An example of nonpoint source pollution would be rainfall or snowmelt picking up natural or anthropogenic pollutants and depositing them into water resources. In towns and cities where much of the land is covered by impervious surfaces (such as parking lots, sidewalks, rooftops, and driveways) water will flow into storm drains that carry the water directly to your local streams or lakes. This is referred to as urban stormwater.
Construction or logging efforts can cause a significant increase of sediment in nearby waterways. The removal of vegetation exposes soil and without vegetation to take-up water there is a greater erosion potential. Suspended solids (turbidity) from erosion prevents sunlight from reaching aquatic plants. Without light photosynthesis cannot take place, which may reduce the amount of dissolved oxygen in the water. Dissolved oxygen is vital for fish and other aquatic life. Sediment absorbs heat, so if there are a lot of suspended sediments the temperature of the surface water can rise. Turbidity can also make it hard for fish to see their prey. Heavy loads of suspended solids can even clog fish gills and filter-feeding devices of aquatic macroinvertebrates (water bugs). As solid matter settles, it may cover and harm plants and animals and spawning beds.
There is currently no federal enforcement for nonpoint source pollution. Nonpoint source pollution is primarily controlled by state, tribal, or local agencies that develop management programs. Many of these programs use Best Management Practices (BMPs), which are technical on-the-ground controls that can reduce nonpoint source pollution. An example of a BMP would be creating a vegetation buffer between an animal feeding operation and a stream. The vegetation can help take-up and filter nonpoint source pollutants like nutrients and sediments.