Investigation of Different Time Scales Rainfall-Runoff Modeling and Calibration using HMS SMA

Performance of hydrological models will depend on how they are calibrated. In these models, the value ​​of some parameters can be estimated with direct observations and measures. But some others are not directly observable and their estimations can be carried out by indirect techniques of model fitting in historical data. The main aim of this study is to investigate about the performance of soil moisture accounting model (HMS SMA) in annual, semiannual, seasonal and monthly time scales to estimate the effect of soil moisture on causing of runoff. In this research, after of Zolachay watershed Modeling with Extension HEC-GeoHMS and finally by estimating accounting model parameters of soil moisture, the rainfall- runoff simulation in other scales has been done. By analysis of measures and enhancement of HMS SMA Model parameters, we can claim that monthly time scale in calibration model can work more accurate than seasonal, semiannual, and annual time scales. Regarding the estimation of peak flow, it can also be said that time - seasonal scale is the best one to meet the above- mentioned goal.