Watershed Boundary Dataset

Source: http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/index.html

The newly released Natural Resources Conservation Service Hydrologic Unit Code (HUC) 12-digit Watershed Boundary Dataset (WBD) provides one of the fundamental frameworks upon which analysis and reporting of WATERS programs takes place.
 

The older 8-digit Watershed Boundary Dataset is now referred to as the "legacy" WBD for clarity.  To allow for migration activities the legacy WBD is also stored in WATERS.

Many WBD layers are provided as mapping services.  See WATERS mapping services for more information.

NRCS Watershed Boundary Datasets:

• WBD_HUC12
  12-digit subwatershed region polygons as released by Natural Resources Conservation Service.
  
  
• WBD_HUC10
  WBD_HUC10_GEN
  10-digit watershed subregion polygons aggregated by Hydrologic Unit Code.
  
  
• WBD_HUC8
  WBD_HUC8_GEN
  8-digit subbasin polygons aggregated by Hydrologic Unit Code.
  
  
• WBD_HUC6
  WBD_HUC6_GEN
  6-digit basin polygons aggregated by Hydrologic Unit Code.
  
  
• WBD_HUC4
  WBD_HUC4_GEN
  4-digit subregion polygons aggregated by Hydrologic Unit Code.
  
  
• WBD_HUC2
  WBD_HUC2_GEN
  2-digit region polygons aggregated by Hydrologic Unit Code.
  

Legacy Watershed Boundary Datasets:

• LEGACYWBD_HUC8
  LEGACYWBD_HUC8_GEN
  8-digit legacy subbasin polygons.  Generalized layer features point removal to about 75 meters.
   
• LEGACYWBD_HUC6
  LEGACYWBD_HUC6_GEN
  6-digit legacy basin polygons.  Generalized layer features point removal to about 75 meters.
   
• LEGACYWBD_HUC4
  LEGACYWBD_HUC4_GEN
  4-digit legacy subregion polygons.  Generalized layer features point removal to about 75 meters.
   
• LEGACYWBD_HUC2
  LEGACYWBD_HUC2_GEN
  2-digit legacy region polygons.  Generalized layer features point removal to about 75 meters.

Storage Details for WBD Layers

• WBD tables are stored in the waters_wbd schema with all tables publically accessible to internal users at EPA.
  
  
• WBD tables are stored in the same coordinate space (NAD83) as RAD and NHD layers.
  
  
• WBD tables are registered to ArcSDE allowing use by any internal EPA ESRI client.
  
  
• NRCS WBD tables are named indicating the vintage of the data (i.e. WBD20090316_HUC12_OS). To account for future updates to the WBD, each table has a spatial view with no vintage information in the name (i.e. WBD_HUC12_OS). The view should be used when hard-coding tablenames in services and procedures. By using the generic view name, the developer can be assured that they will pull the most recent information available in the WATERS instance.  No such naming scheme is required for legacy WBD datasets.
  
  
• All views of the WBD layers are ArcSDE registered spatial views.