Groundwater evolution in Europe - comparing recharge model outputs with spring discharge from hydroclimatic sensitive karst areas

Groundwater resources are generally evaluated by quantifying groundwater recharge and its storage into the aquifer using for example conceptual or numerical models. Recharge modelling provides a preliminary estimation of the renewable part of the groundwater resource. Moreover, results of regional groundwater recharge models may be used as input data for models on a smaller scale, i.e. at the catchment scale dedicated to water management for present and future conditions. It is thus necessary to constrain the recharge models for example by comparing their outputs to historical long-term observations of groundwater flows that can be derived from time series of groundwater levels or spring discharge.

Karst systems with their high infiltration rate and preferential flow in enlarged conduit networks, react quickly to climatic events and changes. Thus, they can be used as proxies to evaluate the impact of global change on groundwater resources. Karst systems are present in different climatic regions of Europe, which allows comparing long-term trends of groundwater recharge with spring discharge (similar or opposing trends). In our study, two different regional recharge models covering entire Europe – one calculating potential groundwater recharge using simple soil water balance methods and one calculating groundwater recharge over karst areas only using 1-D physical equations for infiltration – are compared to the measured spring discharge from a large European database of more than 100 monitored karst systems. To identify and highlight changes in dominant recharge processes related to changing climatic or physiographic (land cover / land use) conditions, different variables used in the regional recharge models will be correlated to indices describing dynamics of karst spring discharge. The results of our study will help to understand the impact of climatic and groundwater recharge related influences on various geographic locations and give insights on uncertainties in the model structure of the applied regional groundwater recharge models.