World’s Largest Lakes Losing Trillions of Gallons of Water Annually

More than half of the large lakes and reservoirs on the planet have diminished since the early 1990s due to climate change and human diversion and consumption, an international team of researchers has found. The findings have implications for people who rely on their supply of freshwater for drinking, hydropower and agriculture.

The researchers looked at almost 2,000 of the largest lakes and found they are losing about 5.7 trillion gallons per year. That’s about the same amount as the entire U.S. used in 2015, or 17 times the volume of the biggest reservoir in the U.S., Nevada’s Lake Mead, between 1992 and 2020, the study said.

“More than half of the decline is primarily attributable to human consumption or indirect human signals through climate warming,” said lead author of the study Fangfang Yao, a University of Colorado Boulder climate scientist, as The Associated Press reported.

According to the study, more water is evaporating due to warmer air associated with global heating, and people are diverting an enormous amount of water, so even lakes in areas with more rainfall continue to shrink.

This includes some of the most important sources of freshwater on Earth, including South America’s Lake Titicaca and the Caspian Sea, reported Reuters.

The study, “Satellites reveal widespread decline in global lake water storage,” was published in the journal Science.

Evaporation leads to more water in the atmosphere that can become rain or snow, but “may end up falling as rain far away, outside the basin where it evaporated or even over the ocean,” said Ben Livneh, a University of Colorado hydrologist and co-author of the study, as The Associated Press reported.

Yao said human consumption and climate warming were responsible for 56 percent of the water decline, but that warming made up “the larger share of that,” reported Reuters.

The research team used satellite images along with hydrological and climate models to assess the lakes. They found that 53 percent of them had shrunk between 1992 and 2020 due to rising temperatures, excessive human use, rainfall and runoff changes and sedimentation.

“This global-scale attribution of [lake water shortage] trends has important implications for water resources management, particularly given that up to 2.0 billion people (one-quarter of the global population in 2023) reside in basins with large water bodies experiencing significant water storage losses,” the authors wrote in the study.

The study found that lakes like the Dead Sea in the Middle East and Central Asia’s Aral Sea were shrinking due to unsustainable use by humans, while rising temperatures were affecting lakes in Mongolia, Egypt and Afghanistan.

Between 1992 and 2020, the Great Salt Lake dried up markedly and Lake Mead lost two-thirds of its water volume. From 1992 to 2013, the Great Lakes shrunk noticeably before leveling off and increasing.

About one-fourth of the lakes in areas like the Inner Tibetan Plateau saw increased water levels, frequently because of dam construction.

“I’m generally most worried about lakes that are ecologically important and in populated areas without a lot of other good sources of water,” said Tamlin Pavelsky, a University of North Carolina hydrology professor who was not part of the study, as The Associated Press reported. “Lake Urmia in Iran, the Dead Sea, the Salton Sea… these are all worrisome.”