Scientists tally Earth's hidden mega-stashes of groundwater

A new study updates the research on the amount of groundwater beneath the Earth's surface: 6 quintillion gallons.

Gleeson, et al/Nature Geoscience
University of Victoria’s Tom Gleeson, and colleagues from the University of Texas at Austin, the University of Gottingen, and the University of Calgary, have mapped the Earth's groundwater.

The first comprehensive study of the planet's groundwater revealed not only how much of Earth’s water lies beneath its surface, but also how old it is.

The study, published Tuesday by the journal Nature Science, followed up on a hasty estimate of the planet's water supply that had not been updated since the 1970s, according to a press release. 

The water beneath the Earth's surface would - if somehow spread horizontally in something resembling an epic remake of "The Ten Commandments" - cover the continents with 600 feet of water. That is a volume of 6 quintillion gallons, wrote Deborah Netburn for the Los Angeles Times.

"This has never been known before," said lead author Tom Gleeson from the University of Victoria in a press release.

Most of this water, it turns out, is quite old. Researchers gathered data on which bodies of water had trickled underground less than 50 years ago. They were interested in studying how quickly water is traveling back up to the surface and into the regular water cycle, as well as determining if “newer” water contained acids or pollutants from surface industrialization.

The vast majority –  94.4 percent – of underground water has been there for more than 50 years, meaning only about 5 percent of the planet’s underground reservoir has seen the sun recently, George Dvorsky wrote for Gizmodo. The fresh, young water closer to the surface is purer and much easier for humans and other life to use, but the older water deeper down can be saltier than ocean water and sometimes contains arsenic and uranium.

Humid land areas such as the Amazon, the Congo, Indonesia, and the Rocky Mountains had high levels of groundwater. The Sahara Desert and the Australian Outback did not. 

"Intuitively, we expect drier areas to have less young groundwater and more humid areas to have more, but before this study, all we had was intuition," said co-author Kevin Befus, who studied groundwater for his doctoral thesis at the University of Texas at Austin, in a press release. "Now, we have a quantitative estimate that we compared to geochemical observations." 

A map shows concentrations of groundwater on all the continents except the northernmost and southernmost land masses, for which there is no data, but the permafrost in these areas likely contains little groundwater, according to Gizmodo.

Researchers used multiple datasets, 40,000 groundwater models, and data from more than a million watersheds, according to a press release. They found 23 million cubic kilometers of underground water.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.