The pollution stain of the Tietê River has grown this year and now extends over 122 kilometers, an increase of 43% compared to 2021, when it reached 85 kilometers, according to a report by the SOS Mata Atlântica Foundation.
The data are from Observing the Tietê 2022 report, released on Thursday, September 22, Tietê River Day.
The monitoring was also done by a technical team from the Água Limpa cause and showed that the good quality water was reduced from 124 kilometers last year to only 60 kilometers in the current measurement.
The pollution has made the water unsafe in 21.18% of the 576 km monitored. According to the foundation, the study was conducted by 35 volunteer groups, between September 2021 and August 2022, from the source, in Salesópolis, to Barra Bonita.
The data points out the compromising of the Alto Tietê, Sorocaba Middle Tietê, and Piracicaba-Capivari-Jundiaí (PCJ) Basins, which correspond to half of the Tietê River Hydrographic Basin.
The largest river in São Paulo state, with 1,100 kilometers from source to mouth, the Tietê cuts the state of São Paulo from east to west and is divided into six water resource management units (UGRHs), also called hydrographic basins.
The data were compiled with the Water Quality Index (WQI) average at 55 collection points distributed over 31 rivers in the Tietê basin, with 11 points along the main river.
These analysis points are spread over 27 municipalities, 14 of which are in the state capital.
Gustavo Veronesi, coordinator of the Observing the Rivers program, says that the main reason for the loss of stretches with good water quality and the worsening, especially in inland cities, is the transfer of contaminated sediments accumulated in the Pirapora do Bom Jesus reservoir to the Tietê River.
The sediments have high loads of Biochemical Oxygen Demand (BOD) and gather remains of sewage and garbage, pesticides, and car soot.
“The greater revolving [operation that prepares the land for sowing] of the soil for planting and the more intense use of fertilizers and pesticides for crops have implied a great production of sediments that reach the rivers and carry with them nutrients and pollutants, which form algae and consume the water’s dissolved oxygen”, he explains.
WATER QUALITY
In 2021, 53 points were monitored, with a good index in six, regular in 36, bad in seven, and terrible in four.
In the Upper Tietê basin, in the headwaters region, the indicators show an improvement in the environmental condition and a reduction in the Biochemical Oxygen Demand (BOD) in the Tietê and Pinheiros rivers.
However, they are still in terrible condition, according to the study. The worst measured result is in the Edgard Souza Reservoir in Santana do Parnaíba.
The situation with algae directly affects tourism in Barra Bonita, where there are boat trips that can go up the locks.
Residents of the area were worried about the intense green coloration that affected the water again at the beginning of the year.
According to Veronesi, another cause for the increase of the stain is the expansion of cities and the appearance of large urban areas in the Tietê region.
According to him, in the metropolitan region of São Paulo, even though the water quality is still below acceptable levels, there has been an improvement in recent years due to sanitation works.
The Tietê River Basin covers 265 municipalities, with a total area of 9,172,066 hectares, 79% of the territory in the Atlantic Forest biome, 7,227,066 hectares, and the rest in the Cerrado.
On July 28, 2010, the United Nations General Assembly declared access to clean and safe water and sanitation as a human right essential for life and a condition for achieving all other human rights.
PINHEIROS RIVER
Three of the four bad spots are in the Pinheiros River, in São Paulo’s capital, part of the Tietê River Basin. The Pinheiros went through sanitation actions, within a cut of the Tietê River Clean-up Project, in the New Pinheiros River.
The program connected more than 649,000 properties in the Pinheiros river basin to the sewage network, benefiting more than 1.8 million people.
This semester the Recovery Units (URs) start operating, which will treat the water in the streams and remove the organic load, according to the state government.
The survey shows that the collection points at the Jaguaré, Cidade Jardim, and João Dias Bridges were analyzed.
With the sewer connections, according to the foundation’s specialists, it may take time to observe improvements in the water quality, but in the river smell, the result is already positive.
According to the report, only one point of analysis went from regular to good condition. The monitoring points of the Sapateiro and Água Podre streams in the state capital registered an improvement in the IQA.
TOXIC FOAM
In Salto, the region presents a phenomenon in which the river is covered by foam when the waters are agitated. Gustavo Veronesi says that pollution with soap and cleaning product residues causes the situation.
“The foam in Salto is mainly due to the beginning of the rapids. The Tietê runs through the metropolitan region, practically without any slope, and from Santana do Parnaíba on; it has rapids.
“In Salto, the soap in the water when it passes [through the rapids], which is the residue of detergent, soap, soap, untreated sewage, gets agitated and forms foams.”
An improvement was seen in the Pirai River in Salto, where the water quality went from regular to good. The indices that indicate compromised water quality were measured in four points that went from regular to bad.
The river lost quality in Botucatu, which had been showing good quality and dropped to regular.
The specialists believe that climatic factors of diffuse pollution and the transfer of pollution loads and contaminated sediments from the Upper Tietê reservoirs to the Middle Tietê have impacted the indicators.
The loss of water quality in inland stretches would also be due to pesticides and chemical fertilizers.
There was a worsening in the Caiacatinga and São Luiz rivers, in the interior of the state of São Paulo, in the area covered by the Sorocaba Mid Tietê Hydrographic Basin Committee.
In the Jundiaí river in Salto, a loss in quality was also noted in the collection point influenced by population growth.
With information from G1