Multidisciplinary approach to assess hydrology of karst vadose zone: from Han-sur-Lesse cave to the Rochefort Cave Laboratory (Belgium).

The role of the vadose zone in karst aquifers is under the scope of the multidisciplinary project KARAG (www.karag.be). This paper shortly describes an innovative methodology to highlight transfer and storage characteristics of the unsaturated zone. This long term and multi-scale methodology was applied in two karstic areas in southern Belgium. First of all, stalactite drip-water discharges were recorded continuously since 2008 in the cave of Han-sur-Lesse. Data coming from 3 monitoring sites give valuable information about the hydrogeological behavior of the vadose zone in this folded Devonian limestone aquifer. A first descriptive approach allows to identify the existence of temporary epikarst storage in the vadose zone as well as the regularity of this storage with time. Dye tracing experiment in the unsaturated zone also precise the transfer and storage dynamic of infiltration water (Poulain et al. 2015).