More than 50% of the world's largest lakes are losing water due to climate change and unsustainable human consumption, reveals a groundbreaking assessment in Science. However, lead author Fangfang Yao highlights that this research provides crucial insights for water managers and communities to protect these vital water sources and ecosystems.
Yao and a team of researchers developed a technique to measure changes in water levels across nearly 2,000 of the world's largest lakes and reservoirs, which represent 95% of the Earth's total lake water storage. By combining three decades of satellite observations with models, they assessed global trends in lake water storage.
Freshwater lakes and reservoirs store 87% of the planet's water, making them essential for humans and ecosystems. However, they have been poorly monitored compared to rivers. This research fills the knowledge gap, providing comprehensive estimates of global lake levels and volume.
Using satellite data from 1992 to 2020, the team analyzed snapshots of 1,972 large lakes. They found that 53% of lakes globally experienced a decline in water storage, driven by climate change and human water consumption. Surprisingly, many factors contributing to lake water losses were previously unknown.
Water losses were observed in both dry and wet areas worldwide, suggesting more widespread drying trends than previously realized. Additionally, nearly two-thirds of large reservoirs globally experienced significant water losses primarily due to sedimentation.
While most lakes are shrinking, 24% showed significant increases in water storage, mainly in sparsely populated areas and regions with new reservoirs.
The study highlights that approximately 2 billion people, or a quarter of the world's population, live in basins of drying lakes, emphasizing the urgent need to integrate factors like human consumption, climate change, and sedimentation into sustainable water resource management.
Addressing human consumption can mitigate large-scale declines, as seen in Lake Sevan in Armenia, where enforcement of conservation laws on water withdrawal led to increased water storage in the last two decades.