Federal biologists forecast a big increase in salmon returns to two rivers that have returned stingy catches for Oregon and California fishermen in recent years.  The biologists say more water for fish and an upturn in the cyclical supply of food in the Pacific Ocean is largely responsible for improved runs in the Klamath and Sacramento Rivers. The Pacific Fishery Management Council forecasts 1.65 million adult Chinook salmon for the Klamath River and almost 820,000 for the Sacramento. The Klamath expectations are more than four times higher than last year.