Shrug. Desalinization will cover the coasts. Agriculture will shut down when the aquifers finally fail.
Seriously though, I was gobsmacked when I found out there was such water-intensive agriculture being done in an area where they're dead proud of the scraggly cottonwood trees that manage to survive along creeks that go dry most summers. Where you have chihuahuas in your yard instead of squirrels because there's nowhere for the squirrels to live. Big fields of alfalfa supported by center pivots in the middle of rocky scrubland where even the cactus dry out some years. It's not sustainable and never has been and now people are sitting around scratching their heads like it's some kind of mystery what's happening.