SAN FRANCISCO (CBS SF) – A citizens’ group dedicated to restoring the now-flooded Hetch Hetchy Valley in Yosemite National Park has sued the city of San Francisco in a bid to change the way water is diverted from the Tuolumne River.

The lawsuit was filed in Tuolumne County Superior Court by the Oakland-based group Restore Hetch Hetchy on Tuesday.

The 9-mile-long glacier-carved river valley was flooded in 1923 when the city of San Francisco built the O’Shaughnessy Dam to create the Hetch Hetchy Reservoir.

The action was authorized by the federal Raker Act, enacted by Congress in 1913, which gave San Francisco rights to Tuolumne River water along with permission to build a dam and pipelines.

The reservoir, managed by the San Francisco Public Utilities Commission, now provides water to the Modesto and Turlock irrigation districts and 24 cities and water districts in Alameda, Santa Clara and San Mateo counties, in addition to San Francisco.

The lawsuit claims the drowned valley, bordered by sheer granite cliffs, was once “as thrilling and majestic a landscape as Yosemite Valley” to the south in the park.

It alleges that the continued operation of the dam and Hetch Hetchy Reservoir violates the California Constitution, which requires state water resources to be used in a reasonable way and “put to beneficial use to the fullest extent” possible.

The reservoir eliminates or impairs scenic, recreational, aesthetic and fishing uses of the river, the lawsuit claims.

It asks the court to order San Francisco to develop a plan to provide the needed amount of water by diverting the river and storing the water further downstream outside of the park, so that the dam can be breached and the valley restored.

“Not one drop of water need be lost” if the river water is captured and stored at a later point and the valley restored, Restore Hetch Hetchy leader Spreck Rosekrans said in a statement.

The lawsuit suggests that the court refer the case to the California Water Resources Control Board for an investigation and report before the case is returned to court for a decision.

Matt Dorsey, a spokesman for San Francisco City Attorney Dennis Herrera, said Wednesday that lawyers in that office had not yet seen the lawsuit, but said San Francisco will “vigorously defend” its water arrangements.

The Bay Area Council, a public policy group representing 275 employers in the region, issued a statement calling the lawsuit “misguided” in view of the current drought.

“Who needs an historic drought when there’s a group that wants to tear down one of California’s critical water storage and clean energy systems,” council president Jim Wunderman said.

Proponents of eliminating the Hetch Hetchy Reservoir gathered signatures to put a measure on the San Francisco ballot in 2012 that would have forced the city to formulate a plan to dismantle the dam.

However, that measure, Proposition F, was roundly rejected by 77 percent of the city’s voters in the November 2012 election.

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