WATER QUALITY ASSESSMENT IN RELATION TO THE SURROUNDING SOIL MANAGEMENT OF TWO RESERVOIRS IN PINDORAMA/SP - A PRELIMINARY STUDY.

Soil management techniques applied by industrial farming have a profound impact on neighboring bodies of water, posing a threat to their aquatic biota. Therefore, water quality monitoring is essential to pinpoint areas of risk and propose remediation strategies. This preliminary study combined analysis of water quality physicochemical parameters and a trophic state index based on phosphorus concentration to characterize and compare two reservoirs in Pindorama/SP located in areas of distinct agricultural land management. Analyses showed that both reservoirs had total phosphorus concentrations above the federal threshold. It was then hypothesized that the excess of this nutrient was caused by the runoff of agricultural products from the surrounding area as no point sources of pollution were found. The first reservoir had a high density of floating macrophytes, which virtually covered the water surface, and was characterized as in a eutrophic state. The second reservoir, with lower macrophyte density and lower phosphorus levels, was characterized as in a mesotrophic state. These results evidenced that the overpopulation of macrophytes in the first reservoir may be a consequence of the eutrophication process. Furthermore, the presence of a more consolidated riparian forest which decreases the impacts of runoff in the second reservoir may explain its lower phosphorus levels. Finally, despite low turbidity, oxidation-reduction potential values in both reservoirs indicated low oxygen intake. The results demonstrate that these ecosystems are at risk of deterioration, thus strategies to improve the surrounding soil management and increase water circulation must be implemented. [ABSTRACT FROM AUTHOR]