The San Diego Aqueduct, or San Diego Project, is a system of four aqueducts in the U.S. state of California, supplying about 70 percent of the water supply for the city of San Diego. The system comprises the First and Second San Diego Aqueducts, carrying water from the Colorado River west to reservoirs on the outskirts of San Diego. The 70-mile (110 km) First Aqueduct consists of the pipelines 1 and 2, which run from the Colorado River Aqueduct near San Jacinto, California, to the San Vicente Reservoir, approximately 15 miles (24 km) northeast of the city. Pipelines 3 and 4 make up the 94-mile (151 km) Second Aqueduct. Together, these four pipelines have a capacity of 826 cubic feet per second (23.4 m3/s). The smaller, 12.5-mile (20.1 km) Fallbrook-Ocean Branch branches from the First Aqueduct into Murray Reservoir. The La Mesa-Sweetwater Branch originates from the First Aqueduct, flowing into the Sweetwater Reservoir.

The Colorado River Aqueduct, or CRA, is a 242 mi (389 km) water conveyance in Southern California in the United States, operated by the Metropolitan Water District of Southern California (MWD). The aqueduct impounds water from the Colorado River at Lake Havasu on the California-Arizona border, west across the Mojave and Colorado deserts to the east side of the Santa Ana Mountains. It is one of the primary sources of drinking water for Southern California.