This study deals with groundwater quality of the Jabal Hafit area in the southeastern part of the UAE. In order to assess groundwater in the study area, 21 samples were collected from groundwater wells. Of these, 12 samples were analyzed for stable isotopes of δD and δ¹⁸O. The results showed that the sequence of cations dominance in groundwater in the study area is: Na⁺> Ca²⁺> Mg⁺²> K⁺, while the sequence of anions dominance is: Cl^-> SO₄^2-> HCO₃^2-> NO₃^-.  The groundwater of the study area is mostly old marine water origin and is characterized by high TDS which is due to the evaporation process and agricultural activities. The sodium adsorption ratio (SAR) values of collected groundwater samples indicate that the groundwater of the study area is not suitable for domestic and agricultural purposes. The results of oxygen and hydrogen isotopes suggested that both theslope and intercept values of the regression equation of the groundwater scatters are significantly different from those for LMWL suggesting that groundwater has gone through evaporation process before or during its underground transit. The scattered correlation between Cl^- and δD indicated that there is more than one source of Cl^- in groundwater of the study area.

Key words: Groundwater quality, sodium adsorption ratio (SAR), isotope of oxygen and hydrogen, evaporation, agricultural activities.