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Subbasins - Wachusetts Reservoir
Geographic & Ecosystem Characteristics | Land Ownership & Land Use Patterns
Major Water Resource Issues | Recreation & Priority Habitat Areas
Resource Protection Goals & Recommended Actions

Land Area: 21.7 square miles or 16,024 acres
Permanently Protected Land Area: 4,680 acres (7.3 sq miles) or 38%
Limited Protection Land Area (Chap. 61, etc.): 655 acres
Dams: 1 in Clinton

% Imperviousness: approximately 10.6%
# of MA NHESP* Priority Habitat Sites: 1
# of discharge permits: none
Most threatened waterbodies: Gates and West Boylston Brooks
Location within the Nashua River Watershed Water Resources Habitat Analysis
Open Space Water Resources Natural Heritage
Limited Protection Water Resources Recreation

Geographic Overview and Ecosystem Characteristics: Most of this 16,024 acre (surface water not included) subbasin1 lies in the Massachusetts communities of Boylston and West Boylston with parts extending into Sterling and Holden. Located in the Southern New England Coastal Plains and Hills ecoregion2 of central Massachusetts, this area drains into the Wachusett Reservoir: the largest body of open water in the greater Nashua River watershed. The Southern New England Coastal Plains and Hills ecoregion is an area with generally similar soils, vegetation, shape of the land, and especially, moderate climate and bedrock geology (glacial tills and outwash deposits). Topography is generally hilly, encompassing numerous flatter wetlands, broad valleys, and floodplains.

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Land Ownership and Land Use3 Patterns: The land-use pattern is nearly 75% forest (hardwood mixed with softwood) or wetland plus low-density residential settlement as well as concentrated settlements and strip development located near town centers and along major roads. Agriculture (notably "hobby farms" and backyard horse paddocks), gravel extraction, commercial operations, industry and other developed land uses are less significant.

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Major Water Resource Issues: Streamflow, as in most of New England, has significant seasonal changes4. Based on recent findings in an Hydrologic Analysis (inflow/outflow) by Camp, Dresser, Mckee, under contract with EOEA for the Massachusetts Watershed Initiative Nashua Team, the Wachusett sub-basin is currently under a medium level of stress. With continued development and withdrawal pressures, the sub-basin will continue as "medium stress" by the year 2020. It should be noted that while there is a minimum flow requirement for discharge over the Wachusett Dam, local and regional water suppliers need to recognize the importance of continuing demand for supply on the reservoir.

This means that the net 7Q10 outflow from the sub-basin equals or exceeds the estimated natural 7Q10. 7Q10 is the lowest consecutive 7 day streamflow that is likely to occur in a ten year period in a particular river segment.

Because the Wachusett watershed is highly managed for the Worcester and MWRA withdrawals, these withdrawals were not considered in the evaluation of stress in the Wachusett Watershed-a much more detailed analysis would be required to evaluate their uses. Instead, the calculations were based on other uses of water in the watershed, particularly withdrawals by Holden, Rutland, Princeton, Sterling, and West Boylston. Based on these withdrawals, three of the four subareas in the Wachusett Watershed were calculated to have medium-stress in the future.

This subbasin features an extensive network of streams and rivers feeding the reservoir including: Boylston, Chaffin's (Unionville outlet), Gates, Malagasco, Malden, Scarlett and Waushacum Brooks; though, all together these brooks make up a comparatively minor percentage of the total inflow to the reservoir.

Though Wachusett Reservoir is principally fed by the Stillwater and Quinapoxet Rivers-together both account for about 30% of annual inflow5 -- these two are considered separate subbasins and are dealt with separately in this Plan. The Wachusett Reservoir provides very high-quality drinking water to a large portion of the Commonwealth's population via the Massachusetts Water Resources Authority (MWRA) and Metropolitan District Commission (MDC) Division of Watershed Management (DWM). More than 90% of the water leaving the Reservoir is withdrawn by the MWRA and only a small amount is released downstream to the South Nashua River.

The amount of permanently protected (owned by MDC and others) undeveloped open space, 28.4% (surface water not included), in the subbasin has meant that the water quality in the reservoir remains excellent, indeed, to such an extent that filtration treatment has to date been considered unnecessary. There are no wastewater treatment plants or industrial discharges in this subbasin.

