Water managers at the U.S. Army Corps of Engineers, along with federal and state fish biologists, determined forecasted inflows are sufficient to provide flow augmentation at Libby Dam, Mont., for endangered Kootenai River white sturgeon downstream in Idaho.
While this year’s augmentation flows do not include spilling additional volume through the dam’s spillway gates, plans include increasing flows to full powerhouse capacity for about a week, on two separate occasions, in an effort to provide river conditions that may foster sturgeon spawning.
Sturgeon flow augmentation is set to begin Saturday at noon when local Kootenai River tributaries below Libby Dam are forecasted to peak, the trigger for initiating releases from the dam in support of sturgeon recruitment. Flows will be increased to full to powerhouse capacity, approximately 26,500 cubic feet per second, and will remain at that level for about one week before decreasing to 18,000 cfs.
A second pulse of powerhouse capacity flows will be timed to coincide near peak inflows above the dam later this month or in early June.
The flow augmentation operation is part of a collaborative, ongoing effort by regional biologists to enhance spawning and migration conditions for sturgeon in the Kootenai River near Bonners Ferry, Idaho. Increased flows are intended to provide river conditions that may foster sturgeon spawning, successful egg hatching, and survival of larval sturgeon in the reach of river upstream of Bonners Ferry, where sturgeon do not currently spawn successfully. While hatchery reproduction has increased the number of young sturgeon in the river, federal, state, and tribal partners hope to improve habitat conditions for adult sturgeon to successfully reproduce on their own.
The U.S. Army Corps of Engineers' primary consideration in operating Libby Dam is to minimize risk to human life, health, and safety, while meeting the dam’s multiple purposes and responsibilities. The Corps will closely monitor Kootenai River elevation in Bonners Ferry during the sturgeon flow augmentation and will adjust operations with the aim of staying below 1,764 feet, the local flood stage.
Libby Dam is a multi-purpose water resource developed for flood risk management, hydropower, fish and wildlife, and recreation.