If we generously assume someone needs 2 liters of water/day to survive, then only 3% of California's water production is needed for its population to not die of thirst. A market system could easily be set up where this tiny sliver of water is reserved for this purpose, avoiding the scenario where those dastardly rich twirl their mustaches and cackle while the poor wither.
In the late 19th century rich people in LA bought many properties upstream of Owens valley, on the Owen’s river, and diverted the water to LA leaving farmers in Owens valley without the water they historically had and needed for their farms.
The idea that the only market is a robber-baron friendly totally unregulated one is an absurd strawman.
The water issues in California could be addressed by trading (say) half the water currently going to agriculture. Everyone would be better off, including those poor you pretend to care about.