基于模态分解法的长江与两湖水沙特征分析

Analysis on runoff and sediment load in Changjiang River,Dongting Lake and Poyang Lake based on modal decomposition method

为研究长江和洞庭湖、鄱阳湖的水沙变化,利用模态分解方法(Welch能谱法及本征正交分解POD法),对长江和两湖中19个主要水文站1956-2018年的水沙序列变化特征进行分析。结果表明:长江和两湖的径流序列中,存在明显的8 a和20 a周期震荡。利用POD法分析得到的长江和鄱阳湖的径流变化率分别为2%-10%和10%-20%;而输沙变化率都接近90%。洞庭湖的水沙变化率要远远大于长江和鄱阳湖,其中荆江三口水沙变化率在140%以上。

In order to analyze trend of annual runoff and sediment load in the Changjiang River and its two river-connected lakes,Dongting Lake and Poyang Lake,we adopted modal decomposition method to extract variation characteristic of 19 major hydrological stations in the Changjiang River,Dongting Lake and Poyang Lake during 1956-2018.The results showed that predominant periods of 8 and 20 years were discovered in the runoff series.On the basis of the principal component(capturing more than roughly 90%total energy),total change ratios of runoff and sediment loads during the last 63 years were evaluated.For the runoff,absolute total change ratios were 2%-10%and 10%-20%for the Changjiang River and Poyang Lake respectively;while for the sediment load,they were around 90%.However,the change rate of flow and sediment in Dongting Lake were much larger,especially for the three outlets on the Jingjiang River reach(over 140%).