| Background | |||
 |
Non-point source pollution includes sources of pollution such as general runoff of sediments, fertilizer, pesticides, trash and other materials from farms and urban areas as opposed to specific points of discharge, such as pipes or outfalls. Non-point source pollution is most associated with pollution resulting from rainfall, snowmelt or other forms of precipitation moving over land surfaces or through the ground. |
 |
|
As this water moves, it gathers all forms of pollution, natural and human-made, that may be in its path and carries them into our streams, creeks, lakes, rivers wetlands, oceans and even underground drinking water supplies.
Non-point source pollution can exist in an urban setting as well as a rural setting. In an urban setting, some major sources of non-point source pollution are mainly related to the amount of paved surfaces in that setting. Impermeable (not allowing water to pass through) surfaces reduce the amount of precipitation that is allowed to slowly filter through soil into groundwater supplies. This increases the amount of surface water in our systems. Elevated amounts of water in surface water systems create increased levels of bank erosion and the subsequent sedimentation that results. As these impervious surfaces are heated by the sun, precipitation that falls on them is also heated, creating thermal pollution entering surface water systems, which can be lethal to many species of macro-invertebrates, fish and other aquatic species. Other sources of non-point source pollution in an urban setting are the lawn fertilizers and garden pesticides that exist around homes, oil and gas that leak or spill from our automobiles and other gas-powered tools, trash and litter, and bacteria and other pollutants resulting from improperly functioning septic systems.
Agricultural non-point source pollution is caused less by the amount of impervious surfaces in surrounding areas than by the nutrients - ammonia, nitrogen and phosphorous - associated with agricultural practices. Livestock with unrestricted access to waterways or drainage from holding pens is a major source of nutrients. Also, excess fertilizers and pesticides applied to crops can impair streams, creeks, lakes and rivers. Crop fields that extend right to the banks of a waterway can make the banks more susceptible to bank erosion due to the lack of root structure, thus causing increased sedimentation, which is harmful to fish and aquatic macro-invertebrate habitat. Pollutants that exist in an urban setting such as oil and gas leaked or spilled from automobiles and trash and litter can also be found in an agricultural setting.