Pollution slick on São Paulo’s biggest river up 40% in one year
On the Tietê River Day, celebrated today (Sep 22), a report by the SOS Mata Atlântica Foundation shows that the pollution slick on a monitored section of the state’s biggest river rose by 40 percent in one year. In 2021, the pollution stretched over 85 km. This year, the affected section totaled 122 km. The length displaying quality water also dropped—from 124 km last year to 60 km.
The Tietê is São Paulo’s largest river, running more than a thousand kilometers across the state from east to west. The monitoring was conducted by 35 volunteer groups between September 2021 and August 2022, covering 576 kilometers of the river, from its source in Salesópolis all the way downstream to the lock of the Barra Bonita reservoir.
The analysis was performed at 55 collection points spread over 31 rivers in the Tietê basin. Of the sites monitored, water quality was rated as good in seven (12.7%), regular in 34 (61.8%), poor in ten (18.2%), and terrible in four (7.3%). Since 2010 no record of optimal water quality has been made.
The main reason behind the reduction in the stretches with quality water and the deterioration observed—especially further into the state—is said to be the contaminated sediments accumulated in the Pirapora do Bom Jesus reservoir moving toward the Middle Tietê river. These sediments bring sewage along with them and also diffuse sources of pollution, such as garbage, pesticides, and car soot.
Another key factor is the emergence of new large urban areas in the Tietê region. According to the foundation, even though the water quality in the metropolitan region of São Paulo is below acceptable levels, an improvement has been perceived in recent years as a result of sanitation works.
Action
In a note, the state’s Infrastructure and Environment secretariat reported a 25 percent decrease from 2019 “when the slick was registered in 163 of the 576 km of the river surveyed by the foundation.”
The Tietê project, active since 1992, expanded the sewage collection network from 70 percent of the urbanized area to over 90 percent, the São Paulo government has reported. Besides, the treatment rose from 24 to 85 percent of the volume collected in the metropolitan region of São Paulo.
The secretariat also stated that the state government in September should sign a financing contract with the Inter-American Development Bank for the Renasce Tietê program. A total of BRL 500 million is expected to be invested in efforts to restore the river.
