Application of a Developed Grid-Xinanjiang Model to Chinese Watersheds for Flood Forecasting Purpose

A distributed rainfall-runoff model, Grid-Xinanjiang model based on the topographical information of each grid cell extracted from the digital elevation model (DEM), was developed to simulate the hydrologic processes within watersheds. The water exchange among grids within the watershed and the runoff routing along the river drainage networks are taken into consideration in the model. The Grid-Xinanjiang model was applied to the two watersheds in China for flood simulations. The performance of the developed model was compared with that of the original Xinanjiang model. Initial tests show that the Grid-Xinanjiang model can perform well as the original model in terms of estimates of streamflow and of the model efficiency coefficient. All of the qualified ratios relative to peak flow, runoff, and peak time for the two models applied to the Misai watershed and the Xixian watershed are more than 88%. The Grid-Xinanjiang model outperformed the original model in predicting flood runoff and outlet hydrographs, especially in the larger watershed. The simulation results show the robust capacity of obtaining spatial distributions of hydrologic variables over the original Xinanjiang model, and also revealed that runoff yield has large temporal and spatial variability during storm period and the runoff response is sensitive to the antecedent soil moisture, topography, and spatial distribution of rainfall.