Evaluation of potential impact of Grand Ethiopian Renaissance Dam on Seawater Intrusion in the Nile Delta Aquifer

The Nile Delta aquifer in Egypt is one of the largest groundwater reservoirs worldwide. It contributes significantly to the water budget of the country and acts as the main source of freshwater apart from the Nile River. Due to excessive pumping to meet the increasing water demands, the seawater intrusion from the Mediterranean Sea has been triggered affecting the groundwater quality in the northern and middle zones of the Nile Delta aquifer. This paper investigates the possible adverse impact of reducing the flow in the Nile River due to the construction of the Grand Ethiopian Renaissance Dam on the Nile Delta aquifer and considers possible measures to adapt with such impacts. A numerical model is developed using SEAWAT to simulate the groundwater flow and solute transport considering the operation of the new dam. Two scenarios of filling the reservoir during 3 and 6 years were considered. The maximum groundwater drawdown in the middle Delta will reach 2.65 m under the conditions of scenario one and 1.4 m under the conditions of scenario two. Equi-concentration lines 1000 and 35,000 ppm would advance to a distance of 110.2 and 70.85 km, respectively, under the first scenario and 108.25 and 67.3 km, respectively, under the second scenario. Results indicated that filling the reservoir in 3 and 6 years would require reducing groundwater abstraction rates from the Nile Delta aquifer by 60 and 40%, respectively, to maintain the freshwater body in the Nile Delta aquifer.