I don’t think climate change had anything to do with build a multi-million-person city in a high desert. Phoenix will soon be facing a similar problem. The Colorado River never had the flow to supply all the people that live in its watershed. It’s why they call them deserts folks.
Vegas has already found the solution they will never be out of water they recycle every drop that hits a drain. Outlaw lawns, most water use in a household is not consumptive it’s washing laundry, dishes, showers and flushing the toilet. The amount of water a human drinks and then loses to evaporation is small in fact most of the water a human needs comes from the food we eat half of our water loss per day is from the food we eat as our bodies burn it into CO2 and water via the ATP cycle. By recycling all those in home water you get 95% back into the water supply only 5% or less is lost via human evap or laundry dryer losses. Vegas is the world leader in recycling Israel is right behind it by percentage. Vegas gets 300,000 acrefeet per year they use less and return to lake mead 200,000+ acre feet per year building up a reserve in excess to their 300,000 allotment. Ten years running now they a have put back more every year than they were allowed to take so they have banked over a million acre feet on lake mead for future use. NV as a state gets to keep every drop they add to lake mead from the Las Vegas wash and the Virgin River per the Supreme Court. They add more in every year due to rain fall in the basins as well. 4” per year added up when it’s hundreds of sq miles of area. The recent floods in Vegas show that in soades.