Yep, Owens valley is basically an environmental disaster created by LA. So in the grand scheme of things, buying water from NorCal is better than stealing from the Owens valley through antiquated water rights.
But really, California (and really the entire Western US) needs a water rights governance overhaul. Right now the focus is all on urban water use, which is practically negligible compared to the agricultural water rights usage.
Much easier to tell Joe homeowner he's not allowed to have a lawn than to close down the country club. Where would the rich relax then?
That's a money play too. Some of the best farmland in the world is now the endless subarban Boston->DC corridor.
We created the miracle on the desert, and billions were made in real estate.