Groundwater ‘time bomb' warning from scientists

In many parts of the world it could take 100 years for climate change to affect the availability of freshwater trapped underground, research suggests.

Future generations face an “environmental time bomb” caused by the effects of climate change on groundwater, scientists have warned.

In many parts of the world it could take more than 100 years for the full impact  of changes occurring today to be felt by groundwater systems, new research shows.

This has major implications for the future availability of fresh water for drinking, irrigation and industry, it is claimed.

Groundwater is water trapped underground in cracks and spaces in soil, sand and rock.

Illustration showing groundwater trapped in porous rock (Geoff Ruth/Wikimedia Commons/PA)

It is the largest source of usable freshwater in the world and relied upon by more than two billion people.

Groundwater is replenished chiefly by rainfall through a process known as “recharge”.

At the same time it is constantly discharged into lakes, streams and oceans.

But the groundwater balance could be upset by climate change – for instance, as a result of reduced rainfall, said the researchers.

Levels of water in the ground will then begin to change until a new equilibrium is reached.

Lead scientist Dr Mark Cuthbert, from the University of Cardiff’s School of Earth and Ocean Sciences, said: “Our research shows that groundwater systems take a lot longer to respond to climate change than surface water, with only half of the world’s groundwater flows responding fully within ‘human’ timescales of 100 years.

“This means that in many parts of the world, changes in groundwater flows due to climate change could have a very long legacy.

“This could be described as an environmental time bomb because any climate change impacts on recharge occurring now, will only fully impact the baseflow to rivers and wetlands a long time later.

“It is essential that the potential for these initially hidden impacts is recognised when developing water management policies, or climate change adaptation strategies for future generations.”

The scientists based their findings on groundwater computer simulations together with hydrological data.

They found that groundwater in wetter, more humid locations may respond to climate change on relatively short time scales.

In contrast, regions where water was naturally more scarce had much longer groundwater response times.

The authors, whose results appear in the journal Nature Climate Change, pointed out that groundwater was essential in drier parts of the world where surface water supplies were limited.

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