Simulation of Flow Hydrographs at an Ungauged Site in Taiwan using a distributed rainfall-runoff model

Simulation of flow hydrograph at an ungauged site recently has attracted considerable attention. A distributed rainfall-runoff model not only can describe the spatial heterogeneity of physiographical and hydrological characteristics in the catchment, but also can simulate the hydrological processes inside the studied area. If a distributed rainfall-runoff model can be adequately verified based on measurements both at the outlet and inside the studied area, then confidence that the model can accurately simulate the hydrological processes inside the studied area becomes more justified. The upstream catchment of Yan-Shoei creek was chosen as the study area, and historical flow hydrographs are observed not only at the outlet of the basin, but also at two small reservoirs inside the basin. A grid-based distributed rainfall-runoff model is first calibrated and verified using 12 and five historical storm events respectively, and the model is found to have reasonable rainfall-runoff simulation for the study area. Observed water level hydrographs recorded at these two reservoirs further indicate that the model could accurately simulate the rainfall-runoff process within the studied catchment. Finally, a windows-based program was developed based on the Visual Basic and Geographic information system-Arc View to establish a user-friendly interface. Users can easily input the model data, calibrate the model parameters, run the model and query the simulated flow hydrograph at any ungauged site within the study area.