Under the searing desert sun, Max Wilson watched water flow through a canal in north Phoenix. This unassuming strip of blue next to a busy road is the city’s lifeline to the Colorado River. Soon, there will be less water in it.

Wilson, who is the water resources management advisor for the City of Phoenix, has to make sure cuts to this canal’s supply don’t cause taps to go dry for more than 1.7 million people who depend on his system.