Geoelectrical Monitoring of Complex Hydrological Processes in a Riparian Wetland

Wetlands or groundwater dependent ecosystems in general provide vital habitats for diverse aquatic and terrestrial flora and fauna. Such systems usually show a highly complex hydrological regime and are very sensitive to environmental changes. Thus non-invasive methods have to be used to investigate those processes. This paper presents the application of 2D geoelectrical monitoring to such environments which is, due to its high sensitivity to changes in moisture content and pore water resistivity, aiding in improving our hydrological understanding of these systems. After correcting the resistivity data for the seasonal temperature variations, our results highlight the need to divide the alluvium into two hydrological layers showing different characteristics. While the uppermost layer shows significant responses from biogeochemical cycling, with decreasing resistivities during spring and summer, the lower part of the alluvium shows increasing resistivities due to upwelling of more resistive pore waters from the underlying gravels. These processes, and thereby also the resistivity changes, were proven by sensors at different locations and depths, showing the same results, but with higher accuracy and sampling rate.