 This study examined streamflow trends in 441 small catchments in 15 European countries over a period of 42 years. It found that overall, streamflow has been declining in southern and eastern regions, while it has been increasing in other areas. Additionally, the study identified a shift towards negative trends in April, gradually spreading across Europe to reach a maximum extent in August. Low flows have decreased in most regions where the lowest mean monthly flow occurs in summer, but they vary for catchments which have flow minima in winter and secondary low flows in summer. These patterns are consistent with projections from climate models, suggesting that this data can be used as a benchmark for various studies and model simulations. This article was authored by K. Stahl, H. Hisdahl, J. Hannaford, and others.