New map depicts the world’s hidden reserves of groundwater in unprecedented detail

Ecosystems around the world are at risk from declining levels of underground water, a study has found — and protected areas aren’t growing fast enough to stem the losses.

A map released Tuesday in the journal Nature offers the first comprehensive map of the world’s underground water sources and the ecosystems that depend on them.

In drylands and deserts across the world, water bubbling up from the ground provides veins of greenery and life — a phenomenon of the landscape that is particularly concentrated in the often-parched American West or African Sahel.

These groundwater springs are resources that are often hidden and exposed to destruction by agriculture. About 53 percent of the ecosystems identified on the map are undergoing depletion, and of these declining springs, only one-fifth are under any official protection.

This lack of protection is in large part explained by the fact that these ecosystems’ locations had until now “been largely unknown,” said lead author Melissa Rohde, of the State University of New York’s College of Environmental Science and Forestry.

That lack of knowledge hindered “our ability to track impacts, establish protective policies, and implement conservation projects to protect them,” Rhodes added.

So a seven-nation coalition of scientists led by the Desert Research Institute (DRI) and the Nature Conservancy set out to build a map. 

They did so by taking advantage of the major feature of groundwater ecosystems: that they tend to be cooler, wetter and greener than the surrounding landscapes. 

By training computer algorithms on known springs and using that code to analyze detailed satellite maps of the Earth’s surface, they created a map that shows the location of likely springs in unprecedented detail.

On the new map, the American West stands out as particularly reliant on a network of underground water sources — like the hidden water that honeycombs the land around and to the south of Utah’s Great Salt Lake, or Central Colorado.

Some of these hidden water tables are tens of miles across — like one that lies beneath White Sands, N.M. But the real power of the map is in its ability to picture springs that are far smaller, researchers said. 

“We now have the data and technology to capture and analyze information for places the size of a basketball court or a swimming pool, and that we can do this across the entire globe,” said co-author Christine Albano, of the DRI.

That level of detail is important, Albano said, because “it is often the groundwater-dependent springs or wetlands that are about this size, or even smaller, that are the most critical to people and wildlife.”