Ecohydrological partitioning through the critical zone drives groundwater recharge: an isotopic approach

In times of accelerated global change, integrated tools are urgently needed that allow process-based, quantitative assessment of how climatic drivers interact with land cover, soil water conditions and hydrogeology to control the inter-relationships between water fluxes and storage in the Critical Zone (CZ). These dynamic relationships determine the availability and quality of water resources during droughts at multiple spatial and temporal scales. This talk will present approaches to investigate the relationships between water fluxes through and storage in the CZ, together with the associated water ages and residence times. The focus will be on groundwater recharge, as groundwater levels have been dramatically affected by the recent extreme droughts in large parts of Central Europe. Multiple ecohydrological processes and transformations within the CZ are influencing groundwater recharge by partitioning incoming precipitation into green (i.e. evaporation and transpiration) and blue (i.e. groundwater recharge and streamflow generation) water fluxes.

Water stable isotopes help to constrain ecohydrological process understanding in the CZ. Incorporating isotopes into tracer-aided ecohydrological models allows water flux, storage and age dynamics to be quantified in both plot und catchment scale modelling. Using such novel analysis of the spatio-temporal interactions of water flux-storage-ages in the CZ improves understanding of the sensitivity and resilience of catchment functionality to hydroclimatic perturbations, and provides science-based evidence on which land management techniques have the potential to modify green water fluxes and to conserve soil water storage, to guide decision-making and build resilience to future droughts.