NASA has conducted a study that explores the flow and storage of water in the Earth’s rivers. This research, published in Nature Geoscience, has uncovered important data about the quantity of water flowing through Earth’s rivers, the rate at which this water flows into oceans, and how these metrics fluctuate over time. Such information is key to understanding the global water cycle and managing Earth’s freshwater resources.
The study found that rivers contain only 2.5% of the world’s water, making them a minor yet critical component of Earth’s hydrosphere. Researchers from NASA’s Jet Propulsion Laboratory (JPL) in Southern California used an innovative method, blending flow meter data with computer models, to analyze over 3 million river segments worldwide.
This methodology provided a detailed estimation of water storage and flow, offering insights into the balance between natural river dynamics and human activity.
The researchers estimated that between 1980 and 2009, the total volume of water in Earth’s rivers averaged 539 cubic miles (2,246 cubic kilometers), equivalent to half the water in Lake Michigan and roughly 0,006% of all freshwater, which itself makes up just 2.5% of the planet’s total water volume.
Despite its small proportion, rivers have played a crucial role in human history, serving as sources of sustenance, transportation, and commerce since ancient times.
Cédric David, a co-author of the study, highlighted the importance of accurately assessing river water volumes. He likened the situation to spending money from a checking account without knowing the balance, emphasizing that understanding the actual volume of river water is foundational for effective water resource management, especially amid growing population pressures and climate change.
The new estimations could be compared with data from the international satellite Surface Water and Ocean Topography (SWOT), launched in December 2022, which maps water elevation across the planet.
This satellite data, in conjunction with the study’s findings, can further enhance our understanding of human impact on Earth’s water cycle.
The study pinpointed the Amazon Basin as the region with the most significant river storage, holding approximately 850 cubic kilometers of water, representing 38% of the global estimate.
This basin also discharges the most water into oceans, with 6,789 cubic kilometers annually, or 18% of the total river outflow into oceans, which averaged 37,411 cubic kilometers between 1980 and 2009.
Interestingly, the study also discovered segments of rivers, like those in the Colorado, Amazon, and Orange river basins, where more water enters than exits, indicating intense human water use. This phenomenon signals human impact, which can lead to reduced water availability and environmental stress.
The findings in this study are significant because they not only update long-standing estimates of global river water storage but also enable more detailed analyses of water flow and human impact across different regions. This knowledge can inform better water management practices and help ensure sustainable freshwater resources for future generations.
Sources
NASA | Collins, E.L., David, C.H., Riggs, R. et al. Global patterns in river water storage dependent on residence time. Nat. Geosci. (2024). doi.org/10.1038/s41561–024–01421–5
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