Following the park and classroom activities, the students will be able to
When rain or snowmelt saturates the ground, the excess water becomes runoff that eventually collects in a stream channel, lake, reservoir, or other body of water. The collection area from where all this water drains is called the drainage basin or watershed. High elevation areas called divides or ridgelines separate watersheds.
The Virginia Department of Game and Inland Fisheries defines 12 major watersheds in Virginia: Big Sandy, Chowan, Clinch, Eastern Shore, Holston, James, New, PeeDee, Potomac-Shenandoah, Rappahannock, Roanoke, and York. In addition there are 497 sub-watersheds, made up of small creeks and streams that flow into larger ones before merging into the major rivers. Five of the major watersheds (60% of Virginia) are part of the larger Chesapeake Bay watershed, which covers 64,000 square miles in six states. Shenandoah National Park, located along the crest of the Blue Ridge Mountains, is at the headwaters of three of these watersheds, the Potomac-Shenandoah, Rappahannock, and James. All the streams that flow out of the park pass through numerous farms, towns, and cities, eventually reaching the Chesapeake Bay and the Atlantic Ocean.
The quality or health of a body of water can be measured by investigating the water chemistry and the types of organisms living in the water. Oxygen content, pH, and mineral content are typical abiotic (non-living) factors that affect water chemistry. pH measures the relative acidity and alkalinity of a substance. pH levels range from 0 (highly acidic) to 14 (extremely alkaline), with 7 being the neutral rating given to distilled water. Most plants and animals prefer a balanced or almost neutral pH level. Dissolved oxygen (DO) is a measure of the water's oxygen content in parts per million (ppm). A DO reading of 5-15 ppm provides ideal conditions for most aquatic organisms and generally indicates a healthy body of water.
Macroinvertebrates are the tiny invertebrate (without backbones) animals that are found in aquatic ecosystems. Examples include such animals as crayfish, mussels, aquatic snails, aquatic worms, and the aquatic larvae of insects such as mayflies, stoneflies, caddisflies, and dragonflies. Many macroinvertebrates require clean, highly oxygenated water to survive. The presence (or absence) of specific macroinvertebrates can indicate the relative health of the water habitat.
Water pollution is caused when harmful chemical or waste materials are discharged or deposited into the water. Point source pollution can be traced to a single source such as a factory or sewage treatment plant while non-point source pollution comes from a variety of sources or over a wide area such as runoff from farmland or city streets. Acid rain, fertilizer runoff, human and animal waste, chemicals, and sediments from erosion can dramatically affect the natural balance of watersheds and alter the water chemistry. Many animals are pollution "sensitive" and are unable to survive when the water conditions change. Irresponsible human actions can have significant impact on the fresh water supply that plants, animals, and people depend on for survival.