Background: the
California Water Wars were a dispute in the first decade of the 20th century between the city of Los Angeles and the people of the Owens Valley in eastern California. LA mayor Frederick Eaton and William Mulholland, head of the LA Department of Water and Power, saw in the Owens Valley a bountiful source of fresh water to fuel the city's growth into the 20th century. The problem was that there were already a lot of people living in the Owens Valley, and they needed that water too. Moreover, the federal Bureau of Reclamation wanted to build an irrigation system in the valley to help the farmers and ranchers there. The city of Los Angeles used a ton of shady tricks to secure the water of the valley and block the Bureau of Reclamation's plans, including understating the water supplies that LA already had access to, and Mayor Eaton posing as a rancher and buying up land in the valley.
At the end of the day, the Bureau of Reclamation's irrigation plans were permanently shelved, Los Angeles built its aqueduct and became a world-class metropolis, and so much water was diverted south that the Owens Valley dried up by 1930, killing the region's agriculture-dependent economy.
But what if it had gone differently? What if LA's plans were blocked, by either the Bureau of Reclamation or by the local community? What would LA and the Owens Valley look like in the present day? Could LA have turned to some other source for water? (In OTL, Mulholland had plans to divert water from the Colorado River, but was blocked from doing so; imagine the can of worms that would've opened with Mexico.) If LA doesn't find an alternative source of water, does another West Coast city (San Francisco, San Diego, Seattle) rise in importance?