A new study suggests the world is depleting underground water reserves faster than they can be replenished. Scientists in Canada and the Netherlands say this is due to over-exploitation.
The researchers are from McGill University in Montreal and Utrecht University in the Netherlands. They combined groundwater usage data from around the globe with computer models of underground water resources to come up with a measure of water usage relative to supply.
That measure shows the groundwater footprint. The area above ground that relies on water from underground sources is about 3.5 times bigger than the aquifers themselves.
The research suggests about 1.7 billion people, mostly in Asia, are living in areas where underground water reserves and the ecosystems that rely on them are under threat.
Tom Gleeson from McGill led the study. He says the results are “sobering” and that they show people are over-using groundwater in a number of regions in Asia and North America.
More than 99% of the world’s fresh and unfrozen water sits underground. Gleeson suggests this huge reservoir could be crucial for the world’s growing population, if managed properly.
The study has been published in the journal Nature. It found that 80% of the world’s aquifers are being used sustainably. But this is offset by heavy over-exploitation in a few key areas.
Those areas included western Mexico, the High Plains and California’s Central Valley in the United States, Saudi Arabia, Iran, northern India and parts of northern China.
Previous research has shown that it takes about 140 liters of water to grow the beans that go into one cup of coffee. It doesn’t matter whether they are cultivated in arid Ethiopia or the Colombian rain forest.
Gleeson has a few suggestions on how to make these water resources more sustainable. He says there needs to be limits on water extraction, more efficient irrigation and the promotion of different diets, with less or no meat.