Characterizing Karst Conduits. A Major Aspect for Understanding Karst Hydrology

Flow in karst systems is controlled by the geometry (e.g., position, density, structure) and characteristics of the karst conduit network, which drains the aquifer toward the karst spring. Many examples show that it is impossible to evaluate the transit of pollutants or to develop the water resource without considering the existence and the characteristics of the karst conduit network. Innovative methods are being developed for this purpose. The approach is the analysis of the geometry of known conduit networks. Cavers provide much data that can be analysed by various methods. The analysis shows that most conduits develop along a restricted number of discrete planes within the limestone mass. Conduits are located along intersections between those planes and the main fractures. The “inception horizon hypothesis” can be derived directly from this analysis. This hypothesis provides a consistent framework for evaluating why conduits are concentrated along some discrete planes and predicting which planes are karstified. Another approach is to infer the conduit network characteristics from the spring response. Many methods are available in the literature, but only a few of them truly take into account the presence of the drainage network. Some interesting investigations using numerical models have been attempted over the last few years which shed some light on this approach. Geophysics is another approach for locating conduits. Electromagnetic and seismic methods likely are the best suited, although they are still very imprecise and the depth of their investigation remains very limited. Lastly, conduits can be explored by cavers, divers, or robots. New positioning methods are being developed that allow the precise positioning of cavers or divers and the first robots are being developed for exploring conduits (or mines).