An Eco-hydrology Method for Evaluating Ecological Suitability of Reservoir Discharge Flow on Downstream Ecosystem

The maintenance of healthy river ecosystem is based on appropriate hydrological conditions. The original hydrological rhythms of the river have been destroyed with the construction of reservoirs, which has brought a series of environmental problems. In order to restore the ecological environment of the river ecosystem, it is necessary to determine the appropriate ecological flow of the river. However, the completion of this work needs to assess the suitability of the flow process to the river ecosystem at first. Therefore, an eco-hydrology method based on fuzzy logic is proposed in this paper. It is considered that the appropriate ecological flow is an interval value, and the ecological suitability decreases when the flow is higher or lower than the inter value. Firstly, the range of appropriate ecological flow is calculated by hydrological statistical analysis method. Moreover, the method of similarity measure between vague sets is used to describe the close degree between the object flow process and the ideal one. Finally, the ecological suitability of reservoir discharge flow on downstream ecosystem is obtained by comprehensive evaluation of close degree. The method is applied to adaptive assessment of Three Gorges reservoir`s discharge flow on the downstream river ecosystem. Compared with the actual reservoir operation and related theoretical research results, it is found that the method can objectively analyze the ecological adaptability of the discharge flow on downstream ecosystem. The research results can provide theoretical basis for the determination of ecological flow and reservoir ecological operation.