Development of a Satellite-Based Algorithm for Groundwater and Drought Impact Assessment in Doñana Wetlands: A Decision-Support Tool for Ecosystem Conservation

The Doñana wetlands, a vital ecological reserve in southern Europe, are experiencing accelerated hydrological degradation due to climate change and increasing anthropogenic pressure. This study introduces the Water Inference Moisture Index (WIMI), a spectral index developed to assess surface water dynamics using Sentinel-2 L2A imagery from 2016 to 2024. The index combines near-infrared (B08) and red (B04) bands to detect wetland water presence with high sensitivity, even under dense vegetation cover. By integrating WIMI with long-term precipitation records and climate data, we analyzed spatial and temporal trends in water availability. Results reveal a progressive decline in surface water across the study area, even in years with average rainfall, suggesting structural changes in water retention capacity and increased groundwater stress. Annual WIMI values were moderately correlated with rainfall but exhibited increasing divergence in recent years. Comparison with projections from the IPCC Sixth Assessment Report reinforces the local expression of broader climate-induced aridification trends. The study demonstrates WIMI’s utility as a low-cost, scalable monitoring tool to support wetland conservation and climate adaptation strategies. The findings advocate for urgent policy measures to safeguard groundwater resources and align with the Sustainable Development Goals related to water security and climate action.