Environmental tracing, an indicator for heterogeneities of the karst hydrosystem

International audienceThe calcareous media contains discontinuous groundwater bodies, ranging from fissured quasi-homogeneous aquifers to highly karstified ones, according to their geological history. Three levels of heterogeneities can be classified in carbonate areas: vertical, with an unsaturated zone splitted into epikarst and unsaturated zone, laying upon the saturated zone, spatial with microfissured blocks surrounded by conduits and annex-to-drain subsystems, in the recharge with diffuse infiltration, locally concentrated in karst depressions, and finally pin-point recharge in ponors. This huge diversity, because of variable geochemical conditions induced by environmental conditions (open or closed media vs oxygen or carbon dioxyde, hydraulic conductivity and related residence time,...) is able to set specific tracings, visible at the outlets of the system (springs, boreholes), despite the rather homogeneous lithological context