Derivation of a two-term infiltration equation from the Green-Ampt model
Swartzendruber, D. (2000). Derivation of a two-term infiltration equation from the Green-Ampt model. J. Hydrol. (Amst.) 236: 247-251
In: Journal of Hydrology. Elsevier: Tokyo; Oxford; New York; Lausanne; Shannon; Amsterdam. ISSN 0022-1694; e-ISSN 1879-2707, more
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| Abstract |
For a uniform and infinitely deep soil at constant initial volumetric soil water content thètan, the soil surface is subjected instantaneously to a ponded-water head that increases with the square root of time t ½ after the initial ponding of water. An integration procedure is used in a rigorous derivation of the one-dimensional Green-Ampt flux equation. The resulting ordinary differential equation is solved exactly to yield the two-term infiltration equation wherein the coefficient of t is the sated hydraulic conductivity, but the ponded-head t ½ function must be the same as the one found earlier by a different but exact mathematical derivation. The present findings reveal and describe this previously unknown kinship between the Green-Ampt infiltration model and the two-term infiltration equation, and underscore in still another way the serious limitations of the two-term equation. |
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