1. Geology and water-bearing deposits.-Indian Wells Valley is virtually a closed basin bordered by consolidated generally non-water-bearing rocks. This basin is filled by unconsolidated deposits of clay, sand, and gravel derived from the mountains and bordering highlands. The principal waterbearing deposits are the younger and older alluviums; a main water body occurs in these deposits, principally beneath the surface extent of the younger alluvium. This estimate of transmissibility, utilized in conjunction with the crosssectional area and the hydraulic gradient of 1921, suggests an underflow at midvalley under natural conditions of about 15,000 acre-feet a year. The underflow is a measure of the recharge and discharge. The quantity of groundwater discharge estimated as the sum of evapotranspiration and groundwater outflow, or about 11,000 acre-feet per year under natural conditions, is about 4,000 acre-feet less than the estimate based on transmissibility, crosssectional area, and hydraulic gradient. 5. Perennial yield.-Perennial yield of a groundwater basin is the rate at which ground water can be withdrawn year after year without depleting groundwater storage to such an extent that withdrawal at this rate is no longer feasible because of increased pumping costs or deterioration of quality. The estimated perennial yield of Indian Wells Valley, based on estimates of evapotranspiration and underflow at midvalley together with other groundwater data, is approximately 12,000 acre-feet per year-about 4,000 acre-feet more than the estimated pumpage in 1953, but about 4,000 acre-feet less than the estimated total discharge.

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Location and general description of the area______________________ Other investigations and acknowledgments______________________ Discharge-point numbering system_____________________________ Geology._________________________________________________________ 6 Structure and landforms_ _____________________________________ Geologic units..

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