by Whit Gibbons

October 30, 2005

Last week I visited one of the unchallenged seven natural wonders of the world-the Grand Canyon. Standing on the cliff edge and looking at the Bright Angel Trail below was breathtaking the first time I saw it a half century ago. It still is. The panorama of red, yellow, and brown rocks forming the ten-mile-wide gorge is as awesome as ever. From one vantage point you can see a short stretch of the Colorado River, literally a mile below, the source of the millions of years of erosion that formed the canyon.

The next day I attended a conference in Phoenix listening to scientists, government officials, power company executives, conservation groups, recreational tour companies, and others discuss and debate the best uses of the river and the canyon. From the perspective of an easterner, or for that matter almost anyone who is not directly involved, deciding how to "manage" such an ecosystem might seem like an ideal example of a nonproblem. Why would a 1,400-mile-long river passing through a canyon with exposed Precambrian rocks more than two billion years old need any help managing itself?

As with all natural systems today, adding people to the equation has caused the dilemma. The Colorado River provides water for millions of people from Wyoming to southern California. Two dams generate hydroelectric power, serving communities living over thousands of square miles. Anglers fish along hundreds of miles of river, while water enthusiasts take rafting tours through rocks and rapids. Along with bird-watchers and hikers, they camp along the river. The general public simply enjoys the views and wildlife, and most want the canyon ecosystem to be as natural as possible.

Major economic and environmental impacts to the Colorado River include one above and one below Grand Canyon National Park. Hoover Dam was completed in 1935 to form Lake Mead along the southern Arizona and Nevada border. The 1963 construction of Glen Canyon Dam in northern Arizona created Lake Powell. At this point no one is going to be 100 percent satisfied with the handling of the Colorado River ecosystem. The Glen Canyon Dam Adaptive Management Program may come closest to a plan that might work.

Adaptive management is a process designed to deal with the disparate opinions of how to manage an ecosystem. In this case, the power generated by the Glen Canyon hydroelectric dam depends on regulating the amount of water released from the reservoir, which changes downstream flow rates and water levels. The basic idea of adaptive management is for scientists to conduct research to determine how dam operations are affecting the river environment and its use by people. Subsequently, science-based decisions can be made to modify future operations.

During the conference one report noted that the use of campsites and sandbars for recreational purposes has declined since dam construction, presumably because of reduced river flows and loss of sand deposits downstream. A 2004 test of a high flow release demonstrated that beaches and sandbars were rebuilt. One response in the adaptive management process would be to modify flow rates in a manner that would assure occasional high flow releases to reestablish river sandbars and encourage recreational camping.

Meanwhile, conflicting situations arise. Commercial power interests would prefer to adjust river flows daily to achieve the most economically efficient rates and would not view excessively high flows as economically practical. Also the river would not be navigable for recreational rafting during high flows. On the other hand, some native fish populations, including the endangered humpback chub, have declined since dam construction. Some ecologists believe that creating the more natural situation of occasional high flows might benefit the chub and other fishes. Such flows would also reduce the number of rainbow and brown trout, neither of which is native to the Colorado River. Trout eat native fish, so are unpopular with some naturalists. But nonnative trout also support a sports fishing industry, making them very popular with anglers.

Adaptive management may become the only viable approach for ecosystems whose management affects many people and many kinds of activity. The Everglades, Great Lakes, and certain coastal areas come to mind. The forthcoming environmental and economic deliberations about the Glen Canyon Dam will be instructive.

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