Buzzards Bay National Estuary Program

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Home  >   Buzzards Bay Pollution & Response  >   Nitrogen Pollution  >   BB Subwatershed Data

Subwatershed Land Use and Nitrogen Loading

What is on this page

On this page we present summary statistics of land use in the various subwatersheds around Buzzards Bay, estimates of nitrogen loading using the Buzzards Bay NEP' nitrogen loading model for MassGIS landuse statistics, and where available, more detailed estimates of nitrogen loading based on parcel land use analysis developed by the DEP Massachusetts Estuaries Project, the Cape Cod Commission, or the Buzzards Bay NEP.

Watershed delineations

Our analysis is based on accepted delineations of Buzzards Bay watershed and subwatersheds (download the GIS data). Most of the boundaries were established by USGS and the Cape Cod Commission in the early 1990s, but they are now under review by DEP and USGS as part of the Massachusetts Estuaries Project initiative. Click on the map on at the lower right of this page to see the subwatershed delineations. Read also the information on our page about changes in the watershed boundary.

Nitrogen Loading and Land Use Spreadsheets

2004 Buzzards Bay subbasin landuse statistics and embayment areas (Excel file)

See the additional data and information on our Nitrogen Management Information page.

Sewering and Wastewater Facility Discharges

Accounting for sewering, and changes in the extent of sewering represents one of the biggest challenges to managers conducting nitrogen loading analyses. This is because even after an area is sewered, because groundwater typically travels only one to two feet per day, it may take ten to twenty years for septic system contaminated groundwater flows to reach the coast from inland areas depending on soil types and groundwater flow patterns. Since 2000, many areas of Buzzards Bay have been sewered. This contrasts with the 1990s, when there was little new sewering, and most of the population growth was served by onsite septic systems. Just as sewering may not be reflected in coastal water quality for many years, these new septic systems also have not yet exerted their effect.

This changing landscape of sewering seen in the two maps of Buzzards Bay sewer coverage below. One represents the extent of sewering in Buzzards bay about 1995, the other represents the extent of sewering in 2008. Beside these changes, elimination of CSO discharges in New Bedford, upgrades in the treatment of effluent of Buzzards Bay municipal wastewater treatment facilities, increases or decreases in the change of flow of those facilities all must be accounted for in any loading analysis.

     

Sewering in Buzzards Bay about 1995 (left) versus expected by 2009 (right). Click on the maps for enlarged views.

Embayment area, bathymetry, and tidal range

Embayment	Water area km2	mean depth at MLW (m)	mean depth (m) at Half Tide	Vol. at MLW m3x10^6	Vol. at Half Tide m3x10^6	Tidal Range(m)
Agawam River	0.47	0.50	0.85	0.23	0.40	0.70
Allens Pond	0.77	0.50	0.90	0.39	0.69	0.80
Apponagansett,inner	1.34	0.60	1.15	0.80	1.54	1.10
Aucoot Cove	1.29	2.22	2.87	2.86	3.70	1.30
Back River- Eel Pond, Bourne	0.08	0.70	1.20	0.06	0.10	1.00
Brant Island Cove	0.34	0.81	1.36	0.27	0.46	1.10
Broadmarsh River	0.40	0.30	0.80	0.12	0.32	1.00
Buttermilk Bay	2.14	1.19	1.74	2.55	3.73	1.10
Clarks Cove	2.86	3.57	4.12	10.20	11.77	1.10
Eel Pond, Mattapoisett	0.10	0.70	1.00	0.07	0.10	0.60
Hen Cove	0.26	0.83	1.43	0.22	0.37	1.20
Little Bay Fairhaven	0.74	1.10	1.66	0.81	1.23	1.12
Little River	0.35	0.58	1.13	0.20	0.39	1.10
Mattapoisett upper Harbor	1.59	2.84	3.44	4.52	5.47	1.20
Megansett Harbor	1.70	4.57	5.17	7.77	8.79	1.20
Marks Cove	0.46	0.78	1.38	0.36	0.64	1.20
Little Bay - Inner Nasketucket Bay	2.05	1.59	2.14	3.25	4.38	1.10
New Bedford Harbor (Acushnet River)	3.85	3.53	4.13	13.60	15.91	1.20
Onset Bay	2.39	1.29	1.84	3.09	4.40	1.10
Phinneys Harbor	2.17	2.00	2.60	4.35	5.65	1.20
Pocasset Harbor	1.00	2.20	2.80	2.00	2.60	1.20
Pocasset River	0.80	0.93	1.53	0.74	1.22	1.20
Quissett Harbor	0.47	1.57	2.17	0.74	1.02	1.20
Red Brook Harbor	0.61	1.74	2.34	1.06	1.43	1.20
Sippican Harbor upper harbor	1.70	1.44	2.04	2.45	3.47	1.20
Slocums River	1.97	0.74	1.29	1.45	2.53	1.10
Squeteague Harbor	0.30	0.81	1.41	0.24	0.42	1.20
Wareham River	2.49	0.96	1.56	2.40	3.89	1.20
Weweantic River	2.38	1.14	1.74	2.72	4.15	1.20
West Falmouth Harbor	0.80	0.58	1.18	0.47	0.95	1.20
Widows Cove	0.54	0.94	1.54	0.51	0.83	1.20
Wild Harbor	0.49	1.17	1.77	0.57	0.87	1.20
Wings Cove	0.88	1.39	1.99	1.22	1.75	1.20
Westport River, East Branch	8.02	0.77	1.17	6.21	9.42	0.80
Westport River, West Branch	5.32	0.78	1.18	4.17	6.30	0.80

Note: 1 square kilometer = 100 hectares = 247.1 acres

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