November 2005

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Overview

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.

Attributes

The polygon attribute table has the following items:
ITEM NAME DESCRIPTION
BASIN_ID 4-digit HUC
NAME Mega basin name (for informal use only - does not conform to USGS naming)
The mega basins' ID and names are as follows:
BASIN_ID NAME
0106 PISCATAQUA-SALMON FALLS
0107 MERRIMACK
0108 CONNECTICUT
0109 COASTAL
0109 NARRAGANSETT
0110 HOUSATONIC
0110 THAMES
0202 HUDSON
In the arc attribute table, the item OUTLINE is coded as follows:
ITEM NAME DESCRIPTION
OUTLINE
 
 Line type:
0 Internal megabasin boundary
1 State outline

Maintenance

MassGIS maintains the layer, although no updates are planned.
For other watershed data, see these layers:

Last Updated 11/23/2005