Initiation and Interaction of Macropore Flow during Rainfall Events

Presented at the XXVI General Assembly of the European Geophysical Society
Nice, France, 2001.

abstract

Vertically oriented, continuous morphological structures like earthworm channels significantly influence infiltration into soils. The initiation of flow in these macropores and the water exchange (interaction) from macropores to the surrounding soil matrix govern the flow and transport processes at field scale. This study explores the factors affecting initiation and interaction of macropore flow and the interference of both processes. Sprinkling experiments on different sites with a dye tracer in combination with soil water content and matric potential measurements were carried out. The resultant dye patterns, descriptions of the macropore network, and measured water fluxes have been used to determine factors influencing initiation and interaction. Initiation of macropore flow started either at the soil surface or from a saturated or partially saturated soil layer. The micro topography at the surface and the macropore density directly control the inflow rate distribution in macropores. Only a small percentage of macropores receive a considerable amount of water from initiation at the surface. The inflow rates are almost equal for subsurface initiation. Macropore density, macropore continuity, the size of macropores, soil hydraulic properties, and the water content of the soil matrix determine interaction and losses to the bedrock. The results of this study show that initiation and interaction considerably changes flow and transport processes in the soil and thus the hydrological behaviour during rainfall events.

© Markus Weiler 4/2001