Years of documentation and research have shown that many of the world’s underground aquifers — the leading source of fresh water for hundreds of millions of people — have been depleted, in some instances well below naturally recoverable rates. Now, recent data from a NASA satellite show the full extent of this problem on a global scale, offering the first detailed assessment of its kind. As the following chart from the Washington Post vividly shows, the outlook is dire.
From the United States to China, 21 of the world’s 37 largest aquifers — the source of 35 percent of the water used by humans worldwide — are depleted passed their “sustainability tipping points”, meaning more water was taken than replaced during the decade in which the study was conducted. Of these, 13 declined to the point of being categorized as “most troubled”. This will only worsen as water usage rates continue to increase across the world, driven by the demands of agriculture, human thirst, and industry (namely mining).
The impact of climate change will no doubt only worsen the problem, as it has in California and most other severely drought-stricken regions. At least the U.S. and the developed world has the capital and technology (if not the political will) to adapt to or address the problem accordingly; much of the world will not be so lucky, and cruelly it is among already deeply impoverished and troubled places where water shortages are most severe.
And while NASA satellites could not measure the total capacity of the aquifers — meaning some of these water supplies could be larger than we can detect — the opposite may very well be true; the uncertainty should make us even more cautious about how we manage our finite water supply, especially as aquifers can take thousands of years to fill up.
A detailed assessment from the article.
The health of the world’s aquifers varied widely, mostly dependent on how they were used. In Australia, for example, the Canning Basin in the country’s western end had the third-highest rate of depletion in the world. But the Great Artesian Basin to the east was among the healthiest.
The difference, the studies found, is likely attributable to heavy gold and iron ore mining and oil and gas exploration near the Canning Basin. Those are water-intensive activities.
The world’s most stressed aquifer — defined as suffering rapid depletion with little or no sign of recharging — was the Arabian Aquifer, a water source used by more than 60 million people. That was followed by the Indus Basin in India and Pakistan, then the Murzuk-Djado Basin in Libya and Niger.
California’s Central Valley Aquifer was the most troubled in the United States. It is being drained to irrigate farm fields, where drought has led to an explosion in the number of water wells being drilled. California only last year passed its first extensive groundwater regulations. But the new law could take two decades to take full effect.
Also running a negative balance was the Atlantic and Gulf Coastal Plains Aquifer, which stretches across the southeast coast and Florida. But three other aquifers in the middle of the country appeared to be in relatively good shape.
Some groundwater filters back down to aquifers, such as with field irrigation. But most of it is lost to evaporation or ends up being deposited in oceans, making it harder to use. A 2012 study by Japanese researchers attributed up to 40 percent of the observed sea-level rise in recent decades to groundwater that had been pumped out, used by humans and ended up in the ocean.
Famiglietti said problems with groundwater are exacerbated by global warming, which has caused the regions closest to the equator to get drier and more extreme latitudes to experience wetter and heavier rains. A self-reinforcing cycle begins. People living in mid-range latitudes not only pump more water from aquifers to contend with drier conditions, but that water — once removed from the ground — also then evaporates and gets recirculated to areas far north and south.
In other words, humanity will need to a comprehensive, internationally-coordinated approach to safeguarding the global water supply. While desalinization is touted as a solution, it is thus far prohibitively expensive and energy intensive, and in any case it will not resolve the environmental catastrophe portended by a depletion of freshwater. Like so many other problems threatening human survival into the 21st century, this one will require humans to harness considerable scientific, technological, economic, and international resources. But water is the ultimate global commons for that reason.