Thermography for characterization of soil water repellency at larger spatial scales

Abstract

Soil water repellency (SWR) is natural phenomenon occurring in soils throughout the world. It is a surface property that reduces the attraction of soil for water. Measurement of soil water repellency is done at the point scale; however its role in the environment often evaluated at the landscape scale. This disparity is due to limitation in the scale of measurements. The objective of this study is improving characterization of soil water repellency at larger spatial scales through thermography. Thermography shows promise to track the temporal and spatial dynamics of soil water repellency. In a lab experiments, it has been demonstrated that there was a huge potential for thermal imaging in SWR mapping to distinguish between highly repellent areas and wettable ones. However, the proposed technique had a number of limitations. One major drawback was its poor performance to detect low SWR areas which is often present in the environment. Another issue is the induction of a temperature gradient to reveal SWR, while also changing the surface properties of SWR. A strategy to help in distinguishing the differences in SWR is to assess the energy balance and evaporative fluxes of the soil surface. A lab calibration experiment will be presented to distinguish the link between thermal regime, evaporative flux, soil water content and soil water repellency. A field survey using thermography to map soil water repellency at larger spatial scales will improve understanding of how SWR can affect hydrologic processes at larger scales. Through this innovative technique, we will be able to predict and model the behaviour of water dynamics in water repellent soil and therefore improve management of water and soil resources. We will further understand the role soil water repellency plays for ecosystem services.