Study On The Influence Of Wind Speed On The Phreatic Water Evaporation In Mu Us Sandy Land

Dry Sand Layer?DSL?is often formed on the surface under strong solar radiation in arid and semi-arid desert regions in China,which can inhibit the evaporation of the water in vadose zone and phreatic water.Wind can promote the evaporation of phreatic water in shallow groundwater areas,it is of great theoretical and practical significance to study the influence of wind on phreatic water evaporation under different groundwater tables for reveal groundwater evaporation mechanism and groundwater resource evaluation in arid and semi-arid regions.In this paper,take aeolian sand in the Mu Us sandy land as a research object,based on Soil Hydrodynamics,Soil Moisture Thermodynamics,Hydrogeology and other theories,combined the indoor experiment,field monitoring and numerical simulation to study the influence of different wind on phreatic water evaporation under different groundwater tables.Some achievements were obtained as follows:Firstly,modified phreatic water evaporation empirical formula.Observation data of indoor physical experiments shown:With wind and DSL,modified Ye Shuiting phreatic water evaporation empirical formula was E=2.9632u×E₀×e^?-5.0017×d×H?,modified Shen Lichang phreaticwaterevaporationempiricalformulawasE=5.161u×E₀^0.7797×?1+d×H?^?-8.1369?,and it was better than Ye Shuiting empirical formula.Secondly,The influence depth of wind on the phreatic water evaporation.When the water depth was 0,50,70,and 100cm,the maximum influence depth of the wind on the state variables of vadose zone?relative humidity,temperature,vapor pressure,water content,and matric potential?were 5,5,10,and 12.5cm below the surface,respectively.The maximum groundwater table was 70¹00cm by the influence of wind on the phreatic water evaporation.Thirdly,model construction.A model coupled water,vapor and thermal was estab-lished,which based on indoor experimental data and considered effect of wind.The model was calibrated and validated by the experimental data,then the hydraulic and thermodynamic parameters were acquired with DSL and without DSL.Fourthly,predicting the influence of meteorological factors on phreatic water evaporation.The results of calibrated model predicted shown that the degree of influence of various factors on phreatic water evaporation were temperature>wind>relative humidity>net radiation.All these achievements can provide scientific evidence for groundwater resources and the mechanism of groundwater evaporation in arid and semi-arid regions.