Abstract:  

After the impoundment of Three Gorges Reservoir, aquatic environment of the tributaries in this reservoir has been subject to algal blooms.  The ecological operation can change the hydrodynamic condition of the reservoir tributaries, and help to control algal blooms. A nested prediction model of reservoir operation with ecological constraint was proposed. The back propagation neural network algorithm(BNN) was used to construct a model for forecasting the algal biomass in the tributaries. The input variables of this prediction model are water level(H), water level frequency conversion(HF) and water level Range(HR).The output variable is chlorophyll concentration. The prediction model is embedded into the reservoir operation model and constructing the ecological operation model which considering the water blooms in the tributaries, then using the discrete dynamic programming(DDDP) to solve the ecological operation model. The results show that the correlation coefficient between the observation and simulation calculated by the prediction model is R = 0.853 6. That means this model can predict the chlorophyll concentration well. Under the condition of 100% control guarantee rate for extreme water bloom. The calculation shows that the ecological operation power generation is 0.89% less than the real power operation. Carrying out the ecological operation in the Three Gorges Reservoir can effectively control algal blooms in the tributary without losing the overall economic benefits.