Selected Northern Hemisphere Basins Information

We first compiled 4, 767 catchments with minimal anthropogenic influence from previous studies, exhibiting mean irrigation areas of 0.33 ± 0.60% (mean ± SD), reservoir areas of 0.13 ± 0.52%, and urban areas of 0.15 ± 0.41%, then we mapped them to their corresponding HydroBASINS Level-08 polygons and identified their parent Level-07 basins (1,038 in total), encompassing 10,656 individual Level-08 polygons. To further focus on snow-dominated systems, we retained basins with a mean ratio R of water-year cumulative snowfall to runoff (ERA5-Land) exceeding 0.5. Consequently, the resulting 1,018 snow-affected basins (Level-07) across the Northern Hemisphere.