A watershed is a section of land, which collects water from local springs, rain, hail and snow. It can be as small as a few acres or as large as one million square miles, such as the Mississippi River valley. A countryside of rolling hills in Kansas, a forest in northern Pennsylvania, a marshy land in southern Louisiana or a high desert, scrub oak hillside in northern New Mexico are all watersheds.

The water which collects is filtered through trees, bushes, plants, grasses and soil, thus cleansing it of pollutants. This vegetation also decreases the contact force of rain or hail on the soil so as to reduce soil erosion. The water continues its downward movement into underground water supplies that feed the local vegetation and into lowland streams. It eventually empties into rivers, lakes and oceans.

Watersheds are seen as areas that need to be protected because, to their neighboring communities, they are the primary source of drinking water. They are rendered ineffective when too much vegetation is removed either through natural or mechanical forces. The soil looses a percentage of its porosity and water runs off the top rather than filtering down. This erodes the soil, decreasing the amount of purified water available as well as adversely affecting the biodiversity of the area.

The health of a watershed is vital because of several factors:

• The leaves of trees, bushes and plants protect the soil from the harsh impact of rain or hail, thus decreasing erosion potential.

• Their roots provide a means of stability to the soil also decreasing erosion potential.

• Roots of trees, bushes, plants and grasses increase the porosity of the soil, allowing water to filter down into the soil. This enables the soil to be a storage tank, which allows for slower release into the ground water system and to the surrounding plants. In conjunction with biological processes, it is also a means of filtering out pollutants, thus providing drinking water for that area.