Hydrogeological model to study natural water flow in karstified and fractured aquifers

Many studies deal with the evolution of karst processes in fractures and conduits within the epikarst, the vadose zone and the phreatic zone of karstified limestone rock masses. Details about the geo-structural setting and the underground conduit pathways and connections can be obtained from the integration of geological/ speleological surveys and tracer tests. These methods are aimed to collect geomorphological, geo-structural, stratigraphic and petrological data at the surface and inside the cave systems, to combine with information derived from tracer tests (i.e. δO18 - δ13C stable isotopes). Whatever the approach, the choice of the best hydrogeological model, i.e. the best way to simulate the water flow through a karstified aquifer, is a very complex problem due to the difficulties to gather detailed geological and hydrological data. The lack of information often leads to several uncertainties on the assumptions of the starting model, namely as regards the underground water movements, the delimitation of the hydrogeological catchment, and the thickness of the saturated zone. The final goal of this research is to build the most suitable conceptual hydrological model, which may allow implementing a realistic simulation of the karstified and fractured groundwater flow. This aim will be obtained by a detailed investigation of the cave systems and the surrounding superficial areas, merging classical geological surveys and speleological investigations. So far, we are able to present the exploration results of the Apulian cave “Inghiottitoio di Masseria Rotolo”, located in the Canale di Pirro polje (Low Murge - Monopoli, Italy). It has been discovered in 2012 and totally develops inside Cretaceous limestones belonging to Apulian Carbonate Platform. The cave reaches water table at the depth of - 264 meters below the ground; diving explorations, carried out during 2018, have brought the total depth of the karst system at - 324 m, making it the deepest cave in Apulia. Inghiottitoio di Masseria Rotolo is a remarkable cave system, characterized by very large passages, including very impressive vertical shafts, with presence also of extremely rich in speleothems rooms. This extraordinary situation represents a real natural, hydrogeological, field-scale laboratory, to direct study both the groundwater and karst conduits outflows, giving the opportunity to collect precious data to better support the hydrogeological conceptual and mathematical model of the Cretaceous limestone rock mass.