The Phoenix area is the fifth largest in the United States 4.8 million - and it is understandable why - it has an enviable lifestyle and climate. Except it is a crazy place for so many people to make their home - there is just not enough water. A city with the population of New Zealand but with a bare fraction of the water resources.

Phoenix ostensibly has a good secure water supply - most comes from the melting snow pack from the mountains to the north and east of the city. The seasonal water is stored in large reservoirs. Together, the Salt River and Verde River—through a network of canals, wells, dams, and lakes known as The Salt River Project—provide Metro Phoenix with one of its primary water sources. The city and its outlying towns use groundwater—water naturally settled into subterranean aquifers—as a second vital source. The third and final primary water source comes through the pumps and aqueducts of the Central Arizona Project, some 190 miles from the body of water that gives Arizona its squiggled western border: the Colorado River.

But in reality the future is not looking rosy as this article highlights.

There is a limited and shrinking supply, growing demand, and a long-run picture that looks, from many angles, hopelessly apocalyptic. Inside the elaborate, diverse, and ever-evolving effort to manage water in what some have called “America’s least sustainable city.”

Water conservation is key. We've touched on Water up-cycling and micro-grids using small in-situ water reclamation and processing. And how this might be applied to cities with threatened water supplies - but surely the focus should be on ensuring people live in places that have sustainable water supplies in the first place. Mass desalination may one day allow us to live anywhere.

The entire article is well worth reading, it is specific to Phoenix, but many of the implications of growth and the need to revisit the business as usual approach to how we sustain out cities becomes obvious.