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Abstract
Amira Mohamed Reda, (2022). “Hydrogeochemistry and Modeling for
Groundwater – Wadi Qena – Eastern Desert – Egypt”. Faculty of Science,
Helwan University.
The Qena basin (16,000 km2
) represents one of the largest dry valleys in the
arid Eastern Desert of Egypt. Groundwater resources in this watershed are
scarce due to limited recharge from annual precipitation. Hydrogeochemistry
and environmentally stable isotopes were utilized to determine the main
sources of recharge and geochemical processes affecting groundwater quality.
The studied basin comprises three main groundwater aquifers: the Quaternary
aquifer, the Post-Nubian aquifer (PNA) of the Paleocene-Eocene age, and the
Nubian Sandstone aquifer (NSA) of the Lower Cretaceous age. Groundwater
types vary from fresh to brackish groundwater. The groundwater salinity of
the Quaternary aquifer ranges from 426 to 9975 mg/L with an average of 3191
mg/L, the PNA’s groundwater salinity ranges from 1134 to 6969 mg/L with
an average of 3760 mg/L, and the NSA’s groundwater salinity ranges from
1663 to 1737 mg/L with an average of 1692 mg/L. The NSA’s groundwater is
relatively depleted of stable isotopes’ signatures (ranges: δ18O from −9‰ to
−4.81‰; δ2H from −71‰ to −33.22‰), whereas the Quaternary aquifer’s
groundwater is relatively enriched (ranges: δ18O from −5.51 to +4.70‰; δ2H
from −40.87 to +37.10‰). Geochemical and isotopic investigations reveal
that the NSA groundwater is a paleo-water recharged in a cooler climate.
In contrast, the upstream Quaternary groundwater receives considerable
recharge from recent meteoric water and upward leakage from the artesian
NSA. The downstream Quaternary aquifer in the delta of the Qena basin is
composed of original groundwater mixed with recharge from the River Nile.
Isotopic analysis confirms that the PNA’s groundwater recharge (ranges: δ18O
from −5.90 to −0.10; δ2H −58.21 to −7.10‰) mainly originates from upward