One day last spring, water pressure in pipelines suddenly crashed In the Antelope Valley, setting off alarms. Demand had inexplicably spiked, swelling to three and half times normal. Water mains broke open, and storage tanks were drawn down to dangerous levels.

The emergency was so dire in the water-stressed desert area of Hi Vista, between Los Angeles and Mojave, that county health officials considered ordering residents to boil their tap water before drinking it.