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MassGIS Data: Surface Water Supply Watersheds

May 2023

This datalayer contains the watershed extents for all surface water supplies including active, inactive, emergency, sources outside of Massachusetts, watersheds that extend into other states and watersheds of sources from other states that extend into Massachusetts.

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This datalayer contains the watershed extents for all surface water supplies including active, inactive, emergency, sources outside of Massachusetts, watersheds that extend into other states and watersheds of sources from other states that extend into Massachusetts. Surface water intakes on Class B Rivers are not included in this datalayer, with the exception of Horn Pond in Woburn where the water is drawn in through wells adjacent to the shoreline.  Please refer to the Surface Water Supply Protections Zones datalayer and the Public Water Supplies datalayer for information regarding regulated protection zones and public water supply intake information.

The layer is named SWP_WATERSHEDS_POLY.


Those areas that contribute to public surface water supplies were originally taken from the USGS Drainage Sub Basins datalayer. Starting in 2003, the DEP GIS Program began using the elevation control points and breaklines from the 1990s Aerial Imagery Project to create a digital elevation model of a surface water supply watershed, and using the ArcHydro toolset developed by ESRI and the University of Texas to delineate watersheds digitally. These basins were then field checked by MassDEP Drinking Water Program staff and edits made when necessary. This work is ongoing and is about 35% complete, with watersheds prioritized by perceived accuracy or if threats to the watershed are identified, with work now progressing in Essex County. Basin extents for watersheds outside of Massachusetts where taken from the NRCS Hydrologic Unit Code (HUC) data or from data provided by other New England states. Where this data was not sufficient basin edges where delineated using the contours from USGS quads in DRG format. The attributes relating to water supply zones in the existing USGS 


Attributes include information from the Public Water Supplies datalayer and summary information from the Surface Water Supply Protections Zones. More detailed information about the source is contained in the Public Water Supplies datalayer.

The attributes for each feature are:

SOURCE_ID Surface water supply source-id from the  Public Water Supplies datalayer; RI sources are coded as RHODEISLAND
TYPE PWS Type. See Public Water Supplies datalayer for current:
 SW – Surface Water (Active or Inactive)
 ESW – Emergency Surface Water
 RI – Rhode Island Source
SITE_NAME Site Name of the reservoir or intake, taken from the  Public Water Supplies datalayer
WSHEDACRES Area of the entire watershed in acres
RESVRACRES Area of the reservoir in acres
ZONEAACRES Area of the  Surface Water Supply Protections Zones A in acres
ZONEBACRES Area of the  Surface Water Supply Protections Zones B in acres
ZONECACRES Area of the  Surface Water Supply Protections Zones C in acres
SUPPLIER Public Water Supplier Name, taken from  Public Water Supplies datalayer
TOWN Town name of the supplier
REG_OBJ_ID MassDEP Facilities Regulated Object ID


The Massachusetts Department of Environmental Protection (DEP) GIS Program is maintaining this datalayer. Any updates sent to MassGIS will be forwarded to DEP and incorporated into this data layer. Please reference the town, water supplier id, water supply source id (if known), and major basin identifier when providing updates.

May 2007 – Wenham Lake Reservoir (3030001-01S) zones updated.
July 2007 – Watersheds updated for all sources in Beverly, Peabody, and Lynn

January 2009 – Watersheds updated for all sources in Danvers, Ipswich, Manchester, Gloucester, Rockport, Newburyport, Haverhill, Amesbury, Andover, North Andover, Wakefield, Winchester, Burlington, Concord, Leominster, Lincoln, Colrain, Greenfield, Fitchburg sources 01S, 03S, 06S, 09S and 13S and MWRA’s Spot Pond. Sources in Cambridge (Waltham) and the MWRA Ware River Intake were edge matched for adjacent newly delineated watersheds. Features were edited in Peabody, North Brookfield, Holyoke, Northfield, Williamstown, Amherst and Fall River. Clinton, Holden, Rutland, Westminster and Worcester sources and the MWRA’s Wachusett Reservoir watershed are included in this update as preliminary, they have not been field verified except where the watersheds adjoins Leominster and Fitchburg watersheds to the north. In March 2009 the Sartori Quarry Reservoir was added.

In March 2010 the following updates (completed in November 2009) were released: Watersheds were updated for all sources in Ashburnham, Gardner, Fitchburg (North), Hudson, Marlboro, Milford, Westborough, Winchendon, Cambridge, Abington, Attleboro, Braintree, Brockton, Fall River, Falmouth, Hingham, Holbrook, New Bedford, Plymouth, Randolph, Somerset, Taunton, Wareham and Weymouth. The watersheds for Worcester sources and the Wachusett Reservoir are now final. Watersheds for Cohasset sources and some Rhode Island sources were edge-matched to the newer watersheds.

April 2017 - Watersheds updated for all sources in the MassDEP Western Region (source ids start with a “1”) ( Berkshire, Franklin, Hampden and Hampshire counties) except for the Cobble Mountain Complex (source ids 1281000-02S, 1281000-05S, 1281000-07S) and the Quabbin Reservoir (source id 6000000-02S) . The watersheds for Mill Pond (Burlington Water Dept.), Old Oaken Bucket Pond (Scituate Water Division) and Silver Lake (Brockton Water Commission) (source ids 3048000-02S, 4264000-01S, 4044000-01S) were altered per MassDEP staff input.

In April 2023, watersheds associated with the following sources were removed due to abandonment in the MassDEP Water Quality Testing System (WQTS):

  • HORN POND  (3347000-01S)
  • BEAR HOLE RESERVOIR  (3347000-01S)

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