About 800,000 residents in western San Bernardino County could be hit with mandatory conservation requirements next year and higher water rates in 2009, officials said Tuesday.

Extreme drought conditions and a recent court order requiring that water supplies from Northern California be reduced to save an endangered fish have forced Southern California's largest urban water supplier to consider drastic measures.

"The bottom line is Southern California is facing a critical situation," said Bob Muir, spokesman for the Metropolitan Water District of Southern California. "We're trying to exhaust all avenues when it comes to voluntary conservation. We're trying to stave off any mandatory requirements."

The MWD supplies about 30 percent of the water consumed by customers of the Inland Empire Utilities Agency, which serves Chino, Fontana, Montclair, Ontario, Rancho Cucamonga, Upland and Chino Hills.

The rest of the water comes from ground water, recycled water and flows from the San Bernardino Mountains.

The MWD is working with the IEUA and other member agencies on voluntary conservation efforts.

The Chino-based IEUA is challenging residents to save 20 gallons of water per day by changing outdoor watering habits, using low-flow toilets, fixing leaky faucets and taking other simple actions.

"This is the driest year on record," said Sondra Elrod, IEUA spokeswoman. "Our message is it's time to get serious about water conservation."

But the voluntary steps might not be enough.

In January, the Board of Directors for the MWD will consider implementing "extraordinary" conservation measures, which could mean forcing cities and member agencies to impose watering restrictions, Muir said.

The board could approve rate hikes of 5 percent to 10 percent in 2009 in order to secure or maintain water supplies, Muir said.

The MWD in January will reduce water deliveries to agricultural customers by 30 percent.

Muir said the MWD also is looking to purchase water from other agencies in the state through water transfer agreements.

He said the board will discuss a plan to deal with potential water shortages at its January meeting.

Martha Davis, IEUA executive manager of policy development, said any increases approved by the MWD would be passed on to local residents.

"For customers, it would mean that rates would go up and the retail agencies would need to conserve more and do more to develop local water supplies that are less expensive than imported water," Davis said.

The IEUA is reducing its reliance on water from Northern California by enhancing conservation and water-recycling efforts, Davis said.

In the next three years, Davis said the IEUA wants to increase its use of recycled water from 13,000 acre feet a year to 50,000 acre feet a year.

An acre foot is typically enough water to serve two families of four for a year.

Several factors are contributing to the water woes in Southern California.

San Bernardino and Riverside counties, which typically get an average of 13 inches of rain annually, have this year received only about three inches, Davis said.

In addition, the Colorado River is in its eighth year of drought and the watershed feeding the system that supplies water from Northern California has had the driest year in decades, Muir said.

Furthermore, a federal judge's ruling expected to take effect next year would reduce by 33 percent the amount of water pumped from the Sacramento-San Joaquin River Delta. The ruling is meant to protect the delta smelt, a small fish threatened with extinction.

Davis said the water situation could get worse if La Nina weather conditions prevail next year. La Nina usually means very little rain, she said.

"It's very likely that if next year is dry there will be mandatory requirements for water conservation," Davis said.