Karst springs of the Zagros Mountains contribute a signi!cant amount to agricultural and human water demand in semiarid and arid regions of western and southeastern Iran. For an adequate management of available water resources, sufficient hydrological monitoring is needed and hydro-chemical and isotope hydrological information provides important additional information. Because of the complexity of karst systems, environmental signals (finngerprints) bear important hydro-geological and hydrological process information. Since August 2011 about 320 water samples were collected from precipitation and river water of the upper part of the Karkheh River basin (21.070 km2; between 35°04’ and 33°34’ North and 49°10’ and 46°21’ East; elevation is ranging from 900 to 3.566 m a.s.l.). Sampling was conducted in about monthly time resolution and the same sampling protocol is continued during 2012. All samples were analyzed for hydro-chemical parameters (ph-value, electrical conductivity, major ions) and stable isotopes (deuterium, oxygen-18). Precipitation was collected for an isotopic characterization at six sites within the study site. Snow samples were collected infrequently because elevated areas are not accessible during winter. Results indicate that stream $ow and karst springs chemically respond to weather conditions and seasonal changes. Hydro-chemical variability re$ects karst and hydro-geological characteristics. The isotope values of precipitation indicate a local meteoric water line (Zagros MWL) ranging between the Mediterranean MWL and Global MWL at (y=7.9x + 17 R2=0.98). The river water isotope values vary between -8.0 ‰ and -4.0‰ and -45‰ and -25‰ for d18O and d2H, respectively, thus re$ecting winter snowmelt and evaporation impacts. This contribution implements stable isotopes and hydrochemical information to understand rainfall-runo% processes in karstic semi-arid ar
