Hydrogeophysical monitoring of intense rainfall infiltration in the karst critical zone: A unique electrical resistivity tomography data set

The common hydrogeological concepts assume that water mostly enters and flows in fractured and karstified media through preferential pathways related to discontinuities. But it is difficult to locate discontinuities and even more to relate those to possible or effective water routes, particularly when soil or scree covers near surface features. When and where does water flow underground? How fast? Are we able to monitor the infiltration processes? A unique large scale Electrical Resistivity Tomography (ERT) surface based timelapse experiment was carried out in fractured and karstified carbonate rock during a typical Mediterranean autumn rainy episode (230mm of rain over 17 days). 120 ERT timelapse sections were measured over the same profile during and after this event (30 days). The gradient array was chosen for his robustness and rapidity. The site is covered by typical Mediterranean forest and is a good example of the surface conditions found in Mediterranean karst. There is no major karstification features (i.e. cave, sinkhole) or major tectonic accident (i.e. fault). In a previous paper, several commercial and research inversion software were tested on this dataset. This processing highlighted some limitations in in version process. At the actual stage, apparent resistivity data provides insight about recharge/discharge processes that are almost valuable as the inverted resistivity results. Due to his quality, the availability of this unique dataset acquired under natural conditions will allow to the scientific and engineer community exploring advances and limits of ERT approach and to test new software or new data processing strategy. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Automated summary

Traditional hydrogeological concepts assume that water enters and flows through fractured and karstified media, but it is difficult to locate discontinuities and relate them to water routes near surface features. This study conducted a large-scale Electrical Resistivity Tomography (ERT) experiment to investigate fractured and karstified carbonate rock during a Mediterranean rainy episode. The research measured 120 ERT sections and used apparent resistivity data to gain insights into the recharge/discharge processes.