Patterns and drivers of global groundwater drought recovery based on recovery regime classifications

Groundwater resources are under increasing pressure from both human and climatic drivers. Increasing water demands, driven by population growth, urbanisation, and agriculture, are intensifying groundwater abstractions and, at the same time, climate extremes such as prolonged droughts affect groundwater recharge. Given these pressures, it is important to understand if groundwater aquifers are resilient to increasing water demands and whether they can recover from future drought events, or whether they will reach critical tipping points.

Using the global groundwater model GLOBGM^1,2, a physically based groundwater model with a 1km spatial resolution, we assess the spatial pattern of global groundwater drought recovery and its potential drivers. We defined drought periods over the entire simulation period 1960-2019 and gathered additional drought characteristics, including the rate of drought development and recovery, drought duration, and drought intensity. Using these characteristics, we assessed spatial groundwater drought recovery patterns worldwide, finding that the average drought recovery rate is highly variable, not only between regions but also within them. Globally, we have identified four groundwater drought recovery regimes: resilient, stable, vulnerable, or unstable. These regimes are then linked to climatological, societal and geophysical drivers that describe the spatial recovery pattern. We observe that, as expected, climatology plays a key role, however on the local scale geophysical parameters are linked to local recovery patterns and highlight differences in recovery behaviour. Locations in the unstable recovery regime (approximately 26%) show a higher number of drought events, where pre- and post- conditions play a strong role relative to the other regimes. Locations within the vulnerable regime (approximately 15%) differ in terms of geophysical parameters, such as topography and groundwater storage characteristics. Furthermore, strong climate signals in these regions affect drought characteristics, including lower drought frequency and longer duration. High numbers of events, combined with faster development and post conditions, as well as higher groundwater conductivities, are standing out for locations within the resilient regime (approximately 57%).

Using this new recovery regime classification and information on drought recovery drivers can help society to potentially improve groundwater resilience to future droughts, as well as identify regions where tipping points are either exceeded or close.

1) Verkaik, J., Sutanudjaja, E. H., Oude Essink, G. H. P., Lin, H. X., and Bierkens, M. F. P. (2024) : GLOBGM v1.0: a parallel implementation of a 30 arcsec PCR-GLOBWB-MODFLOW global-scale groundwater model, Geosci. Model Dev., 17, 275–300, https://doi.org/10.5194/gmd-17-275-2024
2) van Jaarsveld, B., Wanders, N., Otoo, N.G., Sutanudjaja, E.H., Verkaik, J. Zamrsky, D. and Bierkens, M.F.P: Global hyper-resolution groundwater dataset for assessing historical and future groundwater dynamics. Submitted, Preprint, https://doi.org/10.31223/X5QX7W