Middle reaches of the Yangtze River are the worst flooded segments along theYangtze River. It is important to understand and study the variations offrequency and magnitude of historical floods in this area and how were theyrelated to or affected by EI Niño in a long historical period. We applied thestatistics and time series to study and analyze historical floods (1470-2000)and EI Niño events (1525-1995). The results show that the more floods occurredin the latest 200 years. The power-spectral analysis suggests the main cycle offlood variation is longer than that of EI Niño events. El Nino shows the fluctuationsof about 2-year and 3~4 year period while the flood variation is not so significantbut can also be identified in the period of 2, 8 and 40 years (it exceeds the levelof confidence 0.03). Time series analyses of the fluctuation of flood and El Ninoindicate that there is a significant correlation between the two at both high andmoderate frequency sections. The result shows that the response of the floodsalong the middle reaches of the Yangtze River to the effects of El Nino eventsis not only delayed one or more than one year as suggested by many Chinesescientists, but it also can be somewhat longer delayed up to about 8 years.The result also indicates that the shorter the interval of EI Niño events,the sooner the flood events follows. In other words, flood could be delayedwith longer time if the interval time of EI Niño events is longer.
展开▼
