Electrical Resistivity Tomography (ERT) as a Tool for Monitoring Moisture Dy-namics in Soil Filled Containers

The geophysical subproject of the multidisciplinary research group INTERURBAN (DFG 409), formed to investigate the water- and solutedynamics at urban locations with particular attention to spatial heterogeneity and biological transformation processes in the unsaturated zone, aims at the development of a noninvasive conception to map the water distribution and dynamics at small scales. Hydrophobic areas have a major impact for the transport of water and matter through preferential flow in soils. Soil animals, e.g. earthworms, modulate the composition of soil solutions in time and have a species-specific impact on the release pattern of nutrients and pollutants from plants and soil. To assess the possibilities and limitations of 3D ERT in the cm-dm range to monitor the long and short term dynamics of water repellent zones in the presence of soil fauna activity a feasibility study was carried out using soil filled mesocosms (MC) inoculated with earthworms. Results indicate a sufficiently high spatial resolution and sensitivity to reliably monitor in-situ changes of soil moisture on the relevant scales, Earthworm inoculated MC indicate a more homogenous decrease of resistivity throughout the MC whereas in the reference MC the changes are confined to the area below the irrigation zone.