LOS ANGELES (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.

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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.”

A spokesman for the California Farm Bureau Federation said the report showed the need for “better justification of water restrictions” and that there were flaws in the Endangered Species Act.

THREE-YEAR DROUGHT

“We believe the government must do a better job of managing the delta pumps, to make more water available for people while still protecting the fish,” said Paul Wenger, president of the California Farm Bureau Federation.

Wenger also singled out the study’s conclusion that a number of factors, including sewage treatment plants and non-native fish, represented a threat to the protected species.

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 would 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 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.

The state water agency also 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 of farmland with water from the delta.