By TERENCE CHEA
Associated Press Writer

SAN FRANCISCO (AP) -- A federal judge ruled Tuesday in favor of Central Valley farmers and urban water agencies seeking to loosen restrictions on pumping from the Sacramento-San Joaquin Delta, a major source of irrigation and drinking water for much of California.

U.S. District Judge Oliver Wanger in Fresno said the federal government did not properly develop a management plan that restricted water exports to protect endangered salmon, steelhead and other fish.

The judge scheduled a hearing Wednesday to determine how much water can be exported without harming threatened fish that migrate through the delta to the Pacific Ocean.

Groups representing San Joaquin Valley farmers and Southern California water users filed suit to block the pumping restrictions imposed by the 2009 management plan written by the National Marine Fisheries Service.

The restrictions were aimed at protecting winter- and spring-run chinook salmon, Central Valley steelhead, green sturgeon and a group of orca whales.

Judge Wanger said pumping restrictions were necessary to protect those species, but the agency did not adequately explain how they determined specific pumping levels.

Judge Wanger said pumping restrictions were necessary to protect those species, but the agency did not adequately explain how they determined specific pumping levels.

"The exact restrictions imposed, which are inflicting material harm to humans and the human environment, are not supported by the record," Wanger wrote in the 134-page ruling, calling the restrictions the "product of guesstimations."

The restrictions -- along with three years of drought -- have forced farmers to leave large tracts of land fallow, leading to significant economic losses and soaring unemployment in many agricultural communities, said Sarah Woolf, a spokeswoman for Westlands Water District, which serves about 600 farms in western Fresno and Kings counties.

Environmentalists, fishermen and tribal communities that defended the water management plan in court were disappointed by Tuesday's ruling, said Doug Obegi, a staff attorney for the Natural Resources Defense Council.

"We will urge the court to uphold these protections for salmon and the fishing and tribal communities that depend on them," Obegi said. "Weakening those pumping restrictions will jeopardize those species."

Officials with the National Marine Fisheries Service were still reviewing the ruling and declined comment, spokesman Jim Milbury said.

Wanger is also expected to issue a ruling on a similar lawsuit that seeks to block a 2008 management plan that imposed pumping restrictions to protect a tiny endangered fish called the delta smelt.