Calibration of emprical models for estimating runoff depth in l)aryach_e Namak Basins to determine suitable models (1379-1382)

Prediction and understanding of runoff production processes and it's transport to the outlet of the basin is one of basic issue in hydrology. The runoff depth is a flow index, which is needed in water resource and engineering construction. In ungaged station the empirical rainfall- runoff method could be used to predict the runoff depth, however the efficiency of the empirical model varies in different region and should be calibrated. ` . In this research the accuracy and precision of the empirical rainfall ~ runoff models, were investigated in Daryacheh_e Namak Basin. The main exclusive methods that selected in this research were Turk, Kutain, ICAR, Justin, Khosla and Lasy models. The estimated runoff was compared with the observed data that i obtained from 47 hydrometric stations. In the selected sub basins, characteristics that i need in the models were obtained. For comparing the results of empirical models , observed runoff at stations, were used. The compartion of observed and estimated data, showed that the ICAR , Cutain, Justin and Turk methods have the required accuracy and precision i (respectively). By increasing the area of watershed, the precision of the ICAR method decreases and in this condition the Lasy method is more suitable. In order to calibrate the empirical method, the data splited in two parts. The first part used for calibration and the second part used for verification of calibrated models. The regression equation between observed and estimated data (in first part) T in each method was obtained to correct the methods using a correction coefficient. The calibration results showed that, only the Khosla method was acceptable. i Application of regression model in estimating runoff, using independent i factors such as area, elevation, slope and rainfall with first part of data, was investigated. Useing the regression models in second part data, showed that the results are acceptable but have less accurate and precisen in comparing with ICAR method.