<P> The Colorado River originates more than 1,000 miles (1,600 km) from California in the Rocky Mountains of Colorado and Wyoming and forms the state's southeastern border in the Mojave Desert . Unlike the other California watersheds, essentially all of the water flowing in the Colorado originates outside the state . The Colorado is a critical source of irrigation and urban water for southern California, providing between 55 and 65 percent of the total supply . </P> <P> The Central and South Coast watersheds include the most populous regions of California--the San Francisco Bay Area, Los Angeles and San Diego--but have relatively little natural runoff, requiring the importation of water from other parts of the state . </P> <P> Rivers of the Lahontan watersheds in eastern California are part of the high desert Great Basin and do not drain to the Pacific . Most of the water is used locally in eastern California and western Nevada for irrigation . The Owens River of the South Lahontan region, however, is a principal source of water for Los Angeles . </P> <Table> <Tr> <Th_colspan="3"> Main California watersheds </Th> </Tr> <Tr> <Th> Hydrologic region </Th> <Th> Annual precipitation </Th> <Th> Annual runoff </Th> </Tr> <Tr> <Td> North Coast </Td> <Td> 55,900,000 acre feet (69.0 km) </Td> <Td> 28,900,000 acre feet (35.6 km) </Td> </Tr> <Tr> <Td> Sacramento River </Td> <Td> 52,400,000 acre feet (64.6 km) </Td> <Td> 22,400,000 acre feet (27.6 km) </Td> </Tr> <Tr> <Td> North Lahontan </Td> <Td> 6,000,000 acre feet (7.4 km) </Td> <Td> 1,900,000 acre feet (2.3 km) </Td> </Tr> <Tr> <Td> San Francisco Bay </Td> <Td> 5,500,000 acre feet (6.8 km) </Td> <Td> 1,200,000 acre feet (1.5 km) </Td> </Tr> <Tr> <Td> San Joaquin River </Td> <Td> 21,800,000 acre feet (26.9 km) </Td> <Td> 7,900,000 acre feet (9.7 km) </Td> </Tr> <Tr> <Td> Central Coast </Td> <Td> 12,300,000 acre feet (15.2 km) </Td> <Td> 2,500,000 acre feet (3.1 km) </Td> </Tr> <Tr> <Td> Tulare Lake </Td> <Td> 13,900,000 acre feet (17.1 km) </Td> <Td> 3,300,000 acre feet (4.1 km) </Td> </Tr> <Tr> <Td> South Lahontan </Td> <Td> 9,300,000 acre feet (11.5 km) </Td> <Td> 1,300,000 acre feet (1.6 km) </Td> </Tr> <Tr> <Td> South Coast </Td> <Td> 10,800,000 acre feet (13.3 km) </Td> <Td> 1,200,000 acre feet (1.5 km) </Td> </Tr> <Tr> <Td> Colorado River </Td> <Td> 4,300,000 acre feet (5.3 km) </Td> <Td> 200,000 acre feet (0.25 km) </Td> </Tr> </Table>

Where does los angeles get its water supply