Using Copulas to Evaluate Rationality of Rainfall Spatial Distribution in a Design Storm

• Main Authors: Leizhi Wang, Qingfang Hu, Yintang Wang, Zhenduo Zhu, Lingjie Li, Yong Liu, Tingting Cui
• Format: Article
• Language: English
• Published: MDPI AG 2018-06-01
• Series: Water
• Subjects: Copula function; flood control planning; extreme rainfall; conditional probability; Tai Lake Basin; design storm
• Online Access: http://www.mdpi.com/2073-4441/10/6/758

In the absence of long-series streamflow records in plain areas, design storm, which serves as the most important input in a hydrologic model, plays an important role in flood control and water resources management. For a large drainage basin, design storm may be estimated for sub-basins separately; thus the spatial distribution of design storm needs to be carefully treated. However, few studies have been carried out to evaluate the rationality of the spatial distribution in a design storm, which means the storm over space should be in accordance with actual needs or its distributing patterns. Taking the Tai Lake Basin (TLB), 3-d Copula-based models combining extreme rainfall of different sub-basins were built using long-term rainfall data, and conditional probabilities of sub-basins encountering certain amounts of rainfall were investigated to evaluate the rationality of the design storm. Results show that the spatial distribution of the design storm based on a typical year is hardly rational, in which rainfall of the northeastern part of the basin is suggested to be weakened while in the southwest to be strengthened; after the rainfall is redistributed based on long-term information, it shows a better rationality of spatial distribution. Such information provides valuable significance in guiding flood control of TLB, and the considered evaluating method can be used for similar basins in plain areas.