Sediment flux into the sea as influenced by the changing human activities and precipitation: example of the Huanghe River, China

Since the 1970s,the sediment flux of the Huanghe River into the sea has shown a marked tendency of decrease,which is unfavor able to the wetland protection and oil extraction in the Huanghe River Delta.Thus,effort is made to elucidate the relation between the sediment flux into the sea and the drainage basin factors including climate and human activities.The results show that the sediment flux into the sea responds to the changed precipitation in different ways for different water and sediment producing areas in the drainage basin.Other factors are given as constant,when the annual precipitation in the area between Longmen and Sanmenx ia decreases by 10 mm,the sediment flux into the sea will decrease by 27.5 Mt/a;when the precipitation in the area between Hekouzhen and Longmen decreases by 10 mm,the sediment flux into the sea will decrease by 14.3 Mt/a;when the precipitation in the area above Lanzhou decreases by 10 mm,the sediment flux into the sea will decrease by 17.4 Mt/a.Amultiple regression equation has been established between the sediment flux into the sea and the influencing factors,such as the area of terrace land building and tree-and grass-planting,the area of the land created by the sediment trapped by checkdams,the annual precipitation and the annual quantity of water diversion by man.The equation may be used to estimate the change in the sediment flux into the sea when the influencing variables are further changed,to provide useful knowledge for the environmental planning of the Huanghe River drainage basin and its delta.