California water regulators Friday took a step that they haven’t taken since 1977: They cut water allocations to 114 senior water-rights holders in the state.

In fact, this action will probably have more impact than the 1977 cuts, because the state has a greater legal and practical power to demand restrictions.

The State Water Board issued a notice saying: “The State Water Board has been monitoring diversion records and flow conditions within the Sacramento-San Joaquin River watershed and Delta. Due to limited precipitation and snowpack runoff, the current flows are insufficient to satisfy all diversion demands under senior rights.”

The Sacramento Bee reports that this is just the beginning:

Officials said even more curtailment orders are likely in the weeks to come as demand increases and supplies dwindle.

“It’s not even summer,” said the board’s executive director, Tom Howard. “We’re going to be doing further curtailments.”

The senior water-rights holders include water districts — which provide water to farmers — and municipalities (including, incidentally, my hometown, Nevada City). You can find a list of those affected here.

California is expecting lawsuits over all this — and there are legal uncertainties still lingering from the 1970s. Back then, water-rights holders sued the state, but before the court system could reach a decision, it started raining, rendering the issue moot.

It’s unclear how much water this will keep in the rivers — here’s the Sacramento Bee again:

Plenty of water rights holders, anticipating Friday’s action, have been storing water in reservoirs, and that supply is off limits to regulators. “Stored water is … essentially the property of the person who stored it,” Howard said.

But he said he believes Friday’s order will bring more pain to water users, particularly farmers. “There will be some land ending up being fallowed as a result,” he said.

Deep as these cuts are, they don’t affect the oldest water-rights holders — just those dating back to 1903. San Francisco’s water right was established in 1901. There aren’t many older than that.