A watershed is the area of land where precipitation drains to a stream, river, lake, or ocean. For example, the Lost River watershed in Hardy County is the entire area of land that feeds rain and melted snow into the Lost River. Things like the type of bedrock, steepness of the slopes, amount of precipitation, size of the watershed, and human activities can affect how clean the water is, how much water is available, and what kind of fish are in the stream.

A watershed has many parts, and in Watershed Creator, the user builds a watershed by matching the parts of the watershed with their functions.

Many Animals live in our Potomac watersheds. The list includes deer, cattle, squirrels, turkeys, rabbits, owls and many more mammals and birds. It also includes insects, fish, worms, and many other creatures. All of these animals play an important role in a watershed. They help cycle nutrients by eating and digesting plants and each other. They help mix our soil by burrowing. They support culturally and economically important hunting, fishing, and raising livestock. They can also have negative impacts if, for example, they overgraze land and leave it open to erosion. Erosion is especially serious when it occurs near streams because soil and other pollutants are easily washed into streams during a storm.

An Aquifer is the zone of the soil and bedrock that is saturated with water. The top of the aquifer is called the water table. An aquifer can be right at the surface, as in a wetland, or you may have to dig many hundreds of feet down to find water. And just because the underground is saturated does not mean that there is a lot of good water. Most of our Potomac aquifers are located in bedrock, but sometimes the bedrock is so dense it does not have much room to store water. Other times, the bedrock contains minerals like sulfur and iron that make the water taste bad and can require expensive treatment to make the water usable. Water in aquifers supplies all of our drinking water taken from springs and wells, and much of the water flowing in our streams.

Bedrock is the consolidated rock underlying the soil. The bedrock can be far underground below deep soils in valley bottoms, or can be at or near the surface on the top of steep slopes. Rock is broken down into smaller particles, or "weathered," by water, wind and vegetation. These particles are the "parent material" for the soil - the zone where vegetation gets water, plant roots take hold, and microorganisms break down vegetable matter. The type of bedrock in a watershed, such as sandstone, shale, or limestone, has an important effect on the composition of the soils. Have you ever had sulfur or iron in your water? This happens because water reacts chemically with the mineral particles in bedrock, and the chemical makeup of the bedrock influences water quality.  Most of our Potomac Highland aquifers are found in bedrock.

Precipitation is the total annual amount of rain or snow. The amount of precipitation in a given watershed affects: 1) how much water is available for use; 2) what kinds of vegetation are able to live there; and 3) many other characteristics of a watershed. This makes precipitation a major factor in determining what a watershed looks like.  In the Potomac Highlands most of the water flowing into and out of a given aquifer probably comes from precipitation that fell in that watershed.

Soil is the loose mineral matter covering the ground. The top layers of soil include both minerals and organic matter (decayed plants and animals). It is influenced primarily by the type of bedrock underlying it, climate, microorganisms, vegetation, and topography. Many plants depend on soil for support, water, and as a source of nutrients. Microorganisms in the soil also destroy contaminants in the water passing through it, thus helping to cleanse the water before it enters the aquifer or a stream.

A Stream is a body of surface water that moves downhill in a more-or-less distinct channel. Streams reshape watersheds by eroding the land, carrying sediment downstream and depositing sediment on the stream bottom and floodplain. Perennial streams flow constantly, while intermittent streams flow during wet periods. Streams in the Potomac Highlands get much of their water from the underground aquifer, particularly during dry periods. In fact, most of our streams are called "out-flow streams" because ground water is flowing out to them. Streams are important to people in West Virginia because they provide water to use for drinking, farming, industry, and recreation. Our streams also produce income through tourism, and provide drinking water for downstream states like Maryland and Virginia.

In the Potomac Highlands, Vegetation in a watershed can vary a lot. Trees like willows and sycamores that grow right beside a stream are tolerant of wet soils and periodic flooding. Trees on top of the ridges, like chestnut oak and table mountain pine, are tolerant of drought since at higher elevations there is less soil to hold moisture. Regardless of the type of vegetation, plant roots help hold soil in place, thereby reducing erosion and protecting streams from the harmful process of "sedimentation." Vegetation can also filter dirt and other pollutants out of surface runoff and absorb some pollutants in groundwater through their roots. Dead plants provide most of the organic matter in soil. Dead plants are decomposed by microorganisms in the soil and turned into humus--a part of soil that boosts fertility and water holding capacity.