Sao
Paulo’s Reservoirs are Drying Out When they Should Be Filling Up
13
January, 2015
It’s
the rainy season for Brazil. But, thus far, adequate rains have not
come.
A
persistent high pressure system has lingered over Brazil. A blocking
high of the kind that has now become so common with global
temperatures spiking to more than +0.8 C above 1880s averages —
thickening heat domes and granting these powerful weather systems an
ever greater inertia. A set of circumstances that has set off a
plethora of very severe droughts ranging the globe since the early
2000s.
During
early 2015, Brazil’s own persistent atmospheric block
re-strengthened over an Amazon whose water re-circulating abilities
have been crippled by a combined deforestation and ever more
prevalent wildfires. Ever since late December, the high has warded
off cold front after cold front. The result is a terrible extension
of the worst drought to impact Brazil in at least 80 years.
(No rain in sight in the NASA MODIS satellite shot for Southeast Brazil on January 11, 2015. During a typical day in January, the wettest month for Sao Paulo, the satellite map should be filled with clouds and storms. Not so for 2014 and 2015. Image source: LANCE-MODIS.)
During
December, this dogged weather system kept rainfall totals below
average — at about 80 percent typical amounts for that time of
year. But by January, the high had strengthened and only very weak
rains had fallen over Southeastern Brazil with most other areas
remaining dry. Now, drought
appears to be re-establishing a strong grip as weather forecasts call
for the typically strong January rains to be cut in half.
The
ongoing drought has had serious and widespread impacts throughout
Brazil — curbing production of everything from soybeans and
sugarcane to coffee and cattle. But the worst impact has been to the
water supplies of one of Brazil’s most populous regions — the Sao
Paulo megalopolis. There, an unofficial water rationing has been in
place since early 2014. A
rationing that has hit Sao Paulo’s least advantaged residents the
hardest.
Key
Reservoir Drying Out When it Should Be Filling Up
Over
the past six years, water levels for the Cantareira reservoir have
been in free-fall. By 2014, an 80 year drought pushed already falling
water levels radically lower. As an emergency measure, officials
added dead pool volume — a level usually below municipal water
inlets — to the reservoirs stated reserves. This move coincided
with shifting water levels lower.
But
the action only bought time for the failing reservoir as month after
month of drought continue.
(Water losses from the Cantareira Reservoir since 2009. What this ominous graphic shows is that rainy season failure was not isolated to last year’s epic drought. It is instead part of a six year event that may well represent an ominous trend. Image source: Brazil Water)
By
austral spring of 2014 (October), the Sao Paulo water system was
again under dire threat. Water levels at the Cantereira reservoir
fell to below 6% percent before officials diverted water from other
sources and allowed use of water below even already lowered levels.
This new arrangement moved water inlets deeper into the drying
reservoir. An action that essentially dropped Canteriera outlets to
city water supplies into the mud.
These
emergency actions by city and water planners added another few
percent to the radically diminished water supply. Hopes remained that
rains would return with the wet season starting in November and that
levels would rise enough to make it through the next summer.
But
with rains remaining weaker than normal throughout November and
December, water levels kept falling when they should have been
rising. By early January, reservoir levels had again fallen to below
7 percent.
On
Monday January 5, 2015 the level of Sao Paulo’s Cantariera
reservoir was at 6.9% capacity. Today, just one week later, the same
reservoir measured 6.5%.
9
Million Facing Lack of Water, Millions More at Risk
In
total the Cantareira reservoir serves 9 million residents in Sao
Paulo. These are mostly middle and lower class neighborhoods. And if
the current weather situation continues, that reservoir could be
empty come the start of the dry season in April. Such a situation
would force an even more extreme water rationing on a state that has
now become famous for water scarcity.
Unfortunately,
Cantareira isn’t the only Sao Paulo reservoir under threat. In
total, 5 out of 6 reservoirs representing the lion’s share of all
water for more than 20 million people are now at 39 percent capacity
or below.
The
Sistema Alto Tiete — a smaller reservoir serving about 4 million
Sao Paulo residents — is not far behind Cantareira. For as of today
volume in this reservoir stood at 11.3 percent capacity. A third and
fourth reservoir system — Rio Claro and Sistema Alto Cotia — now
stand at 27.5% and 30.% capacity respectively.
Together these two
systems serve another 2 million people. The Guarapiranga reservoir,
at 39.2 percent capacity as of 1/12/2015, serves another 4 million
people.
A
final Sao Paulo reservoir — the Sistema Rio Grande — serves about
2 million residents and remains just above 70 percent capacity.
If
current forecasts for January hold and February-March follow present
trends, then all these reservoirs with the probable exception of
Sistema Rio Grande will be under threat entering the fast approaching
dry season. A situation that would put nearly 20 million residents
under severe threat of losing municipal water service.
UPDATE:
In
addition to Sao Paulo, recent
reports show that 93 cities have rationed water services to
ever-broadening populations. In total, more than 3.9 million
people are estimated to have had their water rationed. In some cases,
water has been cut off to broad areas for as long as five days.
This
official water rationing began last year. But this year’s rationing
is broader in scope with water cut offs, which were at first limited
to isolated rural zones, now stretching into larger urban population center.
As
mentioned above with Sao Paulo, this water rationing is occurring
during the rainy season when water supplies should be building.
However, with rainfall totals for Brazil this summer far less than
the historic average and with a continuation of the worst drought in
more than 80 years, most reservoirs show dropping levels when they
should be filling.
In
total, what we see for Brazil is a sad example of what a combination
of climate change and deforestation can do to a previously water rich
region. Bad management in the face of this crisis and instances of
climate change denial are exacerbating an already desperate situation
there.
UPDATE:
The
Cantareira reservoir fell to 6.4% capacity on 1/13/2015 — a 0.5%
loss in just 8 days. System losses at this rate bring the reservoir
to zero in about 100 days. However, the current capacity, due to very
low level of water outlets may not be fully useable. In
addition, rainy ends in April at which point levels would be expected
to drop more precipitously.
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