Isotope methods proofed to be a useful tool for management of water resources especially in karstic semiarid and arid environments. The light stable isotopes (e.g., deuterium, oxygen-18) in precipitation generally reflect altitudinal, latitudinal, seasonal, amount and continental fractionation effects which are useful to describe catchment elevation, snowmelt influence, and short-term residence times. Beneath distinct characterizations of impacts on river water, stable isotopes allow to study runoff processes, e.g. mixing, evaporative influence, and residence times of river water in karstic systems. In this work water samples of the upper Karkheh River basin were collected on 8 sites repeatedly during field campaigns in August, September, October and November 2011 and the field sampling is continuing in 2012. All samples were analyzed hydro chemically and for stable isotope composition. This contribution aims to give a first report on stable isotope results and discusses implications for an understanding of hydrological systems and water resources management of karstic semi-arid areas.
