长江大通站输沙量时间序列分析研究

STUDY ON TIME SERIES OF SEDIMENT DISCHARGE AT DATONG STATION IN THE YANGTZE RIVER

长江来水来沙直接影响着河口三角洲的发育过程以至入海物质通量变化.大通站作为长江河口的第一个关键界面,有近50年左右的输沙量和流量连续观测资料(1953～2001年).利用肯德尔、有序聚类和熵谱分析等方法,着重对输沙量时间序列进行了统计分析.大通站径流量在保持稳定的情势下,输沙量在过去49年中有明显的下降.输沙量变化主要呈跳跃式下降,同时表现出16年左右周期性阶梯下降规律,1968年和1984年分别为阶梯下降的跳跃点.尤其1984年后,年均输沙量比1984年前下降26.4%,且最大值未超过1984年前的平均值.输沙量减少与人类活动密切相关.20世纪80年代末的'长江上游水土保持重点防治工程'的实施,使长江上游的来沙减少,这是大通站输沙量减少的主要原因;其次是长江流域内水利工程的拦沙作用.

The discharge of the water and sediment of the Yangtze River affect directly the evolvement of the Yangtze River delta,and even the change of material flux towards the sea. Datong station is the first interface in the Yangtze River estuary. There are nearly 50 years field data for the sediment and water discharge (1953~2001). In this paper, probability statistics and time series method such as Kendall method, order clustering method, Entropy spectral analysis were used to analyze the sediment discharge. The runoff discharge has been stable in Datong while sediment discharge has been declining obviously over the past 49 years. The change of sediment discharge decreases mainly in the form of jumping, taking on the rule of step-down once every 16 years.In 1968 and 1984 the hopping site of step down was observed. The sediment discharge decreases greatly in Datong. After the hopping site (1984), the average sediment discharge per year decreases 26.4 % compared with the years before 1984, and even the maximum didn't exceed the average for years before 1984. The decline of sediment discharge is mainly related with activities of human-beings. The main reason for sediment discharge decrease is the implementation of soil and water conservation along the Yangtze River since late 1980's with the effect of sediment trapping in the Yangtze drainage area.