09/30/2024 – 19:32
In recent days, visitors to Ibirapuera Park, south of São Paulo, have found the lake – one of the city’s postcards – green, cloudy and with an island due to the low water level. Furthermore, it is possible to see dead fish on the edge. The capital of São Paulo, like several regions of the country, is facing a period of severe drought this year. At the beginning of the month, the Pinheiros River also had a cloudy green color for days.
According to the São Paulo Municipal Green and Environment Secretariat, the reason for the change in the appearance of the water is due to the eutrophication process, intensified by water pollution with organic matter, high temperatures and lack of rain. The same explanation was given by the State Environmental Company (Cetesb) for the Pinheiros case.
As shown by Estadão, Brazil is facing the most serious drought in the last seven decades, since the beginning of federal measurements, according to the National Center for Monitoring Natural Disasters (Cemaden), linked to the Ministry of Science and Technology. It is the first time that drought has intensely affected such a wide region of the country, from the Amazon to Paraná, fueling fires and leading to record low rivers.
According to Cemaden, the drought tends to worsen until November, in general, in the country. In October, the municipality of São Paulo has a forecast of high temperatures and low levels of humidity, below 30%, according to the Center for Management of City Hall Climate Emergencies (CGE).
The CGE thermometers throughout the city read 28.4°C, on average, this Monday, the 30th, and the maximum could reach 33°C. Until Wednesday, the 2nd, the expected minimum is 19ºC and the maximum is 36ºC.
There is no rain forecast until Thursday, the 3rd, when there should be drizzle, according to the meteorology company Climatempo.
What do the authorities say?
The City Hall’s Green and Environment Secretariat, responsible for the Ibirapuera Park lake, says that, to improve water quality, it is necessary to activate the lake’s fountain pump. However, the lower than usual level “prevents the pumping system from functioning”. A similar measure has already been used by the State government in Rio Pinheiros, for the same reason.
The municipal department claims to monitor the situation of the lake in partnership with Urbia, the concessionaire responsible for managing the park since 2019, but has not, to date, indicated emergency actions, given the impossibility of using pumping.
When contacted, Urbia states that it carries out quarterly analyzes of the lake’s water quality, as per the commitment made in the concession contract. But he highlights that “the responsibility for the quality of the water in the park’s watercourses lies with Sabesp and the granting authority (the City Hall)”.
Sabesp, in turn, says that it “is not responsible for managing the lake”, but rather has a Flotation and Float Removal Station on the bed of the Córrego do Sapateiro, built in 2000, which contributes to water quality through the application of products that promote the flocculation of solid particles present in the water, to be removed after suspension on the surface. “The station operates normally.”
How does the eutrophication process happen?
Eutrophication, responsible for turning the waters of Lake Ibirapuera and the Pinheiros River green, is caused by the excessive proliferation of algae. It happens when there is a high concentration of organic matter in relation to the low liquid volume in the water body – that is, to reverse the situation, it is necessary to increase the amount of water and/or reduce the amount of organic load.
Algae proliferation is a phenomenon that can occur in rivers and lakes due to natural causes, but mainly as a result of human action, when the water is polluted.
Spilled sewage, pollutants, fertilizers and animal waste intensify the problem, which causes the proliferation of cyanobacteria and is harmful to both human and animal health, according to the Ministry of Health.
The water in Lago do Ibirapuera comes from Córrego do Sapateiro, which passes through neighborhoods such as Ibirapuera, Vila Clementino, Vila Mariana and Itaim Bibi, in the south zone. According to reports in “Portrait of Water Quality in the Atlantic Forest Hydrographic Basins”, from the Observing the Rivers program, from the SOS Mata Atlântica Foundation, irregular dumping of sewage into the stream was common in recent decades.
Interventions against the practice and actions to preserve the spring began to be carried out through the Pinheiros River depollution project, which has helped to improve the quality of the lake in recent years. In 2022, the lake’s water was considered “good” by Observando os Rios.
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