[en] Through the use of three different geophysical techniques, we highlight structures and groundwater storage changes in the subsurface of a karst system, in the so-called epikarst layer. An Electrical Resistivity Tomography (ERT) has been installed onsite informing on conductivity variations directly related to changes in groundwater content within the unsaturated zone. Both relative and absolute gravimetric measurements monitor the charges and the discharges of the groundwater storage within the epikarst. Analysis of Horizontal to Vertical spectral ratio of seismic ambient noise allows investigating the structure of the epikarst and validating the robustness of ERT data.
