Located in semi-arid and arid regions in the world, the Middle East has always faced water shortage crisis. Therefore, water resources in this area should be studied by accurate methods such as the stable isotope technique. The results of the current isotopic study show the effects of the main local (temperature and precipitation) and regional parameters (teleconnection indices) on the δ18O values of precipitation and surface water resources across the Middle East. Plotting the values of δ18O vs δ2H in some of the major rivers in the Middle East on the local meteoric water lines shows that the surface water resources are dominantly recharged by local precipitation, while the deviation observed in some samples is due to evaporation. The contributions of various air masses (the precipitation events originating from the main air masses) in the recharge of the principal rivers have also been studied. The results of the mixing models demonstrate that the contributions of various air masses in the recharge of rivers vary significantly across the Middle East.

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