Assessing river ecological quality using benthic macroinvertebrates in the Hindu Kush-Himalayan region

We developed a system for the assessment of ecological condition for rivers in the lower mountains and lowlands of the Hindu Kush-Himalayan region (Pakistan, India, Nepal, Bhutan, and Bangladesh). We used benthic invertebrates collected from 198 rivers, located in five different ecoregions and covering degradation gradients; samples were taken twice (pre-monsoon and post-monsoon) applying a multi-habitat sampling procedure. Out of 38 environmental parameters, we constructed complex principal component analysis (PCA) gradients, separately for the stressors organic pollution, eutrophication, floodplain land use, and hydromorphological degradation. Correlation analysis between invertebrate metrics and environmental parameters revealed those biological metrics that are most responsive to river deterioration. Redundant metrics were deleted, and the most robust metrics were selected. The range of the index values under reference conditions was defined, and a five-class river quality system was generated.