黄河上游黄土高原入黄沙量变化分析

Analysis of Changes in Sediment Inflow of the Loess Plateau into the Yellow River in the Upper Reaches of the Yellow River

早在20世纪70年代黄河上游实测输沙量就开始大幅减少,其中黄河下河沿站1970—1999年和2000—2022年年均输沙量分别较天然时期减少50%、76%,但迄今有关该区沙量锐减的研究极少。以黄河李家峡大坝至青铜峡区间的黄土高原为重点,分析了该区水沙和有效降雨变化情况、水库和淤地坝在不同时期的拦沙作用,还原了1960年以来流域实际产沙量,研究了梯田和植被变化情况,计算了现状下垫面在设计降雨情景下的产沙量。研究结果表明:20世纪后期水库拦沙是研究区输沙量大幅减少的主要原因,2000年以来梯田建设和植被改善逐渐成为主要减沙因素、水库拦沙次之;基于2021年下垫面推算的下河沿以上产沙能力为5800万~6600万t/a、较天然时期降低约62%,清水河流域产沙能力为1920万~2743万t/a、较天然时期降低约53%;未来植被改善潜力很小,新建梯田仅可弥补老旧梯田田埂损毁的负面影响,因此产沙能力进一步降低的潜力极小。

As early as the 1970s,the measured sediment discharge in the upper reaches of the Yellow River had been decreased significantly,and the measured sediment discharge at the Xiaheyan Station had been decreased by 50%from 1970 to 1999 and 76%from 2000 to 2022 respectively.However,there has been very little research on the dramatic decrease in sediment discharge in this area so far.This article focused on the Loess Plateau between Lijiaxia and Qingtongxia of the Yellow River Basin,analyzed the changes in streamflow,sediment load and effective rainfall,the sediment trapping effects of reservoirs and warping dams in different periods,and restored the actual sediment yield since 1960.The changing processes and trends of terrace and vegetation were studied,and the sediment yield of the current underlying surface under the designed rainfall scenarios was calculated.The results show that reservoir sediment containment is the main reason for the significant decrease of sediment transport in the late 20th century.Since 2000,terrace and vegetation have gradually become the main factors for sediment reduction,followed by reservoir sediment containment.Based on the underlying surface in 2021,the sediment yield capacity above the Xiaheyan Station of the study area is 58-66 million t/a,which is about 62%lower than that of the natural period.The sediment yield capacity of the Qingshui River basin is 19.20-27.43 million t/a,which is about 53%lower than that of the natural period.In the future,due to the limited potential for vegetation improvement and the fact that new terraces can only compensate for the negative impact of damaged old terraces,the potential for further reduction in sediment yield capacity is minimal.