Methodology

The Watershed School examined water quality in the Megunticook River along three dams of the Megunticook River: the Montgomery Dam, Knox Mill Dam, and Knowlton Street Dam. The three dams examined are located closest to the outlet into Camden Harbor, and are all being evaluated for full or partial removal in order to reduce flood risk. The removal of the dams along the Megunticook would also restore the river's natural state and provide options for fish passage. Water quality information was taken at these particular locations, both directly above and below each of the dams. Using LoggerPro, students tested the water's pH, temperature, conductivity rate, and flow rate.

• Hydrology

When a dam is built, the flow of water, both above and below the dam, is drastically altered. Above the dam, a deep, still reservoir is created, where once there was a free-flowing river. Most fish, mussels, and other aquatic animals that once thrived in the river often are not able to survive in the lake- like habitat of the reservoir. When a dam is removed, the river’s natural hydrology (movement of water) is restored. Above the dam, habitat for native river species is reestablished as the reservoir disappears. And below the dam, the natural flow patterns that native plants and animals are accustomed to are returned to their original configuration.

• Water Quality

In addition to altering the flow of water, dams can alter the physical and chemical characteristics of the water itself. Aquatic organisms such as fish and macroinvertebrates have varying tolerances to dissolved oxygen, temperature, conductivity, salinity and pollution. While too much sediment, like silt, sand, and rocks, in a river is harmful, rivers naturally carry a certain amount of it. The amount of sediment a stream carries depends on geology, the velocity of the water and the steepness of the streambed. This means that when water comes to a standstill behind a dam, most of the larger sediment drops to the bottom. The result is that sediment free water comes out of the dam. While this may seem like a good thing, it can lead to problems downstream. This clean water then picks up sediment from the streambed and stream banks below the dam, but no sediment is deposited to replace it, so there is increased erosion within the stream itself. This increased erosion can alter the character of a streambed, possibly eliminating mussel habitat or important spawning grounds for fish. Removal of the dam would restore the natural downstream movement of sediment.

• Migration

There are numerous fish species, including American Eels, Alewives, Blueback Herring, Sea Lamprey, Rainbow Smelt, and Sea-run Brook Trout that migrate up and down rivers as a part of their life cycle could be seen traveling upstream from the harbor all the way to Megunticook Lake and beyond. A dam without some mechanism to move fish around it can impede migration and block movement to spawning grounds, resulting in a decline in reproductive success.