This layer represents the eight mega-drainage basins for Massachusetts, aggregated from the Major Basins layer. The delineations were based on the level 2 (4-digit) Hydrologic Unit Codes (HUCs) from the U.S. Geological Survey. Included are delineation of the Narragansett and Thames mega-basins.
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. In the 4-digit HUCs, the first two digits identify the region and the first four digits identify subregions.
The polygon layer is named MEGABASINS_POLY and the line layer MEGABASINS_ARC. Annotation is included in MEGABASINS_ANNO_BASIN.
he polygon attribute table has the following items:
|NAME||Mega basin name (for informal use only - does not conform to USGS naming)|
The mega basins' ID and names are as follows:
In the arc attribute table, the item OUTLINE is coded as follows:
MassGIS maintains the layer, although no updates are planned.
For other watershed data, see these layers: