Geochemical modeling of evaporation process in Lake Qarun, Egypt

Lake Qarun is an inland closed saline lake. It lies within the Fayoum Depression in the Western Desert of Egypt. Evaporation modeling has been carried out using PHREEQC to simulate the geochemical evolution of surface drainage waters inflow towards lake water. In the case of Lake Qarun, it is the first attempt to carry out such kind of modeling. Performance of this model helped to address the different sources of dissolved major ions to Lake Qarun and to identify the mechanisms control the lake's water chemistry. The model demonstrated that evaporation-crystallization process is the main mechanism controlling the evolution of lake water chemistry where major ions Na⁺, Mg²⁺, Cl^- and SO₄^2- have been built up in the lake by evaporation while Ca²⁺ and HCO₃^- are depleted by calcite precipitation. Moreover, the simulated model reproduced the real data observed in Lake Qarun except in the case of SO₄^2- which is in real more enriched in the lake than the model output. The additional source of SO₄^2- is reported to be from groundwater. The models result agreed well with the modified evolutionary Hardie and Eugster's scheme (1970) in which the final major composition of Lake Qarun water is Na-Mg-SO₄-Cl type. In future, the monitoring of Lake Qarun chemistry with detection of any other sources of elements and/or local reactions inside the lake can be detected by performing the simulated evaporation model reported by the present study.