Lakes store 87% of the planet’s fresh water, making them a valuable resource for human and terrestrial ecosystems. Unlike rivers, lakes are not well monitored, but they provide water to a greater proportion of humanity than rivers.

However, more than 50 percent of the world’s major lakes and aquifers are losing water to human consumption and global warming, according to a new study published in the journal Nature.Science(Science) on 18 May.

The authors devised a technique to measure changes in water levels in nearly 2,000 of the world’s largest lakes and reservoirs, which account for 95 percent of all lake water storage on Earth.

Innovative technology combines 3 decades of satellite observations with models to track and interpret changes in lake storage globally.

The first assessment of its kind

The study was motivated by researchers’ observations of environmental crises in the planet’s largest bodies of water, such as the drying up of the Aral Sea between Kazakhstan and Uzbekistan.

As such, the team believes this assessment is the first to provide a comprehensive assessment of trends and drivers of global change in lake water storage based on a combination of satellites and models.

Study co-author Balaji Rajagopalan – a professor of hydrology and civil engineering at the University of Colorado, Boulder – explained in a statement to Al Jazeera Net that until the study was conducted, the research community did not have a clear understanding. Long-term trends and changes in water levels, but now, according to the team’s results, “we can now provide insights into global changes in lake level from a broader perspective using these results and the methodology based on them. On,” he says.

To explain these trends in natural lakes, the team drew on recent advances in water use and climate modeling. They concluded that both climate change and human water consumption are primarily responsible for the global decline in the size of natural lakes, as well as the loss of water from about 100 Great Lakes.

For these results presented in the research, Rajagopalan pointed out, the team used nearly a quarter of a million snapshots of lake areas captured by satellites from 1992 to 2020 to study 1972 areas of the largest lakes on Earth. Therefore, the team combined recent water level measurements with long-term areal measurements to reconstruct lake levels from decades ago.

Dangerous results

“Indeed, the findings of our study are alarming,” says the study co-author. “About 53% of the world’s lakes have lost water storage. This loss is 17 times the size of Lake Mead, the largest reservoir in the United States.”

The researchers note that lakes in both arid and wet regions worldwide are losing volume, and this loss in humid tropical and arctic lakes points to a broader drying trend than previously recognized.

In addition to studying natural lakes, the team also examined trends in water storage in reservoirs, and found that two-thirds of Earth’s largest reservoirs have experienced significant water loss, according to the report. For press release Published on EurekAlert.

According to the study, the process of sedimentation is one of the reasons for the decline in global storage in current reservoirs, as the lake bottom rises due to the accumulation of silty or sandy sediments. For reservoirs created before 1992, silting was more effective than drying.

However, not all lakes are shrinking, as the study shows that 24% of global lakes experienced significant increases in water storage.

These lakes are mainly located in sparsely populated areas such as the Inner Tibetan Plateau and the northern Great Plains of North America, as well as in areas with fresh water reservoirs such as the Yangtze, Mekong and Nile river basins.

The study authors estimate that nearly two billion people, or a quarter of the world’s population, live in the basins of these lakes, which are threatened or already drying up.

This statistic underscores the urgent need to consider the effects of human consumption, climate change and sedimentation in water management strategies.