Watershed Boundary Dataset

The Watershed Boundary Dataset (WBD) is a seamless, national hydrologic unit dataset. Hydrologic units represent the area of the landscape that drains to a portion of the stream network. More specifically, a hydrologic unit defines the areal extent of surface water drainage to an outlet point on a dendritic stream network or to multiple outlet points where the stream network is not dendritic. A hydrologic unit may represent all or only part of the total drainage area to an outlet point so that multiple hydrologic units may be required to define the entire drainage area at a given outlet. Hydrologic unit boundaries in the WBD are determined based on topographic, hydrologic, and other relevant landscape characteristics without regard for administrative, political, or jurisdictional boundaries. The WBD seamlessly represents hydrologic units at six required and two optional hierarchical levels.

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The hydrologic units (HU) in the WBD form a standardized system for organizing, collecting, managing, and reporting hydrologic information for the nation. The HUs in the WBD are arranged in a nested, hierarchical system with each HU in the system identified using a unique code. Hydrologic unit codes (HUC) are developed using a progressive two-digit system where each successively smaller areal unit is identified by adding two digits to the identifying code the smaller unit is nested within. WBD contains eight levels of progressive hydrologic units identified by unique 2- to 16-digit codes. The dataset is complete for the United States to the 12-digit hydrologic unit. The 14- and 16-digit hydrologic units are optional and are not complete for the nation. Efforts to complete the 10- and 12-digit unit delineations within 8-digit hydrologic units extending across the U.S. – Canada border are complete. Additional information about this effort and access to data is linked on the “resources” section on this page. A similar effort is complete for the 10- and 12-digit units extending across the U.S. – Mexico border.

The WBD team is pleased to announce the publication of the authoritative WBD snapshot. This snapshot of the WBD includes various edits and improvements to the attribution and geometry of the WBD and captures any outstanding WBD user edits that were incorporated into the national dataset in the past fiscal year. This snapshot of the WBD dataset should be referenced as the authoritative snapshot of the dataset while the program shifts focus to the new 3DHP data model and can be downloaded here.

Please relay any questions to Kimberly Jones (kjones@usgs.gov) and Lily Niknami (lniknami@usgs.gov).