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With a Concrete Wall, Researchers Improve
Migrating Salmon Survival Rates at The Dalles Dam

by Quinton Smith
The Oregonian, December 10, 2010

(ACOE) A concrete wall at The Dalles Dam has raised the survival rate of migrating juvenile chinook and steelhead. The wall, about the length of three football fields, directs fish to pass into the deeper part of the river, away from predators There were fish problems at The Dalles Dam.

Too many young salmon and steelhead migrating down the Columbia River each spring and summer never made it past.

A federal salmon plan that governs the dams on the Columbia says from 93 percent to 96 percent of endangered juvenile salmon and steelhead must survive a dam's spillways, turbines and sluiceway. At The Dalles, river currents pushed millions of migrating fish into shallow water below the dam and into the path of hungry predators. Not enough survived.

The stakes -- and cost -- of ensuring greater fish survival on the Columbia and Snake river systems increased dramatically in 1991 after most of the salmon and steelhead runs were listed for protection under the Endangered Species Act. Since then, dam operators and power marketers spend millions each year studying dam operations and then trying to improve them. Which brings us back to the gates of The Dalles Dam. In 2004, The U.S. Army Corps of Engineers, which operates nine dams on the Columbia and Snake rivers, built a 150-foot wall below spillways No. 6 and 7. They hoped to steer salmon and steelhead into the deeper, north edge of the river and away from predators.

Still, too many fish got pulled into shallow water.

"Survival from that was not what we hoped for," says Brad Eppard, a corps biologist in Portland.

It was back to the drawing board.

They looked at eight ideas, including a giant steel structure above the dam to block fish from the powerhouse and sluiceway, and direct them into the northernmost spillways. But navigation issues stymied that plan.

They went back to the drawing board.

Corps biologists wondered if a much longer wall between spillways 8 and 9 -- where 40 percent of all spill occurs -- would better guide young fish to deeper water and away from predators. Eppard and others made trips to the corps' research headquarters in Vicksburg, Miss., where scale models of each of its dams are kept.

Biologists, hydrologists and engineers stood below spillways of the 2-foot high model "and tried things" with sandbags, then ran water through the model, Eppard says.

"We tried to come up with a way," he says, and they tested and watched. "If we do this, what happens; if we do that, what happens?"

A much longer wall had possibilities.

Engineers built a more precise plexiglass wall, then did flow studies with dyes. The corps solidified the plan and ran it by other federal and state fish agencies.

It was a go.

Crews at the actual Dalles Dam began to build a concrete wall in fall 2008, stopped for the high-water months, then finished last spring for the annual out-migration of young salmon and steelhead.

The new wall is 10 feet wide and 850 feet long -- nearly the length of three football fields. Anchored to the long concrete floor below the dam, it cost $51 million.

And it seems to work.

A study conducted this spring and announced last week showed remarkable results: 96 percent of spring and summer chinook successfully passed The Dalles Dam this year, up 4 percentage points over similar tests. The study found that 94 percent of fall chinook survived the dam, up 7 percentage points, and that 95 percent of juvenile steelhead survived. The corps does not have previous rates for steelhead survival at The Dalles.

The wall, says Eppard, gets migrating chinook and steelhead into deeper water faster "and gives them a better chance."

"The dam was one of the poorer actors," Eppard says. "Now it's up with the best."

Biologists for the National Oceanic and Atmospheric Administration, the federal agency that shares responsibility for implementing the Endangered Species Act, likes the results as well.

"It's nice to see it work," says Gary Fredricks, an NOAA senior fish biologist in Portland. "We hope this is one dam we can take off the 'to do' list.

"These are big dams and they take big fixes," he adds.

And big money to pay for them. The $51 million project split the cost over two years. It is the second largest project since the mid-'90s in the corps' Columbia River fish-mitigation program, a construction account that pays for fish-passage improvements at Columbia and Snake River dams. In 2009-10 the program budget was $85 million. The Bonneville Power Administration, which markets the power from hydroelectric dams, repays the federal government for the corps' program with revenue from consumers.

The Dalles Dam was a problem for juvenile salmon because it is the only corps-run dam on the lower Columbia or lower Snake rivers without a bypass system for the young fish. Mike Langeslay, manager of the corps' mitigation program, says the agency tried different ways and times of spilling water over its 23 bays and through its 22 turbines in the 1990s. Then in 2000 it started spilling water during fish-passage months only through the northern eight bays, he says, but the change wasn't enough.

Next year the corps will install an array of wires below The Dalles Dam to keep seagulls and other birds away from the salmon, which could improve survival rates even more, Fredricks says.

Also next year, the corps will retest juvenile salmon and steelhead at The Dalles, and for the first time, test if Bonneville and John Day dams meet federal requirements after recent improvements.

"When we meet these numbers we're not finished," Langeslay says. "There's still a lot more to be done."

Related Pages:
Underwater Acoustic Tags Help Salmon Avoid Becoming Dinner by Andrew Nusca, Smart Planet, 1/28/10
Acoustic Tags Track Movement of Salmon Through Dams by Matthew Preusch, The Oregonian, 7/29/9

Columbia predation, by the numbers

Each year the Northwest Region of the U.S. Army Corps of Engineers has researchers it supports attend a symposium to report on their work. Last week in Portland, researchers reported on 59 studies on everything from salmon predation to lamprey migration. Some highlights:

Related Sites:
Anadromous Fish Evaluation Program Annual Review 2010 Lower Columbia River Survival Studies

Quinton Smith
With a Concrete Wall, Researchers Improve Migrating Salmon Survival Rates at The Dalles Dam
The Oregonian, December 10, 2010

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