Las Vegas is allocated a mere 1.8% of Colorado River water, yet is so successful at conservation and reuse it currently is using only 75% of that. So, it’s sending Southern California 150,000 acre feet of water. This isn’t a transfer, it’s more like a loan. At some point in the future, Vegas will ask for the water back, which means it can use more water in Lake Mead and Southern California will get less.
The water will help the Metropolitan Water District of Southern California make up for shortfalls in its supplies from Northern California, where drought has dramatically reduced the amount of water available for shipment through California’s State Water Project. Met is basically desperate, and Las Vegas has been so successful at water conservation that it is only using 75 percent of its Colorado River allocation these days.
Las Vegas has a huge system of flood basins, Rain water is trapped, cleaned up, then pumped into Lake Mead to be re-used. Ditto for all indoor water including that from bathrooms. Vegas has been toilet-to-tap for years.