Abstract :
ABSTRACT: Rainfall-runoff correlation is a complex process with a lot of relative parameters. Main parameters in simulation have an important rule and by some processes, we can change simulated data to actual data. In this study, by use of HEC-HMS model and results of different methods for evaluation of runoff losses (Green and Ampt, Initial and constant loss rate and Deficit and Constant loss) consider to various objective functions (percent error in peaks and volumes) tried to classify the methods. In this way, based on objective functions, the method with least difference between percent of observed and simulated discharges take place in first preference and other methods take place in next preferences. Results showed that Initial and constant loss rate method among six events, in four events by fitting with percent error in peak and in five event by fitting with percent error in volume had better results rather than Green and Ampt method which in three events by fitting with objective function of percent error in peak and in one event by fitting with percent error in volume had less variation coefficient of observed discharges compared to simulated discharges. While, Deficit and constant loss rate method just in three events by fitting with percent error in volume and in two events by fitting with percent error in peak had less changes rather than Green and Ampt method. So, for two objective functions, Initial and constant loss rate method in %70 of events, had less changes percent of simulated to observed discharges and it selected as optimum method for simulation of surface runoff and Green and Ampt and constant loss rate methods took place in next preferences.
