Infiltration into layered soil covered with a depositional seal: a green-ampt approach
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Systems Research Lab, USDA-ARS, Bldg 007, Rm 008,10300 Baltimore Ave., Beltsville, MD 20705, U.S.A.
Int. Agrophys. 1996, 10(1): 21-30
Our objective was to develop a method of infiltration simulation that could be applied in crop models which use simplified soil water transport models. Infiltration into layered soil profiles topped with a deposi-tional crust is considered in this paper. The proposed method, based on the Green-Ampt equation, uses harmonic mean hydraulic conductivity in the wetting zone, assumes the pressure head in the wetting zone to be close to pressure head under the seal, and treats the wetting front pressure head as a value which provides for conservation of the integral mean hydraulic conductivity of the wetting front. The method was validated against results of numerical solution of Richards' equation for infiltration into a three layered soil profile and two homogeneous soil profiles with constant and transient seal conductance. Differences of 2-5 % were found between cumulative infiltration and infiltration rate values calculated by the proposed method and by the finite difference solution of the Richards' equation. Largest differences arose during the period when the wetting front passed the interface between layers. When the conductivity of the lower layer was greater than the conductivity of the upper layer the differences between the finite difference solution and the proposed method was 10 to 15 % after 360 min.
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