The groundwater resources in Ravansar area, west of Iran, characterizing by two major alluvial and karstic aquifers. Due to the broadly expanded and well tectonized Bisitoun carbonate formation and the existence of siliceous limestone in radiolarite alluvial bed rock aquifer, the dominant groundwater type in Ravansar area is bicarbonate. The precipitation isotopes in Ravansar area varies seasonally as a function of local atmospheric parameters especially temperature and precipitation amounts. The local meteoric water line for Ravansar (RMWL - δ2H = 5.8 δ18O + 2.7), which was developed throughout a monthly cumulative approach, was deviated from the Global and Eastern Mediterranean meteoric water lines (GMWL and EMMWL) in both slope and 2H intercept, suggests the effect of the local conditions on the isotopic content of rains. Depending on the groundwater recharge point and residence time, four categories of groundwater (Bistoon, Radiolarite, Deep and Semi deep groundwaters) were plotted around the RMWL. Moreover, as a result of more evaporation, the groundwater samples collected in dry season were isotopically more enrich than the wet season ones.

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