PORTLAND — A federal judge indicated yesterday that he is leaning toward greatly increasing the amount of water spilled over four dams on the lower Snake and Columbia rivers to help threatened and endangered salmon migrating to the ocean.

U.S. District Judge James Redden issued his preliminary finding in a statement filed just two days before a scheduled hearing to determine how dam operations should be changed in the wake of his rejection of the Bush administration approach.

Environmentalists, Indian tribes and fishing groups argue that if the spill is not increased, salmon could face extinction.

Government officials counter that the extra spill is unnecessary and will cost electricity customers up to $100 million in a drought year. When the water is spilled, it does not pass through the dam's turbines — helping young fish survive but missing a chance to generate electricity.

A lawsuit by environmentalists, Indian tribes and fishermen resulted in a ruling that the Bush administration plan for operating Columbia Basin hydroelectric dams violated the Endangered Species Act.

Last month, Redden rejected the Bush administration's $6 billion plan to install special fish slides to improve the survival of young salmon passing over the dams, and other measures, such as habitat improvements. On Friday, Redden will hear arguments on how the dam operations should be changed now that the government's biological opinion has been struck down.

Redden indicated he is not likely to leave in place the 2004 biological opinion he rejected while it is fixed — but he does not want to leave federal agencies liable for not having a plan and wonders whether it is feasible to reinstitute a version from 2000.