LEWISTON – Pacific Northwest water managers are releasing a pulse of cold water from the Dworshak Reservoir earlier than usual in hopes of cooling water temperatures in the lower Snake River and improving conditions for salmon and steelhead.
Each summer, managers release about 2 million acre-feet of 43-degree water from the reservoir to keep stretches of Snake River and its tributaries cool for juvenile fall chinook and returning adult steelhead.
But the release this year is coming earlier than normal due to the heat wave that has sent air temperatures into the triple digits, which has elevated water temperatures. The Lewiston Tribune reported the Clearwater River near Orofino, Idaho, reached 76 degrees Tuesday while the Snake River near Asotin, Wash., hit 71 degrees. Temperatures in the low 70s are considered unsafe for salmon and steelhead.
Officials began increasing flows Sunday.
“We have seen this kind of scenario back in the late ’90s, but since about 2000 we haven’t seen anything quite as severe as we are seeing right now,” said Steve Hall, reservoir manager for the U.S. Army Corps of Engineers at Walla Walla. “Hopefully it will be short-lived.”
Hall said it will take about four days for the cool flows to reach the downriver side of Lower Granite Dam, where the federal government’s salmon and steelhead protection protocols call for a maximum temperature of 68 degrees.
Paul Wagner of the National Marine Fisheries Service at Portland said state, tribal and federal officials try to time the flows to prevent overheating at Lower Granite.
“Once you get behind, you are too late,” he said.
He also noted the early release has consequences.
“This is not sustainable,” he said. “We can’t keep it at this rate or we are going to run out too quickly.”