Severe drought is forcing dam operators in the Northwest to choose electricity generation over salmon. Under an emergency order issued last week that is expected to last much of the year, the Bonneville Power Administration is using what water remains to spin turbines to generate power on the Columbia and Snake rivers, overriding Endangered Species Act requirements to spill water over the tops of dams to help young salmon migrate downstream. Brian Gorman of the National Marine Fisheries Service says the shift will increase salmon mortality by about 15 percent, while some environmentalists say the figure could be as high as 95 percent. Yesterday, the BPA predicted a 250 percent increase in power rates unless energy conservation efforts took off and aluminum smelters idled themselves for two years.