More than 400,000 people in the Sacramento region are now living under severe water rationing orders in response to California's worst drought in a generation, and more are likely to join them.

On Wednesday, both the San Juan Water District and the city of Folsom ordered all their water customers to immediately reduce consumption by 20 percent. The order is backed by "water cop" patrols and fines for repeat offenders.

They join Roseville, which imposed a similar requirement last week.

All three are under unique pressure in the region because they depend on pipelines tapping Folsom Lake. Last week, the U.S. Bureau of Reclamation, which manages the lake, warned its urban customers they will get only 50 percent of normal water deliveries because this winter looks likely to create a third straight year of drought.

Folsom Lake stands at only 67 percent of average capacity for this time of year. Reservoirs statewide are in a similar condition, and many water agencies have had rationing orders in place for months.

Last week, state and federal water agencies urged all Californians to immediately cut their water use by 20 percent, whether they are required to do so or not. As the drought worsens, it's likely that more capital-area water agencies will respond with mandatory rationing orders.

In Folsom and parts of suburban Sacramento served by the San Juan Water District, new rules mean water cops will be out enforcing water-waste prohibitions. Leaks must be capped, no hosing of decks or pavement is allowed, and water may be served in restaurants only on request.

"We have to reduce our water uses by 20 percent right now," said Shauna Lorance, general manager of the San Juan district, which serves its own customers as well as Citrus Heights, Orangevale, Fair Oaks and part of Folsom. "Despite the recent rain, we're facing dangerously low water supplies."

The mandates are necessary because the Folsom Lake intakes serving these agencies could become ineffective if the lake level continues dropping. They are also concerned about looming spring weather and higher temperatures, which usually trigger a spike in water demand.

Both San Juan and the city of Folsom are in "Stage 3 Water Warning" conditions. In Folsom, this means customers may water landscaping only two days a week, and only between 10 p.m. and 10 a.m. For odd-numbered addresses, those days are Tuesday and Saturday; for even numbers, it's Wednesday and Sunday.

For San Juan customers, the irrigation requirements are a bit simpler.

"At this point, nobody should be irrigating," Lorance said.

Next month, however, the district is likely to enforce twice-weekly watering limits.

The two agencies also prohibit using hoses without shutoff nozzles, and no water may be used for construction purposes unless approved in advance.

In Folsom, first-time violators get a warning. A second violation within one month could result in the customer getting their water shut off. A third violation within six months brings fines.

"If we do not achieve voluntary compliance through personal contacts and written warnings, we will impose penalties," Folsom City Manager Kerry Miller warned in a written statement.

Folsom Lake is one of the principal recipients of water from Sierra Nevada snowpack. While recent storms have piled up the snow, it hasn't lowered the state's drought concerns.

That snowpack, the state's most important water bank, stands at just 76 percent of average and is even lower in the northern Sierra, home to the state's largest reservoirs.

State climatologists estimate there is only a 10 percent chance the Sierra Nevada snowpack will be restored to "normal" levels with the time remaining in the winter season. Even if normal snowfall does arrive, officials say it won't be enough to break the drought because reservoirs are so depleted.

Residents throughout the Sacramento region can obtain water conservation tips and rebates, and schedule a free water audit, by contacting the Regional Water Authority at www.rwah2o.org" target="_blank">http://www.rwah2o.org or (916) 967-7692.

Call The Bee's Matt Weiser, (916) 321-1264.