Global Streamflow Seasonality Responses to Vegetation Phenology Shifts Across Diverse Hydroclimatic Regimes

Vegetation phenology has shifted globally over recent decades, yet its influence on streamflow seasonality remains insufficiently quantified. Here we present a global, catchment-scale assessment of streamflow seasonal responses to vegetation phenology changes using long‐term observations from ~3000 river basins spanning diverse hydroclimatic regimes. Our results reveal that where vegetation phenology advances, streamflow is systematically redistributed within the year, characterized by reduced spring and summer discharge and enhanced winter streamflow, reflecting increased growing-season water consumption by vegetation. In addition, streamflow timing responds coherently to phenological shifts, advancing in concert with earlier vegetation activity, with particularly pronounced responses in cold regions. In these regions, early-season streamflow timing exhibits a significant advancement driven jointly by earlier snowmelt and vegetation green-up, indicating a dual forcing that amplifies the sensitivity of runoff timing to phenological change in snow-affected catchments. Furthermore, phenological advancement is associated with a weakening of streamflow seasonality, primarily resulting from decreased summer flows and increased spring flows, thereby reducing intra-annual runoff variability.