Monitoramento hidrológico e sensoriamento remoto em estuários amazônicos: análise da variação espacial e temporal de sedimentos.

Abstract

Monitoring aquatic environments generally requires high technical, scientific and financial investment. The existence of dedicated monitoring networks is necessary to guarantee spatial and temporal continuity. However, data quality also depends on standardization, from sample collection to parameter analysis. Studies show that the biggest challenge in Brazil is the scarcity of financial resources, resulting in data discontinuity. Inter-institutional cooperation is essential to overcome these obstacles and promote long-term monitoring. In this context, remote sensing has emerged as a fundamental auxiliary tool, complementing traditional monitoring by providing data on various aquatic variables, such as height, temperature and concentration of optically active components, especially in conditions of restricted financial resources or governance problems. Spatio-temporal variations in water color in an estuary are affected by various physical and hydrological components, which makes understanding them complex. In this study, we sought to understand the spatio-temporal variation of water color, for sampling purposes, in an estuary on the Amazon Coast. The study area for this study is located in the estuary formed by the confluence of the Pará (Tocantins, 5% of the Amazon River), Guamá and Acará rivers, near the island of Tatuoca, 10 km from Belém. The region is influenced by the Marajó and Santo Antônio bays, which have different bottom morphologies, affecting local currents. The climate has two seasons: rainy (December to May) and less rainy (June to November). The tides are meso and macro semidiurnal, with amplitudes of up to 3.7m. To achieve our objectives, we applied geostatistical and statistical tools to test the spatio-temporal variability of water color, based on multisensor reflectance data, Landsat-8/9 and Sentinel-2 in the red band. The spatial variation showed distances of more than 48 m ±4.26 at high tide and 44 m ±7.62 at low tide. For the temporal variation, we found that the monthly variations are significant according to seasonality and show the same variation in the different phases of the tide (high, low and equinoctial). Therefore, the color of the water in the Tatuoca Island region shows geostatistical and statistically significant spatio-temporal variation. The distances and temporal frequency of sampling should be adjusted according to the tides and seasonality to ensure that the data is sampled according to the variations in the environment.