Seawater intrusion and potential yield of aquifers in the Soquel-Aptos area, Santa Cruz County, California

Seawater has intruded the Purisima Formation in the interval 0-100 feet below sea level in the Soquel-Aptos area. It occurs in the central part of the area and extends inland about half a mile.

The potential yields of the two principal aquifers in the Soquel-Aptos area are 4,400 acre-feet per year from the Purisima Formation and 1,500 acre-feet per year from the Aromas Sand. Pumping from the Purisima Formation, averaging about 5,400 acre-feet per year since 1970, has caused water levels along the coast to decline below sea level and has allowed seawater to enter the aquifer.

Seawater intrusion and ground-water storage could be monitored in all depth zones by expanding the observation-well network to include a number of shallow wells, one deep well inland from the coast, and three deep wells along the coast.