Many of world's biggest lakes in peril due to warming, drying climate

Water storage in many of the world's biggest lakes has declined sharply in the last 30 years, according to a new study, with a cumulative drop of about 21.5 gigatons per year, an amount equal to the annual water consumption of the United States.

The loss of water in natural lakes can "largely be attributed to climate warming," a team of scientists said as they published research today in Science that analyzed satellite data from 1,980 lakes and reservoirs between 1992 and 2020. When they combined the satellite images with climate data and hydrological models, they found "significant storage declines" in more than half of the bodies of water.

The combination of information from different sources also enabled the scientists to determine if the declines are related to climate factors, like increased evaporation and reduced river flows, or other impacts, including water diversions for agriculture or cities. A quarter of the world's population lives in basins where lakes are drying up, they warned.

Vanishing lakes have already caused starvation and dislocation and increased the potential for international conflict, including in Africa, where Lake Chad is drying up, as well as in South America, where Bolivia's Rhode Island-sized Lake Poopo, once the nation's second largest body of water, disappeared over the last few decades.

The study identifies the Southwestern US as a troubled area, confirming the challenges spurred by dwindling water supplies in the nation's two largest reservoirs, Lake Powell and Lake Meade on the Colorado River.

The new study showed lake water storage loss prevailed across major global regions including much of interior Asia and the Middle East, northeastern Europe, as well as Oceania, North and South America, and southern Africa. A total of 457 natural lakes had significant water losses of about 38 gigatons per year, while 234 lakes showed water storage gains and 360--about a third of the studied lakes--showed no significant change.

Only about one-third of the total decline of water storage in drying lakes is offset by increases in other lakes, and the water bodies with rising levels are mainly in remote and sparsely populated regions like the Inner Tibetan Plateau, the Northern Great Plains in the US, and the Great Rift Valley in Africa. These storage increases were driven mainly by changes in precipitation and runoff, the study concluded.

Uncertainty about the Great Lakes

The research did not find a climate warming fingerprint affecting the Great Lakes, but that doesn't mean it's not there. During the 1992-2020 study period, water levels in the Great Lakes dropped steeply and then increased sharply again due to big swings in rainfall. The researchers' analysis didn't show a global warming signal, said lead author Fangfang Yao, who studies surface water changes at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder.

"Lake Michigan-Huron shows no trend during our study period. Lakes Superior and Erie both of them show an overall increasing trend, suggesting the greater role of natural climate variability," Yao said.