The population of Las Vegas has grown a lot since 1983 and the city uses a lot more water now, plus the population getting water from the Colorado River has grown. Then, there is the drought. Plus, they use the water to generate electricity.
One idea, is to use wind and solar for electricity, so that less water is needed to generate electricity.
There is also the idea of aquaducts, and piping water, etc. I would have to look at a map to get ideas, and I would have to know where all of the water sources are.
And of course new dams can be built in certain areas, and new lakes can be made, etc.
Salute,
Tony V.