Impact of the Grand Ethiopian Renaissance Dam (GERD) on Gezira Groundwater, Sudan

Abstract

The Gezira area has one of the most massive agricultural projects in the world. Groundwater is one of the most critical water resources in Sudan. About 80% of the people in Sudan depend mainly on groundwater. The Grand Ethiopian Renaissance Dam (GERD) is under construction on the Blue Nile at 15 km from the Sudan’s border, creating a reservoir of 74 km3. The environmental studies of the GERD effect on Egypt and Sudan are vague. The present paper deals with the assessment of groundwater in Gezira using geochemical analysis, stable isotopes, remote sensing, and GIS. The impact of land use/land cover on groundwater quality was studied using supervised classification techniques of multidates (multitemporal) satellite images. Also, it covers the investigation of water interaction between the surface water and Gezira groundwater aquifer. The surface water includes the White Nile and the Blue Nile that will be controlled entirely by the GERD. If there is a direct recharge from the Blue Nile, the GERD will increase the recharge because it will keep the water in the Blue Nile always at a high level all year, resulting in increasing the seepage to the aquifer. The agriculture will also be all over the year, so water infiltration to groundwater will be increased. The major ions, nitrate, ammonium, heavy metals, and stable isotopes (δD and δ18O) were measured to achieve these goals. The results of hydrochemical data were mapped using ArcGIS 10.3 and Aquachem software. The results indicated that there are no any evidence for the groundwater pollution resulted from the anthropogenic activities in the study area. Although agricultural projects have been started with full capacity, since 1960, the pollution traces were not detected. The stable isotopes of the 2H and 18O confirmed that the groundwater of the Nubian aquifer in the study area is recharged from the Blue Nile through the Gezira aquifer. Moreover, away from the Blue Nile, the influence of recharge is negligible, but the water of the Nubian aquifer still mixed with water of heavy isotopic composition. The chemical and physical characteristics of groundwater indicate that the GERD will increase the recharge because it will keep the water in the Blue Nile always at a high level all year, resulting in increasing the seepage to the aquifer. The agriculture in Sudan will also be all over the year, so water infiltration to groundwater will be increased.