Simulation of snow cover area and its runoff in Horo-Dehno watershed in Lorestan Province

Given the importance of snow, it seems necessary to predict its resultant runoff for optimized usage. In addition, due to snowbound regions cloudiness in winter season, the notice of snow cover area (SCA) using satellite images is difficult. Hence, to help better water resources managing in mountainous areas using supplementary methods for simulating the SCA is necessary. As a case study, Horo-Dehno watershed in Lorestan Province with the area of 263 Km2 was selected. By applying WetSpa model as a verified and promising simulation tool, snow melting runoff as well as snow cover area was simulated based on degree-day approach in Horo-Dehno watershed. Water and Energy Transfer between Soil, Plants and Atmosphere (WetSpa) is a distributed spatial-physical model that simulates different hydrological processes including snow cover area, snow accumulation and melting in a cellular manner at hourly and daily time step by employing energy balance as well as degree-day approaches. Subsequently, simulated the SCA and runoff by the model were compared to the satellite images (MODIS) and the measured discharges at the output of the watershed respectively. In this research, 4-years regional data (from 2007 to 2011) including precipitation, temperature, evaporation, runoff and three digital maps of elevation model (DEM), land use and soil texture with resolution cell size of 100 * 100 meter were used. According to the results, Nash – Sutcliffe efficiency criterion of stream-flow simulation for calibration and validation periods were 0.7034 and 0.655 respectively. Consequently, WetSpa model has promising strength for stream-flow and runoff snowmelt simulation in daily time steps. Furthermore, through comparing snow cover extracted from the model with that of MODIS satellite images at the same periods, it was revealed that simulated snow cover is in a good agreement with observed snow cover.