Three Gorges Dam

China’s massive project to construct the Three Gorges Dam across the flood-prone Yangtze River brings together almost all of environmentalists’ fears. The Three Gorges Dam controls a drainage area of 386,300 square miles (1 million km2) and when complete it will be the world’s largest water conservation structure. The project’s leaders have assured their country and the world that the Three Gorges Dam will be a masterpiece of flood control and energy generation. Critics have cited other factors associated with the dam that will have worse effects on the environment.

Criticism of the dam centers on three health threats: (1) increased disease due to larger mosquito and other pest breeding grounds; (2) downstream droughts when flow is diverted for energy production; and (3) increased incidence of earthquakes due to the size of the structure in the Earth’s crust. George Davis, a specialist in tropical medicine at George Washington University in Washington, D.C., cautioned in 2008, “When it comes to environmental change, the implementation of the Three Gorges dam and reservoir is the great granddaddy of all changes. Once you dramatically change the climate and change water patterns, as is now seen in the Three Gorges region, you change a lot of environmental variables. Almost all infectious diseases are up for grabs.” Davis argues that the standing waters behind the dam create perfect conditions for swimmers to catch infections from polluted water, be invaded by parasites, and attacked by mosquitoes.

Since the Three Gorges building project began at the close of 1994, ecologists have wondered about all the environmental changes about to begin. Warnings came early in the construction, but the Chinese government found no reason to question the dam’s value. By 2007, however, leaders in China admitted that the environmentalists’ cautions about the Three Gorges project might have been right. The Xinhua news agency published the following statement released by the Chinese ruling party: “There exist many ecological and environmental problems concerning the Three Gorges Dam. If no preventive measures are taken, the project could lead to catastrophe.” All of the ecosystem damages, upstream and downstream, have begun to emerge in the Three Gorges project. The difference between this and other dams is the magnitude of the potential problems.

Sediments accumulating in the water behind the dam have prompted environmental engineers to worry about structural failure. Also, flooding of the lake behind the dam would cause lake waters to spread to sewer systems and landfills, and thus pollute the water when the lake recedes. These problems could occur in addition to the normal disadvantages to the environment that dams are known to cause.

Navigation has returned to normal on China’s important Yangtze River—a lock system raises or lowers oceangoing vessels—and some of the dam’s 26 generators have begun to produce energy. The dam uses two power plants on either side of the structure to produce 84 billion kilowatt-hours, or almost 1.5 times the energy produced by the world’s second-largest dam, which is shared by Brazil and Paraguay. The project’s leaders stress that this amount of energy will replace 40–50 million tons (36–45 million metric tons) of coal each year. Three Gorges Dam provides an example of the environmental questions, both troubling and hopeful, raised by massive dams.

Source of Information : Green Technology Conservation Protecting Our Plant Resources