Research shows that salmon avoid water that's warmer than 68 degrees. For years temperatures in the Columbia River have exceeded that for brief periods in the summer. But from July 22 to July 28, water temperatures reached at least 70 at four federal dams on the Columbia and Snake rivers that are passable to salmon.
At Ice Harbor, the first dam on the Snake, and at The Dalles Dam on the Columbia, water temperatures surpassed 70 during the entire week.
And it's not only the reservoirs behind the eight major dams between Idaho and the Pacific that are getting warmer. Temperatures in the Salmon River at Whitebird reached 75 degrees in July. On the Middle Fork of the John Day River in east-central Oregon, temps rose to 78 degrees and 183 chinook salmon were found dead, Oregon fisheries officials said.
Retired Idaho Department of Fish and Game biologist Bert Bowler can't remember a time when the Salmon River got so hot. Temperatures in the Columbia have risen more than 2.7 degrees in the last 50 years, and climatologists say that trend will continue.
"That's scary stuff," Bowler said. "The disturbing part is it's coming much quicker than people thought."
When water temps rise above 68, cold-water species suffer stress and reduced reproduction, and become more vulnerable to disease. In cases where water temperatures reach 80 degrees gradually, salmon have been known to adapt. But when the change happens quickly - as it did in the John Day - fish can die.
COLD WATER FROM IDAHO
Idaho's endangered salmon face many obstacles and dangers, starting at 6,500 feet above sea level and migrating almost 900 miles to and from the Pacific Ocean.
They leave the Salmon, Clearwater and Snake rivers and are swept by the current out to the ocean. From there they travel thousands of miles through the habitat and ecosystems of many species - including humans. Climate change is altering all of these habitats in ways scientists are only beginning to understand.
For 20 years, the U.S. Army Corps of Engineers has released cold water stored at Dworshak Reservoir on the North Fork of the Clearwater River to cool the Snake River and aid migrating salmon. This infusion has aided Idaho's returning salmon, especially its summer-migrating sockeye and steelhead.
But this year, low winds and especially high temperatures caused the reservoir behind Lower Granite Dam on the Snake in Washington just downstream of Lewiston to "stratify" - colder water dropped below the warm water at the surface, where intakes for the dam's fish ladders are located.
Hundreds of endangered Idaho sockeye and Chinook salmon were trapped by the warm water.
Engineers from the Army corps and state fisheries biologists tried to get the fish over the dam and were even ready to trap and haul them, said Russ Kiefer, an Idaho Department of Fish and Game staff biologist.
But they couldn't get cool water into the trap to catch the fish. And with warm temperatures in the Lower Salmon, they weren't convinced the fish would survive once they'd been released.
Eventually, a combination of adjusting turbines and auxiliary pumps got the cooler waters into the ladder and the salmon crossed the dam on their own.
Kiefer praised the cooperative efforts of dam managers and the states. "I think we've got them moving again with the changes we've made," he said.
FEW OPTIONS FOR SOME FISH
Sockeye salmon are listed as endangered, other salmon as threatened.
Throughout the Columbia River system, springs and tributaries bring cool water into the migration route that provides a refuge for the fish. But the clock is ticking, especially for salmon.
The longer and harder the migration is, the more fish die before they return to their spawning grounds. Steelhead can wait until the winter to migrate because they don't spawn until spring.
But the sockeye and some chinook spawn in the summer and fall.
"They have two choices: They either have to plunge through these conditions or wait it out," said Ritchie Graves, a National Marine Fisheries Service biologist in Portland.
Graves said there are signs that some salmon, including Idaho's Snake River fall chinook, are already changing the timing of their migration to avoid the hottest periods. The artificial cooling from Dworshak contributes to the changes.
"These fish are adaptable," Graves said. "You give them conditions like cooling the river and if they can make a go of it, they'll try it."
Idaho's quality spawning and rearing habitat in its pristine central mountains, largely protected as wilderness or with roadless laws and rules, becomes even more critical to the survival of salmon in the entire basin.
"This high-elevation habitat we have in northeast Oregon and Central Idaho is going to be very important," Kiefer said.
For more than a decade, environmentalists have pointed to the slower-moving waters in the reservoirs behind dams as the culprits in increasing the temperatures in the Columbia River. But the warm water in Idaho's Salmon River is not caused by a dam. On the Snake, environmentalists have urged Idaho Power to modify Brownlee Dam to bring cooler water up from the river's bottom and over the dam in the fall, when flows are particularly warm.
One thing is certain: Dworshak's cold releases will be more critical than ever to the survival of Snake River runs.
Rocky Barker: 377-6484