|Fig. 1: Three Gorges Dam. (Source: Wikimedia Commons)|
The Three Gorges Dam, located on the Yangtze River in China, is the largest hydroelectric dam in the world; it is 1.3 miles wide, 610 feet high, and has a 410-mile reservoir behind it.  Fig. 1 shows how large the dam is. The project cost $24 billion, and took thirteen years to complete, from 1993 to 2006. [1,2] The dam was constructed to generate power and control flooding, and is estimated to generate about an eighth of China's energy.  It produces eight times the amount of energy that the US Hoover Dam generates.  The dam reached a full generating capacity of 18.2 GW in 2010. 
One benefit of the dam is that it produces electricity through hydroelectric power instead of through the use of fossil fuels; generating energy does not release any greenhouse gases, which improves air quality even with more electrical use. [1,3] Thirty two Francis turbines, shown in Fig. 2, produce 700 MW of energy each; turbine efficiency averages above 94%, showing how important the dam is in generating electricity for China.  The dam also reduces seasonal flooding, which has contributed to over one million deaths over the past 100 years. 
|Fig. 2: Francis Turbine.(Source: Wikimedia Commons)|
The Three Gorges Dam has negative environmental impacts. In 2008, Chinese officials admitted that the dam could be harming the environment through landslides and fragmentation or changing of ecosystems.  The unstable sides of the river bank had the potential to cause landslides, and the significant weight of the water in the reservoir behind the dam had the potential to cause earthquakes. [3,6] Additionally, the dam submerged the beautiful cliffs and mountains that had once lined the Yangtze River, ruining the natural beauty and cultural relics that were on the banks.  Deforestation also took place as areas had to be cleared in order for there to be space to build the dam, as well as so that people who were displaced could build new homes or farms.  Wildlife was also severely impacted. According to an EIA report, there were 47 endangered species in the area surrounding the dam, which included the Chinese River dolphin and the Chinese sturgeon.  After construction of the dam, the Chinese river dolphin went officially extinct, and there are thought to be only 1,000 sturgeons left, showing a significant impact by the dam on wildlife.  Migrating fish have also had trouble breeding because the dam changed their migrating path, which also had an impact on the animals that depend on them; for example, migrating salmon are food for bears.  The dam has also had negative social impacts, especially on farmers and people living in the area surrounding the dam; 100,000 acres of farm land, 1,600 factories and mines, 13 cities, 140 towns, 1,352 villages were flooded by the dam, and nearly 2 million people were displaced.  Farmers were also left with no land to farm, and had to find new jobs. 
The Three Gorges Dam is controversial because it has both benefits and costs. On one hand, the dam provides clean energy, which reduces burning of fossil fuels and improves air quality; it also reduces flooding. [1,3] On the other hand, it has a significant amount of social and environmental impacts, making it important to question whether the dam is having positive or negative affects in China.
© Britt Mikkelsen. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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 Y. Ma, "Three Gorges Dam," Physics 240, Stanford University, Fall 2010.
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