Hydrological Scenarios of the Renaissance Dam in Ethiopia and Its Hydro-Environmental Impact on the Nile Downstream

This paper investigates the hydrological scenarios of the Renaissance Dam being constructed on the Blue Nile in Ethiopia and the dam’s impact on the water balance downstream. Landsat 8 satellite images from 2013 were obtained and interpreted to identify locations for the Renaissance Dam and its saddle dam. Shuttle radar topography mission (SRTM) data were also obtained and processed to create a digital elevation model (DEM) for upstream areas. The DEM was analyzed to estimate water volumes that will fill the reservoir at various operational levels. The estimations were computed by filling the DEM to certain heights equivalent to the arbitrary barriers added to the original DEM at locations of the dams, and the stored volumes were computed from the resulting surface extent and spatially variable depths for the lakes. Different scenarios for dam height and resulting storage were proposed to estimate the resulting abstraction of the Blue Nile flows until completion of the project and the annual losses due to evaporation thereafter. The current site [506 m above sea level (asl)] for the Renaissance Dam allows the creation of a 100-m deep reservoir with a total storage of 17.5 km3; overflows will occur at the reservoir’s level (606 m asl) from its northwestern part into Rosaires downstream. Construction of the saddle dam to control the overflow area can allow the creation of a 180-m deep lake that stores up to 173 km3 in a lake that will cover 3,130 km2. The negative hydrological impacts of the Renaissance Dam will increase by creating the saddle dam because increasing the storage capacity can affect the strategic storage of the reservoirs in Egypt and Sudan. It is strongly recommended that an agreement be reached regarding the storage capacities and water supplies for all dams on the Nile to thoroughly satisfy all necessary demands.