Proposta de delimitação da bacia hidrográfica do igarapé Carrapato e seu significado para a gestão hídrica

Abstract

Accurate watershed delineation is fundamental for effective water resources management, as it enables a comprehensive understanding of fluvial dynamics, water availability, and the interactions between surface and groundwater systems. In this context, this study focuses on improving the delineation of the Carrapato Stream Watershed (BHIC), located in the municipality of Boa Vista, Roraima State, Brazil, in response to increasing anthropogenic pressure associated with urban expansion and agro-pastoral activities, aligning with the Sustainable Development Goals (SDGs) 3, 6, and 11. The main objective was to delineate the BHIC through the integration of satellite- and drone-based remote sensing techniques, Digital Elevation Models (DEMs), and geospatial data, with emphasis on analyzing surface and groundwater dynamics and evaluating their applicability to water resources management. The methodologywasbasedonastepwiseapproachintegratingmultipleDEMs(FABDEM, COP 30, SRTM, ALOS PALSAR, NASADEM, and ANADEM), drone-derived orthomosaics, field-based altimetric validation, multitemporal optical image analysis, geoprocessing techniques, hydrogeological interpolation, application of spectral indices (NDVI, SAVI, NDWI, and MNDWI), and analysis of data from the SIGGAR and SIAGAS databases. The results demonstrated that DEM selection has a decisive influence on the accuracy of watershed delineation, with higher-resolution and hydrologically corrected models providing representations more consistent with actual topographic features, whereas more generalized models led to the inclusion of areas without effective drainage contribution. The final watershed area was estimated at 109.372 km², with elevations ranging from 54 to 120 m. Environmental analysis revealed the occurrence of 12 fire hotspots between 2016 and 2024, including five in 2016, one in 2022, and six in 2024, with no direct occurrences within the watershed in 2018 and 2020, indicating improvements in fire control. Burned area scars mapped between 2016 and 2023 totaled 32.333 km² according to DETER and 20.602 km² according to SIGGAR, corresponding to 29.56% and 18.84% of the watershed area, respectively, without evidence of significant impacts on hydrological balance. From a hydrogeological perspective, the groundwater depth map indicated variations between 0 m and +2.10 m, evidencing high aquifer vulnerability. Potentiometric levels ranged from 63.66 to 87.83 m during the dry season and from 62.00 to 90.50 m during the rainy season, with predominant groundwater flow from north to south, delineating recharge zones in the northern sector and discharge zones in the southern sector. Regarding water use, SIGGARidentified 249 groundwater abstractions and 39 surface water withdrawals, while SIAGAS registered 64 wells associated with multiple uses, highlighting limitations in monitoring and data integration. The integration of surface, subsurface, and environmental data resulted in a robust and replicable technical framework capable of supporting territorial planning and strengthening integrated water resources management in the BHIC.