Macroinvetebrate Assemblages as Indicators of Water Quality of the West Seti River, Bajhang, Nepal

Abstract

Water quality of the West Seti River, a tributary of the Karnali in West Nepal was assessed using macroinvertebrates as bioindicators. The main objective of the study was to assess the ecological water quality of the West Seti River and to generate a baseline data on macroinvertebrate assemblages. The sampling was conducted during December 2015 and a total of 11 sampling sites were selected from the West Seti River and its tributaries. Qualitative samples of macroinvertebrates were collected from different habitats. Selected physico-chemical parameters such as pH and temperature were estimated on-site. Dissolved oxygen (DO) was estimated by Winkler's method. The macroinvertebrate samples were enumerated and identified up to Family level following standard literature. Chi-square test was performed to see whether macroinvertebrate taxa varied significantly along the altitudinal gradient and between the West Seti River and its tributaries. An ecological assessment tool Nepalese Biotic Score/ Average Score Per Taxon (NEPBIOS/ASPT) was applied to assess the water quality of the sampling sites. The pH value ranged from 7.9 to 8.7 indicating the alkaline nature of the river. A total of 1666 individuals belonging to 34 Families and 7 Orders of macro-invertebrates were observed. The highest diversity of the macroinvertebrate taxa was observed at site T5 with nineteen Families whereas the lowest taxa diversity was observed at R3 with only five Families. The variation in macroinvertebrate assemblages between the sub-tropical and temperate zones; and the West Seti River and its tributaries were not significant. NEPBIOS/ASPT revealed a score of Water Quality Class of III-IV at Site R3 indicating that the site was polluted. This site was characterized by the abundance of red Chironomids which are considered as the indicators of organic pollution.

Evaluation of multiple water quality indices for irrigation purposes for the Bheri and Babai River systems, Nepal

“…This indicates a normal range and is suitable for irrigation (Ayers & Westcot, 1994). Alkaline pH has been reported in other Himalayan rivers as well (Paudyal et al, 2016 b;Seth et al, 2016;Matangulu et al, 2017;Sharma et al, 2020). pH values ranging from 6.5 to 8.40 are considered good for irrigation.…”

Benthic macroinvertebrates assemblages of glacial-fed (Bheri) and rain-fed (Babai) rivers in western Nepal in the wake of proposed inter-basin water transfer

“…The non-insect fauna in the Babai system were represented by 10 families with four Mollusca taxa; one each of Malacostraca and Arachnida taxa and; four Annelida taxa. A number of studies in Nepal have reported insects as dominant macroinvertebrates in streams and rivers ( Matangulu et al 2017 , Rai et al 2019 , Shah et al 2020 , Gurung et al 2021 ). Non-insect fauna, particularly Mollusca , have been reported in lowland water bodies ( Nesemann and Sharma 2005 ) as opposed to mid-hill rivers and streams.…”

Freshwater biodiversity in western Nepal: A review

“…Unfortunately, current knowledge of benthic macroinvertebrates in the freshwater ecosystem in Nepal is still very fragmentary (Brewin & Ormrod 1994;Suren 1994;Manel et al 2000). In western Nepal Himalaya, only a few studies have assessed richness, diversity, and relationship with environmental variables using benthic macroinvertebrate communities as the model organisms (Shah 2020;Matangulu et al 2017;Suren 1994;Manel et al 2000). Suren (1994) examined the relationship of elevation and the land-use changes on the richness and composition of macroinvertebrates in the Karnali River.…”

“…and Lamellidens marginalis. A study of the macroinvertebrates in West Seti river basin recorded 34 Families of the macroinvertebrates belonging to 7 Orders (Matangulu et al 2017). Similarly, Shah et al (2020b) reported 128 taxa of macroinvertebrates belonging to 84 families and 22 orders from the Karnali River Basin.…”