Flood simulation and prediction is one of the most active research areas in surface water management. WetSpa is a distributed, continuous, and physical model with daily or hourly time step that explains precipitation, runoff, and evapotranspiration processes for both simple and complex contexts. This model uses a modified rational method for runoff calculation. In this model, runoff is routed along the flow path using Diffusion-Wave equation which depends on the slope, velocity, and flow route characteristics. Golestan Dam Basin is located in Golestan province in Iran and it is passing over coordinates 55° 16´ 50" to 56° 4´ 25" E and 37° 19´ 39" to 37° 49´ 28"N. The area of the catchment is about 224 km2, and elevations in the catchment range from 414 to 2856 m at the outlet, with average slope of 29.78%. Results of the simulations show a good agreement between calculated and measured hydrographs at the outlet of the basin. Drawing upon Nash-Sutcliffe model efficiency coefficient for calibration periodic model estimated daily hydrographs and maximum flow rate with an accuracy up to 59% and 80.18%, respectively.
 M. Azinmehr, A. Bahremand, and A. Kabir, “Simulating the effects of landuse change scenarios on flow hydrograph using the spatially distributed hydrological model, WetSpa, in the Dinvar Watershed, Karkheh, Iran, “Watershed Engineering and Management, vol. 7, pp. 500-511, 2016.
 M. Azari, H. R. Moradi, B. Saghafian, and M. Faramarzi, “Assessment of Hydrological Effects of Climate Change in Gourganroud River Basin. “Journal of Water and Soil. vol. 27, pp.537-547, 2013.
 A. Bahremand, F. De Smedt, J. Corluy, Y. B. Liu, J. Poorova, L. Velcinicka, and E. Kunikova, “WetSpa Model Application for Assessing Reforestation Impacts on Floods in Margecany–Hornad Watershed, Slovakia, “Watershed Resource Management, vol. 21, pp. 1373-1391, 2007.
 F. De Smedt, Y. B. Liu, and S. Gebremeskel, “Hydrological modeling on a catchment scale using GIS and remote sensed land use information“. pp: 295– 304. In: C.A. Brebbia (ed.), Boston: WTI Press. 2000.
 A. Kabir, M. Mahdavi, A. Bahremand, and N. Noora, “Application of a geographical information system (GIS) based hydrological model for flow prediction in Gorganrood river basin, Iran, “Journal of Agricultural Research, vol.5, pp. 23-31, 2010.
 Y. B. Liu, and F. De Smedt, “Flood Modeling for Complex Terrain Using GIS and Remote Sensed Information, “Water Resources Management, vol. 19, pp. 605-624, 2005.
 Y. B. Liu, S. Gebremeskel, F. De Smedt, L. Hoffmann, and L Pfister, “A diffusive transport approach for flow routing in GIS-based flood modeling. “Journal of Hydrology, vol. 283, pp.91-106, 2003
 J. Rwetabula, F. De Smedt, and M. Rebhun, “Prediction of runoff and discharge in the Simiyu River (tributary of Lake Victoria, Tanzania) using the WetSpa model. “Hydrology and Earth System Sciences. Vol. 4, pp. 881-908. 2007.
 A. Safari, F. De Smedt, and F. Moreda, “WetSpa model application in the Distributed Model Intercomparison Project (DMIP2). “Journal of Hydrology. vol. 418, pp.78-89, 2012.
 B. Porretta, J. Chormanski, S. Ignar, T. Okruszko, A. Brandyk, T. Szymczak, and K. Krezalek, “Evaluation and verification of the WetSpa model based on selected rural catchments in Poland. “Journal of Water Land Dev. vol.14, pp.115- 133, 2010.