Corps Fights Birds at John Day Dam
by Bill Rudolph
NW Fishletter, June 19, 2009
The U.S. Army Corps of Engineers shut down operation of their temporary spillway weirs at John Day Dam June 4, after efforts to reduce smolt predation by gulls below the dam failed to deter the ravenous avian predators.
The Corps had strung wire across the tailrace this year to deter the birds from feeding there, a state of affairs that came to light last year when the two weirs were first placed in spillway bays for testing.
As for the weirs, which are designed to corral migrating smolts and send them over the top of the spillway, "They work too good," said Corps' spokesman Mike Langeslay.
He said the weirs concentrated smolts in such a narrow band in the tailrace below the dam that it has created a great feeding area for the gulls, which are believed to come from large landfills in the vicinity, where urban centers like Seattle haul their garbage in by the trainload.
Langeslay said some crucial wires in the array, which were hanging too low over the water, broke when they were tightened. What remained of the new avian wire array didn't deter the birds.
The Corps tried pyrotechnics, and buzzed the gulls with model planes and helicopters, but the gulls remained undeterred.
Now the Corps has shut down the weirs and is spilling 30 percent of the river flow 24 hours a day, in a bulk pattern that spreads out the smolts in the tailrace, which officials figure is reducing the birds' success rate.
Langeslay said the Corps will be losing this year's test of the temporary weirs. However, he said, the agency has been pleased with the overall performance of the TSWs, which should help reach the new BiOp's survival objectives for fish passage at John Day Dam.
Next year's migrating smolts should find even more help passing the dam. By then, along with a new avian array, an extended-length spillway deflector should be in place to control "edge effort" south of the spillway, said Langeslay.
Currently, there exists a dead zone in the tailrace flows below two skeleton bays where no turbines are in place and predators like pikeminnow like to congregate.
Last year--when the TSWs were first tested--PIT-tagged smolt data seemed to show considerably less survival below the dam than in other recent years. It's still an ongoing puzzle for researchers, since PIT-tag survival above the dam added up to more than 100 percent.
Langeslay said survival of acoustic-tagged fish last year did not agree with the PIT-tag results. He said the questionable results seem to point to the likelihood that one or more assumptions of the PIT-tag study had been violated. There are no results in yet this year for acoustic-tagged fish.
In a June 2 letter to Redden, the Corps spelled out 2008 summer hydro operations and cautioned the Court they might be shutting down the TSWs at John Day over the avian predation issue.
Both sides in the litigation have agreed to maintain Redden's previous court orders on flows and spills until some final settlement is reached, though in their latest missive, the feds said they had significant reservations about implementing actions outside operations agreed upon by most regional players in the 2008 BiOp.
But plaintiffs argued last week that the proposed 2009 summer operations still shortchanged the fish.
In a June 10 letter to the judge, environmental and fishing groups, the state of Oregon, and the Nez Perce Tribe panned the feds' decision to follow the 2008 BiOp's call for taking less water from Montana's Libby and Hungry Horse reservoirs in the wettest 80 percent of all years. They said it meant more than a 20-percent reduction in summer flow augmentation.
Several years ago, an independent science panel decided the change in drafting Montana's largest reservoirs made sense, since it had an unmeasurable impact on flows at McNary Dam, and improved conditions for resident fish in Montana.
Even though the feds have promised to spill through the end of August, the BiOp plaintiffs criticized the feds' wish to implement the BiOp's call for an early cutoff of summer spill if juvenile fish numbers fall below 300 a day for three days in a row. Otherwise, the summer spill would continue through Aug. 31, regardless of the number of migrating fish passing the dams.
On June 10, Redden approved the federal plan for summer hydro operations, which calls for the same spill levels he had ordered in recent years.
learn more on topics covered in the film
see the video
read the script
learn the songs