By Melody Gutierrez and Jill Tucker

San Francisco Chronicle

SACRAMENTO, CALIF. — As drought conditions worsen, California is taking the unprecedented step of cutting off water to contractors that serve 25 million people and 750,000 acres of farmland.

As a result, Californians who have not yet felt the effects of what could be the state’s worst drought in modern history may soon begin to experience the pain. Across the state, more cities are expected to begin implementing mandatory restrictions on water use.

“Today’s action is a stark reminder that California’s drought is real,” Gov. Jerry Brown said Friday. “We’re taking every possible step to prepare the state for the continuing dry conditions we face.”

The California Department of Water Resources announced Friday that if dry conditions continue, water agencies will not receive any water from the State Water Project, a system that serves two-thirds of California’s population using reservoirs, aqueducts, power plants and pumping plants. Water is sent to 29 water suppliers throughout the state, which then provide the water to agencies serving homes and farms.

San Francisco, the Peninsula and other parts of the Bay Area would not be directly affected by the water cut off because they get water from other sources, such as Hetch Hetchy. But as water becomes scarce, less fortunate agencies may turn to healthier ones for assistance.

Department Director Mark Cowin said at a news conference that if the dry spell continues, only carryover water from last year will be channeled to the farmers and several towns that get their water from the State Water Project. Those users will have to rely on groundwater, local reservoirs and other supplies.

“Everyone — farmers, fish, people in our cities and towns — will get less water as a result, but these actions will protect us all better in the long run,” Cowin said. “Simply put, there is not enough water to go around, so we need to conserve.”

The announcement comes after state health officials said 17 communities and water districts are in danger of running out of water within 100 days, including Cloverdale and Healdsburg.

The list is expected to grow.

The snowpack in the Sierra is 12 percent of normal for this time of year, the lowest since the state began keeping snowpack records in 1960. California wildlife officials banned fishing in several rivers to protect salmon and steelhead trout.

The state’s largest reservoirs — Shasta Reservoir north of Redding and Lake Oroville in Butte County — are at 36 percent of capacity. Folsom Lake is at 17 percent, exposing an abandoned town from the 19th century.

With two-thirds of the wet season having passed, there is little hope that enough rain and snow will fall to lift California out of the crisis.

“The state would have to experience heavy rainfall and snowfall every other day through May to get back to average precipitation levels,” Cowin said.

Bay Area water agency officials said they planned for the worst, but this is “worse than the worst,” said Robert Shaver, assistant general manager for the Alameda County Water District, one of four Bay Area agencies that gets its water supply from the State Water Project.

The district typically gets 40 percent of its water from the State Water Project for its customers in Fremont, Union City and Newark.

Without that water, it will have to rely more on local groundwater and the water it gets from the Hetch Hetchy to meet demand, which is about 45 million gallons per day.