基于群智能优化算法的土壤水动力参数反演

Inversion of Soil Hydrodynamic Parameters with Richards Equation Based on Intelligent Optimization Algorithm

土壤水动力参数是模拟田间土壤物质传输过程的基本参数,准确确定土壤水动力参数对实现农田生境精准调控具有重要意义。基于一维垂直入渗试验数据,采用代数方法和数值方法,构造3个不同的目标函数,并分析鲸鱼优化算法和灰狼优化算法反演Brooks-Corey-Mualem模型参数的适用性。结果表明:通过选择合适的目标函数,两种群智能优化算法均可用于反演土壤水动力参数。在代数方法中,鲸鱼优化算法在目标函数2下(由累积入渗量、入渗时间、含水率构成的相对误差)固定参数θr、θs优化得到的土壤水动力参数误差最小,反演参数得到的累积入渗量、入渗率、含水率的相对误差都在9.74%以下,决定系数都在0.9040以上,反演时间为70 s;在数值方法中,灰狼优化算法在目标函数3下(由累积入渗量、湿润锋深度、含水率构成的相对误差)固定参数θr、θs优化得到的参数误差最小,反演参数得到的累积入渗量、入渗率、含水率的相对误差都在2.53%以下,决定系数都在0.9917以上,反演时间为115 s。因此,代数方法所用时间短、精度相对较低,数值方法所用时间较长、精度相对较高,在反演土壤水动力参数时,可根据误差精度需求,选择合适的优化方法。

Soil hydrodynamic parameters are the basic parameters for simulating the process of soil material transport in the field.Accurate determination of soil hydrodynamic parameters is of great significance to achieve precise regulation of farmland habitat.For one-dimensional vertical infiltration experimental data,based on algebraic and numerical methods,three different objective functions were constructed,and the applicability of the whale optimization algorithm and grey wolf optimizer was analyzed to invert the parameters of the Brooks-Corey-Mualem model.The result showed that by choosing an appropriate objective function,both swarm intelligence optimization algorithms can be used to invert soil hydrodynamic parameters.In the algebraic method,the whale optimization algorithm optimized the soil hydrodynamic parameters with the fixed parametersθr andθs under the objective function two(relative error composed of cumulative infiltration,time,and soil water content profiles)with the smallest error.The relative errors of the cumulative infiltration volume,infiltration rate,and soil water content profiles obtained from the inversion parameters were all below 9.74%,the determination coefficients were all above 0.9040,and the inversion time was 70 s.In the numerical method,the parameter error derived from the fixed parametersθr andθs under the objective function three(relative error composed of cumulative infiltration,depth of wetting front,and soil water content profile)of the grey wolf optimizer was the smallest.The relative errors of the cumulative infiltration volume,infiltration rate,and soil water content profiles obtained from the inversion parameters were all below 2.53%,the determination coefficients were all above 0.9917,and the inversion time was 115 s.Therefore,the algebraic method took a short time and has relatively low accuracy,while the numerical method took a long time and has a relatively high accuracy.When inverting soil hydrodynamic parameters,an appropriate optimization method can be selected according to the error accuracy requirements.