Recurrent ponded infiltration into structured soil: A magnetic resonance imaging study

Abstract

Recurrent ponded infiltration (RPI) was applied to two undisturbed samples (5.4‐cm diameter, 9‐cm height) of coarse sandy loam (Korkusova Hut', CR). The water distribution within the samples during RPI was monitored using magnetic resonance imaging (MRI); the soil internal structure was visualized by X‐ray computed tomography (CT). Preferential flow and a decrease of the steady state infiltration rate between two successive infiltrations of RPI are typical for the soil studied. During the MRI‐monitored experiment these phenomena were pronounced only in one sample, which facilitated their linking to specific features in the MRI results; the flow rate decrease was related to a reduction of the MRI‐detected water content and a change of the spectrum of T 1 (a characteristic related to the water surface‐to‐volume ratio). The MRI methods employed could detect water in low‐density regions and thereby captured potential preferential pathways; however, one‐dimensional (1‐D) MRI demonstrated that some results may be affected by fast flow.