In a groundbreaking assessment published in Science, researchers have discovered that more than 50 percent of the world’s largest lakes are experiencing significant water loss. The warming climate and unsustainable human consumption are the main factors behind this troubling trend. However, the study also offers hope by providing a new method to track lake water storage trends and identify their causes. By leveraging satellite data and models, scientists can offer valuable insights to water managers and communities on better protecting these vital water sources and regional ecosystems.

Lead author Fangfang Yao, a climate fellow at the University of Virginia, was inspired to conduct this research due to the environmental crises observed in some of the Earth’s largest water bodies, such as the drying of the Aral Sea. Yao and a team of researchers from various institutions developed a technique to measure changes in water levels in nearly 2,000 of the world’s largest lakes and reservoirs, representing 95 percent of Earth’s total lake water storage. By combining satellite observations spanning three decades with advanced models, the team was able to quantify and attribute trends in lake storage on a global scale.

Freshwater lakes and reservoirs store 87 percent of the planet’s water, making them crucial resources for humans and Earth’s ecosystems. Surprisingly, unlike rivers, these vital water sources have not been adequately monitored, despite their significant contributions to humanity. This study marks the first comprehensive assessment of long-term trends and changes in water levels in lakes worldwide. By analyzing 250,000 lake-area snapshots captured by satellites from 1992 to 2020, the researchers surveyed the areas of 1,972 of Earth’s largest lakes. They combined recent and long-term water level measurements to reconstruct lake volumes dating back several decades.

The study’s findings are alarming, with 53 percent of lakes globally experiencing a decline in water storage. To put this loss into perspective, it is comparable to the volume of 17 Lake Meads, the largest reservoir in the United States. The team found that climate change and human water consumption are the primary drivers of this global net decline in natural lake volume, leading to water losses in approximately 100 large lakes. The study also revealed previously unknown impacts of human activities and climate change on lake water losses, such as the desiccation of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina.

Even more concerning is that dry and wet areas worldwide are witnessing lake volume reductions. This suggests more widespread drying trends in humid tropical and Arctic lakes than previously understood. The research also examined reservoir storage trends and found that nearly two-thirds of Earth’s large reservoirs have experienced significant water losses. Sedimentation emerged as the leading cause of storage decline in existing reservoirs, surpassing the effects of droughts and heavy rainfall years, especially in long-established reservoirs.

While most global lakes are shrinking, there is a glimmer of positive news. Around 24 percent of lakes observed showed significant increases in water storage. These growing lakes are in sparsely populated areas, such as the inner Tibetan Plateau and the Northern Great Plains of North America. Additionally, areas with new reservoirs, like the Yangtze, Mekong, and Nile River basins, have also seen water storage increases.

The study highlights the urgent need to incorporate human consumption, climate change, and sedimentation impacts into sustainable water resource management, as roughly one-quarter of the world’s population, amounting to 2 billion people, resides in the basin of a drying lake. The researchers believe that understanding the role of human consumption in lake water storage decline can lead to the development of new policies that can aid the planet’s freshwater reserves.

References

• CIRES. (2023, April 27). Satellites reveal widespread decline in global lake water storage [Text]. CIRES; University of Colorado Boulder. https://cires.colorado.edu/news/satellites-reveal-widespread-decline-global-lake-water-storage
• Yao, F., Livneh, B., Rajagopalan, B., Wang, J., Crétaux, J.-F., Wada, Y., & Berge-Nguyen, M. (2023). Satellites reveal widespread decline in global lake water storage. Science, 380(6646), 743–749. https://doi.org/10.1126/science.abo2812