Insights from stable isotopes and hydrochemistry to the Quaternary groundwater system, south of the Ismailia canal, Egypt

Abstract

Summary Stable isotopic ratios of water (δ 18 O and δ 2 H) and major dissolved ions were analyzed from samples collected from the area south of the Ismailia canal, Egypt. This region has recently experienced rapid growth that has increased both surface and groundwater use. The data from the samples were used to identify recharge sources, and mixing and salinization processes in the groundwater system in this region. On the basis of the isotopic data and geochemical data, four end-members were defined representing, groundwater in a Quaternary aquifer, groundwater in a Miocene aquifer, water in the Ismailia canal, and wastewater from the 10th of Ramadan city. Several different mixing trends were recognized in the study area. As a consequence of mixing with groundwater in the Miocene aquifer, groundwater in the Quaternary aquifer was found to have depleted isotopic signatures and increased total dissolved ions (TDI) toward the south of the study area, near subsurface Miocene structural highs. Another mixing trend, consisting of, enriched isotopic ratios and lower TDI values toward the north in the Quaternary aquifer, indicated mixing with surface water, i.e., the Ismailia canal and freshwater ponds. A third trend of locally high TDI values together with depleted stable isotopic data, i.e., the Ramsis area and the vicinity of the well field, were interpreted to be due to excessive pumping for irrigation and reclamation activities, which in turn resulted in upconing of the deeper saline groundwater from the Miocene aquifer. Lastly, leakage from the wastewater ponds into the recharge process was suggested by considering chemical and isotopic signature of the Quaternary groundwater sample No. 31. These results strongly indicate the urgent need for monitoring, protection and remediation of the Quaternary aquifer in order to guarantee the sustainability of water resources in the study area. This work also illustrates the efficiency of using stable isotopes and major ion chemistry to improve our understanding of a flow system.