Three-dimensional visualization of preferential flow patterns in two soils

Visualization techniques are helpful in finding spatial relationships of parameters which are otherwise difficult to detect. In this study, visualization techniques were used to examine the basis of moisture distribution patterns in a clay soil and a water repellent sandy soil. In the clay soil, spatial distributions of moisture contents and macropore networks were investigated with computed tomography (CT) images. The macropore networks were determined from CT images from a dry soil core, and the moisture content patterns from CT images after which KI enriched water was applied. Soil moisture and bulk density were investigated and measured in a water repellent sandy soil by intensive sampling of an area 1.2 m long and 0.6 m wide. The measured parameters were visualized in three dimensions using IRIS Explorer on a SGI-Indigo and a SGI-Onyx computer. The 3D computer representations showed that there exists a strong correlation between the moisture content distribution and the geometrical structure of the macropore network for a clay soil. Moisture contents higher than 30% were mostly found inside the upper part of the macropore network and lateral branches of the macropore network were significant drier than the downwards directed branches. The visualizations of the water repellent sandy soil revealed several 10 to 20 cm wide ''fingers'' starting around 10 cm depth at locations with the highest bulk densities.