Abstract: In the management of small and medium-sized rivers in urban plain areas of China, the main task is to strengthen the flood control function of rivers. However, the study on the ecological status of small and medium-sized rivers is not sufficient, leading to the incomplete identification of ecological problems of small and medium-sized rivers. Consequently, it is difficult to provide decision support for the restoration of small and mediumsized rivers. Here, we constructed a multi-index comprehensive evaluation system, including five elements, 11 indices and four evaluation grades of river water discharge, water quality, aquatic organisms, river morphology, and riparian zone in 11 typical small and medium-sized rivers in Beijing plain area. The index weight was determined using analytic hierarchy process. The matterelement comprehensive evaluation model was established to comprehensively evaluate the ecological status of 11 rivers. Theresults showed that the ecological status of six rivers such as Yongding River Diversion Canal and Yunchaojian River is poor (grade IV), and that of five rivers such as Liangshui River and Nansha River is at moderate level (grade II). Results of the diagnostic analysis showed that the hydrological discharge, water quality, and aquatic organisms of the rivers are poor as a whole, with water shortage, single flow pattern, and poor water quality in different degrees. The overall situation of river morphology and riparian zone is moderate and the artificial degree of some river sections is high, which affects the ecological conditions of the rivers. According to the specific problems of each river identified by the evaluation results, we proposed some suggestions for ecological restoration of small and medium-sized rivers in Beijing plain area.

Key words: small and medium-sized rivers, ecology, comprehensive evaluation, Beijing plain area.