The first comprehensive study in decades of the world’s aquifers found that most groundwater doesn’t renew itself in the span of a human lifetime.
The international team of scientists found that so-called “modern” groundwater — younger than 50 years — is only about 6 percent of the world’s groundwater resources.
That means humans often rely on older groundwater, which can take hundreds or thousands of years to replenish with rainfall and snowmelt. In dry places like the American Southwest, recharge can be even slower.
The researchers say modern groundwater is still a vast resource on the planet. Its estimated volume is three times the amount of the world’s surface freshwater lakes and rivers.
A radioactive isotope was used to map the age of groundwater. Levels of this isotope rose sharply during the Cold War when nuclear testing affected the chemical content of rainfall.
The research was published in Nature Geoscience in November.
Groundwater Depletion In The U.S.
