水系连通功能变异下荆南三口流域径流特征

Runoff Characteristics in the Three Outlets of Southern Jingjiang River Based on the Variation of Water System Connection Function

为了探究水系连通功能对流域径流的影响,以荆南三口流域为研究对象,运用模糊综合评判法对水系连通功能进行评判,采用月径流占年径流百分比、年内分配不均匀系数、Morlet小波分析、Sen′s slope等方法,定量分析了水系连通功能变异下荆南三口流域径流特征变化。结果表明:(1)荆南三口流域水系连通功能由1956年为Ⅰ级变为1989年为Ⅲ级再到2008年Ⅱ级,2016年保持为Ⅱ级,1989年为水系连通功能变异年,变异前后河道断流率等指标存在差异,变异后大于变异前。(2)水系连通功能变异下荆南三口流域月径流占年径流百分比更加集中在丰水月份,年内分配不均匀系数增加,表明径流年内分配更加不均匀,易造成旱涝灾害。(3)水系连通功能变异下径流序列演变过程存在的周期变化尺度由3~6 a,7~18 a,22~32 a变为3~6 a,7~8 a,9~12 a,13~16 a,第一主周期缩小12~13 a、第二主周期缩小3~4 a、第三主周期缩小1~2 a,径流丰枯震荡次数增加1~4次,表明荆南三口流域径流发生丰枯交替的频率明显。(4)水系连通功能变异下荆南三口流域径流趋势变化发生不同程度的改变,松滋河西支、松滋河东支、虎渡河径流、藕池河西支减少趋势显著,松滋河西支减弱速率较快,松滋河东支、藕池河西支减弱速率减慢,虎渡河径流减弱速率稍增加,藕池河东支无显著变化。

In order to investigate the influence of the connectivity of the river system on the runoff of the river basin,taking the three Outlets of Southern Jingjiang River Basin as the research object,we used the fuzzy comprehensive assessment method to evaluate the connectivity of the river system,and used the monthly runoff accounted for the annual runoff percentage,the annual uneven distribution coefficient,Morlet wavelet analysis,Sen′s slope and other methods to quantitatively analyze the runoff characteristics of the three Outlets of Southern Jingjiang River Basin under the variation of the connectivity of the water system.The results showed that:(1)the connectivity of the water system of the three Outlets of Southern Jingjiang River-watershed changed from Grade I in 1956 to GradeⅢin 1989 to GradeⅡin 2008,remained GradeⅡin 2016,and the year of 1989 was the year of variation in the connectivity of the water system;before and after the variation,there were differences in indicators such as the channel cutoff rate,channel cutoff rate after the variation was greater than before the variation;(2)under the variation of the connectivity function of the river system,the monthly runoff percentage of the annual runoff in the three Outlets of Southern Jingjiang River was more concentrated in the flood months,and the coefficient of uneven distribution during the year increased,indicating that the distribution of runoff during the year was more uneven,which was likely to cause drought and flood disasters;(3)the periodic change scale of the runoff sequence evolution process under the variation of the connectivity of the water system changed from 3~6 years,7~18 years,22~32 years to 3~6 years,7~8 years,9~12 years,13~16 years,and the first main cycle reduced from 12 to 13 years,the second main period reduced by 3 to 4 yrears,and the third main period reduced by 1 to 2 years;the number of runoff shocks increased by 1 to 4 times,indicating that the frequency of runoff alternation between three Outlets of Southern Jingjiang River watershed was obvious;(4)the runoff trend of the three Outlets of Southern Jingjiang River watershed changed to various degrees under the variation of the connectivity of the river system;runoff of the Songzi River West Branch,the Songzi River East Branch,the Hudu River Runoff,and the Wuchi River West Branch decreased significantly,and the runoff reduction rate of Songzi River West Branch was faster;The runoff reduction rates of the eastern branch of the Songzi River and the western branch of the Muchi River slowed down,and the runoff reduction rate of the runoff of the Hudu River increased slightly,but there was no significant change in the eastern branch of the Muchi River.