Lake Koocanusa Water Quality

Science Center Objects

Lake Koocanusa is a transboundary reservoir located in southeastern British Columbia and northwestern Montana. The reservoir was officially impounded in 1972 after construction of Libby Dam, which began in 1966. The dam was constructed as part of a treaty between the United States and Canada to cooperatively develop the water resources of the Columbia River drainage basin. The reservoir has a volume of 7.16 km3 and provides flood storage, hydroelectric power production, and recreation benefits. The 148-km reservoir straddles the United StatesCanadian border and impounds water from about 23,271 km2 , or 47 percent, of the Kootenai River drainage basin (Woods, 1982). 

Lake Koocanusa Relative to the International Boundary

Map showing the location of Lake Koocanusa relative to the international boundary. Red triangles show the location of the proposed high-frequency monitoring sites.

(Public domain.)

Three Canadian rivers (Kootenai, Elk, and Bull) exert a major influence on the limnology of Lake Koocanusa and supply 87 percent of the reservoir's inflow (Bonde, 1979). The Transboundary Kootenai River Basin contains critical habitat for the threatened bull trout and genetically pure westslope cutthroat. The river basin also serves a vital role in maintaining adequate flows and water quality for several endangered salmon and steelhead runs in the Columbia River. The Kootenai River below the reservoir provides critical habitat for the white sturgeon (Acipenser transmontanus) (Paragamian, 2012), which was listed as endangered in this river during 1994 through the U.S. Endangered Species Act (U.S. Fish and Wildlife Service, 1994).

From 1972 to 1996 the USGS was actively engaged in research and monitoring of Lake Koocanusa. Woods (1982) conducted a detailed USGS nutrient study of Lake Koocanusa, finding initial reservoir concentrations of nitrogen and phosphorus were large enough to predict eutrophic conditions. In 2013, the USGS was re-engaged with the monitoring and research of Lake Koocanusa and the Kootenai River because contaminants from the Elk River watershed in British Columbia were entering the reservoir and tailwater below Libby dam.

Historic and present-day mining of metallurgical coal in the Canadian headwaters have significantly degraded water quality within the rivers that drain to Lake Koocanusa within the United States. The market for non-thermogenic coal from this area of Canada is projected to be strong for the foreseeable future. The Montana Department of Environmental Quality (MT DEQ) has identified Lake Koocanusa as threatened by selenium (Se) and listed the water body under Section 303 (d) of the US Clean Water Act. Based on data compiled by the USGS and MT DEQ, annual Se loads entering Lake Koocanusa from the Elk and Fording rivers in Canada have increased from 2,600 kg in 1992 to over 13,000 kg in 2012, representing more than a 5-fold increase over 20 years. A single water treatment plant designed to remove Se is currently (2019) operating in the Elk River watershed, with additional treatment plants planned for the future (Teck Coal Limited, 2018). In addition to increasing Se loadings to the reservoir, potential chemical transformations of dissolved and particulate Se in Lake Koocanusa prior to discharging to the tailwater below the reservoir is a potential concern to the white sturgeon (Paragamian, 2012) and other fish species. The U.S. State Department and the Department of Interior are actively engaged in this high visibility transboundary issue.

Schematic diagram of proposed point-of-compliance monitoring platform installed on Lake Koocanusa at the international boundary

Schematic diagram of proposed point-of-compliance monitoring platform installed on Lake Koocanusa at the international boundary. Monitoring components include: (1) Syringe Sipper water-sampling system (yellow circles); (2) diffusive gradients in thin film samplers (blue squares); (3) automated water-quality sonde profiling system (YSI EXO 2); and (4) multi-cell doppler current profiler and lake level monitor (Sontek SR).

(Public domain.)

Specific USGS activities associated with this transboundary issues from 2013 to present include: (1) U.S. Federal agency representative on the bi-national Technical Advisory Committee for the Elk Valley Water Quality Plan; (2) membership in the Lake Koocanusa Monitoring and Research Committee and Se Technical Subcommittee; and (3) monitoring and modeling activities on Lake Koocanusa with federal (Army Corps of Engineers, U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service) and state (Montana Department of Environmental Quality and Montana Fish, Wildlife, and Parks) cooperators (Presser, Naftz, and Jenni, 2018). The Lake Koocanusa Se Technical Subcommittee is currently (April 2019) in the process of utilizing the USGS ecosystem-scale model developed by Presser and Luoma (2010), to assist our federal and state partners in setting site-specific criteria for Se in Lake Koocanusa for the protection of sensitive aquatic life (Jenni, Naftz, and Presser, 2017). This biodynamic model requires information not only on dissolved Se, but on other ecosystem compartments as well including particulate material, invertebrates, fish, and wildlife.

In agreement with the new EPA Se regulations (U.S. Environmental Protection Agency, 2016), the lentic portion of the Kootenai River watershed (Lake Koocanusa) is the most sensitive compartment to transboundary Se inputs from British Columbia. Once the site-specific Se criteria for Lake Koocanusa are adopted by our tribal, state, provincial, and federal partners, the primary point-of-compliance monitoring sites will be in Lake Koocanusa at the international boundary (USGS site number 12300110) and the Kootenai River below Libby Dam (USGS site number 12301933).

Schematic diagram of monitoring supplements to the existing USGS gage on the Kootenai River below Libby Dam

Schematic diagram of proposed Syringe Sipper water-sampling system, diffusive gradients in thin film samplers, and water-quality sonde monitoring supplements to the existing USGS gage on the Kootenai River below Libby Dam

(Public domain.)

Although Se loadings entering Lake Koocanusa from the Elk River are critical to monitor, the concentration of Se within Lake Koocanusa at the International boundary is likely the most important point-of compliance monitoring location for the future enforcement of the transboundary, site-specific water quality criteria. This standard is currently under development and approval by the MT DEQ, British Columbia Ministry of Environment, and U.S. Environmental Protection Agency. Modeling results led by the USGS (Presser and Luoma, 2010) will be used by MT and BC regulators to adapt and enforce a site-specific Se guideline(s) for the protection of aquatic life in Lake Koocanusa. A conceptual model framework was published in 2017 (Jenni, Naftz, and Presser, 2017) to serve as a coherent and consistent structure for organizing relevant scientific information, to provide an appropriate context for interpreting new information as datasets and site parameters are developed, and to identify data and science gaps that limit understanding of the implications of alternative Se criteria. A secondary point-of-compliance monitoring site will be in the tailwater below Lake Koocanusa at the Kootenai River below Libby dam (USGS site number 12301933).

A new Lake Koocanusa floating platform data collection station just upstream from Libby Dam will be installed in 2020. A link to this new site will be posted here when those real-time data become available.

Interactive color maps of water-quality parameters with depth over time will also be provided here in the future.