Photo: A tractor plows a dry field last month in Madera. Thousands of farms and water agencies that rely on flows from California’s vast delta watershed are being told to stop drawing water from rivers and creeks. Justin Sullivan/Getty Images

15 June 2021 | Kurtis Alexander | San Francisco Chronicle

“This really emphasizes the seriousness of the circumstances we find ourselves in during this drought,” Joaquin Esquivel, chair of the State Water Resources Control Board told The Chronicle. “It’s about responding to the drought itself and the curtailment (of water) that Mother Nature is imposing upon us.”

The board’s actions mark the latest and most drastic cuts this year under California’s water rights system. The system, seldom employed to the extent it is now, is designed to ration low flows in rivers and creeks during dry times. Seniority is based largely on who has the oldest claims to the waterways, leaving a mosaic of users, both agricultural and urban, with water and without.

The water board, the agency charged with regulating state supplies, determined this week that the rivers and creeks in the Sacramento-San Joaquin River Delta watershed, which runs from the towering Sierra Nevada and southern Cascades to San Francisco Bay, have too little water for everyone with a water right — the area represents about 40% of California. The board is also required to consider the needs of fish and wildlife.

The board subsequently began sending out notices of water unavailability to the basin’s holders of water rights acquired since 1914, considered junior holders. The notices, while not technically curtailment orders, carry potential fines for those who continue taking water. Official curtailment orders, which mean less judicial recourse for water users and potentially greater penalties, generally follow.

While the board did not provide a list of water rights holders being curtailed, the East Bay Municipal Water District is likely to receive notice that there is no longer water available for the agency to exercise its two most important water rights: a 1924 right allowing it to divert water from the Mokelumne River to the Pardee Reservoir and a 1949 right allowing it to divert water from the Mokelumne River to the Camanche Reservoir.

District officials said the directive would have little consequence because they’ve already stopped taking water into the reservoirs.

“Because it’s been a dry year, essentially all of the snowpack has melted on the Mokelumne River,” said Michael Tognolini, the agency’s director of water and natural resources. “The runoff has receded quickly, especially in the last month or so.”

Tognolini said the district has enough water in storage to serve its 1.4 million customers without the need for mandatory water restrictions, at least for this year.

This won’t be the case for the agricultural industry. Many farmers have already been denied water from the state and federal water projects because of limited deliveries during the drought. For those with separate water rights that get cut off, it’s one more blow.

“Curtailment is not a game,” said Chris Scheuring, water attorney for the California Farm Bureau Federation. “It affects families. It affects livelihoods. I got through college on farm income.”

Already, plantings of more than 20 crops have been scaled back statewide because of the lack of water, from almonds and asparagus to watermelons and wheat, according to the California Farm Water Coalition. The total economic hit to the industry won’t be known until the year’s harvest is picked and shipped.

The shortages of water come after back-to-back winters with extremely low precipitation. The two-year period across most of the state was the second driest on record, following only 1976-77. California’s rivers, including the many that flow to the delta, have had very little water as a result.

The state water board is also sending notices to 2,300 senior water rights holders, informing them that water may be unavailable for them to draw this summer. These water users include those with pre-1914 water rights as well as those with land adjacent to a waterway, known as a riparian right.

The San Francisco Public Utilities Commission, which gets most of its water from the Tuolumne River in Yosemite, is among the many senior water rights holders in the delta watershed. During the drought of 2012-2016, which was the last time the state water board curtailed so many water rights holders, the city was ordered to stop drawing water at four locations in the Sierra. City officials ignored the directive.

While small numbers of curtailments aren’t uncommon, taking aim at senior users is rare, controversial and likely to again invite pushback. The water board began regulating water rights in 1914, and its authority to regulate rights before this time is fraught with legal uncertainty.

“We’re monitoring the situation closely,” said Will Reisman, spokesman for the SFPUC.

Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander