The influence of time domain on flood season segmentation by the Fisher optimal partition method

Abstract

Abstract Setting the staged flood limit water level (FLWL) through flood season staging is an important means of fully utilizing reservoir flood resources. The Fisher optimal partition method has been widely used to determine the optimal staging of a flood season. It requires a certain time-domain as the basic unit. This study aimed to analyze the influence of various selected time-domain units on the staging results and to provide a scientific time-domain selection basis for the application of the method in flood season staging. Flood season staging was conducted by taking four specific time-domains: 5, 7, 10, and 15 days as the basic units. The rationality of the flood season staging scheme was tested using the improved Cunderlik method, and the influence of specific time-domains as the basic units in the Fisher optimal partition method on the staging results was evaluated. The results showed the highest relative superiority of 0.9681 for the time-domain unit of 5 d. Therefore, it is recommended that 5 d be used as the time-domain unit. The optimal staging result was determined as June 20 for the first segmentation point and August 20 for the second. According to the results of the staged FLWL compared with a single fixed FLWL, the water level was raised by 5.2 m in the pre-flood season, 0.3 m in the main-flood season, and 3.7 m in the post-flood season. Water storage increased by 24.628 million m³ during the flood season, effectively alleviating the contradiction between water supply and storage.