGS Colorado Water Science Center, Western Colorado Office, in Grand Junction, CO.
Patrick is interested in studying how snowpack dynamics and changing climate affect water availability and water quality at a variety of scales.
Professional Experience
Hydrologist, USGS-Colorado Water Science Center, Grand Junction, CO, 2022-present
Physical Scientist, USGS-Utah Water Science Center, Salt Lake City, UT, 2020-2022
Water Rights Specialist, Utah Division of Water Rights, Salt Lake City, UT, 2019-2020
Hydrologic Technician, National Park Service, Yosemite, CA, 2018
Research Assistant, Nevada Mountain Ecohydrology Lab, Reno, NV, 2015-2017
Education and Certifications
Masters of Science in Hydrology, the University of Nevada Reno, Reno, NV, 2017
Focus: Quantifying the effects of changing snowpack dynamics on hydrologic partitioning at multiple scalesBachelor of Science in Mathematics, Western Washington University, Bellingham, WA, 2014
Science and Products
Drought versus Aridification in the Colorado River Basin
The Colorado River Basin is no stranger to drought. However, not all droughts are the same. Drought refers to a temporary state where conditions eventually return to normal. Aridification is the transition to persistent above-average dry conditions that do not return to normal. It is important to know whether the current, prolonged millennium drought (2000-present) is actually the first stages of...
Input and output data used to assess the effects of climate on the temporal variability in streamflow and total dissolved solids loads in the Upper Colorado River Basin, water years 1986-2021 Input and output data used to assess the effects of climate on the temporal variability in streamflow and total dissolved solids loads in the Upper Colorado River Basin, water years 1986-2021
This data release contains the input and output used to assess the potential effect of climate on streamflow and salinity (measured as total dissolved solids [TDS]) yields across the Upper Colorado River Basin from water years 1986 to 2021. This analysis included estimation of the spatiotemporal variability in mean annual climatic variables (air temperature, snow water equivalent...
Long-term trends in annual, seasonal, and monthly streamflow metrics at streamgages in the Upper Colorado River Basin, 1981-2022 Long-term trends in annual, seasonal, and monthly streamflow metrics at streamgages in the Upper Colorado River Basin, 1981-2022
Identifying long-term trends in water availability, including surface water quantity, is a key part of the U.S. Geological Survey (USGS) Integrated Water Availability Assessments (IWAAs) mission. This data release includes input and output data used in Mann-Kendall trend analyses to characterize streamflow conditions at 124 USGS streamgages in the Upper Colorado River Basin for water...
Daily baseflow discharge and daily stream and baseflow total dissolved solids (TDS) loads for selected locations in the Upper Colorado River Basin for water years 1986 – 2020 Daily baseflow discharge and daily stream and baseflow total dissolved solids (TDS) loads for selected locations in the Upper Colorado River Basin for water years 1986 – 2020
This data release contains measured stream discharge and total dissolved solids (TDS) data and estimated values for daily stream TDS loads, daily baseflow discharge, and daily baseflow TDS loads for 205 locations in the Upper Colorado River Basin. The estimated values, which represent conditions between 10/1/1985 and 9/30/2020, were obtained using the Weighted Regressions on Time...
Daily baseflow specific conductance and daily baseflow discharge at selected sites within the Colorado River Basin for water years 1980-2022 Daily baseflow specific conductance and daily baseflow discharge at selected sites within the Colorado River Basin for water years 1980-2022
This data release contains two sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022). The estimates of daily baseflow discharge will be used as input...
Daily baseflow specific conductance, daily baseflow discharge, and seasonal baseflow discharge and baseflow dissolved solids loads at selected sites within the Colorado River Basin for water years 1980 – 2022 Daily baseflow specific conductance, daily baseflow discharge, and seasonal baseflow discharge and baseflow dissolved solids loads at selected sites within the Colorado River Basin for water years 1980 – 2022
This data release contains three sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 3) seasonal baseflow discharge and baseflow dissolved solids...
