Geographic features: The northern portion of the subbasin contains ridges trending southwest to northeast and valleys of moderate width. The Susquehanna River cuts through these series of ridges and widens as it flows south to southeast through rolling hills and broad valleys of the central portion of the subbasin. The southern portion of the subbasin is characterized by metamorphosed sediments that have been intensely folded and faulted. This material caused the river to carve a deep gorge into the bedrock in a narrowing river valley. The Susquehanna River flows into the Chesapeake Bay at Havre de Grace, Maryland, providing over 50 percent of the freshwater inflow to the bay.
Of the six subbasins in the Susquehanna River Basin, the Lower Susquehanna Subbasin is the most developed. The steep river slope and narrow valley of the Lower Susquehanna gorge provide areas for hydrower development. This part of the subbasin is a major production area for electricity. Some of the most productive agricultural lands and largest population centers of the Susquehanna River Basin are located in the Lower Susquehanna Subbasin. Intense agricultural development occurs in many of the fertile limestone-type soils throughout the subbasin. A significant population is employed in government-related activities around Harrisburg, the state capital.
Total - 5,809 square miles
In MD - 280 square miles
In PA - 5,529 square miles
Major tributaries: Conestoga, Conodoguinet, Swatara, Conewago, Penn's
Total - 1,934,250* (46.6% of the total basin population)
In MD - 59,950
In PA - 1,874,300
*Population estimated from 2010 Census
Major population centers: Harrisburg, Lancaster, York, Lebanon, Carlisle (all in Pennsylvania)