Health assessment of river ecosystem in the lower Jinsha River Basin using an improved comprehensive fuzzy evaluation...

To comprehensively evaluate the ecosystem health of eight major tributaries in the lower Jinsha River, an evaluation framework was established, incorporating five sub-criteria-morphological structural integrity, hydrological integrity, chemical integrity, biological integrity, and regional service sustainability-encompassing 16 indicators. A multilevel fuzzy comprehensive evaluation, integrating the Analytic Hierarchy Process (AHP), the entropy weight method, and the maximum membership principle, was employed in the Yibin section of the lower Jinsha River. This approach accommodates the inherent fuzziness and uncertainty in indicator classification, thereby avoiding biases introduced by rigid classification thresholds. The basin's overall health was classified as healthy, with a mean River Health Index of 80.73 (SD = 2.91). However, significant spatiotemporal heterogeneity was observed: morphological structural integrity scored relatively low (mean = 69.98, SD = 9.27), whereas chemical integrity was notably high (mean = 91.50, SD = 5.32). Uncertainty analysis supported the robustness of the overall assessment (95% CI: 78.28-83.18), though considerable variability was detected among certain sub-criteria, reflecting spatial disparities in anthropogenic pressures and biodiversity. Further analysis identified impaired river connectivity, agricultural non-point source pollution, and invasive species as the principal drivers of ecosystem health. In response, the following management strategies are proposed: implementation of sewage diversion and interception projects to mitigate point and non-point source pollution, development of a dynamic water-quality monitoring and early-warning system, and application of bioremediation technologies to enhance channel self-purification capacity and ecological functioning.