The Mode Of River Basin Cascade Hydroelectric Development And Its Impacts On The Water Environmental Carrying Capacity

The cascade hydropower development of river basin is the leading pattern of the water resource utilization in China. In consideration of the particular natural and economic environment of a given river basin, there are several typical modes of the cascade development. Moreover, though the hydroelectric cascade development can achieved considerable economic gain, it will induce different classes of negative impacts on the natural and ecological environment at the same time. The researches on how to choose the fitting mode of the cascade hydroelectric development for the specific river basin, evaluate and further minimize its negative eco-environmental impacts have been hot topics in hydropower planning and related areas. The major results of this dissertation are shown as below:Firstly, the Columbia River and Han river valley are selected as two typical river basin to analyze the features of different cascade hydropower development modes in three aspects, that is, the main task, the cascade layout, and the scheduling strategy.Secondly, the definition and content of both the positive and negative impacts on the water environmental carrying capacity of the cascade hydropower development are analyzed. On this basis, an evaluation index system of the water environmental carrying capacity in view of four directions is established, that is, the volume of sewage from the basins, the water supply, and the level of social productive forces.Thirdly, the impacts of the river basin cascade development on the water environmental carrying capacity is are analyzed in three aspects including the volume of sewage from the basins, the water environmental capacity and its self-purification ability, and the level of social productive forces.Fourthly, three rivers including Maotiao river, Shaxi valley, Liusha river are selected to summarize the water environmental problems after valley hydroelectric cascade development, and Liusha river is selected to explain the ecological operation of the upper most reservoir and the Fuzzy synthetic evaluation is adopted to evaluate the its water environmental impacts.The assessment results of those three rivers show that the agricultural, industrial and domestic sewage emissions continue increasing after the river basin cascade development, the regional mining, the process of urbanization after the river basin cascade development, and the declining of the water self-purification ability can induce the deterioration of water quality and eutrophication. However, these negative impacts could be remitted through optimized scheduling strategy of the Reservoirs upstream.Finally, the fuzzy model is adopted to evaluate and predict the WECC of the middle and lower reaches of Han River. The result shows that with the continuous development of the social productive forces, the advance of the efficiency of water consumption helps to improve the water environmental carrying capacity.