Influência da vazão afluente do rio de Contas sobre a qualidade da água do Reservatório Pedra, estado da Bahia, Brasil

Abstract

Variations in water physical and chemical characteristics are more frequent in reservoirs located in semi-arid regions where rainfall is seasonal, as the Pedra reservoir. This study evaluated the influence of multi-annual inflow of the Contas River on limnological variables of Pedra reservoir and its relation with reservoir´s water level. Quarterly samples were taken in eleven stations between 2005 and 2007, during the wet and dry seasons and significant differences were analyzed using the Kruskal-Wallis test for variables (pH, conductivity, dissolved oxygen, temperature, euphotic zone, nitrate, nitrite, turbidity, inorganic phosphate, total phosphate, total phosphorus, water level, rainfall and inflow). All variables showed significant differences (p <0.05), with the exception of nitrite, turbidity, and inorganic phosphate. A principal component analysis (PCA) was performed for each month, including data for the three years. Nutrients´ concentrations showed higher values, when water level presented lower values. The PCA showed that variables presented no similar seasonal pattern, but formed distinct monthly clusters for each year, with different determining variables, such as nutrients in 2005, euphotic zone, pH and conductivity in 2006, and water level, rainfall and inflow in 2007.