Operation of the Grand Ethiopian Renaissance Dam: Potential Risks and Mitigation Measures

Abstract

Several studies have simulated the Grand Ethiopian Renaissance Dam filling and operation but the optimum operation policy of the dam has not been fully investigated. This study presents a nonlinear optimization model for the operation of the Grand Ethiopian Renaissance Dam using natural historical inflow time series data (1912–2011) with an objective function that maximizes firm energy. The model results show that the mean hydropower production of the dam is about 14 650 GWh/y. The firm energy is found to be in the order of 12 900 GWh/y, which represents about 24.5% of dam installed hydropower capacity. It was found that the Grand Ethiopian Renaissance Dam operation, if used only for power production, will permanently reduce the Blue Nile flow to downstream countries by an average of 3.2%. It will also extend the downstream drought periods by 200%–300% compared to the time before dam construction. In order to ensure better downstream conditions, smaller dam active storage capacities were modeled and the results were analyzed. As a substantial mitigation measure, decreasing GERD live storage by 40% to reach 35 km3 yields 90% of the mean annual hydropower production of the announced design while better preserving the downstream water rights and conditions.