Watersheds, also known as drainage basins, are areas of land that drain into a common body of water, such as a lake, river or stream. As water travels over the land’s surface—it may pass through farm fields, forests, lawns and city streets—on its course to a waterway. Or the water may seep into the soil and travel as groundwater. Either way, the water body is impacted by what happens, good or bad, in the watershed. And, that water body could be the source of that community’s drinking water supply.
If we take a closer look at the types of pollutants that can impact a watershed, most can be categorized as either point or nonpoint source pollution.
Point source Pollution: This is where you can literally point to and confirm the origin of the pollution. A leaking sewer pipe releasing effluent into a river, for example, is a specific, identifiable source of pollution and is considered point source pollution.
Nonpoint source Pollution: This type of pollution comes from a wide area and no single location is the point of origin. For example, during the spring, several homeowners in the same development spread fertilizer on their lawns. A heavy rain washes the excess fertilizer into a storm drain, which carries it to a stream. Other examples could include litter, grass clippings, animal waste and road salt. Many of these items are not intentionally placed into the aquatic ecosystem, which is why it’s important to build awareness and identify ways we can reduce our impacts on the watersheds in which we live.
Water pollutants can further be classified into eight main categories: organic pollutants, inorganic pollutants, thermal pollution, plant nutrients, sediment, radioactive contaminants, infectious agents and oxygen consuming wastes. Remediation efforts and techniques will depend on the origin of the pollution, as well as the pollutant type. Oftentimes, addressing water pollutants requires a combination of enforcement, education and technology.