Sufficient ground water to provide about 2.1 million acre-feet in a 25-year period is available for delivery to the Ak-Chin Indian Reservation from Federal land in the Vekol Valley, Waterman Wash area, and Bosque area in south-central Arizona. Withdrawal of 85,000 acre-feet per year as required by the Ak-Chin water-supply act--Public Law 95-328--will greatly deplete the amount of water in storage and may cause land subsidence in the areas. Study concurrent with well-field development will enable design changes to minimize pumping costs , water-level declines, movement of poor-quality water into the well fields, and potential land subsidence and associated earth fissures. Surface and bore-hole geophysical testing, aquifer tests, and the development of simulative mathematical models will accomplish these goals and permit quantitative evaluations of the potential deleterious effects resulting from development of the water supply. (Woodard-USGS)