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Spokane, Washington  Est. May 19, 1883

Flow fluctuation hard on chinooks


This 1997 photo shows the salmon nesting area of the White Bluffs, located along the Hanford Reach on the Columbia River. 
 (File/Associated Press / The Spokesman-Review)
Shannon Dininny Associated Press

RICHLAND – Columbia River flow fluctuations due to upstream dam operations kill significant numbers of juvenile fall chinook salmon in the Hanford Reach – and the impact is greater than previously estimated, according to the draft of a new study.

The Hanford Reach, the longest remaining free-flowing segment of the Columbia, stretches 51 miles from Priest Rapids Dam to just below the city of Richland. The area is prime spawning habitat for fall chinook, one of the few remaining Columbia River salmon populations that have not been listing under the Endangered Species Act.

The study, a collaboration of nine federal, state and tribal agencies and consultant groups, conducted research in 2003-04 to evaluate the effects of upstream dam operations on spawning and rearing conditions for fall chinook in the Hanford Reach.

In 2003, an estimated 1.6 million juvenile fall chinook were trapped in isolated pools in the reach when river levels dropped due to dam operations. About 1.3 million of those fish died from being stranded above the water level or as a result of higher water temperatures, the study found.

The study also found that the magnitude of the fluctuation was the biggest driver of fish mortality, rather than flow levels themselves. Frequency of the fluctuation also was a factor.

The study did not offer policy recommendations for operating the dam, but is a tool for developing management alternatives, said Howard Schaller, of the U.S. Fish and Wildlife Service. He helped write the study.

“What it means is fish managers and dam operators can collectively get together to use this tool to see what kind of management alternatives can be used to continue productivity of the stock,” Schaller said Friday.

Grant County Public Utility District operates Priest Rapids Dam under a license that expires in October. The utility is in the process of relicensing the dam.

Tom Dresser, fish and wildlife quality manager for the PUD, raised concerns that the study included only one year of data and that no further research was immediately planned.

Dresser also cautioned the authors against making larger recommendations about managing Priest Rapids Dam without considering the impact to dam operations, recreation, cultural resources and habitat elsewhere on the mainstem Columbia River.

“You pinch the system somewhere, you’re going to have a bubble popping out somewhere else,” he said.

Last year, an agreement was reached by dam operators, fish agencies and tribal groups to incorporate additional flow fluctuation limits to protect juvenile fall chinook rearing in the Hanford Reach. The agreement has been submitted to the Federal Energy Regulatory Commission as part of the relicensing process.

As a result of that agreement and earlier work, fall chinook salmon in the Hanford Reach are one of the healthiest stocks in the Columbia Basin, said Linda Jones, PUD director of communications.

In 2003, nearly 100,000 fall chinook salmon returned to the Hanford Reach to spawn, and nearly 80,000 returned last year. That is far above the average return of 47,000 salmon between 1984 and 2003, Jones said.