Three Gorges Dam



Three Gorges Dam

Introduction

China's Chang Jiang River drains 1.8 million sq km/0.7 million sq mi and discharges 700 cubic km/170 cubic mi of water annually. The Chang Jiang region provides two-thirds of China's rice and is home to 400 million people.

The Chinese government is currently planning to build a dam on the river. The project will be one of the world's largest dams, take between 15 and 20 years to build, and could cost as much as £45 million (Cech, 2005).

The Chinese government is building the dam, with the help of international aid, and hopes to finish the dam by 2016. Three Gorges Dam will be over 2 km/1 mi long and 100 m/300 ft high. The lake it creates will be over 600 km/375 mi long. Over 1 million people will have to be removed to make way for the dam and the lake. The Chinese government claims that the main benefits brought by the dam will be an increase in energy, improvements to navigation, improved irrigation, and reduced flood risk.

Proposed Benefits of the Dam

The dam will generate up to 18,000 megawatts of electricity, more than the world's largest existing hydro electric dam, the Itaipu in Paraguay. It will enable China to reduce its dependency on coal. The aim is for it to supply electricity to Shanghai, one of the world's largest cities, and Chongqing, an area earmarked for economic development (CIPM, 1988).

The dam should also allow shipping to travel the river above the Three Gorges, in an area where there are currently rapids. The dams will raise water levels by 90 m/300 ft, and turn the rapids into a navigable lake. The lake will also make improved irrigation throughout the surrounding area possible.

Another of the perceived benefits of the dam is that it will protect 10 million people from flooding (since 1860 over 5 million people in China have died as a result of flooding).

Possible Disadvantages Of The Development

Not everyone agrees that the dam is a good idea. Some argue that most floods in recent years have come from rivers which join the Chang Jiang below the Three Gorges Dam, and that the development will therefore not improve the flooding problem very much. At the same time they point out that the region is seismically active and that landslides are frequent. Large dams can trigger earthquakes (the weight of the water causes increased pressure on the rocks) and the forced movement of people to higher, steeper ground will result in increased landslide activity (increased effect of gravity and removal of vegetation cover as people need to farm the land).

Silt may pose another problem. Up to 530 million tonnes of silt are carried through the gorge annually. The first dam on the river lost its capacity within seven years and one on the Yellow River filled with silt within four years. The port at the head of the lake may become silted up as a result of increased deposition and the development of a delta at the head ...