Officials releasing more cold water from Dworshak Reservoir to aid migrating salmon and steelhead

Water managers at the Army Corp of Engineers are ramping up flows leaving Dworshak Dam as part of an annual effort to cool the lower Snake River and improve conditions for migrating salmon and steelhead.

The agency expects the lower North Fork of the Clearwater River beneath the dam to hit 9,500 cubic feet per second by Wednesday night. The agency said in a news release that flows would begin rising from 3,600 cfs to 5,300 cfs on Monday evening and then increase from 5,300 cfs to 7,600 cfs on Tuesday evening and make the final step to 9,500 on Wednesday.

The volume of water leaving the dam is expected to remain at 9,500 cfs through at least Friday.

For more than two decades, water from Dworshak Dam has been used to help mitigate high water temperatures in the lower Snake River and protect threatened and endangered salmon and steelhead.

The Snake River naturally runs warm during the summer but dams that turned the Snake from a free-flowing river into a series of slackwater reservoirs exacerbate the problem. To compensate, Dworshak is lowered 80 feet each summer as about 2 million acre feet of water is released from deep below the reservoir’s surface between early July and the middle of September. From the dam, the 43-degree water flows into the Clearwater River and hits the Snake River at Lewiston.

Tribal, state and federal fisheries managers work with the Corps to time release of cold Dworshak water with a goal of keeping water at Lower Granite Dam from exceeding 68 degrees. Temperatures in the 70s are considered unhealthy for salmon and steelhead. On Sunday, water at Lower Granite Dam was about 66 degrees.

Air temperatures in the region are forecast to reach triple digits by the end of this week.