Hydrogeochemical and isotopic study of the groundwater aquifers in Hodein basin, southeastern desert, Egypt

The Hodein basin forms the largest basin in the southeastern portion of the Eastern Desert of Egypt, draining toward the Red Sea. The water resources study of the basin is a very important challenge because the first thing to be attended to is water supply, especially; the basin is marked by dry conditions, experiencing low levels of rainfall and facing issues with desertification. Various records elements have been integrated, such as geology, geomorphology, hydrogeology, hydrogeochemistry, and the isotopes. Based on the geomorphology, the study area includes four geomorphological units: the Red Sea Mountains, Sandstone plateau, Inland tectonic depressions, in addition to the Piedmont and coastal plain. According to the geology, the area under investigation is covered by rock units from the Pre-Cambrian to recent. Groundwater in the area under investigation occurs in three aquifer systems: Quaternary, Upper Cretaceous, and Pre-Cambrian aquifers, where it is represented by 15 samples. The isotopic signature of the Upper Cretaceous indicated that the upper Cretaceous aquifer was recharged during the pluvial periods. Contrary to this, in the Pre-Cambrian aquifer the main recharging source is the rainfall. All the groundwater samples of the Pre-Cambrian and the Upper Cretaceous aquifers are suitable for drinking, according to the World Health Organization. In the Quaternary aquifer, the concentrations of TDS, Ca2+, Mg2+, Na+, SO42−, and C1− exceed the drinking water quality standard limits. The Upper Cretaceous and Pre-Cambrian groundwater samples are considered suitable for irrigation according to the US Salinity diagram for irrigation purposes.