Phoenix is possible as a major metropolis by the cheap water supplied by the Colorado River. There is a small river that runs through Phoenix, and was the reason for it being established initially, but it was with the engineering from the Hoover Dam that the whole US South West became a viable human urban habitat.

Golf course in Mesa, AZ

Many of the private and public areas are saturated with water; such as golf courses and parks. Water being cheap means that automated irrigation is possible. It is in direct contrast to the Phoenix climate which stays above 40C (103F) often for weeks and months at a time during summer. It is enough to wilt the toughest grasses.

The irony is that these green places are not well patronised. The rough city-hikes with its truer desert landscapes are for more popular. While water is cheap it is still a significant expense, not to mention maintenance upkeep, to maintain a green lawn in Phoenix. Consequently the great majority of houses have a yard which is a mix of rocks and succulents (cactus).

People do put trees and bushes in their yards but they are natives that can handle the harsh environment without undue care or watering. A common adage is that if a tree needs watering when it is mature then it is not worth having in the landscape.

Consequently the trees and bushes are a mix of natives and imports from other water scarce environments such as Australian and South America. The mighty old Eucalypt is a common landscaping tree in the older parts of Mesa and Scottsdale. The newer landscaping style is to mimic the local desert environment which produces stunning suburbans environments in my opinion.

The other problem with automated watering is evaporation. Most sprinkler systems are hopelessly inefficient and leave puddles of water on the concrete, road or gutter. Correct pricing for water would solve this, but then again a market price for water would probably make Phoenix economically uninhabitable.

Evaporating water on park footpath in Mesa, AZ

The green grass style of corporate landscaping is less and less common, mainly being in the older areas of Phoenix such as Mesa. Arguably there has been a rationality change in the last fifty years in South-Western cities like Phoenix where dominance of nature has moved toward attempts at living within the environment. There are limitations though, our urban centers are reliant on cheap energy, water and transportation. I don't see that changing.