Abstract:In late July 2025, Chaobai River Basin experienced the most serious flood disaster since 1959. In this paper, a flood simulation and forecasting model is developed for Chaobai River Basin based on a distributed hydrological model to retrospectively analyze the characteristics of the July 2025 regional flood in this basin. The Zhangjiafen hydrometrical cross-section of the Baihe River, the Xiahui hydrometrical cross-section of the Chaohe River, and the Putaoyuan hydrometrical cross-section of the Qingshui River are taken for testing hydrological sections, and a basin flood simulation and forecasting model is developed based on GMKHM distributed hydrological model. The GMKHM model adopts hourly precipitation observation data from CMA regional meteorological stations as forcing input, introduces runoff curve numbers and topographic indices to develop a DEM-based over-storage runoff production model, and has a module of recharging deep groundwater added in the calculation of water source separation. The results show that the peak discharge simulation errors are -1.8% and -4.0% respectively for the Zhangjiafen hydrometrical cross-section of the Baihe River and the Xiahui cross-section of the Chaohe River under the GMKHM distributed hydrological model. The model determination coefficient is 0.87 for the Zhangjiafen hydrometrical cross-section and 0.89 for the Xiahui hydrometrical cross-section. For the Putaoyuan hydrometrical cross-section of the Qingshui River, the peak discharge error is 0.9% and the determination coefficient reaches 0.92. Overall, the GMKHM distributed hydrological model performs well in simulating the July 2025 flood event in the Chaobai River Basin.