Relação entre índice de estado trófico e o uso do solo em áreas de preservação permanente no Rio Paraíba do Sul

The present study aimed to correlate the variables that could influence the water quality of Paraiba do Sul River (PSR), such as vegetation cover in the permanent protection areas (PPA), rainfall, and the Trophic State Index (TSI). The riparian zones were classified according to the vegetation cover from satellite images, as follows: Tree plant cover (TPC), Permeable area (PER), and Impermeable area (IMP). The total phosphorus (TP) and chlorophyll-a (CL) concentrations in the collected water were used to determine the TSI. A multivariate correlation analysis was carried out using the TSI values, rainfall, and vegetation cover. Also, the presence of cyanobacteria was evaluated. We observed a higher occurrence of IMP and PER in the riparian zones. The TP and CL concentrations increased during rainy periods, mainly in PER. The multivariate analysis demonstrated that the terrestrial areas influenced significantly the PSR parameters. PER contributed to the impairment of the water quality from the PSR, particularly in the rainy period. The presence of toxin-producing cyanobacteria was detected in the PSR. Our results reinforce the necessity to preserve and promote the restoration of the riparian areas in watersheds, mainly in the PSR.