Longitudinal gradient in limnological variables in the Upper Paraná River: a brief description and the importance of undammed tributaries

Abstract

Aim: Describe the limnological pattern in a longitudinal gradient in the Paraná River, a highly dammed river, in a stretch localized between two dams, but rich in undammed tributaries. Methods: Twelve transects in the longitudinal gradient of the Paraná River were sampled, with the first transect being placed right after Porto Primavera dam, and the last one in the lotic region of the Itaipu dam. In each of these transects, water transparency, electrical conductivity, pH, total nitrogen and total phosphorous were analyzed. Results: In those regions nearer Porto Primavera dam it was observed high values of water transparency and low values of nitrogen and phosphorous. The values of water transparency decreased and the values of nitrogen and phosphorous increased as the distance from Porto Primavera dam increased. Because the new tributaries connect to the Paraná River, with the sites farer from Porto Primavera dam presenting values similar to those prior its construction. Conclusions: Increase in the nutrients concentration and changes in ecological integrity are probably due to the presence of the undammed tributaries. They are originate in different river basins and therefore contribute to the Paraná River in distinct manners. Results presented here are an indicative of the fundamental importance of undammed tributaries in mitigating damming negative impacts in extremely dammed rivers and highlight the importance of keeping such tributaries free of dams.

Spatio-temporal study of water quality in a subtropical reservoir and related water bodies in Southern Brazil

“…Orthogonal transformation was used to facilitate the interpretation of the factors that composed the matrix.Varimax rotation was applied, distributing factor loadings so that high weights for each variable in a single factor and low or moderate weights in other factors were obtained [17].The latent-root approaches, established by Kaiser (1958) [19]was used for factor selection, where all factors with eigenvalues higher than 1 were considered significant. For factor characterization, the variables with absolute weight higher than or equal to 0.7 were considered [18].Thus, the factors considered significant in FA were analysed and plotted on a chart [20]- [22].…”

“…The Kruskal-Wallis test of the selected factors was conducted to identify the relative contribution of seasonality and the location to variations of the water quality of the different sampling stations. In this way, the axes of the factor analysis selected for interpretation were tested one at a time, using time and space as explanatory variables, and axis score as dependent variable [20]- [22].…”

“…Limnological variables that presented more explanation for the FA were also tested by Kruskal-Wallis to check the relationship space-time, being those used as explanatory variables and the empirical data as dependent variables [20]- [22]. For applying AF, the R statistical environment was used [23].…”

“…The study conducted by Santana et al (2017) [22], also in the upper Paraná river, identified that the dam Porto Primavera retains more than 70% of total phosphorus of the Paraná river. Similarly, to what was found in this study, low values of total phosphorus and nitrogen occurred, as well as high values of transparency of the water downstream of the dam.…”

Dinâmica Fluvial e Caracterização Limnológica do Córrego do Cedro, Presidente Prudente -São Paulo/ Brasil

“…Nesta perspectiva, a inerência entre ciências como a geomorfologia fluvial e a limnologia tem apresentado grande contribuição para estudos ligados a avaliação da qualidade de ambientes fluviais, como pode ser observado em trabalhos desenvolvidos por (Meissner et al, 2016;Chargas et al, 2017;Francisco, 2017;Santana et al, 2017).…”