The mathematical representation of the soil hydraulic properties is of central importance for modeling water, solute and energy transport in soils. The established models of the water retention and hydraulic conductivity curves account for capillary water retention and conductivity, but neglect water adsorption and water flow in films and pore corners. They are therefore suited for modeling flow and transport processes in the medium to wet moisture range, but are susceptible to failure in dry soil. The model system developed by Peters (2013, https://doi.org/10.1002/wrcr.20548; 2014, https://doi.org/10.1002/2014wr016107) and Iden and Durner (2014, https://doi.org/10.1002/2014wr015937) (PDI in the following) is a simple parametric framework that overcomes these structural shortcomings. However, it requires one additional parameter to scale the hydraulic conductivity curve in the moisture range where non-capillary flow dominates. Measured conductivity data are required to determine this scaling parameter and to compute the hydraulic conductivity over the complete moisture range. In this contribution, we first show that the original PDI model is in close agreement with a comprehensive model for film conductivity in porous media. We then derive a physically-based approach to predict the film conductivity from the water retention curve. This improved PDI model has the same number of parameters as established models and provides a complete prediction of the hydraulic conductivity curve including non-capillary flow if water retention data and the saturated conductivity are known. Application to literature data covering a broad range of textures shows an improvement of the conductivity prediction by the factor five if compared to the van Genuchten/Mualem model.

中文翻译：

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从保水曲线预测中等至干土中水力传导率的简单模型

土壤水力特性的数学表示对于模拟土壤中的水，溶质和能量传输至关重要。建立的保水率和水力传导率曲线模型考虑了毛细管的保水率和电导率，但忽略了膜和孔角处的水吸附和水流。因此，它们适合于模拟中湿湿度范围内的流动和运输过程，但容易在干燥土壤中破坏。模型系统由Peters（2013，https://doi.org/10.1002/wrcr.20548; 2014，https://doi.org/10.1002/2014wr016107）和Iden and Durner（2014，https：// doi。 org / 10.1002 / 2014wr015937）（以下是PDI）是一个简单的参数化框架，它克服了这些结构性缺陷。然而，它需要一个附加参数来在非毛细流占主导的湿度范围内标定水力传导率曲线。需要测量的电导率数据以确定该比例参数并计算整个湿度范围内的水力导流率。在这一贡献中，我们首先表明原始的PDI模型与多孔介质中膜电导率的综合模型非常吻合。然后，我们得出一种基于物理的方法，从保水曲线预测薄膜的电导率。如果已知保水数据和饱和电导率，则此改进的PDI模型具有与已建立模型相同的参数数量，并提供了包括非毛细管流动在内的水力导流曲线的完整预测。