What is a Watershed?
A watershed is an area of land that water flows across and through on its way to a stream, river, or some other common body of water. Any rain that falls on the land in this area is drained to this common waterway.
We all live in a watershed. How big or how small that watershed is depends on the topography of the land, or how hilly it is. Typically a watershed boundary is determined by finding the highest points of the land that surround the common body of water mentioned above. Any and all smaller waterways between the high points and the major body of water are part of one watershed, because they drain into it as a result of the lay of the land, so to speak.
Everything we do has an effect on the quality of water in our watershed and vice versa, the quality of water in our area has a direct impact on us. Consider this: anoxic conditions (conditions where oxygen levels in the water is low) in a major water system down the road from you is causing unnatural plant growth in the water. It is green and it is filling up the waterway very quickly. On days when the wind is just right, the smell of this plant growth flows right in through your kitchen window. Not only that. Your neighbour, who is an enthusiastic fisher, says he can’t fish in that water anymore. There are no more trout to be had. The condition of the water (low levels of oxygen) has destroyed it as a good habitat for trout, as they need cool waters with high levels of oxygen.
In this case the quality of the water has affected both you, with the foul smell entering your house; your neighbour, with the inability to enjoy his annual fishing trips; and the wildlife that share the watershed with you, due to the loss of good habitat in which the trout can live.
Watersheds are important for a number of reasons:
- Drinking water
- Wildlife habitat
- Irrigation for farmers’ crops and for livestock
- Industry
- Recreation
- Natural beauty
Threats to a Watershed
Now that we know why watersheds are important, let’s consider what threatens watersheds. In other words, what can affect the health of our water?
- Land alterations
- Anything we do to the land will affect the water, either how it flows or what flows into it (IE. Pollutants)
- Urbanization
- With construction of new homes and businesses comes the removal of vegetation (trees, shrubs, and other plant life). This is often replaced with hard surfaces such as asphalt, sidewalks, and driveways which further alters the flow of water within a watershed. Well-planned development takes into account the health of the environment overall and can lessen some of these effects on the land and the water within it.
- Land-based water pollution
- Litter, pesticides, fertilizers, and sewage are just some of the ways in which people can pollute surrounding waterways. Surface and ground water carry these pollutants throughout the watershed and build-up of them can have serious side effects on humans and wildlife.
- Vegetation removal
- Removing trees and shrubs near waterways has the most serious effect on a watershed. These areas directly next to water are called riparian zones. Riparian zones are the most important areas for wildlife because they provide cover, water, food, and nesting sites. Riparian zones are also important for the waterway itself. They trap silt and other hard particles as surface water passes through them, working as a filter to remove these substances before the remaining water drains into the stream, river or other waterway that they protect.
- Altering the water flow
- Dams, either natural or man-made alter the flow of water. This can affect temperature and oxygen levels on the downstream side of the dam.
- Agricultural practices
- Pesticides, fertilizers, removal of trees and shrubs near waterways, and livestock contaminating waterways with feces are all examples of agricultural practices that can seriously harm the health and quality of the watershed.