VARIATION OF SEDIMENT LOAD AT THE MAJOR TRIBUTARIES IN THE MIDDLE REACHES OF YELLOW RIVER AND ITS IMPACTS ON THE SEDIMENT FLUX TO THE SEA

The loess plateau plays a critical role in the sediment budget of Huanghe River and its flux to the sea.Here in this paper,we studied the variations in annual water discharge and sediment load in seven main tributaries in the middle reach of the Huanghe River.Annual water and sediment data have been acquired from seven major hydrographic stations for 7 tributaries(Huangfuchuan River,Kuyehe River,Wudinghe River,Yanhe River,Beiluohe River,Jinghe River and Weihe River) and the Tonguan Station in the middle reach of the Huanghe River in 1950-2009.Besides,we studied the annual sediment load of the seven major tributaries and several hydrological stations in the mainstream(Tongguan and Lijin).The results indicate that the annual water discharge and sediment load decreased sharply over the past 60 years,the total sediment loads have dropped from 13.5 108t/a in 1950s-1960s to only 3.4 108t/a in 2000-2009,with a reduction of about 75%.Time series data of sediment loads from the major tributaries and Lijin station indicate that tributaries in the loess plateau played a dominant role in the decrease in Huanghe sediment flux to the sea,while the rapid increases in water consumption and redistribution in the low reaches sinc the 1980s accelerated the reduction of sediment flux to the sea.