Half of the largest lakes around the world are losing water to climate change and human uses, but tracking the reasons for the changes in their water volumes can lead to better management strategies, scientists say.
A team of researchers from the United States, France and Saudi Arabia has created a technique to measure fluctuations in the water levels of nearly 2,000 of the world’s biggest lakes and reservoirs, which account for 95% of the planet’s total lake water storage.
The team used computer models to interpret three decades’ worth of observations from satellites to quantify and attribute trends in lake storage around the planet. Their data comprised 250,000 lake-area snapshots captured between 1992 and 2020 from the areas of 1,972 of the planet’s biggest lakes.
“Globally, freshwater lakes and reservoirs store 87% of the planet’s water, making them a valuable resource for both human and Earth ecosystems. Unlike rivers, lakes are not well monitored, yet they provide water for a large part of humanity, even more than rivers,” the scientists explain.
However, some of the Earth’s largest water bodies, such as the Aral Sea between Kazakhstan and Uzbekistan, have seen their water levels reduced drastically as a result of unsustainable water management practices.
The researchers wanted to find out how other water bodies have been faring and have published their findings in a study, in which they report that 53% of lakes have experienced a decline in water storage over the past decades.
“We have pretty good information on iconic lakes like the Caspian Sea, Aral Sea and Salton Sea, but if you want to say something on a global scale, you need reliable estimates of lake levels and volume,” says Balaji Rajagopalan, a professor of engineering at the University of Colorado Boulder. “With this novel method we are able to provide insights into global lake level changes with a broader perspective.”
Climate change and human water consumption have been the main culprits for a net decline globally in natural lake volumes in about 100 large lakes, according to Fangfang Yao, a climate fellow at the University of Virginia.
“Many of the human and climate change footprints on lake water losses were previously unknown, such as the desiccations of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina,” Yao adds.
Importantly, lakes in both dry and wet areas are losing volume with losses in humid tropical lakes and Arctic lakes indicating more widespread drying trends than previously thought. As for large reservoirs, nearly two-thirds of the Earth’s large reservoirs have experienced significant water losses.
The findings have grave implications as a quarter of the world’s population reside in the basins of drying lakes, “indicating an urgent need to incorporate human consumption, climate change, and sedimentation impacts into sustainable water resources management,” the scientists say.
At the same time, a quarter of lakes have seen significant increases in water storage, particularly in underpopulated areas such as the inner Tibetan Plateau and Northern Great Plains of North America as well as in areas with new reservoirs such as the Yangtze, Mekong, and Nile river basins.
“If human consumption is a large factor in lake water storage decline, then we can adapt and explore new policies to reduce large-scale declines,” stresses Ben Livneh, an associate professor of engineering at CU Boulder.
