LOS ANGELES (CNS) — One day after approving a restriction that will limit outdoor watering to once a week for millions of Southern California residents and businesses, leaders of the region's water wholesaler said Wednesday they needed to take unprecedented steps to respond to what they call an unprecedented drought, and even tougher rules could soon follow.

"The reality is, this drought has left us without the water supply we need to meet normal demands in these areas," Adel Hagekhalil, general manager of the Metropolitan Water District of Southern California, said in a statement. "To make sure we have enough water for their basic human health and safety needs, everyone in these communities must immediately and dramatically reduce their water use."

The agency noted that the first three months of the year in California were the driest in recorded history, even though that is the time when the state typically receives nearly half of its precipitation.

The watering restriction approved by the MWD board Tuesday will impact roughly 6 million people in Los Angeles, San Bernardino and Ventura counties. The MWD is the supplier for water agencies throughout Southern California, but the restriction will apply to those that are heavily dependent on State Water Project deliveries.

Due to the drought, the state has slashed SWP deliveries to just 5% of requested allocations. MWD officials said the State Water Project typically provides 30% of the water used in Southern California.

The watering restrictions will take effect June 1. And MWD officials warned that if the move doesn't result in sufficient water savings, additional restrictions are possible, including a complete ban on "all non-essential outdoor irrigation."

Those additional restrictions could be imposed as early as Sept. 1.

"This is a crisis unlike anything that we've seen before," MWD Executive Officer Deven Upadhyay said. "We really only have a little more than half of the water that we need to be able to make it through the summertime and into the end of the year under normal demands, and that's why normal will not work."

According to the MWD, the watering restriction will affect at least some customers served by the Las Virgenes Municipal Water District, the Los Angeles Department of Water and Power, the Upper San Gabriel Valley Municipal Water District, Inland Empire Utilities Agency, Calleguas Municipal Water District and Three Valleys Municipal Water District.

Not all customers of all of those agencies will be impacted. A map provided by the MWD indicates the watering restrictions will affect parts of the San Gabriel and San Fernando valleys, and western reaches of the county including Woodland Hills, Canoga Park and Calabasas, some coastal areas of West Los Angeles and parts of Hollywood.

"Metropolitan has never before employed this type of restriction on outdoor water use," Hagekhalil said. "But we are facing unprecedented reductions in our Northern California supplies, and we have to respond with unprecedented measures. We're adapting to climate change in real time."

The MWD urged all Southern California residents and businesses to slash water use by 30% to combat drought conditions "unlike anything we've experienced before."

MWD member water agencies that fail to enforce the requirement among its customers will face fines of up to $2,000 per acre-foot of water supplied by MWD that exceeds monthly allocation limits.

According to MWD, its member agencies will be responsible for determining which days watering will be allowed for its customers. Individual agencies can also opt — instead of enforcing the one-day watering rule — to meet a pre-determined limit on the overall reduced amount of water it can use. If the agencies exceed that limit, it will face the same fines.

Gov. Gavin Newsom last month directed MWD and other water suppliers statewide to ramp up conservation efforts by advancing water-shortage contingency plans

MWD offers a rebate of $2 per square foot for people who replace their grass with water-efficient landscaping. Rebates are also available from other local water agencies.

The rebate program has helped remove 200 million square feet of grass, which has saved enough water to provide about 62,000 homes with water each year, officials said.