When the rain returns, why doesn’t groundwater?
A few days of rain does not change the low groundwater levels after a long drought. To better determine how groundwater systems recover after a drought and which groundwater reserves are most vulnerable, hydrologist Sandra Hauswirth developed a method to classify groundwater systems based on their ability to recover from long droughts.
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With a very high-resolution global groundwater model (one kilometre), it was possible to determine and analyse how a groundwater system responded during a drought and how quickly it could recover. This provided policymakers with the means to better respond to or prevent severe groundwater problems in the future.
Hauswirth investigated the various factors that make groundwater recover or not after a period of drought by looking at a large range of groundwater drought events around the globe. Climate played a major role, but at the local level the geology and landscape are additional important factors for drought recovery.
Looking at these different drivers, she was able to make a classification of groundwater systems. It turned out that the majority of locations had resilient groundwater systems (57 per cent), exhibiting rapid and robust recovery following droughts. Vulnerable (15 per cent) and stable locations are shaped by geophysical constraints and heightened climate variability, whereas unstable regions (26 per cent) are characterised by frequent, successive drought events leading to a reduced drought recovery capacity and strong effects on the groundwater system.
This study provided the first global study of groundwater drought recovery based on high-resolution simulations of a global groundwater model that was developed at Utrecht University, Netherlands.
Her research showed that regional climatic, geophysical, and anthropogenic aspects played a key role in sustainable groundwater management practices. It could support the identification of regions at risk of crossing critical thresholds and support the development of targeted strategies to enhance global groundwater resilience.
Regions and countries already known for their excessive groundwater use, for instance, for irrigation purposes, and declining groundwater trends (such as the USA, Spain, India, or the North China Plain) more often show a complex mix of recovery regimes. These regions are often characterised by many vulnerable and unstable groundwater systems, as a result of groundwater abstraction, compared to less affected regions.
DOI: 10.1088/3033-4942/aea63d