High Quality Content by WIKIPEDIA articles! The Central Arizona Project (CAP) is a 336 mi (541 km) diversion canal in Arizona in the United States. The aqueduct diverts water from the Colorado River from Lake Havasu City near Parker into central and southern Arizona. The CAP is the largest and most expensive aqueduct system ever constructed in the United States. CAP is managed and operated by the Central Arizona Water Conservation District (CAWCD).