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Dworshak to Give Up its Cool Bounty

by Eric Barker
Lewiston Tribune, July 3, 2013

Soaring temperatures move managers to release chilled water from dam early to help migrating fish

Dworshak reservoir oftentimes is called upon to cool the Lower Snake River for the sake of Idaho's migrating adult salmon. Salmon and water managers from the Pacific Northwest are hopeful a strong pulse of 43-degree water from Dworshak Reservoir will help cool a quickly warming lower Snake River.

Every summer, about 2 million acre-feet of frigid water from the depths of the reservoir is released to help keep the Snake hospitable to migrating juvenile fall chinook and returning adult steelhead, some of which are protected by the Endangered Species Act.

Most years, the cooling flows don't begin until after the Fourth of July weekend. But this week's heat wave, which is sending air temperatures past the century mark across much of the region, is elevating water temperatures and prompted an earlier-than-normal call for relief.

For example, the Clearwater River at Orofino above the mouth of the North Fork reached 76 degrees Tuesday. The Snake River south of Asotin hit 71 degrees and the lower Salmon River near White Bird was 72 degrees. Below Lower Granite Dam, which is 35 miles west of the Lewiston-Clarkston Valley, the water was 65 degrees Tuesday.

Temperatures in the low 70s are considered unsafe for salmon and steelhead.

"We have seen this kind of scenario back in the late (19)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."

The agency began increasing the outflow from Dworshak Dam on Sunday and by Tuesday flows had hit 13,000 cubic feet per second, more than double the volume of just a few days earlier. The water that is drawn from more than 100 feet below the surface exits the dam at 43 degrees.

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. But it has already cooled temperatures near Spalding. On Sunday, before the increased flows from the reservoir, the water rose to 64.5 degrees there. On Tuesday, it was 59 degrees.

Paul Wagner of the National Marine Fisheries Service at Portland said the 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.

But he also noted the water will be exhausted ahead of schedule at the current volume.

"This is not sustainable," he said. "We can't keep it at this rate or we are going to run out too quickly."

According to the provisions in the federal government's plan that outlines how Snake and Columbia River dams will be operated to lessen effects on protected fish, the elevation of Dworshak Reservoir should reach 1,535, or 65 feet below full pool, by the end of August and 80 feet below full pool by the end of September.

This week's early start will mean the reservoir won't brim over for holiday campers later this week. On Tuesday, the reservoir was 2 feet below full pool after being full Saturday. The corps estimates the reservoir will be 5 feet below full pool Thursday and 8 feet below by Monday. The receding water can make it difficult to access some of the remote campsites on the shoreline of the 55-mile-long reservoir and is unpopular with many campers and boaters there.

Eric Barker
Dworshak to Give Up its Cool Bounty
Lewiston Tribune, July 3, 2013

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