A man in Arizona sees a glimpse of a potentially frightening future. A future where the planet is hotter, the soil is drier, and our most precious resource is evaporating. His job is delivering water. And his job is getting harder. John Hornewer is now having to drive hours farther each day to fill his truck, which, in turn, fills the subterranean tanks at homes in an area outside Phoenix. His normal supplier cut him off; more precisely, on Jan. 1, the city of Scottsdale, Ariz., cut off transfers to the exurban community he serves in a desire to conserve water for its own residents. He found new suppliers, farther away. Then another supplier cut him off.