10.6% of total impervious surfaces6 --namely, paved areas such as streets, driveways, and parking lots — for this whole subbasin indicates that concerns of compromised stormwater and other non-point sources7 of contaminants (for example: pesticides, fertilizers, oils, asphalt, pet wastes, salt, sediment, human litter and other debris) is an increasingly pressing concern. The majority of residents have on-site septic systems although a number of homes will be serviced by the new Holden-West Boylston Sewer Project.8

As for specific areas of concern, Wachusettt Reservoir itself has non-native plants* and mercury contamination (as found in fish tissue samples); thus, according to the 1998 Nashua River Watershed Report Card, the Wachusett Reservoir is rated as partially-supportive for biology and non-supportive of fish tissue. However, its waters are crystalline with low turbidity, bacterial counts, algal densities, and nutrients. On the other hand, Gates Brook is considered to be the "most contaminated tributary" in this subbasin with high nitrates and severe impairment for aquatic life. West Boylston Brook is similarly impaired and has the highest nitrate level. Both Gates and West Boylston Brooks are classified by the MDC as "severely septic polluted", having the highest fecal coliform loadings in this watershed, while Boylston and Malden Brooks are considered "moderately septic polluted streams".

Scarlett Brook is considered to be severely impaired for conductivity and fecal coliform which — as with the above mentioned streams — is expected to rise due to high numbers of improperly functioning septic systems and the area's increasing density of development. Beaman Pond, Boylston, Chaffin's (Unionville outlet), Malagasco, and Waushacum Brooks are other tributaries in this subbasin which are severely impaired for conductivity or fecal coliform9. Gates and Malagasco Brook, in particular, exhibit significant impacts potentially caused by contamination (as yet to be identified). Not withstanding these limitations, most of the small waterways in this subbasin are healthy functioning ecosystems exceeding Class A standards in many regards with low levels of phosphorus and other "non-point" pollutants. Also, each of the above mentioned tributaries to the Reservoir have low flows and, thus, contribute only a minor load of "impaired" waters. There are no 303(d)-listed* impaired water bodies in this subbasin.

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Recreation and Priority Habitat Areas: The Reservoir itself is important habitat for lake-nesting and lake-feeding birds. The entire water surface with adjacent upland connects with the Stillwater River as one large state-designated Natural Heritage and Endangered Species Program Priority Habitat area.10 The BioMap Core Habitat area in this subbasin corresponds directly with the NHESP Priority Habitat area, while BioMap Supporting Habitat areas lie along the eastern edge of this subbasin.

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Resource Protection Goals and Recommended Actions

GOAL: Protect wildlife habitat and migration corridors in the subbasin.

  • Assist MDC, MassWildlife, other state agencies, municipalities, and local land trusts in consensual transactions to acquire additional open space in priority areas.
  • Sponsor local events to raise public understanding about native wildlife and the impacts of development patterns on ecosystem and habitat integrity.
  • Work with local conservation commissions to gain their backing of natural resource/ habitat inventories.
  • Continue MDC-DWM's Private Land Forestry program which encourages private forest landowners to adopt forestry practices - namely, forest management planning required by the Chapter 61 program — that protect water quality

GOAL: Protect high-priority open space, vistas, and community character in the subbasin.

  • Encourage the use of MA Executive Order 418* funding for "Open Space and Resource Protection Plans" for each Massachusetts community in the Stillwater River subbasin.
  • Conduct public education sessions to promote local passage of Community Preservation Act*.
  • Work toward ideal of at least 25-50% protected open space in each municipality.
  • Work with municipal officials to develop subdivision standards that require proponents to devote at least 50% of land (not including already undevelopable wet or steep land) for open space conservation and encourage mixed-use development and cluster zoning by-right bylaws.

GOAL: Increase recreational opportunities throughout the subbasin.

  • Support the Wachusett Greenways group in its volunteer efforts to link communities via multi-use intermunicipal trails and open spaces, and in particular the Mass Central Rail Trail.
  • Improve canoeing, fishing, and swimming opportunities by removing weeds from water bodies.
  • Educate the public and municipal departments (especially Public Works Depts.) on efforts relating to invasive species* identification and removal.

GOAL: Improve water quality in the basin.

