INCREASING THE ACCURACY OF RUNOFF SIMULATION USING DIRECTION AND VELOCITY OF WIND, A CASE STUDY OF KARAJ DAM BASIN, IRAN

The movement and motion of cloud mass have great effect on runoff and time of precipitation occurrence is rarely equal in all subbasins of one watershed. Ignoring storm movement influences on runoff simulation and decreases the accuracy of peak flow estimation. The direction and velocity of wind are important factors of cloud mass movement and the time of reaching cloud mass to gravity center of subbasins can be determined using it. According to lack of moment information in Height of cloud formation, direction and velocity information of wind on ground surface was used. Precipitation in subbasins was decomposed based on the rainfall of the nearest recording rain-gauge station and the time of its occurrence in each subbasin was determined considering direction and velocity of wind. Results showed that after determining the time of rainfall occurrence in subbasins based on direction and velocity wind, peak flow of simulated hydrograph had more similarity with observed peak flow, but in most cases, the effect of velocity and direction of wind on runoff volume was effectless.