Streams and Pollution:
Getting to the Source
Thousands of years ago, rivers flowed through the land mostly unaffected by human activities. As more people settled, we impacted the quality of the water, and continue to do so today. It is surprising (and maybe shocking!) to realize how many pollutants actually reach the streams and rivers as a result of our activities.
To help us reduce the amount of pollutants getting into the river we first need to understand what actually enters the water. Some pollutants are easier to identify and much easier to control than others. We describe the way that pollutants reach the river as
either point source or non-point source pollution.
Point-source pollution typically comes from one source, so the type and volume of pollutants is known. A point source pollutant is often easily identified because there is a discharge pipe that drains into the water. An example of point source pollution is an outflow pipe from an industrial plant or sewage treatment plant. Point source pollutants are much easier to regulate than non-point sources because we know the source, the type and the volume.
The more mysterious form of pollution is called non-point source pollution. This type can occur anywhere along the river from widespread activities that originate from more than one place. As rainfall and snowmelt move over and through the ground, the runoff picks up and carries away natural and human-made pollutants. These pollutants are then deposited into
wetlands, lakes and rivers. Examples of these pollutants include salt, oil and gas residue from roads, household and agricultural fertilizers, and runoff from feedlots. Because it is difficult to identify the type of pollutant, the volume, or even the origin, non-point source pollutants are very difficult to manage and can have a significant impact on water quality.
Reprinted from Stream Connections with permission of Alberta