多沙河流水沙变化特征小波分析

为了给多沙水库运行调度提供依据,降低水沙序列长度和随机性的影响,将小波变换应用于研究流域径流与含沙量的变化特性。采用db3小波对标准化径流与含沙量序列进行多分辨率分析,研究径流与含沙量变化的趋势性;选用复Morlet小波绘制出小波方差图,分析径流过程与含沙量过程存在的周期性。以崖羊山水电站所在的李仙江流域为例,针对电站坝址断面的月平均流量与含沙量序列进行小波分析,从低频重构序列的结果中可以看出该流域径流与含沙量的变化趋势;并结合当地的降雨量与水土保持状况分析,表明结果是合理的。根据小波方差图可以看出,崖羊山水电站所在流域径流过程与含沙量过程存在非常接近的显著周期,均为2 a左右,且两者变化周期具有同步性。研究结果表明小波分析是研究非平稳随机时间序列的有效方法。

Wavelet Analysis on Flow and Sediment Variation in Sandy Rivers

In the aim of providing basis for the operation of sandy reservoir and reducing the influences of length and randomness of flow and sediment series,wavelet transform was adopted to analyze the variation characteristics of flow and sediment series.Standardized monthly flow and sediment series were decomposed by Multi-resolution Analysis using the db3 wavelet function,and continuous wavelet transform was used to evaluate the periodic variations of the two standardized series using the complex valued Morlet function.The flow and sediment series at the dam site of Yayangshan Hydropower Station located in Lixianjiang watershed were taken as an example.The reconstruction of the lowest frequency part revealed the trend of the flow and sediment series.According to the local rainfall and soil and water conservation,the result is considered reasonable.Wavelet variances were obtained to identify the dominant period as 2-year approximately for both flow series and sediment series and reveal the synchronization between them.The results indicate that wavelet transform is effective for nonstationary stochastic series analysis.