Moisture Movement Law And Groundwater Recharge In Aeration Zone Under Irrigation Conditions In Yili River Valley

YiIli river valley of Xinjiang is located in the northwest of China,this area hascharacteristics of strong evaporation and rare precipitation.Vadose zone is an important passage for irrigation water to enter the groundwater and Irrigation water is an important source of groundwater,research on the law of water transport,in the vadose zone and the law of groundwater recharge are very essential to realize the rational development and utilization of groundwater resources.In view of the above problems,this paper combines the field farmland irrigation experiment with numerical simulation,and establishes the water transport numerical model of saturated-unsaturated using Hydrus-2d software.the research simulates the law of moisture movement in the vadose zone and the law of groundwater recharge,and explores the influences of various vadose zone lithologic structures on groundwater recharge to use different irrigation conditions.The paper concludes as follows:(1)Based on in-situ testing observations,the research found out that the lithologic structure of the vadose zone controls the law of water transport,Under the same irrigation condition,for water infiltration capacity,the homogeneous structure of fine sand is better than the upper layer coarse and lower layer fine lithology and multi-layer lithology,multi-layer structure is the most unfavorable for water infiltration.(2)Establishesthe water transport numerical model of saturated-unsaturated using Hydrus-2dsoftware.Taking the irrigation recharge coefficient as the researchobject,studying the sensitivity of hydraulic parameters.The homogeneousstructure shows that the factors affecting the irrigation recharge coefficientare?sandn.When the lithology is upperlayercoarseandlowerlayerfine,themaximuminfluencing factor of theirrigation recharge coefficient is?s.(3)Through the two-dimensional model of saturated and unsaturated water,the study shows that under the condition of upper and lower fine lithology,the lateral migration of water is greater than that of homogeneous lithology and multi-layer lithology.Moisture lateral migration distance.The lateral migration distance of the upper and lower lithology is 300cm;the lateral migration distance of the multi-layer lithology is 200cm;under the condition of homogeneous lithology,the lateral migration distance is 70cm.(4)Under the same lithological structure,the migration of irrigation water in the vadose zone is mainly controlled by the irrigation quota.When the lithological structure is a homogeneous fine sandstone layer,the irrigation water can not effectively recharge the groundwater when the irrigation quota is less than 0.05m~3/m~2.As irrigation quotas increase,the lag time for irrigation recharge groundwater also decreases.When the irrigation quota increased from 0.1m~3/m~2to 0.2m~3/m~2,the lag time of irrigation water recharge groundwater was also shortened from 300 days to 180 days,and the irrigation recharge coefficient also increased from 0.03 to 0.38.(5)The law of irrigation water in the vadose zone is not only affected by the irrigation recharge,but also by the lithology of the vadose zone.When the irrigation quota increased from 0.05m~3/m~2 to 0.2m~3/m~2,the irrigation could not penetrate the multi-layer lithology structure mainly because the upper silty clay layer was 140cm thick and the lithology particles were relatively thin.Water holding capacity is relatively strong.Therefore,the irrigation water is enriched in a section of 100 cm or more,and it is impossible to form an effective supply to the groundwater.For the upper and lower fine lithology structure,the water conductivity is relatively strong due to the coarse lithology of the upper part.Therefore,as the irrigation quota changes from 0.1 m~3/m~2to 0.15 m~3/m~2and 0.2 m~3/m~2.The lag time of irrigation water recharge groundwater is changed to 75 days,43 days and25 days,and the irrigation recharge factors are 0.07,0.21 and 0.36,respectively.