黄河流域主要泥沙汇堆积过程及输沙量的长期变化

Changes of Siltation in Main Sediment Sinks and Sediment Load of the Yellow River

黄河流域是地表巨大的输沙系统之一,受气候变化和人类活动的影响,其输沙量经历了显著的变化。探讨了全新世以来黄河流域3个主要泥沙沉积汇的堆积变化过程以及黄河输沙量的变化过程,揭示出在人类活动逐渐增强的主要影响下,宋代以后黄河输沙量经历了加速增加的过程,近几十年来在气候变化以及水利水保措施作用下黄河输沙量又经历了逐渐减少的过程。与历史时期相比,近年来黄土高原坡面和沟道的侵蚀产沙量仍较大,仍需长期开展水土保持工作。20世纪中期以前,由于黄河输沙量逐渐增加,因此黄河下游与渭河盆地及小北干流年沉积量也都呈现一个逐渐加速的过程,两者沉积量年增加的比例比较接近,与黄河输沙量年增加的比例一致。近几十年来,下游主要受大堤防洪能力及来沙变化影响、渭河盆地及小北干流主要受三门峡水库水位和来沙变化影响,年沉积量起伏变化,2003年以来两泥沙汇都发生了持续冲刷过程。河套平原是黄河上游最大的泥沙汇,1949年以前400多a的平均沉积量接近0.9亿t/a,1950年以来年均沉积量较之前长期平均值高,受来沙系数变化影响,经历了两个起伏周期,近期进入低谷。

The Yellow River is one of the gigantic sediment delivery systems on the earth. Its sediment load has experienced obvious changes owing to climate change and human interferences. This study investigated the changes of siltation in three principal sediment sinks and of sediment load of the river in the Holocene. It was displayed that the sediment load of the river had undergone an accelerating increase after the Song Dynasty mainly resulting from a gradual enhancement of human activities and a decrease tendency in recent decades as a result of climate change and soil erosion control and water conservation practices. Compared with that in the historical periods,the sediment yield from the slopes and gullies in the Loess Plateau was still heavier in recent years,demanding the continual implementation of soil erosion control measures. Before the middle of the 20th century,siltation in two sediment sinks （including the lower Yellow River and the lower Weihe River and the Xiaobeiganliu segment of the Yellow River located in the Fen-Wei graben basin）showed an increase trend accompanying with the accelerating increase of the river’s load. The annual percentage increase rates of siltation in the two sinks were nearly the same and close to that of the river’s load. In recent decades,siltation rates in the two sediment sinks undulated due to the promotion of flood control capacity of artificial levees and changes in sediment load in the lower Yellow River and due to the changes in pool level of Sanmenxia Dam and in the river’s load in the lower Weihe River and the Xiaobeiganliu segment of the Yellow River. The sediment storage in the two sinks had continuously decreased since 2003. The Hetao plain is the largest sediment sink in the up-per reaches. Siltation in the sink was approximately 90 million tons annually on average of over 400 years before 1949. In over 50 years since 1950, the mean siltation rate in the sink was higher than that before and rose and fell for two cycles due to the changes in incoming sediment coefficient. It was low in recent years.