AN UNTETHERED PROBE FOR DROWNED KARST CONDUITS MAPPING AND FLOW CHARACTERIZATION

Karst reservoirs represent an interesting groundwater resource which could, in many cases, be more exploited. Since 50 years, a continuous and positive progression occured in understanding karst groundwater flow processes. This progression lead to, for instance, less uncertain quantitative and qualitative groundwater simulations which are a required for an effective resource management. Studies also showed that even though karst reservoirs are highly anisotropic and heterogeneous, a hierarchicaly organized network of karst conduits concentrate and control flows toward one or several outlets. However, despite the use of artificial tracing experiments or diving exploration, there is still a lack of methodology and knowledge to retrieve precise informations on the conduits' geometry and on the flow conditions throughout these conduits.

Here we present recent advances in the design of an autonomous untethered probe which aims to record in situ measurements throughout its journey into drowned conduits. The probe is constituted by an inertial measurement unit. We test it in increasing complex environments (aerial to aquatic conditions). Our results show that, a slightly positive buoyancy property is needed for effective autonomous transport in aquatic conditions, principal flow orientation can be retrieved and turbulent zones may be identified. We suggest that such probe and the measurements it recorded in controled conditions, present encouraging results to obtain geometries of large and unknown conduits and particular flow characteristics in natural systems.

This new tool and the new type of informations it provides could help reduce uncertainties relative to conduits properties into karst reservoirs and, at some extent, open new developments in karst reservoir exploitation and modeling.