Continental-Scale Increases in Betweenness and Modularity in European River Networks: a 30-Basin Analysis from 1992 to 2024

This study investigates hydrological network reorganization across 30 European river basins from 1992 to 2024 using dynamic flow-weighted graph representations. The objective is to determine whether graph-based diagnostics can reveal long-term structural changes in river-basin organization that are not evident from discharge trends alone. Approximately 400 GB of 6-hourly discharge data were mapped onto a fixed river topology, and eight network metrics were computed. Nonlinear dynamical diagnostics were used to identify metric-specific temporal scales for variability analysis. Although discharge exhibits no consistent continent-scale trend, mean edge betweenness and modularity increase significantly after BH–FDR correction, indicating growing dependence on dominant flow corridors and stronger mesoscale compartmentalization. The remaining network descriptors do not retain statistically robust continent-scale level trends, although significant responses occur in selected individual basins. These results demonstrate that flow-weighted network metrics provide complementary indicators of hydrological change beyond discharge magnitude alone, offering a new framework for continental-scale river-basin monitoring and assessment.