The Southwest location of Phoenix, Arizona, makes it a very flat, very hot and dry locality without a major natural water source of its own. For that reason, Phoenix has come to depend more and more heavily upon external sources for its water. In 1934, the Parker Dam, with its reservoir Lake Havasu, and the Colorado Aqueduct Project was initiated. Under the Arizona Project Aqueducts program, the Colorado Aqueduct sends water to Southern California and to Central and Southern Arizona. As a result, Phoenix, Arizona, gets 36 percent of its water from the Colorado River, which, experts have warned, is heading for a drought and a dry-out. Thus the question of where water comes from in the Southwest, from Los Angeles to San Diego to Phoenix--these naturally semi-arid desert or full desert areas--is a vitally critical one.
The next largest percent of Phoenix's water comes from Salt River, originating east of Phoenix and north of Mesa, at the output of 54 percent. Additional water for Phoenix comes from groundwater at 3 percent. Phoenix has intentionally been building up its groundwater by minimizing the drain upon it by implementing mandatory city-wide water conservation measures in order to act with foresight in the shadow of the drying up of the Colorado River.