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| Title: | IMPACT OF DAM COMPOSITION CONSTRUCTION ON PLANT AND DIVERSITY: THE CASE SPECIES OF KOGA IRRIGATION DAM, NORTHWESTERN ETHIOPIA |
| Authors: | Amare, Mekonnen |
| Advisors: | Dr. Hameed Sulaiman
Dr. Mekuria Argaw
Dr. Matthew McCartney |
| Keywords: | IRRIGATION DAM
NORTHWESTERN ETHIOPIA |
| Copyright: | Jan-2009 |
| Date Added: | 10-May-2012 |
| Publisher: | AAU |
| Abstract: | This study attempted to predict the likely impacts of a dam reservoir and flow regulation
on riparian plant composition and diversity. The study was conducted around the Koga
dam in the upper part of the Blue Nile basin in the northwestern part of Ethiopia. Floristic
composition and diversity in the riverine and adjacent sites of the river was studied. The
presence of plant species that would be affected by the storage of the Koga River water
and the modification of the downstream river flow regime were assessed. A total of 87
plots (3.48 ha) were laid, of which 57 (2.28 ha) were located in the upstream area, 17
(0.68 ha) in the vicinity of the reservoir, and 13 (0.52 ha) in the downstream area. A total
of 71 species were identified, of which 36.7 % were trees, 26.8 % shrubs, 18.3 % were
herbs, and 4.2 % climbers. About 59 species of vascular plants, belonging to 39 families
and 53 genera, were recorded upstream of the dam. 17 species comprising 15 families
and 17 genera were recorded in the area that will be flooded by the reservoir and 21
species comprising 15 families and 18 genera were recorded in the riparian zone
downstream of the dam. Comparison of species indicates that though there is no
significant difference between the three sites in terms of species density (p = 0.345). The
downstream region has more diverse and evenly distributed species compared to the
upstream and reservoir areas. There was no significant difference in terms of species
density and diversity in the adjacent and riverine parts of the upstream and downstream
areas. Most of the species in the area downstream of the dam including Dodonea
angustifolia, Ensete ventricosum, Syzygium guineense, Accacia spp., Combretum
adengonium, and Combretum molle, which were found exclusively in the riverine part,
are species that are normally found inhabiting riverine areas. This indicates that the
majority of the downstream vegetation prefers moisture rich substratum.
Flow history
was examined to analyze the likelihood of disturbance in scenarios with and without flow
regulation. The hydrological analysis shows that the dam may lead to reductions in
maximum daily discharges and flood frequency. Reductions in flood peaks and over-bank
flows could result in changes in species composition and diversity of plants growing in
water or water rich substratum below the dam. |
| URI: | http://hdl.handle.net/123456789/2861 |
| Appears in: | Thesis - Environmental Sciences
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