The Earth’s largest aquifers, a source of water for more than 60 million people, are depleting fast, likely due to a growing world population and industries such as agriculture, according to a new study.

Scientists at the University of California, Irvine led the research that used NASA’s GRACE satellite to find out just how much groundwater we’re losing and how quickly. The detailed images show that 21 of the world’s 37 largest aquifers are “past sustainability tipping points,” meaning that those aquifers have lost more water than they gained over the last 10 years.

Researchers learned that about one-third of the aquifers were “stressed,” and that eight that were examined were considered “overstressed” or “highly stressed.” That means that although humans are still removing water from those underground sources, there is no water to help replenish what’s been lost.

The study looked at aquifers all over the world and found that the two most stressed sources of groundwater included the Arabian Aquifer System in the Middle East as well as the Indus Basin in south Asia.

In the United States, California’s Central Valley Aquifer was the most depleted from overuse. The study notes that the West Coast aquifer “is dominated by populated irrigated cropland,” a major source of water consumption.

Fisherman in California's Lake Success, which has low water levels

It may be called Lake Success, but drought is clearly taking a toll on the water levels on this lake in East Porterville, California. (Image: David McNew/Getty Images)

“The water table is dropping all over the world,” said Jay Famiglietti, senior water scientist at NASA’s Jet Propulsion Laboratory in California, after calling the situation “critical" in an interview with The Washington Post.  “There’s not an infinite supply of water.”

As it stands now, already 783 million people don’t have access to clean water. According to the United Nations, the need for more clean water is only going to intensify. “Water availability is expected to decrease in many regions. Yet future global agricultural water consumption alone is estimated to increase by ~19% by 2050, and will be even greater in the absence of any technological progress or policy intervention.”

NASA’s satellite didn’t just reveal the status of underground water. It showed all of the Earth’s water. Famiglietti told the New York Times back in 2011 during the later stages of data collection that GRACE, NASA’s Gravity Recovery and Climate Experiment, captures data showing “all of the change in ice, all of the change in snow and water storage, all of the surface water, all of the soil moisture, all of the groundwater.”

Clean water is one of the most basic requirements for life on earth, a fact that prompted the United Nations to recognize clean drinking water and sanitation as a universal human right. These underground water sources make up 35 percent of the water used by humans.

“Look, water has been a resource that has been plentiful,” said Famiglietti in 2011. “But now we’ve got climate change, we’ve got population growth, we’ve got widespread groundwater contamination, we’ve got satellites showing us we are depleting some of this stuff. I think we’ve taken it for granted, and we are probably not able to do that anymore.”

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We're running out of water, NASA images show
More than half of the world's largest aquifers are being depleted, according to satellite system data.