Base Flow Separation Using 18O Stable Isotopes in Abolabas Karstic Basin-Khozestan Province

Although the empirical models of base flow separation meet the engineering desires in evaluating the volume of storm runoff or total drainage of a basin, however, they do not offer an actual understanding of the existing processes. The common runoff models often assume that the groundwater base flow into the river during wet season is minor. The tracing isotopic methods show that it is not the case and it has caused a close look at the runoff generation processes. In this study, during the winter 2010-2011, three rainfall events with different antecedent moisture and intensity and the corresponding flood were sampled to analyze isotopic composition in stable isotope laboratory of OttawaUniversity. Results showed that surface runoff component was minor for the low moisture conditions, and it increased for the high moisture conditions. Also, the contribution of groundwater component to total runoff was considerably large due to karst development in the Abolabas basin.