(This isn’t exactly tech, but it is technical.)
I have long had a bad feeling about building cities in places not environmentally equipped to support them. On one hand, it does make the desert bloom. On the other hand, blooms eventually fade.
Scientific Blogging has a great post on the growth and ecology of Las Vegas as regards the water supply, the water table, irrigation, and Lake Mead, including some fascinating aerial photographs and diagrams.
Read it here.
When you build a society in the desert the water issue will be a burning hot one. Where do the citizens get their water from? There are basically two options, and rain is not one of them. Even below deserts groundwater can be found. Check for that. And you can collect water from damming natural waterways . . . .
Water is a finite resource. The amount of water in the world is constant, barring some kind of cataclysm.
The amount of water in the world is what it is.
(Post title with apologies to Samuel Coleridge.)