Northwest Newspaper Hydropower Articles

The new lure on the Deschutes? A tower

A PGE-backed collector aims to steer migrating fish past the Round Butte Dam

By MATTHEW PREUSCH
Oregonian

MADRAS --Below the rimrock walls at Lake Billy Chinook a ring of black tubes seven stories high and big enough to crawl through rises next to Round Butte Dam.

The tubes will anchor a $90 million tower the dam's owners hope will fix the four-decade failure to get migrating fish past Round Butte and to the sea.

The 440-foot dam on the Deschutes River about 90 miles southeast of Portland is part of the Pelton-Round Butte hydroelectric project.

Jointly owned by Portland General Electric and the Confederated Tribes of the Warm Springs Reservation, the project generates enough electricity each year to supply a city the size of Salem.

When the dam was built 50 years ago, PGE and regulatory officials tried a number of tactics --including an aerial salmon tram and a 2.8-mile fish ladder --to get adult salmon and steelhead upstream and juvenile fish downstream. But by the late 1960s it was clear fish would not return to 226 miles of spawning grounds in central Oregon's upper Deschutes River basin. It's been 40 years since a Chinook migrated past the dam.

As part of the project's recent relicensing agreement the tribes and utility agreed to spend $135 million on fish reintroduction in the upper Deschutes Basin.

Some of that money is being spent on habitat improvement projects to prepare a sort of riparian welcome mat for juvenile salmon and steelhead now being planted in the upper basin.

But the majority --$108 million --will go toward the 270-foot tower and related fish transfer facility to be finished a year from now. If the tower doesn't work as designed, the fish reintroduction will fail.

While the tower, which will be the height of the Portland Plaza building in downtown Portland and almost entirely submerged, draws on existing technology it is also novel among fish passage projects, and therefore risky.

"I think you have to give a lot of credit to PGE for trying this," said Larry Swenson, a hydraulic engineer with the National Marine Fisheries Service in Portland who consulted on the project. "They are really pushing the envelope of what's been done."

Perhaps because of that there is a fair amount of skepticism about whether the tower will actually work, even among those who signed onto the relicensing deal.

"I don't think there's been a huge level of confidence that this thing is a silver bullet. There aren't many in the fish business saying, 'Oh, yeah, it's obvious,' " said Joe Whitworth, director of Oregon Trout, a fish advocacy group.

The tower itself is unique because of the nature of the problem it's trying to solve. That problem has to do with the way the currents of the Deschutes, Crooked and Metolius rivers combine in the reservoir behind the rock-fill dam. Colder, denser water from the Metolius dives below the flow from the other two warmer rivers. So instead of heading downstream, the warm surface water turns up the Metolius arm of the reservoir. Juvenile fish follow.

The new tower consists of three main parts: a submerged base attached to a tunnel that sends water through the dam's turbines; a 40-foot-wide hollow tube reaching from the base to the surface of Lake Billy Chinook; and a fish collection facility topside.

The fish collector will draw up to 6,000 cubic feet of water per second --roughly four times the average April flow of the Tualatin River at West Linn --off the surface of the reservoir and through two V-shaped fish screens.

"They found that with the screens they could get the currents throughout the lake to move down toward the new intake site," Swenson said.

From there the salmon and steelhead fingerlings will be pumped through a pipe into trucks waiting on shore nearby, which will drive them below the dam complex and put them back in the river. The utility estimates that 96 percent of captured fish will survive the trip.

But just how many of the fish heading downstream will find their way to the intake?

"That is the $100 million question," said Oregon Trout's Whitworth. PGE is confident in its ability to alter the flows in the reservoir based on computer modeling it has done of currents, but fish behavior is harder to predict.

"In this case, you are really banking on fish behavior to follow the hydraulic cues and get them where you want them," said Lynn Reese, an Army Corps of Engineers hydraulic engineer who has worked on fish passage projects in the Columbia Basin for three decades but is not involved in the Round Butte project.

A recent Corps review of surface fish collector systems at dams across the northwest found that, in general, fish will follow currents. The worst-performing surface collectors are those that don't match their intakes with the depths and locations where high numbers of juvenile fish concentrate.

So a lot is riding on PGE's computer modeling of currents in the lake.

In the short term PGE expects to capture about half of the salmon and steelhead coming downstream. Their long term goal is 75 percent. If research shows not enough fish are making it into the facility PGE could make changes such as adding a large hypalon curtain stretching from the tower to the shoreline to guide fish in.

PGE hopes that within 15 years it can stop artificially supplementing the salmon in the upper basin.

If the tower works as designed, the tiny salmon fry now being dumped in creeks and rivers upstream of the dam could start returning as full grown fish in a few years.

What conservationists fear is that PGE and the agencies could end up having to repeatedly plant smolt upstream to simulate a self-sustaining fishery.

"To the extent that you have to jack up the artificial propagation so that enough of a critical number gets up into the tower, you're basically still masking the effects of the dam," Whitworth said.

Matthew Preusch: 541-382-2006; preusch@bendbroadband.com

Oregonian
Portland, OR
March 24, 2008

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