Fact Sheet:
Three Gorges Dam Overview
The Three Gorges Dam (TGD) is currently being constructed in China on the Yangtze River. A number of aspects of the project are controversial, and it is unclear whether there will be more benefits or negatives associated with the project. Some of the pro and cons of the project are highlighted below in green and red, respectively.
Structure
2.3 km (1.4 miles) wide 1
185 m (607 ft) tall 1
28M m3 (34M yd3) of concrete 1
the world's highest vertical shiplift.
Construction
Construction began in 1993 and is expected to last 17 years. The 2nd stage was just completed in June 2003. The project is estimated to employ 250,000 workers5, although only 30,000 were reportedly on site in 19998, making it beneficial to the local economy. Current challenges relate to keeping on schedule while ensuring quality. These issues have been cited as contributors to cracks that have been recently observed.
Energy Production
The new dam will produce 10% of the total energy capacity in China. It will include 26 turbines each rated at 680 MW [total 17,680 MW]. This represents an equivalent energy output as:
15 nuclear power plants 9
50M tons coal/yr 1
25M tons crude oil/yr
The environmental impacts, particularly air pollution, from hydropower should be less than these alternative energy supplies. For example, a coal facility of similar size will produce one to two million tons of sulphuric dioxide, 10,000 tons of carbon monoxide, and 150,000 tons of dust more than the energy from TGD.4
Flood Control
A key motivation for the project was flood control in the region. For example, in 1975 a local flood caused 60 dams to break, killing up to 230,000 people directly and resulting in 11M people later getting sick from resulting disease, food poisoning, and famine.2 The TGD has theoretically been designed to withstand a 1000-yr flood condition.
Navigation
Due to the water retained behind the dam, 10,000-ton ocean-going commercial ships will now be able to reach Chongqing.2 This will increase the annual one-way navigation capacity from present 10 million tons to 50 million tons, and a decrease navigation costs by 35~ 37 %. 1
Silt Accumulation
It is a concern that sediment build-up behind the dam will significantly impair its ability to deliver the designed energy, control floods, and improve navigation. For example, the Three Gate Gorge dam on the Yellow River produces less than one-third of the power that was promised because its turbines are damaged by sediment.2 However, the problem has been studied for 30 yrs. The dam design and operating strategy are expected by some to avoid sedimentation problems.1 Others have pointed out numerous errors and uncertainties in the sediment estimates, and point out that the operational strategies are untested on a dam the size of the TGD.2
Geology
The geology in the area is a key to the success of the project. Already, minor earthquakes have been noted in the area and attributed to the filling of the dam. Further concerns are related to the stability of the walls of the canyon. A positive is that at the TGD location the bedrock is sound, intact granite with high (100 MPa) compressive strength and low permeability.1
Societal Impacts
A key detraction from the project is the extensive population relocation that is needed due to the reservoir created by the dam, that will submerge 19 cities, 326 towns, 1351 villages.2 Estimates are that 1.1-1.9 million people will need to relocate.2 In addition, 30,000 hectares of prime agricultural land will be submerged, and it is unclear if arable land can be found to replace the loss.2
Water Pollution
It is likely that the dam will result in poorer water quality in the river. First, old mines and other contaminated sites will be submerged and leach contaminants into the river. Second, the “static” water in the reservoir behind the dam has a much slower pollutant degradation rate than in flowing water. This is of particular concern due to the large quantity of untreated wastewater (sewage) that is released into the river. The water will likely have more smell, higher pathogen concentrations, and will be less likely to support aquatic life such as fish.
Endangered Species
Various endangered species may decline more rapidly as a result of impacts from the TGD, including the baiji dolphin (shown below), the ancient river sturgeon, the finless porpoise, and Siberian cranes (shown below).3
A significant number of various fish species are also likely to be negatively impacted.
Archaeology sites
Over 1,000 sites in need of protection have been identified2, but depending on government funding only a few (perhaps 10%7) can likely be preserved. In addition, there may not be enough time to evaluate all the potential sites or determine ways to preserve them prior to being flooded.2 Examples of sites include world-renowned low water calligraphy carvings potentially dating back to A.D. 618 and 25 B.C. and a subsurface site of the Daxi Culture dating back as far as 5,000 B.C. 2
Costs
Estimates of total costs vary, in part due to what is included such as relocation, rebuilding of roads, cities, power lines, etc. The official cost estimate is $22B (US)6. A pessimistic estimate is $75B (US)2.
Recommendation: Against, due to uncertainties.
References
1. CTGPC. A Brief Introduction to the Three Gorges Project On The Yangtze River. Hubei, China. Accessed 8/1/03.
2. Qing, D. 1998. The River Dragon has Come! Ed. J.G. Thibodeau, P.B. Williams. Translated Y. Ming. Probe International, IRN. Armonk, N.Y.
3 PBS. Great Wall Across the Yangtze. Accessed 8/1/03.
4. Embassy of the People’s Republic of China in the United States of America. Three Gorges Project and China's Economy. Nov. 4, 1997. embassy.org/eng/6894.html. Accessed 8/1/03.
5. Kennedy, B. 2001. China's Three Gorges Dam. china.50/ asian.superpower/three.gorges/ Accessed 8/1/03.