Reservoir Repairs Threaten Chinook Salmon

salmon1Water levels in Cougar Reservoir are being lowered this month for necessary repairs to the dam’s main water intake. Recent inspections by the Army Corps of Engineers revealed that three trash rack panels had become dislodged and allowed debris to enter the dam’s temperature control tower.

The Corps now needs to lower water levels in the reservoir to about 80 feet below normal so crews can remove the debris and repair the panels to prevent further debris from entering the main water intake. At the current rate of release, water should reach intended levels by March 20. In a normal year, the Corps begins filling the reservoir in February to reach optimal summer water storage. However, delays for repairs could mean water levels lower than usual.

“If we are able to start refilling the reservoir in early April and have a fairly average water year, we will be able to refill the reservoir to about 1,640 feet—50 feet below the maximum summer elevation,” said Tina Teed, the Willamette Valley Projects reservoir regulator.

This summer’s water levels may limit the availability of two boat ramps at Cougar Reservoir, which require a minimum water elevation of 1,635 feet above sea level in order to be usable.

The repair could also affect spring migrations of Chinook salmon, as the south fork of the McKenzie River is prime habitat for this endangered species. Adult salmon depend on water flows from the dam’s hydropower unit to find the collection facility from which they are transported around the dam. Despite lower than normal levels, the reservoir should be in better shape than during last year’s drought when water levels hardly reached 1,600 feet, but the prospect of greater threats to this already endangered species is greatly concerning.

By Taylor Smith