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MASSACHUSETTS DRAINAGE SUB-BASINS
Description:
MassGIS has produced a statewide digital datalayer of the approximately 2300 sub-basins as defined and used by the USGS Water Resources Division and the Mass Water Resources Commission and as modified by Executive Office of Environmental Affairs (EOEA) agencies. These sub-basins were aggregated together to make the 28 basins of the Major Basins Datalayer. Cape Cod and the Islands do not have much lateral 'surface' drainage because the soils are so porous. The sub-basin line shown for Cape Cod is the approximate groundwater divide between Cape Cod Bay, Vineyard Sound, and the Atlantic Ocean, taken from sub-surface groundwater contours. The state coastline and boundaries are included in the sub-basin coverages and are differentiated by arc attributes. The sub-basin datalayer is stored in the Basin library. Coverages are named SUBBAS. A set of 1:24,000 USGS paper quad sheets was delineated into approximately 2200 minor or drainage sub-basins. This work was produced over the past 20 years mainly by the USGS-WRD. Generally, the contours on the quads are the primary guide to basin boundaries. Often the 'mouth' of a basin is marked at the site of a stream gaging station, which can be different from the strict geographic location of the mouth. All sub-basins on the manuscripts were digitized. Due to good manuscript quality, including the visual edgematching of the 189 sheets, digitizing and edgematching was straightforward. The manuscript author was consulted on the minor errors and ambiguities that were discovered. Drainage boundaries added to Cape Cod were created by the Massachusetts Bays Program (the boundary separating drainage between Nantucket Sound/Cape Code Bay/Atlantic Ocean) and the Buzzards Bay Project (the boundary separating drainage between Buzzards Bay and Nantucket Sound/Cape Code Bay). The subdivisions were created by delineating groundwater divides using the 1:48,000 scale USGSHydrologic Atlas Series maps. The delineations were reviewed for consistency by the USGS Water Resources Division, but they are not considered official basins of the USGS or the MA Water Resources Commission. In the fall of 1992 the MA Department of Environmental Protection Division of Water Supply added the state boundary and 1:100,000 coastline and extended or clipped the sub-basins to meet them. Additional drainage basins were delineated at the intake points of public water supplies. From these additional basins all upstream basins were coded as contributing to a surface public water supply. DEP regionalstaff determined which water supplies were primary and which were emergency or backup supplies, and the MDC provided the basins covered by MDC/MWRA jurisdiction.
