Study On The Future Change Trend Of Water And Sediment In The Lower Yellow River

Due to the dual effects of climate change and human activities in recent years,the water and sediment of the Yellow River have decreased sharply,so it is necessary to make a reliable judgment on the future change trend.This paper takes the Yellow River Basin as the research area,uses the water and sediment measured data from Tongguan Station,an important hydrological station in the Yellow River Basin,the European Medium-term Weather Forecast Center reanalysis data set,and the global climate model data under different climate change paths under the CO₂emission concentration.A statistical model method based on a variety of machine learning features to predict the annual average value and change trend of water and sediment at Tongguan Station in the next ten,twenty,and fifty years.(1)The variation trend of water and sediment at Tongguan station is analyzed by linear tendency estimation,M-K trend test and other methods.From 1950 to 2016,the overall water and sediment trend was on the decline.The UF_K value and UB_K value of runoff intersect in 1993 and the intersection point is within the critical boundary(5%confidence interval),so it can be judged that 1993 is the abrupt runoff year.In 1996,the intersection point of sediment discharge was outside the boundary line,and 1993 point may be a sudden change point.(2)The prediction factors of the input model were selected by machine learning method,Among them,the climate factors that had a deep influence on runoff were surface air temperature,600h Pa potential,500h Pa radial wind,700h Pa air temperature and 300h Pa vertical wind.The climatic factors closely related to sediment transport are surface temperature,500h Pa specific humidity,net solar flux at the top of the atmosphere under the clear sky,net solar flux at the surface under the clear sky,net long wave flux at the top of the atmosphere under the clear sky,and net long wave flux at the surface under the clear sky.(3)Under the scenario of RCP26,the runoff of Tongguan station in the next 10,20 and50 years is 23.421 billion m³,22.752 billion m³ and 21.96 billion m³,compared with the average runoff of 22.886 billion m³ from 2000 to 2016,the runoff increases by about 2.3%,-0.5%and 4.0%.Compared with the average sediment transport of 248 million t from 2000to 2016,the predicted sediment transport of section is 268 million t,344 million t and 572million t,which increases by about 7.9%,38.4%and 130.2%,indicating that the situation of"less water and more sediment"in the Yellow River Basin will still be the main feature for a long period in the future.