Evaluation of the Water Quality at the Mouth of the São Francisco River-Brejo Grande/SE

Objective: The objective of this study was to identify the critical changes that occur at the mouth of the São Francisco River caused by saline seawater intrusion. Theoretical Framework: Monitoring natural resources, especially freshwater, is essential because it makes it possible to perceive problems, whether natural or anthropogenic, that are threatening the ecosystem and, consequently, human health. Method: Water samples were collected during the dry and rainy seasons, in five points located along the mouth of the river. At each point two samples were taken, the first at the surface and the second between five and eight meters below the surface of the water. Results and Discussion: The results were classified in accordance with the resolutions of the National Environmental Council (CONAMA). Salinity levels above the acceptable amounts were recorded at the first three points with point 1 having an average of 15.0 PSU. The salinity levels show that the mouth of the river has already been compromised and saltwater is pushing further upstream. BOD levels varied between Classes 1, 2 and 3, with the majority being in class 2. Point 4 had elevated BOD levels up to 10 mg/L indicating the presence of point source pollution. Research Implications: The practical and theoretical implication of this research is discussed, and an immediate plan of action is needed to combat the saltwater intrusion at the mouth of the river and sanitary conditions need to be improved upon in to order restore the São Francisco River back to a healthy and steady state. Originality/Value: This study contributes to the literature by evaluation of the water quality at the mouth of the São Francisco River-Brejo Grande/SE. The relevance and value of this research are evidenced by knowledge of the effects caused by the saline intrusion of seawater at the mouth of the São Francisco River.