Satellite altimetry reveals a contrasting wetting-drying pattern in global rivers under climate change

River water levels and their dynamics are fundamental indicators of freshwater availability, climate change impacts on the water cycle, and regional water security. Although monitoring these changes is crucial for developing adaptive management strategies that balance human needs with ecosystem sustainability, traditional in-situ observations are mostly constrained to large rivers and downstream reaches. Satellite altimetry, using radar pulses to sense surface waters, open a new era to track global river stages and assess their temporal variations. Leveraging advanced Synthetic Aperture Radar techniques and our improved waveform retracking algorithm, we successfully monitored water levels at 46,993 Sentinel-3 virtual stations (VSs) from 2016 to 2024. These VSs, located at the intersections of satellite ground tracks and river channels, encompass rivers ranging from several meters to kilometers in width across diverse topographical settings. Water level change rates unveil a pronounced global wetting-drying pattern across river basins. Our analysis identifies significant water level declines in Central North America, Central South America, and Western Siberia, contrasting with widespread increases across Africa, Oceania, and Eastern and Southern Asia. These findings demonstrate the differential impact of intensifying hydrometeorological events on regional river dynamics and highlight accelerating change rates. Our results provide critical insights into water security assessment and resilience planning, emphasizing the urgent need for targeted policy interventions to address these hydrological changes.