Calibration and Uncertainty Analysis of a Semi-Distributed Model in a Semi-Arid Region, Case Study: Nishabour Watershed

Application of conceptual hydrological models is an important issue in watersheds for researchers, especially in arid and semi-arid regions. The hydrological behaviors are complicated in such watersheds and their calibration is more difficult. In this article, the conceptual and semi-distributed SWAT model is used for a semi-arid Nishabour watershed with 9350 km2 area. Streamflow simulation is considered for 8 years. Nishabour watershed modeling led to 22 subbasins and 146 Hydrologic response units. SUfI2 approach is used for calibration and uncertainty analysis of watershed modeling. Results showed that calibration and validation of watershed model is not satisfactory, because of uncertainties in conceptual model such as dam structures, and land subsidence. Another reason is related to the complexity of hydrological system in arid regions which has simplified in hydrological models. Moreover, the complex behavior between runoff and subsurface flow in low depth of rainfall events usually effects in hydrological simulation results. Finally, it concluded that we cannot rely on conceptual hydrologic models with different sources of uncertainty without including them in hydrological modeling at arid and semi-arid watersheds.