The Colorado River Through Grand Canyon: Natural History and Human Change

Once Glen Canyon Dam was completed in 1963, the Colorado River in its passage through the Grand Canyon would never be the same. Now sealed off at both ends, the Colorado has been transformed into a carefully-tended aquarium, its flow of water controlled and monitored. The effect on the Canyon's physical and biological systems has been extraordinary.Steven Carothers and Bryan Brown—both veteran river runners and scientists—draw on river history and ecological studies to demonstrate how Canyon life has adjusted to these sweeping environmental alterations. For example, they show how increased growth of algae in the now siltless waters have altered fish populations, and how changes in vegetation have encouraged the return of beavers. Insects, birds, reptiles—all have been affected as the Canyon's ecosystem has been redefined by changes in the river's content, temperature, and flow.Recreational use of the Canyon has been altered as well. For the thousands of people who raft down the river each year, the dam has brought the need to account for diurnal rather than seasonal alterations in water flow, as well as the likelihood that changes in debris flow will make rapids increasingly difficult to run. The trapping of silt behind the dam also means that river beaches now wash away without being restored from upstream.The authors warn that these changes may disappoint those who expect the Colorado to represent an untouched wilderness river; yet the new Colorado remains a source of inspiration for all who visit it. In that spirit, they propose a new vision for ecosystem management in the Canyon that would strike a balance between environmental needs, water storage, and hydroelectric power generation, so that "by understanding these recent changes in the river, perhaps we will be able to shape the river of the future for the better."