The Spatial Pattern Of Salt And Simulation Of Water And Salt Transport In Dry Lake Bed Based On Remote Sensing And Hydrus Model

The dry lake bed is a secondary desert landscape with high surface salt content and high dynamic change,which is formed by natural conditions and human activities and other factors.It has a serious impact on the regional ecological environment and human well-being.Understanding the spatial distribution characteristics of salinity in dry lake beds and the laws of water and salt transport in surface soil are of great significance for ecological restoration and prevention of natural disasters.The goals of this paper were to use remote sensed images(Landsat8 OLI)to develop regression model for estimating soil salinity in the dry lake bed of the Qehan Lake;clarify the spatial distribution of salt in the dry lake bed of the Qehan Lake and make attempts to analyze the possible sources of salt;discuss the effect of surface temperature and humidity on salt distribution;The HYDRUS model was used to simulate the water and salt transport in the vegetation root zone(0-40cm)in the vegetation area and bare land area;the laws of water and salt transport in surface soil were obtained.The results showed that the soil brightness index(BI)had a good correlation with the measured conductivity,and the Pearson correlation coefficient(R)=0.7.The developed linear statistical model could be successfully applied to evaluate the soil salinity,determination coefficient R~2=0.62071 and root-mean-square error RMSE=1.61702.The simulation results using the HYDRUS model are good.The water simulation accuracy R~2 is 0.7138-0.97254 and the RMSE is0.00395-0.01341(%).The salt precision R~2 is 0.67921-0.99352,and the RMSE is 1.11094-24.28(dS/m).The simulation result is accurate.Thus,we obtained the salt spatial distribution characteristics of dry lake bed in the Qehan Lake:Low salt in the middle of the lake bed,high salt around the dry lake bed.The strong salinization area is mainly distributed in the eastern,western and southern parts of the lake bed,with a band distribution between the lake bank and the vegetation belt.This spatial distribution of salt may be related to the control of groundwater depth and topography.According to the geomorphological characteristics of the study area,the salt may come from the Abaga Lava Platform in the north and the Otindag Sandy Land in the south.Surface water content was negatively correlated with surface moisture,and there was no significant correlation with surface temperature.The higher the surface water content,the lower the salt content.The change of moisture and salinity in the root zone was highly consistent with the rainfall trend.After the rainfall event,the soil salinity decreased rapidly,and then it gradually increased.The rate of soil salinity increase may be related to the intensity of evaporation.The water and salinity of lake bed changed significantly during the season.In the summer and autumn alternate seasons,the water content in the surface of the lake bed gradually decreased,the salt content gradually increased,and the unsaturated water fall rate gradually decreased.The results of this study can provide scientific basis for the ecological restoration of dry lake beds in the Qehan Lake,and provide theoretical support and programs for the monitoring of salinity in wetlands in arid areas,and provide a scientific reference for the process of water and salt migration of dry lake bed in arid area.