Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants (which are discrete sources), comes from many diffuse sources. NPS pollution is caused by rainfall, snowmelt or other runoff moving over and through the ground. As the runoff moves, it picks up and carries away natural and human - made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our under ground sources of drinking water. These pollutants include:
NPS pollution can come from both rural and urban areas. In rural areas, the causes tend to be primarily large-scale changes to the landscape, land use and hydrology caused by such operations agriculture and logging. In urban areas, population densities, combined with water-hungry non-natural landscaping and much of the rest of the land covered by impervious surfaces causes constant surface water flows that carry pollutants to inland water bodies and the ocean.
What can be done to lessen NPS pollution? For new development and significant redevelopment, we can utilize Low Impact Development techniques to design smarter to use less water, generate less runoff, and retain and reuse runoff water that is generated. We can create Ocean Friendly Gardens that require less water, fertilizers, and other chemicals.
On a personal basis, we can all do things like:
These and other tips on how to reduce NPS pollution and keep our oceans and beaches clean, can be found in Surfrider Foundation's brochure 20 Ways to Cleaner Oceans, Waves and Beaches (pdf).
Another source of information is EPA's NPS website.