以中国山洪水文模型为基础，综合考虑前期影响雨量、累积雨量、降雨强度及雨型分布、地形地貌等因素的影响，提出了基于分布式水文模型的小流域动态临界雨量预警指标分析方法。以四川省不同水文分区3个典型小流域（赶场、西宁和新生流域）为例，评估了该指标用于小流域山洪预警的精度。研究表明：(1)中国山洪水文模型在研究区内具有较好的适用性，3个小流域率定期和验证期的山洪模拟合格率均在90%以上；(2)以1 h、3 h和6 h为预警时段，赶场、西宁和新生流域的临界雨量分别为20~250 mm、12~160 mm、6~140 mm；(3)不同预警时段下，3个小流域山洪预警的合格率达到80%以上。研究成果可为小流域山洪预警提供理论支持和技术支撑。

Flash flood warning at catchment scale was determined by dynamic rainfall threshold using China Flash Flood Hydrological Model (CNFF),considering antecedent soil moistures,accumulated rainfall depths,rainfall intensities,rainfall temporal patterns,and topographies.Three typical catchments of different hydrological characteristics were selected in the Sichuan province as study area to assess the accuracy of CNFF for early warning flash floods.Results show that:（1） CNFF was suitable for flash flood simulation in the study area,and the qualifying ratios were over 90% in the selected catchments;（2）With rainfall durations of 1 h,3 h,and 6h,the critical rainfall thresholds were obtained as 20~250 mm,12~160 mm,6~140 mm for Ganchang catchment,Xining catchment,and Xinsheng catchment,respectively;（3）The qualifying ratios for flash flood warning were over 80% under different rainfall durations for all catchments.This study may provide technical support for early warning flash floods at catchment scales.

国家自然科学基金（41807171;51579131）；国家重点研发计划（2017YFB0203104）