Deluge Has Silver Lining for Water District Officials

Not all of Tuesday’s rain meant trouble for Orange County.

Some 6,700 acre-feet of fresh rainwater that backed up behind Prado Dam will save northern and central county water customers about $1.7 million, Orange County Water District officials said.

But that’s about the only silver lining in the clouds that moved through Tuesday, taxing flood-control systems, storm drainage and the patience of commuters.

Usually, heavy rains like Tuesday’s have little effect on the aquifer beneath Orange County, which provides about 75% of the water to customers roughly north of Lake Forest but none to those farther south, where there’s limited ground water available. The rest of the water is bought from the Metropolitan Water District of Southern California.

The problem with heavy rains is that they lead to heavy and quick runoffs. To replenish the aquifer--imagine a massive underground sponge--rains need to be long and steady, giving water time to soak deep into the ground.

But some of the rain that fell Tuesday into the Santa Ana River watershed northeast of Orange County was diverted to a retention area behind Prado Dam--Spanish for “green meadow”--which lies to the north of the Riverside Freeway west of Corona.

The reservoir was nearly empty before Tuesday’s storm hit. By the time it ends, the reservoir will hold $1.7-million worth of water, said Jim Van Haun, associate general manager for the Orange County Water District.

“That’s the value of the storm to the water supply, and the economics of the water supply,” Van Haun said. “We don’t have enough water to serve the 2 million customers, so we have to purchase the water from the Metropolitan Water District. It costs $250 per acre foot.”

Van Haun said that the massive runoff isn’t necessarily a lost opportunity because the aquifer “is in good shape right now.”

“We don’t have anything like the drought in the late ‘80s and early ‘90s,” he said.