Prediction of flow and transport through unsaturated porous media requires knowledge of the water retention and unsaturated hydraulic conductivity functions. In the past few decades many different laboratory procedures have been developed to estimate these hydraulic properties. Most of these procedures are time consuming and require significant human commitment. Furthermore, multiple measurement techniques are typically required to yield an accurate characterization of the retention and hydraulic conductivity function between full and residual saturation. We present a more efficient and robust approach to estimating the hydraulic properties of porous media. Our method derives an optimized pore-size distribution from measurements of air permeability and using recent advances in capillary modeling and high-dimensional parameter estimation. The section diameters of different parallel capillaries representing the pore structure of a porous medium are optimized with a multi-algorithm optimization method by comparing measured and modeled air permeability values. The optimized pore model is subsequently used to predict the water retention and water permeability functions. The predicted soil hydraulic properties are shown to be in excellent agreement with experimentally determined data from an unconsolidated porous medium column. Our approach does not impose any functional form of the hydraulic properties and requires only measurements of air permeability.

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