Why the amount of water storage is declining in lakes around the world

The amount of water stored in half of the largest lakes and reservoirs around the world is declining due to human activity and climate change, according to new research.

While lake water storage can naturally fluctuate in response to local precipitation, direct human activities, such as damming and water consumption, are increasingly affecting precious water resources, according to a study published Thursday in the American Association for the Advancement of Science.

Researchers combined global satellite measurements with climate and hydrologic models to detect trends in lake water storage for nearly 2,000 of the world’s largest lakes and reservoirs from 1992 to 2020.

The findings revealed "widespread decline," according to the study. About 53% of the water bodies studied were found to have experienced significant water losses over the last 28 years at a rate of roughly 22 gigatonnes, or 1 billion metric tons, per year, according to the study.

The declining water storage could affect a quarter of the world's population, Fangfang Yao, a surface hydrologist who conducted the research with the University of Colorado Boulder, told ABC News.

"This trend is likely to continue if we do nothing about climate change or do not restrict human water consumption," Yao said.

Some of the lakes and reservoirs most affected are the Salton Sea in California, the Great Salt Lake in Utah and the Godzareh depression in Afghanistan, according to the study.

Losses are also "devastating" in the Aral Sea, a lake lying between Kazakhstan and Uzbekistan, which has been shrinking since 1960 and largely dried out more than a decade ago, Yao said.

What used to be a freshwater body is now a hypersaline lake that is no longer suitable for drinking. As a result, the ecology of the region has been affected, with many native species no longer able to survive the environment, Yao added.

While lakes only cover 3% of the global land area, they hold 87% of the planet's liquid surface fresh water, scientists say.

"Much" of the net volume loss in natural lakes is a result of climate warming, increased evapotranspiration and human water consumption, the authors said. Sedimentation was also to blame for storage loss in drying reservoirs.

It was previously well known that the amount of water stored in some of the world’s largest lakes and human-managed reservoirs has progressively declined over recent years, but the drivers behind these losses -- particularly those related to human impacts and climate change -- were poorly understood at the global scale, according to the authors.

The findings underscore the importance of future surface water resources management strategies as well as incorporating climate change and sedimentation impacts into sustainable water resources management, they said.