The increase in the urban population in the world has impacted river basins that supply water to cities, including the treatment and distribution of drinking water for domestic, industrial and commercial use. One example is the Bolonha and Água Preta Lakes Hydrographic Basin (BHLBA) in the Belém Metropolitan Region (RMB), the second largest urban agglomeration in the Brazilian Amazon, with 2.3 million inhabitants. One of the best
ways to monitor the dynamics of river basins is through remote sensing techniques with orbital images, due to the quality of the spatio-temporal data. This work aims to analyze the changes in land cover and use in the last four decades in the BHLBA, through images from the Landsat satellite series from the years 1984, 1989, 1994, 1999, 2004, 2008, 2018, 2021 and 2023, using a geographic object-oriented image analysis (GEOBIA) methodology. Thus, the classes of lakes (L), urban area (AU), aquatic macrophytes (MA), arboreal vegetation (VA) and pasture (P) were evaluated. The overall accuracy of the images showed values around 90%, with the main error being allocation errors. Changes that occurred over the years were identified, such as the significant growth of macrophytes on the water surface of the Bolonha and Água Preta lakes, which decreased by approximately 3.7%. A 13.4% increase in arboreal vegetation in the BHLHA was also recorded, evidencing a forest recomposition. A 3.2% growth in urban areas around the BHLBA was also observed, which is worrying because human influence can put the health of the water supply sources of the RMB at risk. The GEOBIA methodology proved to be adequate for the study and we recommend that monitoring be continued due to the socio environmental importance of the area under study.
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