The Colorado River appears tiny beside the vast Grand Canyon, yet its racing, muddy waters carved the canyon’s one-mile depth. Although it can seem distant from the canyon’s edge, people across the desert Southwest are closely tied to it, and today cities and farms consume the river before it reaches the sea. A bridge spanning 440 feet carries hikers and mules 70 feet above the river to nearby Phantom Ranch. Since 1963, Lake Powell has backed up behind Glen Canyon Dam just upstream of Grand Canyon, and although the dam holds back the river’s canyon-carving power, 128,040 gallons per second still surge through the Inner Gorge during normal operations, enough to fill an Olympic-size pool in only five seconds.