Assessment of plain river ecosystem function based on improved gray system model and analytic hierarchy process for the Fuyang River, Haihe River Basin, China

•A conceptual model for the plain river ecosystem function in semiarid area and interfered by intensive human activities was developed.•The gray system model was improved.•Main functions of plain river ecosystem and the corresponding factors that determine the plain river ecosystem function were proposed.

A comprehensive conceptual model for assessment of river ecosystem function and a multilevel indicator system by including the hydrology and water resources, water environment, physical habitat, as well as biotic structure for the plain river ecosystem function of the Haihe River Basin were constructed in this research. The indicator weights were determined by analytic hierarchy process and the improved gray system model was used to assess the ecosystem function of the Fuyang River in the Haihe River Basin. The elements that determine the plain river ecosystem function are physical habitat, hydrology and water resources, biotic structure and water environment. The maximum membership degree of gray incidence of ecosystem function for the Fuyang River is 0.7228, indicating that ecosystem function of the Fuyang River is at a critical state; comprehensive restoration including water quantity recovery and water quality improvement should be introduced to improve the ecosystem function of the Fuyang River.