All reservoirs that supply Greater SP are in deficit compared to 2013, pre-water crisis; expert predicts water shortage in 2022 | São Paulo

All reservoirs that supply the metropolitan region of São Paulo are on this Tuesday (31) in water storage deficit compared to 2013, the year before the last water crisis, according to data from the Basic Sanitation Company of the State of São Paulo (Sabesp). In the total volume stored, the difference is 19.2 percentage points.

The comparison with 2013 helps to understand the gravity of the current situation. If in 2013 we had more water available and there was a supply crisis in the following two years, the current situation points to a probable lack of water in houses in Greater São Paulo next year, according to researcher Pedro Luiz Côrtes, professor of the Program Graduate Program in Environmental Science at the Institute of Energy and Environment (IEE) at the University of São Paulo (USP).

“Systematically, as indicated by climate forecasts carried out since the end of last year – and updated monthly – the situation of the water sources is getting worse. Today, we have that all producer systems available in 2013 are worse off. As a result, we have 19.2 percentage points less water stored in 2021 than in the same period in 2013. This reinforces the perspective that this new water crisis will turn into a supply crisis in 2022.”

To worsen, the forecast for the coming months continues to be less rain and drier (read more about weather forecasts below).

This Tuesday (31), the Cantareira System, the main water supplier in the region and responsible for supplying 7.2 million people daily, operates with 37.1% of its storage, a difference of 10.2 percentage points in relation to to 47.3% stored on the same August 31, 2013.

The current situation of Cantareira is considered alert state, characterized by volume equal to or greater than 30% and below 40%. To be considered normal, the reservoir needs to operate with at least 60% of its capacity.

The second most important reservoir in the region is the Alto Tietê, which supplies 5.2 million people in Greater São Paulo. It operates on Tuesday with 44.6% of its volume, 14 percentage points below that registered in 2013.

The most serious situation is the Rio Claro system, which supplies 1.3 million people. This Tuesday, it operates with 44.1% of storage, a drop of 54 percentage points from 98.1% on August 31, 2013.

Only the São Lourenço system is not in deficit, as it began operating in 2018 and comparison becomes impossible, therefore. Its contribution is the smallest among all the reservoirs, supplying 1.1 million people a day.

When questioned, Sabesp said that the current interconnection system between the reservoirs allows the transfer of water between regions, but it does not clarify how this can help in the current situation, when all reservoirs have low storage.

“The current situation of the reservoirs defeats the assumption that a production system could compensate for the reduction in capacity of another system. Today, all systems that operated in 2013 are worse off. The São Lourenço System, which started operating in 2018, serves just over 5% of consumption in the metropolitan region of São Paulo. It is not capable of reversing the situation of scarcity in other production systems”, says Côrtes.

See below the situation of each reservoir that supplies the metropolitan region of São Paulo this Tuesday (31), compared to the volume of 2013:

Storage difference of August 31, 2013 and August 31, 2021

Producer SystemPercentage stored on 08/31/2013Percentage stored on 08/31/2021Deficit 2021-2013
stonemason47.337.110.2 percentage points
Alto Tietê58.644.614 percentage points
Guarapiranga84.350.234.1 percentage points
Cotia93.158.534.6 percentage points
big River94.671.922.7 percentage points
clear river98.144.154 percentage points
St. Lawrence57.30

Forecast is drier

The aggravating factor in the current situation of the springs that supply Greater São Paulo is that the forecast for the coming months continues to be of little rain.

According to data from the Climate Prediction Center of the International Research Institute for Climate and Society, at Columbia University, the current Neutral Phase (without El Niño or La Niña) should remain until the end of winter.

The start of La Niña finds more favorable conditions between August and October and the phenomenon is expected to continue until the summer, which ends in March of next year, as shown in the chart below:

Graph indicates possible incidence of La Niña as of August, which is reflected with less rainfall in the Southeast — Photo: Center for Climate Prediction of the International Research Institute for Climate and Society at Columbia University

La Niña is a phenomenon that, unlike El Niño, lowers the surface temperature of waters in the central and eastern tropical Pacific Ocean. But, like El Niño, it generates a series of significant changes in precipitation and temperature patterns on the planet.

What happens is that La Niña changes the pattern of winds in the equatorial region, which become less intense, and this changes the arrival of cold fronts from the southern region towards São Paulo.

Thus, the phenomenon reduces rainfall in the southern portion of Brazil, and this may have repercussions in São Paulo, depending on its intensity.

The lack of prospects for rain makes the scenario even worse, according to Professor Cortes.

“It is essential that Sabesp presents the scenarios it has been working with. It is necessary to deal with effective numbers. Statements that there is nothing to worry about are not enough. The indicators of the water sources, throughout the year, show the opposite. We are dealing with the supply of more than 20 million people.”

O G1 questioned Sabesp about the deficit pointed out by Côrtes, but, until the last update of this article, it has not received a return. On August 13, the company stated in a note, regarding the drop in the volume of supply of the Cantareira System, that “there is no risk of shortages at this time in the Metropolitan Region of São Paulo, but it reinforces the need for the conscientious use of water”.

“The Company has been carrying out in recent years actions that provide more water security to the RMSP: infrastructure expansion (especially the Jaguari-Atibainha Interconnection and the new São Lourenço System, both in operation since 2018), integration and transfer between systems, in addition to of communication campaigns for the conscientious consumption of water by the population. These initiatives allow us to affirm that there is no risk of shortages in the Metropolitan Region at this time of drought and Sabesp forecasts satisfactory levels for the coming months until 2022.”

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