Taking out the Klamath River's dams would cool the river in the fall and warm it in the spring, a shift that may or may not help chinook salmon, predicts a paper by U.S. Geological Survey scientists.

It is not an unexpected result. Reservoirs store water and heat, warming and cooling slower than a river would naturally, the paper reads.

Taking out the four hydropower facilities below Link River Dam on Upper Klamath Lake would allow the river to quickly cool in chilly fall temperatures as tens of thousands of chinook salmon are pushing upstream to spawn, according to the paper's authors.

It would also create warmer conditions in the spring. While the paper postulates that would harm growing young chinook, it also admits that it could help speed their development, generally an advantage for fish.

The paper was submitted to the Federal Energy Regulatory Commission, which is overseeing Portland, Ore.,-based PacifiCorp's dam relicensing request.

Removing the dams would also make more of the river hospitable to spawning salmon in the fall, the scientists found. That could keep an additional 50 kilometers of river below the temperature threshold for spawning salmon and incubation of eggs in the fall.

That does not include habitat that would be opened up above Iron Gate Dam, a barrier which blocks all migrating fish, said USGS author John Bartholow.

The stretch of river most likely to experience a change is Seiad Valley, upstream from Happy Camp. That's because flows from warm, shallow Upper Klamath Lake can at best provide 48 percent of the water to that reach, which has few unmanaged tributaries, the scientists wrote.

The prediction it is only one take in a barrage of complex questions being asked about the Klamath's dams as part the relicensing process.

While important, water temperatures may affect salmon more or less than the exceedingly poor water quality in the reservoirs. The dams also may act as settling pools for nutrients coming downstream -- including from massive algae die-off in Upper Klamath Lake -- a benefit according to PacifiCorp. They also prevent sediment from above the dams from moving downstream.

Asked to relate the importance of water temperature to these other factors, Bartholow said that work is in progress.

"To answer that would be speculative," Bartholow said.

The paper has yet to be published, and Bartholow said some changes may be made before it is.

PacifiCorp spokesman Jon Coney said the paper and the company's work show the same thermal lag caused by the shallow reservoirs, as well as the result that Iron Gate Reservoir isn't big enough to be used to influence water temperatures. He said PacifiCorp's water quality and water temperature studies are now being applied to fish, including coho salmon and steelhead.

"One thing we've tried to emphasize is that water quality modeling shows that it (removal of the dams) could be potentially worse," Coney said.

It's hard to imagine.

In a request for more studies on the dams' impacts, the California State Water Resources Control Board lodged this observation: A scientist was using equipment to locate fish in Copco Reservoir in October 2003. A low-pressure system blew in, and the wind picked up. The scientist "observed a massive release of gasses from the bottom of the reservoir that turned the surface of the reservoir to foam."

The reservoir's fall turnover, when its warm upper layer cools and sinks, may suspend nutrients and organic matter trapped during the summer months and flush them in huge quantities downstream, the board's memo reads.

Mike Belchik, senior fisheries biologist for the Yurok Tribe, added fish passage to the problems that may harm salmon runs more than water temperature. But he said the earlier rise in temperature predicted by Bartholow and others may accelerate the hatching of fish eggs and juvenile fishes' growth. That could get young fish out of the river faster, away from many predators and increasingly warm temperatures.

"This is an effect that the dams are having," Belchik said. "This is an effect that needs to be mitigated.