Is Jay Famiglietti the Al Gore of the global groundwater crisis?

You might think so, given that the scientist at NASA's Jet Propulsion Laboratory has been beating the drum for years about an environmental issue to which few seemed to pay much attention. (And yes, he has slides.) In 2011, Famiglietti appeared in Last Call at the Oasis, a documentary about a burgeoning world water catastrophe. (Like An Inconvenient Truth, the movie was produced by Participant Media, TakePart’s parent company.) It was a little before its time. Then California’s devastating drought started grabbing headlines, and Famiglietti’s warnings that we were pumping irreplaceable groundwater at unsustainable rates started to look prescient.

Now in a paper published in the journal Nature Climate Change, Famiglietti reveals new satellite data that shows that as drought takes hold around the world, the planet’s major aquifers are being drawn down at an alarming clip—far faster than they can be replenished by rain and runoff.

“Nearly all of these underlie the world’s great agricultural regions and are primarily responsible for their high productivity,” Famiglietti wrote. “Vanishing groundwater will translate into major declines in agricultural productivity and energy production, with the potential for skyrocketing food prices and profound economic and political ramifications.”

“Further declines in groundwater availability may well trigger more civil uprising and international violent conflict in the already water-stressed regions of the world, and new conflict in others,” he added.

That doom and gloom is backed up by data produced by a satellite program called Gravity Recovery and Climate Experiment that measures tiny changes in an area’s gravitational pull to determine its groundwater capacity.

The map below shows just how fast groundwater reserves are being drawn down.

GRACE surveys show, for instance, that the Northwestern India aquifer that straddles two antagonistic nations, India and Pakistan, has been depleted at a rate of 17.7 cubic kilometers a year since 2013. Another highly volatile region, the Northern Middle East aquifer, underlies Iran, Iraq, Syria, and Turkey. Those often warring countries pump 13 cubic kilometers a year from the aquifer. Two of the United States’ biggest groundwater reservoirs are the Central Valley aquifer in California and the Ogallala aquifer, which stretches from South Dakota to Texas. Farmers and cities are sucking up a combined 15.6 cubic kilometers of water annually from those reserves.

It’s a vicious cycle. As climate-change-triggered droughts become more frequent and persistent with a warming world, people will pump more groundwater. That in turn leads to lower flows in rivers, which prompts more extraction of groundwater, according to a study on the Colorado River Basin that was published in July.

So why aren’t policy makers freaking out, especially since groundwater stored in subterranean reservoirs supplies a third of the world’s water?

Like greenhouse gases in the atmosphere, groundwater depletion is largely out of sight, out of mind. While the impact of drought can readily be seen in empty riverbeds and dry lakes, groundwater is invisible.

What’s more, scientists don’t even know how much groundwater the planet has left.

“Very few major aquifers have been thoroughly explored in the manner of oil reservoirs,” wrote Famiglietti. “As a result, the absolute volume of groundwater residing beneath the land surface remains unknown.”

In an email, Famigliett said that's only partly a technological challenge. "The main obstacle is that very few people actually understand that we don't know how much water we have," he said, noting that government agencies tackling groundwater issues are underfunded. "There remains a major disconnect about this issue."

What’s to be done?

Famiglietti advocates a global effort to quantify groundwater reserves and increase agricultural efficiency, as nearly 80 percent of the world’s water is used to grow crops.

“One problem that I fully appreciate is that policymakers have several crises to deal with, not just the groundwater crisis, so keeping the focus on water has been a challenge,” he said.