The water levels behind the Colorado River’s biggest dams are fast-approaching or already at record lows, thanks to a 21-year megadrought that’s squeezing water supplies across the Southwest. But the effects of drought are likely to start showing up in energy bills, because those dams can’t produce as much electricity.
The problem is most acute at the Upper Colorado River basin’s largest reservoir: Lake Powell. At the base of Glen Canyon Dam in northern Arizona, the Colorado River flows out cold and clear. On the canyon walls, moss grows where water from behind the dam seeps slowly through the red sandstone. The air buzzes with electricity...