Libby Dam operations focused on flood control
by Brent Shrum, Kootenai Valley Record
May 21, 2008
Lessons learned in 2006, when unanticipated May rains led to a massive spill from Libby Dam, are factoring heavily in planning for dam operations in 2008.
In 2006, “the Corps was trying to be all things to all purposes,” said Libby Dam manager Mick Shea during the U.S. Army Corps of Engineers’ annual public information meeting last Thursday night in Libby.
In attempting to balance competing and sometimes conflicting needs for recovery of Kootenai River white sturgeon and downstream salmon, power production and recreation on Lake Koocanusa, the Corps was left unable to make the necessary adjustments to prevent flooding when taken surprise by heavy precipitation in late spring, Shea explained. This year, as in 2007, Libby Dam will be managed in strict accordance with VARQ flood control procedures that provide for higher flows during spring runoff with a later refill of the reservoir. Rigid adherence to VARQ in 2006 might still have resulted in a small spill, but flows would have been much lower than what actually occurred, Shea said.
The runoff forecast for April through August calls for 6.1 million acre feet of inflows, which is “slightly less than average” for the 70-year period between 1929 and 1999, said Amy Reese, a hydraulic engineer for the Corps’ Seattle District. The reservoir is targeted to reach a peak elevation of 2,453.7 feet – a few feet below the full-pool level of 2,459 feet – sometime in July, with summer flows from the dam at 17,700 cubic feet per second.
While data sites indicate more snow at low elevations in the U.S. portion of the Kootenai Basin, there is less snow at higher elevations in Canada, Reese said.
“Your percentages as you get higher and higher are going to get closer to normal,” she explained.
An after-action report on the 2006 flooding places a renewed emphasis on the Corps’ mission to protect human life, health and safety as the first priority, said Seattle District fishery biologist Evan Lewis.
“It was always implicit,” he said. “But now it’s explicit.”
The Corps is now operating with very strict protocols on how Libby Dam is managed when inflows are on the rise, Lewis said. Deviation from strict VARQ procedures will require defined evaluation and approval procedures.
The after-action report led to “lots of nuts and bolts” on management procedures including staffing, contracting and communications in emergency situations, Lewis said.
The Corps has improved its internal and external communications processes, clarified VARQ flood control procedures, and adopted a new water management tool that considers a wide range of possible scenarios, he said.
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Editor’s Note: See the May 19, 2008 edition of the Kootenai Valley Record for the printed version of this story. The Kootenai Valley Record publishes once a week, on Monday, in Libby, Montana. They are a locally owned community newspaper, located at 403 Mineral Avenue in Libby. For in-county and out-of-county subscription information, call 406-293-2424, or e-mail kvrecord@gmail.com.
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