Aplicação do índice de salinidade das águas superficiais em reservatórios do trópico semiárido cearense

Abstract

Brazil holds approximately 12% of the world's freshwater reserves. However, the uneven distribution of rainfall in the Northeast, concentrated in a few months of the year, requires careful management of water resources. In Ceará, where the semi-arid climate predominates, the construction of reservoirs was essential to guarantee water supply during dry periods. However, in addition to eutrophication, salinization has become a relevant problem, impacting water quality and restricting its use for irrigation and human consumption. The study aims to develop a Salinity Index (ISal) to classify the waters of reservoirs in the State of Ceará, Brazil, using the multivariate Principal Component Analysis (PCA) technique, through the PAST Software version 5.0.2. Data obtained from the HidroWeb/Cogerh portal were examined, covering the period from 2016.2 to 2021.1, with a total of four reservoirs selected. The PCA indicated that chloride (Cl⁻), sodium (Na⁺), magnesium (Mg²⁺) ions and electrical conductivity (EC) are the main factors in the formation of ISal. The results revealed seasonal variations in water quality, influenced by the hydrological and ecological conditions of the region. The Edson Queiroz reservoir presented the highest concentrations of Cl⁻, Na⁺ and Mg²⁺, reflecting on the EC and impacting water quality. ISal values ranged from moderate to high use restrictions, highlighting the importance of continuous monitoring for the sustainable management of water resources in the semi-arid region of Ceará. In addition, it was possible to identify distinct geographic zones regarding the vulnerability of reservoirs to salinity, highlighting areas with greater restrictions.