Could floating solar panels on a reservoir help the Colorado River?

GILA RIVER INDIAN RESERVATION, Ariz.—About 33 miles south of Phoenix, Interstate 10 bisects a line of solar panels traversing the desert like an iridescent snake. The solar farm’s shape follows the path of a canal, with panels serving as awnings to shade the gently flowing water from the unforgiving heat and wind of the Sonoran Desert.

The panels began generating power last November for the Akimel O’otham and Pee Posh tribes—known together as the Gila River Indian Community, or GRIC—on their reservation in south-central Arizona...