The different forms of moisture profile development during the redistribution of soil water after infiltration

Abstract

Two different forms of moisture profile development may occur during the redistribution of soil water after infiltration. In one the profile shape continues to be similar to that during the infiltration process, with a fairly uniform water content region near the soil surface above a steep wetting front, and the rate of redistribution is inversely related to the infiltration depth. In the other, water drains from near the surface to appear as a step in the moisture profile below the wetting front at the cessation of infiltration, and the rate of redistribution is directly related to infiltration depth. Classical theory of soil water movement is shown to account for both forms of moisture profile development, which depend on the moisture profile shape at the cessation of infiltration and on the soil water properties of the porous material. Experimental results of moisture profile development in a sand column illustrate how different profile forms develop as the depth of infiltration is increased and, by inclining the experimental column, how they depend on the relative importance of the soil water pressure head gradients compared with that of gravity.