Climate change it’s hotter temperatures and societal water diversion has reduced the world’s lakes by trillions of gallons of water a year since the early 1990s, a new study finds.
A close examination of nearly 2,000 of the world’s largest lakes found that they lose about 5.7 trillion gallons (21.5 trillion liters) each year. That means from 1992 to 2020, the world lost the equivalent of 17 Lake Meads, America’s largest reservoir, in Nevada. This is roughly equivalent to the amount of water used in the United States in the entire year of 2015.
Even lakes in areas with high rainfall are drying up. That’s because of the same thirsty atmosphere from warmer air absorbs more water in evaporationand a thirsty society diverting water from lakes to agriculture, power plants and drinking supplies, according to a study Thursday journal Science.
The authors also cite a third factor that they call more natural, that water is decreasing due to rainfall patterns and changes in river flow, but that also plays a role in climate change. That’s the main reason Iran’s Lake Urmia loses about 277 billion gallons (1.05 trillion liters) a year, the study said.
Shrinking lakes don’t mean places will suddenly go without drinking water, but it could lead to more competition for lake water, which is also used for hydroelectric power and recreation like boating, the authors said. in the study said.
“More than half of the decline is primarily due to human consumption or indirect human signals through climate warming,” said study lead author Fangfang Yao, a climate scientist at the University of Colorado. .
The transfer of water from lakes – a direct cause of human decline – is likely to be greater and more noticeable because it is “very acute, very local and it has the ability to change the landscape,” said the co-author Ben Livneh, a University of Colorado hydrologist.
But the indirect human decline, from warmer air due to climate change, “is this a global blanket effect affecting all or many areas,” Livneh said. in California Mono Lake is a lake is a good example of this type of reduction, Yao said.
Even areas that have become wetter due to climate change are losing lake water as warm air absorbs more moisture from the lakes. And that means more water in the air, which may fall as rain or snow but “may fall as rain far away, outside the basin where it evaporates or even into the ocean,” Livneh said in an email.
Yao, Livneh and colleagues used nearly 30 years of satellite observations, climate data and computer simulations to determine what is happening to the lakes and found that more than half of them have shrunk significantly. statistically and not randomly.
In the United States, Lake Mead lost two-thirds of its water between 1992 and 2020, while the Great Salt Lake also noticed a decrease, Yao said. The Great Lakes declined sharply from 1992 to 2013 then plateaued and then increased.
Another problem is that the lakes are filled with sediment or sewage from the upper river.
Scientists have known for a long time about the problems of climate change, migration and sedimentation, “although the complete calculation of the differences in water storage for large lakes is provided by Yao and colleagues are new” and it creates “a more complete picture” than previous research, said University of North Carolina hydrology professor Tamlin Pavelsky, who was not part of the study.
“I’m generally most concerned about ecologically important lakes and in populated areas that don’t have many other good sources of water,” Pavelsky said in an email. “Lake Urmia in Iran, the Dead seathe Salton Sea … all of this is worrying.”
This is likely to worsen as society searches for more water and more reservoirs with a growing population and a warmer Earth, said UCLA climate hydrologist Park Williams, who was not part of the study.
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