A groundbreaking assessment published in the journal Science reveals that over 50 percent of the largest lakes in the world are experiencing a significant loss of water. The primary culprits behind this concerning trend are the warming climate and unsustainable human consumption practices. However, the study also presents a glimmer of hope by introducing a novel method to track water storage trends and identify their underlying causes. This newfound knowledge can provide invaluable insights to water managers and communities, aiding in the protection of vital water sources and regional ecosystems.
Lead author Fangfang Yao, a climate fellow at the University of Virginia and a former CIRES visiting fellow, was inspired to undertake this research due to the environmental crises witnessed in some of the world's largest water bodies, such as the drying of the Aral Sea between Kazakhstan and Uzbekistan. Yao collaborated with researchers from the University of Colorado Boulder, Kansas State University, France, and Saudi Arabia to develop a technique capable of measuring changes in water levels across nearly 2,000 of the world's largest lakes and reservoirs, which represent 95 percent of the total lake water storage on Earth.
By combining satellite observations spanning three decades with advanced models, the team successfully quantified and attributed global trends in lake water storage.
Freshwater lakes and reservoirs globally account for 87 percent of the planet's water, making them a crucial resource for both human and ecological systems. While rivers receive significant monitoring attention, lakes often remain underrepresented. Surprisingly, lakes serve as the primary water source for a considerable portion of humanity, surpassing that of rivers.
Prior to this study, long-term trends and changes in water levels of lakes were largely unknown, leading to a knowledge gap that has now been bridged.
The researchers used approximately 250,000 satellite snapshots captured between 1992 and 2020 to assess the area of 1,972 of Earth's largest lakes. They gathered water level data from nine satellite altimeters, combining it with long-term records to minimize uncertainty. In cases where lakes lacked long-term level records, recent water measurements obtained from newer satellite instruments were utilized. By integrating recent level measurements with historical area measurements, scientists reconstructed the volume of lakes dating back several decades.
The findings were staggering: 53 percent of lakes globally experienced a decline in water storage. This loss is comparable to the combined magnitude of 17 Lake Meads, the largest reservoir in the United States.
The research team utilized recent advancements in water use and climate modeling to explain trends in natural lakes. The results showed that climate change and human water consumption were the primary drivers of the global net decline in natural lake volume, leading to water losses in approximately 100 large lakes. Some notable examples of lakes impacted by these factors include Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina, where human and climate change footprints on water losses were previously unknown. Surprisingly, both dry and wet areas of the world are witnessing shrinking lakes, indicating more widespread drying trends than previously understood, including humid tropical lakes and Arctic lakes. The study also assessed storage trends in reservoirs, revealing that nearly two-thirds of Earth's large reservoirs have experienced significant water losses. In existing reservoirs, the decline in water storage was primarily driven by sedimentation rather than droughts or heavy rainfall years. This is particularly true for reservoirs that were filled before 1992. While the majority of global lakes are shrinking, 24 percent experienced substantial increases in water storage. These growing lakes tend to be located in underpopulated areas such as the inner Tibetan Plateau and Northern Great Plains of North America, as well as in regions with new reservoirs like the Yangtze, Mekong, and Nile river basins.The research highlights the urgent need to incorporate human consumption patterns, climate change impacts, and sedimentation effects into sustainable water resource management. Astonishingly, approximately one-quarter of the world's population, equivalent to 2 billion people, resides in the basin of a drying lake, emphasizing the pressing importance of addressing these issues. The study also offers crucial insights into potential solutions. Ben Livneh, a co-author of the study and an associate professor of engineering at CU Boulder, suggests that if human consumption plays a significant role in the decline of lake water storage, adaptation and exploration of new policies can help mitigate large-scale declines.An encouraging example highlighted in the research is the case of Lake Sevan in Armenia. Over the past two decades, Lake Sevan has experienced an increase in water storage, which the authors attribute to the enforcement of conservation laws on water withdrawal since the early 2000s. This success story demonstrates the positive impact of proactive measures in preserving and replenishing water resources. The comprehensive assessment of global lake water storage trends underscores the alarming reality that more than half of the world's largest lakes are losing water. The study highlights the role of climate change and unsustainable human consumption as the key drivers behind this decline. However, the findings also present an opportunity for water managers and communities to take informed action in safeguarding critical water sources and preserving vital ecosystems. With the newfound method of tracking lake water storage trends and understanding their underlying causes, researchers can contribute to sustainable water resource management and offer valuable insights into policies and practices that can help mitigate the decline of lake water storage globally. By incorporating these insights, we can work towards a more sustainable future where our precious water resources are protected for generations to come.
References
University of Colorado at Boulder. "Half of world's largest lakes losing water: Climate change, human consumption and sedimentation contributing to decline." ScienceDaily. ScienceDaily, 18 May 2023. <www.sciencedaily.com/releases/2023/05/230518172007.htm>.
Comments