Low Flow Inventory

Merrimack River Basin

Bare Meadow Brook; Cobbler Brook; Martin’s Brook; Merrimack River; Spickett River; Stony Brook

Observations

The Merrimack River Watershed Council and the Groton Lakes Association conducted a shoreline survey of Martin’s Pond Brook in 1999 below the outlet of Martin’s Pond in Groton. From the outlet of the pond to the Route 40 culvert the brook was dry during August and September. Low flow conditions as well as erosion, sedimentation and turbidity problems were also observed on Bare Meadow Brook from its headwaters in Methuen to its confluence with the Merrimack River. These conditions were attributed to crushed culverts, clogged storm drains, and beaver activity in the area (1).

Suspected Causes

Dam Management A local resident reported that the operation of the Methuen Falls hydropower project on the Spickett River at Methuen Square repeatedly drained the river dry over the summer of 2002 and affected river flows well into the New Hampshire portion of the Spickett River(4).

Bypassed Reaches / Diversions At the Lowell Project hydropower facility on the Merrimack River in Lowell, 0.7 miles of river including Pawtucket Falls can be bypassed through a canal system to generate power. The riverbed is periodically exposed when flow is diverted, particularly during naturally low flow periods. In the 1999 Water Quality Assessment Report, DEP recommended establishing minimum flow requirements through the bypassed reach in the next round of permitting (1).

Consequences

Pollution Reduced baseflow may have contributed to significant deposits of sand and silt on Stony Brook from the outlet of Forge Pond in Westford to its confluence with the Merrimack River (1). As water velocities drop, finer particles are able to settle out of the water column and consequently smother the gravel and boulder habitats that are nest and nursery locations for many species of fish as well as preferred habitat for many aquatic macroinvertebrates.

Aquatic Flora and Fauna Low flows limit the amount of habitat available to fish and other aquatic organisms in Cobbler Brook from its headwaters in Merrimac to its confluence with the Merrimack River. DEP staff observed the channel only half full in 1999, leaving the other half high and dry and inaccessible to water-dependent species (1).

References & Resources
1) Kennedy, Laurie E., Kiras, Stella, and Richard McVoy. November 2001. Merrimack River Basin 1999 Water Quality Assessment Report, Report Number 84-AC-1, DW Control Number 52.0. MA DEP, Bureau of Resource Protection, Division of Watershed Management.
2) USGS real-time stream gage data for the Merrimack River below the Concord River at Lowell.
3) USGS real-time stream gage data for the Spicket River in Metheun.
4) John Loeschen. August 25,2002. Email to Joan Kimball, Riverways Programs.