A multi-method recharge estimation tool applied to four contrasted karstic systems (France): a simple and robust approach

International audience; Managing groundwater for a given territory from a quantitative standpoint should be based on a precise estimation of the available resource. Quantifying groundwater resource is necessary in order to see if it can supply the water demand of the territory dependent on it. For some systems, such as karstic aquifers, the resource estimation can represent a huge challenge due to the limited knowledge in terms of geometry and structure. One way to provide water managers with an operational assessment method is to estimate the renewable water resource corresponding to the recharge by precipitation. While such approach may, in some cases, under-estimate the actual renewable resource (for example by neglecting river flows infiltration), it allows comparing situations of contrasted systems and assessing the impact of future climate on groundwater resources availability, in a broad context of a higher water scarcity. A multi-method recharge estimation tool, combining several analytical recharge estimation methods based on climate data, discharges or piezometric levels depending on the method, has been built and applied to four contrasted karstic aquifers in France. These aquifers are: Fontaine de Vaucluse, Loue-Lison, Gillardes and Lez karstic systems subjected to variable climatic and pumping conditions. This study presents a comparative assessment of the results and discusses the issues of uncertainty linked to the estimation method and usefulness of the proposed tool.