Lake Koocanusa () is a reservoir in British Columbia (Canada) and Montana (United States) formed by the damming of the Kootenai River by the Libby Dam in 1972. The Dam was formally dedicated by President Gerald Ford on August 24, 1975.

thumb|The Koocanusa Bridge over Lake Koocanusa from the east bank

The lake is formed north of the dam, reaching to the Canada–United States border and further into British Columbia. The lake holds 13% of the water in the Columbia River system. The town of Rexford was moved, as well as the Great Northern Railway line. The town of Waldo, British Columbia is now covered by the lake. What was once a barrier to river travel, Jennings Canyon is now inundated by the lake. The Elk River joins the Kootenay River in the northern part of Lake Koocanusa, within Canadian territory.

Lake Koocanusa was named in a contest won by Alice Beers of Rexford, Montana. A September 24, 2020 Montana Department of Environmental Quality presentation to the Board of Environmental Review Meeting, reported that the 95% of the selenium coming into Lake Koocanusa originates from the Elk River—"which has been contaminated by current and historic coal mining in the Elk Valley." The average selenium levels in Lake Koocanusa were 1 part per billion. Montana has established new standards for selenium—0.8 parts per billion. Because of the high bioaccumulation of selenium in fish, excessive levels of selenium in an aquatic ecosystem has implications for human health. In the spring of 2020, Teck Resources, had "reported a dramatic decline in adult westslope cutthroat trout in Elk Valley waterways closest to its mines". Montana's has been in force since the fall of 2020, but British Columbia has not aligned their standards yet.

{| class="wikitable"

! colspan="1" rowspan="1" |Species

! colspan="1" rowspan="1" |Family

! colspan="1" rowspan="1" |Native to MT

|-

|Brook Trout

|Trout

|Introduced

|-

|Bull Trout

|Trout

|Native

|-

|Burbot

|Codfish

|Native

|-

|Kokanee

|Trout

|Introduced

|-

|Largemouth Bass

|Sunfish

|Introduced

|-

|Largescale Sucker

|Sucker

|Native

|-

|Longnose Dace

|Minnow

|Native

|-

|Longnose Sucker

|Sucker

|Native

|-

|Mountain Whitefish

|Trout

|Native

|-

|Northern Pike

|Pike

|Introduced

|-

|Northern Pike Minnow

|Minnow

|Native

|-

|Peamouth

|Minnow

|Native

|-

|Pumpkinseed

|Sunfish

|Introduced

|-

|Rainbow Trout

|Trout

|Introduced

|-

|Redside Shiner

|Minnow

|Native

|-

|Westslope Cutthroat Trout

|Trout

|Native

|-

|Yellow Perch

|Perch

|Introduced

|}

See also

  • List of lakes of British Columbia

References

  • The Libby, Montana, web site with more information about Lake Koocanusa
  • Libby Dam, United States Army Corps of Engineers