Hydrochemistry and environmental isotopes (18O, 2H, 3H, 3He/4He) of groundwater and floodwater in the great area of Hurghada, Eastern Desert of Egypt
Manal Wannous, C. Jahnke, Uwe Troeger, M. Falk, Florian Bauer
Abstract
Abstract Porous and fractured aquifers exist in the area of Hurghada, Eastern Desert of Egypt, whose recharge processes through the common flash floods are not identified. Hydrochemical parameters, stable isotopes 18 O, 2 H and tritium in floodwater and groundwater were applied in the area subject to study. Additionally, He isotopes were investigated in the deep wells in the faulted zone at the Abu Shaar Plateau. 3 H activity in all sampled points lies below the detection limit excluding a recent recharge component in groundwater. However, the hydrochemical ratios and the stable isotope signature confirm that the shallow wells and springs (Red Sea Hills group) are being recharged from modern precipitation. The hydrochemical parameters of the deep wells at the Abu Shaar Plateau (coastal plain group) confirm another origin for the ions rather than the modern precipitation. Together with the 18 O and 2 H values, the Br/Cl ratio of this group confirms the absence of seawater intrusion component and the role of the fault as a hydraulic barrier. These 18 O and 2 H values deviate from the GMWL confirming an evaporation effect and colder infiltration conditions and reveal strongly a possible mixing with the Nubian Sandstone in the region. The 3 He/ 4 He ratio confirms a mantle contribution of 2% from the total He components.