ASSESSMENT OF THE RUN OF THE RIVER HYDROPOWER POTENTIAL AT THE DOWN STREAM OF KOKA DAM AND FORECASTING THE LEVEL OF FLOODING AT SELECTED SITE (CASE STUDY OF AWASH RIVER BASIN, ETHIOPIA)

Abstract

Energy demand is increasing exponentially. This is because of rapid population growth, urbanization, the higher standards of living, industrial and agricultural expansion. Nevertheless, the available energy supply is not reliable due to sedimentation problem. So, it is advisable to use the nearby available natural resources (i.e. river and suitable topography) for potential assessments without adverse effect to cope with increasing and diversified energy demands. This study aims to investigate the assessment of river run of hydropower potential at 50km downstream of Koka Dam. To achieve the goal, Stream flow data were collected from 1991-2016 and height information was quantified from contour map and 3D spatial analyst tool in ArcGIS. Initially, the study was identified three possible potential sites and from these sites; site one was selected as the most prioritized site using MCDA method. The study included the Flood level forecasting at mostly prioritized site for further precaution using HEC-GeoRAS for preprocessing of geometric data and HEC-RAS for post processing of hydraulic modeling. Following the aforementioned model, methods and data the study computed the theoretical power at site one was (8981kw and 4197kw), technical power was (6960kw and 3253kw) and the annual energy output was (60.9GWh/year and 28GWh/year) are the maximum and minimum power at Q30 and Q95 respectively. The most preferred site had dependable flow of 19.71m3/s and is occur 95% of the year and the design flow was 42.17m3/s and is occur 30% of the year. The flood inundation area and the maximum flood depth at mostly prioritized river station 1100 where the study starts head measurement (i.e. upstream full reservoir level) and around 1km upstream of R.S. 1100 (i.e. at R.S.2050) were (145.79m 2 , 4.96m) and (204.09m 2 , 5.62m) respectively for 100 year return period. The validation of spatial information for site one tested were 0.71 for RMSE and hydraulic model performance for R.S.1100 and R.S.2050 were (0.7, -8.29 and 0.97) and (0.83, 5.92 and 0.96) for ENS, PBIAS and R for return period of 100 year and show the applicability of the model was good. To encapsulate we can get the site at 50km downstream of Koka Dam that have the capacity to produce annual energy of 60.9GWh/year. Consequently, it is possible to minimize the problem of highly increased and diversified electric demands at the target area. Hence, it is recommended that the government at national as well as local level or any other agency should look over it in detail and finding to implement thorough investigation of the area