O efeito da renovação das águas na qualidade de água em um manancial de abastecimento na região semiárida

Abstract

The eutrophication process in water bodies, caused by the enrichment of nutrients such as nitrogen and phosphorus, represents a growing threat to water quality. This phenomenon, intensified by human activities and climate change, affects both the availability and quality of water, especially in regions with frequent water scarcity, such as the northeastern Brazilian semi-arid region. Although water renewal following drought periods is often associated with improved limnological conditions—such as increased transparency and reduced turbidity—this effect is not always guaranteed. Therefore, this study aims to evaluate the dynamics of limnological variables in a tropical semi-arid reservoir during the dry and rainy seasons, comparing the epilimnion and hypolimnion layers. Monthly water sampling was conducted during two contrasting periods: Period I (dry season, from July 2023 to March 2024) and Period II (rainy season, from March to June 2024) in the Gargalheiras Reservoir. Parameters related to eutrophication were analyzed. A reduction in electrical conductivity values was observed in the period following water renewal, while fixed and volatile suspended solids did not show significant differences. However, the similarity in variables such as pH, dissolved oxygen, chlorophyll-a, Secchi transparency, and water temperature, combined with increased turbidity, suggests that the lack of control over external and internal nutrient inputs—due to the absence of watershed and sediment management—contributed to the worsening of water eutrophication.