Past and future change in global river flows

Rivers are a vital component of the global water cycle, and human influence on the climate and terrestrial systems is increasingly shaping their flow regimes. This review summarises the current understanding of past and projected changes in global river flow, focusing on annual volumes, seasonal dynamics and sudden changes. Observations reveal distinct regional trends, including increased flows in high-latitude regions and decreased flows in parts the mid-latitudes and subtropics. Especially snow dominated regions, also show shifts in their seasonal cycle towards earlier flows. These patterns align broadly with historical climate model simulations, suggesting an anthropogenic climate change signal. However, attribution is complicated by the interplay of greenhouse gas emissions, CO₂-driven vegetation response, land use change and water management. Future projections indicate continued change, with some regions experiencing wetter conditions and others intensified drying. Seasonal changes, particularly those due to altered snow dynamics, are also expected to intensify. Despite modelling and observational advances, uncertainties regarding the combined effects of anthropogenic climate change and direct human interventions in terrestrial systems remain. Closing these gaps requires improved monitoring, advances in modelling and robust attribution frameworks, in support of efficiently managing water resources, sustaining ecosystems, and adapting to a changing climate.