Stream regulation: Variations in the density, composition and diversity of benthic macroinvertebrates occurring in the up and downstream sections of the impounded zone of the river Ganga in the foothills

摘要

Variations in the density, composition and diversity of the benthic macroinvertebrates were studied in the up and downstream sections of the impounded zones (Veerbhadra and Bhimgoda barrage) of the river Ganga in the foothills. In these sections differences in the benthic density were found to be insignificant (P<0.05). The sections differed in terms of composition and relative abundance of different taxa. The regulated stretch was found to harbour only Ephemerotera, Diptera, Trichoptera and Mollusca. Plecoterans were absent while Coleopterans were very rare in the regulated stretch as compared with the upstream pristine stretch studied earlier. The predominance of Heptageniidae and fragmented occurrence exhibited by other taxa are attributed to fluctuations in the flow regimes and loss of substrate diversity. The diversity of benthic community was lower in upstream sections being least in UVB (0.1348 — 1.1319). However, the differences were not significant. Similarity index indi-cated lack of similarity in the community at impounded locations.