Californians are using less water, but they'll have to conserve a lot more to reach the mandatory drought cuts taking effect this month, according to the latest numbers released Tuesday.

California residents reduced overall water use by 13.5 percent in April compared to the same month in the benchmark year of 2013, water officials said.

That's the second-best conservation achievement since state officials started closely tracking water use more than a year ago, but it fell short of the 25 percent cut that Gov. Jerry Brown made mandatory for cities and towns as of June 1.

"Local communities are stepping up in a way they weren't before, and I'm hoping that's why we are starting to see the uptick" in conservation, said Felicia Marcus, chairwoman of the state Water Resources Control Board.

"The real challenge is, we really have to step it up for the summer months," Marcus said. "If we miss the summer, we are toast."

April's still-lackluster overall savings reported by the roughly 400 water agencies in the state could raise concerns about whether Californians have fully acknowledged the severity of the drought.

This year's Sierra Nevada snowpack, which feeds the state's rivers, was the lowest on record — a grim image that served as Brown's backdrop when he announced unprecedented conservation measures on April 1.

"When they saw the governor out on that dry meadow and saw what was in his executive order, and realized it was really time to step up, they really started to step up," said board scientist Max Gomberg, who is overseeing conservation.

April's best conservers included Santa Rosa, a city of 170,000 people north of San Francisco, which reported a 32 percent drop in April compared to the same month in 2013. The city offered a host of programs to achieve savings such as paying residents to reduce 52 football fields' worth of lawn and giving away 50,000 low-flush toilets since 2007.

Saved water "is the cheapest water you can find," said David Guhin, water director for Santa Rosa. "It's gotten to where lawns are uncool."

Cool or no, many communities are still falling far short.

"Fifty-thousand toilets? Really? We don't have that kind of money," said Alan Tandy, city manager of Bakersfield, where water use increased by 1 percent in the latest state tally.

Along with offering some modest rebate programs for water conservation, the working-class city surrounded by farms and oil rigs was finding it difficult to get the word out to everybody about saving, Tandy said.

The Southern California coast, a region including Los Angeles and San Diego, cut just 9 percent in April, compared to a 20 percent reduction in the San Francisco Bay Area and 24 percent in the Sacramento area.

Among cities of 40,000 or more, the steepest reduction of 45 percent was reported by the water company serving Livermore. The worst was Escondido, reporting a 20 percent increase.

Starting this month, each community has a mandatory water reduction target, with some ordered to cut back as much as 36 percent.

Water districts missing their targets face potential fines of up to $10,000 a day once June numbers are in, although a far more likely outcome will be state-ordered changes in local regulations, like toughening limits on lawn-watering.

The shift to mandatory conservation followed lackluster savings through a voluntary effort, with water use slipping just 3 percent in February and 4 percent in March compared to the same months in 2013.

Water waste also is being tracked, and the board could penalize local agencies that don't crack down. Only a tenth of water departments reported penalizing their customers for water waste in April.

Suppliers of treated water closely monitor and report their customers' usage each month, but most farmers self-report consumption long after their crops have been grown and harvested.

But as more wells and streams run dry, California's farmers are expected to increase by a third the fields they fallow this year.

The drought's impact on agriculture alone will cost California $500 million more than last year, for a total economic hit of $2.7 billion in 2015, according to a new study by the University of California at Davis.

Roughly 200 farmers in the Sacramento-San Joaquin River Delta east of San Francisco have submitted plans for voluntarily reducing water use by 25 percent to avoid deeper mandatory cuts later this year.

State officials are still figuring out how much water could be saved through the deals, but state delta water master Michael George said he expects significant conservation.