Watershed Systems

Health of Ecosystems

  • Factors that can affect health:

  • Ecosystems contain abiotic and biotic factors that affect water quality

    • Biotic factors are living, including organisms

    • Abiotic factors are nonliving

      • Sunlight

      • Soil

      • Water supply

      • Topography

      • Soils

      • Dissolved oxygen

      • Air quality

      • Salinity

      • Water chemistry

Many environmental processes are natural, but humans can alter these natural processes:

  • release pesticides/herbicides/fertilizers and alter the chemicals in the ecosystem

  • flood protection/wetland loss

  • plowing fields (accelerates erosion)

  • planting trees (slows erosion)


  • What are watersheds?

    • Land that water flows across or through on its way to a stream, lake, wetland, or other body of water

    • Areas of high elevation, like ridgelines and divides, separate watersheds

    • Arrangements of river systems

  • VA’s Watersheds

    • 3 major regional watershed systems lead to:

      • Chesapeake Bay (pictured on left)

        • 6 States (New York, Penn., Maryland, Delaware, West Va., Virginia)

        • 6 Major river systems

          • Susquehanna River

          • Shenandoah River

          • Potomac River

          • Rappahannock River

          • York River

          • James River

      • North Carolina sounds

      • Gulf of Mexico

Rivers and Tributaries

  • River systems are made up of tributaries of smaller streams that join along

  • What are tributaries?

    • Tributaries are rivers or streams that enters a larger body of water, especially a lake or river

  • Rivers and streams generally have wide, flat, border areas, called flood plains (water spills out at times of high flow)

  • Rivers and streams carry and deposit sediment


  • transition zone between dry land and bodies of water (rivers, lakes, or bays)

  • regulate runoff by storing flood waters

  • reduce erosion by slowing down run-off

  • maintain water quality by filtering sediments, trapping nutrients, and breaking down pollutants

  • recharge groundwater

  • provide food, shelter for wildlife

  • provide nesting and resting areas for migratory birds


  • Saltwater and freshwater mix (water is called “brackish”)

  • provide habitat for many organisms and serve as nurseries

  • Example: Chesapeake Bay - largest estuary in the contiguous United States (and one of the most productive) - covers 60% of VA

  • Estuaries can also be called bays, lagoons, harbors, inlets, or sounds

  • Humans rely on estuaries for recreation, tourism, fisheries, and transportation

  • Support communities of organisms

Chesapeake Bay

Conservation and Water Quality

  • Monitoring water quality is an important way for scientists to determine ecosystem and watershed health

    • Scientists collect water samples to analyze chemical and/or biological parameters

    • Parameters include (there are many more):

      • pH, temperature

      • salinity

      • dissolved oxygen

      • turbidity (cloudiness)

      • presence of macroinvertebrate organisms

      • Chemical components and nutrients

  • Many governmental and local efforts to conserve watershed ecosystems (like the Chesapeake Bay)

  • Ways to help: advocacy, working with educational programs, litigation/laws, restoration, and volunteers picking up trash

Pollution and Safety Issues

  • Nonpoint Source Pollution - does not result from a single location

    • Examples: runoff, drainage or seepage, when rainfall carries contaminants, such as fertilizers and pesticides, oils, grease and trash to bodies of water

  • Point Source Pollution - pollution that flows from pipes or comes from specific points

    • Examples: industrial plants, sewage treatment plants, storm water drains, pipes

  • This damages both human health and the health of organisms in these bodies of water, compromising safety and water quality


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