Reservoir at 5 Percent Capacity: Climate Change to Leave Sao Paulo’s 20 Million Without Water By November?

Suffering from its worst drought in over 84 years, the city of Sao Paulo is in the midst of a crisis. For as of this weekend the city’s primary reservoir — the Cantareira — had dropped to just 5 percent capacity putting millions at risk of losing access to water.

The fall prompted the city’s governor — Geraldo Alckmin — to again ask for permission to draw emergency water supplies from below flood gates to alleviate catastrophic losses from the Cantareira and ensure water supplies to the region’s 20 million residents. The move would tap a river system that feeds two other states also facing water shortages — Rio de Janeiro and Minas Gerais.  But the draw is only a temporary stop gap and, without rain, the Cantareira will continue to fall — bottoming out sometime this November.

cantareira-reservoir-sadesp-sao-paulo-brazil-february-2014

(Dam and section of Cantareira Reservoir high and dry under incessant drought conditions. Image source: Linhas Populares.)

Don’t Use the ‘R’ Word

The Cantareira provides water to nearly 50 percent of Sao Paulo’s residents. But ever since February of 2014 the multi-year long drought, a drought that has featured less and less seasonal rainfall over time, has triggered reduced water access by city and state residents.

Those living within areas served by the Cantareira have been treated to increasing periods of dry taps — being forced to go for longer and longer without available water supply. The intermittent lack of water service has put a strain on businesses and residents alike with many people living in Sao Paulo being forced to abstain from washing, cooking and brewing. For now, water for drinking can be stored during times when the faucets flow. But that time could come to an end all too soon without a change in the weather.

“Sometimes I have no water for two days, then it comes back on the next day and the day after that, I have no water again,” said Zeina Reis da Cruz, a 55 year old resident of one of Sao Paulo’s lower income neighborhoods in a September 25 interview with The Globe and Mail.

Despite an ongoing and growing failure to provide water services, the city refuses to use the word ‘rationing.’ Such an admission of failure would have weighed heavily on Alckmin’s re-election campaign (Alckmin was just recently elected to a new term as governor). Instead, irate citizens and businesses making calls to utilities are simply told that there is nothing wrong with the water supply and to wait until the water comes back on.

Regardless of politically-motivated denials, water rationing is the most accurate way to describe what many Sao Paulo residents have been experiencing for 9 months now under a regime of systemic drought that just grows steadily worse with time.

Climate Change Spurred by Deforestation, Worsened By Atmospheric Heating

The great forest of the Amazon provides a rich source of water for both Brazil and surrounding countries. It captures as much as 80 percent of the tropical atmosphere’s heavy moisture load and re-circulates it locally – providing ongoing and consistent rains. A critical means of replenishing regional water sources.

But, over recent decades, a combination of clear cutting and human-spurred warming of the climate have been adding severe stresses to the Amazon. During the period of 2000 to 2010, the great rainforest lost 93,000 square miles of wooded land alone to clear cutting. By 2014, government restrictions had brought down the rate of loss to around 2,300 square miles per year, but by this time warming-related impacts to the Amazon were looking even more dire.

As the 2000s progressed, it was becoming ever-more-clear that a heating climate driven by human fossil fuel emissions was taking an increasing toll. For, during recent decades, the Amazon has been warming at a rate of around 0.25 C every ten years — about twice as fast as the global climate system. The added heat increased evaporation, pushing soil moisture levels below critical thresholds.

Drought Map South America

(It’s not just Sao Paulo, most of South America is showing ongoing rainfall deficits. Map provided by NOAA shows percent of normal precipitation received by South America this summer. Note the severe drying over much of the Amazon Rainforest and broader South America coupled with drought over Sao Paulo. Image source: Climate Prediction Center.)

This loss has, in turn, increased the prevalence of forest-destroying understory fires. And, according to a 2012 NASA study these understory fires have been burning away the Amazon at the rate of more than 30,000 square miles every ten years for nearly two decades. By late this Century, business as usual fossil fuel emissions and related warming of 4 degrees Celsius is expected to destroy about 85 percent of the Amazon, resulting in widespread desertification of a once-lush region.

Today, this period of initial drying caused by a human heating of the atmosphere appears to be putting the stability of Brazil’s most populous city at risk.

A Major Humanitarian Disaster

Typically for October, Sao Paulo receives between 80 and 100 mm of rainfall. So far this month, the number is approaching zero. Long range forecasts bring that total to just above 50 mm through the end of the month — about half the usual rainfall. Very dry for a month that is supposed to be the start of Sao Paulo’s rainy season, a period that usually runs from October through March. A rainy season once fed by a now greatly endangered and increasingly moisture-impoverished Amazon rainforest.

It would take a massive rainfall to replenish Sao Paulo’s reserves. The kind of rain event that would result in widespread devastation should it emerge. Now, city officials appear to be holding out for any rain to tip the scales on their swiftly shrinking water stores.

But if the worse happens. If this year is a repeat of last year which saw a parched rainy season. If the rains of October and November continue to delay or do not emerge at all, then Sao Paulo faces a terrible event. A complete drying out of its largest water store and a complete cut-off of water supplies for millions of residents.

It’s like Paulo Nobre, director of the Center for Weather Forecasting and Climate Studies at the National Institute for Space Research in Brasilia, recently noted:

“It will be a real humanitarian disaster if it happens. We are 20 million people: You can’t bring water on trucks for 20 million. So they are praying that rainfall will come – but it may not rain so much.”

Links:

Sao Paulo Water Supply at Risk in Extreme Drought

Unprecedented Drought Puts Sao Paulo Water Supply at Risk

Brazil Drought Crisis Deepens in Sao Paulo

Climate Conditions Determine Amazon Forest Fire Risk

NOAA’s Climate Prediction Center

Reversal of Fortune: Amazon Deforestation Increased by 28 Percent Over Past Year

Amazon Could Shrink by 85% Due to Climate Change

Sao Paulo Weather Forecast

Linhas Populares

Impacts of Deforestation

(Hat tip to Andy)

(Hat tip to Colorado Bob)

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