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Low river to follow high water

 

Annie Wooden

WHITE WATER - The Clark Fork River rages through the dry channel dam in Thompson Falls.

High water has put a snag in recreation opportunities on the Clark Fork River above the Thompson Falls Dam. NorthWestern Energy was forced to remove steel beams to allow more water to flow through the dam. The reservoir will need to be drawn down several feet for those beams to be replaced once the high water ebbs.

With the high flows in the Clark Fork River this spring, NorthWestern Energy was forced to release several removable steel spillway beams at the Thompson Falls Dam. The action is aimed at allowing greater-than-normal amounts of water and debris to safely pass through the dam. Flows at the Thompson Falls Dam have reached as high as 103,000 cubic feet per second (cfs). NorthWestern Energy used both the main dam and the smaller dry channel dam to increase flow at the facility.

The removal of the steel spillway beams means that NorthWestern Energy will have to draw down the reservoir for repair work at the dam. According to NorthWestern Energy, the reservoir will be lowered once river flows drop below 20,000 cfs. The reservoir will then be lowered to the crest of the dam, an elevation of 2,380 feet (16.5 feet down from full pool). Once the reservoir elevation drops to that point, work will immediately begin on replacing the beams.

"We apologize for this inconvenience, but the drawdown is unavoidable," NorthWestern Energy said in a statement. "After completion of the work, the reservoir will be refilled as soon as reasonably possible given the inflows, likely to be late July to mid-August."

The last time NorthWestern Energy was forced to draw down the water level for dam repairs was in 2011. According to a statement from NorthWestern Energy, the replacement work will take about two weeks.

NorthWestern is advising its neighbors around the reservoir and other users to consider removing docks and boats from the water to avoid damage as the reservoir elevation drops and use caution navigating the shallow reservoir.

 

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