In the early 20th century, Arizona's leaders knew the state's future depended on a water supply that was secure, stable and renewable. They pursued that vision; the result was Central Arizona Project (CAP), a 336-mile system that brings Colorado River water to central and southern Arizona, delivers the state's single largest renewable water supply and serves 80% of the state's population.
In the early 1900s, the seven states that share the Colorado River Basin - Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming - negotiated for shares of its water. Ultimately, the states were divided into the Upper Basin and Lower Basin and each basin was allocated 7.5 million acre-feet (MAF) of water. Arizona, Nevada and California comprise the Lower Basin and receive 2.8 MAF, 300,000 AF and 4.4 MAF respectively. The 1944 U.S.-Mexico Water Treaty provides 1.5 MAF of Colorado River water to be delivered to Mexico annually. One acre-foot equates to a yearly supply for three Arizona families.
