The Colorado River Aqueduct, or CRA, is a 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. Originally conceived by William Mulholland and designed by Chief Engineer Frank E. Weymouth of the MWD, it was the largest public works project in southern California during the Great Depression. The project employed 30,000 people over an eight-year period and as many as 10,000 at one time. The system is composed of two reservoirs, five pumping stations, of canals, of tunnels, and of buried conduit and siphons. Average annual throughput is . Route The Colorado River Aqueduct begins near Parker Dam on the Colorado River. There, the water is pumped up the Whipple Mountains where the water emerges and begins flowing through of siphons and open canals on the southern Mojave Desert. At Iron Mountain, the water is again lifted, . The aqueduct then turns southwest towards the Eagle Mountains. There the water is lifted two more times, first by to an elevation of more than , then by to an elevation of above sea level. The CRA then runs through the deserts of the Coachella Valley and through the San Gorgonio Pass. Near Cabazon, the aqueduct begins to run underground until it enters the San Jacinto Tunnel at the base of the San Jacinto Mountains. On the other side of the mountains the aqueduct continues to run underground until it reaches the terminus at Lake Mathews. From there, of distribution lines, along with eight more tunnels, delivers water to member cities. Some of the water is siphoned off in San Jacinto via the San Diego canal, part of the San Diego Aqueduct that delivers water to San Diego County. Background and construction As the Los Angeles metropolitan area grew in the early 1900s, Mulholland and others began looking for new sources of water. Eventually, Los Angeles laid claim to the waters of the Owens Valley, east of the Sierra Nevada, and in 1913 completed the Los Angeles Aqueduct to deliver its waters to the burgeoning city. By the early 1920s, Los Angeles had grown so rapidly that the