Water Surface Extent and Chlorophyll Dynamics in Pantanal Wetland based on Sentinel-2 Data

Pantanal Wetland is under threat by anthropogenic activities and the ongoing climate crisis. While many studies have addressed changes in water quantity in the region, it has been little discussion on how water quality can be affected. This study aimed to investigate the relationship between water surface extent (WSE) and chlorophyll dynamics in the Lake Uberaba, the largest lake in Pantanal. We used Sentinel-2 images to determine the WSE using several water indices and thresholds defined by Otsu method. Chlorophyll-a levels were estimated using the normalized chlorophyll water index (NDCI). We generated time series of WSE and NDCI and analyzed them using the Seasonal and Trend decomposition using the STL method. In general, the thresholding method presented satisfactory results; the automated water extraction index with shadow (AWEI_sh) had the best performance in identifying WSE dynamics. WSE presented a significant decreasing trend, and it has an inverse relationship with NDCI.