Geochemical modeling of evaporation process in Lake Qarun, Egypt

• A first simulated geochemical model of evaporation process in Lake Qarun was done.
• The model helped to recognize the different sources of elements to Lake Qarun.
• The modeling data showed good agreements with the real data monitored in the lake.
• Evaporation–crystallization is the main mechanism controlling the lake chemistry.
• Monitoring of the lake chemistry became easier by using the current simulated model.

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 SO42− 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 SO42− which is in real more enriched in the lake than the model output. The additional source of SO42− 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.