From a secure, windowless room in northern Phoenix, technicians control the Colorado River water that sustains America’s largest desert metropolis. The vast canal system the team oversees has for four decades conveyed an increasingly scarce commodity across 330 miles of rugged terrain to slake blossoming subdivisions, sprawling farmland and, in recent years, a powerhouse semiconductor industry. It supercharged Arizona’s economy and transformed Phoenix into one of the nation’s fastest-growing cities.

But this lifeline, known as the Central Arizona Project, came with a catch. In exchange for billions of federal dollars to build it, the state agreed to lower-priority water rights, putting the aqueduct among the first in line for cuts in a time of deep drought. Now that time has come.

With the seven states that rely on the Colorado River deadlocked over how to split its diminishing supply, the Trump administration is pushing its own plan to divide the water. The three downriver states — Arizona, California and Nevada — would most likely shoulder the most pain, but no single user stands to lose more than the Central Arizona Project. Short-term reductions, announced by the federal government on Friday, will cost Arizona roughly one-third of its share of river water over the next two years.

Under the most severe outcome, the system would be cut off entirely during the driest years, setting off a social and economic meltdown Arizonans shudder to even imagine.