The development of a theoretical method for estimating the wetting branch of the soil water retention curve (SWRC) is required for knowledge of the soil infiltration process. The aim of this study was to derive the theoretical functions to represent the wetting branch of the SWRC based on the Jensen method, and then compare the Jensen method and Kool & Parker (KP87) model for estimating the wetting branch of the SWRC. Fifteen soil samples with varying basic properties (e.g., grain‐size distribution and bulk density (BD)) were selected from the Unsaturated Soil Hydraulic Database (UNSODA) to test these two methods. Results showed that the Jensen method (root mean squared error (RMSE) = 0.057 cm³ cm⁻³) produced a substantially better performance in predicting the wetting branch of the SWRC than the KP87 (RMSE = 0.089 cm³ cm⁻³) for the 15 samples. The range of the scaled mean bias error (SMBE) between the Jensen method‐predicted and measured soil water contents at all pressure heads was −0.529 to 0.402. A positive linear relationship between the SMBE and silt content was observed for the Jensen method. The findings of this study have practical significance for simulating the soil infiltration in the unsaturated zone.

中文翻译：

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根据粒度分数估算土壤保水曲线的润湿分支

需要了解土壤入渗过程的理论方法来估算土壤保水曲线的润湿分支（SWRC）。这项研究的目的是基于Jensen方法得出代表SWRC润湿分支的理论函数，然后比较Jensen方法和Kool＆Parker（KP87）模型来估算SWRC的润湿分支。从非饱和土壤水力数据库（UNSODA）中选择了15种具有不同基本特性（例如，粒度分布和堆积密度（BD））的土壤样品来测试这两种方法。结果显示Jensen方法（均方根误差（RMSE）= 0.057 cm ³ cm ^-3）在15个样品上，在预测SWRC的润湿支路方面比KP87（RMSE = 0.089 cm ³ cm ^-3）产生了更好的性能。Jensen方法预测和测得的所有压头土壤含水量之间的比例平均偏差误差（SMBE）的范围为-0.529至0.402。对于詹森方法，观察到SMBE和淤泥含量之间呈正线性关系。这项研究的结果对于模拟非饱和区的土壤入渗具有实际意义。