Qualitative and quantitative uncertainties in regional rainfall frequency analysis

Abstract

Uncertainty exists widely in hydrological analysis, and this makes the process of uncertainty assessment very important for making robust decisions. In this study, uncertainty sources in regional rainfall frequency analysis are identified for the first time. The numeral unite spread assessment pedigree (NUSAP) method is introduced and is first employed to quantify qualitative uncertainty in regional rainfall frequency analysis. A pedigree matrix is particularly designed for regional rainfall frequency analysis, by which the qualitative uncertainty can be quantified. Finally, the qualitative and quantitative uncertainties are combined in an uncertainty diagnostic diagram, which makes the uncertainty evaluation results more intuitive. From the integrated diagnostic diagram, it can be determined that the uncertainty caused by the precipitation data is the smallest, and the uncertainty from different grouping methods is the largest. For the downstream sub-region, a generalized extreme value (GEV) distribution is better than a generalized logistic (GLO) distribution; for the south sub-region, a Pearson type III (PE3) distribution is the better choice; and for the north sub-region, GEV is more appropriate. 通过引进 NUSAP 方法量化区域降雨频率分析不确定性来源中质量方面的不确定性, 并结合数量方面的不确定性, 分析这些不确定性对降雨频率分析的影响, 为水资源风险决策和水利工程设计等提供更好的指导。 总结区域降雨频率分析中的不确定性来源, 并在区域频率分析中引进 NUSAP 方法用以量化其质量不确定性, 针对区域频率分析提出 Pedigree 矩阵。 1. 选取区域频率分析中三个主要不确定性来源, 即降雨测量不确定性、 水文分区不确定性和分布线型的不确定性; 2. 提出针对区域频率分析的评价依据 Pedigree 矩阵, 量化区域频率分析中的质量不确定性; 3. 将质量和数量两类不确定性结合在不确定性诊断图中, 综合评估区域频率分析中的质量不确定和数量不确定性。 NUSAP 方法可以有效地量化区域降雨频率分析中的质量不确定性, 并通过不确定性诊断图将质量不确定和数量不确定性很好地结合起来, 为水资源风险决策和水利工程设计等提供了直观的方案。