Simulation of Rainfall-Runoff Process Using Green-Ampt Method and HEC-HMS Model (Case Study: Abnama Watershed, Iran)

Estimation of surface runoff in a watershed based on the rate of received precipitation and quantifying discharge at outlet is important in hydrologic studies. In this study, HEC-HMS hydrological model version 3.4 was used to simulate rainfall-runoff process in Abnama watershed located in south of Iran. To compute infiltration, rainfall excess conversion to runoff and flow routing, methods like Green-Ampt, SCS Unit hydrograph and Muskingum routing were chosen, respectively. Rainfall-runoff simulation has been conducted using five rainstorm events. Initial results showed that there is clear difference between observed and simulated peak flows. Therefore model calibration with optimization method and sensitivity analysis has been done. The results showed that lag time is sensitive parameter. Model validation using optimized lag time parameter showed reasonable difference in peak flow. Finally it can be concluded that model can be used with reasonable approximation in hydrologic simulation in Abnama watershed.