Three Reservoirs Forced to Release Water : Drought: The flow from two lakes can be recaptured, but about 13,000 acre-feet spilled from Castaic Lake will be carried into the ocean.

This week’s heavy rains have forced state water officials to open the gates on three Southland reservoirs, spilling considerable volumes of water that in one case cannot be captured before flowing into the Pacific Ocean.

As of late Friday, about 13,000 acre-feet of water--enough to serve about 20,000 families for a year--had been spilled from Castaic Lake into the Santa Clara River, which carried the flows into the sea near Oxnard.

Releases were also made from two other reservoirs--Pyramid Lake near Gorman and Silverwood Lake in the San Bernardino Mountains. But that water either poured into downstream reservoirs or soaked into underground basins, where it can be pumped for later use.

With California trapped in a sixth year of drought, the lost water represents a minor embarrassment for the state Department of Water Resources. On Friday, the department confirmed that the Metropolitan Water District of Southern California and other customers on the State Water Project will be forced to live with just 20% of their requested water deliveries for 1992.

But officials who run the state’s intricate system of pumps and dams said that this week’s deluge made releases of water unavoidable--and added that more would likely be spilled with the arrival of weekend storms.

“We haven’t had to make releases of this volume (from Castaic) since the big storms of 1983,” Lonnie Long, chief of field operations for the water department’s southern district, said Friday. “I know it’s hurting everybody to watch that water run down the river, but this is a heavy storm. You can’t predict this sort of thing.”

Long said the reason for the release at Castaic was that the reservoir was at 90% of capacity when the rains began Monday. He said the lake is kept nearly full to guarantee that Southern California has an emergency supply in the event of trouble on the California Aqueduct, which carries water south from the state’s major reservoirs.

Those who could be hurt most by the wasted spillage are water districts downstream of Castaic that are entitled to all of the runoff flowing into the lake during storms. Contracts say the state must give these districts every gallon of rainfall that winds up in the lake.

Under normal conditions, that runoff is released slowly and percolates through the soil into ground-water basins. But in this case, the volume and velocity of the water released are greater, and thus most of the flow is rushing out to sea.

“We definitely don’t like to see this,” said Jim Gross of the United Water Conservation District, which supplies the cities of Oxnard and Port Hueneme as well as numerous farmers.

Gross said that in addition to the rains, diversions from Pyramid Lake near Gorman have helped raise the level at Castaic, thereby causing excess spillage. Normally, storm flows into Pyramid Lake are released by the state into Piru Creek, which flows into a reservoir owned by the United Water Conservation District.

But when the gushing creek began eroding an old highway this week, releases were cut until work crews repair the damage.

“If we are told we have lost water because of poor maintenance along a highway, we won’t be too happy about that,” Gross said.

Spillage from Silverwood Lake--where the state stores water heading for the Inland Empire and Orange and San Diego counties--is draining into the Mojave River Basin, where it can be pumped by desert cities that rely on ground water.

Rain and snow continued to fall in Northern California on Friday, but experts said 1992 was still shaping up as a critically dry year. Precipitation levels at eight key measuring stations stood Friday at about 60% of average.

The water content of the Sierra Nevada snowpack stands at just 58% of the average for mid-February.

Times staff writer Virginia Ellis in Sacramento contributed to this story.