Central Arizona Project – Part 1

Arizona_cap_canalToday, we will begin a three-part series highlighting the largest aqueduct system in the United States, the Central Arizona Project. This project was created by the Colorado River Basin Project Act of 1968, signed by President Lyndon B. Johnson on September 30, 1968.


The Central Arizona Project (CAP) is a 336-mile diversion canal designed to deliver 1.5 million acre-feet (488,473,200,000 gallons) annually. The CAP is currently the largest non-groundwater source of water for southern and central Arizona, making up an average of 32% of the distribution area’s total water supply.  This aqueduct is managed and operated by the Central Arizona Water Conservation District (CAWCD). The aqueduct diverts water from the Colorado River at Lake Havasu City near Parker, delivering water to over a 1,000,000 acre area of south and central Arizona, including Maricopa County, Pinal County and Pima County, and the metropolitan communities of Phoenix and Tuscan. When the project was initially approved, it included authorization for the development of facilities to deliver water to Catron, Hidalgo, and Grant counties in New Mexico. As of today, these facilities have not been constructed because of cost considerations, a lack of demand for the water, lack of repayment capability by the users, and environmental constraints. In addition to central-arizona-project_canal_graphicits water supply benefits, the project also provides substantial benefits, from flood control and outdoor recreation, to fish and wildlife conservation, and sediment control.


The CAP is the largest and most expensive aqueduct system ever constructed in the United States, and the time spent in actual construction ran from 1973 until 1993, when the major portions of the project were declared “substantially complete.” There are still distribution stations awaiting construction; it is estimated that full development of these systems could require another 10 to 20 years. Next week, we’ll take a look at the construction of the CAP, including some of the subsequent dams that proved necessary during the construction process.