One difference between Cataract Canyon and the Grand Canyon is that the water is typically quite a bit warmer in Cataract. That is because the start of the Grand Canyon (Lees Ferry) is just 15 river miles below Glen Canyon Dam, where ice cold water comes out of the bottom of Lake Powell. With Cataract Canyon, the closest large dam upriver is Flaming Gorge on the Green, a couple hundred miles upriver. And on the Colorado above the confluence, there are no major dams at all (there are smaller dams on some tributaries such as the Gunnison and the Blue).