More than half of the world lives near freshwater sources while alarming declines in lake volumes threaten long term water security. Climate change compounds a trend already set in motion by rising demand and heavy use of water resources. Large lake systems on which billions depend are shrinking, reducing the reliability of this essential resource for the future.
A consortium of scientists published the findings in the journal Science after building a long term record from satellite data. Over the last three decades they reconstructed the volumes of the planet’s major lakes using extensive historic observations and modern imaging. The study marks a first comprehensive assessment of global trends and drivers behind lake water changes, according to lead author Fangfang Yao from the University of Colorado Boulder’s Environmental Sciences Research Institute.
To perform this analysis, researchers from Colorado and Kansas in the United States joined colleagues from France and Saudi Arabia. They developed a new method that tracks shifts in water levels across nearly two thousand large lakes and reservoirs, an amount that represents roughly 92 percent of all stored freshwater on Earth.
Lake Poopó in Bolivia is cited as an example of disappearing water, illustrating the real world impact of these trends.
Within the study there are twelve Spanish reservoirs named Iznajar, Puente Nuevo in Andalusia, Serena, Cíjara, Valdecanas, Alcántara in Extremadura, Almendra, Ricobayo in Castile and Leon, Yesa in Navarre, Buendía, Alarcón in Cuenca and Mequinenza in Aragon. Of the Spanish reservoirs inspected, eight show diminished volumes, three show no clear directional trend, and only Alarcón is increasing.
Using data gathered from 1992 to 2020, the researchers built a model that tracks water storage patterns for these lakes. They were able to recover satellite imagery for nearly two thousand of the largest lakes and reservoirs on the planet. In addition, nine satellite altimeters supplied water level data which the team cross checked with historical flow records to reduce uncertainty. For lakes lacking historical records, more recent measurements from other methods filled the gaps.
The resulting conclusion indicates that 53 percent of the world’s lakes have shown a net decrease in water flow, a loss comparable to the total runoff of Lake Mead, the United States’ largest reservoir. The decline is observed in both arid and humid regions, suggesting that drought is a broader and more persistent problem than previously understood.
Another finding shows that water losses are not limited to the largest lakes. At least two thirds of the major lakes studied have lost a significant amount of water.
Only Lakes in Remote, Unpopulated Areas Show Gains
While many lakes appear to be drying, about 24 percent have experienced increases in stored water. A common factor among the growing cases is their location in sparsely populated regions where human activity is lower.
Regions experiencing new reservoir development such as the Yangtze Basin in China and the Mekong Basin in Southeast Asia, as well as the interior of the Tibetan plateau and North America’s Great Plains, show positive trends. Spain’s Alarcón reservoir stands out as the sole example with a rising water volume among the studied sites.
The drivers behind lake impoverishment are not fully debated in the paper, but the authors point to climate change and increased human water use as primary factors. In addition, seepage plays a role in at least a subset of large lakes.
Two Billion People Affected
Lakes have historically supplied a larger share of human water than rivers, underscoring the importance of detailed lake data for resource planning. The researchers argue that this information should prompt policymakers to incorporate both consumption patterns and climate pressures into sustainable water management strategies. As co author Ben Livneh notes, reductions in water storage can be addressed through policy changes that curb excessive use.
The scale of impact is vast. About a quarter of the global population, roughly two billion people, lives near a lake that is drying. This reality heightens the urgency of coordinated water governance and proactive adaptation to rising temperatures and shifting rainfall.
Scientists advocate for integrating human behavior with climate trends to strengthen water management. Only by aligning policy with the realities of changing lake storage can societies meet future water challenges.
Reference work: Science doi 10.1126/science.abo2812.
Map illustrating the status of major lakes and reservoirs around the world appears in the Colorado Boulder globallakes project.
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Note: This article summarizes public research findings and emphasizes the need for responsible water stewardship on a global scale.