The Three Gorges Dam Project

Environmental Impacts

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The environmental impacts associated with large scale dams often have significant negative impacts on the environment. The Three Gorges Dam is no different. The creation of the dam and associated reservoir has impacts both upstream from the dam and downstream. It affects species in the area, some endangered, water quality, and may increase the likelihood of earthquakes and mudslides in the area.

A number of species will be adversely affected by the construction of the dam. There are 300 species of fish in the Yangtze River. The dam will create a barrier in the river that these species will not be able to cross. Fish will not be able to travel upstream to spawn, so the populations of the species will decrease. Other affected species include the Chinese River Dolphin, Chinese Sturgeon, Chinese Tiger, Chinese Alligator, Siberian Crane, and the Giant Panda. There are a total of forty-seven rare or endangered species in the Three Gorges Dam area that are protected by Chinese national law. The only natural habitat of the Chinese River Dolphin is the Yangtze River, and there are less than one-hundred of these endangered dolphins in the river. The reservoir created from the construction of the dam covers a significant amount of the dolphins’ natural habitat. The government plans to sustain the River Dolphin and other endangered species by creating natural reserves and artificial spawning programs. It should be noted that past attempts to relocate the Yangtze River Dolphin have failed.dolphins in the river. The reservoir created from the construction of the dam covers a significant amount of the dolphins’ natural habitat. The government plans to sustain the River Dolphin and other endangered species by creating natural reserves and artificial spawning programs. It should be noted that past attempts to relocate the Yangtze River Dolphin have failed.

Photo of the Baiji Dolphin. Its only natural habitat is the Yangtze River.

Towns and forests located in areas that will be inundated will have to be demolished and removed in order to increase navigability on the river. The loss of forests and agricultural lands will lead to erosion and the build up of sediment at the base of the river and reservoir. This could lead to increased flooding upstream. Sediments and silt contain valuable nutrients necessary to agricultural production. The blocking of sediments behind the dam means that these nutrients may not reach fertile farmland downstream of the dam. This could reduce the fertility of the land.

The destruction of the villages also leads to problems of pollution. The Yangtze River is already polluted from the shipping of coal, acid rain, and its central location in Chinese industrial activity. Pollutants from towns and waste dumps that will be inundated will add to this pollution. Some funds were set up to aid in cleaning the area for the reservoir, but only the future will show whether a sufficient job was done. Water moves slower in the reservoir and some are concerned that the pollution will sit and worsen water quality of the river.

Overhead view of Three Gorges Dam. Note flooding of land on left side of the photo. Courtesy of European Space Agency.

Other consequences of the Three Gorges Dam are lower temperature and dissolved oxygen content in water down-gradient from the dam. Dissolved oxygen is necessary for healthy aerobic activity in aquatic ecosystems. Fish and plants depend on oxygen to survive. The presence of the dam will disrupt the natural processes of aeration (the movement of water) and diffusion, ways oxygen dissolves into water. Water will move more slowly downstream, thus making it more difficult for available oxygen to be present in the water. This could have a negative impact on the aquatic ecosystem downstream.

Some positive results of the Three Gorges Dam include the use of water, a natural and renewable resource, as an energy supply. Hydroelectricity is clean since no greenhouse gases are emitted from producing this type of energy. The Three Gorges Dam will replace up to 50 million tons of raw coal in China’s energy use, prevent more acid rain, and improve health standards, since the air will be cleaner.

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