2 billion people at risk as half of world’s largest lakes drying up

New Delhi: More than 50 per cent of the largest lakes in the world are losing water, and the key culprits are not surprising: warming climate and unsustainable human consumption, a new study, including a researcher of Indian-origin, has stressed.

According to a groundbreaking new assessment published in the journal Science, with a new method of tracking lake water storage trends and the reasons behind them, scientists can give water managers and communities insight into how to better protect critical sources of water and important regional ecosystems.

The authors estimate roughly one-quarter of the world's population, two billion people, resides in the basin of a drying lake, indicating an urgent need to incorporate human consumption, climate change and sedimentation impacts into sustainable water resources management.

"This is the first comprehensive assessment of trends and drivers of global lake water storage variability based on an array of satellites and models," said lead author Fangfang Yao, a climate fellow at University of Virginia in the US.

He was motivated to do the research by the environmental crises in some of Earth's largest water bodies, such as the drying of the Aral Sea between Kazakhstan and Uzbekistan. He and colleagues from the University of Colorado Boulder, Kansas State University, France, and Saudi Arabia created a technique to measure changes in water levels in nearly 2,000 of the world's biggest lakes and reservoirs, which represent 95 per cent of the total lake water storage on Earth.

The team combined three decades of observations from an array of satellites with models to quantify and attribute trends in lake storage globally.

Globally, freshwater lakes and reservoirs store 87 per cent 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.

"We have pretty good information on iconic lakes like 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," said Balaji Rajagopalan, a professor of engineering at CU Boulder and co-author.

"With this novel method...we are able to provide insights into global lake level changes with a broader perspective."

For the new paper, the team used 250,000 lake-area snapshots captured by satellites between 1992-2020 to survey the area of 1,972 of Earth's biggest lakes. The results were staggering: 53 per cent of lakes globally experienced a decline in water storage. "Lakes in both dry and wet areas of the world are losing volume. The losses in humid tropical lakes and Arctic lakes indicate more widespread drying trends than previously understood," the findings showed.