非饱和土壤Richards方程入渗求解探讨

Discussion on unsaturated soil of Richards infiltration equation

根据理查兹 (Richards)方程求解非饱和土壤垂直一维入渗率历时规律 ,因缺乏土壤水分特性函数K(θ)、D(θ)的一般有效公式 ,而采用与实际相差甚远的定值或线性函数假设 ,使成果隐含过多经验成分或需要反复迭代计算。笔者在文献 [1]中提出的非饱和土壤水分特性函数的一般有效基础公式 ,用分离变量法直接求解Richards方程 ,用土壤水动力学方法分别导出了含有渗前土湿因子的新入渗公式。它摆脱了同类入渗公式对水分函数过于简单的概化假设和经验成分。为放弃迄今水文学产流计算中惯用的下渗容量曲线“截首留尾”的经验做法 ,以直接使用含有渗前土湿因子的下渗公式提供了理论依据 ,从而将有利于产流计算方法的改进和计算精度的提高。

According to Richards Equation, 1-D vertical infiltration rate by real time for unsaturated soil could be found. Because of lacking for formula on unsaturated soil moisture function K(B)、D(B), suppose of fixed value or linear function, which were not fit reality, had to be adopted. Thus, those results of research has to imply some experiential elements or some iterative calculation. With generic effective base formula on unsaturated soil moisture function K(B)、D(B) list in reference 1, new infiltration formula, which contains soil moisture factor before infiltration、more solid theoretical basis, can be exported by using the method of separation of variables to answering Richards Equation directly and soil water dynamic method. New formula avoided experiential elements and general supposed on moisture function and reflecting effect of decrease infiltration indirectly on soil moisture before infiltration in congeneric infiltration formula. It provide theoretical basis for using infiltration formula which contains soil moisture factor before infiltration instead of giving up existing empirical way of “rounding off” in infiltration capacity curve at rainfall excess calculation in hydrology so far. It will help improve the method of rainfall excess calculation and calculating precision.