SEATTLE – 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, including spill, at Libby Dam, Mont., for endangered Kootenai River white sturgeon in the Kootenai River downstream in Idaho.
Sturgeon flow augmentation began Monday after appropriate conditions were met, including reservoir and river water temperatures, reservoir elevation, and sturgeon behavior in the Kootenai River near Bonners Ferry, Idaho. Outflows were initially increased to 15,000 cubic feet per second on Monday. Flows increased to 20,000 cfs on Tuesday and were held at that level for three days until switching to full powerhouse capacity (approximately 26,500 cfs) today.
A spill test of up to 10,000 cfs above powerhouse capacity will begin June 4 and last up to seven days. Outflows from Libby Dam may reach up to 37,000 cfs depending on how much water can be released from the powerhouse.
Biologists and water managers will monitor the spill operation, called for in the 2006 U.S. Fish and Wildlife Service (USFWS) Biological Opinion, as clarified in 2008, to test whether additional flows over the spillway will provide the habitat conditions thought to be necessary for successful sturgeon spawning. Water temperature and total dissolved gas levels will be monitored by the Corps to ensure they do not exceed criteria established by the Montana Department of Environmental Quality. Montana Fish, Wildlife and Parks will monitor fish for symptoms of gas bubble trauma.
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. 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 sturgeon flow operation will be closely monitored to ensure that the spill test does not exceed flood stage below Libby Dam.
Libby Dam is a multi-purpose water resource developed for flood risk management, hydropower, fish and wildlife, and recreation.
Release no. 12-006