Erosion rates and salinity and selenium yields in a basin near Rangely, Colorado following the 2017 Dead Dog wildfire as modeled by WEPP and measured from UAV Erosion rates and salinity and selenium yields in a basin near Rangely, Colorado following the 2017 Dead Dog wildfire as modeled by WEPP and measured from UAV
This data release accompanies a U.S Geological Survey study that assessed sediment, salinity, and selenium yields following the Dead Dog wildfire in northwestern Colorado. The Dead Dog fire ignited on June 11, 2017, near Rangely, Colorado, and burned over 17,000 acres, including the B2 study area. Two methodologies were used to quantify erosion and associated salinity and sediment yields...
Digital hydrogeologic framework model of the Upper Colorado River Basin, western U.S. Digital hydrogeologic framework model of the Upper Colorado River Basin, western U.S.
This digital dataset was created as part of a U.S. Geological Survey hydrologic resource assessment and development of an integrated numerical hydrologic model of the hydrologic system of the Upper Colorado River Basin, an extensive region covering approximately 412,000 square kilometers in five states: Wyoming, Colorado, Utah, Arizona, and New Mexico. As part of this larger study, the...
Hydrogen and oxygen stable isotope mass balance evaluation of the National Water Model (v2.1) streamflow, runoff and groundwater flows Hydrogen and oxygen stable isotope mass balance evaluation of the National Water Model (v2.1) streamflow, runoff and groundwater flows
This data release contains the results of an isotopic mass balance approach to provide an estimate of the long-term average isotope ratios of NWM streamflow for the summer season (JJA) between 2000 and 2019 in the Western United States. The NWM-estimated long-term average isotope ratios are compared directly to 6426 stream stable isotope observations in 995 unique catchments. Quantified
SPARROW model inputs and simulated future baseflow for streams of the Upper Colorado River Basin SPARROW model inputs and simulated future baseflow for streams of the Upper Colorado River Basin
The U.S. Geological Survey's (USGS) SPAtially Referenced Regression On Watershed attributes (SPARROW) model was used to estimate baseflow changes from historical (1984 - 2012) to thirty-year periods centered around 2030, 2050, and 2080 under warm/wet, median, and hot/dry climatic conditions. SPARROW is a spatially explicit hybrid statistical and process-based model that estimates mean...
Dissolved-Selenium Concentrations and Loads in the Lower Gunnison River Basin, Colorado, as Part of the Selenium Management Program (ver. 5.0, September 2025) Dissolved-Selenium Concentrations and Loads in the Lower Gunnison River Basin, Colorado, as Part of the Selenium Management Program (ver. 5.0, September 2025)
The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation, completed a review of dissolved selenium data collected from the Selenium Management Program network during each water year (WY) in the lower Gunnison River Basin, in western Colorado. The data tables include dissolved-selenium concentrations, selected streamflow data, and computed loads as well as...
Effects of climate on temporal variability in streamflow and salinity in the Upper Colorado River Basin Effects of climate on temporal variability in streamflow and salinity in the Upper Colorado River Basin
Study RegionThe Upper Colorado River Basin, a critical water source for more than 40 million people in the western United States.Study FocusPotential decreasing streamflow and elevated salinity concentrations threaten this resource. Climate variability has a large and well-studied effect on streamflow in the basin; however, the effect on salinity loading is less understood. This study...
Authors
Natalie K. Day, Patrick C. Longley, Daniel Wise, Morgan C. McDonnell
Contributions of Great Salt Lake playa- and industrially-sourced priority pollutant metals in dust contribute to possible health hazards in the communities of northern Utah Contributions of Great Salt Lake playa- and industrially-sourced priority pollutant metals in dust contribute to possible health hazards in the communities of northern Utah
Communities and ecosystems of northern Utah, USA receive particulate pollution from anthropogenic activity and dust emissions from sources including the Great Salt Lake (“the Lake”) playa. In addition to affecting communities, anthropogenic pollution is delivered to the Lake's playa sediments, which are eroded during dust events. Yet, spatial variability in dust flux and composition and...
