Assessing the impacts of mining on the Transboundary Koocanusa Reservoir
In 2019, the USGS began a water-quality monitoring program in Lake Koocanusa (also known as Koocanusa Reservoir) and at a site on the Kootenai River downstream of Libby Dam to provide high-frequency water-quality data for Federal, State, Provincial, and Tribal entities in the United States and Canada.
Stay up-to-date with our latest publications

Objectives of this study are to
- Collect water-quality samples from multiple depths,
- Collect continuous vertical profile data to understand limnological processes contributing to variations in selenium concentrations, and
- Collect time-series samples to compare to an established baseline dataset of selenium concentrations throughout the reservoir.
Monitoring water quality (and fish populations) in Lake Koocanusa and the Kootenai River has been a collaborative effort since at least 1967, when the United States Army Corps of Engineers (USACE) and the USGS began collecting water samples (Easthouse, 2013) to better understand the relation between Libby Dam operations on the reservoir and downstream effects on the Kootenai River. Monitoring and research by these and other agencies have increased recently because of concerns of a potential increased selenium concentrations in the basin, and a need to better understand the biogeochemical dynamics and ecological effects of selenium in the basin (Presser and Naftz, 2020).
Water-quality data collection in the center of Lake Koocanusa requires a specialized platform to house sampling equipment, sensors, and electronics that transmit data to the internet in real-time during the sampling season.

Evidence of selenium transport from Elk River Valley, Canada to the Columbia River
Monitoring Mining Effects in the Kootenai River Watershed
Growth of coal mining operations in the Elk River Valley linked to increasing transport of selenium, nitrate, and sulfate into Lake Koocanusa
Developing CE-QUAL-W2 Models of the Kootenai River and Koocanusa Reservoir, Montana and Idaho
Data releases associated with the project
Lake Koocanusa Water Quality Profiles for 2019 through 2024 Lake Koocanusa Water Quality Profiles for 2019 through 2024
Laboratory analyses for fish tissue samples from Lake Koocanusa and Kootenai River Basin, Montana, 2022 (ver. 2.0, May 2025) Laboratory analyses for fish tissue samples from Lake Koocanusa and Kootenai River Basin, Montana, 2022 (ver. 2.0, May 2025)
Fish Tissue Analysis Results, Koocanusa Reservoir, Montana, 2021 Fish Tissue Analysis Results, Koocanusa Reservoir, Montana, 2021
Input Files and WRTDS Model Output for the two major tributaries of Lake Koocanusa Input Files and WRTDS Model Output for the two major tributaries of Lake Koocanusa
Results of Ecosystem Scale Selenium Modeling in Support of Site-Specific Guidelines Development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada, 2020 Results of Ecosystem Scale Selenium Modeling in Support of Site-Specific Guidelines Development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada, 2020
Selenium concentrations in food webs of Lake Koocanusa in the vicinity of Libby Dam (MT) and the Elk River (BC) as the basis for applying ecosystem-scale modeling, 2008-2018 Selenium concentrations in food webs of Lake Koocanusa in the vicinity of Libby Dam (MT) and the Elk River (BC) as the basis for applying ecosystem-scale modeling, 2008-2018
USGS Measurements of Dissolved and Suspended Particulate Material Selenium in Lake Koocanusa in the Vicinity of Libby Dam (MT), 2015-2017 (update) USGS Measurements of Dissolved and Suspended Particulate Material Selenium in Lake Koocanusa in the Vicinity of Libby Dam (MT), 2015-2017 (update)
USGS Measurements of Dissolved and Particulate Material Selenium in Lake Koocanusa in the vicinity of Libby Dam (MT), 2015-2016 USGS Measurements of Dissolved and Particulate Material Selenium in Lake Koocanusa in the vicinity of Libby Dam (MT), 2015-2016
Evidence of Long-Range Transport of Selenium Downstream of Coal Mining Operations in the Elk River Valley, Canada
Evidence of long-range transport of selenium downstream of coal mining operations in the Elk River Valley, Canada Evidence of long-range transport of selenium downstream of coal mining operations in the Elk River Valley, Canada
Growth of coal mining operations in the Elk River Valley (Canada) linked to increasing solute transport of Se, NO3-, and SO42- into the transboundary Koocanusa Reservoir (USA-Canada) Growth of coal mining operations in the Elk River Valley (Canada) linked to increasing solute transport of Se, NO3-, and SO42- into the transboundary Koocanusa Reservoir (USA-Canada)
Sampling and analysis plan for the Koocanusa Reservoir and upper Kootenai River, Montana, water-quality monitoring program, 2021 Sampling and analysis plan for the Koocanusa Reservoir and upper Kootenai River, Montana, water-quality monitoring program, 2021
Selenium in the Kootenai River Basin, Montana and Idaho, United States, and British Columbia, Canada Selenium in the Kootenai River Basin, Montana and Idaho, United States, and British Columbia, Canada
Understanding and documenting the scientific basis of selenium ecological protection in support of site-specific guidelines development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada Understanding and documenting the scientific basis of selenium ecological protection in support of site-specific guidelines development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada
Conceptual modeling framework to support development of site-specific selenium criteria for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada Conceptual modeling framework to support development of site-specific selenium criteria for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada
Annual Nutrient Loadings, Primary Productivity, and Trophic State of Lake Koocanusa, Montana and British Columbia, 1972-80 Annual Nutrient Loadings, Primary Productivity, and Trophic State of Lake Koocanusa, Montana and British Columbia, 1972-80
Transboundary Watersheds Geonarrative Transboundary Watersheds Geonarrative
Below are partners associated with this project.
In 2019, the USGS began a water-quality monitoring program in Lake Koocanusa (also known as Koocanusa Reservoir) and at a site on the Kootenai River downstream of Libby Dam to provide high-frequency water-quality data for Federal, State, Provincial, and Tribal entities in the United States and Canada.
Stay up-to-date with our latest publications

