Evaluation of the Space-Temporal Influence in the Trofia Indexes of the Rio Verde Grande Watershed

Abstract

Purpose: This study aimed to evaluate the influence of space-time variation to determine the trophic states of the tributaries of the Verde Grande river basin.   Theoretical framework: To maintain water quality in hydrographic basins, it is necessary to use a monitoring plan that demonstrates the qualitative and quantitative trends of natural resources and the influences exerted by human activities and natural factors on the environment.   Method: In this study, data from 20 monitoring stations located on rivers in the Rio Verde Grande watershed were compiled. The Trophic State Index (TSI) was used to monitor water quality by nutrient enrichment and its effect on algal overgrowth. The sampling data, carried out in the months of March, June, September, and December 2018, were obtained from the Instituto Mineiro de Gestão das Águas (IGAM).   Results and conclusion: The results allow inferring that there was no direct influence of temporal variations on TSI values, but that this basin is significantly impacted by the discharge of domestic, agro-industrial and textile industry effluents. Among the analyzed rivers, it was concluded that the Mosquito, Gorutuba, Verde Grande and Vieiras rivers had the worst trophic indices in the Verde Grande River basin.   Research implications: The contribution of this research is to present an efficient method to monitor the water quality of rivers, having as parameters the enrichment by nutrients and the excessive growth of algae that can lead to eutrophication.   Originality: The originality comes from the analysis of trophic indices to assess the water quality of rivers, which can be applied to other rivers in Brazil.