Three Gorges Dam

Largest dam in the world in China

At the heart of China, Three Gorges Dam is the largest hydroelectric dam in the world, the result of a water project and titanic energy, as do the Chinese know. China is rich in water with its large interior basin, formed by the blue river (Yangtze) and the Yellow River (Huang He). The Yangtze, the third largest river in the world and the largest in Asia, rises in the Tibetan plateau at 4900 meters in the Kunlun Mountains. It measures 6300 km long and flows into the South China Sea up to Shanghai. In its race to the sea, it receives more than 3000 tributaries. To control the course of the Yangtze River and produce energy, the Chinese have undertaken a huge project in 1993, which ends in 2009.
The three gorges of the Yangtze are known as Qutang, Wu and Xiling, they will meet the growing demand for water and electricity to China. The dam forming a lake 700 km long, larger than the African great lake, Tanganyika (673 km). A number of ancient cities have disappeared under the water (Fengdu, Dingfang, Yunyang, Zigui, Yichang...). The dam with a length of 2335 meters and a height of 185 meters, will have a reservoir of about 40 billion m3. The two hydroelectric plants on both sides of the dam, will provide in 2015, about 10% of China's needs for electricity, one with 12 turbo-generators and the other with 14 turbo-generators. Each of the turbines installed is rated at 700 megawatts, 18,200 megawatts, the equivalent of 14 slices of nuclear power plants.
This construction will certainly have consequences pharaonic land and water, but the biggest dam in the world must address regional disparities in China.
This whole area of the Yangtze River is a central device in the territory of China. Indeed, it occupies 1.5 million square kilometers, or 15% of Chinese territory, concentrating 38% of the Chinese population.
The dam will prevent flooding and to significantly increase the hydropower generation Chinese (about 85 billion kWh per year). The ocean-going vessels can reach 10 million inhabitants of the city of Chongqing.
Facilitated the connection between Chongqing and Shanghai for ships with the tonnage may be up to 10 000 tones, will strengthen the integrative role of the river as an essential cross Chinese territory.

Yangzi is required and who wants China to open up its territories and develop the market economy.
The regional development is thus a response to the often advanced hypothesis of a possible or imminent collapse of China (Chang, 2001).
 

Image: From space the great Three Gorges Dam (May 2006). The Yangtze Jiang flows from left to right. To the left of the photo, the water retention of more than 3 km wide, just upstream of the dam. We also see great white jets of water that flow valves in its central part.

Image: SPOT Image, 1998, on the left bank of the Yangtze, one sees the town of Zigui, now defunct.

Image: The Three Gorges Dam, above, built on the vast Yangtze River. Its 2335 meters long and 185 meters in height make it the first hydroelectric complex in the world. photo © China Three Gorges Project Corporation

The problem of silt

No site before the Three Gorges Dam, has used as many concrete. With its 185 meters high and 2 km long, the dam blocks the silt at its base, the silt is essential to the enrichment of the surrounding land. The silt will accumulate for decades and could prevent the monstrous machine running. One of the objectives of the dam was to control recurrent flooding of the Yangtze River. Floods had an advantage is that it fed land in the region and farmers downstream of the dam are quickly realized, crops are less abundant, soils so poor that it takes millions of tons fertilizer each year. The land is deprived of the river water that carries with it the silt nourishing, natural nutrients, nitrogen, phosphorus, magnesium, calcium and potassium.

Approximately 500 million tons of sediment trapped dam every year or 1 km3, it became such a problem that the Chinese have very cleverly put into circulation a small part of the sediment. At the bottom of the Three Gorges Dam, huge valves are periodically raised and current hunting sediment downstream. This purge system can not thoroughly clean the dam for 30 to 60% of the sediments remain despite all prisoners. The Chinese are convinced that the benefits outweigh the disadvantages.

Image: Three Gorges Dam. The water released from the other side of the dam.