What lies beneath the surface in Conowingo Reservoir presents what might be the largest threat to the health of the Chesapeake Bay. For years, Conowingo Dam has trapped sediment from entering the Bay. The velocity of sediment laden runoff from Pennsylvania and New York would be slowed down in the reservoir, giving the sediment time to settle to the bottom. Now, according to experts, the reservoir has reached its maximum capacity for the sediment load that it can handle - meaning that during every large runoff event we have, the sediment just flows unimpeded down the river and into the Bay.
There are two other dams upstream of Conowingo with reservoirs that are also maxed out with sediment - Holtwood and Safe Harbor Dams, both of which are in Pennsylvania.
This photograph shows water rushing out of the floodgates at Conowingo Dam into the lower Susquehanna River near Darlington, Maryland.