Presumpscot River Management Plan:

Cumulative Impacts

Mainers have relied on the Presumpscot River for its fisheries, power generation, and as a conduit for waste disposal for hundreds of years. These interactions have had far-reaching effects on:

Water resources: The presence of dams along the river has drastically reduced the variability in flow, thereby impacting the shape of the river. In addition, watershed development, waste discharges, and dams have resulted in degraded water quality (e.g. higher temperature, lower dissolved oxygen, increased total suspended solids).

Estuarine resources: Water quality in the estuary is also degraded, as evidenced by the absence of eelgrass beds. The sediments washing downstream into the estuary are moderately contaminated with pollutants including PAHs (polycyclic aromatic hydrocarbons).

Fisheries: The absence of fish passage at several critical dam locations, coupled with the fragmentation of habitats, has resulted in a decrease of habitat and a shift in species abundance.

Endangered species: A series of changes including timber harvesting, loss of anadromous fish, and use of pesticides have contributed to declining populations of some threatened and endangered plant and animal species in the watershed, including bald eagles.

Reacreational resources: The character of the river has changed with dams impounding most of the fast moving sections. This has implications on fishing and whitewater boating. Conversely, the impoundments have created opportunities for flatwater recreation.

Local and regional economy: Dams provide low-cost power, with direct, measurable impacts on the economy. More difficult to measure are the costs to the public for programs to reduce pollution, coupled with the lost revenue to the recreation industry.

More information on the historic and present uses of the river and its watershed, as well as details of the cumulative impacts of these uses, can be found in the reports below.