There is a lot of water in Scottsdale, even though the Phoenix metro area is the desert, with only 7 inches (18 cm) of rain per year. Perhaps people like the lakes and ponds to give the impression that we are not in the desert. Developers like to add lakes and ponds because they can charge more for the houses they build around them.
Under the initiative of former Governor Bruce Babbitt, who later ran for President and served as U.S. Secretary of the Interior under President Clinton, since the 1980's it has been illegal for developers or cities to use ground water from wells for lakes and ponds. It is obviously wasteful to pump water from the aquifer for decorative features.
We have photos of the stark landscape of the Atacama Desert of northern Chile this week on our Viva la Voyage travel photo site.