Rain Clouds Had Silver Lining for Water Supply : Drought: Recent storms could be worth up to $25 million and help keep water bills from rising.

The recent torrential rains have been like pennies or, more accurately, millions of dollars, from heaven for the San Gabriel Valley.

The monetary value of all the moisture that has fallen on the region in the past two weeks, water officials say, could be worth as much as $25 million.

As the rainwater and runoff from the San Gabriel Mountains percolates underground, it could raise the water table by 15 to 25 feet throughout a vast part of the region, said Steve Johnson, an engineer with West-Covina based Stetson Engineers Inc., which provides data to local water agencies.

A one-foot increase in the water table represents about 8,000 acre feet of water--enough for 16,000 families for a year--or more than $1 million worth of water, Johnson said.

Eventually, the officials say, the change in the water table could have a positive effect on water bills paid by San Gabriel Valley residents and businesses from Pasadena to Pomona. Although it is doubtful that water bills would decrease, the bounty brought by the storms will probably prevent further increases, they said.

Nonetheless, it will be a few more weeks before officials can calculate precisely how much water percolated underground in the region. Regardless, they said, the rains--although devastating in terms of lives lost and property damage--were a boon to the drought-thirsty, local water supply.

“When that water reaches the underground, it’s worth a lot of money to us,” said Robert G. Berlien, general manager of the Upper San Gabriel Valley Municipal District.

“If you’re looking for me to say the drought is over, I’m probably not going to say that,” he said. “But in the San Gabriel Valley, where we rely 90% on ground water, the rainfall is a major improvement.”

Unlike many areas of Los Angeles County, which depend heavily on imported water, much of the supply for a majority of the communities in the San Gabriel Valley comes from underground. A series of dams and spreading grounds that have been in place for decades help to replenish the region’s water table.

“I’ve been hearing on the radio that the storm won’t have a big effect on the drought,” said Carol Williams, administrative assistant for the Main San Gabriel Basin Watermastercq, an agency that oversees pumping rights. “But here, in our valley, it’s going to help considerably.”

The San Gabriel Valley has three major underground basins that percolate water for most of the region.

The largest--the Main San Gabriel Basin--stretches from Alhambra to San Dimas. About 90% of the water, distributed by dozens of public and privately owned water agencies in the region, comes from this basin, which is fed by local rainwater runoff. The remaining 10% comes from afar--Northern California, the High Sierra and the Colorado River--and principally is distributed by the Metropolitan Water District of Southern California.

In the west, underlying the Pasadena area, is the Raymond Basin, which provides close to 40% of the water needs for that part of the region. The remaining water is from the MWD.

In the east, beneath the Pomona and Walnut areas, are two separate, but related, basins. Together they supply about 40% of the needs for the Claremont-based Three Valleys Municipal Water District, the provider to 26 smaller water agencies in the region. Like the Pasadena area, it relies on the MWD for the majority of its water.

“A lot of people really hate this rain,” John Maulding, executive director of the Main San Gabriel Basin Watermaster said last week as the rains were still coming down. “But we look at it as a real godsend.”

Throughout the San Gabriel Valley during the past two weeks, the rain came down in torrents.

Devil’s Gate Reservoir in Pasadena last week was at the highest level in its 72-year history, water officials said.

Susan Nielsen, principal engineer for water quality and supply for Pasadena’s water system, said the recent rains “certainly helped” boost the level of the underground basin, but “we still need more.”

In the San Gabriel Mountains, three major dams along the San Gabriel River hold water for distribution into “spreading grounds” downstream, including the Santa Fe Dam area in Irwindale.

A portion of the mountain runoff comes from Cogswell Reservoir where, in the eight days from Feb. 9 to 16, it rained more than 22 inches. The average annual rainfall there is 32 inches.

In addition, for the first time since 1983, water flowed over the spillway at Morris Reservoir in the San Gabriel Mountains and has been going over it periodically since last Thursday, although it has posed no major flood control problems, county water officials said.

All of this water, Johnson said, will boost the reading downstream in Baldwin Park at the key underground well that indicates the depth of the water supply. In March, 1991, the well recorded the least amount of water ever at that site since the early 1900s.

Officials said the current water shortage has been made worse by overpumping, by which more water is taken out of the ground than nature, or humans, put back. For example, most of the region’s sewage waste water, which used to remain within the water table, is now treated and pumped out via the San Gabriel River. Only a small portion is reclaimed and recirculated into the basin.

The region’s population explosion also has aggravated the water shortage, officials said.

Among the water districts particularly affected by population increases is Three Valleys, whose service area includes the fast-growing cities of Walnut and Diamond Bar, which both rely 100% on water from outside sources.

“The rains are great,” said Three Valleys general manager Richard W. Hansen.”But you’re not going to recover from five years of a drought in one rainstorm.”

The message still, he said, is: “Use water wisely.”