The spatiotemporal heterogeneity in precipitation and underlying surfaces and hybrid runoff generation mechanism make hydrological modelling and forecasting in semi-arid regions becoming a challenging work. Therefore, to provide a reference for the development of hydrological models in such regions, two nested hydrological experimental watersheds in semi-arid regions were selected for attribution analysis. Based on the concept of large-sample hydrology, large-scale numerical simulation experiments were performed by constructing different spatial and temporal scale rainfall schemes and combining three hydrological models with different runoff generation mechanisms. Finally, the influences of the time step, station density, and model structure on the flood simulations in semi-arid regions were evaluated. The spatial interpolation technique was used simultaneously to describe the high-dimensional complicated nonlinear relationships between the influencing factors and simulation results. The results show the following: (1) the flood simulation accuracy was more sensitive to the time step than the spatial station density of the rainfall schemes and was highly dependent on the time step of the original observation data, and (2) compared with the accuracy of the rainfall schemes, the model structure plays a dominant role in flood simulation accuracy. Thus, the hybrid model has significant potential for flood forecasting in semi-arid regions by combining different runoff generation mechanisms. (3) The spatial interpolation technique based on the k-nearest neighbour algorithm can construct a high-dimensional distribution between the influencing factors and model simulation accuracy, and describe the complicated relationships among the time step, station density, model structure, and flood simulations.

降水和下垫面的时空异质性以及混合径流产生机制使半干旱地区的水文建模和预测成为一项具有挑战性的工作。因此，为了为该地区水文模型的开发提供参考，选取了两个半干旱地区嵌套的水文实验流域进行归因分析。基于大样本水文概念，构建不同时空尺度降雨方案，结合三种不同产流机制的水文模型，进行大尺度数值模拟实验。最后，评估了时间步长、站点密度和模型结构对半干旱地区洪水模拟的影响。同时使用空间插值技术来描述影响因素与仿真结果之间的高维复杂非线性关系。结果表明：（1）洪水模拟精度对时间步长比降雨方案的空间站密度更敏感，并且高度依赖原始观测数据的时间步长，（2）与降雨方案的时间步长相比。降雨方案的准确性，模型结构在洪水模拟精度中起主导作用。因此，混合模型通过结合不同的径流生成机制，在半干旱地区的洪水预报中具有巨大的潜力。