'Changing landscape': More than half of world's lakes have shrunk since early 1990s, study finds

More than half of the world's lakes have shrunk and are continuing to lose trillions of gallons of water every year since the early 1990s, a new study has revealed.

A close examination of nearly 2,000 of the world's largest lakes found they are losing about 5.7 trillion gallons (21.5 trillion litres) a year.

Between 1992 to 2020, the world lost the equivalent of 17 Lake Meads, America's largest reservoir, in Nevada - or roughly equal to how much water the United States used in an entire year in 2015.

Hotter temperatures, brought about by climate change, and which are causing greater amounts of water to be evaporated into the air were cited as one of the main causes for the findings, the report's authors said.

Meanwhile, increased levels of water consumption by humans for agriculture, power plants and drinking supplies was blamed for the trend.

The study also said changes to rainfall pattern and river runoff provided a third, more natural, reason for its findings. But it added that may have a climate change component.

A decline in the number of global lakes does not mean humans are at imminent risk of going without drinking water, but it may lead to more competition for lake water - which is used in hydroelectric power and for recreational purposes.

The study's lead author, Fangfang Yao, a climate scientist at the University of Colorado, said: "More than half of the decline is primarily attributable to human consumption or indirect human signals through climate warming."

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In addition, the diversion of water from lakes - a direct human cause of shrinkage - is probably larger and more noticeable because it is "very acute, very local and it has the capability of really changing the landscape", said co-author Ben Livneh, a University of Colorado hydrologist.

But he added that the indirect human shrinking, from warmer air due to climate change, "is this global blanketing effect that kind of affects everything or more places".

Areas which are becoming wetter because of climate change are also losing lake water because hotter air is sucking more moisture out of the lakes.

As a result, you end up with more water in the air, which can fall as rain or snow, but "may end up falling as rain far away, outside the basin where it evaporated or even over the ocean", Mr Livneh said.

The study was created using almost 30 years of satellite observation, climate data and computer simulation to determine what is happening to lakes.

More than half of the lakes observed were found to have shrunk so much that it is statistically significant and not random.

Scientists have long known about the problems of climate change, diversion and sedimentation, "however the complete quantification of water storage variations for large lakes that Yao and colleagues provide is new", said University of North Carolina hydrology professor Tamlin Pavelsky - who was not part of the study.

"I'm generally most worried about lakes that are ecologically important and in populated areas without a lot of other good sources of water," he said.

"Lake Urmia in Iran, the Dead Sea, the Salton Sea... these are all worrisome."

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