Sturgeon spills to run through J

Sturgeon spills to run through June 16

June 13, 2012

After a five-day interruption for flood risk management, the U.S. Army Corps of Engineers re-commenced spilling as part of the sturgeon flow augmentation at Libby Dam on June 10 and expect the operation to last through Saturday.

The sturgeon flow augmentation operation began on June 4, but the spill operation was halted when heavy rainfall, increased tributary inflows and high Kootenay Lake elevation caused the Kootenai River to rise swiftly and reach flood stage, 1,764 feet above mean sea level, at Bonners Ferry, Idaho. The spill operation resumed June 10 and could include spilling up to 10,000 cubic feet per second above full powerhouse capacity, approximately 26,000 cfs, increasing outflows to about 36,000 cfs for a total of seven non-continuous days.

Spill amounts will be based upon the river stage at Bonners Ferry, which the Corps is targeting to maintain between 1,762.5-1,764 feet elevation during the sturgeon flow operation.

In addition, with upper basin snowpack still higher than normal and the current inflow forecast at 123 percent of average, the Corps continues to closely monitor local conditions and will make flow adjustments as necessary for flood risk management. The Corps plans to release flows of 26,000 cfs for the foreseeable future and possibly continue to spill up to 2,000 cfs after Saturday. The operation after Saturday is intended to maintain enough space behind Libby Dam to accommodate potentially high inflows to the Dam through early July.

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. 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 continue monitoring 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 dam is a multi-purpose water resource developed for flood risk management, hydropower, fish and wildlife, and recreation.