Research On Water Requirement Of CHIBUSU Watershed Ecosystem After Exploitation Of Cascade Hydropower Stations

With the accelerate development of the western area in our country, the exploitation of water resource in Sichuan Province has been came to head. It brings not only a prominent economy and social benefit, but also diverse ecological and environmental problems due to unduly exploited water resource for hydropower projects. The more attention has often been paid only on the social and economic water requirement and less attention on the eco-environmental water requirement during the most of the planning for constructions of hydropower projects, which leads to the damage of environment and seriously affects the eco-environmental balance and sustainable utilization of water resources. In order to keep the stability and sustainability of the eco-environment in the whole drainage basin, it is very important that how to satisfy the eco-environment water requirement of that drainage basin in the development planning of a cascade hydropower project.On the basis of analyzing and review of researches on eco-environmental water requirement in domestic and oversea, it has been explored that how to guarantee the eco-environmental water requirement of the drainage basin from the principle, components and related calculating theory in this dissertation, with considering some main factors which affect the eco-environment of the basin due to the construction of cascade hydropower station. Combining with the environmental evaluation of the development of cascade hydropower stations on Chibusu Drainage Basin in Abazhou, the eco-environmental water requirement of this basin is studied. After substantive investigations for natural, social and economic circumstances of Chibusu Drainage Basin had been done, the current situation of system function of this basin has been analyzed, and the impact of construction of cascade hydropower station to the drainage biological environment has been predicted and evaluated. With the calculating theory of eco-environmental water requirement for Chibusu Drainage Basin, the minimum water requirement to sustain the eco-environment balance of this basin has been obtained.Combining with the characteristics of Chibusu Drainage Basin and the environmental evaluation of the development of cascade hydropower stations, the calculation methods for eco-environmental water requirements of this basin are as the followings. R2CROSS method is chosen to calculate the habitat water requirement, water quality prediction method is used to calculate the self-purification water requirement, experience-parameter method is selected to compute sight-seeing and entertainment water requirement, and rated-area method is assigned to compute the drainage production and resident living water requirement. With the above estimation computing, the eco-environmental water requirements (abr. EWR) of each reaches of Chibusu Drainage Basin are listed as belows:(1)the EWR up the reach of Weicheng power station is 0.62m~3/s;(2) the EWR of the reach between Weicheng power station and Dazhaizi is 0.83m~3/s; (3) the EWR of the reach between Dazhaizi and Chibuzhai is 1.06m~3/s, and (4) the EWR of the reach between Chibuzhai and Lianghekou is 1.47m~3/s. Totally, a 10.2%-12.6% of the perennial average flux of Chibusu River in roughly is required for EWR, In other words, at least 10.2%-12.6% of the whole flux of Chibusu River is needed to support the aquicolous biology inhabitation and vegetation of the Chibusu drainage, and to satisfy the functional water requirement for self-purification and common sight, and what's more, it has the ability to ensure the ordinary production, living and botanic growth water requirements.