基于小波的三江源年径流变化的周期性分析及趋势预测

Period Analysis and Ttrend Forecasting of Annual Runoff of Sanjiangyuan Based on Wavelet Transform

为了研究三江源径流演变规律,用小波分析方法对三江源唐乃亥、直门达、香达站52年(1956-2007)径流时间序列变化进行了多尺度周期性分析.每个站都有各自的径流丰枯变化周期,三个站作为组成三江源的整体又有共同的周期变化特性.从小波变换时频分布图中得出以下结论:唐乃亥站表现为23年、18年、8年、4年尺度周期变化,直门达站为23年、17年、9年、7年尺度周期变化,香达站为23年、16年、8年尺度周期变化.经小波方差图对主要周期的检验,证明前述结论是正确的.可以看出,三个站表现出了23年的共同周期,同时具有唐乃亥站18年、直门达站17年、香达站16年的近似周期,并且唐乃亥站和香达站有8年的共同周期(直门达站为9年).1956-2007年间,直门达9年尺度下径流变化趋势与香达8年尺度下径流变化趋势非常相似.研究还表明,三个站径流表现出了一致的变化趋势,即2007年以后一段时间内径流还将处于偏丰期,一般持续到2009年,2010-2014年径流将处于偏枯阶段.

Based on the annual runoff time series data of 52 years（1956 ～ 2007） of Tangnaihai,Zhimenda and Xiangda gauge station in the source region of the Yangtze River,Yellow River and Lancang River（Sanjiangyuan）,the periodic variation characteristics in multi-time scales of annual runoff were probed with Morlet wavelet transform method.Each station had its own high and low periods of annual flow,however,three stations had common cycle characteristics as they located near to each other within Sanjiangyuan.We draw conclusions from time-frequency distributions chart of wavelet transform： the major periods of the time series are about 23 years,18 years,8 years and 4 years in Tangnaihai station;about 23 years,17 years,9 years and 7 years in Zhimenda station;about 23 years,16 years,and 8 years in Xiangda station.The foregoing conclusions were also confirmed by wavelet variance graph.The 9-year-scale periodic characteristic of annual runoff of Zhimenda station was very similar to the 8-year-scale periodic characteristic of annual runoff of Xiangda station in the period 1956-2007.The study also showed that there would be a consistent trend of the runoff change in the three hydrological stations,that was,annual runoff would deviate to higher in 2007-2009 and to lower in 2010-2014.