The Three Gorges Project On Downstream River Eco-hydrological Impact Assessment Study

Dam construction,on one hand,for the human and social provides water supply,shipping,hydropower,irrigation,leisure and entertainment needs,promote the progress of human beings and society,has made great contribution for the economic development of the society.On the other hand,the construction of the dam breaks the stability and continuity of the river ecosystem.In this paper,combined with the National Natural Science Fund Project "consider fish habitat in the middle and lower reaches of the health of the research on the reservoir ecological operation" analyzed before and after the impoundment of the Three Gorges Project in the middle and lower reaches of the Yangtze River ecological changes in the hydrological regime,and three Gorges Dam impoundment effects on important fishes in the middle and lower reaches of the Yangtze River four everybody fish habitat conditions and suitability evaluation,for ecological operation of Three Gorges reservoir research and analysis provide the basis for laid the foundation.(1)In the downstream of the Three Gorges Reservoir hydrological control station at Yichang station as the research object,using linear tendency estimation method and Mann Kendall method,IHA/RVA analysis before and after the impoundment of the Three Gorges reservoir runoff,sediment and water temperature was used to analyze the trends and changes in the situation of and analysis results show that after the impoundment of the Three Gorge Reservoir in the middle and lower reaches of the Yangtze River hydrological regimes occurred moderate change and sediment regimes occurred changing the height and temperature regimes occurred moderate change.(2)According to the hydrological situation of 4 everybody fish spawning period,analyzes the four everybody fish spawning during the hydrological factors mean,range and standard deviation and rising duration,daily growth rate,.And in order to statistics of the four everybody fish spawning during the hydrological factors suitable range by the rules of the Sturge calculated water temperature elements of the optimal interval,statistics in different hydrological factors in the range of 4 everybody fish spawning times,and draw the frequency curve of the hydrological factors.Based on the quantitative analysis of hydrological changes in 5~7 months before and after the water storage of the Three Gorges project,it is concluded that the ecological hydrological target of spawning of four people before and after the water storage of the Three Gorges dam is analyzed.(3)By MIKE11 model constructed in the middle and lower reaches of the Yangtze River Yichang Zhicheng one-dimensional hydrodynamic model,and the model for the calibration and validation,results display,model simulation of flow and water level and calculated data are basically the same.This shows that the model is used to simulate the water dynamics of Yichang-Zhicheng section is reliable.For the lower reaches of the Yangtze River four big fish habitat for the habitat suitability study provide the basis and foundation.(4)Physical habitat simulation of the "four fish" spawning sites of the Three Gorges project before and after the water storage of the Three Gorges project was carried out by one dimensional physical habitat simulation model PHABSIM.Simulation results show that: before the Three Gorges Dam,the suitable environment for the "four fish" spawning period is 8000~150008)3/,the most suitable environmental flow rate is 110008)3/.After the Three Gorges Dam,the appropriate environmental flow of the four fish spawning period is 7500~125008)3/,the most suitable environmental flow is 100008)3/.(5)Finally,based on the analysis results of the ecological hydrological objectives and the simulation results of the four fish spawning period,the feasible measures for the protection of the four fish spawning sites were proposed.