Higher temperatures from climate change and societal water diversion have reduced the world’s lakes by billions of gallons of water a year since the early 1990s, a new study has found.
Close examination of nearly 2,000 of the world’s largest lakes has revealed that they are losing around 5.7 trillion gallons (21.5 trillion liters) per year. This means that from 1992 to 2020, the world lost the equivalent of 17 Lake Meads, America’s largest reservoir, in Nevada. It’s also roughly equal to the amount of water used by the United States in an entire year in 2015.
Even lakes in areas that receive more precipitation are shrinking. This is because of both a thirstier atmosphere, warmer air sucking in more water through evaporation, and a thirstier society diverting water from lakes to agriculture, power plants and drinking water supply, according to a study published Thursday in the journal Science.
The authors also cited a third reason which they described as more natural, decreasing water due to rainfall patterns and changes in river runoff, but even this may have a climate change component. It is the main cause of the loss of about 277 billion gallons (1.05 trillion liters) per year in Iran’s Lake Urmia, according to the study.
The decline of lakes does not mean that places will suddenly run out of drinking water, but it may lead to greater competition for lake water, which is also used in hydroelectric power and recreation such as boating. yachting, the study authors said.
“More than half of the decline is primarily attributable to human consumption or indirect human signals via global warming,” said study lead author Fangfang Yao, a climatologist at the University of Colorado.
The diversion of water from lakes — a direct human cause of shrinkage — is likely larger and more visible because it’s “very acute, very local, and it has the ability to really change the landscape,” the co-author said. Ben Livneh, an academic hydrologist from Colorado.
But indirect human shrinkage, due to warmer air from climate change, “is this global blanket effect that kind of affects all or more places,” Livneh said. Mono Lake in California is a good example of this type of shrinkage, Yao said.
Even areas that are getting wetter due to climate change are losing water from the lakes because warmer air sucks more moisture from the lakes. And that means more water in the air, which may fall as rain or snow but “may end up falling as rain far away, outside the basin where it evaporated or even above the ocean,” Livneh said in an email.
Yao, Livneh and their colleagues used nearly 30 years of satellite observation, climate data and computer simulation to understand what is happening to lakes and found that more than half of them have shrunk so much that it’s was statistically significant and not random.
In the United States, Lake Mead lost two-thirds of its water between 1992 and 2020, while the Great Salt Lake also shrank noticeably, Yao said. The Great Lakes fell dramatically from 1992 to 2013, then plateaued and then rose.
Another problem is that the lakes fill with sediment or dirt from the rivers upstream.
Scientists have long been familiar with the problems of climate change, diversion and sedimentation, “however the comprehensive quantification of water storage variations for large lakes that Yao and his colleagues provide is novel” and it creates “a much more comprehensive” than previous research, said Tamlin Pavelsky, a professor of hydrology at the University of North Carolina, who was not part of the study.
“I’m generally more concerned about lakes that are ecologically important and in populated areas without many other good water sources,” Pavelsky said in an email. “Lake Urmia in Iran, the Dead Sea, the Salton Sea… all of these are disturbing.”
It is likely to get worse as society seeks 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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