Abstract:

In the upper and middle reaches of the Yangtze River main stream and major tributaries，largescale hydropower development is now being conducted.As the construction of these cascade reservoir groups，the flow and hydrothermal process being of ecological significance to natural river have been changed.These changes caused flow and water temperature averaged，and a few of river ecological environmental problems.According to attainable statistical data，taking Xiluodu and Xiangjiaba hydropower stations being built in the lower reaches of Jinsha River as examples，this paper analyzed the differences between natural and changed runoff，discussed the effect of averaging phenomenon of natural runoff and water temperature on the ecological habitat.It calculated the averaging effect of cascade reservoirs development on the natural runoff by using averaging coefficient λ.It also primarily analyzed how the cascade hydropower projects had averaged the water temperature process by taking k-ε water temperature model.At last，some measures to reduce the negative effects of cascade reservoir on the Yangtze River ecological environment were put forward.