Variação nictemeral da qualidade da água em um espelho d’ água de captação pluvial

Abstract

Nycthemeral Variation of Water Quality in a Rainwater Harvesting Reservoir: The construction of reservoirs to collect rainwater can be an effective alternative, especially in urban areas, as they allow for the storage and conservation of water for varying periods, depending on use and evaporation rate. Therefore, this study aims to evaluate the water quality of a newly constructed rainwater harvesting reservoir during its variation throughout the nycthemeral cycle, considering physical, chemical, and biological parameters. Four samples were collected during the summer at two points in the reservoir on a weekly basis. The physical and chemical analyses of the water were compared with the values ​​recommended by CONAMA Resolution 357/05 for Class II freshwater. During the period, aquatic invertebrates were collected from the reservoir banks, with these collections occurring weekly, but only at one time of day. Invertebrates were classified using the BMWP (Biological Monitoring Working Party), which assigns weights to each family according to their tolerance and sensitivity to pollution. The results indicated that pH, dissolved oxygen, and phosphorus showed discrepancies with the values ​​of CONAMA Resolution 357/05 in at least one of the samples. Nitrite levels were high in all samples; however, ammonia remained within permitted limits. Temperature remained high during the monitoring period, especially in shallow lakes in open areas. The BMWP index indicated water quality of "very critical," "critical," and "doubtful." Thus, the results show that the morphology of the environment exerts a significant influence on water quality, since it is a recently altered environment with little structure and in a phase of formation.