Hydrogeochemical characteristics and age dating of groundwater in the Quaternary and Nubian aquifer systems in Wadi Qena, Eastern Desert, Egypt

The study area is a part of Wadi Qena, Eastern Desert. It is one of the largest promising areas for development in Upper Egypt. A new desert road was constructed to join Upper Egypt to the Red Sea, passing through the wadi. This accelerates the forms of development in the middle part of the wadi. The development focused on new cultivation farms established through the drilling of tens of wells to extract groundwater for land reclamation. The present study focused on the assessment of groundwater quality, its origin and suitability for drinking and agricultural purposes. This is made through the chemical analysis of a number of groundwater samples. A comparison of the water quality with the standard of drinking and irrigation water quality revealed that the water was not suitable for drinking purposes and could be used for high salt-tolerant crops. The evaluation of the saturation index (SI) of the water sample indicted that water was oversaturated with respect to iron minerals and undersaturated with carbonate minerals The analysis of the isotope data (δ¹⁸O and δ²H) of the water samples indicated that water samples of wells more than 500 m deep were mainly of Nubian sources (old water) and could be mixed by recharge from the Quaternary water. The other water samples showed that the origin of water was Quaternary, while the water samples collected from the shallow pits showed that water originated from the relatively fresh water. The study revealed that the old Nubian water was not renewable and should be managed properly to sustain the existing and proposed development.