Impact of Climate Change on the Hydrology and Hydropower in the Upper Blue Nile Basin

Abstract:

The Upper Blue Nile (UBN) basin in Ethiopia is referred to as the “Water Tower” of northeastern Africa for its contribution of about 60% of the discharge to the main Nile river. The highlands of the UBN have the potential for significant hydropower and irrigation, with spatially varying temperature and precipitation over the basin. In order to meet the demand of the increasing population for electricity and water Ethiopian government has started the construction of the Grand Ethiopian Renaissance Dam (GERD) in 2011 at the outlet of the UBN, which has arisen controversies of water share among the three riparian countries, Ethiopia, Sudan, and Egypt.

In this study, we deployed a physically-based hydrological model (Coupled Routing and Excess SToarage; CREST) to investigate the impact of future climate projection on the basin hydrology. CREST was tested in a prior study and was demonstrated its good performance in terms of ET and discharge simulation and that the modeling framework can be applied to predict reservoir inflow volume (Lazin et al., 2020). We used sub-daily resolution climate projection data (3 hourly by 50 km) from Rossby Centre regional atmospheric model, RCA4, which is forced by the Model for Interdisciplinary Research On Climate (MIROC5) global circulation model. We used 1981-2010 as the baseline period and analyzed future projections within the three windows (2011-2040, 2041-2070, and 2071-2100). Compared to the baseline period, climate projections in UBN exhibit an around +9% increment of the annual total precipitation and 1.8 to 4.2 overall increment of temperature As a result, the annual flow at Eldiem outlet of UBN (close to the GERD) could increase between 24% and 63%. Considering different annual release scenarios to the downstream countries and the simulated projected inflow to the GERD, we estimated the probable filling time of the reservoir and analyzed the hydropower generation of the dam in the various future time windows. The findings of the study will help understand how the dam operation can be planned for future climate extremes as well as the negotiation among the three counties regarding the release amounts.

Acknowledgment: This material is based upon work supported by the National Science Foundation under Grant No. 1545874.

Reference:

Lazin, R., Shen, X., Koukoula, M., Anagnostou, E., 2020. Evaluation of the Hyper-resolution Model Derived Water Budget Components over the Upper Blue Nile Basin. J. Hydrol. 590, 125231. https://doi.org/10.1016/j.jhydrol.2020.125231