The Susquehanna River, in the Mid-Atlantic States of the United States, has a collection of dams. These dams are used for power generation, flood control, navigation and recreation. These dams have local and regional environmental impacts on the river and the Chesapeake Bay, both positive and negative. Environmental impacts And by making it more Susquehanna specific. The dams have a positive impact on the environment. They slow water, trapping silt and pollutants. Conowingo Dam 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. Conowingo Dam is noted for its bald eagles. Hydroelectric power is considered an environmentally friendly method of power generation. The dams also make a negative impact on the environment. They 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 to mitigate this. Human impacts And by making it more Susquehanna specific. The dams have both a positive and negative impact on human society, outside of the environmental impacts above. River dams have long been associated with power generation. In the past dams powered mills directly. Today dams are used both for direct hydroelectric generation and to form pools for cooling other forms of generation. Dams create navigable stretches of river where they may have been unnavigable before. The first dams at Sunbury, Pennsylvania were to support year round ferry crossings. The creation of dams does have negative impacts. Communities on the river edge are displaced, such as Conowingo, Bald Friar, and Glen Cove, Maryland in 1928. Longitudinal river navigation is impeded. Although the historic Susquehanna was very difficult to navigate most of the year. Timber rafts could come down in the spring high water, but very few boats went up the river, before the canals were built. The Conowingo Dam is located near "Smith's Falls", where John Smith had to turn back while exploring the region in the early 17th century due to the impassable rapids. List of dams Listed from the headwaters toward the mouth of the river. This includes existing