The world's largest dam is the Three Gorges Dam on the Yangtze River in China. Structural work was completed in 2006. The dam is 2,309 m (1.4 mi) long and 185m 607 ft) tall, six times the size of the Hoover Dam. When its generators are installed and it goes online in early 2009, it will be the world's biggest power plant. The Three Gorges Dam will generate 18.2 GW, or about 2% of China's total power consumption. China's exploding economy needs power, and considerable effort has been placed towards alternative forms of energy which do not pollute the air, as China's primary source of energy is coal.
The Three Gorges Dam has been at the center of controversy since its construction was announced. Over 1,000,000 people had to be evacuated to avoid the flood basin it created, which is 660k m (410 mi) long and submerges 632 sq km of land. 1,200 towns and villages were relocated in preparation for its construction. Following an incident in 1975 during Super Typhoon Nina where 140,000 people were killed due to catastrophic dam failure, extra precautions were taken in the engineering and fault tolerance of the Three Gorges Dam. It will be guarded by large amounts of soldiers around the clock to deter possible terrorist attacks.
Despite frequent criticisms stating that the costs of the Three Gorges Dam could be as high as $100 billion US Dollars (USD), the actual cost is not likely to exceed $22.5 billion USD. Most of this is being paid for by a national tax on electricity. Officials have stated that the dam will pay for itself with power generation.
Part of the role of the dam is also to engage in flood control. It will decrease the number of major downstream floods from once every 10 years to once every 100 years. Its massive 22 cubic kilometer reservoir will regulate the flow of water, increasing during the big floods and releasing the water at a uniform rate, sparing people downstream from the devastating economic effects of floods. The Three Gorges Dam's reservoir will be 200 m (219 yards) deep when it is fully flooded.