PORTLAND - Juvenile chinook salmon need a more stable flow of water through the upper Columbia River system to improve their chances of surviving their migration to the sea, according to a preliminary review by an independent panel of scientists.
The data suggest that power generation at hydroelectric dams causes river levels to slosh up and down, much like the disturbance caused by children playing in a bathtub, confusing the juvenile fish with shifting currents while they try to find their way downstream, the scientists said.
"If you were a salmon smolt and the river flow was reversing every couple of hours, it would be pretty confusing," said Charles Coutant of the Independent Scientific Advisory Board.
More study is needed, but the data indicate that juvenile fish passage and survival could be improved along the lower Snake River with better water flow management even when river levels are low, Coutant told the Northwest Power Planning Council on Wednesday.
But council members said there may be little managers can do to control water levels if the light snowpack and relatively dry winter leave the region with another drought this summer that limits hydroelectric generation.
"We have to see if the problem is solvable or not and still keep the lights on," said Frank L. "Larry" Cassidy Jr., a council member from Washington state.
The council last November asked the scientific board to review efforts to occasionally boost river flow levels to improve salmon smolt migration to the Pacific Ocean. The council represents Idaho, Montana, Oregon and Washingon with two members from each state charged with balancing fish conservation with regional energy needs.
Coutant also told the council that conventional wisdom may be wrong about the "pulsed flow" theory of flushing young salmon out of reservoirs with high flows for short periods.
"The pulsing idea is pretty much discredited," Coutant said.
The review did not cover other issues such as barging young salmon past dams or examine factors such as water temperature, turbidity or gas saturation - all areas that need more study and data, Coutant said.