Squeezed dry

by Tim Hornyak, BA’95

McGill hydrogeologist Tom Gleeson (Photo: Claudio Calligaris)

With more than 75 percent of the U.S. suffering extreme drought this summer, farmers can’t be blamed for looking to underground aquifers for relief. But a new analysis of groundwater shows that people are already overusing these subterranean sponges, some of which took thousands of years to form.

“Over 2 billion people drink groundwater everyday, and groundwater is important for growing food in many regions,” notes McGill hydrogeologist Tom Gleeson, who co-authored the study in the journal Nature. “Our results show that humans are over-exploiting groundwater in many large aquifers that are crucial to agriculture, especially in North America and Asia, and that a quarter of the world’s population live in regions where groundwater is being overused.”

Gleeson’s team, including researchers from Utrecht University in the Netherlands, developed an analysis tool called a groundwater footprint. It measures the amount of water flowing into aquifers, how much humans use, and how much should be left for the environment. It’s being heralded as the first measure of the sustainability of groundwater use around the world.

The researchers used this tool to examine data on water use from across the globe. While most sources of groundwater are not threatened, the study identified heavily overtaxed aquifers feeding population centres such as the Upper Ganges of India and Pakistan, California’s Central Valley and the North China Plain.

Getting billions of people to change their water use is a daunting task, and Gleeson, an assistant professor of civil engineering, says a multi-pronged approach is needed.

“A wide variety of water policy, management and governance options are possible for these regions that are being overused,” says Gleeson. “Options include setting limits on groundwater use, more efficient irrigation and the promotion of less meat-rich diets since they use less water.”