At a Glance

State water regulators vote 4-1 to reallocate water to help fish.The vote came even as Gov. Brown and water agencies reached a deal.Some water suppliers are already threatening lawsuits over the plan.

California's water regulators have approved a plan that will cut water supplies to dozens of communities, from the Central Valley to San Francisco.

The vote Wednesday by the State Water Resources Control Board will reallocate water from the San Joaquin River and its tributaries from farms and cities to , the Fresno Bee reported.

Thewill require tributary rivers within the San Joaquin watershed to maintain an average water level of 40 percent of “unimpeded flow” — that is, the flow that would exist without human activity — during the spring season. Now, as little as 20 percent of the water stays in the rivers. The three major tributaries are the the Merced, Stanislaus and Tuolumne rivers.

Households in the Bay Area may have to reduce water use by, the San Francisco Chronicle reported. And during long dry spells, customers could be forced to reduce water use by 40 percent, the San Francisco Public Utilities Commission said.

The state board approved the plan 4-1 despite a last-minute $1.7 billion compromise agreement between Gov. Jerry Brown's administration and water suppliers.

(MORE: California's Central Valley is Sinking Because of Drought and Groundwater Loss)

Under the deal, many cities and farms across the Central Valley would contribute blocks of water, habitat restoration, , according to the Modesto Bee. In exchange, some of the difficult Bay Delta Plan requirements would be removed.

Water board members said they voted for their original plan to put pressure water agencies that hadn't agreed to the deal with Brown's administration.

The agreements are “potentially quite good. But … the devil’s in the details,” state water board Chairwoman Felicia Marcus told the Fresno Bee.

Environmentalists say the Brown agreement doesn't do enough to help struggling fish populations.

“The salmon are at the point where they can’t wait any longer,” Regina Chichizola of Save California Salmon told the board.

(MORE: 12 GIFs That Show How Weather Left Its Mark in 2018)

According to the Chronicle, the state says the reduction in water available for agriculture is estimated to result in a 2.5 percent drop in produce output in the San Joaquin River basin.

Already, some water suppliers are threatening lawsuits over the board's plan.

“We’re disappointed by the board’s action and we’ll take any and all measures to protect our water supply and our communities,” the Modesto Irrigation District said.

The Trump administration also has promised to take legal action to block the plan.