  • Conduct more detailed inflow/outflow studies given stressed status of some waterways.
  • Evaluate West Boylston and Holden's sewering project for impact on surface water quality.
  • Assist Boylston and West Boylston with its EPA's Clean Water Act-mandated MS-4 Phase II stormwater requirements.* These municipalities will be required to obtain permits to reduce impacts to the receiving streams through the development of Best Management Practices* (BMPs), elimination of cross-connections and significant public education. CSO controls and the development of a long-range control plan will be required.
  • Identify the major sources of fecal coliform and nitrate-nitrogen inputs to the river and work with communities to address the problem.
  • Identify the degree of threat from potential faulty/ illicitly discharging septic systems, which may result in bacterial and nutrient contamination of nearby streams and groundwater.
  • Identify underground storage tanks (USTs) and work with communities to have them removed.
  • Monitor effects of increasing urbanization to prevent diminished groundwater recharge and to declining stream flow as well as stream channel widening and downcutting.
  • Help develop and disseminate Best Management Practices for small-scale, hobby type agricultural operations.

GOAL: Reduce negative effects of development in this subbasin.

  • Monitor uncontrolled runoff from construction sites to prevent sedimentation of streams.
  • Track increased imperviousness and both direct and indirect riparian zone alterations that may increase stream temperature and cause sedimentation.
  • Help local volunteer board members responsible for development and land-use rulemaking and enforcement get technical assistance and information regarding fundamental and innovative techniques to control and guide land use and development balanced with adequate resource protection (e.g., Citizens Planner Training Collaborative11 workshop offerings).
  • Increase or establish staff hours of municipal conservation agents to more effectively monitor runoff from construction sites and assist with the preparation of relevant bylaws.
  • Write and implement stormwater, erosion and sedimentation bylaws/controls.

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* See glossary.

1 For this Plan, subbasins were delineated and analyzed using USGS defined boundaries which sometimes are truncated at the gaging station and may not appear to be consistent with topographically determined drainage areas.

2 The Southern New England Coastal Plains and Hills ecoregion is an area with generally similar soils, vegetation, shape of the land, and especially, moderate climate and bedrock geology (glacial tills and outwash deposits).

3 "Land Use" description at

4 Corresponding to seasonal stream flow changes are notable spikes in bacteria levels during summer and fall. Seasonal cycles of high bacteria concentrations may be attributed to decreased dilution during summer months, when tributary flows are lowest. (Wachusett Reservoir Watershed Protection Plan Update 1998, pp. 2-29)

5 Water from the Quabbin Reservoir -- some 35 miles due west of the Wachusett Reservoir -- is regularly transferred to the latter through the Quabbin Aqueduct and accounts for about 50% of the inflow to Wachusett on an annual basis. (Wachusett Reservoir Watershed Protection Plan Update 1998, pp. 1-4)

6 According to the Center for Watershed Protection's Rapid Watershed Assessment Handbook protocol, an area with less than 10% (8 - 12%) impervious surfaces is considered "partially threatened"; less than 8% is considered "sensitive" or what one would say is a relatively pristine environment;" 12 - 20% is considered "threatened"; and more than 20% is considered "non-supporting" or urbanized. The figures cited in the narrative are based on NRW Estimated Impervious Cover by Sub-basin based on '85/'92 Land Use: MDC '98 Methods Estimate by Bruce Bayne and Jo Anne Carr of the EOEA Nashua River Watershed Team.

7 Non-point source pollution, also known as polluted runoff, is the single largest source of water pollution nationwide. Polluted runoff is the result of rain or melting snow carrying pollutants or sediments from the land to the water. Polluted runoff results in water pollution from land-disturbing activities like agriculture, forestry, mining and urban development.

8 Historically, the MDC Division of Watershed Management "has considered on-site wastewater disposal systems to be the most significant source of pathogens and other pollutants of concern within the [greater] Wachusett watershed." (Wachusett Reservoir Watershed Protection Plan Update 1998, pp. 6-23)

9 It should be noted that fecal coliform data have a large degree of variability as seasonal, transient spikes greatly elevate annual averages. Furthermore, wintertime roosting gulls and other native wildlife are important sources of fecal coliform bacteria, as are failing septic systems and some agricultural practices.

10 Focus Areas for Wildlife Habitat Protection in the Nashua River Watershed (MAS, 2000).

11 Citizen Planner Training Collaborative (CPTC)
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