SCALING OF SOIL WATER RETENTION USING A FRACTAL MODEL

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Abstract

A quantitative description of the spatial variability of soil hydraulic properties is increasingly important, especially in simulations of soil water regimes. The objective of this study was to use a fractal concept to quantify and simulate the spatial variability of water retention of fine textured soils over a wide range of soil matric potentials. To scale water retention data, we assumed fractal self-similarity of pore volume and derived an equation of the water retention curve in the form of the probability integral. Experimental data on water retention were obtained on sand-kaoline plates and above saturated salt solutions in the ranges of the soil matric potential from −50 to −1 kJ m-3 and from −140 to −20 MJ m-3, respectively, for chernozem soil (Typic Haploboroll, clay loam) sampled over a 12,000 m2 area and for dark chestnut soil (Ustolic Orthid, loam) sampled over a 1500 m2 area. The resulting formulae gave a good fit of water retention data. The spatial variability of water retention could be described by the spatial variability of the single dimension-less parameter. Pore fractal dimension could be considered constant over the areas of sampling for both soils.

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