The sources of Maracanã river are located inside the Atlantic Forest, in Tijuca National Park. Within the conservation area, its waters are clean and clear. However, following its course, the strong urbanization, which promotes irregular dumping of domestic and industrial effluents and garbage into its waters, results in the degradation of water quality along the entire river to the site of its mouth, the Guanabara Bay.
In this work, the water quality parameters of the Maracanã river (Biochemical Oxygen Demand (BOD), Total Phosphorus (TP), Nitrate (NO3), Dissolved Oxygen (DO), pH, Turbidity (T) and Thermotolerant Coliforms (TC)) for the period between 2012 and 2019, were determined in two monitoring points of the State Institute for the Environment (INEA). Data were evaluated in accordance with CONAMA Resolution No. 357/2005, which provides environmental classification and guidelines for the framing of surface water bodies, as well as establishes the conditions and standards for the release of effluents.
The obtained results, for the period considered in this study, indicate the classification of water quality for the Maracanã River as bad (years 2012, 2013 and 2016) and very bad (years 2014, 2015, 2017, 2018 and 2019). These results can be correlated with the great disorganized urbanization process in the region, with the disposal of waste and effluents in the river. The highest average value for the water quality index (29.28) was determined in 2016, which can be attributed to local actions of the Guanabara Bay Depollution Program, carried out that year, for the Rio Olympics-2016.
This work also indicates that the region of the “Canal do Mangue sub-basin”, where the Maracanã River is located, despite its great importance in terms of its biodiversity, has most of its water resources polluted. This fact shows the government neglect in this location and highlights the urgency in taking corrective and mitigating measures, both along the entire Maracanã River and in its tributaries.