RETENTION AND DISTRIBUTION OF MOISTURE IN SOILS AFTER INFILTRATION HAS CEASED

Abstract The description of the downward movement of water during infiltration can be obtained by solving the partial differential equation that governs the unsaturated flow of water through soils. The problem of the redistribution of the water and prediction of moisture profiles after the infiltration has ceased cannot be solved (from a theoretical standpoint) with the present knowledge. This is due to the scanning curves in the relationship of pressure versus water content which, therefore, is not a unique function. Experimentally obtained soil-moisture profiles are presented. A discussion on the "field capacity" concept is also presented which is shown not to have any physical or mathematical justification. It is proposed that the "field capacity" concept should be replaced with the water content corresponding to the point of inflection (of the drying phase) of the pressure-water content curve. This value is a physical characteristic constant value for a given soil and is different for different soils ...