World's Largest River Floods Five Times More Often Than It Used to
Sep 24 2018 | 03:02:54
Extreme floods have become more frequent in the Amazon Basin in just the last two to three decades, according to a new study.
After analyzing 113 years of Amazon River levels in Port of Manaus,
Brazil, researchers found that severe floods happened roughly every 20
years in the first part of the 20th century. Now, extreme flooding of
the world's largest river occurs every four years on average—or about
five times more frequently than it used to.
"With a few minor exceptions, there have been extreme floods in the
Amazon basin every year from 2009 to 2015," study lead author, Jonathan
Barichivich, environmental scientist at the Universidad Austral de
Chile, said in a press release.
This increase in flooding could be disastrous for communities in
Brazil, Peru and other Amazonian nations, the researchers pointed out.
"There are catastrophic effects on the lives of the people
as the drinking water gets flooded, and the houses get completely
destroyed," Barichivich told the Thomson Reuters Foundation.
The study, published Wednesday in the journal Science Advances, also determined that droughts in the Amazon Basin have increased in frequency.
"Our findings unravel the ultimate causes of the recent
intensification—wet season getting wetter, and dry season getting
drier—of the water cycle of the largest hydrological basin of the
planet," Barichivich told Retuers.
The researchers linked the increase in flooding to a strengthening of
the Walker circulation, which is induced by the contrast of warm
Atlantic waters and the cooler waters of the Pacific.This ocean-powered
air circulation system, which influences weather patterns and rainfall
in the tropics and elsewhere, can partly be attributed to shifts in wind
belts caused by climate change, as Reuters noted about the study.
"This dramatic increase in floods is caused by changes in the
surrounding seas, particularly the Pacific and Atlantic oceans and how
they interact. Due to a strong warming of the Atlantic Ocean and cooling
of the Pacific over the same period, we see changes in the so-called
Walker circulation, which affects Amazon precipitation," study co-author
Manuel Gloor, from Britain's University of Leeds, said in the press
release. "The effect is more or less the opposite of what happens during
an El Niño event. Instead of causing drought, it results in more
convection and heavy rainfall in the central and northern parts of the
With temperatures in the Atlantic expected to continue warming, the
scientists expect to see more of these high water levels in the Amazon
"We think that it's going to continue for at least a decade," Barichivich told Reuters.