Porosity reviewed : quantitative multi-disciplinary understanding, recent advances and applications in vadose zone hydrology

Abstract

Porosity—one of the most basic mechanical properties of a medium—has implications in a vast range of disciplines and used for a similar vast range of applications. These include, for instance, the storage and flow of water; the compressible component of earth materials, which can be subjected to consolidation under loading; the variable parameter in the swelling and shrinkage of clays; and possibly a governing parameter in the formation of wetlands and perched water tables. This review notes the relevance of a fourfold quantification of porosity for vadose zone studies, viz. (1) type (matrix or structure), (2) scale (submicro to macro scale), (3) connectivity, and (4) water saturation. This is followed by a review of recent advances in the quantification and description of porosity in porous media (visual and remote sensing methods, porosimetry, geometrical approaches, empirical estimations, densest packing simulations, etc.), the applications to quantification of hydrological parameters, and a brief glimpse into the significance of porosity in a temporary hillslope wetland underlain by Archaean Lanseria gneiss in South Africa. Final comments are made regarding areas where quantification of porosity is problematic.