The Colorada is WAY oversubscribed for withdrawls outside of its basin.
Deciding to live in a place without a reliable natural water supply is just fundamentally stupid. Sadly, the modern post industrial world, allows an encourages people to make insanely stupid decisions.
If California would ignore the envirowhackos (I know, not going to happen) and build some reservoirs to capture the water that falls on their own state, it would certainly help and perhaps alleviate the problem altogether. As with electric cars, they live in a fantasy world where they believe that they can have the benefits without the necessary trade offs. You want water?... Well then you have to live with construction of additional reservoirs.