Abstract
Aim: This study assessed the water quality from the springs and river mouths of the fifth-order tributaries which compose the reservoir of Marechal Mascarenhas de Morais HPS in the middle Rio Grande watershed, Minas Gerais, Brazil. Methods: It has been studied 14 tributaries distributed in the reservoir, two points for tributary - spring and river mouth. Eighteen limnological variables added to the Rapid Assessment Protocol and Trophic Level Index were evaluated. The benthic macroinvertebrates had been collected by the use of a granulometric sieve and a Petersen-type sampler. Results: The cluster analysis of limnological data revealed the existence of two tributary groups. Group I consisted of eutrophic tributaries degraded by human activities, while group II exhibited good water quality and well-preserved environments. Group I was divided into two subgroups, Ia tributaries were characterized by being altered by human activities, while the Ib subgroup was composed of highly impacted tributaries. By ordering the PCA, it can be observed spatial segregation of groups, where the most polluted tributaries were separated from those which are better preserved. A total of 8,987 individuals belonging to 36 families of macroinvertebrates were identified. The family Chironomidae was the most abundant. There was no significant difference in total abundance and the richness of macroinvertebrates taxa inhabiting springs, by those who inhabiting the river mouths. Conclusions: It was noticed that most of the tributaries which supply and composes the reservoir are already degraded and have low quality water. It is observed that the human presence drastically affected water quality and faunal composition of tributaries. Thus, it is necessary a complementary study of the tributaries in working with issues related to reservoirs, as these components have direct influence on the water quality and composition of these lentic environments.
Highlights
Water is considered an essential resource for the possibility of life, regardless of amount or proportion
Averages and standard deviations of data on each physical, chemical and biological parameter evaluated in the water samples taken from springs and mouths of 14 studied tributaries are shown in Tables 1 and 2, respectively
According to CONAMA Resolution 357/2005 (Brasil, 2012a) that classifies water resources and establishes environmental guidelines, concentration of dissolved oxygen recorded in the tributaries – streams and mouths – exceeded 6 mg.L–1, classifying these waters as Class 1, that is, ecologically balanced environments
Summary
Water is considered an essential resource for the possibility of life, regardless of amount or proportion. Since the beginning of human civilization, societies have been using water for a wide range of purposes and history shows that the development and success of great civilizations is often based on the abundance and correct use of water resources in a given area (USEPA, 2000). The rapid growth of demographic density on a global scale associated with modernization in certain regions has resulted in a steady increase in power generation and water supply in urban centres. This additional demand has often required the construction of dams and reservoirs. Obvious effects are related to the dumping of domestic effluents released without treatment, leading to changes in faunal composition (Gaufin and Tarzewell, 1952; Hodkinson and Jackson, 2005) and nutritional load of water bodies (Paschoal et al, 2012)
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