Water resources of the Santa Rosa Indian Reservation and vicinity, Riverside County, California

Additional water for irrigation is needed by the Santa Rosa Indian Reservation, Riverside County, California. Water in the area is derived from precipitation, which averages 12 inches annually, on three subbasins nearly surrounding the 17-square-mile reservation. No ground water flows in from outside the area. A supply well that taps sandy material overlying the pre-Tertiary basement complex showed a specific capacity of 0.4 gallon per minute per foot of drawdown. Estimates of specific yield for material encountered during drilling of three wells and a test hole ranged from 5 to 10 percent. A gravity survey outlined the thickest section of the aquifer in the Vandeventer Flat area, and test wells are proposed to determine its potential well yield. Damming streams to retain runoff (about 1,500 acre-feet per year, and more during periods of heavy precipitation) is also proposed. Analyses of water from the supply well and five major springs showed that ground water is suitable for irrigation except at Sulphur Spring, where the percent sodium of 97 exceeds recommended maximums, and at Bull Canyon Spring, where the specific conductance of 1,300 micromhos indicate a salinity hazard. (Kosco-USGS)