The operation of cascade hydropower stations is accompanied by various target risks while exerting the comprehensive benefits of water resources. The systematic analysis of multi-risk interactions during the operation of cascade hydropower stations is helpful for improving the operational benefit of hydropower stations. However, the current hydropower operating model used for risk simulation cannot show the dynamic operation processes within the system, which may limit the popularization of the model. In addition, most existing studies define risk from the perspective of reliability and lack analyses of risk resilience and vulnerability. In this study, a system dynamics model of cascade hydropower stations is constructed, and the relationships among the multi-risk of the Xiluodu-Xiangjiaba (XLD-XJB) cascade hydropower stations are explored from the aspects of reliability, resilience and vulnerability. The results are as follows. (1) The system dynamics model can effectively simulate the dynamic process of system operation and can be used to study the performance risk changes in the operation process of hydropower stations. (2) The current operating rule leads to ecological risk and shipping risk in the system in the normal scenario. There are also power risks in wet and dry scenarios. (3) There is a contradiction between power risk and shipping risk. In addition, in the case of insufficient inflow, there is a contradiction between the reliability and vulnerability of power risk. (4) The regulation of ecological risk helps reduce shipping risk and power risk. Therefore, ecological outflow should be regarded as the minimum outflow requirement of cascade hydropower stations.

At present, the index of the effect evaluation of reservoir ecological operation cannot fully and systematically reflect the impact of the operation on the river ecosystem, and there is a lack of a complete and widely applicable index system. From the composition of river ecosystem, taking full account of the impact of water conservancy project on river ecosystem, this paper analyzes the effect of reservoir ecological operation from ecological environment benefit and social economic benefit, confirms the overall hierarchy of evaluation index system, and establishes the effect evaluation index system of reservoir ecological operation and the calculation method of each index. In this paper, the ecological operation of different objectives is analyzed, and evaluation indexes for water quantity, water quality, aquatic organisms and other operation objectives is established. The index system is applied to evaluate the ecological operation effect of four domestic fishes in Three Gorges reservoir. The results given in this paper are significance to the evaluation of reservoir ecological operation.