Evaluation of hydrogeochemical parameters of the ground water in El-Bahariya oasis, western desert, Egypt

EI-Bahariya Oasis is a natural topographic depression located in the heart of the Western Desert of Egypt. The Nubian sandstone aquifer represents the main water- bearing horizon. The hydrochemical characteristics of this aquifer are studied based on the chemical analysis of 125 groundwater samples collected from different sites. The salinity of the groundwater is relatively low (TDS vary from 108 to 632 ppm), as : well as the electric conductivity and total hardness. The recorded groundwater temperature values, from the Nubian sandstone aquifer range between 15 to 45°C. The variation in temperature may be due to structures or differences in drilling depths. The TDS, TH, major cations (Ca. +, Mg. +, Na+, and K+), and major anions ((HCO3)-,(SO4). and CI-) show general increasing from south to north. The hypothetical salt combinations in the studied area revealed the presence of different salts arranged in terms of their order predominance as NaCI, Ca(HCO3)2, MgSO4, Mg(HCO3)2, KCI, Na2SO4, NaHCO3, MgCI2 and CaSO4 where their average equivalent percentage are 31 %,20 %, 14 %, II %, 10 %,7%,3 %,2 % and 2 %, respectively. Water types are classified into chloride, sulphate, and bicarbonate which reflect that all collected groundwater samples lie in the range of normal chloride water, normal sulfate water, and under carbonate water classes, respectively. The Hydrochemical classification reflects a high concentration of sodium, chloride and bicarbonate ions, indicating that the dominant salts are sodium chloride, and sodium bicarbonate. Most of the samples having sodium-chloride surplus facies. Hydrochemical Parameters are used for identification of groundwater bodies, based on and confirmed by hydrogeochemical indicators such as ionic ratios. These ratios are helpful in detecting the previous hydrochemical processes affecting water quality such as mixing, leaching and ion exchange and could be used for comparison with other sources or reservoirs.