Study uncertainty of parameters of rainfall-runoff model (WetSpa) by Mont carlo method

Studying and quantifying the uncertainty of the parameters of rainfall-runoff models have been raised mainly in the last decade and now is considered as one of the major challenges in international level. Despite the easy use of most conceptual rainfall-runoff models، due to the large number of parameters and lack of physical understanding of these models، use of them will be difficult in the calibration phase. In this study، uncertainty of the parameters of WetSpa model was investigated in Gorganrood catchment، Golestan province by Mont carlo method. WetSpa is a GIS-based distributed hydrological model that operates on catchment scale and has developed for flood prediction and watershed management. The model is physically based and simulates hydrological processes continuously both in time and space، for which the water and energy balance are maintained on each raster cell. Most of Uncertainties in model simulations results from the model structure and because some of the parameters have not properly defined. So for the correct prediction of runoff، uncertainty of the parameters and also forecast uncertainty should be taken into consideration. An appropriate parameter range was obtained by application of the Mont carlo method. The results show that the correction factor for measured evaporation data Ke has the highest relative sensitivity، because the margin of uncertainty of this parameter is the smallest، while parameters of g0 and Krain have the highest uncertainty.