A multidimensional ecological health assessment method in plateau rivers

River ecosystem health assessment is essential for sustainable water resource management, particularly in ecologically sensitive regions such as the Qinghai–Tibet Plateau. This study proposes a multidimensional ecological health assessment method based on physical, chemical, and biological dimensions to evaluate the ecological health of plateau rivers, using the upper and middle reaches of the Nujiang River catchment as a case study. Subsequently, a multidimensional ecological health assessment was conducted using the water quality index (WQI), heavy metal enrichment factor (ER) and benthic index of biotic integrity (B-IBI). Results indicate that the study area exhibits overall clean water quality with good overall water quality; sediment shows significant pollution from Mn and Pb, while other heavy metals exhibit moderate or slight pollution, with distinct temporal variation patterns. The B-IBI assessments showed that the studied river catchments is generally in a healthy ecological state, with 55.3% of sites rated as Excellent or Good. However, degradation was observed in midstream gorge areas and densely populated regions. Notably, no significant correlation was found among WQI, ER, and B-IBI results, highlighting the necessity of multidimensional ecological assessment. The proposed multidimensional ecological health assessment method offers a robust, objective, and transferable tool for ecological health evaluation in plateau river systems. • Multidimensional ecological health assessment for plateau rivers: integrating physical-chemical-biological indicators. • 93.7% of the surface water samples are in a “clean water” state. • Significant pollution exists for Mn and Pb, while other heavy metals (excluding Hg) show moderate pollution. • 55.3% of the sites had healthy ecological conditions (Excellent or Good).