HYDROPOWER DEVELOPMENT POTENTIAL AND OPTIMUM OPTION IN RIVER BASIN (IN TIGRAY, NORTH ETHIOPIA)

Abstract

The Ghiba river basin in Tigray regional state, North Ethiopia, has catchment area of 5163km2, the length of the main water course is 236.4km, with a total fall of 2030m. The average annual rainfall over the basin is 665.5mm and annual runoff volume of 1372milliom m3. There are eleven storage sites and 9 cascades planned (identified) in the river based on various established criteria: head, discharge (reservoir volume), geology, etc. The potential storage sites are: (1) Suluh, (2) Genfel-1, (3) Genfel-2, (4) Genfel-3, (5) Genfel-4, (6) Genfel-5, (7) Agulae, (8) Meskila-1, (9) Meskila-2, (10) Meskila- 3 and (11) Ghiba. All the cascades are located on the main rivers downstream of all the storage sites with the first cascade being a dam scheme. The objective of this study is to estimate hydropower potential at each site of interest as well as the whole basin, and to select an optional site based on the average power out put (Pm) at site that could reach selected demand centres. Hydropower development potential of the Ghiba basin is estimated. Hydrologic study was carried out, using existing discharge data recorded at the gauging stations available for the basin, and rainfall gauging stations in or nearby the basin. Due to significant missing data in rainfall and runoff, as well as poor matching of recorded periods, eleven years of monthly rainfall and concurrent runoff data was used. The missing records in rainfall data Hydropower Development Potential and Optimum Option In Ghiba River Basin v The water resources potential, at the ungauged sites (hydro sites) have been estimated by applying the relationships developed at gauge sites. To estimate the energy potential of the hydropower sites two analytical techniques were used The Flow Duration Curve (FDC) method and the Sequential Stream Flow Routing (SSR) method. Therefore, the total annual energy potential from FDC is170.27GWh and from the SSR analysis is 597 .179GWh. In addition, 822GWh of energy could be harnessed from the cascading systems. All the hydro sites are assumed to be connected to two near by grid centers at Wukro and Mekelle. Selection of an optimal site was done by ranking site: (1) based on limited criteria, topography, hydrology and proximity to load centers, (2) based on the power out puts reached the demand centers. Thus, the site with the highest rank would be the optimal site. This study thus concludes that, the total hydro-energy that could be harnessed from the whole basin is about 1419 GWh/ year and the optimal site, which should be implemented first, is the Ghiba storage hydro site.