Climate change poses threat to thirsty São Paulo
Less predictable rainfall patterns are causing water supply problems in Brazil’s biggest city
When it rains in São Paulo, it pours. During tropical storms that punctuate late afternoons in summer, drains overflow on to pavements and floods are not uncommon.
But, despite its sobriquet as the Terra da Garoa, or land of drizzle, ensuring an adequate supply of clean water is a major challenge for Latin America’s biggest metropolis as the climate changes.
This was laid bare when the region’s worst drought in 80 years resulted in severe water shortages between 2014 and 2015. Sporadic outages in parts of the city sparked protests, as well as fears that reserves might run out.
Since then, the utility Sabesp — which serves 28m residents in the greater São Paulo area and eponymous state — has undertaken a range of measures and investments with the aim of avoiding a repeat episode.
Chief executive Benedito Braga insists the company is prepared, with systems that kick in for “extreme situations”.
“What we thought was an extreme situation is becoming more common,” he adds. “For 10 years, rainfall has been below average in the region. It’s very worrying”.
While a long dry spell was the primary reason behind the São Paulo crisis, it compounded other factors such as a growing population, polluted waterways and deforestation.
Levels in the city’s large Cantareira system of reservoirs, which serves around 7.5m people, dropped to below one-tenth of its capacity.
Sabesp then provoked controversy by lowering pressure in the distribution network, which temporarily led to taps running dry in certain neighbourhoods. But its other main defence tactic has had lasting benefits.
“During the water crisis, we gave economic incentives [discounts] for people to save water,” Braga says. “Then we removed it, but they changed their habits. Today, consumption is approximately 10 per cent less than before the 2014 crisis.”
To increase its resilience, Sabesp has also invested in schemes to boost the supply of water to the metropolitan region. Already planned before the crisis, works were accelerated on the flagship R$2.2bn ($405m) São Lourenço production system, built through a public-private partnership. It transports water from a reservoir 83km away, via a treatment plant, to around 2m residents in the west of São Paulo.
Other actions taken by Sabesp include clamping down on theft, fixing leaky pipes, cleaning contaminated rivers and planting trees in areas adjoining the Cantareira reservoir network.
Braga reckons cities in a similar position to São Paulo should now concentrate on boosting storage. “The theory of climate change is that we will have more intense rainfall and longer dry periods. To minimise this variability, you . . . need to build dams to store water — that’s lesson number one.
“There’s a very strong environmental lobby against the construction of dams. This needs to stop. People need to be more reasonable.”
Pedro Côrtes, a professor of environmental science at the University of São Paulo, commends the way Sabesp has changed management of the Cantareira system, so that less water is drawn when storage levels are low.
“But, in fact, our supply system is still strongly dependent on climatic conditions,” he says. “There is no negotiation with the climate, but adaptation. We always need to save water.”
“There is no negotiation with the climate, but adaptation. We always need to save water.”
Some scientists, including Côrtes, argue that deforestation of the Amazon is contributing to São Paulo’s water problems, given the importance of the “flying rivers” originating in the rainforest that bring clouds and rain to the central and southern regions of Brazil.
Braga sees it differently, though. “If deforestation causes drought, how did we have this huge flood [in 2010]? These variabilities are linked to phenomena on a global scale and it is the oceans that play a much more important role.”
The volatility of rainfall in the city region was made clear in February 2020, a month with the highest volume of precipitation in 77 years of measurement, according to Brazil’s meteorological service, Inmet.
Juan Carlos Castilla-Rubio, a São Paulo resident and chair of SpaceTime Labs, which helps companies optimise their use of natural resources, suggests that water-risky regions should introduce a “water stress early warning system”. This would issue predictive alerts so that water can be conserved in times of stress.
He also suggests that these areas could introduce a price mechanism that reflects water’s scarcity, by using artificial intelligence systems to establish water risk ratings.
But environmental campaigners argue that there needs to be a more fundamental rethink about water. Greater re-use of wastewater for activities like cleaning that do not require it to be drinkable would be a start, says Édison Carlos, head of the NGO Trata Brasil.
“We need to continue pursuing new ways of reducing our dependence on water accumulated in the reservoirs”.
Written by Michael Pooler and Carolina Pulice
