The area under consideration represents the middle part of El-Qaa plain, which lies in the southwestern part of Sinai Peninsula. The importance of El-Qaa plain lies in the fact that it is one of the most promising areas in Sinai Peninsula for integrated development due to its even surface, easy access, presence of groundwater resources and strategic location.
The main objective of the present study is to recognize in detail the hydrogeochemical characteristics of the Quaternary aquifer. The hydrogeochemical studies revealed that the total salinity of groundwater ranges from 373 to 4239ppm. However, 79% of the collected samples were found to have TDS less than 1000ppm. The salinity and ions concentrations (Na, Mg, Ca, Cl and SO4) were found to increase westward and southwestward. This can be interpreted as due to the leaching process of evaporites or mixing of meteoric and marine water at the southwestern part of the area. The increase in salinity takes place along the same directions where geoelectrical resistivity decreases. The relative increase in K ions in groundwater at the northeastern part of the area proves the leaching process of rock debris enriched with potash feldspar. The saturation indices of calcite, aragonite and dolomite minerals indicate sub-saturation and potential for dissolution at the recharge area, whereas they reflect super-saturation and precipitation of these minerals at the discharge area. The saturation index of gypsum in groundwater shows negative values throughout the aquifer, indicating the potential for dissolution of such mineral.
The majority of groundwater samples (75%) are characterized by the presence of Na2 SO4 water type of meteoric origin. The presence of MgCl2 and Ca Cl2 water types in 25% of water samples indicates the leaching and Base Exchange processes of meteoric water to marine sediments. Hydrochemical and geophysical means prove local seawater intrusion at the southwestern part of the investigated area. The groundwater at the eastern part of the area is chemically suitable for drinking and irrigation uses, as the salinity and ions concentration are below the international permissible limits, whereas at the western and southwestern parts the water is not suitable for these purposes.
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