Study On Hydraulic Conductivity Of Wetland Sediment Of Bosten Lake

The hydraulic conductivity of sediment is a quantitative indicator of the capacity of water bodies to pass through the sediment,and it influences the conversion efficiency of surface water and groundwater.In arid regions,percolation process accelerates the exhaustion of water vol?mme in rivers and lakes.As the largest inland freshwater lake in China,Bosten Lake is the water source of Bayinguoleng Mongolian Autonomous Prefecture in Xinjiang.In recent decades,however,the dramatic increase in population in the prefecture,the gradual expansion of production scale,as well as the intensified shortage of water resource have led to ecological problems,such as cutoff in lower reaches,drying up of Lop Nor,salinization of lake water,desertification and decreased biological diversity.An in-depth study of permeability coefficient is conducive to understand the exchange process between surface water and groundwater in arid regions,improve the scientificity of water resource allocation and development,and alleviate the shortage of water.It is also beneficial to the conservation,recovery,and economic development of the lake ecosystem.In this paper,the Bosten Lake is taken as the research area and divided into three areas—the Great Lakes,the Small Lakes and Huangshuigou District.With riser test method,grain-size analysis method,the mass method and so forth to obtain sediment's hydraulic conductivity,grain size characteristics,porosity,total salt content and the like key information.Also,the spatial distribution,vertical distribution and influence mechanism of the hydraulic conductivity and related factors are studied with traditional statistical methods,geostatistical methods,principal component analysis,stepwise fitting method,etc.The research results are as follows:?1?The hydraulic conductivity ranges from 3.75 m·d^-11 to 39.12 m·d^-1,with an average of 17.90 m·d^-1,and it ranks as the Great Lakes>Huangshuigou District>the Small Lakes.The spatial autocorrelation is great,and the contribution rate of structural factors reaches up to 98.81%.?2?The sediment's grain size range from 28?m to 387?m,with an average of 149.39?m,of medi?m variation,showing a significant spatial differentiation as the Great Lakes>Huangshuigou District>the Small Lakes.The spatial autocorrelation is great,and the contribution rate of structural factors reaches up to 94.93%.The sediment is largely composed of clay,silt,fine sand and coarse sand,accounting for more than 99.99%,among which silt and fine sand outn?mmber others,accounting for 79.37%.The content of clay and silt in the research area shows significant spatial differences as the Great Lakes<Huangshuigou District<the Small Lakes,while the Small Lakes<Huangshuigou District<the Great Lakes as for the content of fine sand and coarse sand.Clay,silt and fine sand display significant spatial autocorrelation,and the random factors'contribution rate of spatial differentiation of the coarse sand reaches to 59.08%.?3?The sediment's porosity ranges from 43.26%to 55.97%,with an average of 48.94%,and that of the three areas ranks as the Great Lakes>Huangshuigou District>the Small Lakes.The spatial autocorrelation is great,and the contribution rate of structural factors reaches up to 89.18%.?4?The total salt content ranges from 4.42g·kg^-11 to 13.74g·kg^-1,with an average value of 8.28g·kg^-1,and most of the sediment have been salinized.In terms of the total salt content,it ranks like the Great Lakes>Huangshuigou District>the Small Lakes.The spatial autocorrelation is great,and the contribution rate of structural factors reaches up to 90.98%.?5?At the depths of0-10 cm,10-20 cm and 20-40 cm,the mean hydraulic conductivity value is 20.61m·d^-1,18.35 m·d^-11 and 14.71 m·d^-1,respectively,gradually decreasing with depth.The spatial autocorrelation of different depths is great,and the contribution rate of structural factors is more than 98.30%.?6?At depths of 0-10 cm,10-20 cm and 20-40cm,the sediment has the mean grain sizes of 169.94?m,154.22?m and 136.69?m,respectively,decreasing with depth increasing.In the spatial differentiation of various depths,the contribution rate of structural factors are all more than 94.32%.Clay and silt increase with depth,while fine sand and coarse sand decrease with depth.The sediment at different depths has the spatial distribution dominated by structural factors,but coarse sand,in the spatial differentiation of various depths,the contribution rate of random factors are all more than 53.61%.?7?At the depths of0-10 cm,10-20 cm and 20-40 cm,the porosities of sediment are 49.61%,49.06%and48.14%,respectively.Porosity decreases with depth.The spatial correlation of different depths is great,and the contribution rate of structural factors is more than88.43%.?8?At the depths of 0-10 cm,10-20 cm and 20-40 cm,the mean total salt values are 8.54g·kg^-1,8.31g·kg^-11 and 8.01g·kg^-1,respectively,steadily reducing with depth.The spatial autocorrelation of different depths is great,and the contribution rate of structural factors is more than 98.71%.?9?The correlation analysis revealed a strong correlation between elements and their relationship with hydraulic conductivity.?10?The principal component analysis found that porosity is the most critical factor that affects the hydraulic conductivity,with the contribution rate reaching up to 92.95%,so porosity is the main component.?11?Through stepwise regression analysis,it's shown that the fitting of the three models is quite good,and the linear function model R² reaches 0.93,based on which the expression of hydraulic conductivity and porosity is established.