Application and Calibration of WetSpa Hydrological Model for Daily Runoff Simulation for 2007-2008 to 2011-2012 Water years: A Case Study: Balokhluchay Watershed, Ardabil, Northwestern Iran

WetSpa model simulates water and energy transfer between soil, plant and atmosphere and calculates water balance in cell scale. In this study, the WetSpa model was applied to simulate daily discharge of Balokhluchay watershed in Ardabil province. Three base layers including digital elevation model from 1:50,000 scale topographic maps, landuse map from ETM satellite images and soil texture map from analyses of 38 surface soil samples were prepared in raster format with a sell size of 100 m. Precipitation, temperature, evapotranspiration and discharge data were obtained from Ardabil Regional Water Company in daily time step. The model was run for 2007-2008 to 2009-2010 water years and then was calibrated using both manual and automatic calibration methods. In order to test the model, it was run with 11 calibrated global parameters for 2010-2011 and 2011-2012 water years. Evaluating coefficients for test period including Model Bias, NashSutcliffe, Nash-Sutcliffe for low and high flow, correlation coefficient and mean relative error were calculated -0.0873, 0.4572, 0.3011, 0.6437, 0.6965 and 0.9607 respectively. Results showed acceptable accuracy of model in daily flow simulation and high accuracy of model in high flow simulation in comparison to low flow in study area.