"When it Stops Snowing in the Rockies,Then there will be a Major Problem,The Rockies feed The Colorado River,Of which feed Las Vegas/Los Angeles/Arizona/etc."

It isn't just the water, it's the delivery system that could be a major issue.

Sue

Some time in the future you may be able to ante into a poker game in Las Vegas with water.

There was a movie, a B-grade film, but entertaining enough, "Ice Pirates". The protagonist, trying to obtain something on the black market, gets asked by the supplier, making the move usually applied to money, 'Do you have any water'.

I also liked that people didn't do much of the fighting. They left it to the robots. Who went at the other sides robots with an axe.

Who knows what Las Vegas might do if water got tight? Probably something grand and over-the-top. Perhaps a huge dome over the city to catch evaporated water. Maybe a huge water-from-air system run by a nuclear plant or a huge solar bank. They do have a lot of room for solar collectors.

Perhaps, poetic in its extraction of utility from discards, like Las Vegas itself blooming in the barren desert, It might sell itself for high-level nuclear waste storage and then use the waste heat created to run a desalination or water-from-air plant.

"It might sell itself for high-level nuclear waste storage..."

100 miles north of Vegas, they already do store nuclear waste, it's called Yucca Mountain. It's delivered from all over the country, from the states that think nuclear reactors are great, but don't want the waste in their own backyard (sneer).
http://www.yuccamountain.org/

There used to be a joke in LV about how they could merge the components of Yucca Mountain and Las Vegas, with everything glowing without the use of neon lights. And maybe the people, too.

Sue

The idea was that Yucca Mountain would be the main US storage facility. That it would allow the closure of several thousand smaller storage sites. Didn't work out that way.

As far as I can tell the only nuclear waste present is the stuff they used for proof-of-concept engineering studies. The US spent many millions testing, engineering, and building the site and it looks like it will never be used as intended.