Wet Winter May Not Ease Effects of Drought : Weather: Experts link relief for Southern California not only to a season of heavy rain and snowstorms, but also to their timing.

As a light blanket of early snow fell on highest elevations of the Sierra Nevada, concerned water officials were warning Tuesday that even a season of heavy rain and snowfall may not relieve California completely from the effects of four years of drought.

“Unless Mother Nature cooperates and gives us a bumper crop of snowfall in the mountains of the West, we’re going to have real extreme drought conditions going into next spring,” Michael Hudlow, director of the National Weather Service’s Hydrology Office, said in Washington, D.C.

“Areas like California are particular crisis points,” he added.

To be freed from drought conditions, Southern California in particular depends not only on heavy rains and snows, state and local water officials said, but also on their timing. They must come soon and continue steadily through the winter.

Larry Gage, chief of the schedules and analyses branch of the state Department of Water Resources, said that after four years of drought the state has depleted its reserves at the San Luis Reservoir, a storage facility south of the Sacramento-San Joaquin Delta that collects much of the water for Southern California.

But the San Luis, he said, has its own peculiarities--limited pumping capacity makes it impossible to refill the reservoir quickly. To replenish the storage facilities, he said, the pumps need a slow steady water supply; they cannot keep up with a sudden abundance of water.

“The San Luis is our major problem south of the delta,” he said. “We would like to be pumping at maximum now and we’re not.”

To ease the drought enough to make normal water deliveries in the south, officials estimated that rain and snow runoff in the north this year must be at least 70% of normal. To replenish reservoirs, they said, the runoff must be 105% of normal. However, even if the runoff reaches these levels, the San Luis would still have problems if most of the runoff comes too late.

State and local officials differed on how late is too late. Metropolitan Water District officials believe summer water shortages already are inevitable.

“No matter how much rain and snow we receive from this point forward we cannot pump the water from the north, through the delta and into the San Luis Reservoir in sufficient quantities and meet normal summer demands,” said MWD spokesman Bob Gomperz. “We cannot squirrel enough water away to meet summer demands even if it rains for the rest of the year.”

Gage was more optimistic. He said normal water deliveries can be made to the south if the delta has “excess conditions” by Jan. 1 and then continues to have above normal rainfall. “Excess conditions” means the delta would have enough water to meet normal demands plus begin to refill the reservoir, he said.

For Southern California, the delta is critical because it feeds the State Water Project, a system of dams, reservoirs and pumping stations. The MWD, a water wholesaler, draws more than half its water from the State Water Project to supply customers in Southern California, including the city of Los Angeles. In recent years, environmental concerns and the drought have required the city to rely more heavily on the MWD for its water.

Douglas Priest, director of the department’s drought center, said the rainfall outlook either for the state as a whole or the San Luis in particular is not good. In October and November, he said, rainfall has been about 25% of normal.

“You have to remember this follows four very dry years,” he said. “So we’re starting off awfully slow. We can’t say it looks real good from that perspective although we’ve had a lot of years with dry Octobers and Novembers that have come back and had very wet winters.”

If California experiences a fifth dry year in 1991, state water officials have already warned that agriculture may have to cut 60% to 65% of its share of state water while municipal and industrial users would be reduced by 15%.

In Washington, Hudlow of the National Weather Service said that short supplies of clean water could rival oil as one of the nation’s most serious concerns unless the country starts to implement strategies to better manage water resources.

Hudlow also said that the weather service has completed more than two decades of research for a new water supply forecasting system, which is being tested in the Colorado River Basin Forecast Office in Salt Lake City.

The Water Resources Forecasting Service feeds into a computer long-range climate and weather trends. The system studies historical patterns, compares them to current trends and then calculates the probabilities of floods, drought or a return to normal conditions both for the coming season and further into the future.

The system could be put into national service by 1992 if funds are made available.

“The potential is tremendous in California,” Hudlow said.

The new system could provide local water managers and civil defense officials probabilities of danger or drought as much as a year in advance, Hudlow said. Current long-term weather forecasts do not extend beyond two or three weeks.

Ellis reported from Sacramento. Toth reported from Washington.