Title: Water Boundary Data - 12 digit Hydrologic Units
Originator:
Abstract:
This dataset is a complete digital hydrologic unit
boundary layer to the sub-watershed (12-digit) 6th level at 1:24,000 scale.
This data set consists of geo-referenced digital data and associated attributes
created in accordance with the "FGDC Proposal, Version 1.0 - Federal
Standards For Delineation of Hydrologic Unit Boundaries 3/01/02 ( http://www.ftw.nrcs.usda.gov/huc_data.html
). The hydrologic unit boundaries
provide a uniquely identified and uniform method of subdividing large drainage
areas.
Polygons
are attributed with hydrologic unit codes, names, downstream hydrologic unit,
flow modifications, and hydrologic unit type for 4th level (8-digit)
sub-basin, 5th level (10-digit) watershed, 6th level
(12-digit) subwatershed, and acres for subwatershed. An accompanying line
shapefile is attributed with the highest hydrologic unit level for each
hydrologic unit, linesource, and a metadata reference file.
A text
document that is provided with the data called Watershed Boundary Dataset
(WBD) User Guide provides information on the methodology used to delineate
the hydrologic units and provides definition for all the attributes. The smaller sized 6th level sub-watersheds
(most within 10,000 to 40,000 acres) are useful for numerous application
programs supported by a variety of local, State, and Federal Agencies. This
data set is intended to be used as a tool for water-resource management and
planning activities, particularly for site-specific and localized studies
requiring a level of detail provided by large-scale map information.
Until the
entire nation is complete and HUC_8 codes are stable, the Geospatial Data
Gateway will only be serving two WBD layers; HU12 linework and HU12 polygons
(which consists of HUC_8, HUC_10, and HUC_12 codes, as well as HUC_10 and
HUC_12 names). If you would like to
derive HUC_2, HUC_4, HUC_6 codes and names or HUC_8 names, these values can be
dissolved from WBD HU12 then joined to the USGS layer (HUC250K) for naming
purposes. When ordering from the Gateway, the HUC250K USGS layer is listed as “8-Digit
Hydrologic Units 1:250,000”.
For instructions about how to derive HU2, HU4, HU6, or HU8
codes or names, see the following document:
ftp://ftp.ftw.nrcs.usda.gov/pub/wbd/hu_qa/wbdhu8.doc
For the progress in mapping HUC12 see the following status map:
ftp://ftp.ftw.nrcs.usda.gov/pub/wbd/status_maps/hucstatusstate.pdf
For additional information on WaterShed BOundary Dataset (WBD) see the following:
http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/index.html
Format: vector lines – Arc shapefile
Spatial Reference Information: Decimal Degrees, North American Datum 1983
