Seawater intrusion, ground-water pumpage, ground-water yield, and artificial recharge of the Pajaro Valley area, Santa Cruz and Monterey Counties, California

The Pajaro Valley area, California, covering about 120 square miles (310 km²), extends from the southern part of Santa Cruz County to several miles south of the county line into Monterey County. It borders the Pacific Ocean on the west and the Santa Cruz Mountains on the east. The city of Watsonville is the largest center of population.

Seawater intrusion is occurring in the Pajaro Valley area from several miles north to several miles south of the mouth of the Pajaro River and in a small area about 4 miles (6.5 km) north of the river. The intrusion extends inland about 1 mile (1.6 km). Two water-bearing zones are being intruded--the depth intervals 100-200 feet (30-60 m) and 300-600 feet (90-180 m).

Ground-water pumpage averaged 49,100 acre-feet per year (60.6 hm³/yr) for the 9-year period 1963-71. The long-term ground-water yield of the Pajaro Valley is about 44,000 acre-feet per year (54.3 hm³/yr). Artificial recharge can be effected through modified streambeds at infiltration rates as high as 3 feet per day (0.9 m/d). Injection wells may have recharge capabilities of as much as 500 gallons per minute (1.9 m³/min).