Hydrological Modeling of Snow Accumulation and Melting in Semi-Arid and Mountainous Watersheds (Case study: Bar Arye Watershed)

In this study, the WetSpa model was utilized to simulate the snow accumulation and melting processes in the Bar Arye mountainous watershed with an average altitude of 2225 meters above the mean sea level. The input data used in this study included daily records of precipitation, air temperature and potential evapotranspiration, covering the period of 2003 to 2008, as well as three types of maps, namely; land use, soil texture and topography maps. According to Nash-Sutcliffe assessment index values (0.67, 0.69) for the calibration and validation periods, the model could simulate the Bar Arye river flow with high accuracy. The results indicated that the temperature threshold for snow formation in this catchment was 0.11°C. According to the water balance components, it was indicated that the maximum amounts of equivalent snow water belonged to the months of December (29.25 mm) and January (37.94 mm), while the maximum snow melt values were observed during March and April , as 38.89 mm and 37.14 mm, respectively.