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Dworshak Flows to be Adjusted

by Eric Barker
Lewiston Tribune, August 15(?), 2002

Idaho, tribe win a round in timing releases for fish

After three years of trying, the Nez Perce Tribe and the Idaho Department of Fish and Game scored a rare victory in the management of Dworshak Reservoir outflows.

The state and tribe convinced the so-called salmon managers, the U.S. Army Corps of Engineers, National Marine Fisheries Service, Washington, Oregon and Montana to ease back on flows in the second half of August.

The move will leave more water in the reservoir in September, which will be used to attract adult steelhead and fall chinook into the Snake and Clearwater rivers. The water also will help juvenile fall chinook that have not yet migrated to the ocean.

"We are just really pleased that everyone came together on this," said Greg Haller of the tribe's water resources department.

The federal salmon recovery plan calls for Dworshak water to be used in July and August to help cool the Snake River and flush juvenile salmon to the ocean. But the state and tribe have long argued some of the water should be saved for late summer, when it can be used to coax adult fish up the Snake River.

Haller credited a good winter that left a healthy snowpack in the North Fork of the Clearwater River basin, flexible spring flood control measures by the corps, and the persistence of the state and tribe in continuing to push their plan, for the decision that emerged from the technical management committee.

The committee is made up of fisheries and water managers from Idaho, Oregon, Washington, Montana, Columbia River Indian tribes and federal fisheries agencies. It meets bi-weekly through the spring and summer to make water management decisions to benefit salmon and steelhead.

Each year Dworshak Reservoir is lowered 80 feet as water is flushed out to help cool the Snake River. The state has questioned the need for the flows because it harms recreation at the reservoir. But it and the tribe have objected to all of the water being used in the heart of the summer, leaving none for September, when it has traditionally been used to attract returning adult salmon and steelhead.

Once the cool water flows from the reservoir end, the Snake River can rise several degrees warmer than the Columbia River. The condition, known as a thermal blockade, can delay the return of adult salmon and steelhead.

In the past, outflows from Dworshak Reservoir were used to combat the blockade. But since salmon and steelhead have been listed, and Dworshak Reservoir water has been used as a tool to help young salmon and steelhead reach the ocean, the adult flows have ended.

The state and tribe argued that with judicious planning, enough water would be left for use in September without dropping the reservoir more than 80 feet below full pool.

Under the plan adopted Thursday, flows from the dam will drop from the current level of 13,800 cubic feet per second to 12,000 cfs Aug. 25. Flows will drop again Sept. 1 to 10,000 cfs and remain there until at least Sept. 10.

Under the old plan, all of the water would have been used by the end of September.

"The idea here is to provide cold water benefits to returning adults and also later migrating juvenile fall chinook," Haller said.

The plan can be revisited if the reservoir level drops too quickly, according to Karl Kanbergs, a hydrologist with the corps reservoir control center at Portland.

The corps has begun a study that will track returning adults to see if they take advantage of the cooler flows. A small number of fish are being captured and given special tags that measure the temperature and depth of water in which they travel. The study is expected to help fisheries managers learn the value of the late summer flows, which have been debated for the past several years.

Kranbergs said the latest water supply forecast under the new plan calls for Dworshak Reservoir to hit elevation 1,520, 80 feet below full pool, at about the end of September.

The reservoir was 41.5 feet below full pool Thursday afternoon.

Eric Barker
Dworshak Flows to be Adjusted
Lewiston Tribune, August 15(?), 2002

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