Study On Index System And Threshold Value Of Sediment Dynamic Regulation And Control For Key Hydro Junction Groups In The Main And Tributaries Of The Yellow River

The Yellow River is a famous river with high sediment content in China and even in the world.It is characterized by less water and more sediment.Since ancient times,the Yellow River is the mother river for our people's survival,but it is also one of the rivers with the most disasters.In this paper,using the method of the analysis of the measured data of the Yellow River,this paper first studies the Ningmeng reach in the upper reaches of the Yellow River,the reach of the Xiaobei main stream in the middle reaches of the Yellow River and the lower reaches of the Yellow River According to the analysis of the characteristics of water and sediment variation,it is found that the annual inflow and sediment amount and the large discharge level inflow are generally reduced in each reach of the Yellow River,and there are different degrees of shrinkage of the main channel,siltation,reduction of the flow and sediment transport capacity of the river channel,resulting in flood drought and ice jam.These phenomena are mainly determined by the disharmony of water and sediment,the imbalance of water and sediment between years and within years,and high sediment concentration,which cause serious threat and loss of life and property to the Yellow River Basin.Secondly,the threshold analysis of flood control and ice prevention control index,threshold analysis of water and sediment transport function regulation index and threshold analysis of water and sediment resource allocation regulation index are carried out for each reach of the Yellow River The threshold indexes which can maintain and shape the healthy water and sediment transport of the Yellow River in the future are put forward.So as to provide scientific and technological support for the Yellow River to regulate and control the water sediment relationship entering the downstream by using the main and branch reservoirs,and to shape a relatively coordinated water sediment relationship.The results are as follows:1.According to the characteristics of water and sediment of the Yellow River,the sediment dynamic regulation index system of the backbone hub group of the main and tributaries of the Yellow River is preliminarily constructed from four levels of different reaches,different functional systems,the most important control indexes and the regulation indexes along the river;2.The characteristics of water and sediment variation in the Ningmeng reach are as follows:the distribution of water and sediment is not coordinated,the water and sediment are different sources,the annual distribution of water and sediment is uneven,and the water and sediment are not uniform In recent years,the water and sediment transport is mainly concentrated in 500?3000 m~3/s discharge level.In order to avoid further siltation and shrinkage in Ningmeng reach,the threshold value of water and sediment transport function regulation index is determined as follows:discharge 2000m~3/s?2500 m~3/s,sediment concentration no more than 10kg/m~3,incoming sediment coefficient less than 0.004 kg.s/m~6.3.The characteristics of runoff and sediment variation in the middle reaches of Xiaobei main stream are as follows:the annual distribution of incoming water and sediment is uneven;the interannual distribution of incoming water and sediment is uneven,especially since 1987;since 1987,the inflow and sediment amount of Xiaobei main stream has shown a relatively obvious decreasing trend;since 1987,the probability of small discharge in Xiaobei main stream has increased significantly,and the probability of large discharge has decreased obviously;the probability of small discharge in Xiaobei main stream has increased significantly,and the probability of large discharge has decreased obviously;the probability of small discharge in Xiaobei main stream has decreased The annual average sediment concentration also varies greatly from year to year.The threshold value of water and sediment transport function in Xiaobei main stream is determined as follows:the discharge is about 2500 m~3/s,the incoming sediment coefficient is about 0.013 kg·s/m~6,Sanmenxia reservoir is used for storing clear water and discharging muddy water,and the average operating water level is 315m in flood season and non flood season(the maximum operating water level is not more than 318m).Under this condition,the channel of Xiaobei main stream will not be silted up and the elevation of Tongguan will not be raised.4.The characteristics of water and sediment variation in the lower reaches of the Yellow River are as follows:the annual distribution of water and sediment is not uniform;the distribution of water and sediment in the lower reaches of the Yellow River is uneven;the decrease of water and sediment before 1986 basically does not damage the water and sediment collocation relationship of the lower Yellow River,but after1986,the water and sediment matching relationship has been significantly improved since 2003;in recent years,the water and sediment transport in the lower Yellow River mainly concentrated in 1000?4000 m~3/s flood.The threshold value of the regulation index of water and sediment transport function in the lower reaches of the Yellow River is determined as follows:the incoming sediment coefficient is not more than 0.01kg.s/m~6,the sediment concentration is below 25.5kg/m~3,the average water volume in flood season is more than 10.5 billion m~3,and the discharge is about 4000 m~3/s.