Visualisation of Static and Dynamic Water Phenomena in Soil Using Magnetic Resonance Imaging

Abstract

This paper reports the use of Nuclear Magnetic Resonance Imaging (MRI) to study static and dynamic soil water phenomena. Two-dimensional and three-dimensional images were obtained to visualise water content, void geometry, and water wetting, drainage and redistribution in three soil materials: packed crumbs of Hanslope clay soil, medium quartz sand and coarse quartz sand. The observed wetting and drying phenomena differed among these soil materials. The wetting front in a column of the medium sand was the typical piston type, but not in the packed clay soil column. Wetting front instability was observed in the coarse sand column. Images of water draining vertically through the medium sand column showed a uniform drainage profile. Drainage from the coarse sand column initially showed a drying front, and approached a uniform profile after free drainage. In contrast, drainage from the clay soil column showed a drying front and a non-uniform drainage profile. The preliminary results from this study show that MRI appears to be a useful tool for visible, nondestructive investigations of soil structure and transport processes, with potential attendant benefits for quantification and modelling of preferential flow in such soils.