Jean-Yves Parlange

Water movement in soils

The physical phenomena associated with water movements in soils are examined through a series of simple and concrete examples. Two general analytical tools are used systematically to obtain quantitative results. The first is appropriate for transient effects and the second for gravity effects with finite size cavities. A theoretical description of this kind helps understand the nature of the phenomena, but the solutions are not always adequate for outdoor conditions. The neat description of a soil in terms of well defined properties may be appropriate for laboratory experiments under controlled conditions, but does not take into account the large fluctuations, both with time and position, in properties observed in the field. Often it is not possible to describe a soil in the field by more than a few average features, e.g., moisture content under typical conditions, average diffusivity, and conductivityat saturation. With this in mind, drastic simplifications have been made whenever possible to simplify more ‘rigorous’ solutions. The simpler results become more practical since they are expressed in terms of properties that can be measured in the field.