That’s pretty neat. Too bad most of SoCal’s water is pumped in from halfway across the States, so even if they do keep their people, they’ll have a water shortage along with much if the Western US.
80% of water usage in CA is agricultural, and over a third of that is for water-intensive crops like nuts and alfalfa.
Add on top of that that half of all domestic water usage in CA is for watering lawns and it becomes obvious that multi-family housing is severely not the problem. Apartment-dwellers use drastically less water than single-family homeowners, but it all pales in comparison to the terrible land use decisions made by Central Valley farmers and enabled by the state.