The available quantity of surface water is an important index in water resources planning for a basin or region.This paper applied the algorithm that the cross-section excess flow deducts ecological water consumption inner river and the surplus water volume difficult to control and utlize outer river,and deducts the repetition calculation between the both.The observed and statistical data of the stations of Huaxian and Zhaungtou were used to make analysis and calculation,and the result was got that the mult...