Rain increases capacity over dam

MURTAUGH, Idaho – Federal managers hope to help young salmon migrate seaward by increasing flows of the Snake River through American Falls Dam in Southern Idaho this week, and river runners will get the added bonus of frothy whitewater.

After consecutive years of drought, a rainy spring has left American Falls Reservoir at 89 percent capacity and given the Bureau of Reclamation an opportunity to fulfill Idaho’s agreement for higher Snake River flows to aid the passage of juvenile salmon downstream.

It’s the first time since 2001 that the agency has been able to release additional water from the reservoir, which is the largest in the Upper Snake River Basin that stretches into Idaho, Wyoming and Montana. As of Tuesday, reservoirs in the basin were 82 percent full overall.

“We look for every opportunity to fulfill our salmon water augmentation requirements,” said Tim Miller, a hydrologist with the agency.

Water managers are still developing a release schedule, but expect to send 150,000 acre-feet of water through American Falls Dam over the next 50 days, Miller said. An acre-foot is enough water to cover an acre one foot deep.

Monday, the bureau began sending an additional 500 cubic feet per second of water down the Snake River from the dam and expect to increase that to as much as 1,500 cfs by today.

“We do know at 1,500, there will be some recreational benefits,” said Ted Day of the bureau’s regional office in Boise.

Those benefits will be most visible in the stretch of Class IV and Class V whitewater rapids on the Snake near Murtaugh.

“That’s a pretty nice flow for kayaks,” said Grant Amaral, author of “Idaho the Whitewater State.”

“When it’s high, it’s one of the best runs anywhere.”

Olin Gardner, who operates the Idaho Guide Service, expects to be taking clients through the whitewater by the weekend, joining other enthusiasts on the river.

“They’ll be coming out of the woodwork,” said Gardner.

The higher flows are also expected to add another 600 cfs to the river as it plunges 212 feet over scenic Shoshone Falls near the city of Twin Falls. Miller said even if the demand for irrigation water below American Falls this summer increases slightly, the reservoir still will have enough water to handle farmers’ needs through the end of the growing season.

“We still should have more carry-over water this year than we had the last year or the year before,” he said.