U.S. Fish & Wildlife ServiceEach drainage area is considered a Hydrologic Unit (HU) and is given a Hydrologic Unit Code (HUC) which serves as the unique identifier for the area. Hydrologic Units are delineated to nest in a multi-level, hierarchical drainage system with corresponding HUCs, so that as you move from small scale to large scale the HUC digits increase in increments of two. For example, the very largest HUCs have 2 digits, and thus are referred to as HUC 2s, and the very smallest HUCs have 12 digits, and thus are referred to as HUC 12s. HUC 2s, 6s, 8s, 10s, & 12s, define the drainage Regions, Subregions, Basins, Subbasins, Watersheds and Subwatersheds, respectively, across the United States. Their boundaries are defined by hydrologic and topographic criteria that delineate an area of land upstream from a specific point on a river and are determined solely upon science based hydrologic principles, not favoring any administrative boundaries, special projects, or a particular program or agency. The Watershed Boundary Dataset is delineated and georeferenced to the USGS 1:24,000 scale topographic basemap. This feature class was built from the WBDHU10 dataset and slightly modified by adding additional fields to the attribute table that identify fish passage survey partners and their timelines within a particular HU10 watershed. The layer serves as a vital tool in fostering collaboration and communication among fish passage partners, aiming to enhance survey and conservation efforts. Dataset Summary Phenomenon Mapped : Watersheds in the United States, as delineated by the Watershed Boundary Dataset (WBD). Coordinate System : NAD83 Extent : Contiguous United States, Alaska, Hawaii, Puerto Rico, Guam, US Virgin Islands, Northern Marianas Islands and American Samoa. Visible Scale : Visible at all scales, however USGS recommends this dataset should not be used for scales of 1:24,000 or larger. Source : United States Geological Survey Publication Date : July 27, 2023ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/8f642d6c06e14657b163e3989edcaf95_0engU.S. Fish and Wildlife Service Open DataPublicWBDHU10 Partner Fish Passage Survey Priorities [United States]Web servicesUnited StatesLast Modified: 2025-12-04