Estiagem prolongada e conteúdo iônico das águas de dois reservatórios do semiárido brasileiro

Abstract

The main objective of this work is to investigate the hydrochemical behavior and the ionic content in two reservoirs in Ceará, Northeast Brazil, due to changes due to prolonged drought in the region. The study comprised the surface waters of the Banabuiú and Pedras Brancas reservoirs, with samples collected between 2005 and 2017. The parameters monitored were electrical conductivity, total hardness, higher ions, hydrogen potential, total dissolved solids and temperature. In addition, a hydrochemical approach was performed from the Piper, Gibbs and Chadha diagrams. The predominant cations were those of greater mobility for both dams, while bicarbonate anion was more incident in Banabuiú and chloride in Pedras Brancas. The surface waters of the Banabuiú reservoir were classified as bicarbonated mixed, while Pedras Brancas was predominantly chlorinated sodium. The Gibbs diagram was important to show the dominance of the action of the hydrological cycle on the interaction of the cations with the rocks and the interchange of the anions with the rocks prevailing the effect of the rains and the evaporation. For White Rocks, evaporation had a predominant effect in both cases, and the interaction between rocks and surface water occurred predominantly between cations. The Chadha diagram indicated that the waters of Banabuiú had greater interchange between the mobile cations and favored by surface runoff for bicarbonate. For White Stones, the reversals of the left inferior quadrant, referring to the dominance between Na+ and Cl‐ and indicating salinization, were emphasized.