Selection of indicators of salinity in surface waters of the Metropolitan basin, Ceará using multivariate analysis

Abstract

The objective of this research was to evaluate the behavior of salinity of surface water reservoirs of the Metropolitan bowl of Ceará, Brazil, as well as identify by multivariate statistical Factor Analysis/Principal Components Analysis (FA/PCA) the determining factors in the variability of water salinity. The data were supplied by the Company of Water Resources Management of Ceará available to the National Institute for Scientific and Technological Salinity/UFC - INCTSal with a total of 290 samples of 7 reservoirs. The parameters evaluated were: electrical conductivity of water (EC), sodium (Na⁺), calcium (Ca⁺²), magnesium (Mg⁺²), chloride (Cl^-) and bicarbonate (HCO₃^-). The results show that the waters of the reservoirs showed no risk to severe risk of causing salinity problems and toxicity for use in irrigated agriculture, and the Castro and Pompeu Sobrinho dams, with the main problems of concentration of salts. The FA/PCA best fit a model consisting of two factors explaining 89.02% of total variance was identified. The first factor is related to the total dissolved salts in surface water,
represented by the parameters EC, Na⁺, Cl^-, Ca⁺² and Mg+2 . The second factor basically expresses the effect of dissolving salts of carbonates in the basin represented by the HCO₃^- anion.