黄土高原典型流域次洪事件水沙关系变化及其驱动因素

Variation of Runoff-Sediment Relationship at Flood Event Scale in Typical Watersheds of the Loess Plateau

[目的]探究黄土高原典型流域次洪事件水沙关系变化,探讨水土保持综合治理对流域水沙关系的调控,以期为黄土高原地区未来的生态恢复与水土保持综合治理提供参考。[方法]基于孤山川、佳芦河和西川河流域1974—1989年和2007—2019年的洪水水文要素资料,采用线性函数分析了流域不同时期水沙关系变化特征,采用皮尔逊相关系数法探讨了径流指标(年径流深、平均洪峰流量和平均流量)和输沙指标(年输沙量、平均最大含沙量和平均含沙量)间的相关性,辨析了不同流域水沙变化的驱动因素。[结果]2007—2019年各流域次洪事件的年均径流深和年均输沙量较1974—1989年均显著减少(p<0.05),孤山川流域变化最大,分别减少56.48%,95.03%;佳芦河流域的年均输沙量变化不明显且年均径流深有所增加,主要由于该流域植被覆盖较差、水土保持措施治理占流域比例小,加之近年来极端降雨量增加。[结论]各流域的水沙关系在经过水土保持综合治理后发生显著变化,径流深-输沙模数线性关系减弱,黄土高原水土保持措施的实施尤其是大规模植被恢复使流域产输沙能力下降,从而导致径流和输沙变化的不同步。

[Objective]The aim of this study is to explore the changes of runoff-sediment relationship at flood event scale in typical watersheds of the Loess Plateau,to discuss the regulation of runoff-sediment relationship by comprehensive management of soil and water conservation,and to provide reference for future ecological restoration and comprehensive management of soil and water conservation in the Loess Plateau.[Methods]We selected the Gushanchuan,Jialuhe and Xichuanhe watershed to explore the changes of runoff-sediment relationship at flood event scale in three watersheds.Based on their flood event data of 1974—1989 and 2007—2019,a linear model was used to analyze the changes of runoff-sediment relationship in different periods of three watersheds,the Pearson correlation coefficient method was used to investigate the correlation of runoff and sediment-related variables,and the driving factors of runoff-sediment relationship change in each watershed were identified.[Results]The runoff depths and sediment yields of flood events in 2007—2019 of each watershed significantly reduced(p<0.05)compared with 1974—1989,and the greatest changes were observed in the Gushanchuan watershed,with a decrease of 56.48%and 95.03%,respectively.The change in the amount of sediment yield in the Jialuhe watershed was not obvious and the increase in runoff depth was mainly due to the low degree of vegetation restoration in the watershed,the relatively low impact of soil and water conservation measures,and the increase of rainfall in recent years.[Conclusion]After the implementation of soil and water conservation measures,the runoff-sediment relationship of each watershed had changed significantly,and the linear relationship between runoff depth and sediment yield had weakened,which was due to the implementation of soil and water conservation measures on the Loess Plateau,especially the large-scale vegetation restoration,which had reduced the sediment production and transportation capacity of the unit runoff depth in the watersheds,and resulting in the reduction of sediment into the Yellow River.