Faced with worsening drought, the Metropolitan Water District of Southern California has ordered major watering restrictions aimed at reducing demand.

Here is what you need to know:

A large swath of Southern California — covering six million people — will be restricted to watering outdoors just one day a week. Alternatively, local water suppliers must find other ways to cut usage and meet a new monthly allocation limit, or face fines.

The regulations don’t cover all of Southern California. They apply to areas of Los Angeles, Ventura and San Bernardino counties that are dependent on water from the drought-ravaged State Water Project.

According to a map presented Tuesday by the MWD, the areas include a large swath of Ventura County as well as the San Fernando Valley, the Westside of Los Angeles, sections of the San Gabriel Valley and southwestern San Bernardino County.

For the first time ever, Southern California water officials will limit outdoor watering to just once a week in certain areas beginning June 1.

Some of the larger communities that fall under the new rule include: Thousand Oaks, Calabasas, Van Nuys, Woodland Hills, Hollywood, West Covina, El Monte, Monrovia, Claremont and Fontana.

Map of some areas to be hit by new water restrictions >> https://t.co/EKgdUx4x2L pic.twitter.com/VhnM29f3xQ

The MWD said it will be up to local water agencies to make those determinations and to communicate them to customers. “Metropolitan will not specify the day of the week or any method of even/odd house numbering rotation to moderate distribution system impacts. Metropolitan will, however, require that Member Agencies limit watering times to prevent substitution of water use from newly banned days to permitted days,” it said in a report.

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“Member Agencies must be willing and able to impose meaningful penalties for non-compliance. As such, a Member Agency choosing this compliance path also must submit to Metropolitan an enforcement plan with real consequences to the consumer or end user for failing to abide by the one-day-per-week restriction or ban on outdoor water use. This enforcement plan must be auditable, with a clear and transparent way to verify enforcement if expected water use reductions fall short,” the report added.

The water level at Mono Lake has fallen to a key threshold, prompting cuts in water exports by the Los Angeles Department of Water and Power.

The MWD report cited some exceptions. “The primary exception is to allow hand-watering of trees or other perennials to support their health and ability to recover once the outdoor watering restrictions are lifted. A second exception is to allow drip or other high-efficiency irrigation systems to apply water at a weekly volume consistent with the one-day watering restriction imposed on less efficient irrigation systems. Metropolitan will continue to coordinate with the affected Member Agencies on an appropriate formulation of these types of exemptions if a complete ban on outdoor watering is imposed.”

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Ian James is a reporter who focuses on water in California and the West. Before joining the Los Angeles Times in 2021, he was an environment reporter at the Arizona Republic and the Desert Sun. He previously worked for the Associated Press as a correspondent in the Caribbean and as bureau chief in Venezuela. He is originally from California.