Estimating epikarst water storage by time-lapse surface to depth gravity measurements

In this study we attempt to evaluate the magnitude of epikarstic water storage variation in various karst settings using a relative spring gravimeter. Gravity measurements are performed two times a year at the surface and inside caves at different depths on three karst aquifers in southern France: two limestone karst systems and one dolomite karst system. We find that water storage variations occur mainly in the first ten meters of karst unsaturated zone. Afterward, surface to depth gravity measurements are compared between the sites with respect of net water inflow. A difference of seasonal water storage is evidenced probably associated with the lithology. The transmissive function of the epikarst has been partially deduced from the water storage change estimation. Long (> 6 months) and short (