Study On The Aeolian Sand Amount Into The Yellow River In Shizuishan And Bayangaol Hydrological Stations

The Tengger Desert,the Ulan Buh Desert,the Hobq Desert and the Mu Us Sandy Land,in the upper reaches of the Yellow River,has a certain amount of sand entering the Yellow River and participating in the evolution of the river every year.The river channel evolution mechanism under the combined action of wind and water sand is an important scientific issue in the discipline of riverbed evolution,and it is.also a key issue restricting the development and utilization of river channel in the upper reaches of the Yellow River.Since the 1980s,many researchers have carried out the research on the process of the sand entering the yellow river and the amount of the sand,but limited to the observation technology,the length of observation and the systematic and continuous observation,the results of research is still controversial.This paper takes Ulan B'uh Desert as the object of the research,studying the sand of Ulan Buh Desert entering the Yellow River,with the method of sampling data analysis,remote sensing image interpretation,field system observation,model calculation,etc.This paper has analyzed the characteristics of water and sediment from Shizuishan to Bayangaol,and obtained the data of sandstorm movement through field observation,described the law of sand wind movement,calculated the amount of sa.nd entering the Yellow River from 2013 to 2016.It also analyzed the long-term variation law of various influencing factors affecting sand into the yellow river,made qualitative analysis of the amount of sand entering the Yellow Rive for a long time,established the model of sand entering the yellow river and calculated the amount of sand into the river since 1980s,using the water level of the Sakaguchi hydrological station,and the topographic data of 1967 and 2012.The main conclusions obtained are as follows:(1)Since the 1950s,the water and sediment from Shizuishan to Bayangaol have generally decreased.Since 1970s,the water and sediment reduction trend is more significant,and the reduction of sediment load is greater than the decrease of runoff.The particle size of desert sand is mainly larger than 0.1mm.The content of coarse particles(particles larger than 0.1mm)at the entrance and exit of the river section is basically close to that of sediment load.The average difference(1961-2014)is 759300 tons.The change of bed material size in the section of the river is similar to that in the entrance and exit,which indicates that the channel is not affected by wind and sand.(2)The dunes along the Ulan Buh Desert are mainly crescent-shaped dunes and crescent-shaped dune chains.The dune along the left bank of the river is 46.35km long,the semi-fixed dune is 12.1km long,and the fixed dune is 3.97.Km,there is a good correlation between the width of the dunes,the speed of movement and the height of the dunes.(3)The vegetation coverage of the entire Ningxia-Inner Mongolia River has increased from 10.9%in 1990 to 16.5%in 2010,and the vegetation cover in Ulan Buh Desert has increased to 11.29%.Urban land,industrial land and mining land from Shizuishan to Bayangaol increased significantly in 2013 and beyond,and the proportion of desert area decreased from 72.76%in 2000 to 52.12%in 2015.(4)The meteorological data of four national meteorological stations near the study area and the two local meteorological stations in Wuhai and Dengkou show that since the mid-1990s,the maximum wind speed has dropped by 8?9m/s,and the maximum wind speed has dropped by 5?10m/s.The annual average wind speed has dropped by 1.1?1.7m/s,so the sandstorm weather and the frequency of sandstorms in the region have shown a significant downward trend.(5)By measuring the sediment load in the range of 0-60cm in the near surface,the results show that the sediment transport volume of the study area is 81.75%concentrated in 0-10cm,and the sediment load above 30cm is less than 7%on average.Silt discharge has a power function to the ground heights.(6)Having evaluated the amount of sand in the different periods,from 2013 to 2016,the amount of sand entering Yellow River in Ulan Buh Desert was 1.5892 million t/yr,927,400 t/yr,556100 t/yr and 537800 t/yr,respectively.From 1954 to 2016,the annual average amount of sand was 3.5378million tons,and the maximum value was 5.8661million tons in 1987.The minimum value was 537,800 tons in 2016.Under the set scenario model,with the improvement of land use types,the amount of sand entering the Yellow River will decrease to 2624500 t/yr from 2031 to 2036.(7)The paper has analyzed the amount of sand in Sanshenggong Reservoir Area using the cross section method,sand volume method,scouring and silting capacity and the field observation.According to the comprehensive analysis,the amount of sand entering the Sanshenggong Reservoir area is about 700000?1000000 t.