STEADY INFILTRATION INTO A 2-LAYERED SOIL FROM A CIRCULAR SOURCE

Infiltration of water from a surface source is highly relevant to a wide range of problems in soil science, hydrology, and engineering. This article presents analytical solutions to steady infiltration in layered soils caused by a constant influent through a circular area (such as a pond or a ring infiltrometer) at the land surface. An exponential relationship between the unsaturated hydraulic conductivity and the pressure head, K = K-0 exp (alpha psi), is assumed for both layers, and alpha is assumed to be the same for both layers. The solutions for two kinds of lower boundary conditions are discussed. The first condition assumes a semiinfinite system with very dry soil at an infinite depth; the second condition considers an impermeable boundary. Solutions are given for single layer and two-layer systems. As a special case of the two-layer solution, the single layer solution agrees very well with previous solutions when the boundary conditions are approximately the same. The effects of soil properties and layer thickness are also discussed.