Three watersheds comprise the Plum Island Sound land margin ecosystem: the
Parker River (155 km2), the Rowley (26 km2) and the Ipswich (404 km2). The Parker River watershed is largely undisturbed with extensive upland,
bottomland hardwood and cedar swamp forests. Almost 50% of the Parker River
watershed is set aside as conservation land. The basin contains some minor
rural-residential development. There is a single minor industrial development
and there are no major cities.
The Rowley River watershed is small and drains directly into Plum Island
Sound. The river has one wastewater discharge site and no mainstem dams. This
watershed is entirely low lying coastal plain and predominantly salt marsh.
There is some rural-residential development within the upper watershed.
The Ipswich River watershed is the largest and most developed. The watershed
is primarily coastal plain. There are three mainstem dams, one major
water treatment plant in the town of Peobody as well as eight smaller
wastewater discharge sites. Almost 25% of the Ipswich watershed is
set aside as conservation land, the rest is primarily suburban-residential.
Boston bedroom communities have been rapidly encroaching along the
southern portion of the watershed. The USGS maintains two gauging
stations on the Ipswich. The one at the mouth of the river has a mean
discharge of 249 cfs.
Dam samples from the Parker River and Ipswich River have been taken
approximately monthly since 1993, and at the Egypt River since 1999
to determine loading to the Plum Island estuarine system from the