Points of View: The Three Gorges Dam

China’s Yangtze River is the third longest river in the world after the Nile and the Amazon. The Yangtze River flows through the Three Gorges region of central China, which is famous for its natural beauty and historical sites. For thousands of years, the area’s sheer cliffs have inspired paintings and poems. This idyllic region seems like the sort of place that would be protected as a park or reserve. But in fact, it is the site for the Three Gorges Dam—the largest hydroelectric dam project in the world. Now that the dam is fully operational, the Yangtze River forms a reservoir that is 595 km (370 mi) long—as long as Lake Superior. In other words, the reservoir is about as long as the distance between Los Angeles and San Francisco!

Advantages
The dam has several purposes. It controls the water level of the Yangtze River to reduce downstream flooding. About 1 million people died in the last century from flooding along the river. The damage caused by a severe flood in 1998 is estimated to have cost as much as the entire dam project. During dry times, release of water from the dam increases fresh water for agriculture and people downstream.

The dam provides millions of people with hydroelectric power. China now burns air-polluting coal to meet about two-thirds of the country’s energy needs. With all its  turbines operational, the dam will provide enough electrical energy to power a city that is 10 times the size of Los Angeles. With the Yangtze’s flow controlled, the river is deep enough for large ships to navigate on it, so the dam will also increase trade nearly ten-fold in a relatively poor region of China.

Disadvantages
The project has many drawbacks, however. The reservoir behind the dam has flooded an enormous area. Almost 1.5 million people living in the affected areas were relocated— there were 13 cities and hundreds of villages in the area of the reservoir. As the reservoir’s waters rose, they destroyed fragile ecosystems and valuable archeological sites.

Pollution in the Yangtze River above the dam has increased much more than anticipated by engineers. Slower water flow fails to flush away sewage and other pollution. Flooded urban and industrial areas contribute a mixture of other pollutants.

reservoir

This aerial view shows the reservoir that formed behind the Three Gorges Dam.

Long-Term Concerns
Before construction, some people raised concerns about geological instability that might result from so much added weight. Experience is justifying those concerns. The dam was built over a fault line. In late 2011, Chinese government officials acknowledged that regular landslides and earthquakes were increasing dangers for local people. Another concern is that the reservoir may quickly fill with sediment. The Yangtze picks up enormous amounts of yellowish soil and sediment as it flows across China. With the river slowed by the dam, much of the silt is deposited in the reservoir. As sediment builds up behind the dam, the deposited sediment will reduce the size of the reservoir, limiting the flood prevention and power generating capacities of the dam. In addition, productive farming regions below the dam will be deprived of the fertile sediment that is deposited every year when the river floods, and river banks may become more eroded because the river carries less replacement sediment from upstream.

Hidden Costs?
The official cost of the project is $25 billion, but other sources give estimates of two to three times that amount, due to environmental costs. It is hard to assign an economic value to the loss of wildlife diversity in this area that previously supported many unique species. The true cost of the dam may never be known because corruption and inefficiency have plagued the project from the start. For example, money sent to compensate 13,000 people relocated near Gaoyang disappeared, and no people received payments. These negative effects of the Three Gorges Dam project will be difficult to remedy, but even more dams are planned for the Yangtze River.

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