The Origins and Implications of the 100-Year Water Rule

Arizona's 100-year water rule requires housing developers to demonstrate access to a reliable water supply for a century before new developments can proceed. This rule, established in the state's 1980 water law, was largely a response to concerns over groundwater depletion and aims to ensure sustainable water management. Originally viewed as an arbitrary yet suitable benchmark, the rule gained significance when housing developments in Phoenix faced delays due to re-examination of water supply claims. Kathy Ferris, one of the law's authors, explained that these efforts were largely driven by city officials in conjunction with farmers, who recognized the need for a regulated water supply to support both agriculture and community growth.