Legend (Reference/Columbia_River_HydroUnits)

Columbia River Basin Boundary (0) Columbia River - Subregions (level 2 HUCs) (1) Columbia River - Basins (level 3 HUCs) (2) Columbia River - Subbasins (level 4 HUCs) (3) Columbia River - Watersheds (level 5 HUCs) (4) Columbia River - Subwatersheds (level 6 HUCs) (5)