Roodzard Representative Watershed Surface Runoff and Evapotranspiration Simulation Using Stanford-IV Model

Prediction of watershed responses and simulation of runoff rate and volume are required for design purposes in most water resources projects. For this purpose, different hydrologic methods and events based on continuous hydrologic mathematical models are applied. In this research, a continuous hydrologic model, Stanford Watershed Model-IV (SWM-IV) is used for simulation of annual and monthly volumes and mean daily runoff flow produced in Roodzard representative basin with an area of 896 km2 located in southwest of Iran. The accuracy of the simulation outputs were checked using the sensitivity analysis over reasonable ranges of input sata related to Roodzard watershed. Calibration and verification of the Stanford model were performed using the data of 1976-1977 and those of the four consecutive years (1978- 1981). The output of the SWM-IV model showed that the values of annual and monthly runoff, groundwater, and monthly interflow can be simulated in close agreement and acceptable precision corresponding to the observed data. The model is also capable of combining the hydrologic components of the basin to determine the dominant flow of the study watershed. Actual evapotranspiration and annual runoff coefficients, are two other parameters that have been estimated successfully by the model. However, the coefficient of determination (R2) for the observed and predicted daily flow values ranged from 0.44 to 0.81 for the available data. Therefore, application of the model is recommended for predicting the hydrologic responses of various sizes of watershed in Iran.