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EPA and partners release data and findings from Kootenai River sampling effort

Water quality and fish tissue results show elevated levels of selenium and nitrates associated with upstream sources

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Lisa McClain-Vanderpool (

HELENA, Mont. (Sept. 23, 2019) – Today, the U.S. Environmental Protection Agency (EPA), in cooperation with the U.S. Geological Survey (USGS), released the results of a water quality study indicating elevated levels of selenium in water and fish, and elevated nitrates in water, in the Kootenai River associated with upstream sources in Canada’s Elk Valley and Lake Koocanusa.

The study, part of a collaborative effort between federal, state and tribal agencies to assess the Kootenai River watershed, is based on water chemistry and fish tissue samples taken on the river in Montana and Idaho from immediately below Libby Dam to the Canadian border.  Data contributing to the study were collected by USGS, the states of Idaho and Montana, and the Kootenai Tribe of Idaho.

“These data indicate upstream activities may be affecting water quality and aquatic resources in Montana and Idaho,” said EPA Regional Administrator Gregory Sopkin. “The results, particularly selenium impacts to fish, underscore the need for a more detailed understanding of water quality and continued collaboration to protect Lake Koocanusa and the Kootenai River.”

EPA has long been engaged in efforts to address water quality impacts to Lake Koocanusa, which straddles the border of British Columbia, Canada and the state of Montana. Selenium and nitrate concentrations entering the lake from British Columbia’s Elk River have been increasing since data collection began several decades ago. EPA initiated this study in 2018 to address questions posed by state and tribal partners and to better understand the presence, sources and movement of selenium and nutrients in the Kootenai River watershed downstream of Libby Dam. USGS led the EPA funded study, in collaboration with EPA, state and tribal partners. EPA conducted the fish tissue analysis.


The sampling results released today show elevated selenium levels in some of the 142 fish evaluated in the study, with levels in some mountain whitefish eggs exceeding EPA’s recommended criterion of 15.1 ug/L, the level at which fish reproduction may be harmed. Six of eight mountain whitefish exceeded the EPA criterion. In addition, one redside shiner exceeded EPA’s whole-body criterion for selenium.

Selenium concentrations in water were elevated above background levels but did not exceed EPA recommended criteria for selenium in flowing waters. Selenium was not detected in water samples from Kootenai River tributaries unaffected by discharge from Lake Koocanusa, indicating that the source is the discharge of mine-related constituents from the lake. Nitrate was detected in water immediately below Libby Dam at nearly three times the concentrations observed in previous samples collected from 2000-2004, and significantly higher than those found on the tributaries. Previous studies show that most of the selenium and nitrate in Lake Koocanusa originates from coal mining in the Elk Valley.

Communities and tribes in Montana and Idaho depend upon good water quality and healthy fisheries. EPA’s study indicates that the Kootenai River is being impacted by upstream mining in British Columbia and points to the need for continued monitoring to assess Kootenai River health and to track future trends. EPA is sharing the results of this study with our state, tribal and international partners, and will continue to support the development of information and measures to protect water quality.

Fish tissue samples were also analyzed for mercury, which can be harmful to people who consume fish. Mercury concentrations were generally below EPA fish tissue criteria for methyl mercury except for three northern pikeminnow. Tribes and state agencies will consider whether fish advisories are appropriate.


EPA issued revised national criteria recommendations in 2016 for selenium in water and fish. The Montana Department of Environmental Quality (MDEQ) is currently working with the British Columbia Ministry of Environment and Climate Change Strategies and other parties, including EPA, to develop site-specific water quality criteria for selenium in Lake Koocanusa. MDEQ expects to submit revised selenium criteria to EPA for review next year. Montana also plans to adopt EPA-recommended selenium criteria for the Kootenai River below Libby Dam. Idaho has water quality standards for selenium in the Kootenai River that are consistent with EPA’s 2016 recommendations.

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