Ninety-nine percent of Earth's liquid freshwater supply sits in the ground beneath our feet, where it fills the spaces between grains in the soil and the small holes in porous rocks. In other words, 99% of the planet's liquid freshwater supply is invisible to us, which is part of the reason most of us don't notice that it's disappearing.
But over the past decade, thanks to a pair of satellites orbiting 300 miles above Earth's surface, researchers have been keeping tabs on the seasonal ups-and-downs in groundwater stores all over the world, and tracking longer-term trends like the depletion of the Ogalalla aquifer under the southwestern U.S.
This year, a few designers took the data from the GRACE satellites' gravity measurements and created some stunning visualizations that allow us to see, for the first time, the resource we rely on most.
The seasonal swells and dips in groundwater level are especially cool in this one:
Credit: Roxana Torre, via Visual.ly
This annotated version shows some notable cases of both drought and surplus--check out the Amazon during monsoon season:
Credit: Richard Vijgen
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.