Avaliação da qualidade das águas do açude Santo Anastácio

Abstract

Brazil has a large quantity of freshwater, but the Northeast Region and state of Ceará suffer scarcity of this resource. In function of this, many rivers were barred to build reservoirs. Within this context, there is the Santo Anastácio dam (ASA), the object of this research, located in Fortaleza-Ceará. ASA is suffering progressive losses in the quality and depth of waters, mainly due to human actions. Thus, this study aimed to diagnose the evolution of this degradation by physical, chemical and biological analysis, as well as to calculate the water quality index (IQA) for ASA, to evaluate eutrophication and siltation levels and to study the spatial and temporal variability of their limnological parameters. All methods used here were based on the 21st edition of Standard methods for the examination of water and waterwaste - APHA-AWWA-WPCF. By the results, it was possible to conclude that some of the analysed parameters, including OD, total phosphorus and BOD, were evaluated against the established standards for freshwater, class 3, by “Resolução CONAMA nº357”, in which ASA was classified according to its predominant uses. This means that this reservoir is unfit for the purposes for which it is currently used. The results indicated a low quality of the waters, according to IQA, which oscillated between good and bad, with deterioration in quality, at the point 1, which is the region of ASA dam near the community that resides in its surroundings. About the level of eutrophication, it was classified as hypertrophic, higher ranking in artificial aging process. Regarding the temporal variation of the parameters, it can be concluded that there was seasonal, with the influence of local climate. This fact was observed by the study of correlations among the climatic factors using Tukey’s test and ratified by Principal Component Analysis (PCA). In relation to spatial variation, it was not observed in most variables, except the OD, that exhibited heterogeneity at the point 1, according to Tukey’s test.