Most of the river lies in Pennsylvania. The Susquehanna River has an average flow of 19 million gallons of water per minute, the highest average flow of any river in the eastern United States. Although the average depth of the Chesapeake is only 30 feet, a channel over 180 feet deep runs through its center. The channel is the original Susquehanna River bed, dating back to the Ice Age. Excess nutrients cause an overgrowth of algae, called algae blooms.
Algae blooms deplete oxygen supplies and block sunlight needed by aquatic plants and animals.
Pennsylvania contributes an estimate 36 percent of the nitrogen and 25 percent of the phosphorus entering the Bay. Over half of the nitrogen and the phosphorus entering the Susquehanna River comes from agricultural runoff. Improper fertilization of residential lawns and gardens, malfunctioning septic systems, industrial activities, and air deposition of nitrogen and phosphorus can also affect water quality. The Pennsylvania Chesapeake Bay Program was launched in 1984 in response to an Environmental Protection Agency study that reported the health of the Bay is declining. The Pennsylvania Bay Program is supported by state and federal funds.