Corps increases release from dam

The U.S. Army Corps of Engineers has ramped up releases from Libby Dam to prepare for spring runoff.

Increased snowpack in the Kootenai Basin has caused discharge to be increased to full powerhouse capacity of 25,000 cubic feet per second. Managers plan to maintain releases at full capacity for the remainder of April or until the start of refill, projected for the first or second week of May, according to a release from the Corps.

The decision was made to help create more storage in Lake Koocanusa and will allow the Corps to retain more Kootenai River flow behind the dam during the spring.

Lake Koocanusa is currently at 2,400 feet. The reservoir will continue to be drawn down at a rate of about 1 foot per day until the start of reservoir refill, when the dam shifts from emptying the reservoir to create storage space to control flooding.

Snowpack in the Kootenai basin is about 115 to 120 percent of normal. The water supply forecast for April through August into Lake Koocanusa is 117 percent of normal.

Above average precipitation for the month of March, which came in the form of snow at higher elevations, has increased the water supply forecast from 93 percent of normal to 117 percent for March and April.  

Libby Dam generally regulates upper river runoff while lower river runoff is mostly unregulated since it flows into the Kootenai River below the dam. The Corps’ flood risk management strategy is to retain as much volume as possible behind the dam, while the downstream unregulated tributaries pass as much of their spring snowmelt and rain flows as possible.

Current projections show that there is about 40 percent chance of being over flood stage at Bonners Ferry. The potential for being near flood stage is highest in late-May through June.