L.A. has been stealing, buying, paying for water canals and piping water from all over CA since the turn of the century. The first stolen bought water is from the Owens valley on the east side of the Seirra Mountains, it is piped and uses gravity fed water in canals to get to L.A. The next one is the All American canal from the south east corner of CA along the Colorado river and is routed from their through the Imperial and Coachella valleys and pump it into L.A. from the bottom of the White Water grade.
Their are another one or two canals from the Colardo river, one form the Parker Dam ,Lake Havazu, feeding that water into L.A.
The last water piping project taking water form the Sacramento central CA area is the Feather river project that was built in the late 1960s and finish in the early 1970.
Some of the wiser cities along the coast like Santa Barbera and several others further north on the coast have built and are using water desalination plants to reclaim and use ocean water
The immigration, legal and illegal, of all people into SO CA should have been stop years ago due to the water problems and other crisis like no more space for them