Eco-environmental Problems Recognition And Health Assessment Of Wet-dry Zone In The Three Gorges Reservoir Area Of Chongqing

The Three Gorges Reservoir Area is an ecological threat in the upper section of Yangzi River. The construction for the ecological protection of this zone is vital to the well-operation of the Three Gorges Power Plant and to the healthy ecology in the drainage area of the mid-lower section of Yangzi River. After the operation of the power plant, a reservoir wet-dry zone will be formed, where the water seasonally rises to 30 meters high and extends to 349 km2 each year. The wet-dry zone is a key sub-system of the Reservoir ecology, a transitional area of ecology between the reservoir and the land, the most active area in transmission and conversion of substance, energy and information, as well as the unstable and vulnerable ecological area with dramatic changes of eco-environment, and currently is the largest artificial everglade and one of the most significant environmental capitals of China. The eco-environment of the Three Gorges Project is highly concerned in the world. The most important part of the project is the eco-environment of the Reservoir wet-dry zone as it is closely related to the stability of the one million migrants, to the economic and social development in the Reservoir area, and to the image of China. However, studies on the eco-environment in the Three Gorges Reservoir wet-dry zone are only in the initial stage, waiting for exploring. The study on recognition and assessment of the major eco-environment problems in the wet-dry zone would contribute to the theory of restoring everglade ecologies, provide scientific guidance technically and practically for planning the protective construction for the eco-environment in the wet-dry zone, and would be practically significant in protecting the ecological safety of the Reservoir and promoting the sustainable development of the Reservoir area.This thesis is supported by the innovative project of Chinese Science Academy:"Study on the Demonstrative Experiment of High-efficient Eco-agriculture and Environmental Protection and Cultivation Technology in the Three Gorges Reservoir Area", by the West Action Planning Project of Chinese Science Academy:"Study on the Demonstrative Experiment of the Controlling of Soil Loss and Surface-source Pollution in the Three Gorges Reservoir Area", and by the national supporting project for science of the Science and Technology Administration:"Study on the Technological Development and Application of Ecology Restoring and Integrated Treatment of the Wet-dry zone in the Three Gorges Reservoir Area". Taking Chongqing wet-dry zone of the Three Gorges Reservoir as an illustration, referring to relevant literature both home and abroad, and combining the field research in the wet-dry zone, this thesis probes into the recognition and assessment of the ecological problems with the insistence of 3S technology, and of the approaches of hierarchy analysis and fuzzy integrated assessment, etc. The major findings are as follow:1. Based on the discussion of the formation, area distribution, the eco-environment before and after the water storage and evolution trend of Chongqing wet-dry zone of the Three Gorges Reservoir, the major eco-environment problems are analyzed and predicted. Since the operation of the Three Gorges Power Plant, due to the submergence of the reservoir water and the seasonal rising and receding of the water each year, the water flows much more slowly, resulting in dramatic changes of the eco-environment, the ecology, the geographic landscapes and patterns in the wet-dry zone prior to the water storage. Consequently, a series of ecological and environmental problems will occur, including the sharp reduction of diversity of animals and plants in the wet-dry zone, the extinction of the special rare species in the Reservoir area, the decreasing of ecological types, the simplification of structure and functions; the degradation of landscape ecological system in the wet-dry zone, the simplification of landscape grouping, the loss and damage of landscape structure, the decreasing of landscape heterogeneity, and the appearance of desert-like landscapes; Moreover, the degrading purifying function of the wet-dry zone to the pollutants in the Reservoir land area will lead to the degrading of water quality of the Reservoir. The country surface-source is the major source of pollution. The pollution zone along the city banks is extending; the nutrition enrichment is growing at the estuary and at backwater of Branch Rivers; the stability of the Reservoir bank and the safety of the towns are endangered due to the increasing geological hazards.2. Based on the analysis of ecological function of the wet-dry zone of the Reservoir, according to the nature and degree differences of the interaction between human activities and the wet-dry zone, the types and degrees of the ecological and environmental problems and ecological characteristics resulted in, as well as the orientation of ecological functions and the primary protection subjects and the differences of measures, the indicators of major characteristic factors in classifying the ecological function types of the wet-dry zone are established. Hereby the ecological functions of the Chongqing wet-dry zone of the Three Gorges Reservoir are categorized into 5 types (15 sub-types), namely, the wet-dry zone needing protection from the intensive disturbance of urban human activities, protection from disturbance of town and country market human activities, protection for tourist attractions and island-like ecological landscapes, protection from disturbance of rural agricultural activities, and protection for gorges and valley landscapes. In addition, the area distribution, the orientation of major functions, and the characteristics of the ecological and environmental problems of various types are analyzed.3. In accordance with the principles and approaches of the theory of Health Assessment of Ecology, the indicator system of health assessment of Chongqing wet-dry zone of the Three Gorges Reservoir is established. Taking Kaixian County wet-dry zone as an example, a health prediction assessment of the protection and construction mode of the wet-dry zone is carried out, employing hierarchy analysis and fuzzy-integrated assessment. The result shows that the influence on the health of the wet-dry zone is "very heathy" employing "the mode of artificial everglade ecological protection zone". Such a mode is of the least risk, but is of high policy cost in implementation and thus need financial support from the state or the local government. The influence on the health of the wet-dry zone is "relatively healthy", employing "the mode of ecological experiment demonstration zone". This mode can maximize economic efficiency at certain ecological and environmental efficiency threshold, and thus is a mainstream approach in the construction of protection for the ecology and environment of the wet-dry zone. The influence on the health of the wet-dry zone tends to be "relatively healthy", employing "the protecting and attending mode of the wet-dry zone". Thus, this mode can be applied secondarily in the construction in protecting the ecology and environment of the wet-dry zone. The influence on the health of the wet-dry zone of "the mode of agriculture development and exploitation" is negative, tending to be "general morbidity". This mode, therefore, should be employed by the migrants of the Reservoir area or by the local farmers as less as possible to reduce the risk of water pollution in the Reservoir area.4. The environmental factors around and the management of the wet-dry zone of the Three Gorges Reservoir are very significant to the maintenance of ecology stability in the wet-dry zone, and to the prevention from the negative influences of environmental problems on the Three Gorges Reservoir resulting from the wet-dry zone. Guided by clear orientation and goals and based on the undergoing major protective constructions of the state, this thesis suggests a series of measures, including the establishment of protection experiment zone for the everglade ecology in the wet-dry zone of the Reservoir, the protection and cultivation of everglade ecology, the strengthening of prevention and treatment of rural surface-source pollution in the Reservoir area, the enhancement of Reservoir banks protection and geological hazards prevention and control, as well as the strengthening of protection construction for the land ecology of the Reservoir area.