A study on a river health assessment method based on ecological flow

•This study presents a new method for calculating ecological flow that is more accurate and reliable than the traditional method.•This study presents a new river health assessment method that can be applied to assess the health status of the river.•The river health assessment method presented in this study, can be used in watershed management, which provides a scientific and efficient method for management. In order to facilitate watershed management, we developed an expansive river health assessment method based on ecological flow hydrology method in this study that estimates the ecological flow of a river by using a probability density curve combined with six levels of river flow in different states of a river ecosystem. We apply the above method to a river health assessment in the middle reaches of the Yangtze River. The results show that the ecological flow calculated by this method is more accurate than that of the traditional hydrology method and the fish spawning water demand method and can better describe the actual demand of river ecosystems to flow; thus, this method is reasonable for evaluating river health. Moreover, the river health assessment method described in this study covers the different health states of river ecosystems, including all intervals of river flow, and takes into account the influences of extreme flow events and the uneven distribution of flow during the year. It is a reasonable river health assessment method that can evaluate river health status systematically, comprehensively and accurately. Moreover, we demonstrate the feasibility of this method in watershed management. The results show that this method can provide a scientific decision-making basis for river health management in actual watershed management.