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Three‐parameter lognormal distribution model for soil water retention
Author(s) -
Kosugi Ken'ichirou
Publication year - 1994
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/93wr02931
Subject(s) - log normal distribution , mathematics , standard deviation , function (biology) , water retention curve , distribution (mathematics) , distribution function , water retention , soil water , statistics , soil science , thermodynamics , environmental science , mathematical analysis , physics , evolutionary biology , biology
Many models for soil water retention have been proposed. However, most of these models are curve‐fitting equations and do not emphasize the physical significance of their empirical parameters. A new retention model that exhibits increased flexibility was developed by applying three‐parameter lognormal distribution laws to the pore radius distribution function ƒ( r ) and to the water capacity function, which was taken to be the pore capillary pressure distribution function ƒ(ψ). This model contains three parameters that are closely related to the statistics of ƒ(ψ): the bubbling pressure ψ c , the mode ψ 0 of ƒ(ψ) and the standard deviation σ of transformed ƒ(ψ). By comparison of this model with three existing models (the van Genuchten model, the Brooks‐Corey model, and the modified Tani model), it was shown that ψ c , ψ 0 , and σ are all essential for a general retention model.