Integrating field work, large sample hydrology and modeling to inform (inter)national governance of karst water resources

Substantial changes of climate and land use are projected in many karst regions in the world for the next decades. Despite these projections, only few studies have been performed to quantify the impact of climate change and land use change on karst water resources. This is mainly due to a lack of observations of the karstic recharge and groundwater dynamics, which is prohibiting the development large-scale karst simulation models. Here we present the advances of the first global effort to develop a simulation tool to support (inter)national governance of karst water resources. Using a global soil moisture monitoring program and a global database of karst spring discharges, we evaluate the simulations of a preliminary global karstic groundwater recharge model. We show that soil moisture is a crucial variable to better distinguish recharge dynamics in different climates and for different land cover types. Analyzing the global dataset, we find that mean discharge volumes, their variability and the recharge areas are showing similar variability for a large range of altitudes. Comparing the model simulations with the newly collected observations, indicates that (1) improvements of the recharge model are still necessary to obtain a better representation of different land cover types and snow processes, and (2) there is a need to incorporate groundwater dynamics. Applying and strictly evaluating these improvements in the model will finally provide a tool to identify hot spots of current or future water scarcity in the karst regions around the globe thus supporting national to international water governance.