Proposta de um índice de qualidade de águas para microbacias hidrográficas sob manejo silvicultural

This work aimed to develop a Water Quality Index (WQI) for the forestry sector. Therefore, to achieve this purpose, the physical and chemical characteristics of the water were monitored: Ca, Cu, Fe, K, Mg, Na, P, S, Zn, IC, OC, Chlor, Nitr, Sulf, Phosp, Ammo, Glyph, Alka, EC, Color, COD, CH, MH, DO, SS, DS, Sulfl, Temp, Turb and pH in four micro-watersheds (MW) under activities of forest management in the city of Aracruz, Espirito Santo, Southeast of Brazil, from January to June, 2012. The multivariate statistical analyses, the Principal Component Analysis (PCA) and the Factor Analysis (FA) indicated that the most significant variables in the variation of water quality to compose a WQI were: EC, Color, Chlor, Nitr, Mg, Alka, Na, IC, OC, Fe, pH and SS, responsible for a total variance of 61.77% of the data after the rotation of the factors using the normalized Varimax method. Variables related to the dissolved salts in water assumed higher weights due to the proximity with the sea. The proposed WQI proved itself to be efficient when evaluating the water quality of the monitored micro-watersheds, instead examining the variables independently.