Seasonality effect on water quality in the Taquara Reservoir, Ceará, Brazil

Abstract

Water quality in reservoirs is a growing concern for environmental sustainability, water bodies play a vital role in providing drinking water, in agriculture and in maintaining aquatic ecosystems. It is noted that the water issue has been worsening over time, with the semi-arid region having the greatest impacts in relation to the water crisis, but today the concern about availability is notable in all regions of the world. This study assessed the impact of seasonality on the water quality of the Taquara Reservoir. The data utilized were sourced from the Water Resources Management Company (COGERH) for the period from 2016 to 2020. Parameters analyzed for water characterization included pH, dissolved oxygen, electrical conductivity, chlorophyll "a," cyanobacteria, Escherichia coli, total nitrogen, total phosphorus, chlorides, color, magnesium, potassium, sodium, total solids, and turbidity. Descriptive analyses and box-plot graph construction were employed to assess water body quality during seasonal periods, comparing concentrations of the analyzed variables with the maximum allowable values (MAVs) established by CONAMA Resolution No. 357/2005 for freshwater class 2. The concentrations obtained mostly fall within the limits permitted by CONAMA Resolution. However, parameters such as total phosphorus, dissolved oxygen, Escherichia coli, chlorophyll "a," and cyanobacteria did not comply with the legislation. The results suggest seasonal variations and anthropogenic contaminations. Emphasis is placed on the importance of understanding the influence of seasonal changes and adopting measures to reduce human interference, aiming at the preservation of the quality and sustainability of this vital resource.