China has been doing what the grandparent suggests for 20 years now, building networks to transfer water from the south to the north, and even at full-tilt with cheap access to labor and the political will to displace (so far) hundreds of thousands of people, it's not nearly enough to solve their looming water crisis.

Regions like Arizona are just inimical to large-scale human habitation and agriculture. The good news is that Arizona is projected to get more humid thanks to climate change. The bad news is that Arizona isn't projected to get any less hot, so look forward to an increasing frequency of wet bulb events in the future.