San Luis Obispo residents and businesses, for the first time, will soon be forced to limit outdoor watering to three days a week.

The San Luis Obispo City Council adopted mandatory watering restrictions Tuesday at the behest of the State Water Resources Control Board, which recently adopted emergency drought regulations.

The rules must be implemented by all urban water suppliers, regardless of the community’s water supply, or face a $10,000-per-day fine.

The restrictions, which pertain to outdoor irrigation of ornamental landscape and turf with potable water, will begin on Oct. 2.

Even-numbered addresses will be permitted to water Sunday, Tuesday and Thursday; odd-numbered addresses will be able to water Monday, Wednesday and Friday.

Hand-watering of plants and vegetable gardens is exempt. Recycled water is also exempt.

“Water is a scarce resource, but people in San Luis Obispo have paid for it,” said Mayor Jan Marx. “This is a lifestyle choice not necessitated by the city’s lack of water. Yes, we are water secure right now, but we must comply with the state.”

County supervisors also adopted an ordinance Tuesday that limits water users in Cayucos, Shandon, Santa Margarita and Avila Valley to outdoor watering only on Mondays and Thursdays.

San Luis Obispo resident Steve Del Martini said he was concerned that the added conservation measures would eventually lead to higher rates for consumers.

The operational budget of the city water department is based on revenue assumptions related to water use. If that use drastically declines, then the utility department would likely have to raise rates to fix the shortfall or enact other cost-cutting measures.

Carrie Mattingly, utilities director, said the city will rely first on a rate stabilization fund to offset additional costs to consumers.

“We do not want to raise rates because of the drought,” Mattingly said. “Conserving water is important. We also don’t want to be scofflaws against the regulations.”

According to city staff, a recent projection of the city’s water supply shows that about seven years of water is available to the community, if mandatory conservation actions are put in place for three of those years.

Customers who do not follow the new regulations will be warned and then issued a $50 citation through the city’s administrative citation process.

The ordinance will stay in effect as long as the state’s emergency conservation regulations are in place — which have currently been set for 270 days but can be extended or rescinded based on the drought conditions.

The city has set up a hotline at 783-7776 for people who witness excessive use of water. More information about mandatory conservation can be found at http://slowater.org.