Future growth may be curtailed as someone who plans on retiring to a sunny spot with a huge lawn, a pool, an outdoor mister, and 30 golf courses nearby may choose to stay in Ohio or go to Myrtle Beach or wherever instead, but, no, people won't leave the SW any time soon because of a lack of water...there's just way too much that can be done to cut back on water usage to feed municipal/residential demand. In drier cities like Albuquerque, people undertake efficiency measures voluntarily, but in higher consumption cities like Vegas and Fresno and Phoenix, it'll require more tough choices. For one thing, Vegas has virtually no parks or green spaces, so golf courses and lawns are the only respite from concrete and dust and they'll willingly pay much higher water rates to keep their level of consumption/lifestyle. The megaresorts are xeriscaping quite a bit, if only for public relations purposes, especially since they're frequently seen as a scapegoat for rampant water usage when they really don't use that much. Millions of square feet of grass have been removed in Vegas in recent years, saving billions of gallons of water per year.