World's hidden groundwater mapped by Canadian scientist

File photo.

Monday, November 16, 2015, 5:00 PM - Groundwater -- the water held in the cracks in soil and in the pores of rocks -- is a precious resource that has never been fully quantified.

The need to know how much groundwater Earth has has become increasingly important in recent years, due to unprecedented drought in California and long heat spells elsewhere.

Now, a new study led by B.C.'s University of Victoria has provided the first-ever data-backed estimate of the Earth's total groundwater supply. The paper was led by Dr. Tom Gleeson, in collaboration with researchers from the University of Texas at Austin, the University of Calgary and the University of Göttingen.

The team used multiple datasets to estimate the world holds 22.6 million cubic kilometres of groundwater. About 96 per cent is 'old' groundwater and non-renewable six per cent is 'modern' and renewable. 

Old groundwater is found at a greater depth and often sourced for agriculture and industrial projects. Modern groundwater is closer to the surface and more vulnerable to climate change and contamination from pesticides, detergents and other pollutants.

Researchers say this could pose a potential problem, given that modern groundwater is renewed slowly over many years. It supplies water to aquifiers and wells that more than a third of the world's population -- and more than a third of Canadians -- rely on, but the study found this resource could eventually run out.

According to the paper, only six per cent of the world's groundwater is replenished in 50 years' time.

"This has never been known before," Dr. Gleeson said in a statement.

"We already know that water levels in lots of aquifers are dropping. We're using our groundwater resources too fast--faster than they're being renewed." 

Good news and bad news

The good news is even at 6 percent, the amount of available renewable groundwater is significant. At 0.35 cubic kilometres, there is three times more modern groundwater than all other freshwater contained in the Earth's lakes and rivers.

The bad news is it isn't evenly distributed and there is less modern groundwater in arid regions.

Dr. Gleeson told the CBC parts of California and the U.S. Midwest are already being forced to tap into 'non-renewable' water that is thousands of years old.

In Egypt, water that was last renewed an estimated 1 million years ago is being sourced. In addition to this water being non-renewable, it tends to be higher in contaminants and have a saltier taste.

Researchers hope the paper will inspire the public to conserve water.

The complete findings have been published in Nature Geoscience.

Sources: University of Victoria | CBC | Nature Geoscience