Avaliação físico química da qualidade de águas de reservatório de usinas hidrelétricas na Amazônia oriental

Abstract

Brazil has its energetic matrix composed mainly of hydroelectric power plants (HPP). In recent years, a large part of the projects for the implementation of these HPPs has been concentrated in the Amazon region of the country, which has great hydroelectric potential and has not yet been explored when compared to the other Brazilian regions. Studies that seek to monitor the quality of river waters are of great importance, since they allow the identification, analysis and prevention of problems, recovery and improvement of their environmental condition. Therefore, the objective of this research was to evaluate the physical-chemical quality of the waters of the HPP reservoirs present in the Araguari river, in the municipality of Ferreira Gomes-Amapá. To obtain data, water samples were collected at certain points in the reservoirs of Coaracy Nunes Hydroelectric Power Plant, Ferreira Gomes Hydroelectric Plant and Cachoeira Caldeirão Hydroelectric Plant, 4 samples per reservoir distant at 1000m, thus adding 12 samples multiplied by 2 collection periods, totaling 24 samples. The collection periods were defined in drought (October 2018) and rainy (February 2019). The analytical procedures were performed in the laboratory with the help of the manual of the National Health Foundation of 2013 and the physicochemical parameters analyzed were: true color, turbidity, total solids, temperature, chloride, calcium (hardness), pH, dissolved oxygen, iron and lead. The results of the monitored parameters were compared with the water quality standards established by Conama Resolution nº 357 of 2005 and Portaria nº 2914 of 2011 of the Ministry of health. The analyzes show, in general, good water quality results in the reservoirs, however, parameters such as pH, Dissolved Oxygen (DO) and lead indicate nonconformity with law in some samples in one of the collection periods. The results for Principal Components Analysis (PCA) show that there are differences in water quality in seasonal terms, and that the parameters color, turbidity, temperature and iron appeared to be larger contributions to this variation. In a Hierarchical Cluster Analysis, water quality grouping patterns were verified, in which two subgroups were identified for both collection periods, revealing that the points of the UHECN reservoir were the ones that distanced themselves from the others, while between the sampling points of the UHEFG and UHECC reservoirs maintained a similarity. Therefore, this study is a contribution to the environmental monitoring system of UHECN, UHEFG and UHECC, as well as to public and private sector managers who are concerned with changes that can be generated in the limnological characteristics in areas modified by dams