1.2 Water Resources (Please refer to Map 1-1 of the areas water resources.)
Little Harbor Classification: Class SA Land-use estimates for the 1.7 mi2 subwatershed are 43% residential, 43% forest, and 5% open land. Little Harbor is listed on the 2002 Integrated List of Waters in Category 4(a). This segment is impaired due to pathogens; a TMDL was completed and approved by EPA on September 12, 2002 (MassDEP 2006).
According to the TMDL study, most of the residential and commercial properties in the Little Harbor watershed are connected to the town of Cohasset public water supply. All the properties are serviced by on site sewage disposal systems (MassDEP 2002). The current sewer extension for this area should be completed by 2009 (Nye 2005). There are no Water Management Act withdrawals or NPDES permitted discharges in this segment. Based on the DMF shellfish growing area status, the Shellfish Harvesting Use is assessed as impaired because of elevated bacteria (MA DEP 2006).
Cohasset Harbor Cohasset Harbor includes waters south of a line drawn from the northwestern point of Scituate Neck, Scituate to just north of Quarry Point, Cohasset not including Cohasset Cove, Cohasset/Scituate. Land-use estimates (top 3, excluding water) for the 17.6 mi2 subwatershed are Forest 58%, Residential 27%, and Wetlands 7%. Cohasset Harbor is listed on the 2002 and the draft 2006 Integrated List of Waters in Category 5. This segment is impaired due to pathogens and a TMDL is required (MassDEP 2006).
The Gulf Watershed The Gulf Watershed covers an area of approximately 16 square miles and encompasses the municipalities of Cohasset (36%), Scituate (35%), Hingham (10%), and Norwell (19%). There are several significant hydrographic features in the Gulf River watershed. Lily Pond has been used as the Town of Cohasset’s drinking water supply since 1880. It is approximately 52 acres in size and can store up to 170 million gallons of water (Norfolk Ram Group 2002). Two tributaries, Peppermint Brook and Brass Kettle Brook feed into the pond and the Herring Brook serves as the natural outflow. The Aaron River Reservoir is an artificial water body that was formed in 1978 when a dam was erected to control flow in the Aaron River, the main tributary to the Reservoir. The Reservoir is located one mile south of Lily Pond and is hydrologically connected to the pond by a sluice gate at Bound Brook that is used to control water elevations in the Brook (Norfolk Ram Group 2002). Outflow from the Aaron River Reservoir into the Aaron River is controlled by a slide valve that controls flow over a fish ladder at the Reservoir dam. Bound Brook begins where the outflows from both Lily Pond and the Reservoir converge and extends to Hunter Pond. Hunter’s Pond has two fish ladders. One is impassable, the other has been modified. A few herring used this modified ladder last year. Aaron reservoir and Lily Pond both had large runs of alewives (Jim Drysdale, GRWA).
The Aaron River Reservoir and the Beechwood Street Dam both have fish passageways that are in excellent condition (Rebak, 2004). However, a flow control structure at the upstream side of Beech Street diverts flow from Aaron River into Herring Brook and into Lily Pond as part of the water supply system operations.
South Coastal Watershed Action Plan 9/12/2006 Watershed Action Alliance