Vegetation Response to Interannual Precipitation Variability in High-Andean Wetlands of Central Chile Using Sentinel-2, ERA5-Land, and UAV Imagery

Difficult access and a lack of in situ data limit monitoring of high-Andean wetlands, which are key components of water regulation in central Chile. This study analyzes the multitemporal dynamics of vegetation in three high Andean wetlands of the headwater (1HW), lateral (2LW), and confluence (3CW) types in the Los Nogales Nature Sanctuary between 2018 and 2025. We integrated Sentinel-2 Level 2A images, annual accumulated precipitation from the ERA5-Land product (lag-1 year), and high-resolution UAV-derived boundaries to characterize six spectral indices (NDVI, EVI, NDRE704, NDRE705, NDWI, and SAVI) and their relationship with water variability. Annual precipitation ranged from ~420 to 780 mm during a regional megadrought. The headwater wetland showed the greatest climate sensitivity, with significant correlations between the previous year's precipitation and NDVI, NDRE705, EVI, SAVI, and NDWI (|R| ≥ 0.70; p < 0.05), while in the lateral and confluence wetlands, the relationships were moderate or weak. Multitemporal mosaics showed maximum vegetative vigor between 2018 and 2021, followed by a decline. Overall, the results confirm that integrating the Sentinel-2 series, climate reanalysis, and UAV delimitation is an effective tool for ecohydrological monitoring and management of high-Andean wetlands.