The Yellow River Water and Sediment Regulation

The main reason of aggradation happened in the lower Yellow River is because of less runoff, too much sediment and unbalanced amount of water and sediment. According to the law of scouring and deposition of the channel, it can totally avoid that situation in the lower reaches if only to regulate the unbalanced relationship of water and sediment in the lower reaches into a balanced relationship. The Xiaolangdi Reservoir built on the Yellow River and completed by the end of 2001 has powerful functions to regulate the unbalanced relationship of water and sediment. The Xiaolangdi Reservoir is situated on the key position where can control the water and sediment entering into the lower reaches. It has controlled 91% of the river runoff and almost 100% of the river sediment. The discharge controlled at Huayuankou cross section during the first water and sediment regulation test conducted in the Yellow River is 2 600 m 3/s, the mean outlet sediment concentration less than 20 kg/m 3 and duration is 11 days. In the test, it has totally flushed out 36.2 million tons of sediment and achieved the desired purpose. Through the test, we have collected 5.2 million sets of data and have a better understanding on the laws of riverbed evolution, water and sediment. It has provided extremely important physical parameters for establishing a mathematical model and a physical model that will further tally with the actual real river in the future. It is shown by the test that it is one of the effective way to be beneficial for delivering sediment into the sea, reduce aggradation of the lower river channel and even scour the lower river channel to regulate the unbalanced relationship of water and sediment into a balanced relationship by using a reservoir for water and sediment regulation.