MADRID, April 29 (EUROPA PRESS) –
A new methodology by NASA researchers calculates that only 0.006% of all the fresh water on Earth flows through the Earth’s rivers, which in turn represents 2.5% of the total water.
The investigation, published in Nature Geoscienceestimates that the total volume of water in the Earth’s rivers on average between 1980 and 2009 was 2,246 cubic kilometers.
Researchers at NASA’s Jet Propulsion Laboratory used a novel methodology that combines flow measurements with computer models of about 3 million river segments worldwide.
Although researchers have made numerous estimates over the years about the amount of water that flows from rivers to the ocean, estimates of the volume of water that rivers collectively hold (known as storage) have been few and more uncertain, said Cédric David, co-author of the study.
He compared the situation to spending from a checking account without knowing the balance. “We don’t know how much water is in the account, and population growth and climate change are making things even more complicated,” said David it’s a statement. “There are a lot of things we can do to manage how we use it and make sure there’s enough water for everyone, but the first question is: How much water is there? That’s critical to everything else.”
The paper’s estimates could eventually be compared with data from the international Surface Water and Ocean Topography (SWOT) satellite to improve measurements of human impacts on Earth’s water cycle. Launched in December 2022, SWOT maps water elevation around the world, and changes in river heights offer a way to quantify storage and discharge.
38 PERCENT ARE FOUND IN THE AMAZON
The study identified the Amazon basin as the region with the greatest river storage, with approximately 850 cubic kilometers of water, approximately 38% of the global estimate. The same basin also dumps the largest amount of water into the ocean: 6,789 cubic kilometers per year. That’s 18% of global discharge to the ocean, which averaged 37,411 cubic kilometers per year between 1980 and 2009.
Although it is not possible for a river to have a negative discharge (the study’s approach does not allow for upstream flow), for accounting purposes, it is possible for some segments of the river to leave less water than entered. That’s what researchers found in parts of the Colorado, Amazon and Orange river basins, as well as the Murray-Darling basin in southeastern Australia. These negative flows mostly indicate intense water use by humans.
“These are places where we are seeing fingerprints of water management,” said lead author Elyssa Collins, who conducted the analysis as a JPL intern and doctoral student at North Carolina State University in Raleigh.
