Water is being depleted at sites around the world
Intensive groundwater pumping, evaporation and melting due to rising global temperatures have shifted a growing amount of freshwater from the continents to the oceans. This threatens water availability for most of the world’s population and adds to sea level rise.
Jay Famiglietti at Arizona State University and his colleagues used gravity measurements from satellites to estimate changes in the total amount of water mass stored on the continents. That includes all forms of freshwater, from rivers and underground aquifers to glaciers and ice sheets.
These measurements show there have been alarming declines in freshwater in many parts of the world between 2002 and 2024. The researchers found dry regions aren’t just getting drier – a trend expected with climate change – they are also expanding by more than 800,000 square kilometres per year, an area about the size of the UK and France combined.
The team identified four “mega-drying” regions where separate areas of freshwater loss have now connected to create a swathe of drying. Those include northern Canada and Russia, where loss is driven by melting glaciers, permafrost and reduced snow.
In the other two regions, water loss is dominated by groundwater depletion, mainly from pumping for irrigation. Those are the US Southwest, much of Central America and a region stretching from western Europe and North Africa to northern India and China. They found groundwater depletion, which can be exacerbated by heat and drought prompting people to pump more, makes up 68 per cent of the decline in overall water storage.
This transfer of mass is so large it has become a major contributor to sea level rise. They found since 2015, water loss from the continents has caused more sea level rise than meltwater from the Antarctic or Greenland ice sheets, raising the oceans by just under a millimetre per year.
These trends together “send perhaps the direst message on the impact of climate change to date”, the researchers write in their report. “The continents are drying, freshwater availability is shrinking, and sea level rise is accelerating.”
We already knew about these drying trends in many individual regions, says Manoochehr Shirzaei at the Virginia Polytechnic Institute and State University. But he says the power of this research comes from its global view of the problem. “We are not producing water or destroying water. We are just redistributing water. But redistribution is not going in the right direction,” he says.
“The next step is really to do the detailed diagnosis to actually separate out what’s driving the groundwater depletion,” says Benjamin Cook at Columbia University in New York. “It would take a little more detail to separate the climate change story from the groundwater depletion story.”
Topics:
