SACRAMENTO — Few local water agencies have forced customers to cut their water use amid the ongoing drought, but a new poll shows a large majority of Californians support mandates to turn off the tap.

Three-quarters of people surveyed across the state want to see their local water providers require reductions, the Public Policy Institute of California found.

Support for restrictions stretches across the state and tops 80 percent in Los Angeles, where water use has barely budged since Gov. Jerry Brown declared a drought emergency earlier this year, according to a survey the group released Wednesday. With Brown also pushing for tougher curbs, it appears the agencies themselves, who stand to lose money if Californians use less water, are the holdouts.

Water is too important to leave to personal discretion, a Sunnyvale resident said Wednesday.

“You need to make the rules compulsory or a significant portion of people won’t do what needs to be done,” said Kevin Jackson, 61, a retired computer professional. “Water is right up there with air in terms of resources that have no substitutes, but some people just won’t listen.”

More than half of respondents said they believed water supply is a big problem in their part of the state, but Californians seem undecided about why that is. A majority of people polled said they believe global warming risks a drier California in the future, but most believe natural weather patterns have caused the now three-year drought.

The institute conducted the survey between July 8 and July 15 among 1,705 adults. Its margin of error is plus or minus 3.7 percentage points.

Support for local, mandatory water-use restrictions has picked up in recent months because people are becoming more keenly aware of how serious the bone-dry weather is for the state’s economy and ecosystems, said Felicia Marcus, chairwoman of the state Water Resources Control Board.

“No one inherently wants to waste a precious resource like potable drinking water, but people have busy lives,” Marcus said. “They’re not out there checking reservoir levels and thinking about how long this drought might last. It’s our job to tell them.”

The state recently kicked off a drought-busting “Brown is the New Green” advertising campaign, and last week, a state water agency approved unprecedented penalties for people who waste water by soaking the lawn or washing a car using a hose without a shut-off nozzle.

Cindy Aisenbrey was a child when California suffered through its last severe drought, and the 47-year-old said she wonders why the stiff water-use restrictions the state adopted then aren’t in place now. Limiting the number of days homeowners can water their lawns isn’t enough, she said.

“Back then, no one served water at restaurants. Water was restricted everywhere,” said Aisenbrey, a contract negotiator from Livermore. “It would behoove us to get back to that. Otherwise, we’ll be in very dire straits.”

The timing of a local water agency’s decision to constrain customer water use is crucial if the provider hopes to build public support for an imposed hardship, said Jay Lund, a resources expert at UC Davis. Moving too quickly could cause an unwanted backlash.

“If you’re a water utility, you don’t want to be accused of crying wolf,” Lund said. “If they impose restrictions this year, and next year we get wet weather, people will say, ‘Why did you do it?’ This is the dilemma urban utilities face.”

Walnut Creek resident Jim Rogers said he favors water-use restrictions tailored to individual households and hopes to see Central Valley farms — which use 80 percent of the state’s water to grow a large portion of the country’s fruits and vegetables — start planting fewer water-intensive crops.

No one in California is doing enough to plan ahead for a drought that could last years, said Rogers, a 57-year-old teacher.

“No one in California wants to accept that anything bad is happening until that thing has become a disaster. Everyone I know is still hoping a good El Niño season will save us.”

Contact Jessica Calefati at 916-441-2101. Follow her at Twitter.com/calefati. Read the Political Blotter at IBAbuzz.com/politics.