Many of the above are sources of nutrients and pollutants. Nutrients such as nitrogen and phosphorus increase algal growth which will block out light. Aquatic plant growth is reduced by decreased light exposure. Wetlands have the potential to increase water quality. Wetlands prevent some nutrients and pollutants from reaching the stream.
Livestock are a source of nitrates and fecal bacteria that can be harmful to stream health.
Man-Made Structures Dams restrict water flow, which reduces erosion. Entry ramps indicate recreational uses of the waterway such as boating or fishing. Effects of these activities are dependent on the pre-existing condition of the stream. Bridges and piers provide a foreign habitat that may have variable effects. Pipe outfalls indicate a point source.