Processes of water–rock interactions and their impacts upon the groundwater composition in Assiut area, Egypt: Applications of hydrogeochemical and multivariate analysis

Ion exchange, dissolution and precipitation represent the effective hydrogeochemical processes water-rock interactions. They play a great role in the form of changes in the hydrogeochemical composition of the groundwater in the Pleistocene, Plio-Pleistocene, and Eocene aquifers in Assiut area. Their impacts upon groundwater composition are investigated by applying the conventional hydrogeochemical tools and confirmed by the multivariate statistical treatments. The hydrogeochemical indices are used for investigating the actual changes in the chemical composition of the groundwater and their extents. Statistical multivariate analysis of the factors and principal components are used for investigating the effective loading of groundwater. They confirm the obtained results by applying the hydrogeochemical indices. The results indicate that dissolution and precipitation play the essential control on the groundwater composition in the Pleistocene aquifer around the Nile, while ion exchange is more effective in controlling the water composition in the Plio-Pleistocene and Eocene aquifers in Assiut area. The present work enables for assessment of the hydrogeochemical regime of the aquifer systems in Assiut area. It provides good understanding of natural and man-made factors which execute the processes of water-rock interactions and controlling the groundwater composition and suitability for different uses.