Really? The West isn't having any issues with fresh water supply?
Las Vegas Tries to Prevent a Water Shortage - Popular Mechanics
So... you're quoting the inability for people to live in a manufactured entertainment city in the middle of the desert as evidence of the "overpopulation" problem?
Las Vegas exists because of technology, ingenuity and money. If the casinos pulled out or died tomorrow, that city would be a ghost town in short order.