Rainfall- Runoff Hydraulic Simulation Using Diffusive Wave Model in Kamanaj Olia Watershed

In the present research the transformation of rainfall into runoff was simulated using twodimensional Saint-Venant equations in the Kamanaj watershed, a subwatershed of Ajichay, located in East Azarbaijan Province, Iran. Rainfall-runoff was simulated based on diffusive model by consideration of momentary infiltration rate for temporal and spatial analysis. Saint-Venant equations were solved using explicit method of finite difference numerical technique as the initial and boundary conditions were defined. For this purpose, the watershed area was divided into 250×250 meters cell size grid by the tools of GIS, then digital elevation model was prepared. Kostiokov infiltration model, as the best fitted model to measured infiltration data was selected for expression of infiltration in Saint-Venant equations. Three hydrographs were used to verify the model. In the calibration of the model, lower relative average error of discharge was equal to %9.4. Comparing the simulated hydrographs to those observed, verificated the capability of model in simulation of rainfall-runoff. The presented model can be used for determination of runoff from momentary rainfall with consideration of temporal and spatial variation of infiltration over the watersheds. This model can also be used to forecast the peak discharge and time to peak in the watershed outlet.