The Marine Corps Base, Twentynine Palms, Calif., pumped 2,600 acre-feet of water in 1975 from five supply wells in the Surprise Spring subbasin. The water levels in those wells declined an average of 35 feet in the preceding 10 years. This decline is a result of (1) the proximity of Surprise Spring fault, a ground-water barrier; (2) the close spacing of wells; and (3) the large volume of water extracted.
At the present rate of water-level decline, the pumping water levels will be below the pump intakes by 1980. The projected water demand for the base will increase to 3,000 acre-feet per year by 1980.
To help evaluate the geohydrologic properties of Surprise Spring subbasin, three test holes were drilled northwest of the present well field. That area shows promise of being a good location for drilling three new supply wells. The addition of these new wells to the water supply will reduce the pumping stress from the existing supply wells and reduce the rate of decline.
With an estimated 600,000 acre-feet of ground water remaining in storage after 22 years of pumping and with a projected water demand of 3,000 acre-feet per year, Surprise Spring subbasin, if properly developed, could supply the base for many years to come.
