The Saugus-Newhall area is in the upper Santa Clara River valley, in northwestern Los Angeles. County, about 30 miles north of Los Angeles. The area has two main aquifers, the alluvial aquifer and the underlying Saugus aquifer. These two aquifers are the subject of this investigation. The alluvial aquifer consists of river channel alluvium as much as 200 feet thick with a transmissibility ranging from 50,000 to 325,000 gallons per day per foot and a storage coefficient of i0 to 20 percent. In 1945 about 210,000 acre-feet of recoverable ground water was in storage in the alluvial aquifer. The alluvial aquifer is the major source of ground-water pumpage and has supplied about 600,000 acre-feet of effective pumpage during the period 1945 through 1967. Ground-water pumpage and variations in the quantities of surface-water recharge have caused large fluctuations in the water levels in the alluvial aquifer. The Saugus aquifer has. a maximum saturated thickness of about 3,500 feet and ranges in transmissibility from 2,000 to 200,000 gallons per day per foot. Based on limited available data, the Saugus aquifer may contain as much as 6 million acre-feet of ground water in storage under steady-state conditions. Meager available data indicate the water quality in some areas of the Saugus aquifer is poor so that only a fraction of the ground water in storage in the aquifer may be usable for domestic water supplies. Floodflow in the streams in the area is the major source of recharge to the alluvial aquifer and the underlying Saugus aquifer. The chemical quality of the ground water is largely dependent on the chemical quality of the surface-water recharge. Ground-water discharge occurs along the Santa Clara River below Castaic Junction. Water will be imported to supplement the existing water resources. An analog model of the ground-water basin indicates that it will not be possible to artificially recharge the proposed quantities of imported water into the alluvial aquifer above Saugus unless ground-water pumpage from that area is increased. The model further indicates that the alluvial aquifer may not be able to supply enough water, even when artificially recharged with imported water, to meet the estimated maximum pumping rate to 1990 used in the model and that increased pumpage from the Saugus aquifer may cause water-level declines in both aquifers and may eliminate the natural ground-water discharge from the aquifers.