Adán Pajuelo is harvesting carnations, deftly clipping stems as he hustles down the row, when he pauses to glance up the mountain toward the source of water for his field—a lake and the glacier that feeds it. His community is concerned about a local utility’s use of water from the lake, and about possible downstream pollution from a mining project planned nearby.

“The retreat of the glaciers is a huge concern for everyone. It makes us think that we won’t have water in the future,” says Pajuelo, who heads the local organization of water users in this Andean farming community. He says he fears the mine “will take away what water we have.”

The glaciers in Peru’s central Cordillera Blanca are shrinking steadily, leaving policymakers and water users along the Santa River to grapple with long-term implications that may include not just less water during the dry season, but also a greater concentration of pollutants as a consequence of lower water flow. And recent studies show that the dry-season water flow may be decreasing faster than previously believed, giving people less time to adapt.