July 31, 2010 - Bend Bulletin - Fish intake confounds anglers
Aug 30, 2010
Fish intake confounds anglers
Goal is to bring Lower Deschutes closer to pre-dam days; fishing guides say warmer water caught them off guardBy Scott Hammers / The Bulletin
Published: July 31. 2010 4:00AM PST
Lifelong Maupin resident and fishing guide Nate Morris has long considered himself an authority on the ways of the river that runs through his hometown —until this year, that is.
With the activation of a new fish transfer facility in April at the Round Butte Dam on Lake Billy Chinook, temperatures on portions of the Lower Deschutes River are up 2 to 5 degrees over the historical average.
The Round Butte project is part of an effort to return river conditions to the way they were before the dam was built in 1964, including elevated water temperatures in spring and early summer and cooler temperatures in late summer and fall.
Warmer temperatures in recent months have disrupted the once-predictable hatching of aquatic insects, a primary food source for fish in the Lower Deschutes, leaving anglers and guides like Morris unsure when and where the
fish will be biting.
“People come from all over the world to fish the Lower Deschutes,” Morris said.“I had some guys showing up from back east on June 10, and I had to tell them there weren't any bugs left. ... As a guide who's making my living out here being an expert on the river, it can make it a bit difficult.”
A project of Portland General Electric and the Confederated Tribes of Warm Springs, the $110 million fish and water intake at Round Butte Dam was conceived as a way of bringing back chinook and steelhead that once migrated up the Deschutes, Crooked and Metolius rivers before the dam was built.
Until the fish passage was activated, all water that passed downstream from the dam had been drawn from the bottom of Lake Billy Chinook, between 220 and 260 feet below the surface. With the completion of the fish transfer facility — where migratory fish headed downstream are captured and trucked around the dam — a second water intake was added, drawing in water from the surface down to about 45 feet deep.
Like a sink with hot and cold taps, the two water intakes allow PGE to adjust the temperature of the water it sends downstream by blending warmer water from the shallows with cooler water from the bottom of the lake.
Learning the blends
Don Ratliff, senior biologist with PGE, said the construction of the dam delayed the natural cycles of warming and cooling that would have happened in the undammed river. Water stored through the winter and spring created coolerconditions downstream when it was released in spring and summer, he said, while sun-warmed lake water stored in summer created warmer river conditions when it passed through the dam in late summer and early fall.
Using historical data and temperatures measured at Lake Billy Chinook and downstream, scientists working with the dam operators calculated how temperatures would likely fluctuate through the year had the Round Butte Dam
never been built. With additional computer modeling, the team developed “Blend 17,” a pattern of timed openings and closings of the gate on the deep water intake to achieve the target temperature.
It has been a learning process so far, Ratliff said. A week ago, warmer-than projected temperatures were observed at the Madras gauging station downstream from Round Butte, and the dam operators decided to make an unscheduled adjustment to the blend. The dam's computers were reprogrammed to shift from drawing 15 percent of water from the bottom of the lake to 19 percent.
Because the computer system is programmed to manage flows month-to-month, it overcompensated, opening the deep water intake all the way to try to bring the deep water portion of the July flow all the way up to 19 percent with just over a week left in the month.
In two days, the temperature at the Madras gauging station dropped almost five degrees before dam operators could correct the error.
Ratliff said it's theoretically possible for PGE to adjust the downstream water temperature to benefit one species or another, but probably not desirable.
“The problem with that is it's a real complex ecosystem,” he said. “What you're trying to do for something you see or perceive as a problem, may be a negative for something you didn't even think about.”
Amy Stuart, the Deschutes Watershed Manager with the Oregon Department of Fish and Wildlife, said she's heard some of the concerns from anglers about the potential for warmer waters to damage fish runs, but so far, her agency's biologists have been finding healthy fish throughout the Lower Deschutes this season.
“We're not seeing any kind of apparent change in mortality or disease or biological issues,” she said. “A lot of it seems to come from the public; we probably didn't do a very good job of telling them what to expect.”
Great fishing, no clients
Guide Steve Light from Fly & Field in Bend said he knew the changes were coming this year, but warmer water conditions still caught him by surprise. Stoneflies and salmonflies began hatching on the Lower Deschutes in early May, he said, two to three weeks earlier than in past years.
“In all honesty, we weren't completely prepared for it,” Light said. “We had two weeks where the fishing was phenomenal, and we really had no clients booked.”
Light said the new system could have a positive effect on fishing on the Lower Deschutes, provided dam operators can achieve the same year-to-year consistency in water temperatures seen in the past.
Much of the concern about higher temperatures comes from conditions at the mouth, where the Deschutes joins the Columbia River near The Dalles.
Temperatures at the mouth are key to the success of steelhead runs. Unless the Deschutes is running cooler than the Columbia River, hatchery steelhead generally will not make the right hand turn toward Central Oregon, but will instead continue on in search of cooler spawning grounds further up the Columbia system.
Morris said he's noted “extremely abnormal” water temperatures up to 72 degrees near the mouth in July, and suggested ODFW might want to consider shutting down fishing in the area if temperatures don't drop soon.
Measuring the mouth
Morris said he's taking a wait-and-see approach to how efforts at Round Butte Dam ultimately affect fishing downstream.
“I'm willing to let it run its course and see where it goes, but August is going to be a big determining month,” he said. “I'll be up in arms if we're dealing with 70 degree temperatures through August.”
Stuart said her agency's measurements of temperatures near the mouth are in line with historical trends. Any adjustment to water temperatures at Round Butte Dam would be undetectable by the time the river reaches Mack's Canyon, about 24 miles above the mouth, she said, simply due to sun warming and springs feeding into the river.
The Columbia is running cooler than usual this year, Stuart said, which could potentially depress steelhead runs on the Deschutes.
Light said he's still has reservations about the Round Butte project, and thinks there are any number of ways $110 million could have been better spent to improve fisheries, from buying up water rights to piping irrigation canals.
Ideally the project could extend the fishing season by a few weeks, he said, but if it fails, whole communities could be upended by the deterioration of fish stocks.
“When we have a good run in the Deschutes River, our shop is busy, the Maupin shops are busy,” Light said. “When people are out catching steelhead, they're staying in hotels, they're eating in restaurants, they're spending money.”
Scott Hammers can be reached at 541-383-0387 or at firstname.lastname@example.org.
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