Over Half of World's Largest Lakes Losing Water

2023

A groundbreaking study published in Science reveals that over 50% of the world's largest lakes are losing water due to a combination of climate change and unsustainable human consumption. This trend poses significant challenges to global water resources and ecosystems.

Researchers, led by Fangfang Yao, a climate fellow at the University of Virginia, analyzed satellite observations spanning decades to gain insights into lake water storage variability. Motivated by environmental crises, including the drying of the Aral Sea, an international team of scientists from various institutions developed a novel technique to measure changes in water levels across nearly 2,000 of the largest lakes and reservoirs, which account for 95% of the world's total lake water storage.

Freshwater lakes and reservoirs store 87% of the planet's water, making them vital for both human and Earth ecosystems. However, long-term trends and changes in water levels have remained largely unknown until now.

The study's results are striking: 53% of lakes worldwide experienced a decline in water storage, equivalent to the combined volume of 17 Lake Meads, the largest reservoir in the United States. Climate change and human water consumption were identified as the primary drivers behind the decline, affecting around 100 large lakes globally. Surprisingly, previously unknown factors such as the desiccation of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina also contribute to water losses. Notably, both dry and wet regions are witnessing a reduction in lake volume, highlighting more widespread drying trends than previously understood.

Large reservoirs faced significant challenges as well, with nearly two-thirds experiencing notable water losses. Sedimentation emerged as the leading cause of storage decline, surpassing the effects of droughts and heavy rainfall, especially in long-established reservoirs filled before 1992.

However, the study does offer some hope. Around 24% of lakes experienced significant increases in water storage, particularly in less populated areas like the inner Tibetan Plateau and the Northern Great Plains of North America. Regions with newly constructed reservoirs, such as the Yangtze, Mekong, and Nile river basins, also saw growing lake volumes.

The implications for sustainable water resource management are substantial, as a quarter of the world's population, roughly 2 billion people, resides in the basin of a drying lake. Urgent action is necessary to incorporate the impacts of human consumption, climate change, and sedimentation into effective water resource management strategies.

Ben Livneh, a co-author of the study and associate professor of engineering at CU Boulder, emphasizes the need to adapt and explore new policies to mitigate large-scale declines in lake water storage. Encouragingly, successful conservation efforts in Lake Sevan, Armenia, have led to increased water storage due to strict enforcement of conservation laws on water withdrawal.

As shrinking lakes become a global reality, it is imperative to protect these invaluable resources. Understanding the causes and effects of declining water storage will enable us to implement sustainable solutions and safeguard our precious lakes for future generations.