Distribution flow: a general process in the top layer of water repellent soils

Distribution flow is the process of water and solute flowing in a lateral direction over and through the very first millimetre or centimetre of the soil profile. A potassium bromide tracer was applied in two water-repellent sandy soils to follow the actual flow paths of water and solutes in the upper part of the profile. In both fields, distribution flow actually displaced the applied bromide laterally through a very thin layer to locations within the 0-2.5 cm layer, where the soil was the least water-repellent. Here, the highest concentrations of bromide could be found and there was an acceleration in the vertical transport at these sites. Implications for modelling field-scale water and solute flow are outlined.