Variabilidade hidroquímica em dois reservatórios no semiárido brasileiro

Abstract

This study aims to analyze the dominant hydrochemical mechanisms and water management for use in the irrigation of two reservoirs in the Banabuiú basin, in the Brazilian northeast. The study comprisedthe surface waters of the Banabuiú and Pedras Brancas reservoirs, with samples collected between 2005 and 2017. The hydrochemistry of the dams was analyzed by varying the ionic ratios of the dominant ions over time, followed by the multivariate technique Principal Component Analysis (ACP). In order to classify the waters for use in irrigation, the ionic index was monitored by Ratio of Sodium Adsorption (RAS). The mobile Na+ and Mg2+ cations were dominant for both reservoirs, whereas the HCO3-anion was predominant in Banabuiú and Cl-in the White Stones, due to the characteristic chemical weathering between the ion exchange reactions. The chemical species correlated positively to the C1 axis in the two dams, confirming the occurrence of salinization as the main reaction mechanism. The empirical correlations between the ionic profile and available volume and volumetric precipitation represented an essential approach for hydroclimatic analysis. The RAS diagrams defined the waters of Banabuiú as of good quality,medium salinity and low risk of sodicity. The Pedras Brancas weed had high saline risk and low sodicity risk for most of the analyzed period.