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Economic and dam related articles

Working Weirs

by Editorial Board
Tri-City Herald, October 29, 2007

(Andy Porter/Union Bulletin) A 1,000-ton removable fish weir is guided into the navigation lock at Lower Monumental Dam late Tuesday afternoon. The weir arrived from Portland and will be installed in coming days. Phase three of a Snake River success story should slip into action this spring.

It's the third huge weir to be installed on the Snake River to help juvenile salmon pass the dams.

The first was installed at Lower Granite Dam in 2001 and the second at Ice Harbor Dam in 2005.

The new 2 million-pound weir, fabricated in Portland, was barged up the Columbia and Snake rivers, through the locks and up to Lower Monumental Dam this past week.

Fish going downriver are guided away from the dams' turbines by the weirs and exit through the spillway.

Research indicates fish survival has increased where the weirs are installed.

The survival rate of fish passing through the gates at Lower Granite Dam has risen from 93 percent to 98 percent, said Cory Rahn, project manager for the Army Corps of Engineers.

"At Ice Harbor Dam, we have seen slight increases in spillway survival for the spring out-migration and about a 2 percent increase in survival for the summer fisheries," he told the Herald.

These might ordinarily be seen as marginal increases, but when Northwest salmon are involved, every improvement is important.

With some environmentalists wanting dams breached to save more fish, no matter the cost in lost power production or increased greenhouse gas emissions, the dams must be made as neutral a factor as possible in fish survival.

These weirs are good investments, whether seen from the viewpoint of transportation, energy production, protecting irrigation or through the eyes of the fish.

Editorial Board
Working Weirs
Tri-City Herald, October 29, 2007

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