Hydrogeochemical Processes Controlling the Water Chemistry of a Closed Saline Lake Located in Sahara Desert: Lake Qarun, Egypt

We present here the first detailed hydrogeochemical study about Lake Qarun. It is a closed, saline, and alkaline lake located in the North African Sahara Desert. It has no outflow except by evaporation. This lake is the deepest area in the Fayoum Depression with elevation 43 m below sea level. In th...

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Bibliographic Details
Published in:Aquatic geochemistry 2015-01, Vol.21 (1), p.31-57
Main Authors: Abdel Wahed, Mahmoud S. M, Mohamed, Essam A, El-Sayed, Mohamed I, M’nif, Adel, Sillanpää, Mika
Format: Article
Language:English
Subjects:
calcium
Chemistry
Deserts
drainage
drainage water
dry environmental conditions
Earth and Environmental Science
Earth Sciences
electrical conductivity
evaporation
Geochemistry
Hydrogeology
Hydrologic sciences
Hydrology/Water Resources
isotopes
Lakes
magnesium
Original Paper
oxygen
Saline water
salts
sea level
sodium
Water Quality/Water Pollution
water salinity
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Summary:We present here the first detailed hydrogeochemical study about Lake Qarun. It is a closed, saline, and alkaline lake located in the North African Sahara Desert. It has no outflow except by evaporation. This lake is the deepest area in the Fayoum Depression with elevation 43 m below sea level. In this area, Nile River is the main source of water and Lake Qarun acts as the main reservoir of all drainage waters. Along the flow path of water, the salinity of water increases with increasing proximity to Lake Qarun and the water chemistry has developed from Ca–Mg–HCO₃at head waters to Na–Cl–SO₄in low lands and in Lake Qarun. The main processes that control the water chemistry in the studied area are dissolution of soluble salts along with continuous evapoconcentration. The progressive evaporation of drainage water inflow has increased the concentrations of Na, Mg, Cl, and SO₄in Lake Qarun water, while Ca and HCO₃have been depleted through CaCO₃precipitation. This is confirmed by the application of Hardie and Eugster’s model parallel with a PHREEQC simulated evaporation model. Both models demonstrated that the evolution of lake water during evaporation should reach the final composition of “Na–Mg–SO₄–Cl.” Oxygen isotope (δ¹⁸O) values of the studied water samples showed a strong positive correlation with electrical conductivity values supporting the effect of evapoconcentration process on the evolution of the lake brine. This study presented an integrated geochemical approach that can help in understanding similar cases studies in arid environments.
ISSN:1380-6165
1573-1421
DOI:10.1007/s10498-015-9253-3