Evaluation of Disturbance Zonation of Bagmati River System using Benthic Macroinvertebrates in the Kathmandu Valley, Nepal

The existence of Nepal's holy river, Bagmati, which flows through the core Kathmandu Valley has been menaced by many anthropogenic threats. It is necessary to identify how vulnerable it been. This research focuses on evaluation disturbance zonation analyze Bagmati River System’s spatial biological health. Benthic macroinvertebrates (BMIs) were used as indicators and sampled from upstream downstream using a multi-habitat sampling approach during post-monsoon period in 2021. Ganga System Biotic Score/Average Score per Taxa (GRSBIOS/ASPT) was assess river water quality. From 21 sites, total 5839 individual BMIs 51 Families 11 Orders recorded. Upstream accounted for more than 30% all families, making rich taxonomic preferences, steadily decreased midstream downstream. Facultative taxa widely distributed both midstream, but sensitive limited only. There are no signs that facultative existed fully dominated pollution-tolerant species. According classification, within Shivapuri Nagarjun National Park clean categorized Class I, whereas rivers boundaries protected area IV-V with few sites II III, indicating this stretch extremely polluted. Water resource managers should utilize study's findings restore water's quality indicators.