Important food for thought. How people in arid regions landscape and garden is also important. Water management includes practices you point out, as well as replacing water-hungry lawns, capturing household "gray water" for use in toilet tanks or in the garden, capturing precipitation from rooftops into rain barrels, sculpting landscape swales to direct water in the landscape and slow down runoff, selecting plantings for drought tolerance, and mulching effectively to help soil retain water longer.

There is a terrific documentary to check out called "Re-Greening the Desert," with John D. Liu.

All of he "solutions" create new ecological problems somewhere. The problem is simply too many people populating the landscape, overusing limited resources.