By John A. Izbicki
U.S. Geological Survey Fact Sheet 126-96
Management Strategies
Isotopic data show that recent recharge occurs primarily as infiltration of surface water from large streams. Water from these sources does not effectively recharge the lower aquifer system or aquifers in parts of the basin that are distant from these large streams. In some areas recharge occurs as infiltration of precipitation or as infiltration of runoff in smaller, intermittent streams (especially in areas where flow in these streams has been increased by discharge of treated municipal wastewater). However, in most areas where aquifers are distant from large streams ground water does not contain tritium and, on the basis of carbon-14 data, is very old.
Results of a recently completed U.S. Geological Survey simulation-optimization study of alternative management strategies (Reichard, 1995) showed that ground-water resources in the Santa Clara-Calleguas basin could be used more efficiently by increasing artificial recharge programs and reducing pumping from the lower aquifer system. Local agencies responsible for ground water management are increasing recharge to the upper aquifer system by releasing water for ground-water recharge to the Santa Clara River from Lake Piru (Densmore and others, 1992), increasing the capacity of facilities used to supplement natural recharge through the diversion of surface water, and injecting water in the lower aquifer system and other parts of the basin where present day recharge is scant (Ventura County Public Works Agency, 1995). Local agencies also are proposing to reduce pumping from the lower aquifer system through a combination of water conservation measures, a shift in pumping to the upper aquifer system, and delivery of surface water for agricultural supply to replace ground-water pumping (Ventura County Public Works Agency, 1995). Information obtained from the U.S. Geological Survey RASA study of southern California coastal basins will aid in the development of those projects and in the effective management of the ground-water resources of the Santa Clara-Calleguas basin.