With new evidence that seawater has breached the county's largest underground source of fresh water, officials have enacted an emergency ban to prohibit new wells on the Oxnard Plain and proposed a permanent ordinance to reduce water consumption there by 25%.
Tests in November warned growers and the four cities that depend on the ground water that the county's deepest underground pools might have been contaminated with seawater. Results from the U.S. Geological Survey announced Friday confirmed those suspicions.
"There is almost no doubt that this is lateral seawater intrusion," county hydrologist John Turner told the Fox Canyon Groundwater Management Agency on Friday. The public agency regulates ground water usage on the Oxnard Plain.
The emergency measure, which expires in six months, permits water users to replace wells as they go dry or break down, but prohibits new wells.
"This is not a moratorium," said grower Lynn Maulhardt, chairman of the Groundwater Agency board. But, he added, it does prohibit growers from irrigating new farmland that has not previously used county water.
Seawater contamination can make water unsuitable for crops or municipal use, water experts say.
Growers who packed the board hearing room last week sat quietly as the emergency ban was discussed. Rex Laird, executive director of the Ventura County Farm Bureau, said the growers understand the need for the restrictions.
"There is a finite water capacity," Laird said. "The issue is going to have to be addressed whether we like it or not."
Only one person, representing an industry association of well drillers, pump contractors and engineers, spoke in opposition to the emergency ban. Larry Rottman of the California Groundwater Assn. threatened to sue the board if it passed the ordinance.
Nevertheless, the agency passed the measure 5 to 0 and instructed its staff to prepare a permanent ordinance to replace the temporary measure when it expires.
The county's deep ground water system, which includes the large Fox Canyon Aquifer, was previously believed to have remained pure despite six decades of pumping more water than rainfall could replenish.
Officials have known since the 1920s that overdrafting allowed the gradual encroachment of seawater into the more shallow aquifers. But over the past several years the 800 water users on the Oxnard Plain, including the cities of Ventura, Oxnard, Port Hueneme and Camarillo, dug their wells deeper to find fresh water.
Deeper wells and the past three years of drought have strained the lower ground water system, a series of deep freshwater pools, and allowed the seawater to move in, Turner explained.
Those wells pump about 150,000 acre-feet of water per year out of the Oxnard Plain, Turner said. The ban would prohibit pumping to irrigate the 3,700 acres of agricultural land in the area that currently is not irrigated. Turner estimates it would take a maximum of 10,000 acre feet of water annually to irrigate that land.
An ordinance to reduce pumping 25% by 2010 will affect far more growers and water users than the emergency ban, officials said. That ordinance calls for the first 5% cut in consumption by 1992, with 5% decreases every five years until 2010.
By that time, according to officials, the lower ground water system should reach the point at which water draining into the underground pools is equal to or more than the quantity being pumped out. That point is called safe yield.
The ordinance uses historical records on water use to determine individual water allocations. If growers already are using water efficiently, and can prove that they use less water than other growers with similar crops, their allocations can be adjusted, according to the ordinance. Fines would be assessed ranging from $50 to $200 per acre foot above allocations.
The next public hearing on the ordinance is planned for Feb. 23 in the county Board of Supervisors Hearing Room. Officials hope to have the ordinance adopted and in place by late spring.