Assessment of the Santa Margarita Sandstone as a source of drinking water for the Scotts Valley area, Santa Cruz County, California

Scotts Valley, Calif., is a rural residential area with a rapidly expanding population. Its mediterranean-type climate yields an average annual rainfall of 40 inches. The Santa Margarita Sandstone is the principal aquifer in the area, supplying about 90 percent of all water for domestic purposes. Sources of recharge for the Santa Margarita Sandstone are natural recharge, subsurface inflow from adjacent areas, artificial recharge, and deep penetration of excess irrigation water. Total domestic water use in 1979 was about 2,600 acre-feet. The quantity of ground water pumped for domestic use is expected to increase at a rate of 7 percent per year. Evapotranspiration, estimated to be about 29 inches per year, is the largest form of ground-water discharge. Ground water from the Santa Margarita Sandstone is generally suitable for domestic use. Potential for water-quality degradation exists from urban runoff, leachates from a solid-waste disposal site, and liquid wastes. Several agencies and individuals monitor surface-water and ground-water quality in the Scotts Valley area. Water from streams and the city of Santa Cruz are potential alternate sources of drinking water for the Scotts Valley area. (USGS)