A Modular Framework for Modeling Unsaturated Soil Hydraulic Properties Over the Full Moisture Range

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A generalised modular framework for partitioning soil hydraulic properties functions (SHP) into a capillary and a non-capillary part is developed. The full water retention curve (WRC) is modelled as a weighted sum of parametric capillary saturation function and a new general model for the non-capillary saturation function. This model is directly computed from any selected capillary saturation function. With it, a physically complete, continuous and flexible representation of the WRC is achieved, ensuring zero water content at oven dryness. In a modular and hierarchical framework, the expressions for the capillary and non-capillary saturation function are used to calculate the respective hydraulic conductivity curves (HCC). This is achieved by adopting Mualem’s integral for the capillary part of the HCC only and calculating the non-capillary HCC directly from the new non-capillary saturation function. This leads to consistent descriptions of measured HCC data, including the often observed change in slope beyond –100 cm pressure head. Compared to the classical van Genuchten- Mualem approach, it requires only one additional model parameter. The SHP framework model describes both WRC and HCC adequately and coherently. We demonstrate the suitability of the SHP Framework and versatility by describing measured WRC and HCC data across the full moisture range using soil samples from a wide range of textures and origins. The modular framework was implemented in the soil physics and soil hydrology (spsh) R-package, available from the SI. It contains several SHP models, model parameter estimation, and features options for goodness of fit statistics, and model selection. Plain
Original languageEnglish
JournalWater Resources Research
Volume55
Issue number6
Pages (from-to)4994-5011
ISSN0043-1397
DOIs
Publication statusPublished - Jun 2019

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