| Coordinating the relationship between water and sand is an important measure to promote the ecological protection and high-quality development of the Yellow River Basin,and quantitatively analyzing the corresponding relationship between the driving factors affecting the changes of water and sand in the Yellow River and the temporal and spatial changes between the water and sand of the Yellow River can provide a scientific basis for the spatial allocation of the overall ecological governance of the river basin.In this paper,taking16 hydrological stations in the main stream of the Yellow River Basin as the research object,the Gini coefficient of land use,the Lorentz asymmetry coefficient and the coefficient of variation were calculated by calculating runoff,sediment transport,rainfall,NPP,NDVI,Gini coefficient of land use,Lorentz asymmetry coefficient and coefficient of variation,and the M-K trend analysis and mutation test were carried out.Principal component regression and correlation analysis were used to study the spatio-temporal correspondence between the Yellow River water and sand and its driver factor inefficiencies.Studies have shown that:(1)From 1955 to 2015,the runoff of the Yellow River Basin decreased by 54.63%,the amount of sand transport decreased by 96.30%,and the spatial and temporal distribution of sand transport was significantly higher than that of runoff.In terms of time distribution,the unevenness of runoff showed a downward trend year by year with time,and the mutation year appeared in 1985,with obvious seasonal changes,and the unevenness of runoff was mainly concentrated in July-October.The uneven distribution of sand transport showed an increasing trend with time,the mutation year appeared in 1996,and the uneven amount of sand transport during the year was mainly concentrated in July to September.In terms of spatial distribution,the uneven distribution of runoff in the basin gradually increases with the upstream-downstream interval,and the areas with strong inequity are mainly concentrated in the downstream Garden Mouth-Lijin Station,and the areas with uneven sand transportation are mainly concentrated in the section of Dengkou-Longmen Station.(2)The results of the double accumulation curve of the main stream of the Yellow River show that the transition years of each station are mostly concentrated around 1970 and 2000,and the slope of the accumulation curve of all stations is significantly reduced,indicating that the amount of sand transport in the main stream of the Yellow River has been controlled to a certain extent,and the consistency of sand transport with the change of runoff is strong.The multi-year average sand coefficient of the main stream of the Yellow River showed a trend of increasing along the course from upstream to downstream,and the sediment content per unit flow was large,and the siltation capacity of the river increased.(3)The differentiation rules of the driving factors in the Yellow River Basin are also different.The NPP and NDVI in the Yellow River Basin showed a trend of slow decline and significant increase,which is related to the vigorous implementation of the project of returning farmland to forests and grasslands in the Loess Plateau around 2000,and the vegetation cover in the Yellow River Basin has experienced a large decrease and gradual recovery trend during this period.And the areas with strong inequality are mainly concentrated in the upper and middle reaches of the Yellow River Basin.According to the Lorentz curve of land use location entropy,the uneven distribution of land types in the entire basin is grassland < waters< forest land< arable land< urban and rural areas,industrial and mining,residential land < unused land in all years.That is,the uniformity of grassland,water and woodland is the best in the uniformity of the distribution of land types.The rainfall in the Yellow River Basin changes in stages with time,and the Gini coefficient range is mainly distributed between 0.5–0.6,the overall degree of inequity is strong,and the uneven distribution during the year is mainly concentrated in summer.In terms of spatial distribution,the degree of inequality in the west is significantly higher than that in the eastern part of the basin.(4)Through principal component regression,it can be concluded that the main factors that play a positive correlation with the change of runoff in the Yellow River Basin are mainly forest land and NPP,and the negative correlation is mainly in water,urban and rural areas,industrial and mining,and residential land;the driving factors that play a positive correlation role in the sediment transport volume in the Yellow River Basin are cultivated land and rainfall from large to small,and the driving factors that play a negative correlation role are grassland and unused land from large to small.The main cause of the water and sand changes in the Yellow River is the change in the land use structure caused by human activities.In the study of spatial and temporal differentiation correspondence between the yellow river water and sand and its driving factors,the NDVI was significantly negatively correlated with the change of runoff unevenness on the time scale,and the rest were not significantly positive correlation;rainfall and NDVI were significantly positively correlated with the uneven distribution of sand transport.At the spatial scale,the most consistent with the uneven distribution trend of runoff is rainfall and NPP,and the degree of variation of sediment transport is most similar to that of NPP.Moreover,the spatial differentiation law of runoff and sediment transport has always been closely related. |
