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ENVIRONMENTAL CHANGE: IMAPCTS ON THE NILE – PART 2

This post follows on from the background information disclosed in the previous entry and focuses on the potential hydrological impacts of the Great Ethiopian Renaissance Dam (GERD) project on the River Nile. The data for this entry has been sourced mainly from the July 2021 scientific report by Eldardiry and Hossain in the Journal of Hydrology titled ‘A blueprint for adapting high Aswan dam operation in Egypt to challenges of filling and operation of the Grand Ethiopian Renaissance dam’ (Elidardiry & Hossain 2021). In this report, scientists have computed different dam and climatic scenarios against a baseline so that the hydrological impacts and shifts in the river flow regime of the Nile can be determined.

The Eldardiry and Hossain (2021) report found that during the drier summer months (June to August), the High Aswan Dam (HAD) in Egypt releases a significantly higher volume of water into the Nile Delta in order to irrigate the river and decrease water stress in the Upper Nile. During these summer months it is highly important that the flow volume of the Nile is maintained. If it is not maintained widespread drought in the Upper Nile is likely to occur, creating severe challenges for the agricultural industry in Egypt (Hasan and Tarhule 2020). As mentioned in the previous blog entry, the GERD is located on the Blue Nile which is the largest contributing source of the Nile and controls 53% of the water that feeds the HAD (Elidardiry & Hossain 2021). Therefore, if the GERD is filled too quickly, much of the water that would usually reach the HAD would be hindered, creating severe ecological and consequent fiscal issues further downstream.

Figure 1: Graph comparing the HAD water level under the three- and seven-year filling scenarios for the GERD. The red lines represent linear regression. The blue lines represent the mean water level. The thin lines below represent the scenario for a low preliminary water level. The thick lines above represent the scenario for a high preliminary water level.

Figure 1 reveals that if the GERD is filled in a short three-year period, the water level of the HAD is likely to change significantly beyond its usual seasonal variations. Therefore, if the filling of the GERD is mishandled in this way, there could be a major deficiency of water inflow into the HAD system. In this scenario, the volume of flow from the Blue Nile (where the GERD is situated) into the HAD is projected to decrease by approximately 30% (Hasan and Tarhule 2020), causing a 17% shortfall in total water flow into the lower Nile and HAD system (Elidardiry & Hossain 2021). This will cause significant water stress in the Nile Delta in Egypt and will consequently create a range of serious environmental issues such as desertification and drought. If the GERD is filled in a less abrupt 7-year period, however, it is projected that the likelihood of major shifts in the HAD water level will be marginal in comparison to the 3-year filling scenario (Elidardiry & Hossain 2021).

Figure 1. Ethiopia's Grand Renaissance Dam - in construction on the Blue Nile (source)

The interplay between these two hydrological systems highlights the highly complex cost-benefit examination that is needed to create successful hydrological systems that account for the environmental, economic and social variables of all parties involved (Goulden et al, 2010).

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