The Operating Simulation Of Cascade Reservoirs And It's Impacts On River Eco-environment

The impact of basin hydropower development on eco-environment always is one of the front and hot topics in the hydrology and water resources domain and reservoir group union-operation in large-scale basin is the key problem to basin water resources management. This paper studies on the reservoir group operation simulation in upstream of Yangtze River, which is important to water security and safeguarding in Three Gorges area. in addition this paper also studies the response of the Three Gorges cascade reservoir under different reservoir group operating options in upper reaches of Yangtze River, which had important practice application value.On the basis of a research on substantial quantity of literatures worldly, the research progresses and developments on the impact of combined operating of reservoirs and hydropower cascade. Hydropower cascade development in the upstream of Yangtze River was comprehensive surveyed and the status and layout of reservoirs was grasped. Moreover the simulation system of reservoirs operating in the upstream of Yangtze River was established by coupling the confluence of river network model and reservoir operating. And then the different reservoirs operating modes were simulated by using this model. The response of Three Gorges cascade reservoirs to different reservoir operating modes and river runoff variations were analyzed. The impact of reservoir groups operating on ecological environment was analyzed and the ecological basic flow was studied. Finally, the problems of hydropower cascade development of upstream of Yangtze River were discussed. In general, the main achievements of this study were concluded as follows:1,The data of related reservoir parameter and hydrologic station historical flow were collected, reorganized, and analyzed. Hydropower development Status and hydropower planning of the upstream of Yangtze River were investigated and large reservoir parameters were collected; the pattern of cascade hydropower development in future was analyzed; Historical flow data of main hydrological station in the upstream of Yangtze River were collected, reorganized, and change trends of runoff were analyzed.2,Established the Yangtze River upstream reservoir group operating modelYangtze River upstream river routing of flow model was built. Routing was simulated by using Muskingum method and its successive routing in sub-reaches and adopted"routing-resultant-routing"or"resultant-routing-resultant"method. And the parameters were calibrated by using of historical data. The reservoir operating model was built according to objectives of reservoir design and parameters of upstream. reservoir storage capacity curve was modeled and a new method was used to establish reservoir operating graph. Coupling the reservoir operating model and river routing of flow model, then we can get the reservoir operating model Yangtze River upstream reservoir groups operating model.3,different reservoirs operating modes were simulated by using this modelDifferent operating modes such as reservoirs group combination and water store schemes were simulated by using this model; the impact of different operating modes on runoff progress and storing water & electricity generating of Three Gorges. The results showed that: since water storage of reservoirs upstream, the total runoff annual was reduced, especially after flood season, but the runoff on dry season was increased, which could ensure less abandoned water and more time of generate electricity at high water level. It is benefit to generation of Three Gorges. In addition, it is helpful for Three Gorges to stagger the scheme of Three Gorges and reservoirs upstream.4,Studied the effect on ahead the storing water scheme of Three Gorges after flood seasonIn recent years, the amount of sand-load decreased in Three Gorges reservoir which makes it possible to ahead of Three Gorges water storage scheme after flood season. The rainfall and runoff was reduced, especially after flood season, it is necessary to ahead of Three Gorges water storage scheme after flood season. Different storing water scheme of Three Gorges after the flood season was simulated, and the results showed: ahead of Three Gorges water storage scheme could ensure storing water to the regular high water level better and helpful to bring the benefit of Three Gorges Project. At the same time, it wouldn't increase risk of the flood in Three Gorges. So, it is feasible to ahead of Three Gorges water storage scheme.5,Analyzed the effect of different reservoir group operating on river ecological flowThe basic ecological runoff in different sections of Yangtze River upstream was calculated by using the Low- flow percentage of average annual runoff method and the effect of different upstream reservoir groups operating on the minimum ecological flow was simulated by this model. The results showed that the runoff of river was increasing in dry season because the stored and regulated function of reservoir, which could guarantee the minimum basic ecological flow better.In addition, this paper discussed the impact of hydropower developing on river ecosystem and the question in further progress in the upper reaches of Yangtze River.