The amount of water is decreasing in more than 50% of the world’s lakes. Satellites reveal the scale of the phenomenon

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Lakes, also known as the “eyes of the Earth,” are one of the most beautiful natural phenomena on our globe. Their waters conceal extraordinary ecosystems, are habitats for many species of plants and animals, and provide a place where migratory birds find shelter and food. In addition, they are an important source of water for local communities, both for economic and recreational purposes. And although the number of lakes on the planet is an impressive 117 million, their total amount of water (surface area) is less than 4% of the Earth’s total area. Compared to the vast oceans, which are nearly 18 times larger, the lakes can seem almost imperceptible. Nevertheless, it was noted that more than half of them are alarmingly, steadily losing water.

Amount of water in lakes – latest study

According to a new landmark assessment released on May 18 this year. inScience, the amount of water is declining in more than half of the world’s largest lakes and reservoirs. This disturbing trend has continued for 30 years.

Scientists see the reasons for this phenomenon mainly in three factors. First – a warming climate. Second – the excessive consumption of resources by humans. Consumption by the ever-increasing population, industrial development or irrigation of agricultural fields consume huge amounts of water. These factors cause the water balance of the lakes to be disturbed and their water levels to steadily decline. And third – sedimentation. The accumulated sediment reduces the capacity of the lake, limiting its ability to hold water.

“Lakes around the world are under threat, and this has broad implications,” Balaji Rajagopalan, a professor at the University of Colorado Boulder and co-author of the study. – “They allow societies and humanity to live, yet they do not receive the respect they deserve.”

A total of 1972 lakes and reservoirs were surveyed by the researchers, focusing on those with an area of more than 100 square kilometers and reservoirs. The analyses used 250,000 images of lake areas taken by satellites between 1992 and 2020. The results were astonishing – as many as 53% of lakes around the world experienced a drop in water levels.

“In 30 years, the lakes have lost up to 25.26 gigatons of water per year, a striking number,” Jean-François Cretaux, an engineer at the National Space Research Center.

The research yielded yet another surprising discovery. It appears that not only in dry areas, but also in wet regions, lakes are experiencing water loss, in part due to increasing land evapotranspiration and potentially longer recovery times. These losses in the tropics and the Arctic indicate more widespread drying trends than previously thought.

However, not all lakes are drying up. In comparison with the shrinking resources of more than half of the world’s lakes, about 24% have seen a significant increase in water storage. The amount of water with an upward trend usually occurs in sparsely populated areas, such as the inner Tibetan Plateau or the Great Plains in North America. These areas are characterized by low human pressure and lower resource use, which promotes water accumulation. In addition, an increase in lake levels has been reported in areas with new reservoirs, such as in the Yangtze, Mekong and Nile basins, mainly due to increased rainfall and dam construction.

Environmental and social consequences

The shrinking of major lakes and reservoirs has serious consequences for both the environment and society. The decline in water resources leads to the degradation of aquatic ecosystems, so we are losing unique habitats for many plant and animal species. Insufficient water in reservoirs can also affect water quality by concentrating pollutants and deteriorating ecological status.

For the local population, falling water levels have serious economic and social consequences. Local residents draw water from the lakes for drinking, crop irrigation or as an energy source for power plants. If the amount of water continues to decline, it could lead to serious water supply problems for these communities.

An estimated 87% of the world’s lakes are freshwater, and as much as a quarter of the globe’s population, or approx. 2 billion people, live near drying lakes. In the face of these facts, it becomes urgent to consider the impact of human water use, climate change and sedimentation on the sustainable management of this precious resource. The new research provides data on water loss and its impact on residents of problematic regions, but also offers hope for new solutions to curb the trend.

“If human consumption is a significant factor in the decline of water storage in lakes, we can adapt new policies to limit large-scale declines.” – Ben Livneh, co-author of the study, CIRES member and professor of engineering at CU Boulder.

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