The Coastal Branch diverts about per year from the California Aqueduct to parts of San Luis Obispo and Santa Barbara counties. The aqueduct stretches for , and is mostly made up of buried pipeline. Pumping plants at Las Perillas, Badger Hill, Devil's Den, Bluestone, and Polonio Pass serve to lift the water over the California Coast Ranges. Once over the crest of the mountains, the water is reregulated in a series of small reservoirs numbered Tanks 1 through 5. The Coastal Branch was completed in 1994 following a severe drought that led to calls for importation of SWP water.