To: World Commission on Dams Review Commission
From: International Rivers Network
After careful study by experts representing our organization, we fear serious and long-lasting effects may have already occurred in China because of the construction of the Three Gorges Dam. Our findings have been verified by some of the world's leading environmentalists and we are convinced that the potential of environmental damage from this project far outweighs any economic benefits. We have outlined our main reasons for opposition in the following letter:
The environmental impacts as a consequence of the construction of large dams is well documented in the scientific literature. The greatest effects will be on the patterns of erosion and deposition in the river, the unnatural flow regime downstream of the dam, and water quality and temperature will affect ecosystems downstream.
It is envisaged that sedimentation behind the dam will be a serious problem. The dam may trap 70% of bed-load behind the dam, thereby continually losing storage capacity. Possible silting-up of Chongqing's deep-draft harbor may also obstruct navigation. Silting may also impede the generation of electricity.
Erosion of bed and banks downstream, and channel lowering is another problem. Degradation, is expected to occur for hundreds of miles downstream, eroding flood control embankments, undermining bridge supports, changing hydrological regime of the river. The effects may be felt as far downstream as the mouth of the Yangtze - the delta may become eroded due to reduction in sediment. Although accommodating smaller flood events, it is argued that dam will not be able to contain largest floods, and so flood hazard will remain a problem downstream.
Aquatic and terrestrial ecosystems
Dams reduce downstream water temperature and downstream water levels may be artificially raised at certain times of year. Most fish sensitive to water temperature and stage especially for breeding which may result in reductions or elimination of native species. The flooding of gorge to produce reservoir will drown habitats. Presently endangered species include Chinese Sturgeon and paddlefish, Yangtze dolphin, Chinese tiger, Chinese alligator, Giant Panda, and Siberian Crane will come under greater stress.
Water pollution and disease
The Yangtze River is presently the biggest sewer in China. Pollutants from thousands of industrial plants and mining (including heavy metals such as arsenic, cyanide and methyl- mercury), agricultural runoff, residential wastewater, urban sewers, pollution from shipping enter the river. Obstructing river flow and slowing water will concentrate toxins and pollutants, which otherwise would have been washed downstream and out to sea. Furthermore, the cessation of annual flooding and deposition of fertile silt onto fields, resulting in increased use of chemical fertilizers and resulting associated problems of nitrate runoff and groundwater pollution.
Displaced people likely to suffer epidemics of infectious diseases (Anderson, 1999), in particular schistosmiasis (disease caused by tiny blood flukes that can damage liver and intestines). Over the past 5 years infection has dropped by 50% as a result of treatment with the drug praziquantel, but the changed cycle of flows downstream of dam may increase the number of water snails carrying the flukes. Infected snails are presently found 500 km above the dam, but previously could not transverse the rapids. In addition, ambient temperatures above the reservoir are expected to be 1oC warmer allowing mosquitoes carrying Japanese B encaphalitis and malaria to proliferate. Also as terrestrial animals seek higher ground to escape the flooding of the reservoir pest levels will be increased in surrounding towns and cities.
Loading of the dam structure and reservoir water on the Earth's crust may place generate further crustal stresses in an area already prone to small earthquakes. In 1958 a large landslide near the site generated a flood wave tens of meters high. Overtopping of the dam or dam breach could submerge towns and cities such as Wuhan.
We are concerned that this dam seems to be more a political project done for "prestige" reasons rather than sound financial investment for China. It seems clear to us that the Chinese government officials and the majority members of the feasibility study team have deliberately slanted the information to make it look as if the Three Gorges Dam was the best option for survival in today's world. The feasibility study's language indicates that the authors accept as a foregone conclusion that the Three Gorges Dam would be built along with other grandiose mega-projects affecting the Yangtze River. We strongly disagree with their assessment and feel that other energy options should have been pursued and would have worked much better while preserving the quality of life for existing plant, animal, and human species.