Southern California's water wholesaler voted on 14 April to cut its deliveries to cities and communities by 15% as the state clamps down on water usage amid a devastating four-year drought.

The Metropolitan Water District's plan aims to put cities in the greater Los Angeles area in compliance with an order by Governor Jerry Brown to reduce water use by 25%, the first mandatory statewide reduction in California history.

Beginning in July, two-dozen member agencies will be fined up to four times their regular rates for demanding excess water. Those penalties will range from $1,480 (£1004) to $2,960 per acre-foot of water.

The cutbacks are expected to last a year, with opportunities each month to amend the system. A formal reconsideration is scheduled for December, during the rainy season.

If Brown's statewide plan succeeds, businesses and residents will use only three-quarters of the amount they used in 2013. The savings would amount to some 1.5 million acre-feet of water in the next nine months, just as the state snowpack is at its lowest level on record.

"It's not time to panic, it's time to act wisely and prudently," MWD General Manager Jeffrey Kightlinger said, adding, "We're saying, you're going to go down from three times a week to probably one day a week. Take out your lawn, take out some of that ornamental landscaping, I don't think that's panic, but it is time to act."

Some board members had pushed for a higher cutback rate of 20% - a difference of 100,000 acre-feet, or 326,000 gallons. Just one acre-foot can provide for two average households a year.

Kightlinger said the water supply drop combined with incentives to conserve - such as rebates to rip out thirsty lawns - will help Southern California reach its state target of a 25% cutback.