Building the World’s Largest Dam
In an interview with the London Times, the Three Gorges Dam general manager, Li Yougan, hinted that the dam is “the grandest project the Chinese have undertaken” since the Great Wall of China. Despite producing environmentally friendly hydropower to the region, the new dam has provided civil engineers with a wide array of challenges, which now leaves them in search of solutions to ensure the dam can remain without threatening the public and the environment.
A New Concept for an Old Idea
The Chinese government conceived the Three Gorges Dam project centuries ago when the Republic of China founder Sun-yat Sen considered constructing a dam on the Yangtze River as early as 1919. At the time, the leader was more concerned with flood protection rather than power generation. It wasn’t until roughly three-quarters of a century later that Chinese leader Mao Zedong revived Sen’s plan and construction of the dam began in 1993 and opened in 2003.
The Three Gorges Dam:
- Measures one and a half miles long
- Stands 607 feet (roughly 56 stories) high
- Required 21 million cubic yards of concrete to complete
- Produces upstream water levels 456 feet above sea level
- Required over one million residents to relocate
- Could cause a 50 percent reduction in needed sediment nutrients
- Houses 26 turbines
- Produces 18,000 megawatts of power
- Blocked 10 million tons of debris from entering the ocean to date
The Three Gorges Dam earned its name because it empties into the Qutang, Wu Xia and Xiling Gorges rivers, which collectively span 124 miles. The cost of the dam is reported at $24 billion. Chinese officials believe this high cost will be worth it as the project is projected to sharply reduce the number of deaths caused by floodwaters.
Challenges Facing the Three Gorges Dam Project
Since construction approval in 1992, the Three Gorges Dam project has been met with opposition from the Chinese scientific community, including warnings for increased landslide activity and water transmitted illnesses, as well as a potential decrease – or even extinction – in area wildlife. Unfortunately, many feel that these concerns were validated when landslide activity began shortly after the first artificial increase in the water level during the construction of the dam. Surrounding soil was unable to withstand the additional water pressure, causing the landslides to produce 65-foot waves that claimed 14 lives. Furthermore, as engineers raised the water level more to continue with the dam project, additional landslides resulted.
Geologists blame the landslide activity on three factors related to dam operations. The first is that the added moisture caused water to seep into the loose soil supporting rock cliffs. Additionally, the waxing and waning water levels, both artificial and natural, furthered the issue. The final factor was that the dam rests above two major fault lines, which scientists fear will begin to move after agitation from the increased landslide activity.
The changing water levels also increase the potential for extinction. It can threaten to flood the habitats of some of the rarest animals and plant life in the world. For some fish, the drop in water levels could leave the entire species stranded in lakes and unable to reproduce and feed. On land, the water table increases cover connecting land bridges, which could leave species stranded on newly created islands. Scientists argue that the true impact of the dam on area wildlife will not reveal itself for another 15 years.
The Chinese government touted the Three Gorges Dam as protection against massive life-threatening floods and regular flooding, both which can threaten human life. Since the dam’s construction, central and northern China have fallen victim to droughts, and in certain areas the water table has fallen to its lowest levels in almost 150 years. As a result, low water levels have left many ships in these areas stranded while the drought is causing water shortages in some areas.
When fresh water is not readily available, salt water takes its place. As a result of this, jellyfish who feed on endangered indigenous fish species can now survive in areas they could not before. The change in habitat is also allowing snails, which carry diseases that are harmful to humans, to breed in overabundance. Water quality around the dam is below acceptable health standards due to the blockage created by the dam. Scientists fear that, as the environment continues to change, more diseases will follow.
The Three Gorges Dam project serves as a valuable case study in which civil engineers can learn. They need to understand and plan, as best as possible, for challenges that could affect the public’s health and well-being as well as the surrounding environment. To help resolve the challenges faced in the Three Gorges Dam project, civil engineers have developed environmental impact assessments to help further identify and address the environmental or public health concerns of the area.
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China's Three Gorges Dam, by the Numbers, National Geographic
China's Three Gorges Dam: An Environmental Catastrophe?, Scientific American