The Phoenix lifeline running dry

An aerial view of the Central Arizona Project canal winding through Mesa, Arizona. — Rebecca Noble/The New York Times

FROM a secure, windowless room in northern Phoenix, technicians control the Colorado River water that sustains the United States’ largest desert metropolis.

The vast canal system the team oversees has for four decades conveyed an increasingly scarce commodity across 530km of rugged terrain to slake blossoming subdivisions, sprawling farmland and, in recent years, a powerhouse semiconductor industry.