Application of GIS-based Hydrological Models in Semi-arid Watershed

Two GIS-and-DEM-based distributed hydrological models are developed. The runoff production theory of Xinanjiang model and TOPMODEL, i.e. GTOPMODEI, and Grid-Xinanjing model, are used for reference, flood forecasting and hydrological simulation. In Grid-Xinanjiang Model, water exchange among grids and the confluence of river drainage network are considered. TOPMODEL is improved by establishing the relationship among initial soil-moisture deficit, topographic index and initial flow. Xinanjiang model, the improved TOPMODEL and the two improved models are applied to flood forecasting in the semi-arid watershed. The analysis of the results demonstrates that the four models all perform well for flood forecasting and simulation in the semi-arid watershed and two distributed hydrological models perform better. Though the four models are based on the saturation-excess mechanism of runoff generation, all of them are applied successfully. The reason is that, in semi-arid watershed, stable infiltration can usually be obtained in one hour. Therefore, in order to distinguish the mode of runoff yield from the historical hydrological data, the step-time of the data should be less than 0.5 hour.