Community Features of Benthic Macroinvertebrates and Bioassessment of the Stretch of Bhagirathi River Impacted by Maneri Bhali Stage I Hydroelectric Project

Sandeep Kumar, Prakash Nautiyal


Benthic macroinvertebrate community was studied in a stretch of Bhagirathi River fragmented by Maneri-Bhalli stage I Hydroelectric project. Three stations were sampled at monthly intervals: one (S1) upstream of Maneri dam with natural hydrological regime, one (S2) in the 17 km fragmented stretch starved of its flow  downstream of the dam, and one (S3) abour 1 km downstream of M-B I power house. Mean water temperature increased while current velocity and DO decreased from S1 to S3. The benthic density decreased significantly in the downstream stations. Similar benthic assemblages in most of the months at S1 indicated the stable ecosystem while varying types of assemblages at S2 and S3 depict perturbed state. Biological Monitoring Working Party Score indicated moderately impacted to impacted and impacted to heavily polluted water quality at S2 and S3 respectively as compared to moderate water quality at S1. LIFE score indicated moderate to fast-flow conditions at S1, slow to moderate at S2 and varying flow conditions at S3 during lean season. CCA separated three stations with different characteristic taxa associated with different environmental variables. Current velocity, pH and dissolved oxygen explained maximum of the variance in assemblage in CCA plot. The study indicates that urgent measures are required to improve the ecological health and integrity of the stretch deprived of its natural hydrological regime.


: Bhagirathi river; Macroinvertebrate assemblage; BMWP; LIFE; CCA


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