Objectives of this study are to
- Collect water-quality samples from multiple depths,
- Collect continuous vertical profile data to understand limnological processes contributing to variations in selenium concentrations, and
- Collect time-series samples to compare to an established baseline dataset of selenium concentrations throughout the reservoir.
Monitoring water quality (and fish populations) in Lake Koocanusa and the Kootenai River has been a collaborative effort since at least 1967, when the United States Army Corps of Engineers (USACE) and the USGS began collecting water samples (Easthouse, 2013) to better understand the relation between Libby Dam operations on the reservoir and downstream effects on the Kootenai River. Monitoring and research by these and other agencies have increased recently because of concerns of a potential increased selenium concentrations in the basin, and a need to better understand the biogeochemical dynamics and ecological effects of selenium in the basin (Presser and Naftz, 2020).
Water-quality data collection in the center of Lake Koocanusa requires a specialized platform to house sampling equipment, sensors, and electronics that transmit data to the internet in real-time during the sampling season.

Evidence of selenium transport from Elk River Valley, Canada to the Columbia River
Monitoring Mining Effects in the Kootenai River Watershed
Growth of coal mining operations in the Elk River Valley linked to increasing transport of selenium, nitrate, and sulfate into Lake Koocanusa
Developing CE-QUAL-W2 Models of the Kootenai River and Koocanusa Reservoir, Montana and Idaho
Data releases associated with the project
Lake Koocanusa Water Quality Profiles for 2019 through 2024 Lake Koocanusa Water Quality Profiles for 2019 through 2024
Laboratory analyses for fish tissue samples from Lake Koocanusa and Kootenai River Basin, Montana, 2022 (ver. 2.0, May 2025) Laboratory analyses for fish tissue samples from Lake Koocanusa and Kootenai River Basin, Montana, 2022 (ver. 2.0, May 2025)
Fish Tissue Analysis Results, Koocanusa Reservoir, Montana, 2021 Fish Tissue Analysis Results, Koocanusa Reservoir, Montana, 2021
Input Files and WRTDS Model Output for the two major tributaries of Lake Koocanusa Input Files and WRTDS Model Output for the two major tributaries of Lake Koocanusa
Results of Ecosystem Scale Selenium Modeling in Support of Site-Specific Guidelines Development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada, 2020 Results of Ecosystem Scale Selenium Modeling in Support of Site-Specific Guidelines Development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada, 2020
Selenium concentrations in food webs of Lake Koocanusa in the vicinity of Libby Dam (MT) and the Elk River (BC) as the basis for applying ecosystem-scale modeling, 2008-2018 Selenium concentrations in food webs of Lake Koocanusa in the vicinity of Libby Dam (MT) and the Elk River (BC) as the basis for applying ecosystem-scale modeling, 2008-2018
USGS Measurements of Dissolved and Suspended Particulate Material Selenium in Lake Koocanusa in the Vicinity of Libby Dam (MT), 2015-2017 (update) USGS Measurements of Dissolved and Suspended Particulate Material Selenium in Lake Koocanusa in the Vicinity of Libby Dam (MT), 2015-2017 (update)
USGS Measurements of Dissolved and Particulate Material Selenium in Lake Koocanusa in the vicinity of Libby Dam (MT), 2015-2016 USGS Measurements of Dissolved and Particulate Material Selenium in Lake Koocanusa in the vicinity of Libby Dam (MT), 2015-2016
Evidence of Long-Range Transport of Selenium Downstream of Coal Mining Operations in the Elk River Valley, Canada
Evidence of long-range transport of selenium downstream of coal mining operations in the Elk River Valley, Canada Evidence of long-range transport of selenium downstream of coal mining operations in the Elk River Valley, Canada
Growth of coal mining operations in the Elk River Valley (Canada) linked to increasing solute transport of Se, NO3-, and SO42- into the transboundary Koocanusa Reservoir (USA-Canada) Growth of coal mining operations in the Elk River Valley (Canada) linked to increasing solute transport of Se, NO3-, and SO42- into the transboundary Koocanusa Reservoir (USA-Canada)
Sampling and analysis plan for the Koocanusa Reservoir and upper Kootenai River, Montana, water-quality monitoring program, 2021 Sampling and analysis plan for the Koocanusa Reservoir and upper Kootenai River, Montana, water-quality monitoring program, 2021
Selenium in the Kootenai River Basin, Montana and Idaho, United States, and British Columbia, Canada Selenium in the Kootenai River Basin, Montana and Idaho, United States, and British Columbia, Canada
Understanding and documenting the scientific basis of selenium ecological protection in support of site-specific guidelines development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada Understanding and documenting the scientific basis of selenium ecological protection in support of site-specific guidelines development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada
Conceptual modeling framework to support development of site-specific selenium criteria for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada Conceptual modeling framework to support development of site-specific selenium criteria for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada
Annual Nutrient Loadings, Primary Productivity, and Trophic State of Lake Koocanusa, Montana and British Columbia, 1972-80 Annual Nutrient Loadings, Primary Productivity, and Trophic State of Lake Koocanusa, Montana and British Columbia, 1972-80
Transboundary Watersheds Geonarrative Transboundary Watersheds Geonarrative
Below are partners associated with this project.