Zagros mountain range (ZMR) covers the most karst carbonate formations in Iran. Because of the broad expansion of folded and fractured carbonate rocks, well-developed karstic aquifers can be found in NW of ZMR which is reflected in the existence of many karstic springs with large amount of discharge water (up to 6 m3/s). These important karstic formations (in PV, JR, RS and PZ study areas) are supplying water for residents and it seems to be a recharge source for the adjacent alluvial aquifers. A narrow range of isotopic compositions observed in JR (-7.5 to -7.0‰ and -38.5 to -35.0‰ for 18O and 2H, respectively) and PV regions (-7.5 to -6.3‰ and -40.5 to -33.6‰ for 18O and 2H, respectively) indicates the same origin for water for springs and rivers in these areas. The wider isotopic range of 18O (-8.1 to -5.6‰) and 2H (-46.2 to -26.2‰) observed in RS and in PZ regions (from -6.8 to -3.9‰ and from -36.2 to -21.7‰ for 18O and 2H, respectively), indicate the existence of different recharge areas for the aquifers in these areas. PZ is the only study area that has 5 alluvial springs and their isotopic compositions indicate the alluvial aquifer is feed by discharge from the underneath karstic aquifer. The good correlation observed for the relationship between altitude and isotopic composition in springs indicated the groundwater flow system and altitude of recharge are the main factors controlling the isotopic composition of the water in the study areas.

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