Accurate estimation of basin discharge has been discussed by the experts in various construction projects and this important issue has considerable influence on the design of the required structures and their cost. Basin discharge can be calculated according to different methods. According to the conditions of the basins under study, the accuracy of these approaches varies and the obtained results often show relatively large differences. To estimate the annual average flow of the basin, the obtained results of discharge stations are analyzed by different methods and regional relations discharge are obtained. To this end, in this study four regional models consists of an area – discharge, area – standard deviation, area - specific discharge and height - discharge have been used. Also, basin discharge estimation is presented based on flow shortage methods. For this purpose, the method of empirical relations, like ICAR, Justin and Coutange catchment were used to calculate discharge then regional models were compared. The obtained results indicate the accuracy of the results of flow shortage methods to determine the discharge basin. In this research, Polrud basin co-discharge model has been developed in the Gilan province by using the capabilities of GIS model.