The Memramcook River has a drainage area of 400 km², including several small tributaries. The upper reaches of the Memramcook River watershed remains largely wooded aside from the Memramcook and Dorchester communities. Despite having a small area of its watershed influenced by human activity there are still potential pollution sites. Notably, activities associated with the Gayton Quarry, situated on each side of the river near Route 6, constitutes a potential threat to water quality. The river is tidally influenced up to the causeway, below which differing levels of salinity can be found during different levels of tide, when the freshwater of the river mixes with salt water of the incoming tidal waters.
The Memramcook causeway, built in 1973 , is owned and operated by the Province of New Brunswick, located on College Bridge modifies the hydrological characteristics of the river, creating Memramcook Lake, and changes its natural ecosystem functions for 400 km2. When the causeway gates are open, the river sees an increase in water volume causing sediments to become suspended and results in large fluctuations in parameters such as E. coli, sedimentation, and salinity. Such dramatic fluctuations are stressful for aquatic organisms inhabiting the river and make generalizations about river health difficult. The causeway also serves as a periodic barrier to fish passage when its gates are closed, and does not have a fish ladder present, continues to create an obstruction to natural fish passage conditions to roughly 60 percent (240 km2) of the Memramcook River system.
The causeway also caused the elimination of several kilometres of upstream estuary, affecting the historical tidal range and salt-fresh water exchange in the system. Both the Memramcook causeway is responsible for the elimination of nearly every historical fish species in the river system, including the distinct Inner Bay of Fundy Atlantic salmon, American shad, Striped bass, Atlantic tomcod, Sea run brook trout and others. The Memramcook causeway also continues to be responsible for the buildup of massive sediment deposits downstream, reducing the width of the Memramcook River and affecting Shepody Bay’s mudflats, a critical habitat for migrating shore birds. In the fall of 1999, the Province of New Brunswick initiated the process of restoring free flow to the Memramcook River at the request of the community. The plan to restore the Memramcook River has yet to be implemented. However, removal of the Memramcook causeway remains a top priority for the community.
The South Branch of the Memramcook River is situated in the upper part of the Memramcook River watershed and has a watershed area of 12 km². The physical habitat surrounding the upper area of the river is forested which results in high organic matter deposits. These deposits settle in the substrate and during decomposition release humic acid causing water to occasionally display yellow colours. The presence of beavers in the area leads to frequent damming and the formation of ponds as well as reduced water velocity.
Site Name: Memramcook River @ Aboujagane Rd.
Site Code: MemU
Coordinates: 46.04352, -64.47316
Site Name: Memramcook River @ TransCanada
Site Code: MemL
Coordinates: 46.04312, -64.56505