黄河干流近70年来水沙关系变化

Variation of runoff and sediment load in the mainstream of the Yellow River over the past 70 years

为明确黄河干流径流输沙时空变化及水沙关系,采用线性回归、Mann-Kendall趋势检验法、累积距平法、水沙关系曲线和小波变换等方法分析黄河干流唐乃亥至高村区间的6个水文站近70年的径流输沙变化。结果表明:唐乃亥年径流量和输沙量呈非显著下降趋势,兰州、头道拐、龙门、花园口、高村站的年径流量和输沙量均呈显著下降趋势,且径流和输沙的减少量自上游向下游增加,趋势更加显著。黄河干流径流和输沙序列的突变大多数发生在1985年,主要是干流大型水利工程的调控所致。20世纪90年代以前,黄河干流月径流和输沙具有0.5~1、3~5和7~9年的周期性特征。不同时段的水沙关系曲线表明:黄河干流河道输沙特性发生明显变化。由于上游宁蒙河段泥沙淤积严重,头道拐站自1986年后泥沙供给增加18.2%,而水流挟沙能力下降8.3%;中下游站点1950—1999年,水沙关系存在较好的幂函数关系,但受小浪底水库调水调沙的影响,下游花园口、高村站2000—2017年水沙关系曲线较之前发生明显变化,幂函数关系消失。水土保持措施实施和大型水利工程运行是改变黄河干流水沙关系的主要原因。

[Background]Runoff and sediment load play an important role in development and utilization of water resources,shaping the river morphology,maintaining river ecological system.The runoff and sediment load in the Yellow River have decreased greatly in the past several decades because of climate change and anthropogenic influences.Better understanding the spatial-temporal variation in runoff and sediment load and their relationship in the mainstream of the Yellow River can provide good reference for watershed management and soil and water conservation.[Methods]This study attempted to investigate the changes of runoff and sediment load at 6 hydrological stations along the mainstream of the Yellow River from 1950 to 2017.The linear-regression analysis,the non-parametric Mann-Kendall test,the accumulative annual anomaly,the flow-sediment curve and wavelet transform were employed for investigation.[Results]Annual runoff and sediment load at Tangnaihai station showed a non-significant downward trend,whereas annual runoff and sediment load at Lanzhou,Toudaoguai,Longmen,Huayuankou and Gaocun stations showed significant decreasing trends(P<0.05).The annual streamflow exhibited the most significant decrease at Gaocun station with average reduction rate of-5.12×108 m3/a,while the streamflow at Tangnaihai station showed gently decrease(-0.21×108 m3/a).Positive correlation between runoff and sediment load was examined at all the stations before 2000.A abrupt changes of annual runoff and sediment load were examined in 1985.A periodical fluctuation of 0.5-1,3-5,and 7-9 years was detected before the 1990s.Flow-sediment curve showed that sediment supply from upstream of Toudaoguai station had increased 18.2%since 1986 due to severe siltation in the mainstream section of Ningxia and Inner Mongolia,but the sediment transport capacity had decreased 8.3%.The construction of Xiaolangdi Reservoir altered the exponential relationship between flow and sediment at its downstream stations(Huayuankou and Gaocun)after 2000.[Conculsions]Large-scale hydraulic projects,soil and water conservation and water withdrawal by agriculture and industry are the dominant causes for significant reduction in runoff and sediment load in the mainstream of the Yellow River.