The role of Renaissance dam in reducing hydrological extremes in the Upper Blue Nile Basin: Current and future climate scenarios

Climate change poses a great threat to society through its effects on extreme hydrological events (floods and droughts) and the sustainable development. Coping with climate change requires a better awareness of the possible impacts to inform climate adaptation strategies. In this study, we investigated the climate projections from two contrasting GCMs (wet scenario from MIROC5 and dry scenario from CSIRO) and quantified the possible outcomes in terms of hydrological components of the Upper Blue Nile Basin (UBNB). These two climate projection scenarios show that the overall precipitation change in the early (2011-2040), mid (2041-2070), and late century (2071-2100) over the UBNB may vary from -18.3 % to + 13.6 % of the baseline annual precipitation of 1350 mm. The hydrological simulations over the basin from our study showed that evapotranspiration may vary between -13.7 % and + 12.1 % of the average annual total actual ET of 710 mm, and the flow at the basin outlet may range between -40.7 % and + 30.8 % of the mean annual total flow volume of 45 billion cubic meters. As a result, the wet projection exhibited more frequent floods while the dry projection showed severe droughts, specifically in the late century. We also examined the role of the Grand Ethiopian Renaissance Dam (GERD), designed for hydropower generation, in moderating these potential future climate hydrological extremes. Our findings indicate that GERD operations can help reduce downstream flood and drought severity by managing flow releases. Thus, this study illustrates the most possible extreme hydrological events in the UBNB due to climate change and demonstrates the degree to which GERD operations can help reduce the impact of these extremes downstream. The findings and data generated in this study will aid understanding the importance of sustainable water management and reservoir operation that caters to both hydropower generation, and recurring floods and droughts.

Automated summary

Climate change affects extreme hydrological events in the Upper Blue Nile Basin, with wet scenarios leading to frequent floods and dry scenarios causing severe droughts. The operations of the Grand Ethiopian Renaissance Dam can help mitigate the impacts of these extremes downstream.