Simulation Of Unsaturated Soil Infiltration And Water Salt Transport In Arid Area Based On HYDRUS

Soil salinization has become an important factor hindering agricultural economic development in oasis in arid areas.The study of soil water and salt transportation in arid areas is very important to the ecological and agricultural economic development in arid areas.This paper takes unsaturated soil of Xinjiang Akesu Wei-Ku Oasis as the research object,according to the soil structure of study area setting indoor experiments,to study the influence of soil texture,soil structure,TDS of irrigation water in water and salt movement on unsaturated soil of Wei-Ku Oasis.The HYDRUS model is used to simulate the process of water and salt transportation in unsaturated soil in study area,so as to provide theoretical basis for solving the problem of soil salinization and establishing reasonable irrigation plan in Wei-Ku Oasis.The results show that:1)The cumulative infiltration capacity and wetting front change trend of unsaturated soil are similar in the study area.At the initial stage of infiltration,the cumulative infiltration capacity and wetting front of four unsaturated soils increase rapidly and change nonlinearly with time;with the increase of infiltration time,the cumulative infiltration and wetting front of the four soils showed continuous linear growth with time2)In the four structure,when the soil salinity is the same,the cumulated infiltration amount of interlayer soil is larger than that without interlayer soil;in the soil with interlayer structure,the lower structure of coarse soil is beneficial to the infiltration of soil water,and the infiltration time is short.3)By using different salinity water infiltration,when the TDS of 3.5g/l water infiltration,all soil infiltration increased,soil water infiltration time is greatly reduced.Among them,soil infiltration time of the sand layer structure is the shortest,the water conductivity of sand layer increases obviously under this condition.4)Using exponential model to fit the hydrodynamic dispersion coefficient of unsaturated soil in study area,the overall fitting accuracy is higher.The highest of fitting degree was 0.97,and the lowest was 0.64.5)By measuring the change of soil moisture in unsaturated soil,it is found that the variation of moisture in the soil with interlayer is discontinuous.Among them,the soil structure with less salt content has the fastest change of soil moisture.In all unsaturated soil,the soil with large proportion of silt and clay has great soil moisture content and good soil water holding property.6)HYDRUS model is used to simulate the process of water and salt transport in unsaturated soil of Wei-Ku oasis,and the overall simulation accuracy is high.The simulation result shows that the minimum of coefficient of determination R2 is 0.65,the highest is 0.92;and the minimum of the root mean square error RMSE is 0.11,and the highest is 0.39.It shows that HYDRUS model is applicable to the study area,and can provide the basis for water and salt management for unsaturated soil of study area.