National Hydrography Dataset & Watershed Boundary Dataset in Idaho


The Idaho Department of Water Resources (IDWR) and Natural Resource Conservation Service (NRCS), in cooperation with various state and local agencies produced the statewide Watershed Boundary Dataset (WBD) for 5th and 6th field watersheds for the State of Idaho. Idaho received a Full Certification status for the WBD effort in Idaho on December 2, 2008. Thank you to all cooperators, data stewards and interested parties who helped in this endeavor!


If you would like to download WBD data, please visit the USDA Natural Resources Geospatial Data Gateway and request your area(s) of interest. Click here to visit the NRCS WBD page.


WBD/NHD Integration

The National Hydrography Dataset (NHD) and Watershed Boundary Dataset (WBD) have been integrated into a common data model, and the new WBD boundaries are packaged with the NHD subbasins as they are checked out and downloaded. New editing tools for both NHD and WBD are currently being developed and tested.


Future Updates

Updates to the WBD are now in the maintenance phase. Revisions may be required to incorporate corrections within the state or along the international border in order to further harmonize the data and create a seamless dataset across boundaries. Work is underway to develop standards for incorporating 14 and 16-digit delineations into the WBD.


History

The Idaho 4th, 5th and 6th field level boundaries were created using the “USGS Interagency Guideline on Delineation of Watershed and Subwatershed Hydrologic Unit Boundaries” standards, version dated October 4, 2004. Each Subbasin, formerly known as a “HU” (hydrologic unit) was assigned a data steward at the 4th field (8-digit) level, based on land ownership, management, and interest for each area. Data stewards reviewed their areas and coordinated with other interested cooperators and surrounding states to create new draft fourth, fifth, and sixth field watershed lines. Statewide 24k Digital Raster Graphics (DRG) and hydrography data was utilized, along with Shaded Relief and NAIP aerial photography to help determine boundary lines. Polygons were attributed with new names and nesting watershed numbers pursuant to the watershed standards:


Hydrological Unit Boundary Delineation Process Used in Idaho

Hydrologic Unit Level Name Coding Digits Size (in acres) Number
1 Region 2    
2 Sub-region 4    
3 Basin 6    
4 Sub-basin 8 250,000 - 450,000  
5 Watershed 10 40,000 - 250,000 5 to 15
6 Sub-watershed 12 10,000 - 40,000 5 to 15


A WBD Technical Working Group was formed, and members of the TWG, in cooperation with various federal, state and local agencies participated in monthly TWG meetings to review and update subbasin delineations during each day-long session. After each session, edits were collected and sent out for further review to all interested parties, which included coordination and edge-matching with surrounding states. As a result of this process, new 4th, 5th and 6th field watershed boundaries were created at 1:24,000, utilizing local expertise to more accurately depict drainage patterns throughout the state. After all subbasins had been reviewed, a statewide dataset was assembled and put out for a last final review before being submitted for final certification consideration. Certification in Idaho was obtained on December 2, 2008.

Contact Information:

Genna Ashley
Idaho NHD Technical Point of Contact
Phone: (208) 287-4880

Linda Davis
Idaho NHD Principal Steward
Phone: (208) 287-4877

Idaho Department of Water Resources
322 East Front Street
PO Box 83720
Boise, Idaho 83720-0098

For a list of contacts for neighboring states, as well as a list of contacts for specific regions or hydrologic units, please email Genna Ashley.

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