Rivers, streams cover substantially more of Earth’s surface than we thought

A new global map of rivers and streams created using satellite data suggests that the global surface area of these bodies of water is about 44% higher than previously thought. Only two studies to date have attempted to quantify the global surface area of rivers and these were based on limited data; yet important and complex chemical exchanges with the atmosphere and biosphere happen at the water-atmosphere interface of rivers. For example, rivers release roughly one-fifth of the carbon dioxide levels emitted by fossil fuel combustion and cement production. Using satellite data, George Allen and Tamlin Pavelsky created one of the most detailed databases of rivers and streams to date, called the Global River Widths from Landsat (GRWL) Database. It quantifies the surface area of rivers greater than 90 kilometers (km) in width. The authors performed a series of calculations to account for smaller rivers, for which less data is available. Collectively, global rivers and streams were estimated to cover roughly 773,000 km2 of Earth's global non-glaciated land surface – tens of thousands of kilometers squared higher than previous estimates. Regionally, the authors report more river surface area coverage in the Arctic (where the impacts of climate change on carbon fluxes are of major concern) than previous estimates have ballparked, and less in Europe, the U.S., and some other economically developed regions. Allen and Pavelsky note that the lower-than-previous estimate of river surface area in many developed areas may suggest large-scale impacts of human modification on river networks, although this hypothesis requires further testing.


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       https://www.eurekalert.org/jrnls/sci/summaries-06-29-18.php#D <h4>Related Journal Article</h4>http://dx.doi.org/10.1126/science.aat0636 
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