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Upper Columbia: Peak Runoff Yet To Come On Rivers Already Exceeding Flood Stage
Posted on Friday, May 20, 2011 (PST)

High water has started to cause some problems at the outset of a flood season that is expected to last for weeks in the Upper Columbia River Basin.


“I believe what we’re seeing is the start of a pretty long flood season,” said hydrologist Ray Nickless with the National Weather Service in Missoula, Mont.


“There’s still lots of snow left to melt,” he said. “That’s why we’ll see rivers continue to stay high through May and into June.”


The Thompson River and the Yaak River in Lincoln County exceeded flood stage this week and then receded due to cooler temperatures. The Stillwater River in Flathead County exceeded flood stage early in the week and those flows are expected to continue through most of next week.


Marty Whitmore, the warning response meteorologist for the National Weather Service in Missoula, stressed that peak runoffs have yet to come, even on rivers that have already exceeded flood stage, and the same goes for streams flowing from well-above average mountain snowpacks.


The most remarkable water content was recorded at the Noisy Basin automated snow gauge on the Swan Mountains — a record high 80 inches that has only recently started to melt.


Noisy Basin is one we’ve been watching all winter just because of the impressive amount of water in the pack,” Whitmore said. “We’re just now starting to tap into that.”


A prolonged runoff has been a concern for the U.S. Army Corps of Engineers and residents in Bonners Ferry, Idaho, which can be impacted by high flows on the Yaak, Fisher and other Kootenai River tributaries.


Libby Dam Superintendent Mick Shea said the Corps is forecasting that the Kootenai River could reach its flood stage elevation of 1,764 feet and could rise to 1,765 feet.


“We think we are going to be at or near flood stage for four to eight weeks” at Bonners Ferry, he said.


Boundary County, Idaho, officials are alarmed because Bonners Ferry agriculture starts to get damaged when the river reaches a 1,758-foot elevation. In 2002, when the river rose to 1,758 feet, farmers endured about $2 million in crop damage and those flows only lasted a few days.


Libby Dam has been operated to put Lake Koocanusa at about 121 feet below full pool as of May 11, a reservoir low that hasn’t been seen since the severe winter of 1996-97.


Since May 11, the reservoir has started to refill, even with the dam discharging at powerhouse capacity of 20,000 cubic feet per second.


As the Kootenai River rises at Bonners Ferry, Libby Dam discharges will be scaled back and Lake Koocanusa will begin a more rapid refill.


Montana Gov. Brian Schweitzer and a good part of his administration were in Kalispell Thursday to meet with local emergency responders and inform them of the state’s capabilities in assisting with flood response.


“We’re just here to remind everybody that we’re a team,” Schweitzer told northwest Montana law enforcement, fire and local government officials at the Flathead County Office of Emergency Services. Earlier in the day, he had a similar meeting In Missoula.


Jim Lynch, director of the Montana Department of Transportation, said maintenance personnel are regularly monitoring bridges and culverts and in some cases are actively involved in clearing debris.


Bruce Measure, who chairs the Northwest Power and Conservation Council as a Schweitzer appointee, said he is confident that Libby and Hungry Horse Dams have been managed well to allow for plenty of storage for runoff while holding back on discharges to curb flooding on the Kootenai and Flathead rivers.


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