The dams slow water, trapping silt and pollutants. Conowingo Dam[1] is credited with preventing much of the silt from Pennsylvania from reaching the Chesapeake Bay. The dam spillways can add oxygen to the water. The down stream side of dams is favored by aquatic birds, possibly because the fish that pass through the dam are a bit stunned. Hydroelectric power is an environmentally friendly method of power generation. The dams also raise the water level, altering the riparian environment. The upstream pools can become environmentally unsound below the surface, especially during summer. They block migratory fish, such as the American shad. The dams from York Haven down to the Chesapeake all have fish ladders or lifts in an attempt to mitigate this.
Communities on the river edge have been displaced, such as Conowingo, Bald Friar, and Glen Cove, Maryland in 1928.
List of dams
Listed from the headwaters toward the mouth of the river. This includes existing and historic structures, as well as dams off the river that have a major impact on the river. The river also grows its own ice dams during the winter and notable ones will be included.
