Increased water releases from Idaho’s Dworshak Reservoir have increased dramatically the survival of endangered Snake River salmon heading for the ocean, government scientists reported Wednesday.
Biologists for the U.S. Fish and Wildlife Service said they found 47 percent to 55 percent of tagged fall chinook salmon survived this year with the help of 48 days of extra water releases from Dworshak Reservoir.
That compares with a survival rate of just 7 percent for the young fish in 1992, when special releases to help migration lasted only 11 days.
Until physical modifications can be made to hydroelectric dams on the Snake and Columbia rivers, the releases are the only tool biologists have to boost the survival of young fall chinook salmon, said Fred Olney, Columbia River coordinator for the Fish and Wildlife Service.
The findings are likely to influence decisions by the National Marine Fisheries Service on how Dworshak dam will be operated, Olney added. The fisheries service is in charge of salmon recovery efforts.
Dworshak Reservoir is on the North Fork of the Clearwater River near Orofino, Idaho. Water flows into the Clearwater and, ultimately, into the Snake River.
Given the controversy over the reservoir drawdowns, the Fish and Wildlife Service wanted to keep the public posted on the latest findings of the study, said Dan Diggs, the agency’s associate manager for the Columbia River Basin.
Both of Idaho’s senators, Larry Craig and Dirk Kempthorne, have urged Commerce Secretary Ron Brown to reconsider the reliance on increasing flows for salmon and recognize the need for a full summer pool at Dworshak for recreation.
Craig has said he is working to insert language in an energy bill to limit the power of federal agencies to control reservoir levels.
The Orofino Chamber of Commerce sued the National Marine Fisheries Service and U.S. Army Corps of Engineers to stop the drawdowns, claiming the dramatic lowering of Dworshak Reservoir has hurt tourism.
A federal judge turned down their request to stop the releases, which began in mid-July and are scheduled to continue through Friday.
Federal biologists have asked that smaller water releases continue into September, because the fall chinook are still migrating.
The Columbia River Alliance, which opposes drawdowns on behalf of barge companies, irrigators and other river users, called the research findings “junk science.
“This is the first good water year we’ve had in eight or nine years,” said executive director Bruce Lovelin. “Any increase in survival that these salmon will experience is likely due to the fact that we are moving out of an extended drought cycle.”
The biologists said they found the extra water from Dworshak made water temperatures in the Snake River much cooler. Past studies have indicated that young fish will swim nearer the surface when the water is cooler, rather than diving down to find relief from warm water.
When they are near the surface, the fish are more likely to be diverted by special screens around dam turbines and through a bypass area, where they are captured and barged down the Columbia River, said biologist Billy Conner.
, DataTimes ILLUSTRATION: Graphic: Water flows seem to help salmon
The following fields overflowed: CREDIT = Associated Press Staff writer Julie Titone contributed to this report.