An Investigation of The Effects of Land Use Change on Simulating Surface Runoff Using SWAT Mathematical Model

There are several methods of estimating runoff from a catchmant area. One of these methods is the hydrological model. Hyrological models by simulating hyrological processes, make it possible to evaluate runoff from rainfall in the shortest possible time and with the lowest possible costs. However there does not exist the possibility of measurement of all cases in all cachments, so, there is the necesity of choosing those models which can evaluate hydrological processes with a minimum number of parameters. One of these models is SWAT. This model has been developed by Arnold in 1972 and improved towards perfection by Arnold & Wiliams in 1996. The model receives the daily raifall, daily discharge and daily evapotranspiration, after being optimized parameters. This study was carried out in Kasilian catchment area in Iran. Results indicated the value of determination coefficient to be satisfactory for the cachment. In addition, the results of model revealed that ABF, CN2 and REVAPC parameters are the most sensitive among other parameters. Finally the effect of hyrological parameters on the streamflow is evaluated. SWAT model simulated the hydrological processes for agricultural and rangeland uses better than for forest land use.