Water rights are going to be a hot topic. There just isn't enough for everyone, and sharing a commons is not something that America (and other western societies) has been good at.
There's enough for everyone, but some large actors are taking most of the water and wasting it or exporting the productive value of that water due to a lack of real market forces on the price of water.
You're absolutely correct there will be water rights issues, I would argue they will become wars in certain places and in others it will result in certain massive cities becoming dead over several decades.