【摘要】 水文计算的不确定性是影响模型适用性与精度的关键因素，该文旨在评估子流域单元划分对洪水峰值流量计算的影响。以四川省汶川地震灾区典型小流域为研究对象，基于历史最大降雨特征值，采用土壤保持服务(soil conservation service, SCS)水文模型评估了子流域单元划分对洪水峰值流量的影响，并结合实际洪水案例进行验证。研究结果表明，对于面积2 km~2左右的小流域，子流域单元划分对洪水计算结果的影响可以忽略，但对于面积为数十平方公里的小流域，子流域单元划分对洪水计算有显著影响，洪峰流量随子流域的数目呈负幂减小趋势。不同降雨总量条件下，洪峰流量的减小趋势基本一致；不同雨型条件下，减小趋势有所区别，其中“先大后小”雨型的减小幅度最大。通过细化子流域单元划分，能够更精细地考虑流域内的水文汇流过程，降低洪峰流量。更多还原

【Abstract】 Uncertainty in hydrological calculations serves as a pivotal determinant impacting the reliability and precision of model predictions, and the purpose of this paper is to evaluate the impact of sub-watershed unit division on the calculation of flood peak discharge. This study focuses on a typical small watershed in the Wenchuan earthquake-affected area of Sichuan Province, based on historical extreme precipitation data and hypothesizing rainfall scenarios, the SCS hydrological model is employed to assess the impact of sub-watershed division on peak discharge, and the results are validated with actual flood cases. The results indicate that for small watersheds with an area of around 2 km~2, the division of sub-watershed has a negligible impact on flood calculation results. However, for small watersheds covering tens of square kilometers, the division of sub-watershed units significantly influences flood calculations. The finer the sub-watershed division is, the more the calculated peak discharge decreases, following a negative power-law trend. The decreasing trend of peak flow is generally consistent under different rainfall totals, however, it varies under different rainfall patterns, with the largest decrease occuring under “high first, then low” rainfall pattern. By refining the sub-watershed division, it is possible to more accurately account for hydrological confluence processes within the watershed and reduce peak discharge.更多还原