Half of world’s largest lakes losing water

Fifty-three per cent of the world’s largest freshwater lakes are in decline, storing less water than they did three decades ago, according to a new study. The study analyzed satellite observations dating back decades to measure changes in water levels in nearly 2,000 of the world’s biggest lakes and reservoirs. It found that climate change, human consumption and sedimentation are responsible.

More than 50 per cent of the largest lakes in the world are losing water, according to a groundbreaking new assessment published today in Science. The key culprits are not surprising: warming climate and unsustainable human consumption.

But lead author Fangfang Yao, a CIRES visiting fellow, now a climate fellow at University of Virginia, said the news is not entirely bleak. With this 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.

“This is the first comprehensive assessment of trends and drivers of global lake water storage variability based on an array of satellites and models,” Yao said.

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.

So 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.

But despite their value, long-term trends and changes to water levels have been largely unknown -- until now.

“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 CIRES fellow, 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.”

Science Daily