Since 1988, the Bonneville Power Administration (BPA) in the US has annually regulated the flow from the six dams downstream of Grand Coulee Dam, in order to save Chinook salmon at Vernita Bar.
BPA, however, has to operate the dams by foregoing their optimized operation for power production. Last year nearly 600 salmon redds, nests containing fertilized eggs, were counted in the upper protection level of Vernita Bar, 20 per cent more than in 1996.
Vernita Bar is located in eastern Washington about four miles downriver from Priest Rapids dam. It represents nearly 40 per cent of all the spawning in the Hanford Reach, one of the last free-flowing stretches of the Columbia River. The flow regulation in this reach of the river is carried out starting in mid October and continues through the third weekend in November.
The flow regulation was agreed on when it was noticed in the 1970s that adult salmon which spawn during the day, had tended to build their redds high on the Vernita Bar, due to the high water levels at this time – caused by high power generation releases. Unfortunately, at night, when power demands dropped and flows went down, the redds containing salmon eggs were left exposed and dried out.
To ensure the safety of the salmon, BPA agreed with other river users to regulate the flows so that the fish would build their redds, where they would remain submerged, until all the eggs hatch sometime between mid-April and late June.
These regulations, formally adopted as the Vernita Bar Agreement in 1988, reverse the pattern of high day time flows and low night time flows by regulating flows from the six dams below Grand Coulee.