ASSESSMENT AND EVALUATION OF HYDROPOWER POTENTIAL SITES USING GIS AND HYDROLOGICAL MODELING TECHNIQUES: A CASE STUDY OF UPPER NYABARONGO CATCHMENT, RWANDA

Abstract

The renewable sources of energy plays the most important role in socio-econom development in Rwanda that have a favorable topographic condition because of hi variation of elevation make the country one of the richest nations in terms of hydropow potential and the study was done on Upper Nyabarongo that is an elongated catchment ar sloping down from south to north. The assessment and evaluation of the hydropower potential available in all the sub basi in the Upper Nyabarongo catchment was completed. Potential head drops were calculat from a digital elevation model with a 1-arc-second resolution (approximately 30 resolution at equator) where head drops greater or equal to 5 m were selected. The rainf data used come from eight rainfall gages. The potential hydropower of all streams w estimated as 67 megawatts using design discharges corresponding to 45th percentile flo with the hydraulic head. Within the study area there were 8 rainfall gages, one minimu and maximum temperature gage and one stream flow gages with long-term data recor To estimate the daily discharges of the reaches are derived from hydrologic and clima data using HEC-HMS model that divided the catchment into 8sub- basins and 14 riv reaches was used. Stream reaches, upstream areas, and mean annual rainfall were estimat using GIS techniques. The overall simulated stream flows were significantly correlated with the observed flow with Nash efficiency of 0.905 and volume percentage difference of 2.62 and the accurac of the flows estimated with the HEC-HMS Model was validated with Nash efficiency o 0.95.The results indicate that the potential hydropower is mostly concentrated near Muhanga and Ngororero Districts and Sub basins W780 and W580 showed the highest potential. In addition to the hydropower estimates, potential hydropower estimates with flow rates with exceedance probabilities of 45 percent, 60 percent, and 95 percent were made. Therefore, this study has shown the limitations and potentialities in giving support to th mid to long term planning of the energy sector in Rwanda.