Conowingo Dam

The reservoir behind Conowingo Dam has long captured sediment flowing downstream, but recent studies have drawn attention to its changing effectiveness as a “pollution gate.”

FAQ

  • How do storm events impact Conowingo dam?

    Although smaller storm events can cause sedmient to flow over the dam, the greatest concern is with large storms events and severe floods. Large storm events are predicted to occur every three to four years in the Chesapeake Bay region.  During the last major storm event, Tropical Storm Lee, four million tons of sediment flowed over the dam.

  • How much sediment is trapped behind Conowingo Dam?

    As of 2014, an estimated 174 million tons of sediment are trapped behind the dam with an additional 3 million tons added each year.

  • What is scouring?

    Scouring occurs when fast-moving water moving disrupts the arrangement of sediment in a river or stream, depositing the material downstream.

  • How does sediment affect the Bay?

    Sediment is made up of loose particles of sand, silt and clay. It is a natural part of the Chesapeake Bay, created by the weathering of rocks and soil. In excess amounts, sediment can cloud the waters of the Bay and its tributaries, blocking sunlight for underwater grasses, covering bottom habitats (such as oyster beds) as it settles and reducing water quality for fish and other aquatic species.

  • Where do nutrients come from?

    In general, nutrients like nitrogen and phosphorous reach the Chesapeake Bay from three sources: wastewater treatment plants; urban, suburban and agricultural runoff; and air pollution. Nutrients can also come from natural sources, like soil, plant material and wild animal waste.

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Terms

  • Nutrients

    Chemicals that plants and animals need to grow and survive but, in excess amounts, can harm aquatic environments. Elevated levels of the nutrients nitrogen and phosphorous are the main cause of poor water quality in the Chesapeake Bay.

  • Pollution

    The introduction of harmful substances or products into the environment.

  • Reservoir

    A natural or artificial place where water is collected or stored for use, especially water for supplying a community, irrigating land and furnishing power.

  • Sediment

    Loose particles of sand, silt and clay that settle on the bottom of rivers, lakes, estuaries and oceans. Suspended sediment pushed into the water by erosion is one of the biggest impairments to water quality in the Chesapeake Bay.

  • Total maximum daily load (TMDL)

    Defines the pollutant load that a water body can acquire without violating water quality standards, and allocates the pollutant loading between contributing point sources and non-point sources.

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