Electrical capacitance volume tomography of soil water infiltration in a vessel experiments

Abstract. Electrical capacitance volume tomography (ECVT) is a recently-developed technique for real-time, non-invasive 3-D monitoring of processes involving materials with strong contrasts in dielectric permittivity. This paper is the first application of the method to visualization of water flow in soil. We describe the principles behind the method, and then demonstrate its use with a simple laboratory infiltration experiment. 32 ECVT sensors were installed on the sides of an empty PVC column. Water was poured into the column at a constant rate, and ECVT data were collected every second. The column was then packed with dry sand and again supplied with water at a constant rate with data collected every second. Data were analyzed to give bulk average water contents, which proved consistent with the water supply rates. Data were also analyzed to give 3-D images (216 voxels) allowing visualization of the water distribution during the experiments. For infiltration into the soil, wall flow, progress of the unstable wetting front, and the final water distribution showing air pockets are clearly visible. Result of this study showed that the normalized dielectric permittivity distribution of the water and the saturated soil is 1.0 and around 0.9, respectively.