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Research Paper | Zoology | Ethiopia | Volume 3 Issue 6, June 2014 | Rating: 6.6 / 10

The Impact of Impoundment on Downstream Macroinvertebrate Communities at Koga Irrigation Dam; West Gojam; Ethiopia

AbileTeshita | Ayalew Wondie

Abstract: Despite its vital importance; river regulation affects downstream lotic environment and aquatic fauna. In this study; downstream effects of reservoir were evaluated using macroinvertebrate bio-assessment techniques. Macroinvertebrates community structure and physicochemical parameters were assessed at upstream and downstream sites relating to dam impact. Samples from four sites were collected using standard dip-net (500-m mesh size) and identified to family level. Rapid Bio-assessment Protocol-II metrics and scoring criteria was used to quantify changes in macroinvertebrate community structure and water quality. Downstream of reservoir; total abundance; Chironomidae abundance and Hilsenhoff Biotic Index values increased. However; richness; Ephemeroptera Plecoptera and Trichoptera taxa and Ephemeroptera abundance decreased. Trichoptera were absent from reservoir and downstream sites; but the number of gatherers and filter-feeder individuals were higher than reaches above the reservoir. Physicochemical parameters were significantly different (p < 0.05) among sites except temperature. A post-hoc test for Shannon Diversity Index indicated a significant difference (p < 0.05) between Site 1 and Site 4. Habitat and water quality changes have disrupted downstream continuum of macro-invertebrate communities. Generally; impoundments have profound impacts on macroinvertebrates within reservoir and below it as indicated by this study; therefore; needs an appropriate conservation measures.

Keywords: Downstream, Impoundment, Irrigation, Koga Dam, Macroinvertebrates

Edition: Volume 3 Issue 6, June 2014,

Pages: 544 - 552