Authors
Annie L. Putman, Molly A. Blakowski, Destry N. DiViesti, Diego P. Fernandez, Morgan C. McDonnell, Patrick C. Longley, Daniel K. Jones
Wildland fire effects on sediment, salinity, and selenium yields in a basin underlain by Cretaceous marine shales near Rangely, Colorado Wildland fire effects on sediment, salinity, and selenium yields in a basin underlain by Cretaceous marine shales near Rangely, Colorado
Understanding and quantifying soil erosion from rangelands is a high priority for land managers, especially in areas underlain by Cretaceous Mancos Shale, which is a natural source of sediment, salinity, and selenium to surface waters in many areas of western Colorado and eastern Utah. The purpose of this report is to present the results of a U.S. Geological Survey study that assessed...
Authors
Natalie K. Day, Todd M. Preston, Patrick C. Longley
Isotopic evaluation of the National Water Model reveals missing agricultural irrigation contributions to streamflow across the western United States Isotopic evaluation of the National Water Model reveals missing agricultural irrigation contributions to streamflow across the western United States
The National Water Model (NWM) provides critical analyses and projections of streamflow that support water management decisions. However, the NWM performs poorly in lower-elevation rivers of the western United States (US). The accuracy of the NWM depends on the fidelity of the model inputs and the representation and calibration of model processes and water sources. To evaluate the NWM...
Authors
Annie L. Putman, Patrick C. Longley, Morgan C. McDonnell, James E. Reddy, Michelle P. Katoski, Olivia L. Miller, J. Renee Brooks
Assessing exposure of northern Utah communities to dust from the contaminated and dynamic Great Salt Lake playa Assessing exposure of northern Utah communities to dust from the contaminated and dynamic Great Salt Lake playa
No abstract available.
Authors
Annie L. Putman, Molly A. Blakowski, Morgan C. McDonnell, Destry N. DiViesti, Diego P. Fernandez, Patrick C. Longley, Daniel K. Jones
A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin
The Colorado River is a critical water resource in the southwestern United States, supplying drinking water for 40 million people in the region and water for irrigation of 2.2 million hectares of land. Extended drought in the Upper Colorado River Basin (UCOL) and the prospect of a warmer climate in the future pose water availability challenges for those charged with managing the river...
Authors
Fred D. Tillman, Natalie K. Day, Matthew P. Miller, Olivia L. Miller, Christine Rumsey, Daniel Wise, Patrick C. Longley, Morgan C. McDonnell
How will baseflow respond to climate change in the Upper Colorado River Basin? How will baseflow respond to climate change in the Upper Colorado River Basin?
Baseflow is critical to sustaining streamflow in the Upper Colorado River Basin. Therefore, effective water resources management requires estimates of baseflow response to climatic changes. This study provides the first estimates of projected baseflow changes from historical (1984 – 2012) to thirty-year periods centered around 2030, 2050, and 2080 under warm/wet, median, and hot/dry...
Authors
Olivia L. Miller, Matthew P. Miller, Patrick C. Longley, Jay R. Alder, Lindsay A. Bearup, Tom Pruitt, Daniel K. Jones, Annie L. Putman, Christine Rumsey, Tim S. McKinney
Non-USGS Publications**
Tillman, Fred D, Natalie K. Day, Matthew P. Miller, Olivia L. Miller, Christine A. Rumsey, Daniel R. Wise, Patrick C. Longley, and Morgan C. McDonnell. 2022. "A Review of Current Capabilities and Science Gaps in Water Supply Data, Modeling, and Trends for Water Availability Assessments in the Upper Colorado River Basin" Water 14, no. 23: 3813. https://doi.org/10.3390/w14233813
Olivia L. Miller; Matthew P. Miller; Patrick C. Longley; Jay R. Alder; Lindsay A. Bearup; Tom Pruitt; Daniel K. Jones; Annie L. Putman; Christine A. Rumsey; Tim McKinney. 2021. "How Will Baseflow Respond to Climate Change in the Upper Colorado River Basin?" Geophysical Research Letters, Volume 48, Issue 22. https://doi.org/10.1029/2021GL095085
**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
Drought versus Aridification in the Colorado River Basin
The Colorado River Basin is no stranger to drought. However, not all droughts are the same. Drought refers to a temporary state where conditions eventually return to normal. Aridification is the transition to persistent above-average dry conditions that do not return to normal. It is important to know whether the current, prolonged millennium drought (2000-present) is actually the first stages of...
