Global change is altering river basins and their discharge worldwide. We introduce the land–atmosphere reservoir (LAR) concept to investigate these changes in six of the world's largest basins. We found that low-latitude basins (Amazon, Paraná, and Congo) are getting wetter, whereas high-latitude basins (Mississippi, Ob, and Yenisei) are drying. If this continues, these long-term trends will disrupt the discharge regime and compromise the sustainability of these basins with widespread impacts.