Patterns and drivers of global groundwater drought recovery

Abstract

Groundwater resources are under increasing pressures, due to changes in climatic and anthropogenic drivers. Meanwhile extreme drought events can strongly affect the resilience of groundwater systems, due to decreased groundwater recharge and increased groundwater abstraction to meet increasing water demands. As groundwater systems tend to respond on a longer timescale, it is important to understand how these systems recover from these drought events back to normal levels. This study provides the first global study of groundwater drought recovery based on high-resolution simulations of a global groundwater model. We find that the spatial variability of the groundwater drought recovery rate is mostly influenced by the local climate, while local geophysical attributes such as topography and aquifer storage capacities can account for regional differences. We introduce a classification of groundwater drought recovery regimes (resilient, stable, vulnerable, and unstable) based on drought event-specific recovery rates, which allows us to identify the resilience of groundwater systems around the world. We observe that areas sharing similar average recovery rates can differ in their underlying recovery regime and controlling drivers. Resilient regions, covering the majority of locations (57%), exhibit rapid and robust recovery following droughts. Vulnerable (15%) and stable locations are shaped by geophysical constraints and heightened climate variability, whereas unstable regions (26%) are characterised by frequent, successive drought events leading to a reduced drought recovery capacity. By systematically relating recovery regimes to drought characteristics, environmental and anthropogenic factors, our findings offer insights into the mechanisms that influence groundwater drought resilience. These results show that integrating regional climatic, geophysical and anthropogenic aspects into groundwater management practices is important and could potentially support the identification of regions at risk of crossing critical thresholds and support the development of targeted strategies to enhance global groundwater resilience in the face of climate and anthropogenic changes.