Overview
Lake Koocanusa is the 90-mile Kootenai River reservoir behind Libby Dam in northwest Montana, extending into British Columbia. The U.S. Army Corps of Engineers operates Libby Dam (dedicated 1975) under Columbia River Treaty arrangements for flood risk management, hydropower, and recreation. The name Koocanusa blends Kootenai, Canada, and USA - reflecting the reservoir's binational footprint.
At normal full pool 2,459 feet the lake covers about 46,500 acres (U.S. and Canada) with roughly 229 miles of shoreline and maximum depth near 370 feet. Steep forested mountains and a long, narrow pool define its character. About half the full-pool length and a large share of surface acres lie in British Columbia.
Fishing for trout, kokanee, and other species is managed with Montana and British Columbia partners. Corps recreation sites and public ramps provide U.S. access near Libby and along the reservoir arms. Corps visitor facilities near Libby Dam interpret Treaty hydropower and flood-control operations.
Treaty flood control can draw the pool far below full elevation. Monitoring current lake levels is essential before launching - drawdowns routinely change ramp usability and shoreline camping. Deep winter drafts for Columbia system flood control are among the largest elevation swings on any Montana lake. Visitors who track the official gage before launching avoid the most common access surprises.
Current Conditions
Lake Koocanusa is currently 11.28 feet below full pool and has fallen slightly over the past week.
- 7-day trendFallingLatest movement can differ from the seven-day trend.
- 7-day changeDown 0.62 ft
- 30-day changeUp 0.37 ft
- Drought conditionsAbnormally Dry
About This Lake
Learn how this lake is managed, what affects its water level, and where Lake Insights gets its data.
Lake Koocanusa is a 46,500-acre reservoir on the Kootenai River managed by U.S. Army Corps of Engineers (Libby Dam); BC Hydro coordination for Canadian reach.