Characterizing a coastal karst aquifer using an inverse modeling approach: The saline springs of Thau, southern France

A methodological approach using inverse modeling was used to characterize the functioning of the deep and shallow reservoirs of the Thau karst aquifer system. Three springs were monitored at the convergence of rising saline water diluted with shallow groundwater in karst conduits and unmixed shallow groundwater that behaves as confined groundwater. In such a method, impulse responses of flow and fluxes are combined in order to separate hydrographs. The model explains the salinity and hydraulic head variations of the submarine and inland springs. It confirms and improves the conceptual model of this groundwater system in which mixing of saline and subsurface waters occurs. The different forces driving the upward flowing mixed water into the drainage axis and faults were studied in order to elucidate the springs\u27 functioning. A comparative study of spring functioning is proposed, which clearly shows the very high sensitivity of the groundwater system to changes in recharge and discharge conditions

Vulnerability to Contamination of Karst Aquifers

The karst aquifers are especially vulnerable to pollution due to their hydrologic behavior derived from karstification. The vulnerability mapping is one of the most applied tools to protect them. There are a wide range of methodologies for vulnerability mapping that have been developed for karst aquifer, to consider the specific characteristics of karst into the vulnerability assessment, such as EPIK, PI, COP, Slovene Approach, and PaPRIKa, among others. The vulnerability map can help to the water stakeholder for making decision and to promote a land-use management compatible with the water protection. So the maps should have reliable accuracy. Many works highlight that the maps of groundwater contamination vulnerability obtained by the different methods differ significantly, although they were all obtained by methods developed for karst aquifers, even if they are obtained from the same sources of information and applied by the same person. So, the validation is an essential element of any contamination vulnerability assessment. The current challenge of researchers is to obtain versatile and easy to apply methods to test and validate vulnerability maps