Evaluation of the Effect of Micro-Topography of a Potato Field on ERT to Assess Soil Moisture Patterns in Sandy Soil

Electrical resistivity tomography is a method that provides a spatial-temporal characterization of the subsurface. In this project, the method is used to monitor a potato field, characterized by a microtopography composed of furrows and ridges. Nevertheless, changes of this micro-topography due to erosion during the growing season could lead to artefacts in the inverted resistivity distribution. To quantify this effect, we first used a hydraulic model with non-uniform infiltration patterns and converted the obtained soil moistures in bulk resistivities. We then conducted a forward modelling with a decrease of the ridge height in the mesh. Afterwards, we used the initial microtopography of the start of the growing season in the inversion and compared the retrieved resistivity distributions to the ones of the hydraulic model. We also compared different array configurations to assess which array is most suitable to retrieve the expected infiltration pattern. Gradient and Wenner configuration were performing best with a coefficient determination coefficient close to 0.9 and a RMS close to 1. The change of ridge height highly impacted the coefficient of determination once the decrease is above 6 cm. Nevertheless, pattern between furrows and ridges can still be retrieved qualitatively up until a decrease of 10 cm.