LA is the classic example for that.
Of course, any idiot who would try to build a metropolitan area of over 15 million in the middle of a desert deserves it. The sad thing is, the LA area used to be absolutely wonderful for agriculture, since it has better local supplies of fresh water than the Imperial Valley does, along with being closer to supply routes. After all, for the longest time, Pasadena was actually larger than LA itself. LA gets its water from a number of sources. The main external sources are the Colorado River, especially from the Parker and Davis dams, the Owens Valley, Mono Lake, and the Sacramento River Delta.