A study employed magnetic resonance imaging (MRI) to characterize fluid distribution and diffusion in a polypropylene nonwoven fabric based geotextile. Image analysis of three dimensional MRI data determined pore structure. Pore size distribution determined by MRI were smaller on average than those determined by capillary flow smaller on average than those determined by capillary flow porosimetry. Direct imaging of three dimensional pore structure also provided information on preferred fiber orientation in the substrate. Fluid specific imaging of a multicomponent fluid (mineral oil and water) described fluid distribution according to the distribution of total fluid and the distribution of individual components. 9 refs.