Jeffrey D. Bennion and Dr. M. Brett Borup, Civil and Environmental Engineering

Introduction

The Glen Canyon Dam was completed by the Bureau of Reclamation in 1963 as the main feature of the Colorado River Storage Project. The purposes of the dam were to regulate the flow of the Colorado River, store water for consumptive use, provide for the reclamation of arid and semi-arid land, control floods, and generate hydroelectric power (U.S. Department of the Interior, 1995). Since the dam was completed prior to enactment of the National Environmental Act, no environmental impact statement was filed regarding its construction and operation. Many environmentalist groups, most recently the Sierra Club, have lobbied for the removal of the Glen Canyon Dam; they claim that the dam is destroying downstream wildlife habitat (Sierra, 1997). In response, the federal government, with the help of several private sources, has done extensive research on the environmental effects of the Glen Canyon Dam, and has proposed several alternatives for modifying dam operations in order to improve the survivability of affected species while continuing to maintain the dam’s productivity.

The focus of my research was changed slightly because there is very little data on the environmental affects of draining the dam. Additionally, there were few specifics regarding the economic affects of draining the dam. As a result, I have focused primarily on the affect of the dam on the original environment, the governments proposed compromise, and the basic economic concerns.

Effects of the Dam

Resources downstream from Glen Canyon Dam through Grand Canyon are interrelated, since virtually all of them are dependent on water and sediment. Historically, the Colorado River and its larger tributaries were characterized by heavy sediment loads, variable water temperatures, large seasonal flow fluctuations, extreme turbulence, and a wide range of dissolved solids concentrations. The dam has altered these characteristics. Before the dam, water temperature varied from 80 degrees Fahrenheit to near freezing. Now, water released from the dam averages 46 degrees Fahrenheit year round, and very little warming occurs downstream (U.S. Department of the Interior, 1995). Lake Powell also traps sediment that previously was transported downstream. Sediment occurs both above and below the water surface, and its transport and deposition are important considerations in many resources. Exposed and submerged sediment deposits throughout the Glen and Grand Canyons maintain backwater fish habitats which are essential for spawning, and support vegetation that provides food for fish and other wildlife. (Angrandi, et al., 1993).

The pre-dam aquatic system supported an array of native and non-native fish. Non-native carp and channel catfish have probably been present since the late 1800’s; by 1950, channel catfish comprised ninety percent of the fish captures. However, by 1968 (five years after the completion of the dam) trout dominated the new cold water system below the dam. Before the dam, eight native and several non-native fish inhabited the river. Today, three native species are no longer in the system, two others are listed as endangered, and another is a candidate for listing under the Endangered Species Act. Non-native carp and channel catfish have also declined. The reasons for the declines may actually be quite complex, but a principle factor is the habitat changes brought about by the construction and operation of Glen Canyon Dam. Because of cold water temperatures, suitable  habitats for young fish are confined to tributaries, tributary mouths, and backwaters (Carothers and Brown, 1991).

The Government’s Solution

The government’s preferred alternative is called modified low fluctuating flow. This involves reducing maximum flows, increasing minimum flows, reducing daily flow fluctuations, and providing habitat maintenance flow. The goal is to protect and enhance downstream resources while allowing some flexibility for power operations. This alternative would have the same annual and monthly operating plan as the current plan (i.e. the same amount of water would be released, and ideally, the same amount of power would be generated), but would restrict daily and hourly operations considerably (U.S. Department of the Interior, 1995).

Unfortunately, successful spawning of native fish in the mainstream would still be near impossible because of the unchanged temperature of releases from Glen Canyon. However, the preferred alternative would permit unlimited access to tributaries and backwater areas which are used as larval and young-fish nurseries. Reduced fluctuations should also allow for moderate warming of backwaters, and would maintain the nutrients important to food resources. Some increases in the aquatic food base and stability of backwater and nearshore nursery areas would be expected (Arizona Game and Fish Department, 1993).

Increased minimum flows will have a positive affect on the aquatic food base that the fish and wildlife depend on. It will increase the amount of algae and invertebrates floating in the water, and will prevent them from exposure to the air and sun. Minimum flows under this alternative would reduce the degree of stranding experienced in the Glen Canyon reach. This is the problem of fish entering certain areas during times of high flow, but being cut off from the rest of the river when flows are lowered. The habitat maintenance flows (which are higher than normal flows) would be designed to reform and maintain backwaters for native fish. Without such flows, it is assumed that backwaters would fill with sediment, become colonized by vegetation, and lose their habitat value for young fish. (U.S. Department of the Interior, 1995).

Economics

Lake Powell generates over $400 million for local economies through tourism by 2.5 million visitors annually; many surrounding towns would literally cease to exist if the dam were removed. The dam provides the federal government with about $30 million annually from power sales, and the controlled releases supply water for 20 million people. The cost of removing the dam and restoring the area’s natural habitat has not been studied in depth, but would likely cost several billion dollars. Additionally, loss of electricity generated by the dam would lead to greater pollution by burning fossil fuels (Davidson, 1997).

Bibliography

• Angrandi, T.R., and Kubly, D.M. (1993). “Effects of Atmospheric Exposure on Chlorophyll, Biomass and Productivity of the Epilithon of a Tailwater River”, Regulated Rivers: Research and Management, vol. 8, pp. 345-358.
• Arizona Game and Fish Department. (1993). Glen Canyon Environmental Studies Phase II 1992 Annual Report. Prepared for the Bureau of Reclamation by Arizona Game and Fish Department, Phoenix, Arizona.
• Carothers, S.W., and Brown, B.T. (1991). The Colorado River Through Grand Canyon: Natural History and Human Change, University of Arizona Press, Tucson, Arizona.
• Davidson, Lee. (1997). “Powell Plan Encounters Rough Waters At Hearing”, Deseret News Web Edition, September 23, 1997.
• Sierra Club. (1997). “Let the River Run Through It”, Sierra, vol. 82, pp. 42-43. U.S. Department of the Interior. (1995). Operation of Glen Canyon Dam: Final Environmental Impact Statement. Bureau of Reclamation, Arizona.