WATER DEMAND FOR SEDIMENT TRANSPORT CAN BE GREATLY REDUCED AFTER THE CONSTRUCTION OF XIAOLANGDI RE SERVOIR

摘要

After several generations’research and engineering practice in our country， there is a major breakthrough in the knowledge and understanding on sediment transport of the Yellow River，i.e.use the hyperconcentrated flood to transport sediment to sea.This method can not only reduce the water demand for sediment transport，but also control river channel aggradation，which serves as a prosperous solution for flood control of lower Yellow River.By the multi-year regulation operation of sediment in Xiaolangdi Reservoir， hyperconcentrated flood with higher discharge makes it possible to transport large quantity of sediment to sea，which is an efficient technical measure to alleviate sedimentation problem in the lower Yellow River.Under a tight water resources budget，especially in mean or low runoff years，all the outflow from Xiaolangdi Reservoir can be used for municipal and environmental purpose，not for flushing out the bottom sediment.The computational results based on measured data from 1970 to 1996 indicate that when the initial deposited sediment volume in the regervoir is around 3 billion m3，there is a greater opportunity for erosion on the downstream river bed， but the erosion efficiency is low. However，when the initial deposited sediment volume in the reservoir reaches 6 billion m3， the opportunity for downstream erosion is low，but the erosion efficiency is high，and more sediment can be saved for transportation during flood season.Under such condition，the average annual water demand for sediment transport is around 4.3 billion m3，ranging from 12.8 million for high flow year，to 1.6 billion m3 for low flow year.Therefore，by using hyperconcentrated flood for sediment transport，the conflict of water demand between sediment transport and industrial and agricultural use of the lower Yellow River can be completely resolved.