泾河流域枯水复杂性研究

Complexity Analysis of Low Flow in the Jinghe Watershed

枯水复杂性作为枯水的重要特征,在枯水研究中具有重要的意义。论文以泾河流域张家山水文站1933—2010年的月径流序列为研究对象,基于距平法和均值标准差法对比确定月枯水序列,基于近似熵(Ap En)分析枯水的复杂性。结果表明:1)年径流在0.01水平下呈现极显著的递减趋势,流域1997年以来发生枯水的频率越来越大。张家山水文站月枯水量上界为9 369.67×10~4m^3,1、2和12月径流量小于月枯水量上界的月份比例远大于其他月份的比例,故以这3个月的月枯水组成枯水序列;2)枯水序列的Ap En值为1.059 1,与同期整个月径流序列的Ap En值(1.059 7)接近,说明发生于1、2和12月的15个非枯水月份径流对枯水序列的复杂度影响不大;3)月枯水复杂度在0.05水平下呈现显著的波动递增趋势,与月枯水径流呈显著的负相关关系,但与月降水量不显著相关,表明降水不是枯水径流系统的主要输入,降水量的变化对枯水复杂度的变化不起关键作用,而径流惯性可能是引起枯水复杂度变化的重要因素。

As one of the important characteristics of low flow, the complexity of low flow has a significant role in the low flow studies. The time series of monthly runoff at Zhangjiashan（ZJS） station of the Jinghe River Basin during 1933-2010 was studied. The time series of low flow were determined based on the anomalies and the average standard deviation. The measure of approximate entropy（Ap En） was employed to analyze the complexity of low flow. Results show that： 1） The annual average runoff presents significant decreasing trend at the 0.01 level of significance. The low flow occurs more and more since 1997. The upper bound of monthly low flow at the ZJS station was determined to be 9 369.67×104m3. The occurrences of monthly low flows in January, February and December are much more than those in other months.Therefore, the monthly low flows in these three months were set as the time series of low flow in this study. 2） The value of Ap En of the low flow series was calculated to be 1.059 1, which is close to the value of 1.059 7 calculated from the entire monthly runoff series at the same time.It indicates that the fifteen non-dry months occurring in January, February and December have little impacts on the complexity of low flow series. 3） The complexity of monthly low flow showed increasing trend with fluctuations at the 0.05 level of significance. The complexity of low flow has a significant negative correlation to the monthly runoff, but has no significant relation to the monthly precipitation. The results demonstrate that the precipitation in the watershed is not the major input of the low flow system. The precipitation change does not play a key role in the change of the complexity of low flow. The runoff inertia is probably an important factor resulting in the change of the complexity of low flow.