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Soil Water Relations During Rain Infiltration: I. Theory
Author(s) -
Rubin J.,
Steinhardt R.
Publication year - 1963
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1963.03615995002700030011x
Subject(s) - ponding , infiltration (hvac) , hydraulic conductivity , water content , soil science , thermal diffusivity , soil water , hydrology (agriculture) , environmental science , pedotransfer function , richards equation , geotechnical engineering , geology , thermodynamics , physics , drainage , ecology , biology
Soil moisture content changes and rates of water entry during rain infiltration into a semi‐infinite soil column are analyzed mathematically. The model considered involves, principally, the following assumptions: Darcy's and continuity equations are applicable; the soil's hydraulic conductivity and diffusivity are unique, positive, and monotonically increasing functions of soil moisture contents; rainfall entering the soil can be considered as a continuous body of water. It is shown analytically that an incessant rain eventually results in ponding if and only if rain intensity, R, exceeds the saturated soil's hydraulic conductivity, K(w sat ). For R ⩽ K(w sat ) it is proven that as infiltration proceeds soil moisture contents at increasing depths tend to approach a constant level. At this level the soil's hydraulic conductivity equals the rain intensity. For R > K(w sat ) it is indicated how to estimate the water uptake at incipient ponding. A difference method for solving approximately the differential equation of the model in question is described. An illustrative numerical example of this method's results is presented.