Chapter 7 - Large Rivers of the West

Abstract

Several large rivers have headwaters in the western United States, including the Columbia, Colorado, Missouri, Yellowstone, Snake, Arkansas, and Rio Grande rivers. This chapter emphasizes the Colorado and Columbia rivers, both well studied and important rivers. Physically, they are similar in length and drainage area. But the mean annual discharge of the Columbia, at 7960 m3/s, is more than 10 times greater than that of the Colorado, at 640 m3/s. The ecological history of these two rivers can be summed up in a single word—abuse. This abuse largely has been due to the construction of large hydroelectric and storage dams to produce cheap and abundant electrical energy, to supply irrigation water to crops throughout the western United States, and to control floods. The Corps of Engineers and Bureau of Reclamation have held fast to their philosophy that every drop of water that flows to the sea unused is wasted. Fortunately, as public awareness of the ecological harm caused by dams began to grow, the missions of both the Corps and the Bureau evolved from dam-building to other pursuits, including recreation. All in all, the Colorado and Columbia rivers represent severely impacted riverine ecosystems. The Upper Basin of the Colorado remains fairly typical of pristine streams of this region; however, the Colorado River in the Lower Basin and the entire Columbia River within the continental United States are mere ghosts of their former ecosystems. These significant and largely irreversible impacts were initiated during a time when there was little appreciation for the value of unperturbed wilderness or pristine environments.