Earth's rivers cover 44 percent more land than recognized

BY LEAH WILLIAMS
Posted on FEB 18, 2019

Satellite maps suggest that waterways traverse approximately 773,000 KM.

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, according to the American Association for the Advancement of Science.

Particularly two studies to date have attempted to quantify the global surface area of rivers, noting that these were based on limited data.
Important and complex chemical exchanges with the atmosphere and biosphere happen at the water-atmosphere interface of rivers. The study provides examples, such as rivers releasing 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, authors Allen and Pavelsky report more river surface area coverage in the Arctic, distinctly where the impacts of climate change on carbon fluxes are of a major concern than previous estimates have ballparked. Remarkably, the report displays less in Europe, the U.S., and 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, emphasizing the hypothesis necessitates additional examination