近60年黄河中游水沙变化趋势及其影响因素分析

The Variation Trend of Streamflow and Sediment Flux in the Middle Reaches of Yellow River over the Past 60 Years and the Influencing Factors

采用线性回归、Mann-Kendall检验、双累积曲线及小波变换等方法系统分析了黄河中游干流及支流渭河、汾河和无定河的6个主要水文站(头道拐、龙门、花园口、华县、河津、白家川)1950s-2009年的水沙序列。在系统搜集流域基本信息的基础上,深入探讨流域水沙变化的特征及其驱动力。研究表明:黄河中游流量和输沙量呈现急剧减少趋势,尤其在20世纪70年代之后,减少更加显著,其中,汾河的水沙减少幅度最为显著,2000年-2009年的年均流量与输沙量相当于1950年-1959年约20%。干流龙门站流量和输沙量的小波变换在1980年代前表现出0.5～1.0a显著周期,且达到95%的置信度水平,之后周期特征减弱甚至消失。气候变化、降雨、水土保持措施(如退耕还林、草,梯田建设,水库淤地坝等工程)等人类活动是水沙变化的主要影响因素,其中,干流的头道拐和花园口水沙变化受干流水库影响较为显著。

The hydrological processes and sediment fluxes have been dramatically altered by large amount of dams’construction as well as reforestation in the Yellow River basin during the past several decades.Better understanding of the variations of streamflow and sediment flux in the Yellow River is greatly helpful for soil and water conservation,water resources planning and river basin management.This study has systematically analyzed the variations of streamflow and sediment flux in the Middle Reaches of Yellow River from 1950s to 2009 based on the observed data from 6 hydrological stations（Toudaoguai,Longmen,Huayuankou,Huaxian,Hejin and Baijiachuan）with linear regression,Mann-Kendall test,double mass curve method and wavelet transform.The results indicate that both runoff and sediment flux show significant decreasing trends,which are more evident after 1970s.Average annual streamflow and sediment flux during 2000 and 2009 are extremely low at Hejin station in Fen River,accounting for only 20%of those from 1950 to 1959.Being detected by double mass curve function,the abrupt changes of streamflow and sediment flux at Toudaoguai,Longmen and Huayuankou appeared in 1985 due to the operation of Longyangxia Dam.The significant wavelet spectrum of streamflow and sediment flux was mainly detected during 1950s and 1970s with a period of 0.5-1 year at confidence level of 95%,but later the periodicity features become more and more insignificant and even disappear.In summary,the reduction of streamflow and sediment flux is mainly caused by climate change,rainfall,soil and water conservation measures（such as afforestation,terraces,reservoirs and dams）and other human activities.Among these,reservoirs operation in the mainstream has great impacts on variations of water and sediment at the Toudaoguai and Huayuankou hydrological stations.