A Map of the Future of Water

Global changes are altering where and how we get fresh water, sparking the need for worldwide cooperation

The availability of fresh water is rapidly changing all over the world, creating a tenuous future that requires attention from policymakers and the public.

We know this thanks to 14 years’ worth of satellite data collected by a unique NASA Earth-observing mission called the Gravity Recovery and Climate Experiment—which has the gratifying acronym GRACE. Unlike some satellite missions that rely on images, GRACE, which was launched in 2002 and decommissioned at the end of 2017, was more a “scale in the sky.” It measured the very tiny space-time variations in Earth’s gravity field, effectively weighing changes in water mass over large river basins and groundwater aquifers—those porous, subterranean rock and soil layers that store water that must be pumped to the surface.

As complex as that sounds, the results are actually quite simple to understand. The data quantified the rates at which all regions on Earth are gaining or losing water, allowing my colleagues and me to produce the accompanying map. And what the map shows is also simple to understand but deeply troubling: Water security—a phrase that simply means having access to sufficient quantities of safe water for our daily lives—is at a greater risk than most people realize.