| Minqin Basin is a typical desert oasis.Groundwater and surface water in the area are frequently converted through aeration zone.The main source of groundwater supply is irrigation water infiltration.The continuous exploitation of groundwater makes the thickness of vadose zone increase,and the law of water infiltration in vadose zone becomes complex.It is urgent to study the law of water migration in vadose zone in this case,so as to provide a basis for groundwater resource evaluation.In this paper,the in-situ aeration zone test station is established,and the matrix potential data from April 2019 to October 2019 are monitored and collected.The physical properties of soil were analyzed.The numerical model of water migration in the vadose zone is established,and the law of water migration in the vadose zone is analyzed.The research results are of great significance to the evaluation of groundwater resources and the improvement of ecological environment.The model method and the zero flux method are used to calculate the equilibrium of the study area,both of which ignore precipitation and soil evaporation.The evapotranspiration calculated by the model method and the zero flux method are 479.82 mm and 512.66 mm respectively,and the storage changes in the vadose zone are 31.08 mm and 17.17 mm respectively,which are in a positive equilibrium.Zero flux method has a large amount of evapotranspiration,because it actually considers the influence of precipitation and soil surface evaporation.In the process of single irrigation,the shallow zero flux surface has obvious displacement,but there is a stable divergent zero flux surface at the depth of 280 cm.After 10 days of irrigation,the soil volume moisture content of 20 cm,40cm,70 cm,100cm and 140 cm increased by 6.0%,2.9%,2.0%,0.4% and 0.3% respectively.It can be concluded that the irrigation water replenished the soil moisture within 140 cm of the buried depth,and the soil moisture content of 180 cm and below did not change significantly.The position of zero flux surface is different after irrigation in different growth period of maize.From seedling stage to jointing stage,the divergent zero flux surface formed by irrigation moved from 100 cm to 40 cm,and the convergent zero flux surface appeared at jointing stage.From jointing stage to grouting stage,the divergent zero flux surface moved from 40 cm to 70 cm,and the convergent zero flux surface moved from 100 cm to 140 cm.The effects of soil texture,crop potential evaporation and crop root depth on water movement in vadose zone were analyzed.Among them,with the increase of sand,the decrease of crop transpiration and the increase of discharge from the lower layer,the single irrigation should be reduced and the number of irrigation should be increased to make better use of irrigation water.With the increase of crop potential transpiration,the transpiration will increase,and the amount of water discharged to the aeration zone in the lower layer will decrease.The soil water potential increases with the increase of root depth in the soil layer whose root depth is within 70 cm,and decreases with the increase of root depth in the soil layer below 70 cm.The deep root system of crops makes the soil water potential content of the surface soil higher.Considering the evaporation of soil surface,the evapotranspiration of the whole aeration zone increases,so it is necessary to increase the irrigation amount properly. |
