ND Watershed Boundary Dataset
The Watershed Boundary Dataset, or WBD, is part of the hydrography framework data for the nation. The WBD defines the perimeters of surface water drainage areas, or hydrologic units, formed by the terrain and other landscape characteristics. A hydrologic unit (HU) is delineated by hydrologists based on topography and surface water drainage, not political or administrative boundaries.
Drainage areas of the WBD are delineated to nest in a multi-level, hierarchical arrangement. At a minimum, the WBD is being delineated to U.S. Geological Survey 1:24,000-scale topographic maps. These data were created using the same set of hydrologic unit delineation standards across the entire country thereby creating a base-line drainage framework for the entire United States.
HUCs and the WBD?
Hydrologic units are given a Hydrologic Unit Code (HUC). A HUC describes where the unit is in the country and the level of the unit. For example, a hydrologic region has a 2-digit HUC. The number of digits in the HUC reflect the "level".
The WBD that is distributed on the ND GIS Hub Data Portal is a subset of the nationwide WBD; it contains only those regions (HU2), subregions (HU4), basins (HU6), subbasins (HU8), watersheds (HU10) and subwatersheds (HU12), and subwatershed lines (HU12 Line only) that touch the borders of North Dakota.