Tropical Groundwater Resources Benefit From Fewer, But More Intense Rainfall

Tropical groundwater resources may be able to stand up to the challenges imposed by climate change, researchers from the University College London (UCL) and the University of Calgary report in a new study. Generally speaking, global warming leads to fewer but more intense rainfalls. However, this precipitation pattern seems to adequately recharge vital sources of freshwater.

Groundwater is an invaluable source of freshwater across the tropics, providing safe drinking water and a source of agricultural irrigation. It follows then, the replenishment of these sources is vital for sustaining the livelihoods and ecosystems that depend on the availability of freshwater. 

For their study, researchers assessed the chemical signatures in precipitation and groundwater at 15 sites spread out across the tropics. This allowed them to compare the stable isotopes of hydrogen and oxygen found in these water molecules, from which they can interpret how heavy rainfalls impact groundwater recharge in surrounding areas. In terms of their study, heavy rainfall was defined as those exceeding the 50th percentile of local rainfall intensity. Therefore, their results suggest that groundwater recharge occurs disproportionately from heavy rainfalls, but the processes that carry intensive rainfall to groundwater systems and enhance the resilience of tropical groundwater storage as global temperatures rise remains unknown.

"Our results suggest that the intense rainfall brought about by global warming strongly favors the renewal of groundwater resources. As over half the world's population is predicted to live in the tropics by 2050, dependence on groundwater as a resource will continue to rise," Professor Richard Taylor, one of the study researchers from the department of Geography at UCL, explained in the university's release. "It is important to note that the results simply indicate a tendency towards increased groundwater recharge from extreme rainfall. Other influences on groundwater storage including excessive pumpage, substantial changes in total precipitation, and land-use change can undermine and overwhelm this resilience of groundwater resources in the tropics to climate change."

Their findings, recently published in the journal Environmental Research Letters, could be used to develop better strategies for groundwater usage that accommodate for the variability in rainfall and river discharge brought on by climate change.

"Groundwater is a life-sustaining resource for many people in the tropics. Future research will explore how the combination of climate change and pumping will impact the availability of groundwater supplies across the tropics," Dr. Scott Jasechko, study leader from the University of Calgary, concluded in a statement. 

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