Well-Preserved : Defying a Withering Drought, an Underground Basin Keeps Rising

Beneath a series of wellheads along a dry Somis creek bed lies a mystifying underground basin that is flush with water in the midst of an unrelenting drought.

Elsewhere in Ventura County, scores of wells are running dry or mining from record depths. But well levels of the Zone Mutual Water Co. basin rose as much as 25 feet in the last year, and there was no need for the rationing being imposed in neighboring water districts.

“It is kind of a mystery,” said Richard Underwood, 74, a Somis farmer who uses the wells to irrigate 250 acres of lemons and vegetables. “It’s been building up for a long time.”

Zone Mutual, a growers cooperative founded in 1922, provides irrigation water to 90 ranches in a nine-square-mile area of Somis. Among the nearly 200 water purveyors in the county, it is one of the few that has seen well levels rise during the drought. And no other district has seen them rise so dramatically, water experts said.

The water depth in the company’s basin wells has risen from about 200 feet to 90 feet since 1960, and jumped 50 feet in the last three years. Hydrologists have pinpointed a number of possible sources for the bounty--including ground-water runoff from two sewage treatment plants--but admit that the true source is anyone’s guess.

“We had a geologist out here a few years ago who gave us all sorts of explanations, but none of the professionals really seem to know,” said William S. Radford, the company’s manager.

Growers dependent on Zone Mutual’s wells say that the water is unfit for human consumption and that its high chloride concentrations are reducing the potential yields of their crops.

“You look at the soil where we’re irrigating and it’s turning white or a bronze color because of the salt buildup,” said John W. Borchard Jr., whose family owns 680 acres of lemon, orange and avocado groves. “It’s having a detrimental effect on the size and quality of the fruit and on the health of the trees.”

But poor as the water is, the growers have been living with it for decades and are glad to still be flush when the county is in its fifth year of drought, Borchard said.

“They’re in better shape than the rest of the county,” said Lavern Hoffman, a county ground-water expert who said the rising well levels will reduce the company’s pumping costs.

Zone Mutual’s pump house still employs much of its original equipment. The company pumped 6,000 acre-feet in 1990, enough to cover as many acres with a foot of water.

Besides its six basin wells, Zone Mutual draws from four wells in Fox Canyon that descend to more than 600 feet. Those wells furnish high-quality water containing only about 30% of the basin wells’ mineral content. It costs about 25% more to pump out that water, which is blended into basin supplies to improve overall quality, Radford said.

But even with all of that water in storage, Zone Mutual’s customers are anxious for rain. A good rainstorm would help heal crop damage by cleansing the soil of salt deposits, said Darrell Nelson, president of a Santa Paula firm that conducts annual tests for Zone Mutual.

As for the bonanza in the basin wells, county hydrologists have identified three possible sources:

* “Dewatering” wells in Simi Valley: In 1973, that city abandoned its heavily mineralized ground-water system and began buying imported water from the Calleguas Municipal Water District. Wells that had supplied farmers and the city were shut down. But the water from the wells has kept coming.

The five wells today dump about 2 million gallons of water daily into Arroyo Simi, which becomes Arroyo Las Posas and, eventually, Calleguas Creek. Experts say a sizable percentage probably seeps into the ground and into Zone Mutual’s basin.

* Simi Valley’s waste-water treatment plant: An estimated 9 million gallons of treated water is discharged from the plant into Arroyo Simi each day. Like the water from the city’s runoff wells, the effluent usually seeps into ground-water aquifers and eventually into Zone Mutual’s basin beneath Arroyo Las Posas 12 miles downstream.

Michael Kleinbrodt, Simi Valley deputy public works director and district engineer, said the effluent is a likely source of Zone Mutual’s rising well levels.

* Ventura County’s water treatment plant in Moorpark: About 1.8 million gallons of treated water from the plant runs into 30 acres of man-made ponds at the plant site and drains into the ground.

Waterworks Manager Reddy Pakala said a portion of the plant’s discharge probably migrates underground into Zone Mutual’s basins. But he said the plant’s daily flows have dropped 6% in the last 12 months.

“We have not increased our flow, but it is recharging the ground-water basin,” Pakala said. “Just how much is going where is very difficult for anyone to tell.”