Environmentally profound10 September 1998
The environmental impacts of the Three Gorges project in China will be extensive. However, as Wang Rushu* explains, the project company is taking such concerns seriously through the implementation of various mitigative measures
The Three Gorges project (TGP) on the Yangtze river is the largest water resources project in the world and, consequently, its impact on the environment, local people, species, cultural relics and water quality will be widespread and profound. However, various environmental benefits will be experienced on the middle and lower basins of the Yangtze. After project completion flood control in the Jingjiang reaches of the Yangtze will be raised from less than a 10-year frequency to a 100-year frequency. Meanwhile the regulation of the reservoir will help prevent the disease schistomiasis and extend the life span of Dongting Lake due to reduced deposition of sediments.
TGP will provide 84.68B kWh of hydro power a year — the plant will replace approximately 50Mt of coal which would have to be burnt for a coal-fired plant. Furthermore, the project will help to improve local navigation and climate and enhance the water quality below the dam during the dry season. The operation of the project will ease salt water intrusion in the river mouth region and the increased water surface area will promote aquatic culture in the new reservoir.
In contrast, the main negative impacts will be exerted on the upper reaches and include the large amount of farmland which has to be flooded and the number of people who have to be relocated.
According to a 1992 survey the TGP reservoir will inundate 25,900ha of farmland and orchard and 846,000 residents living in the affected area. Taking into consideration population growth and relocation during the construction period, the total population resettled will be over one million.
The Chinese government has defined a development orientated resettlement policy which will not merely compensate but should promote economic development of the reservoir region to benefit relocated people. The programme should also maintain relocated people’s living standards and give the opportunity for them to achieve a higher standard in the future.
After impoundment higher water levels and wider channels will modify the scenery of the canyon to a certain extent. The level of the future reservoir will be 175m, 40-110m higher than the river at present. However, the steep canyon enclosing the river valley will be untouched and improved navigation will provide access to new scenic views, such as the Little Three Gorges in the Daning river.
Impoundment of the river will affect 44 archeological sites and ancient monuments. The most famous ones such as Ghost City in Fengdu county, Baidicheng (White Emperor City) in Fengjie County and Huangling Temple in Yichang City will not be inundated. Lower archeological monuments such as Zhang Fei Temple (el 137m) and Qu Yuan Temple (el 150m) will be relocated to higher places. Other sites and monuments will be either excavated, protected or relocated.
There are 47 rare or endangered species in the area surrounding the reservoir, most of them are growing between 300 and 1200m asl. There is almost no natural vegetation in the inundated area and the impoundment will not cause serious losses.
Rare animals in the Yangtze basin, such as the Chinese river dolphin and the Chinese sturgeon will be protected by measures such as the establishment of natural reserves and artificial spawning habitats. It is acknowledged that the construction and operation of TGP will affect their habitats to a certain degree, so it is necessary to ensure that effective counter-measures are continuously implemented.
Systematic survey and research indicate that the habitats of the Yangtze alligator and Siberian crane will not be affected by the project.
The total waste water discharge in to the reservoir area amounts to more than 1.2Bt annually. However, the water quality in the Yangtze does remain quite high, except for pollution belts along the banks near cities, due to the large quantity of runoff. The slower flow velocity of water in the reservoir and higher water level created by TGP will aggregate shoreline pollution along this stretch of the river. This impact needs to be mitigated by improved waste water measures.
Environmental protection is one of the basic policies in China and has been taken seriously at TGP. Much consideration has also been given to the negative environmental impacts of the construction work taking place at the dam site. The following points have been focused on:
•A maximum daily drainage of 276,000t will be drained from the foundation ditch of the second phase coffer dam. This drainage will have a pH value of 11-12 with a higher turbidity.
•During the peak period of construction daily domestic sewage and discharge will reach 6-10,000t for 40,000 people on the construction site.
•A large quantity of oil-containing waste water will be produced from 3000 sets of mechanical facilities.
•The daily dust deposition from peak explosion will be up to 1t/km2.
•Noise from drilling, explosions, aggregate processing, concrete batch plants and heavy truck transportation may reach as high as 80-100dB.
•Some diseases such as lung fluke, leptospirosis and malaria have prevailed in the Sandouping region in the past. It is acknowledged that during the construction phase a large number of people will come to the site which may cause diseases to spread.
Counter-measures are being implemented to mitigate such negative impacts. Spoils and solid wastes produced by the construction process are being disposed of properly; attention is being paid to the natural landscape to ensure that vegetation is restored in the quarry area; and afforestation will be carried out on the construction site to prevent soil erosion.
Anti-epidemic measures have also been implemented to prevent the potential prevalence and spreading of diseases. Finally, an Ecosystem and Environmental Supervision and Monitoring Centre has been established at the dam site to ensure effective management of such environmental protection measures during the construction phase.