Huge Dam Seen by Satellite

Mother Nature is providing the raw energy for the world's largest hydroelectric power generator currently being built. The Three Gorges Dam is easily one of the few man-made structures that's actually visible to the naked eye from space.

Construction of the dam along the 3,900 mile-long Yangtze River—the world's third largest river—is scheduled to be completed in 2009. At least $625 billion is being spent to erect the dam, which is 600 feet tall and mile-and-a-half long—five times larger than Hoover Dam on the Arizona-Nevada border.

These NASA Landsat satellite images, released this week, provide detailed, vivid views of the dam since its inception in 1994. The earliest data set, from 1987, shows the region prior to construction. By 2000, construction was underway, but sediment-filled water still flowed through a narrow channel near the river's south bank. The 2004 data shows development of the main wall and partial filling of the reservoir, including numerous side canyons. By mid-2006, construction of the main wall was completed and a reservoir more than 2 miles across had filled just upstream of the dam.

In addition to being designed to produce more than 18,000 megawatts of electricity when all 26 turbines become operational in 2009, the dam is expected to greatly improve flood control on the river and protect the 15 million people and 3.7 million acres of farmland in the lower Yangtze flood plains.

However, controversy stems from the dam's effects on the local environment. In March 2007, reports indicated that the dam's reservoir is polluted with industrial waste. A study also has shown that the structure has blocked sediment flow along with the river leading to a significant decrease of nutrients that people have depended on for agriculture to flourish. NASA satellites are being used to help determine how changing land cover and use may influence climate and the environment.

—LiveScience Staff

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Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio United States Geological Survey