22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Groundwater in the upper part of the eastern desert of Egypt: isotopes, infiltration, flow conditions, and chemical indicators

24 Sep 2019, 12:30
15m
Multiuse room 2 ()

Multiuse room 2

Oral Topic 5.3 - Advanced modelling tools for subsurface hydrology: from the vadose zone to deep environments Parallel

Speaker

Prof. Uwe Troeger (Technische Universität Berlin)

Description

Groundwater resource in the Eastern Desert of Egypt represents beside the surface water from the Nile a very important resource. In form of fracture springs, dug wells and relative deep wells groundwater serves as an only source in remote communities and also as a source for the desalinization process at the Red Sea touristic facilities. Eight locations in the area of Hurghada (south group), seven locations in the area of Elgouna (mountain group) and nine locations in the area of St. Anthony and St. Paul (north group) were sampled. Chemical composition, stable isotopes of 2H and 18O, tritium 3H were analyzed in all collected samples and additionally helium 3He and 4He was analyzed in the deep wells in the mountain group. The molar ratio Br/Cl indicates influence of evaporates in the north group and marine aerosols influence in the recharge area of the south and mountain group. The results show that groundwater in the south group and the mountain group needs a long time from the recharge area to springs and deep wells. From the recharge area to the springs and wells the residence time is over 60 years. In the mountain group 4He concentrations indicates groundwater ages of several 100 to 1000 years. Elevated temperatures and 3He/4He ratios show magmatic influence through the faults of the Red Sea Rift system.
In the northern part where the rainfall is more frequent, the concentration of tritium was between ≤ 0.5-1.5 TU and indicates the residence time between recharge area and springs is shorter and the fractures might be more open. The discharge of the St. Anthony spring, where 3H was less than the detection limit was recorded along a period of four months to investigate the hydraulic behavior of the aquifer. The measurements which were observed till now show a constant discharge rate indicating a regime of old water which takes long flow path from the recharge area to the spring area. On the other hand, the tritium concentration in the other springs which range from 0.5-1.5 TU indicate different independent flow paths which are probably connected with the fault system in the fractured rocks. The constant (even if low) discharge flow of most of the springs depends on a big buffer in the mountains with little change in the hydraulic head.
The stable isotopes 2 H and 18O indicate infiltration condition of extreme low humidity. The calculation of infiltration temperature depending on the stable isotopes and the noble gases reflects different values and imply warmer infiltration conditions rather than the one calculated from the stable isotopes.
The groundwater management in the Eastern Desert of Egypt must control that discharge from wells is in equilibrium with the rare recharge.

Primary authors

Dr Manal Wannous (Technische Universität Berlin) Prof. Uwe Troeger (Technische Universität Berlin) Mr Christoph Jahnke (State Office for Mining, Geology and Minerals Brandenburg) Mrs Marianne Falk (Museum of Natural History, Leibniz Institute for Evolution and Biodiversity Science)

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