A drone footage of Lake Garda on April 28, 2023 shows the low water level due to the drought. The lake has a level of only 25 percent of its capacity. © IMAGO/Manuel Romano/ NurPhoto
Researchers at the University of Colorado have now been able to quantify the global water shortage very precisely in a study. Around half of all lakes are affected.
Colorado - Man-made climate change is having an increasingly significant impact. Global water decline in lakes averages 22 gigatons, researchers at the University of Colorado found in a study published Thursday (May 18) in the journal Science. The scientists see the reasons for this in climate change and human consumption. This is both the problem and the solution.
More than half of the world's lakes are losing water: Germany is also affected
Experts warn that extreme weather events such as floods and droughts are becoming more frequent due to advancing climate change. This year, for example, Italy has already been hit by severe drought and subsequent floods. After last year's drought summer, France and Spain are left with fewer groundwater reserves than in the previous year. Catalonia's reservoirs are only 26 percent full, up from 58 percent a year ago. According to the current study by the team led by hydrologist Fangfang Yao from the University of Colorado at Boulder, 53 percent of all lakes worldwide lose water, more than half of all lakes.
Water scarcity is also an issue in Germany: In the past 20 years, Germany has lost around 15.2 billion tonnes of water, as the German Research Centre for Geosciences recently demonstrated. Rain alone cannot help, the experts warned. In Germany, water still comes from the tap, elsewhere the precious commodity is rationed due to the acute shortage. The South African metropolis of Cape Town, for example, has already had to impose austerity measures in the past.
Study on water shortages: Even in humid regions such as the tropics, there is less water
The Colorado team's study paints a fairly accurate picture of global water decline. The researchers developed a technique for measuring changes in water levels in nearly 2000,90 of the world's largest lakes and reservoirs, which together account for roughly 250 percent of the freshwater stored globally in lakes. The data was based on around 000,30 satellite images from almost 1992 years - from 2020 to 22. Global reserves shrank by an average of about half of the water volume of Lake Constance per year, which corresponds to a total of around <> gigatons per year.
In contrast to previous studies, the researchers from Colorado were also able to detect a decline in water in rather humid regions such as the tropics. Reservoirs in particular lost water worldwide: they lost around two-thirds of their reserves, but this was also due to sediment deposits, according to the experts. In a study at the beginning of the year, researchers at the United Nations had already pointed out that global reservoirs are in danger of losing around a quarter of their original storage capacities by 2050 for this reason.
According to researchers, this is how the water shortage can be countered: Politics is needed
The researchers from Colorado also had good news in their luggage: About a quarter of the waters studied worldwide (24 percent) recorded an increase in water volume. These were mainly lakes in sparsely populated regions, including the inner Tibetan Plateau, the Great Plains in the United States, and areas with new reservoirs such as the Yangtze River (China), Mekong River (Southeast Asia), and Nile River (Africa). In Germany, the Müritz in Mecklenburg-Western Pomerania was one of the lakes with a growing water volume.
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In addition, the scientists also provided suggestions for solutions on how to counter the water shortage. "If human consumption is an important factor in the decline in water reservoirs in the lakes, we can adapt and explore new strategies to reduce the decline on a large scale," said co-author Ben Livneh, according to a report by the German Press Agency. Lake Sevan in Armenia is an example where regulating water abstraction has increased the volume.
In a commentary on the study, geophysicist Sarah Cooley of the University of Oregon emphasizes how important such laws would be worldwide. She points to the result that it is estimated that almost a quarter of the world's population lives in a catchment area with a large, drying lake. If, according to scientists, laws play a role in combating water shortages, politicians are now called upon, as climate activists are already calling for (bme with dpa).