Input and output data used to assess the effects of climate on the temporal variability in streamflow and total dissolved solids loads in the Upper Colorado River Basin, water years 1986-2021 Input and output data used to assess the effects of climate on the temporal variability in streamflow and total dissolved solids loads in the Upper Colorado River Basin, water years 1986-2021
This data release contains the input and output used to assess the potential effect of climate on streamflow and salinity (measured as total dissolved solids [TDS]) yields across the Upper Colorado River Basin from water years 1986 to 2021. This analysis included estimation of the spatiotemporal variability in mean annual climatic variables (air temperature, snow water equivalent...
Long-term trends in annual, seasonal, and monthly streamflow metrics at streamgages in the Upper Colorado River Basin, 1981-2022 Long-term trends in annual, seasonal, and monthly streamflow metrics at streamgages in the Upper Colorado River Basin, 1981-2022
Identifying long-term trends in water availability, including surface water quantity, is a key part of the U.S. Geological Survey (USGS) Integrated Water Availability Assessments (IWAAs) mission. This data release includes input and output data used in Mann-Kendall trend analyses to characterize streamflow conditions at 124 USGS streamgages in the Upper Colorado River Basin for water...
Daily baseflow discharge and daily stream and baseflow total dissolved solids (TDS) loads for selected locations in the Upper Colorado River Basin for water years 1986 – 2020 Daily baseflow discharge and daily stream and baseflow total dissolved solids (TDS) loads for selected locations in the Upper Colorado River Basin for water years 1986 – 2020
This data release contains measured stream discharge and total dissolved solids (TDS) data and estimated values for daily stream TDS loads, daily baseflow discharge, and daily baseflow TDS loads for 205 locations in the Upper Colorado River Basin. The estimated values, which represent conditions between 10/1/1985 and 9/30/2020, were obtained using the Weighted Regressions on Time...
Daily baseflow specific conductance and daily baseflow discharge at selected sites within the Colorado River Basin for water years 1980-2022 Daily baseflow specific conductance and daily baseflow discharge at selected sites within the Colorado River Basin for water years 1980-2022
This data release contains two sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022). The estimates of daily baseflow discharge will be used as input...
Daily baseflow specific conductance, daily baseflow discharge, and seasonal baseflow discharge and baseflow dissolved solids loads at selected sites within the Colorado River Basin for water years 1980 – 2022 Daily baseflow specific conductance, daily baseflow discharge, and seasonal baseflow discharge and baseflow dissolved solids loads at selected sites within the Colorado River Basin for water years 1980 – 2022
This data release contains three sets of estimated values at selected sites within the Colorado River Basin: 1) daily specific conductance at 143 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); 2) daily baseflow discharge at 100 sites in the Upper Basin and 3 sites in the Lower Basin (WY 1980-2022); and 3) seasonal baseflow discharge and baseflow dissolved solids...
Erosion rates and salinity and selenium yields in a basin near Rangely, Colorado following the 2017 Dead Dog wildfire as modeled by WEPP and measured from UAV Erosion rates and salinity and selenium yields in a basin near Rangely, Colorado following the 2017 Dead Dog wildfire as modeled by WEPP and measured from UAV
This data release accompanies a U.S Geological Survey study that assessed sediment, salinity, and selenium yields following the Dead Dog wildfire in northwestern Colorado. The Dead Dog fire ignited on June 11, 2017, near Rangely, Colorado, and burned over 17,000 acres, including the B2 study area. Two methodologies were used to quantify erosion and associated salinity and sediment yields...
