Pollution patch on Tietê River grows 43% in one year

The pollution patch on the Tietê River grew by about 43% in a year and now reaches 122 km of water body in the state of São Paulo. There was also a decrease in good water in the river, according to the analysis carried out by Fundação SOS Mata Atlântica as part of the Observando os Rios project.

The study, carried out annually since 1993, points to the presence of stretches with poor water quality in both Tietê and Pinheiros, its tributary — this despite the investment of billions of reais by the state government for depollution.

The situation is surprising, according to Gustavo Veronesi, coordinator of Observando os Rios, precisely because of these recent sanitation actions, especially on the Pinheiros River. Although the situation in the great São Paulo river has worsened, that of the basin as a whole remains relatively stable.

Project volunteers collected water samples from September 2021 to August 2022 at 55 points in the Tietê and other rivers that make up its basin, including the Pinheiros.

In addition, SOS Mata Atlântica used 16 indicators to compose the water quality index, including data from Cetesb (Companhia Ambiental do Estado de São Paulo). The project monitors 576 km of the river, which in total is approximately 1,100 km long.

The pollution patch can be translated as the extension of the river without oxygen dissolved in the water. Under these conditions, water, in general terms, cannot be used by humans — but it can be used for navigation, for example.

According to the index used by the foundation, 117 km of the river have poor water quality and 5 km have poor water quality — documented in the Edgard Souza reservoir region, in Santana do Parnaíba (in Greater São Paulo).

In the previous analysis, not one kilometer of Tietê had poor quality and 85 km had bad water.

To make matters worse, the 124 km of good water were reduced to only 60 km (a decrease of around 51%). As in the last two years, no stretch reached optimal quality.

While in the metropolitan region of São Paulo the water quality of Tietê was stable, the situation worsened in the interior, according to the analysis.

“Now problems are appearing in the Tietê River that were previously concealed with this argument that the metropolitan region throws sewage into the river. Now the damage that is caused in the interior is appearing with greater clarity”, says Veronesi.

The climate situation may explain, in part, the worsening in the interior. During this period, the state went through a period with rainfall below the expected volume, according to Veronesi, which led to a decrease in the flow of the river and, consequently, a greater concentration of organic material.

Allied to this, the worsening of quality in the interior can also be explained by the use of fertilizers and pesticides in the agricultural environment, which eventually end up in water bodies. When they reach the rivers, these products serve as a nutrient for the proliferation of plants that end up consuming the oxygen in the water, which, ultimately, impairs the quality of the water.

Finally, the SOS Mata Atlântica report also points to the expansion of urbanization (which, of course, is a continuous process lasting decades) in the interior of the state, which reinforces the need for improvements in sanitation in other areas beyond the metropolitan region. .

Even with the results, there are solutions on the horizon, says the coordinator of Observando os Rios. An example is the lake at Ibirapuera Park, in the city of São Paulo, fed by the Sapateiro stream, part of the Pinheiros basin.

The lake’s water quality, which was regular until the last analysis, is now good — including, in 2021, fish filmed in the Pinheiros River possibly came out of the Sapateiro stream. It is the result of efforts to improve sanitation.

Another point that improved within the city of São Paulo was the Água Podre stream, in the Butantã neighborhood, a self-explanatory name for the situation of local waters — which went from bad to regular, a category in which, after advanced treatments, the liquid it may even be destined for human supply.

In other words, a case like the Pinheiros River can be reversed. “If this classification existed, the Pinheiros River would be in ‘very bad’, ‘beyond bad’. Now it is getting worse. It’s not going to get better overnight”, says the specialist. “But it has improved. The aspect is not as dark as it used to be, the discomfort of being on the riverbank doesn’t happen so much anymore.”

wanted by Sheet, Cetesb states that the SOS Mata Atlântica study is carried out in a collaborative manner and that the measurements on the Pinheiros River “do not reflect the systematic data monitored by Cetesb”.

“As for the Tietê river spot, the 2019 SOS Mata Atlântica report compared to the 2022 report shows a 25% decline in the pollution spot”, he says, in a note to Cetesb. “During the pandemic period, according to SOS Mata Atlântica’s 2021 report, the measurement was impaired due to the decrease in points and the frequency of analyses. Scientific references show that it is not possible to compare atypical periods, such as the influenced years by the pandemic, which registered changes in society’s behavior.”

The state government has highlighted the improvements in the Pinheiros River, through the Novo Pinheiro Program, after billions were invested and with the connection of more than 624 thousand properties in the Pinheiros River basin to the sewage network.

At Usina São Paulo (formerly Usina da Traição), which is on the course of the river, there are plans for the construction of a cultural and gastronomic hub, inspired by Puerto Madero, in Buenos Aires, which would be a new postcard for the capital. . Despite this, there is always the emphasis on the fact that it will never be possible, for example, to take a dip in Pinheiros.

Veronesi says that the expansion of sanitation and the concern with cleaning up the Tietê and Pinheiros areas must continue in the next government, whatever it may be.

“I am reluctant when people say that the Tietê River is the most polluted in Brazil. It is not. I think it is unfair for a river that has more than 1,100 km, with 10% of them with compromised quality, to put the stain of a polluted river. polluted by 10%, for reasons that can be solved”, says the coordinator of Observando os Rios. “If we take care of each little river in the basin, we can improve the big river.”