土壤水下渗解析解与数值解的比较研究

Comparison of Analytical and Numerical Solutions for Soil Water Leakage Calculation

针对饱和—非饱和条件下土壤水的垂向下渗,分别用半经验计算公式和全物理基础的HYDRUS模型模拟了不同降雨情景下的土壤水渗漏量,对两种方法的计算结果进行了比较。结果表明,两种方法均能反映出土壤水渗漏率与降雨强度的相关性,降雨强度和降雨总量的增加引起土壤水渗漏总量的增加。在较小雨强条件下,公式计算土壤水渗漏总量稍大于HYDRUS模型计算,雨强较大时则相反。两种方法的计算结果在渗漏率峰值的出现时间和土层底部初始出流时间上存在差异。当土层厚度减小时,半经验解析式的计算精度有所提高,在使用该解析式时,建议对土壤层分层计算,可以提高计算精度。

The vertical percolation of soil water under different rainfall inputs is calculated using a semi-empirical analytical equation and the numerical solution from HYDRUS-1D model.Results from both methods are compared to assess the relative accuracy of the analytical equation.It is found that both methods can capture the response of soil water leakage to the rainfall conditions.The soil water percolation rate is highly correlated to rainfall intensity.The analytical solution of soil water percolation is a little greater than the numerical solution for low rainfall intensity and the result is the opposite for high rainfall intensity.Major differences from the two methods are shown in terms of the time when the peak percolation rate occurs and the time when the water initially starts to occur at the bottom of soil column.It is also found that the accuracy of the analytical solution is improved with the decrease in the thickness of soil column.Therefore,it is suggested that soil column be divided into sub-columns when the analytical solution is used to achieve a better accuracy in the calculation.