Geotechnologies in the Assessment of Eutrophication in the Barra Bonita Reservoir, São Paulo, Brazil

Abstract

Objective: The objective of this study was to identify locations with higher eutrophication and, consequently, susceptible to the emergence of macrophytes in the Barra Bonita reservoir, SP. Theoretical background: The presence of macrophytes, such as Eichhornia crassipes, is influenced by ecological succession driven by human activities like introducing exotic species and discharging untreated nutrients. Effective management, including buffer zones, is suggested to reduce eutrophication, though some studies question their effectiveness on a large scale. Method: The analysis of the Normalized Difference Vegetation Index (NDVI) was conducted using remote sensing images obtained from Landsat 8 and 9 satellites. As a criterion for data acquisition, corresponding data for the study region were obtained over a one-year temporal scale with a maximum cloud cover of 0%. Results and conclusion: Analyzing the images, it is observable that the month of June 2023 exhibited areas with a higher vegetation index and, consequently, eutrophication processes. This trend gradually decreased in the months of August, September, and November. Research implications: The analysis of satellite images revealed specific patterns of eutrophication, suggesting a direct correlation between the geographical distribution of nutrients and the potential proliferation of macrophytes. Additionally, comparative studies of nutrient concentrations in tributaries indicate that urban pollution, besides affecting local water quality, contributed to eutrophication in the Barra Bonita reservoir. Originality/value: Through the NDVI, the eutrophication possibility in Barra Bonita’s Reservoir was evidentiated.