Corps: Low snowpack means low flood risk

BONNERS FERRY — Barring any unusually high amounts of precipitation in June, the U.S. Army Corps of Engineers is predicting a low flood risk for the Kootenai River this spring.

“Snowpack is pretty bleak south of the border,” said Joel Fenolio, Upper Columbia Senior Water Manager, at the March KVRI meeting. “It’s been a weird year for precipitation and temperature.”

Even though precipitation has been above average this winter, the higher than normal temperatures caused the precipitation to be rain instead of snow. The snowmelt won’t be the same as the last few years since the precipitation hasn’t been building up the snowpack, said Fenolio.

Around Libby, Mont., the snowpack is about 85 percent of average and in Boundary County it ranges from 25 to 50 percent of average. The upper Kootenai watershed is faring the best with 117 percent of average precipitation.

With rain this winter, Lake Koocanusa has been slowly filling instead of holding steady like normal. The higher levels in the reservoir are manageable with the lower snowpack in the mountains explained Fenolio.

The Corps of Engineers is forecasting 97 percent of average inflow into Libby Dam for April to August.

June precipitation is always the wildcard in the forecast, said Fenolio.

With the current precipitation outlook, sturgeon operations will be at half the volume of prior years said Fenolio. Instead of a double peak of seven days each, there may only be one peak release of seven days in late May or early June.

Typical summer releases from Libby Dam are planned unless the main Columbia River needs more water for salmon. Then Libby Dam operators could be asked to draft 10 feet from the reservoir. The extra water would be drafted from early/mid-July to August with releases up to 15,000 cfs. The extra water would result in the Kootenai River ranging from 1,750 feet to 1,755 feet (still below flood stage of 1,764 feet) for a portion of the summer.

The Corps of Engineers should know in April whether or not they need to draft extra water for salmon. Engineers are modeling the scenario because it would impact refilling the reservoir. The reservoir should refill as long as there is June precipitation, said Fenolio.

Despite the inflow into the reservoir, Libby Dam has been releasing 4,000 cfs since January. The fluctuations in the Kootenai River’s water levels have been from the tributaries, said Fenolio.

British Columbia is taking advantage of Libby Dam not operating at powerhouse capacity in March. They are lowering the level of Kootenay Lake two weeks earlier to a minimum elevation of 1,739.1 feet on March 20 according to Greg Hoffman, U.S. Army Corps of Engineers.

With the channel restriction at Grohman Narrows, water cannot be released suddenly from Kootenay Lake if Libby Dam has to increase flow. The lowering of Kootenay Lake will result in lower backwater on the Kootenai River, said Hoffman.