Integration of geochemical data to assess the groundwater quality in a carbonate aquifer in the southeast of Beni-Suef city, Egypt

Abstract

The Middle Eocene carbonate aquifer constitutes the major source of groundwater for the expansion of reclamation projects outside the Nile Valley southeast of Beni-Suef, Egypt. In the past few decades, groundwater abstraction from the Middle Eocene carbonate aquifer has increased, leading to the deterioration of groundwater quality. The current study combines geochemical methods and multivariate statistical analysis to assess the factors controlling the deterioration of groundwater quality in this aquifer. The results show that the total dissolved solids (TDS) varies between 263.7 and 4214 mg/l. The groundwater is dominantly of Na–Ca–Cl SO4 type. Various plots were used to assess processes such as carbonate and evaporite dissolution, silicates weathering and/or cation exchange controlling groundwater quality. Geochemical modelling with NETPATH indicates that recharge sources and mixing of groundwater within the aquifer result from occasional storms over the eastern watershed. These rainfall events account for ~32% of aquifer recharge, along with infiltration of Nile water in the west, which contributes ~36% of the recharge. The groundwater salinity is controlled by precipitation of calcite, dissolution of dolomite, gypsum and halite and ion exchange along the groundwater flow path. Multivariate statistical analysis highlights that the Ca, Na, Cl and SO4 ions control groundwater salinity within the aquifer through water-rock reactions and mixing of Nile water from the western side of the study area with subsurface recharge from mountainous areas in the eastern portion of the watershed. Integration of hydro-geochemical data and multivariate statistical analysis leads to better understanding of geochemical processes controlling regional groundwater quality in the Middle Eocene carbonate aquifer near Beni-Suef, Egypt and in areas with comparable conditions.