THE HYDROLOGICAL EFFECTS OF FRACTIONAL WETTABILITY AND CONTACT ANGLE DYNAMICS IN WATER REPELLENT POROUS MEDIA

Abstract

<p>Soil water repellency is a spatially and temporally variable near surface phenomenon most often associated with reduced or impeded infiltration into porous media. In recent years, soil water repellency (hydrophobicity) has garnered much attention in the literature due to its detrimental effects on soil water processes and its widespread observance allover the world in both rural and urban settings. While previous work has developed our understanding of these inherently complex systems, insight into their dynamic and variable nature is still lacking. Having utilized existing technologies in a new way, in this study we present a series of systematic field and laboratory based investigations that clarify the roles of fractional wetting and contact angle dynamics on soil water processes using hydrophobic materials found at a wildfire site approximately 1.5 years post-fire. The robust and fundamental approach taken in investigating<br />water repellency in these materials provided the foundation to develop two conceptual models based on our observations and with respect to existing and emerging theory. These models better explain soil water behaviour in hydrophobic systems than is currently afforded by the literature. We found that wetting and infiltration processes are contingent upon the functional relationship between wettable fractions of materials and the rate of contact angle change in non-wettable fractions.</p>