Then Southern California is "desert" only in a most technical sense, and misleading. San Diego is downright tropical, not because of water shipped to it, but because of humidity and climate and more rain than in L.A., I'd wager. It might not be lush, but it would hardly be "desert" without a city there.
Vineyards and agriculture were pretty strong before shipped in water in Los Angeles and surrounding areas. Fountain Valley (in the heart of Orange County -- yes, "the O.C.") is called that because of underground springs that were there (still are), and a lot of produce was grown there before it became citified.
Consider it a "desert" if you want, but ... I've been to deserts. San Diego and L.A., even without the cities, sure looked like they must have been pretty nice and fruitful deserts!
gee, I wonder if the reason for it is good irrigation coming from other parts of the state.