The thrust of California's problem is a loss of flexibility in its water system, reigniting decades' old disputes pitting farmers and growth advocates against conservationists and Indian tribes, and the water-rich northern end of the state against the arid south.

The system carries water to 34 million people, a number growing at about 750,000 - the population of San Francisco - every year for the next eight years.

It also sustains a $27 billion a year farming industry - the nation's biggest and the largest water consumer in California - hydroelectricity plants that generate up to 25 percent of the state's power needs, and populations of threatened fish protected by federal laws.

But some of California's biggest water sources are shrinking, including the 1,400-mile (2,240-km) Colorado River, shared by seven states and Mexico.

California, after decades of siphoning off the lion's share of Colorado River water, is now being forced by booming neighbors like Arizona to cut its take by 15 percent over the next 15 years.

The vast snowfields of California's Sierra Nevada mountains are its other big source of water.

One problem is uneven runoff, forcing some reservoirs to spill water to avoid possible flooding later in the season while other reservoirs end the rainy season barely half full.

A separate but significant problem is crumbling pipelines, such as in the San Francisco Bay Area, which faces a multibillion dollar price-tag to upgrade its largest water system, which includes lines that date back nearly 100 years.

California will spotlight its water predicament April 16 in the second of what is likely to become an annual event, said Jeff Cohen of the California Department of Water Resources, which is sponsoring the meeting.

LIKE POWER, CONSERVE

"The water problems in California have been below the radar because Mother Nature gave us an unusually wet period the six years before 2001," said Peter Gleick of the Pacific Institute for Studies in Development, Environment and Security.

A new wrinkle to the problem is meeting the requirements of a growing population without building more dams, which these days are almost certain to wither on the drawing board amid litigation over property rights and environmental impact.

Like last year's power crisis, tamed in part by widespread conservation, California looks to make efficiency a major tool in combating its looming water problems.

Last week, for example, a state panel discussed ways of using more recycled water, setting a goal of providing enough recycled water for up to 1.5 million people by 2010.

"The good news in all this is that California is rethinking how it uses water. Many cities don't use as much water as they did 10 years ago. We're doing more with our water," Gleick said.

Farmers have made big strides, armed with better weather forecasts, better knowledge about crops' water needs, and improved irrigation techniques.

The California Farm Bureau said farmers grew 67 percent more crops in 1995 than in 1967 with 2.5 percent less water.

New homes are also using more efficient household appliances, like low-volume flush toilets, which can use around 1.6 gallons (6 litres) of water each flush compared with older models, which could drain around 6 gallons (23 litres).

On the legislative side, two bills were signed into law last autumn, one requiring housing developers to show they have lined up enough water rights to serve a development for at least 20 years, the other requiring local water agencies to determine whether there is enough water to meet the needs of mall and housing projects.