DeHoff started seeing changes in Cataract Canyon in 2002—about when the region’s drought started. Lower water levels led rapids to form. Cottonwoods and seep willows sprouted in areas that were once underwater. As Lake Powell shrunk, the river cut through the layers of sediment left behind—dams halt the flow of rivers and stop sediment from moving freely. Yet, despite these rapid changes, DeHoff saw little scientific research or public attention focused on this section of the river. Instead, he says, efforts went downstream to the Grand Canyon, on the other side of the lake.