It is unclear whether the upcoming winter will be the rainy season the state so desperately needs. If not, California could be facing mandatory water conservation measures again as voluntary reductions fail to impress.

California’s drought may not be over, but a troubling number of residents – and the suppliers that deliver water to them – appear to be acting like it is.

Last week, the State Water Resources Control Board announced that, compared to 2013 numbers, urban water conservation dropped from 27 percent in August 2015 to 17.7 percent this past August. It’s a clear sign that voluntary reduction targets aren’t having the same effect as the 25 percent statewide mandatory cuts issued by Gov. Jerry Brown a year and half ago, which were lifted in June.

The trend is an ominous one, said Peter Gleick, a water and climate expert and chief scientist at the Pacific Institute, a global water think-tank he co-founded in Oakland nearly 30 years ago. Gleick believes permanent, statewide targets for water conservation and efficiency must be implemented, and blames the rise in water use on the State Water Board’s decision this summer to move to a voluntary program, “at which point almost all of the water agencies statewide, south and north alike, set zero conservation targets.”

Part of the problem was the sharp shift in communication. “I think the messaging is really important,” said Gleick, who noticed months ago when he stopped seeing water conservation messages show up in his social media feed and his mail. “When the state board removed the mandatory targets, that sent a message. I think it sent the wrong message, and I think the numbers reflect that. It sort of said, ‘The drought’s over, the mandatory conservation targets are gone.’”

In addition to last year’s moderately wet winter in parts of the state, Gleick cited another, more cynical reason why the State Water Board decided to halt water restrictions: The conservation measures were hurting the bottom line at water agencies throughout the state. “When their customers conserve, they sell less water, and when they sell less water, they make less money,” said Gleick, and what you end up with is “this disconnect between the urgent need to conserve water statewide, and the financial incentives that water agencies have to sell water.”

All of which isn’t to say that Californians have stopped conserving. A 17 percent reduction in overall water use from several years ago shows clear progress. The State Water Board reports that since June 2015, residents have saved 2 million acre-feet of water – the equivalent of supplying 10 million people with water for one year. At the same time, the reported 36 percent fall in water savings, from 63.5 billion gallons (240 billion liters) in August 2015 to 40.4 billion gallons (153 billion liters) this August, wasn’t uniform across the state; on the contrary, many regions continue to show efficient water use even as other areas have lagged.

“We are examining the data to understand why some areas slipped more than others,” State Water Board chair Felicia Marcus said in a statement last week. Calling the results “a mixed picture,” she said many communities that “certified that they didn’t ‘need’ to conserve are still conserving up a storm, while others have slipped more than seems prudent.”

Among the cities that showed the steepest drop in conservation were Malibu, where water savings plummeted from 20.4 percent in August 2015 to 7.9 percent in August 2016. According to the Los Angeles Times, Malibu’s 22,000 residents used about 300 gallons (1,136 liters) per person per day in August, compared with Los Angeles residents who averaged just 84 gallons (318 liters) per day. An even worse offender was the Santa Fe Irrigation District, serving mostly affluent areas in northern San Diego County, where residents used 525 gallons (1,987 liters) per person per day in August – a fall of 22.6 percent in water savings over the same period last year.

In Stanislaus County in the Central Valley, cities like Modesto, Turlock, Ceres and Oakdale all saw their water savings fall in August over the previous period last year, according to the Modesto Bee.

“People don’t appreciate that we live in a Mediterranean climate where water is precious and we shouldn’t overuse it,” said Dennis Baldocchi, a professor of biometeorology and ecosystem ecology in the Department of Environmental Science, Policy and Management at the University of California, Berkeley. “We’re mining this water. It took tens of thousands of years for that water to form. And farmers are now going even deeper, hundreds and hundreds of feet deep, and spending hundreds of thousands of dollars to drill for water that they then have to lift [out of the ground] using immense power. What they’re doing is not sustainable in the long run,” he said.

On October 1, California’s drought officially entered its sixth year. Since no climatologist can say what this winter – or the next five winters, for that matter – will bring, Baldocchi cautioned that water managers “should be thinking big picture, and longer term. We don’t know if these droughts are going to return more often. It should be a lifestyle in California that we all conserve, making it normal to have low-flush toilets and use recycled gray water. It’s not rocket science solutions: a little bit from everybody adds up.”

For starters, he said, the state needs to put a more accurate price on water, which remains dirt cheap, allowing large business interests including hedge funds to buy up immense tracts of farmland in the Central Valley where they draw out water without shouldering the cost. “If they really paid for the cost of moving water around, they’d pay a lot more. What the real, fair price should be is something economists need to think about,” Baldocchi said.

Due to the decline in conservation, the State Water Board has signaled the possibility of returning to state-mandated cuts at the start of 2017, depending on how much rain the state receives.

But for Gleick, permanent and mandatory cutbacks of the kind that worked successfully between 2015 and 2016 – with rebates for people who switched to using low-flush toilets or changed out their lawns for drought-resistant gardens – will be key to managing the state’s future water supply.

“It’s not a question of making everybody constantly panic, or creating a crisis mentality. It’s a question of getting smarter with the way we use our limited water resources, and there are lots of things we can do,” he said. “There are no good forecasts. We’re hoping that it will be wet, but we better plan for it to be dry. Look at it this way: Every gallon of water that we don’t save, that we could save, is a gallon that is no longer in our reservoirs. That’s why wasteful use is so damaging.”