Libby Dam spill now in doubt

Plans for an experimental water spill from Libby Dam to help Kootenai River white sturgeon this spring now are uncertain because of below-average mountain snowpack above the dam.

Snowpack in the Kootenai River Basin is 71 percent of average and well below last year’s snowpack at this time of year.

The streamflow forecast for the Kootenai River Basin, which is based on receiving average precipitation over the next few months, is just 66 percent of average from April through July.

How the rest of the winter plays out will determine whether the planned spill will proceed, said Brian Marotz, a fisheries program manager for Montana Fish, Wildlife and Parks who coordinates with other agencies on dam operations.

“It could go either way, but there’s definitely a relationship between water availability and the ability to do a [spill] test,” Marotz said.

With eroding water supply forecasts, he said, “just meeting the minimum flows in the Kootenai River is going to make it very difficult to refill” Lake Koocanusa over the next few months.

And refilling the reservoir is crucial to proceeding with a spill. “The surface elevation of the reservoir needs to be high enough that you can physically use the spillway,” Marotz said.

A spill operation must also meet other criteria to have a meaningful chance of encouraging white sturgeon to move into the best spawning areas just upstream from Bonners Ferry, Idaho.

Adult sturgeon need to be in the right place in the river and the correct temperatures of water need to be available to release through the dam’s selective withdrawal system at the right time.

“That’s a lot of stuff,” said Marotz, a member of an interagency white sturgeon recovery team.

For years, the state of Montana has resisted releasing water over the dam’s spillway because it can result in gases that are harmful to native fish populations, and those higher gas levels exceed Montana’s water quality standards.

The state agreed to a legal settlement, however, that allowed for spills to determine if higher flows improve sturgeon spawning success. For that to happen, Marotz said, the Montana Department of Environmental Quality will draft an unprecedented waiver of the state’s water quality standards — with conditions.

The waiver will specify maximum gas saturation levels in the river and where those levels will be measured. It limits the spill to a range of 5,000 cubic feet per second up to 10,000 cfs, in addition to releasing water through the dam’s turbines at maximum capacity, about 25,000 cfs.

The outlook for a spring spill could change “if we suddenly get a bunch of precipitation,” Marotz said. “We’ll know by June.”

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com