Climate change is scary not just because of the direct problems it’s causing, but also because of its ability to exacerbate other problems. In particular, many of the ways we have to deal with higher temperatures require increased use of water. More water for agriculture, more water for drinking, and more water for evaporative cooling of various sorts.

This combines uncomfortably with the incredibly high rate at which we use fresh water, the trend of privatizing water sources, and the widely reported depletion of aquifers. The danger of lethal water shortages is very real, and has a lot of people worried about mass famine, thirst, and war as a result. It’s a valid cause for worry, particularly with the current political climate of the world.

Given all of that, it’s nice to have a little good news now and then, and this bit comes to us from a recent publication in the journal Earth Systems Dynamics that suggests that the world’s large aquifers are in less danger than previously feared, and more resilient to climate change than previously hoped. From the research team’s press release:

Previous global studies of changes in groundwater storage, estimated using data from the GRACE (Gravity Recovery and Climate Experiment) satellite mission and global models, have concluded that intensifying human water withdrawals in the majority of the world’s large aquifer systems are causing a sustained reduction in groundwater storage, depleting groundwater resources.

Yet this new study, published in Earth System Dynamics, reveals that depletion is not as widespread as reported, and that replenishment of groundwater storage depends upon extreme rainfall that is increasing under global climate change.

Lead author, Dr Mohammad Shamsudduha, Lecturer in Physical Geography and a member of the Sussex Sustainability Research Programme at the University of Sussex, said: “The cloud of climate change has a silver lining for groundwater resources as it favours greater replenishment from episodic, extreme rainfalls in some aquifers located around the world mainly in dry environments. This new analysis provides a benchmark alongside conventional, ground-based monitoring of groundwater levels to assess changes in water storage in aquifers over time. This information is essential to inform sustainable management of groundwater resources.”

This new study updates and extends previous analyses, accounting for strong seasonality in groundwater storage in the analysis of trends. It shows that a minority (only 5) of the world’s 37 large aquifers is undergoing depletion that requires further attention for better management.

Co-author, Professor of Hydrogeology, Richard Taylor from UCL Geography, said: “The findings do not deny that groundwater depletion is occurring in many parts of the world but that the scale of this depletion, frequently associated with irrigation in drylands, is more localised than past studies have suggested and often occurs below a large (~100 000 km2) ‘footprint’ of mass changes tracked by a pair of GRACE satellites.”

For the majority, trends are non-linear and irregular, exhibiting considerable variability in volume over time. The study shows further that variability in groundwater storage in drylands is influenced positively and episodically by years of extreme (>90th percentile) precipitation.

For example, in the Great Artesian Basin of Australia, extreme seasonal rainfall over two successive summers in 2010 and 2011 increased groundwater storage there by ~90 km3, more than ten times total annual freshwater withdrawals in the UK. Elsewhere in the Canning Basin of Australia, however, groundwater depletion is occurring at a rate of 4.4 km3 each year that is associated with its use in the extraction of iron ore.

This doesn’t mean that there are no problems, and the study’s authors still advocate that measures be taken to reduce groundwater depletion. Even so, it’s nice to know that the bigger storms aren’t just creating temporary deluges that run off into the oceans – they also replenish aquifers, more than we previously knew.

There remains the danger of contaminating aquifers through industrial activity like fracking and the storage of fracking wastewater, but that is, in theory, a problem we can avoid in pursuit of mitigating our climate impacts, that will also help conserve our sources of potable water.

As ever, the goal is to avoid the creation of a Mad Max hellscape, and increased resilience in our planet’s aquifers gives us an additional buffer against that.

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