Libby Dam spill test for sturgeon planned in June

KALISPELL, Mont. - A spill test for white sturgeon will proceed at Libby Dam in June, based on recent inflow forecasts for Lake Koocanusa, and an old dispute has resumed over the way the dam will operate this summer.

"We will have a sturgeon operation in early June," said Jim Litchfield, Montana's representative on an interagency panel that oversees hydropower operations throughout the Columbia River Basin. "Folks in that area can expect flows to go up quite dramatically in early June for about a week."

The dam will release a powerhouse capacity of 25,000 cubic feet per second, and about 10,000 cfs will be released over the spillway. The operation is intended to test whether the spill changes white sturgeon spawning behavior in the Kootenai River near Bonners Ferry.

To prepare for the spill during a low-water year, Libby Dam has been releasing minimum flows of about 4,000 cfs, when it is usually operated for flood control purposes.

"We are trying to store as much water as we can during the month of May," Litchfield said.

The decision to proceed is based on the U.S. Army Corps of Engineers' latest forecast that inflows at Lake Koocanusa will be 4.88 million acre feet from April through August, said Litchfield, adding that the Corps forecast is historically on the high side.

If actual inflows fall short of the forecast, he said, Lake Koocanusa will fall short of refilling to full pool.

The state of Montana has resisted spill operations at Libby Dam for years because of impacts to native fish below the dam. But the state participated in a legal settlement in 2008 that stipulated for a spill test to happen if certain conditions were met.

Female sturgeon, fitted with sonic transmitters, need to be properly positioned in the river below Bonners Ferry, the right temperatures have to be available from the reservoir, and there has to be an adequate supply.

The state of Montana also established restrictions for the spill, limiting it to seven days and implementing safeguards to ensure that gas levels in the river caused by the spill do not exceed certain levels. Elevated gas levels can cause trauma to fish below the dam.

The spill is intended to entice sturgeon to move upstream from Bonners Ferry to an area with optimal spawning habitat. In past years, most spawning activity had been downstream over a sediment-covered riverbed where egg survival has been low.