HYDROPOWER DEVELOPMENT POTENTIAL AND OPTIMUM OPTION IN GHIBA 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 1334milliom m3. There are eleven storage sites and nine 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 river 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 the most promising 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 area. 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 The water resources potential at the ungauged sites (hydro sites) have been estimated by applying the relationships developed at the gauged sites. To estimate the energy potential of the hydropower sites two basic · -:·· . ·- approaches were used. The Flow Duration Curve (FDC) analysis and the Storage. Therefore, the total annual energy potential from FDC is170.27GWh and from the storage analysis is 418.126GWh. By combining storage and cascading systems at the main river, 1004GWh of energy could be harnessed All the hydro sites are assumed to be connected to two near by grid centers at Wukro and Mekelle. Selection of superior site. was done by ranking of sites: ( 1) based on I imited 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 most promising site. This study thus concludes that, the total hydro-energy that could be harnessed from the whole basin (storage + cascade) is a bout 1 00� GWh/ year and the most promising site, which should be implemented, first, with � I .•. average power out put of 32 MW, is the Ghiba storage hydro site.