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Overview
This dataset is a digital hydrologic unit boundary layer that is at the Subwatershed (12-digit) level. The layer also includes delineations at the Watershed (10-digit) and Subbasin (8-digit) levels. Each basin is identified by a unique Hydrologic Unit Code (HUC), as well a name, at each level. HUCs are identifiers as assigned to basin polygons by the U.S. Geological Survey (USGS).
Data in this layer cover all of Massachusetts and small parts of surrounding states. The names of the statewide datalayers are NRCSHUC_POLY (polygons), NRCSHUC_ARC (arcs), and NRCSHUC_ANNO (annotation).
The HUC is a hierarchical, numeric code that uniquely identifies hydrologic units. Hydrologic units are subdivisions of watersheds nested from largest to smallest areas and are used to organize hydrologic data.
HUCs are constructed as follows:
- the first two digits identify the region,
- the first four digits identify subregions,
- the first six digits identify accounting units,
- the first eight digits identify cataloging units,
- the first ten digits identify watershed units,
- and the full twelve digits identify subwatershed units. The USGS has developed the first 8-digit HUC for the United States, while the U.S. Department of Agriculture, Natural Resource Conservation Service (USDA-NRCS) within each state is developing the full 12-digit HUC.
Production
The original data set was developed by the USDA-NRCS, by delineating the boundary lines on base USGS 1:24,000 scale topographic quadrangle maps, and digitizing the delineated lines. Digital Raster Graphics (DRG) images were used for edits to the data layer. The dataset produced by the joint NRCS-USGS effort to develop the 12-digit national standard is known as the Watershed Boundary Datalayer (WBD).
For ease of use and purposes of symbology and labeling, MassGIS dissolved the full polygon layer into three additional layers. Each contains features delineated at one of the three HUC levels: NRCSHUC10_POLY, NRCSHUC12_POLY and NRCSHUC8_POLY.
Attributes
The polygon attribute table for NRCSHUC_POLY has the following fields:
| Field Name | Description |
| HUC_8 | 8-digit HUC |
| HU_8_STATE | HUC 8 State: CT = Connecticut MA = Massachusetts NH = New Hampshire NY = New York RI = Rhode Island VT = Vermont |
| HU_8_DS | Downstream HUC Subbasin Level 4 (8-digit) |
| HU_8_NAME | HUC 8 Basin Name |
| HU_8_MOD | Hydrologic Unit Modifications Subbasin Level 4 (8-digit) (Not coded) |
| HU_8_TYPE | Hydrologic Unit Type Subbasin Level 4 (8-digit) (Not coded) |
| HUC_10 | 10-digit HUC |
| HU_10_STAT | HUC 10 State (same values as HU_8_STATE) |
| HU_10_DS | Downstream Hydrologic Unit Code Watershed Level 5 (10-digit) |
| HU_10_NAME | HUC 10 Basin Name |
| HU_10_MOD | Hydrologic Unit Modifications WATERSHED Level 5 (10-digit): BC = Barge Canal DM = Dam at outlet or HU boundary IT = Interbasin Transfer NM = No Modifications PD = Pipe Diversion |
| HU_10_TYPE | Hydrologic Unit Type Watershed Level 5 (10-digit): F = Frontal hydrologic unit S = Standard hydrologic unit |
| HUC_12 | 12-digit HUC |
| ACRES | Area of polygon in acres |
| HU_12_STAT | HUC 12 State (same values as HU_8_STATE) |
| HU_12_NCON | |
| HU_12_DS | Downstream Hydrologic Unit Code Subwatershed Level 6 (12-digit) |
| HU_12_NAME | HUC 12 Basin Name |
| HU_12_MOD | Hydrologic Unit Modifications Subwatershed Level 6 (12-digit) (same values as HU_10_MOD) |
| HU_12_TYPE | Hydrologic Unit Type Subwatershed Level 6 (12-digit): F = Frontal hydrologic unit S = Standard hydrologic unit W = Water hydrologic unit |
| FIPS_C | County codes |
Each of the three polygon layers delineated at the individual HUC levels contain only the fields relevant for its level.
In the arc attribute table, the field OUTLINE is coded as follows:
| Field Name | Description | ||||||||
| OUTLINE | Boundary type:
|
Maintenance
MassGIS maintains the layer, although no updates are planned.
For other watershed data, see these layers:
- Major Watersheds (similar to 8-digit HUCs)
- Major Drainage Basins (similar to 8-digit HUCs)
- Drainage Sub-basins (more delineated than the 12-digit HUCs)
- Mega Basins (4-digit HUC delineations)
| Date published: | November 1, 2005 |
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| Last updated: | November 1, 2005 |