Multi-Indicator Assessment of Hydrological Change Across Europe Using Satellite Observations

Understanding drought and water availability requires integrating multiple components of the hydrological cycle. Satellite observations enable consistent monitoring of water storage, groundwater variability, and water budget components at continental scales. This study synthesises results from several satellite-based analyses to examine hydrological signals across Europe within the Köppen–Geiger climate zones. Indicators were analysed jointly, including the Combined Climatologic Deviation Index (CCDI), Water Budget (WB), Water Storage Deficit Index (WSDI), and Groundwater Drought Index (GDI). The comparison of these indices reveals consistent spatial and temporal patterns of water deficit across Europe, with the strongest drying signals observed in temperate and Mediterranean regions. In contrast, northern climatic zones show higher retention capacity. The integrated approach highlights relationships among groundwater variability, water storage anomalies, climate anomalies, and water budget dynamics, providing a broader perspective on hydrological responses to climate variability. The results demonstrate the value of multi-indicator satellite analysis for large-scale drought monitoring and water resource assessment.