SEASONAL ANALYSIS OF WATER QUALITY IN THE AYRES DE SOUSA RESERVOIR, CEARÁ, BRAZIL

Abstract

Water is an indispensable resource for the maintenance of terrestrial life, however this resource has been inadequately treated, compromising the quality and various uses of water bodies. Given this scenario, the objective of this research is to evaluate the effect of seasonality on the water quality of the Ayres de Sousa reservoir, seeking to identify the variables that may be interfering with the natural state of this water body. The data used for analysis belong to the water quality monitoring database of the Water Resources Management Company - COGERH, and the period from 2016 to 2020 was analyzed, with data representative of the rainy (first semester) and dry periods (second half). The parameters used for the characterization of the weir water were: pH, dissolved oxygen (DO), electrical conductivity of water (EC), chlorophyll a, cyanobacteria, Escherichia coli, total nitrogen, total phosphorus, chlorides, color, magnesium, potassium, sodium, total solids and turbidity. To assess the quality of the water body, descriptive statistical analyzes were applied in the construction of box-plot graphs in seasonal periods, in order to represent the behavior of the water quality variables. Most of the values found are within the limits allowed by CONAMA Resolution 357/05 for class 2 fresh waters, the parameters total phosphorus, dissolved oxygen, Escherichia coli, chlorophyll and cyanobacteria did not meet the CONAMA resolution. The results point to possible changes due to seasonality, as well as contamination by anthropogenic interference, since the variables that did not comply with the legislation are indicative of contamination by organic matter.