OVERVIEW

MassGIS produced an aquifer datalayer composed of 20 individual panels, generally based on the boundaries of the major drainage basins. Areas of high and medium yield were mapped. The SDE layers contain seamless data from Basin-based tiles and are named AQUIFERS_POLY and AQUIFERS_ARC.

Aquifer polygons were not delineated for Cape Cod and the Elizabeth Islands. These areas in their entirety are considered by the Massachusetts Contingency Plan (MCP) as medium yield aquifers. The areas of Martha's Vineyard and Nantucket not delineated as high yield aquifers are also considered as medium yield under the MCP.

This datalayer NO LONGER includes polygon attribute coding to help in the identification of areas in which clean up of hazardous waste sites must meet drinking water standards, as defined in the Massachusetts Contingency Plan (MCP) (310 CMR 40.0000). Please refer to the DEP NPDWSA Datalayer for areas that are defined as Non Potential Drinking Water Source Areas.

MANUSCRIPT

The USGS 1:48,000 hydrologic atlas series on groundwater favorability was produced for all of Massachusetts. The basemaps for these were photographically reduced and spliced together from 1:24,000 USGS quadrangles. Each manuscript covers one of the major drainage basins. They have been individually researched and published by the USGS-WRD starting in the 1960s and continuing to the present. Several have been compiled but not yet published. In these cases the draft manuscripts were automated.

The definition of high and medium yield varies between panels, as it does on the source manuscripts. While the medium yield for most basins is between 100 and 300 gpm (gallons per minute), this range may vary greatly from basin to basin. High yield definitions vary from basin to basin as well. Yield for each panel is found in the metadata file AQ.SRC.

Entering the data in Librarian format modified the tiling scheme of this layer. The aquifers are now tiled by major basin grouping as illustrated in the Basin Index. However, the original tiling scheme may be recovered by reselecting on the PANEL item in the polygon attribute table.

The high and medium yield categories were automated from the manuscripts. The major drainage basin boundary was copied from the MAJ_BAS coverage to use as a template for digitizing. Because ponds and lakes are also closely related to aquifers, they were clipped from water bodies in the 1: 100,000 Hydrography datalayer and also used as a template. The USGS manuscripts were not edgematched to adjacent panels; no attempt has been made to resolve interpretation inconsistencies between panels.

The arc feature class has one item called OUTLINE. The drainage basin boundary is coded as '1'. All other arcs are coded as '0'.

The polygon feature class has the following items:
 

	CODE		0 = Non-aquifer area 1 = Pond 2 = High yield ( > 300 gallons per minute) 3 = Medium yield (100-300 gpm) 4 = Low yield ( < 50 gpm)
	TYPE		Character values the equivalent to the CODE item (POND, HIGH, MED, LOW)
	YIELD		Yield in gallons per minute for the aquifer classes
	TRANS		Transmissivity in square feet per day
	AREA_SQ_FT		Area in square feet of each polygon
	AREA_ACRES		Area in acres of each polygon
	BAS_ID		Major basin ID
	PANEL		Original basin panel, used to identify source of aquifer data

The item PANEL stores the panel code identifying data sources and changes of the data from its original tiling scheme. Using the identifier PANEL as the link between the data and metadata, table AQ.SRC contains the AQ.DOC records from the original, individual aquifer coverages. More than one record may exist per panel.

Plots of each panel were made at a scale of 1:48,000 and compared to the source map. Corrections were made as needed.

To properly portray the aquifers with full statewide coverage, users should refer to the image above. This image displays the Aquifers layer symbolized on CODE or TYPE. If the display of NPDWSA is desired, see the "Displaying the Data" section in Non-Potential Drinking Water Source Areas layer.

This datalayer is maintained by MassGIS. In June 2003, the DEP GIS group modified all tiles to remove the NPDWSA designations.
In July 2007, the boundaries of two polygons in the town of Colrain were modified.

Last Updated 7/31/2007
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