Science justifies California water limits-report

* Environmentalists welcome findings for sake of fish

* California river delta at center of state's water fight

* Report won't end controversy or California water woes

By Dan Whitcomb

LOS ANGELES, March 19 (Reuters) - Federal limits on water that can be pumped out of a major river delta for California farmers are scientifically justified, a much-anticipated report said on Friday, a finding hailed by environmentalists in the state's epic water wars.

But the National Academy of Sciences stopped short of handing a decisive victory to environmental interests over agricultural interests. The academy said further study was required and that threats to Chinook salmon, delta smelt and other endangered fish were not entirely caused by the pumping.

"The Academy of Sciences report clearly validates the biological opinions," Ann Hayden, a senior water resource analyst for the Environmental Defense Fund, said of regulations devised under court order by federal wildlife biologists and issued in late 2008.

"It's time to stop pitting the economic interests of farmers against fishermen and move forward to find solutions," Hayden said. "We have pushed the Bay-Delta system to the brink of collapse and saving it -- and the jobs that depend on it -- is going to require increased cooperation among all interests."

The Sacramento-San Joaquin Delta is at the center of California's long-running tug-of-war over water, which has become increasingly testy during a three-year drought that led to rationing, higher charges for water and mandatory conservation measures across the state.

Dramatic cutbacks in water deliveries by the U.S. Bureau of Reclamation and state Water Resources Department have idled thousands of farm workers and large swaths of farmland. The crisis prompted U.S. Senator Dianne Feinstein, a California Democrat, to propose easing the environmental restrictions to allow the pumping of more water for growers.

Feinstein came under fire from environmental activists, fishing groups and even members of her own party. She dropped the plan after state and federal agencies, citing a series of strong winter storms that may signal the end of the drought, announced they will supply farms considerably more water this year than last.

Lawmakers have said they would await the National Academy of Sciences report, which was ordered by the Obama administration, before making further policy decisions.

On Tuesday U.S. Interior Secretary Ken Salazar said that irrigation districts south of the delta, which represent farmers on the west side of the state's fertile Central Valley, will get 25 percent of their contracted water allotment from the Bureau of Reclamation, up from just 5 percent in February.

The increase was issued ahead of schedule and comes at a critical time for the Central Valley, one of the country's most bountiful agricultural regions. California, the No. 1 farm state, produces more than half the fruits, vegetables and nuts grown in the United States.

Meanwhile, the state water agency boosted its allocation for all users to 15 percent, up from 5 percent last year.

The state supplies more than 25 million people and more than 750,000 acres (300,000 hectares) of farmland with water from the delta.

(Editing by Steve Gorman and Bill Trott)