Silver lining in muddy dam project is more fish in the rivers.

Byline: INSIDE THE OUTDOORS By Mike Stahlberg The Register-Guard

Every dark cloud has its silver lining. Even those clouds of muddy water that came billowing out of Cougar Lake during the spring of 2002, turning the pristine McKenzie River into the world's largest iced latte.

That was the year the U.S. Army Corps of Engineers drained Cougar Lake to provide access to the face of the dam for construction crews installing "temperature control" facilities.

As the reservoir was being emptied, the dammed portion of the South Fork McKenzie River began meandering through thick layers of silt that had accumulated on the reservoir bottom over the previous 40 years.

Brown muck picked up by the flowing water was carried through the drainage tunnel in the dam. From there it flowed into the mainstem McKenzie, creating a muddy mess just in time for the opening of the 2002 trout season.

Turbidity levels in the McKenzie, once gin-clear, shot through the roof. Not only was the McKenzie coffee- colored but its flow muddied the Willamette and Columbia rivers.

By June of 2002, the McKenzie was no longer brown. But it was still discolored, running a deep greenish hue that reduced visibility in the water to a couple of feet.

Fishermen and other recreational users were angry. The turbidity of the river became so severe that the Corps stopped lowering the reservoir sooner than planned.

In an editorial, this newspaper chastised the Corps for creating "muddy water conditions that caused river recreation to plunge, threatened fish and other wildlife and caused local residents to refer to the `McKenzissippi.' '

So where's the silver lining in that?

Well, it's swimming in the Willamette River and its tributaries right now - in the form of one of the three biggest runs of silvery summer steelhead in history.

The size of that returning run was very likely boosted - inadvertently, but significantly - by all the "McKenzissippi mud."

The theory is that high turbidity helped increase smolt survival rates by making it difficult for predators to see the 5- to 6-inch long steelhead smolts as they migrated down the McKenzie, Willamette and Columbia rivers to the Pacific Ocean during April and May 2002.

It's a theory that meshes well with research that shows the greatest single factor in winter steelhead returns is the amount of water flowing in the rivers during the out-migration of smolts.

High, cold water minimizes disease. It also speeds the smolts' journey to the sea, reducing their exposure to inland predators.

It stands to reason that high, cold, and off-color water, like we saw in 2002, would be just that much better for smolt survival. Salmon and steelhead, of course, evolved with high, muddy spring flows to help their out-migration. Construction of 13 dams helped control flooding and reduce turbidity.

In any event, those tiny steelhead that went to sea in a cloud of mud two years ago are coming home as fat adults, and in surprisingly large numbers.

More than 20,000 of the sea-run rainbow have been videotaped swimming through the Willamette Falls fish passage at Oregon City.

The steelhead tally at Willamette Falls by late May was already larger than the final count for 25 of the past 35 years.

Based on the May counts, state fish biologists estimated that somewhere between 30,000 and 38,000 summer steelhead would return to the Willamette Basin this summer. Only three times since summer steelhead counts began in 1970 has the tally exceeded 30,000, the record being 40,719 fish in 1986.

As a result, they recommended that the bag limit be raised to three adiplose fin-clipped steelhead per day. More silver, in other words, to line anglers' creels.

Meanwhile, work on the Couger Dam temperature control project is slated to be completed in time to allow the reservoir to be refilled next spring. If the system works as designed, it will produce another silver lining - in the form of increased spring chinook salmon production in the McKenzie River.

Mike Stahlberg can be reached at [e-mail].