By Herton Escobar, in São Paulo, Brazil
“Welcome to the Cantareira Desert,” says the graffiti spray-painted on a rusted- out hatchback. Not long ago, the car was fully submerged in the Atibainha reservoir,
part of the Cantareira water system near São
Paulo, Brazil’s biggest metropolis. But driven
by a mysterious atmospheric anomaly, a
2-year-long drought has exposed the decay-
ing hulk to the elements—and exposed all of
southeast Brazil, a region home to 85 million
people, to a crippling water crisis.
“This is a very serious situation. We are
not just talking about water shortage,” says
Paulo Nobre, a senior meteorologist at the
National Institute for Space Research’s
(INPE’s) Center for Weather Forecasting
and Climate Research in Cachoeira Pau-
lista. “We are talking about the possible
collapse of our most important water sup-
plies.” Some are bracing for rioting. “There
is a real risk of social convulsion,” warns
José Galizia Tundisi, a hydrologist with
the Brazilian Academy of Sciences (BAS),
which in a press conference last week took
state authorities to task for failing to take
bolder actions sooner and for a lack of
transparency about the gravity of the situ-
ation. “Authorities need to act immediately
to avoid the worst.”
The São Paulo government has reduced
the water pressure in its mains, which reg-
ularly leaves faucets running dry. And it is
now taking a carrot-and-stick approach to
water usage, financially rewarding those
who conserve and, starting last month, fin-
ing those who waste. Barring a sudden re-
versal of meteorological misfortune, officials
are contemplating drastic rationing that
would deprive millions of households of wa-
ter for up to 5 days a week. During Brazil’s
dry season coming up in a couple of months,
Tundisi says, the shortages will be “brutal.”
He and other Brazilian scientists blame
a climate anomaly for the lack of rain—and
poor governance for the ensuing predica-
ment. “Everybody needs to be prepared for
increasingly extreme climate events,” ar-
gued 15 weather and water experts with
BAS in an 11 December open letter. They
called for rapid and substantial invest-
ments by Brazil’s state governments to tap
new water resources and expand sanitation
systems to clean up surface water sources
that are now too polluted for any usage.
Normally, the Southern Hemisphere
summer is southeast Brazil’s rainy season,
brought about by a weather pattern called
the South Atlantic Convergence Zone.
But for 2 years running, persistent high
pressure—Antonio Nobre, Paulo’s brother
and a fellow researcher at INPE, calls it
an “atmospheric pachyderm”—has blocked
the convergence zone from taking hold and
has impeded the southward flow of water
vapor from the Amazon. “There is very
strong evidence that a great part of the
rain that falls in the southeast comes from
Amazonia,” he says. As a result, precipitation levels in December and January—the
region’s two wettest months—were half the
average in 2014 to 2015.
The high-pressure system has stumped
scientists. It seems unconnected to ocean
temperatures or other large-scale weather
phenomena. “We have never seen this before,” says Marcelo Seluchi, a director of
the National Center for Monitoring and
Early Warning of Natural Disasters in Cachoeira Paulista. Many experts see the dark
hand of human-induced global warming. “I
think this will go down in the books as yet
another extreme event related to climate
change,” says Paulo Nobre.
Whatever the cause, the anomaly has
left vast sections of Brazil’s waterworks in
shambles. The Cantareira system, which
provides water for 8.8 million people, is so
depleted that authorities are tapping the
last 8%—little more than stagnant dregs.
Also teetering on collapse is São Paulo’s
Alto Tietê water system, serving approximately 3.5 million people, with 15% of its
water remaining. Reservoir levels are in difficult condition in the neighboring states
of Rio de Janeiro and Minas Gerais, raising
red flags across the entire industrialized
southeast, which is responsible for 55% of
Brazil’s gross domestic product. A system
for piping in water from the Paraíba do Sul
watershed during emergencies won’t be
ready until at least next year. “We are driving around on a very low tank, with a big
desert to cross ahead of us, and we don’t
know if there will be any gas stations along
the way,” says Paulo Nobre.
Even if rainfall were to return to normal,
“it will take several years to rebuild these
reservoirs,” says Tundisi, who helped draft
the BAS letter. He says the drought’s pervasive impacts will be enormous, hobbling
industry and agriculture and hampering
operations at hospitals, schools, and prisons, for example. He fears a reprise of what
happened in Itu, 100 kilometers west of São
Paulo. In September and October, protests
over water shortages there turned violent,
sparking vandalism and clashes with police.
Imagine what could happen in a metropolis
of 20 million without water, Tundisi says. ■
812 20 FEBRUARY 2015 • VOL 347 ISSUE 6224 sciencemag.org SCIENCE
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IN DEPTH
Drought triggers alarms in
Brazil’s biggest metropolis
Water shortages blamed on climate anomaly, tardy response
WATER SECURITY
In the Cantareira reservoir system, all that’s left are
the dregs.