No abstract

l Heiz area, a part of El-Bahariya Oasis, is distinguished by nonrenewable Nubian Sandstone Aquifer System (NSAS) that has a large amount of fresh water. 16 groundwater samples were collected from multilayered Nubian Sandstone Aquifer (NSA) for physical, chemical and isotopic analysis. The average values of the total dissolved solids (TDS) indicated fresh water types with values that ranged between 149 mg/l and 544 mg/l with an average of 257 mg/l. However, the measured pH values showed relatively acidic water with values that ranged from 5.77 to 6.74 and averaged on 6.3. The measured temperature degrees varied greatly with values ranged from 26.3 o C to 46.4 o C. The stable isotopic content is also variable, where it ranged from -9.84 to -2.28 (on average -6.0) and from -79.90 to -48.63 (on average -62.20) for δ 18 O and D, respectively. The wide range in stable isotope values indicates variable geochemical processes. The results of some trace elements such as iron and manganese showed values that exceeded the permissible limit for drinking purposes in some of the studied groundwater samples. PHREEQC program was applied to calculate the saturation indices of some selected minerals such as anhydrite, gypsum halite, calcite, dolomite, siderite and hematite to identify the role of the geochemical process on groundwater evolution. The factor analysis suggested three factors that impacted groundwater quality, including the evaporation and/or geothermal, rock-water interaction, and ion exchange processes. In general, the application of the aforementioned methods showed that the groundwater extracted from the Nubian Sandstone Aquifer (NSA) is primarily recharged from the paleo-water, which was subjected to evaporation, geothermal, leaching, and dissolution processes.