Flow hydrograph moving method based on inflow-outflow tests and its application on canal seepage calculation

Inflow-outflow test and ponding test are both common ways to measure canal seepage and have their own advantages and disadvantages and respective applicable conditions. Inflow-outflow test is more convenient than ponding test, while less accuracy. Inflow-outflow test is conducted in irrigation period, and its calculation accuracy mainly depends on stability of canal flow. This paper establishes the flow hydrograph moving (FHM) method, by which seepage quantity can be calculated. The FHM method has 3 factors: hydrograph flowing velocity, length between upstream and downstream section and time consumption, and needs 3 steps: drawing hydrographs, moving hydrographs and measuring flow difference. The possible cause of errors is potential flow fluctuation between 2 measurements. After all, time interval is almost inevitable between them. Seepage calculation using the FHM is more suitable under canal's measuring conditions and makes the application of inflow-outflow tests more effectively.