Digital hydrogeologic framework model of the Upper Colorado River Basin, western U.S. Digital hydrogeologic framework model of the Upper Colorado River Basin, western U.S.
This digital dataset was created as part of a U.S. Geological Survey hydrologic resource assessment and development of an integrated numerical hydrologic model of the hydrologic system of the Upper Colorado River Basin, an extensive region covering approximately 412,000 square kilometers in five states: Wyoming, Colorado, Utah, Arizona, and New Mexico. As part of this larger study, the...
Hydrogen and oxygen stable isotope mass balance evaluation of the National Water Model (v2.1) streamflow, runoff and groundwater flows Hydrogen and oxygen stable isotope mass balance evaluation of the National Water Model (v2.1) streamflow, runoff and groundwater flows
This data release contains the results of an isotopic mass balance approach to provide an estimate of the long-term average isotope ratios of NWM streamflow for the summer season (JJA) between 2000 and 2019 in the Western United States. The NWM-estimated long-term average isotope ratios are compared directly to 6426 stream stable isotope observations in 995 unique catchments. Quantified
SPARROW model inputs and simulated future baseflow for streams of the Upper Colorado River Basin SPARROW model inputs and simulated future baseflow for streams of the Upper Colorado River Basin
The U.S. Geological Survey's (USGS) SPAtially Referenced Regression On Watershed attributes (SPARROW) model was used to estimate baseflow changes from historical (1984 - 2012) to thirty-year periods centered around 2030, 2050, and 2080 under warm/wet, median, and hot/dry climatic conditions. SPARROW is a spatially explicit hybrid statistical and process-based model that estimates mean...
Dissolved-Selenium Concentrations and Loads in the Lower Gunnison River Basin, Colorado, as Part of the Selenium Management Program (ver. 5.0, September 2025) Dissolved-Selenium Concentrations and Loads in the Lower Gunnison River Basin, Colorado, as Part of the Selenium Management Program (ver. 5.0, September 2025)
The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation, completed a review of dissolved selenium data collected from the Selenium Management Program network during each water year (WY) in the lower Gunnison River Basin, in western Colorado. The data tables include dissolved-selenium concentrations, selected streamflow data, and computed loads as well as...
Effects of climate on temporal variability in streamflow and salinity in the Upper Colorado River Basin Effects of climate on temporal variability in streamflow and salinity in the Upper Colorado River Basin
Study RegionThe Upper Colorado River Basin, a critical water source for more than 40 million people in the western United States.Study FocusPotential decreasing streamflow and elevated salinity concentrations threaten this resource. Climate variability has a large and well-studied effect on streamflow in the basin; however, the effect on salinity loading is less understood. This study...
Authors
Natalie K. Day, Patrick C. Longley, Daniel Wise, Morgan C. McDonnell
Contributions of Great Salt Lake playa- and industrially-sourced priority pollutant metals in dust contribute to possible health hazards in the communities of northern Utah Contributions of Great Salt Lake playa- and industrially-sourced priority pollutant metals in dust contribute to possible health hazards in the communities of northern Utah
Communities and ecosystems of northern Utah, USA receive particulate pollution from anthropogenic activity and dust emissions from sources including the Great Salt Lake (“the Lake”) playa. In addition to affecting communities, anthropogenic pollution is delivered to the Lake's playa sediments, which are eroded during dust events. Yet, spatial variability in dust flux and composition and...
