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Variation in Macro Invertebrates Communities in Streams in Above and Below Dam: A Case of Kulekhani Dam, Makawanpur, Nepal

Manisha Ghimire*, Tejendra Regmi, Rajeshwor Shrestha

Damming of rivers disrupts hydrological cycle and negatively impacts the structure, function of riparian ecosystems and alters the abundance and composition of biological conditions in the aquatic environment. Macroinvertebrates play important role in stream ecosystem function and research related on their responses to dam construction is lacking. This study was to assess the variation in Benthic Macro Invertebrates (BMIs) communities in streams in above and below Kulekhani Dam in relation to physico-chemical parameters. Multi habitat qualitative samplings for four sites were conducted with 100 m stretch in each study river section during winter season, 2019. The Ganga River System biotic (GRS bios) score method was used for the biological water quality assessment. High value of DO, pH with fewer temps, TDS and EC was found above the dam while inversed below the dam. The water quality was high in the site SA02 with Average Score Per Taxa (ASPT) value 6.1 (i.e. River Water Quality Status (RWQS)-I) which is slightly polluted above the dam site and immediate site SB01 was found to be critically polluted with ASPT value 5.4 (i.e. RWQS-III) which was recovered in the reference site SB02 with ASPT value 6 (i.e. RWQS-I). A total of 25 families and 8 orders of aquatic BMIs were identified in different sampling sites. The taxa richness was found higher above the dam and lower in below sites. Whereas, abundance of macro-invertebrates was found higher above the dam and lower below the dam. Percentage of EPT taxa and abundance was decreased below the dam and found higher above the dam respectively. The SA01 showed the high concentration of Shannon and Simpson’s diversity index.