Karst is a complex hydrogeological object requiring dedicated and original approaches and models. SNO KARST aims to generate scientific questions and advances, specifically in terms of modeling hydrogeochemical flows at the outlet of karst hydrosystems, or the links between global changes and the physico-chemical composition of water at the interface between hydrological and hydrogeological compartments. Particular attention is paid to the link between data and models, in order to better understand the physics and chemistry of the environment, and to enhance the ability of models to reproduce variations in flows and materials. It should also be noted that the carbonate rocks that host karst systems are eminently “fragile” materials when it comes to erosion and weathering, and that these mechanisms are themselves highly conditioned by expected changes in climate, hydrological and rainfall regimes. This makes karsts even more vulnerable on relatively short time scales, a characteristic that is generally less prevalent in conventional hydrosystems that are deeper or have slower water dynamics. The aspect of matter transfer and participation in major biogeochemical cycles is also a major concern of this SNO, all the more so as karst systems are highly vulnerable to changes in surface boundary conditions.
SNO KARST is an ideal place to bring together all current observation and research activities on karst aquifers, to compare and unify approaches (tools, methods, concepts). These players are working to develop tools to characterize and model the evolution of water resources (qualitative, quantitative) in response to short-, medium- and long-wave drilling, in different physiographic, geological and climatic contexts. Our aim is to develop a “synthetic” approach on the scale of major karst typologies, from characterization of their structure and functioning to hydrodynamic and hydrogeochemical modeling of transfers. To achieve this, we need to establish long-term monitoring of the various natural laboratories.
For example, we need to identify the intrinsic variability of water resources in these hydrosystems, by attempting to differentiate the impact of climate variability from the impact of global change on the scale of the karst basin. To do this, we need to characterize the specific non-linearity of karst in terms of its hydrodynamic or hydrochemical response to external stresses, as well as the role of the various compartments in this non-linearity. The existence of long chronicles, specific to one or other of the karst compartments depending on the observatories, as well as the expertise of each of the teams participating in this SNO, will enable us to address this issue.
Another challenge for SNO KARST is to propose a systemic and generic approach to karst. In many respects, this generic approach can be compared with what is currently being developed at the meso-scale for 3D surface-underground integration of fluid dynamics and material flows in a watershed. In the specific case of karst, flows in the unsaturated zone (UZ) and saturated zone (SZ) cannot be understood using fine-grained physics, due to a lack of knowledge of flow geometry and channelization. It therefore seems necessary that, at least for flows, this ZNS - ZS part of the system be apprehended in a homogenized, or even systemic, form. For example, we need to identify the intrinsic variability of water resources in these hydrosystems, by attempting to differentiate between the impact of climatic variability and the impact of global change on the scale of the karst basin. To do this, we need to characterize the specific non-linearity of karst in terms of its hydrodynamic or hydrochemical response to external stresses, and the role of the different compartments in this non-linearity. The existence of long chronicles, specific to one or other of the karst compartments depending on the observatories, as well as the expertise of each of the teams participating in this SNO, make it possible to address this issue.