Aerial view of the Hoover Dam on the border of Arizona and Nevada.

In many ways, these dams have been successful. Irrigation of the Western United States, for example, has allowed large-scale farming to flourish in arid conditions. India’s irrigation systems have enabled that country to become a self-sufficient producer of food for over one billion people. Dams have helped in reducing the life-threatening problems of famine as a result of drought, devastation from floods, and disease.

Despite these benefits, the widespread damming of rivers has come under increasing criticism due to a wide range of unintended negative consequences. The adverse effects of dams include the disruption of ecosystems, the decline of fish stocks, the forced resettlements of communities, and, in some cases, increases in disease. New damming projects face increased opposition. Despite this, the world’s largest dam is nearing completion in China.

China’s Yangtze River is the world’s third largest river. It stretches for 3,700 miles across China and provides life-sustaining water for millions of people who live in the Chinese countryside. It irrigates the majority of the crops that feed the rest of country. The Yangtze’s life-giving waters can also cause devastation and death. Throughout thousands of years of Chinese history, the Yangtze has flooded on an average of about once every ten years. These floods have caused great losses of life and infrastructure. As more and more businesses and factories sprung up along the river, there were increased calls to dam the Yangtze. After decades of debate, construction of the Three Gorges Dam was begun by the Chinese government in 1994. Originally scheduled for completion in 2007, delays have pushed the completion date back to 2011.

Critics of the Three Gorges Dam continue to warn that when the project is completed, it will destroy the delicate ecosystem of the river, killing many of the fish and dramatically increasing pollution of the Yangtze as it becomes increasingly stagnant. Further, the flooding of the area behind by the dam will bury archaeologically valuable temples and burial grounds, as well as causing the forced displacement of between four and five million people.