Non Monotonic Imbibition Profiles and Transition to a Perched Water Table in a Gradually Layered Soil

Abstract

An imbibition process at low infiltration rate into a soil, whose hydraulic conductivity at saturation K _s decreaseswith depth, can lead to non monotonic water– content profiles and to the onset of a perched water table. By means of a numerical simulation of an infiltration process into a 1D, exponentially K _s –decreasing soil, four different behaviors of the tensiometer–pressure profiles were observed at increasing the infiltration rate: either the solution remains monotonic, or a peak of water content onsets and vanishes and the solution recovers its monotonicity, or the peak vanishes but a perched water table onsets at the bottom and rises, or the peak itself reaches the water content at soil saturation at one point and there a perched water table onsets. This latter pattern was found in qualitative agreement with previously performed experimental results.