A multivariate approach to analyze the spatial-temporal variation of limnological parameters of the reservoir of the Curuá-Una hydroelectric plant

Abstract

The construction of reservoirs for hydroelectric plants (HP) began in the 1960s and is currently an integral part of the objectives of economic expansion plans in Brazil. The Curuá-Una HP was the first HP constructed in the central Amazon. Due to the great importance of this reservoir for limnological studies in the Amazon, the objective of this study was to analyze and quantify the percentage of spatial-temporal variation of limnological variables upriver of the reservoir of the Curuá-Una hydroelectric plant. Sampling was conducted between 2016 and 2017. The limnological variables analyzed were water transparency, conductivity, turbidity, dissolved oxygen, pH, biological oxygen demand, nitrate, silica, total phosphorus, and chlorophyll-a. Principal components analysis was used to investigate patterns and the size of the gradient in the reservoir, and to select which spatial and temporal variables make significant contributions a canonical redundancy analysis (RDA) was conducted incorporating a partitioning of variance. PCA showed that the samples were seasonally grouped, and the first two axes explained 51.74% of the variability. The RDA and partition of variance showed that the spatial and temporal explanatory variables together explained 66% of the variability (time = 56%, spatial = 10%, time and spatial = 0%, residual = 34%). The results obtained suggest that the seasonal effect is responsible for 56% of the variability, and such changes in time are sufficient enough to alter the biological processes when environmental conditions are turbulent.