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Global Lake Water Storage: A groundbreaking assessment published in Science reveals that over 50 percent of the world’s largest lakes are experiencing a significant loss of water. The primary culprits behind this alarming trend are the escalating effects of climate change and unsustainable human consumption practices.
However, there is a glimmer of hope amidst these findings, as lead author Fangfang Yao, a climate fellow at the University of Virginia and former CIRES visiting fellow, explains.
By employing an innovative method to track water storage trends and identify their underlying causes, scientists can now offer invaluable insights to water managers and local communities.
This knowledge empowers them to implement more effective measures for safeguarding critical water sources and preserving vital regional ecosystems.
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Unveiling Comprehensive Trends and Drivers of Global Lake Water Storage Variability
Yao’s research was spurred by the environmental crises witnessed in some of the world’s largest bodies of water, exemplified by the desiccation of the Aral Sea between Kazakhstan and Uzbekistan. To tackle this issue, Yao collaborated with colleagues from esteemed institutions such as the University of Colorado Boulder, Kansas State University, France, and Saudi Arabia.
Together, they devised a technique capable of measuring changes in water levels across nearly 2,000 of the planet’s most prominent lakes and reservoirs, which collectively account for 95 percent of the Earth’s total lake water storage.
Their approach involved merging three decades of satellite observations with advanced modeling techniques to quantify and attribute trends in global lake storage.
This comprehensive assessment provides a crucial understanding of the current state of freshwater lakes and reservoirs worldwide, as they constitute a staggering 87 percent of the Earth’s water resources.
Surprisingly, lakes, despite their immense significance, have remained inadequately monitored when compared to rivers, even though they cater to a larger portion of humanity’s water needs.
Revealing the Unknown: Distressing Long-Term Trends in Water Levels
The lack of reliable data on lake levels and volume has hindered our ability to comprehend long-term trends and changes in water levels—until now.
Balaji Rajagopalan, a professor of engineering at CU Boulder and co-author, emphasizes the need for precise estimates on a global scale, beyond the iconic lakes like the Caspian Sea, Aral Sea, and Salton Sea.
The novel methodology developed by the team now allows for comprehensive insights into global lake level changes, expanding our perspective on this critical issue.
The researchers harnessed 250,000 lake-area snapshots captured by satellites between 1992 and 2020 to survey 1,972 of the Earth’s largest lakes.
By collecting water level data from nine satellite altimeters and incorporating long-term records to minimize uncertainty, they achieved a more accurate understanding of lake volumes over the past few decades.
In cases where long-term level records were unavailable, recent water measurements from newer satellite instruments were utilized.
This combination of recent and historical measurements enabled scientists to reconstruct lake volumes dating back several years.
Staggering Results: Over Half of Global Lakes Experience Water Storage Decline
The findings of this comprehensive assessment are nothing short of staggering. The study reveals that a shocking 53 percent of lakes worldwide have witnessed a decline in water storage. To put this into perspective, this loss is equivalent to the magnitude of 17 Lake Meads—the largest reservoir in the United States.
The team, in their effort to explain trends in natural lakes, leveraged advancements in water use and climate modeling. Climate change and human water consumption emerged as dominant factors contributing to the global decline in natural lake volume.
Moreover, these factors were identified as key drivers of water losses in approximately 100 large lakes, many of which were previously unknown. Distressing examples include the desiccation of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina.
Alarming Trends: Water Losses Impact Dry and Wet Areas Alike
The concerning trends extend to both arid and humid regions across the globe, affecting lakes in tropical and Arctic zones alike. These losses in humid tropical and Arctic lakes indicate more extensive drying trends than previously understood.
The researchers’ analysis also encompassed reservoirs, revealing that nearly two-thirds of large reservoirs on Earth have experienced significant water losses.
Sedimentation, the accumulation of sediment over time, emerged as the primary cause of global storage decline in existing reservoirs. Ben Livneh, a co-author and associate professor of engineering at CU Boulder, emphasizes the dominance of sedimentation over droughts and heavy rainfall years in long-established reservoirs. These findings underscore the urgent need to address sedimentation as a crucial factor in preserving water resources.
Encouraging Signs: Certain Lakes Experience Increased Water Storage
While the majority of lakes worldwide are shrinking, the study identifies a positive trend wherein 24 percent of lakes experienced a significant increase in water storage.
Notably, these growing lakes tend to be located in sparsely populated areas within the inner Tibetan Plateau and Northern Great Plains of North America. Additionally, areas with newly constructed reservoirs, such as the Yangtze, Mekong, and Nile river basins, have also witnessed notable increases in water storage.
Implications for Sustainable Water Resource Management
The researchers estimate that approximately one-quarter of the global population, comprising 2 billion people, resides in a basin connected to a shrinking lake. These findings underscore the urgent need to incorporate the impacts of human consumption, climate change, and sedimentation into sustainable water resource management practices.
Fortunately, the research also sheds light on potential solutions, as Livneh highlights. If human consumption significantly contributes to the decline in lake water storage, it becomes crucial to explore adaptive measures and new policies aimed at mitigating large-scale declines.
A prime example of successful conservation efforts can be seen in Lake Sevan in Armenia. Over the past two decades, the lake has experienced increased water storage due to the enforcement of conservation laws on water withdrawal since the early 2000s.
Details provided by University of Colorado at Boulder.
Journal Reference: Fangfang Yao, Ben Livneh, Balaji Rajagopalan, Jida Wang, Jean-François Crétaux, Yoshihide Wada, Muriel Berge-Nguyen. Satellites reveal widespread decline in global lake water storage. Science, 2023; 380 (6646): 743 DOI: 10.1126/science.abo2812