Evaluation of the Water Quality of the River Basin of São João River in the Municipality of Porto Nacional - Tocantins

Water is an essential natural resource for the maintenance of the life of man and the numerous ecosystems present on the planet Earth, besides enabling several activities that generate income for civilizations. The main objective of this work is to analyze the water quality of the São João River basin in the city of Porto Nacional - Tocantins, by determining the Water Quality Index (WQI). For the development of this work, it was established three research points, located downstream of the São JoãoRiver. The samples were collected monthly and, for six months, from August 2018 to January 2019. The results obtained demonstrated that the water from São João River can be classified as regular according to NSF, although some parameters compared to environmental legislation were in disagreement with the standards determined by CONAMA resolution 357/2005 for freshwater class two.