Authors
Annie L. Putman, Molly A. Blakowski, Destry N. DiViesti, Diego P. Fernandez, Morgan C. McDonnell, Patrick C. Longley, Daniel K. Jones
Wildland fire effects on sediment, salinity, and selenium yields in a basin underlain by Cretaceous marine shales near Rangely, Colorado Wildland fire effects on sediment, salinity, and selenium yields in a basin underlain by Cretaceous marine shales near Rangely, Colorado
Understanding and quantifying soil erosion from rangelands is a high priority for land managers, especially in areas underlain by Cretaceous Mancos Shale, which is a natural source of sediment, salinity, and selenium to surface waters in many areas of western Colorado and eastern Utah. The purpose of this report is to present the results of a U.S. Geological Survey study that assessed...
Authors
Natalie K. Day, Todd M. Preston, Patrick C. Longley
Isotopic evaluation of the National Water Model reveals missing agricultural irrigation contributions to streamflow across the western United States Isotopic evaluation of the National Water Model reveals missing agricultural irrigation contributions to streamflow across the western United States
The National Water Model (NWM) provides critical analyses and projections of streamflow that support water management decisions. However, the NWM performs poorly in lower-elevation rivers of the western United States (US). The accuracy of the NWM depends on the fidelity of the model inputs and the representation and calibration of model processes and water sources. To evaluate the NWM...
Authors
Annie L. Putman, Patrick C. Longley, Morgan C. McDonnell, James E. Reddy, Michelle P. Katoski, Olivia L. Miller, J. Renee Brooks
Assessing exposure of northern Utah communities to dust from the contaminated and dynamic Great Salt Lake playa Assessing exposure of northern Utah communities to dust from the contaminated and dynamic Great Salt Lake playa
No abstract available.
Authors
Annie L. Putman, Molly A. Blakowski, Morgan C. McDonnell, Destry N. DiViesti, Diego P. Fernandez, Patrick C. Longley, Daniel K. Jones
A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin
The Colorado River is a critical water resource in the southwestern United States, supplying drinking water for 40 million people in the region and water for irrigation of 2.2 million hectares of land. Extended drought in the Upper Colorado River Basin (UCOL) and the prospect of a warmer climate in the future pose water availability challenges for those charged with managing the river...
Authors
Fred D. Tillman, Natalie K. Day, Matthew P. Miller, Olivia L. Miller, Christine Rumsey, Daniel Wise, Patrick C. Longley, Morgan C. McDonnell
How will baseflow respond to climate change in the Upper Colorado River Basin? How will baseflow respond to climate change in the Upper Colorado River Basin?
Baseflow is critical to sustaining streamflow in the Upper Colorado River Basin. Therefore, effective water resources management requires estimates of baseflow response to climatic changes. This study provides the first estimates of projected baseflow changes from historical (1984 – 2012) to thirty-year periods centered around 2030, 2050, and 2080 under warm/wet, median, and hot/dry...
Authors
Olivia L. Miller, Matthew P. Miller, Patrick C. Longley, Jay R. Alder, Lindsay A. Bearup, Tom Pruitt, Daniel K. Jones, Annie L. Putman, Christine Rumsey, Tim S. McKinney
Non-USGS Publications**
Tillman, Fred D, Natalie K. Day, Matthew P. Miller, Olivia L. Miller, Christine A. Rumsey, Daniel R. Wise, Patrick C. Longley, and Morgan C. McDonnell. 2022. "A Review of Current Capabilities and Science Gaps in Water Supply Data, Modeling, and Trends for Water Availability Assessments in the Upper Colorado River Basin" Water 14, no. 23: 3813. https://doi.org/10.3390/w14233813
Olivia L. Miller; Matthew P. Miller; Patrick C. Longley; Jay R. Alder; Lindsay A. Bearup; Tom Pruitt; Daniel K. Jones; Annie L. Putman; Christine A. Rumsey; Tim McKinney. 2021. "How Will Baseflow Respond to Climate Change in the Upper Colorado River Basin?" Geophysical Research Letters, Volume 48, Issue 22. https://doi.org/10.1029/2021GL095085
**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.