三峡调蓄前后径流变化的多尺度分析

Multi-scale Analysis of Runoff Variation before and after the Three Gorges Reservoir

径流时间序列复杂多变,既存在着非周期成分(趋势、突变等)变化特征,又存在着多尺度的周期变化特征,水文径流的多尺度分析研究具有重要价值。主要利用极点对称模态分解(ESMD)方法,对宜昌水文站多年实测径流量进行模态分解及时频分析,得出不同的时间尺度下,该站径流的趋势、突变及周期变化,进而分析三峡水库调蓄前后的径流变化规律;同时分别利用传统径流分析方法中的Mann-Kendall(M-K)法、小波变换法及希尔伯特-黄变换法三种方法对ESMD法所得结论进行验证。研究结果表明:三峡调蓄前后,不同时间尺度下的径流均存在2003年6月左右的突变点,趋势项上均表现为不显著的递减变化趋势,这表明三峡工程的正式蓄水对径流量产生了较为明显的影响;年、月、日的周期则表现出了一致性,证实了径流研究具有不同尺度上的嵌套性,同时ESMD法在径流多尺度分析上具有较好的应用效果。

The runoff time series is complex and variable, and there are both non-periodic components (trends, mutations, etc.) and multi-scale periodic variations.The multi-scale analysis of hydrological runoff is of great value.In this paper, the pole-symmetric mode decomposition (ESMD) method is used to analyze the modal decomposition and time-frequency analysis of the long-term measured runoff of Yichang Hydrological Station.The trend, sudden change and periodic variation of the runoff at the station are obtained at different time scales.The runoff variation law before and after the storage of the Three Gorges Reservoir is carried out.The results obtained by the ESMD method are verified by Mann-Kendall (MK) method, wavelet transform method and Hilbert-Huang transform method in the traditional runoff analysis method.The results show that before and after the Three Gorges Reservoir, the runoff at different time scales had the sudden change point around June 2003, and the trend items showed an insignificant decreasing trend, indicating the official water storage to runoff of the Three Gorges Project.It has obvious influences;the cycle of year, month and day shows consistency, which proves that runoff research has nesting on different scales, and ESMD method has better application effect on runoff multi-scale analysis.