In recent years, climate change has significantly impacted European river systems, reshaping streamflow patterns with far-reaching consequences for ecosystems and water resources. This study investigates hydrological variability across 16 major European rivers. Cross-correlation analysis reveals strong climatic influences, with the Danube showing robust positive correlations with rivers such as the Elbe, Oder, Rhine, and Vistula, suggesting shared climatic drivers. In contrast, negative correlations between Central European rivers, like the Danube and Drava, and Southern European and UK rivers highlight the influence of distinct climatic regimes and geographical factors. To assess trends and identify abrupt changes in streamflow, the study applies the Mann-Kendall (MK), Seasonal Kendall (SK), and Regional Kendall (RK) tests, along with the Bayesian Estimator of Abrupt Change, Seasonal Change, and Trend (BEAST) algorithm. Hierarchical clustering analysis identifies four distinct groups: one cluster dominated by a strong negative trend in the Ebro River, another with a positive trend in the Thames, and two additional clusters representing Eastern and Western European rivers, with a few exceptions. The findings from the MK and SK tests reveal declining trends in rivers such as the Danube, Drava, and Nemunas, likely driven by long-term climatic shifts. In contrast, the Thames exhibits significant increases in streamflow, likely reflecting unique climatic conditions in Southern UK. The RK test further corroborates these observations, showing an overall pattern of declining streamflow across the studied rivers. BEAST analysis uncovers historical variability by identifying important transitions on long-term trends and abrupt changes in streamflow. Rivers like Danube, Loire, Drava, Nemunas and Vistula transitioned from positive to negative trends starting in the 1970s to 1990s. BEAST reveals also more complex dynamics in rivers like Rio Ebro and Thames, where both upward and downward abrupt changes reflect the impact of extreme weather events. [ABSTRACT FROM AUTHOR]