Cooler than normal temperatures combined with above normal rain and snow is creating a situation where significantly higher than normal Kootenai River flows are more likely in the coming weeks.

The U.S. Army Corps of Engineers has created water storage space for greater than normal inflows by drafting the Koocanusa Reservoir down to 2,354 feet in elevation, approximately 100 feet below capacity, on the reservoir side of Libby Dam, Libby, Mont. The Corps is targeting a reservoir elevation of 2,348-2,351 feet by the end of April. The reservoir will continue to be drafted at a rate of roughly one foot per day until the start of reservoir refill, projected for the first or second week of May.

Current high-elevation snowpack is 128 percent of normal and lower-elevation snowpack is 153 percent in the Kootenai River basin. The National Oceanic and Atmospheric Administration forecast is for cooler than normal temperatures through June with continued higher than normal precipitation through May.

Generally upper river runoff is regulated by Libby Dam, while lower river runoff is mostly unregulated since it flows into the Kootenai River below the dam. The Corps’ flood risk management operation is to retain as much Kootenai River flow as possible behind Libby Dam while the downstream unregulated tributaries, which are forecasted to flood, pass as much of their spring snowmelt and rain flows as possible. It is likely that Kootenai River flows may be at or above flood stage from unregulated tributary flows alone.

“Forecasts suggest we could see significant rapid rises in reservoir elevation, up to eight feet per day, by mid-May through mid-July,” said Joel Fenolio, Upper Columbia Senior Water Manager for the Army Corps of Engineers. “The Kootenai River may be at or near flood stage for a period of time starting mid-May. Downstream tributaries to the Kootenai which are not controlled by Libby Dam, such as the Yaak, Moyie and Fisher Rivers, are expected to be at or above flood stage as well.”

Residents and businesses in the river basin should be prepared for potentially swift water rises in a relatively short period of time once snowpack begins to melt.

The Corps is regulating Libby Dam for flood risk management, closely monitoring weather conditions, snowpack readings and inflows to mitigate flood risk downstream.

Public information meetings for Libby Dam operations are scheduled for:
    • May 9 at the Kootenai River Inn, Bonners Ferry, Idaho, at 7 p.m.
    • May 12 at Libby City Hall, Libby, Mont., at 7 p.m.