The measurements we do have come courtesy of data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites.
How can satellites measure the water levels under the Earth’s surface? NASA’s pair of GRACE satellites measures tiny fluctuations in Earth’s gravity. These miniscule changes are caused by the mass of water.
The first study highlighted 13 of the planet’s 37 largest aquifers. Between 2003 and 2013, these 13 were losing more water than they could recoup.
The cause is obvious. Human consumption. Eight of the 13 are classified as “overstressed.” Meaning, there was little to no water flowing back into them despite heavy consumption.
These ‘overstressed’ aquifers are in the usual spots. Arid areas where people living there depend solely on underground water.
Typically, oil is known as the resource that causes the most political tension. Soon, that could switch to water.
“What happens when a highly stressed aquifer is located in a region with socioeconomic or political tensions that can’t supplement declining water supplies fast enough?” asked Alexandra Richey, the lead author on both studies. “We’re trying to raise red flags now to pinpoint where active management today could protect future lives and livelihoods.”
The most overstressed aquifer in the world lies in the heart of one of the driest places on Earth. The Arabian Aquifer System supplies water to more than 60 million people.
The second most overstressed aquifer is the Indus Basin aquifer located in India and Pakistan. The Murzuk-Djado Basin in northern Africa came in third.
What about California? The state is experiencing an unprecedented drought right now, but is faring a bit better than the three worst. Researchers labeled California’s Central Valley as highly stressed along with four others.
Researchers have no idea how much water sits in these aquifers
A second paper was published this week. In it, scientists say data on the world’s usable groundwater is nearly non-existent. When scientists took data from the GRACE satellites and compared it with previous data on groundwater availability, they found huge swings in the time it would take for the aquifers to be depleted.
Take the overstressed Northwest Sahara Aquifer System. Time to depletion estimates range from 10 years to 21,000 years. We are either screwed or perfectly fine.
Determining how much water is in the world’s aquifer systems needs to be our top priority. Even understanding how much water sits below Earth raises its own set of challenges. Depending on how deep the water is, accessing could be difficult.
One simple solution is to take water from areas that already have plenty. Take the recent floods in Texas and the Midwest. Rivers swelled to record levels. We like building oil pipelines; how about one for water. Instead of letting all of this floodwater flow straight to the Gulf of Mexico, why not pipe some of it to areas that need it?
Or, put more effort into desalination plants. We have taken easy water availability for granted. California is learning this the hard way.