A study on the effects of karst area on the source of river’s base flow using modified Saturation Area Model (SAM) in Kazeroon and Barm Plain basins

Monthly water balance models (rainfall-runoff models on a monthly basis) are major tools in long-term planning of water resources. The basic structure of these models includes continuity equations for soil moisture storage, subsurface flow and groundwater. Due to the complexity of the formation process and the different sources of flow, Rainfall-runoff models have different structures and need to be improved, simplified and revised according to the studied catchment conditions. If there is a karst origin in the study area, because of its importance in providing drinking water, it can not be simply ignored in the modeling. In this study, the structure of daily reservoir Saturation Area Model (SAM) is modified to improve the prediction of base-flow and monthly runoff in Kazeroon and Barm plain karst basins. The results of the modified model (SAM-KARST( and original model (SAM) have been compared and then the performance of the proposed model has been evaluated. The obtained results showed a relative improvement in the performance parameters of SAM-KARST in comparison to SAM for the study basins.By considering the conceptual reservoir for karst origin in the model, the contribution of base flow obviously increased, which indicate the important role of karst origin in supplying base flow.