Proposed water supply augmentation for Tucson, Arizona

Abstract

Tucson, Arizona, with a 1950 population of 64,000 and a projected population exceeding 800,000 by the year 2000 remains one of the fastest growing areas in the United States. This growth has created an ever increasing demand for water with resulting increased impacts on local aquifers. Continued water-level decline, decreased pumping capacities, and potential land-surface subsidence have heightened the need for alternative water resources. Central Avra Valley is a recommended source area. A hydrologic evaluation of central Avra Valley was conducted and a proposed well field was identified. Comparison of present hydrologic conditions with those existing in 1952 show that the water table has declined more than 150 feet in certain areas of Avra Valley. A storage coefficient of 0.15 was selected based on previous investigations, and aquifer transmissivity values of 35,000 gpd/ft (4,700 ft²/day), 50,000 gpd/ft (6,700 ft²/day), and 150,000 gpd/ft (20,000 ft²/day) were assigned to the proposed well field. Ground-water quality meets all domestic requirements. Water-level declines from 20 wells each discharging at 1,000 gpm (134 ft³/min) over a 10-year interval ranged from less than 20 feet to more than 96 feet. These results suggest that the proposed well field could be used to meet projected demands for water through the year 2000.