Spurned at the ballot box three years ago and facing an even more uphill battle now because of California’s historic drought, an environmental group has filed a lawsuit attempting to drain Hetch Hetchy Reservoir, a linchpin of the water supply for 2.6 million Bay Area residents from San Francisco to San Jose to southern Alameda County.

The reservoir in Yosemite National Park, built in 1923, violates California’s constitution, according to the suit from the nonprofit Restore Hetch Hetchy, based in Oakland.

Water that flows from the Sierra Nevada, through the Tuolumne River and into the reservoir can be stored in other reservoirs in the Sierra and downstream, the group argues. As a result, it contends, San Francisco, which owns the system, is not following a key provision of the state constitution requiring that water in California “be put to beneficial use to the fullest extent possible” and be used in “reasonable” ways.

“Hetch Hetchy Valley in Yosemite National Park was once one of our nation’s most treasured landscapes. Its destruction, allowed a hundred years ago, is widely regarded as a mistake,” said Spreck Rosekrans, executive director of Restore Hetch Hetchy. “The time has come to have a conversation about the merits of restoration in a court of law.”

The lawsuit, filed Tuesday in Tuolumne County Superior Court, was blasted by business and city leaders in San Francisco.

“Who needs a historic drought when there’s a group that wants to tear down one of California’s critical water storage and clean energy systems?” said Jim Wunderman, president and CEO of the Bay Area Council, which represents 275 of the Bay Area’s largest companies.

“The court should quickly dismiss this.”

Hetch Hetchy Valley is a spectacular landscape that rivaled nearby Yosemite Valley before Congress approved construction of O’Shaughnessy Dam in 1913, submerging the valley under 300 feet of water.

The fight to save the valley was the final battle of Sierra Club founder John Muir’s life. And the valley’s submersion has haunted many environmentalists ever since.

For years, supporters of restoring the valley have said the water could be stored in Don Pedro Reservoir, Cherry Reservoir and other lakes. But Wunderman and other opponents say the issue is far more complex, involving technical problems and controversies with other water agencies that also have rights to the reservoirs.

In 2012, Restore Hetch Hetchy placed a measure on the San Francisco ballot which would have required the city to conduct an $8 million study of draining the reservoir. It was endorsed by three former Yosemite superintendents. But it was opposed by U.S. Sen. Dianne Feinstein, San Francisco Mayor Ed Lee and Silicon Valley business leaders. It failed in a landslide, 77-23 percent.

“This new lawsuit, like the 2012 initiative, is an unfortunate distraction from our core mission of delivering reliable drinking water to 2.6 million people in the Bay Area,” said Tyrone Jue, a spokesman for the San Francisco Public Utilities Commission.

Paul Rogers covers resources and environmental issues. Contact him at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN