Water ecosystem health evaluation and influencing factors analysis of AN urban river: A case study at Beiyunhe River, Northern China

The Beiyunhe River is a typical urban river in northern China, and the health status of its ecosystem is degraded by urbanization. To evaluate this health status, a survey was performed throughout the basin. Thirteen indexes were selected to construct an ecosystem health evaluation system, and a composite index method was used to quantify the Beiyunhe River’s ecosystem health. Redundancy analysis (RDA) was used to detect the key factors influencing ecosystem health. The results showed that the river’s health status was mostly moderate: of the 38 surveyed points, the health status of 10% was Good, 47% was Average, 40% was Poor, and 3% was Very Poor. The upper and middle reaches were in better health than the lower reaches, and the main stream health was better than the tributaries. Among the tributaries, Bahe River (upper and middle reaches) had the best health status, whereas Fenghe River (lower reaches) had the worst. RDA showed that the ratio of hardening of the river, number of water-blocking structures (gates and dams), and population density in the catchment area were the key factors affecting the health of the Beiyunhe River ecosystem. This study can be used as a reference for the evaluation of the health of urban river ecosystems.