Groundwater, the fresh water found in layers beneath the earth's surface, is the largest and most accessible source of fresh water in California.
The Oxnard Plain has been a rich agricultural community for more than 150 years requiring large amounts of fresh water for irrigating crops. During the 19th and 20th centuries wells were drilled into the aquifers to access this water. Increased pumping over the years caused the aquifers' water levels to ultimately drop below sea level resulting in seawater intruding into underground basins, contaminating groundwater which could no longer be used for agriculture or residential uses. . This salt water intrusion primarily affects a 23-square mile area of the Oxnard aquifer from Point Mugu northward to the Santa Clara River, referred to as the Oxnard Forebay.
Combating this salt water intrusion is a primary focus of the United Water Conservation District (United). While the region annually receives between 5 and 45 inches of rainfall, it is often not enough to replenish the close to 200,000 acre-feet of water pumped from area wells each year. United recharges a significant amount of high quality water each year (the amount depending upon local rainfall) to underground aquifers to ensure adequate supplies during drier seasons.
Since 1984, United's constituents have invested more than $50 million dollars to design and complete projects such as the Freeman Diversion Improvement Project, the Pumping- Trough- Pipeline, and for the annual importation of 5,000 acre- feet of State water. Together, these projects provide an average of 60,000 additional acre- feet of fresh water annually to the basins, and help reverse the effects of seawater intrusion.