Water transport in frozen soil is not yet understood sufficiently well for both, qualitative description and modelling. That is in part due to the complex coupling between the energy and water balance at temperatures below 0oC and to the high spatial variability of soil physical properties. An additional complication arises from the assumption that liquid water is transported through two different flow domains, i.e. the liquid water adjacent to the soil particles and the previously air-filled macropores. These two domains are separated by pore ice and are temporally variable.
Heterogeneous water transport in frozen soil cannot be fully characterized by means of a limited number of point or spatially integrating measurements of the hydraulic variables. To get an idea of the flow pattern, cold chamber infiltration experiments with soil columns were carried out, where a dye tracer was added to the applied water. After uni-directional freezing and subsequent infiltration, several cross-sections of the columns were obtained by cutting. The water flow pathways were indicated by the stained regions of the sections, which allowed a three-dimensional description of the infiltration process with a high spatial resolution. The concentration distributions of the dye were obtained by image analysis.
Some preliminary results will be presented. Not only the flow patterns with regard to different soil texture, initial water content, and boundary conditions but also the technical problems and limitations will be discussed.
Daniel Stadler ETH Zurich Soil Physics, Institute of Terrestrial Ecology Grabenstrasse 11a CH-8952 Schlieren SWITZERLAND Phone: +41 1 633 6082 Fax: +41 1 633 1123 E-mail: stadler@ito.umnw.ethz.ch