University of São Paulo Reports 26% Decrease in Reservoir Supply Compared to Last Year
The severe drought affecting the Southwest, Southeast and Central-West regions has affected hydroelectric reservoirs. However, the concern is not only with the generation of electricity; water supply is also a warning sign. In the interior of São Paulo, for example, cities such as Atibaia, Bauru and Vinhedo are already rationing water. In the metropolitan region of São Paulo, scarce and irregular rainfall is causing concern regarding the level of the reservoirs used for water supply.
Professor Pedro Luiz Côrtes, professor at the Institute of Energy and Environment at USP, analyzes the issue: “It is not an emergency situation now, it is a situation that requires attention, because the level is low and we should not have a substantial recharge within a year and this could really cause harm to our supply”.
He draws a parallel between the need for precaution and the previous crisis of 2014-2015. “From a technical point of view, it was already present in 2013, even in 2012. If measures had been taken at the time to warn the population, this would have prevented us from entering the so-called dead volume of the Cantareira system. So it is very important to issue these warnings in advance so that the population avoids, for example, washing the sidewalk with a hose.”
The situation of the reservoirs
According to the expert, several of the reservoirs that supply the Metropolitan Region are at levels around 50% or well below that. “This is the case of Cantareira, which is at 50.1% and is the main reservoir and supply system for the Metropolitan Region of São Paulo. Alto Tietê, which is the second largest system, is at 45.8%; Guarapiranga, at 38.3%.”
Compared to last year, at this same time, the aggregate of all reservoirs was at a level of 65%, and today it is at 48% full. Pedro Luiz Côrtes comments that “Sabesp claims – and is correct in this – that the general level has remained at the average of the last five years, but this always causes concern regarding the possibility of how this will unfold in the future”.
Weather phenomena
The expert explains that this situation is due to the irregularity of rainfall in recent times. “We had a very rainy period last summer and last spring, due to the El Niño phenomenon, which significantly recharged the reservoirs. But after El Niño ended, we are still in a transition phase, which we call the neutral phase, between El Niño and La Niña. The name of this neutral phase can be misleading, because it gives the impression that the climate will behave normally, but that is not the case.”
During this transition period, there is alternation between little and no rain, causing reservoirs to reach lower levels than last year. In the near future, La Niña may also affect the scenario. Initially, the phenomenon does not interfere much in the Central and Southeast regions, but with climate change, the impacts are becoming increasingly unpredictable: “Often, this drought in the South region ends up affecting part of the Southeast region, and it is important to remember that the last general water crisis we had occurred precisely under the effect of La Niña.”
The good news is that, after the 2014 crisis, Sabesp made a series of investments, “whether to expand water collection for the Cantareira system, or to interconnect these distribution systems, in such a way that one system can partially compensate for the other, if one system has a slightly lower level, it can use another system to replace it”, explains Côrtes.
Finally, he brings a message: “I reiterate that it is important that we take action from now on, reinforcing the need for consumption, rational use of water, conscious consumption, so that we can keep reservoirs at minimally adequate levels to avoid potential greater restrictions on consumption.”