Tucson's Needs for Central Arizona Project Storage

Abstract

The future acceptance and utilization of Central Arizona Project water by the City of Tucson Water Utility present many complex technical, economic, institutional, and environmental problems. Since Congressional adoption of the Colorado River Basin Project Act in 1968, Tucson Water engineers have supported the concept of a large CAP raw water storage reservoir near Cat Mountain west of the City. The United States Bureau of Reclamation, in its Stage Two planning for Phase B of the Tucson Aqueduct, has identified four potential storage sites, including the Cat Mountain location, for economic and environmental evaluation in conjunction with two basic aqueduct alignments. Engineers of the municipal water utility have utilized available computer tools to develop a preferred CAP delivery location and elevation economically advantageous to water rate payers. This paper discusses the various factors associated with Tucson's projected need for CAP water storage including reliability, operational flexibility, water quality, shortage, and power management. Each of these factors will affect the degree to which the water utility can successfully assimilate Central Arizona Project water into its groundwater supply system. Although a decision regarding storage location and volume has been postponed for the present, the initial years of CAP usage by the City of Tucson will provide sufficient test to justify the decision for no storage or prove its necessity.