The student will investigate and understand the natural processes and human interactions that affect watershed systems. Key concepts include
1. a watershed is composed of the land that drains into a body of water;
2. Virginia is composed of multiple watershed systems which have specific features;
3. the Chesapeake Bay is an estuary that has many important functions; and
4. natural processes, human activities, and biotic and abiotic factors influence the health of a watershed system.

Central Idea: Watershed systems are dynamic and complex; interactions within these systems may influence the overall health of the watershed.

Biotic & Abiotic Factors of Watersheds

All ecosystems, including watershed ecosystems, are affected by complex biotic and abiotic interactions involving exchanges of matter and energy.

• An ecosystem is made up of the biotic (living) community and the abiotic (nonliving) factors that affect it. The health of an ecosystem is directly related to water quality.

• Abiotic factors determine ecosystem type and its distribution of plants and animals as well as the usage of land by people. Abiotic factors include
  • water supply,
  • topography,
  • landforms,
  • geology,
  • soils,
  • sunlight, and
  • air quality/O2 availability.

Monitoring

• Water quality monitoring is the collection of water samples to analyze chemical and/or biological parameters.
• Simple parameters include
  • pH
  • temperature
  • salinity
  • dissolved oxygen
  • turbidity
  • presence of macroinvertebrate organisms

About Watersheds

• A watershed is the land that water flows across or through on its way to a stream, lake, wetland, or other body of water.
  • Areas of higher elevations, such as ridgelines and divides, separate watersheds.
  • The watershed systems in Virginia lead to three main bodies of water. These are the Chesapeake Bay, the North Carolina sounds, or the Gulf of Mexico


Wetlands

• Wetlands form the transition zone between dry land and bodies of water such as rivers, lakes, or bays.
• Both tidal and nontidal wetlands perform important water quality functions, including
  • regulating runoff by storing flood waters;
  • reducing erosion by slowing down run-off;
  • maintaining water quality by filtering sediments, trapping nutrients, and breaking down pollutants; and
  • recharging groundwater
  • Wetlands also provide food and shelter for wildlife and fish and nesting and resting areas for migratory birds.

Estuaries

• Estuaries perform important functions, such as providing habitat for many organisms and serving as nurseries for their young.
  • The Chesapeake Bay is an estuary where fresh and salt water meet and are mixed by tides.
  • It is the largest estuary in the contiguous United States and one of the most productive.
  • Human actions and geologic processes affect the availability of freshwater resources.
  • Human activities can alter abiotic components and thus accelerate or decelerate natural processes