WATER WORRIES HIT LOS ANGELES GLOBAL WARMING COULD AFFECT WATER SUPPLY.

Byline: Kerry Cavanaugh Staff Writer

Worried that global warming could impact Los Angeles' water supply, the Department of Water and Power is studying how to deal with potential changes in supply and demand.

Higher temperatures likely mean more rain and an early Sierra Nevada snowpack melt, possibly overflowing reservoirs and aqueducts in the spring when the water isn't needed, officials said. Locally, summer demand for irrigation and household water is expected to rise with the mercury.

``Climate change is happening. Everybody has to come to grips with that and there may be impacts to the water supply,'' said Alvin Bautista, a water services engineer overseeing the DWP's long-range water plan.

Climate change is triggered by the addition of heat-trapping gases, including carbon dioxide, methane and nitrous oxide. The National Academy of Sciences estimates that Earth's average surface temperature could rise by 5 degrees in the coming century.

In general, scientists figure rainfall will increase, but warmer weather would dry soil faster, raising the chance of drought in dryer regions. Researchers are still trying to figure out how climate change will affect local environments.

Southern California is especially susceptible to the impacts of global warming because the region depends on imported water from the Colorado River and the Sierra Nevada, where researchers have already begun to see earlier snowmelt and less spring runoff.

Statewide, water agencies have been slow to respond to the effects of climate change that were first predicted 20 years ago, said Peter Gleick, president of the Pacific Institute, an independent think tank based in Oakland.

``We have to explore how sensitive we are to the changes that are coming. It's possible we could manage our water system differently and handle the change.

``Climate change is inevitable. How bad it is depends on how prepared we are for it.''

Bautista and a group of DWP engineers have begun running various climate scenarios through computer simulations, analyzing what would happen to drinking water supplies if the snowpack were reduced by 10 percent, 15 percent or 20 percent, or if the snow began to melt earlier.

``The hottest months in Los Angeles are typically August, September and sometimes July. If the water comes down earlier, we'll have to keep it in the system if the demand is not there,'' Bautista said.

In a draft of its 2005 Urban Water Management Plan, DWP analysts wrote that the city may have to rely less on imported water - which now makes up 85 percent of the city's supply - and develop more local resources.

That could mean cleaning up contaminated groundwater, capturing and using storm water, recycling treated sewage water or building a desalination plant to purify seawater.

While researchers try to understand how higher temperatures will affect snow and rain in the mountains, Bautista said Los Angeles has already seen the effect of higher temperatures locally.

``The only definitive thing is warming in Los Angeles city high temperatures and that's driving up demand.''

So the DWP must encourage Angelenos to conserve more water. The utility plans to step up its education campaigns that encourage people to plant drought-tolerant landscaping and not over water their yards.

The Metropolitan Water District of Southern California has a multimillion-dollar publicity campaign to promote native plants and to teach residents how to use water wisely.

The MWD imports water for 17 million customers from Northern California and the Colorado River and has been studying the potential impacts from global warming for the past five years.

``There's no model out there that's going to tell you exactly what's going to happen in your area,'' said Steve Arakawa, MWD manager for water resources.

The district has tried to become less dependent on those two major sources by increasing conservation, building the new Diamond Valley reservoir in Riverside County and funding new recycled water projects throughout the region.

Ruben Aronin with the nonprofit Global Green said he worries that agencies and individuals won't make lifestyle changes until there's a crisis.

``We're going to have to be increasingly innovative in a desert landscape.''

Kerry Cavanaugh, [phone]

kerry.cavanaugh(at)dailynews.com