Even as water allocations to California farmers have been severely reduced, San Francisco water authorities have freely tapped the Tuolumne River, which the city dammed early in the last century at its headwaters in Yosemite National Park. 

Now the State Water Resources Control Board wants the city to help save the estuary by leaving 40 percent of the Tuolumne’s water in the river, a level that the board’s own scientists have said may not be enough to rescue the freshwater-starved bay and delta.

The Tuolumne is one of the most over-drafted rivers in the state, running on average at just 20 percent of its natural flow. The river provides 85 percent of the water used by 2.6 million Bay Area residents, including San Francisco.

Chasin’ Crustacean operator Christian Cava naugh filets salmon for a passenger. Regula tors say more water is needed to save fish.
The draft rule, which the board hopes to make final next spring, could severely restrict water use during drought years, when there is not enough water for both the ecosystem and humans at current rates of consumption.

Jeffrey Mount, an expert in water policy at the Public Policy Institute of California, a nonprofit think tank, called the steps a long-overdue effort to “rebalance the allocation of water for the ecosystem and water we use consumptively.”

The Clean Water Act, a landmark federal environmental law, is driving a new approach, Mount said.

Mount, a senior fellow at the institute’s Water Policy Center, called the plan to leave more water in the rivers far weightier than the multibillion-dollar twin tunnels that Gov. Jerry Brown wants built to draw water directly from the Sacramento River, bypassing the delta, and send it to cities and farms in the south.

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