Geohydrology of part of the Round Valley Indian Reservation, Mendocino County, California

The Round Valley Indian Reservation in northern California obtains most of its water from the ground-water reservoir. The ground-water reservoir is made up of continental deposits, alluvium, and stream-channel deposits ranging in age from Pliocene to Holocene. Most of the water is pumped from the alluvium. Most ground water (about 20,000 acre-feet or 25 cubic hectometers per year) is derived from stream seepage. Natural discharge (discharge to streams, evapotranspiration, and underflow) has averaged about 21,000 acre-feet per year. Pumping and flow from artesian wells has averaged about 2,750 acre-feet per year. Ground water occurs in both confined and unconfined aquifers. The ground-water reservoir is full, and about 230,000 acre-feet of water is stored in the depth interval 10-200 feet. The water is chemically and biologically suitable for domestic or irrigation use, although hardness is high for domestic use and, locally, dissolved iron is a problem. There is potential for developing additional ground-water supplies. (Woodard-USGS)