NEWHALEM – Seattle City Light is holding water in Ross Lake to help reduce flooding in the Skagit River around Concrete and Mount Vernon.
Since 2 p.m. on Sunday, Jan. 6, more than seven inches of rain have fallen in the area of the upper Skagit where City Light operates its Gorge, Diablo and Ross dams.
The U.S. Army Corps of Engineers asked City Light early Monday morning to limit the amount of water discharged from Ross Dam to 5,000 cubic feet per second or less. By 2 p.m. Monday, City Light had completely shut down Ross Dam operations to capture as much water as possible in the reservoir behind the dam and reduce downstream flooding.
As of 7 a.m. Tuesday, Ross Lake had risen more than 3 feet, reducing the flood crest by at least that amount.
Ross Dam is the uppermost of City Light’s three dams on the Skagit, with Gorge Dam the lowermost and Diablo Dam in the middle. Along with water from Ross, sidestream water and any additional rain collects in Diablo and Gorge lakes behind the two lower dams. Gorge Lake became filled to capacity Monday night by about 10 p.m., and City Light had to begin sending water through Gorge Dam’s spill gate.
Still, by shutting down Ross Dam, City Light was able to limit the spill at Gorge Dam to about 3,000 cfs as of 7 a.m. Tuesday. The Corps of Engineers has reported that the Skagit crested at Concrete during the night with a flow of about 98,000 cfs.
“As long as we have room behind the dams, we will capture water and not add to downstream flows during a flood situation,” said Mike Sinowitz, City Light power marketing director.