Motivated by a versatile three-parameter water retention curve (WRC) formula of Fredlund and Xing, we proposed an alternative expression to describe the relative hydraulic conductivity (RHC) for soils that can capture oven-dry to water-saturated conditions (full moisture range) with a single, closed-form equation (without having to explicitly partitioning the capillary and film flow components). This RHC expression was tested using an existing data set that includes a wide range of soil textures, and shown to be more accurate than the other two RHC expressions. Subsequently, the new RHC expression was combined with the WRC formula of Fredlund and Xing, generating an alternative model (hereafter called the FL model) applicable to describe soil hydraulic properties over the full moisture range. The FL model requires both the known WRC and RHC data since three additional fitting parameters are involved in the present RHC expression. Furthermore, the FL model was employed in a HYDRUS-1D numerical model for simulating the soil moisture redistribution within a lysimeter. The numerical simulation with using the FL model can accurately predict the moisture redistribution, in turn confirming the validity of the FL model despite without partitioning the capillary and film flow components.

中文翻译：

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评估和应用替代公式来描述整个湿度范围内的水力传导率

受 Fredlund 和 Xing 的多功能三参数保水曲线 (WRC) 公式的启发，我们提出了一个替代表达式来描述土壤的相对水力传导率 (RHC)，这些土壤可以捕捉干燥至水饱和条件（全水分范围) 具有单一的封闭式方程（无需明确划分毛细管和薄膜流动分量）。此 RHC 表达式使用包含各种土壤质地的现有数据集进行测试，并显示比其他两个 RHC 表达式更准确。随后，新的 RHC 表达式与 Fredlund 和 Xing 的 WRC 公式相结合，生成了一个替代模型（以下称为 FL 模型），适用于描述整个水分范围内的土壤水力特性。FL 模型需要已知的 WRC 和 RHC 数据，因为当前 RHC 表达式中涉及三个额外的拟合参数。此外，FL 模型用于 HYDRUS-1D 数值模型，用于模拟蒸渗仪内的土壤水分再分配。使用 FL 模型的数值模拟可以准确地预测水分再分布，从而证实了 FL 模型的有效性，尽管没有划分毛细管和薄膜流动分量。