The world today faces a major problem that is the pollution of water resources, occurring a huge loss of water quality. The quality monitoring is of utmost importance for obtaining physical, chemical, biological and ecological information of water resources through sampling. However, this research will cover a study of the waters of São João river, an important water resource for the municipality of Porto Nacional-TO, to meet the demands of the city in relation to supply, fishing, leisure, among others. This project will be directed in three stages: study and demarcation of three points of the hydrographic basin, field methodology and then laboratory methodology. The parameters to be analyzed are: temperature, oxygen, pH, total nitrogen, total phosphorus, electrical conductivity, total of coliforms, total of solids and turbidity. The project will examine the quality of the water, verifying if the basin has the necessary parameters determined by Resolutions 274/2000 and 357/2005 of the National Environmental Council (CONAMA).