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Xi’an University of Science and Technology (2019)

Analysis on the Evaporation of Soil and Groundwater in the Mu Us Desert

李吉祥;

Titre : Analysis on the Evaporation of Soil and Groundwater in the Mu Us Desert

Auteur : 李吉祥;

Grade : Master’s Theses 2019

Université : Xi’an University of Science and Technology

Résumé
Bare soil evaporation is an important compont of energy balance and hydrological cycle in arid and semi-arid regions.Soil evaporation is closely related to net radiation,air temperature,relative humidity,wind speed,soil texture and the lithology of aeration zone,so the calculation of soil evaporation is very complicated.Studies have shown that groundwater evaporation is an impor,tant discharge in arid areas,and the accuracy of soil-groundwater evaporation calculation directly affects the evaluation accuracy of the quantity of groundwater.Therefore,it is of great theoretical significance and practical value to carry out the analysis of soil-groundwater evaporation for the evaluation of water resources.In this paper,the aeolian sand in Mu Us Desert is taken as the research object,and soil hydrodynamics,soil thermodynamics,soil physics,hydrogeology and other theories are taken as the guidance.A study on water transport in vadose zone under evaporation conditions was carried out by means of laboratory test,in-situ test and numerical simulation.Firstly,indoor evaporation tests were carried out and the evaporation formula considering the soil texture is proposed,and compared with the commonly used empirical formula,and the applicability of the formula in Mu Us Desert is discussed.Secondly,the in-situ test of soil-groundwater evaporation is carried out,and the correlation between evaporation rate and net radiation,air temperature,relative humidity and wind speed is analyzed.Finally,a numerical model of soil-groundwater migration was established based on in-situ test,and the phreatic evaporation ratio and contribution rate of soil water under the condition of the different phreatic water depth were predicted.In conclusion,the following works have been done in the study.The laboratory test shows that the evaporation intensity gradually decreases with the increase of the buried depth of diving.When the buried depth is 71cm,the evaporation intensity of diving is close to 0,so the maximum evaporation depth of diving in Mu Us Desert is 71cm.The formula of phreatic steady evaporation based on soil texture is proposed E = 0.002E0d-4Ks,which has better fitting effect than the empirical formula in calculating steady phreatic evaporation in Mu Us DesertThe in-situ test shows that the shallow water evaporation intensity of bare soil is positively correlated with net radiation,relative humidity and air temperature,but negatively correlated with relative humidityThe numerical simulation results show that :①When the depth of phreatic water is less than or equal to 30 cm,the contribution rate of soil water is exponential function with the depth of phreatic water and follows the distribution law of C = 0.043×e(H/10.3)-0.05.When the depth of phreatic water is greater than 30 cm,the contribution rate of soil water is power function with the depth of phreatic water and follows the distribution law of C = 0.765 +0.185/(1+(H/81.1)3.716).②The diving depth and the potential evaporation ratio are exponentially functional,obeying the distribution law of E/Eo0= e-(H/4.48)+1.85E-4.The above results show that the contribution rate of soil water and groundwater to evaporation varies nonlinearly with the increase of phreatic depth,which has a certain guiding significance for improving the evaluation accuracy of water resources in arid areas

Mots clés : evaporation; water transport in vadose zone; analysis; depth of phreatic water; Mu Us sandland

Présentation (CNKI)

Page publiée le 15 novembre 2019