River Flow Simulation Using Distributed Hydrological Model WetSpa in Atrak Watershed

Simulation of rainfall-runoff process in the watershed has a significant importance from various points of view، such as better understanding of hydrological issues، water resources management، river engineering، flood control structures and flood storage. Therefore in this study، the river flow and surface runoff are simulated using the distributed hydrological model، WetSpa. In the WetSpa model runoff process of the basin is simulated using diffusive wave approximation method based on gradient، flow rate and distributed features along the flow routes. Atrak watershed with about 11639 km2 area is one of the largest watersheds of Iran and average annual precipitation is about 283mm. Meteorological data from 1383 to 1390 consisting of rainfall in 25 stations، temperature and evaporation measurements in 5 stations were used as model input data. To run the model three base maps including DEM، land use and soil type with cell size of 100m were provided. Simulation results show a relatively good agreement between calculated hydrographs and measurements at the basin outlet. The model estimates daily hydrographs، with an accuracy of over 60% and 53% based on Nash-Sutcliff criterion، for calibration and validation periods، respectively. And based on Nash-Sutcliff criterion adapted for the maximum flow rate، the model accuracy was evaluated as 77%. According to model output and hydrological factors with spatial distribution at each time step، the model has the ability to analyze topographic effects، soil texture and land use in hydrological behavior of basin.