变水头入渗条件下VG模型参数变化对土壤入渗的影响

Effect of VG Model Parameter Changes on Soil Infiltration Under Varying-head Infiltration

为了探究变水头入渗条件下van Genuchten模型各参数对不同质地土壤入渗特性的影响,基于HYDRUS-1D模型,采用局部分析法对不同土壤质地不同输出变量下VG模型各参数的敏感性进行分析。结果表明:各参数对压力水头的影响均随土壤质地变细而减小,且同质地土壤各参数敏感性在降雨结束时达到最大,之后随时间增加而减小;同一参数的正负扰动对累积入渗量的影响程度基本相同;n、Ks、θs对压力水头和累积入渗量的影响较大;VG模型各参数对不同质地土壤湿润锋运移距离的影响差异较大,各参数敏感性大小排序为:θs>Ks>α>n>θr(砂壤土)、α>θs>Ks>θr>n(壤土)、n>α>θr>θs>Ks(黏壤土)。边界条件是VG模型参数敏感性的重要影响因素之一。因此在模型应用时,应注意边界条件的选择以及参数θs、α、n、Ks的准确性。

In order to explore the influence of various parameters of Van Genuchten model on infiltration characteristics of soils of different textures in the condition of varying-head infiltration,based on the HYDRUS-1D model,this paper analyzes the sensitivity of VG model parameters under different soil texture and output variables by the partial analysis method.The results show that:The influence of each parameter on the pressure head decreases as the soil texture becomes finer,and the parameter sensitivity of soils with same texture reaches the maximum at the end of the rainfall,and then decreases with the increase of time;The effects of positive and negative perturbation of the same parameter on cumulative infiltration are basically the same;n、Ks、θs have greater influence on pressure head and cumulative infiltration;The influence of VG model parameters on the wetting front transport distance for soil of different textures varies greatly,and the sensitivity of each parameter is ranked as follows:θs>Ks>α>n>θr(sandy loam),α>θs>Ks>θr>n(loam),n>α>θr>θs>Ks(clay loam).Boundary conditions are one of the important factors affecting parameter sensitivity of VG model.Therefore,when applying the model,more attention should be paid to the choice of boundary conditions and the accuracy of the parametersθs、α、n、Ks.