SIMILARIDADE DAS VARIÁVEIS HIDROQUÍMICAS COM O USO DA ANÁLISE MULTIVARIADA, NA BACIA DO SALGADO, CEARÁ

Abstract

This study aimed to identify the similarities among hydrochemical variables describing the groundwater qualities in the Salgado watershed river (Southern Ceará), with the use of multivariate statistical analysis. Also, the groundwater hydrochemistry was investigated and classified using the Piper diagram. The study was developed from secondary data provided by the CPRM (Centro de Estudo Geológico do Brasil, previously Companhia de Pesquisa de Recursos Minerais). The geological formation of the Salgado basin has two aquifer systems, one on sedimentary rock (porous, karst and alluvial) and another on (fractured) crystalline rock. The research was conducted in 24 groundwater wells spread out over the drainage area of the basin, with data having been collected for the last 10 years. The water samples were analyzed for their content of Na+, K+, Ca2+, Mg2+, Cl-, CO3, HCO3 -, SO4 2- and CE. Two groups were formed by the use of cluster analysis, and both were independent with respect to their hydrological characteristics, and similar in hydro geological formation. The water quality study showed no temporal interference. The two components explained 78.30% of the total variance of the water quality. According to the Piper diagram, the waters were classified as 55.6% mixed chlorided water and 40% mixed bicarbonate water, in groups 1 and 2 respectively. The hydrochemical characterization of the studied waters implied no limitation to their human consumption.