What is Nonpoint Source Pollution?

Nonpoint source (NPS) pollution comes from many diffuse sources. Rainfall or snowmelt moving over and through the ground causes NPS pollution. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, streams, wetlands and introducing them to ground water.

These pollutants include:

• Excess fertilizers, herbicides, and insecticides from both agricultural lands and residential areas
• Oil, grease, and toxic chemicals from urban areas
• Sediment from poorly managed construction sites, agricultural and forest lands, and eroding stream banks
• Salt from crop irrigation
• Acid drainage from abandoned mines
• Bacteria and nutrients from agriculture, pet wastes and poorly maintained septic systems
• Adverse changes to the vegetation, shape and flow of rivers and streams

According to the U.S. Environmental Protection Agency, NPS pollution is the leading remaining cause of water quality problems. The effects of nonpoint source pollutants on specific waters vary and may not always be fully quantified. However, it is known that these pollutants have harmful effects on drinking water supplies, recreation, fisheries, and wildlife.

Simple household activities can have a negative impact on water quality, such as

• Improperly disposing of motor oil and other automobile products
• Overusing lawn and garden chemicals
• Leaving pet waste on the ground

These urban and suburban sources of NPS pollution contribute to urban polluted runoff. In a 1998 survey of the nation’s water resources, the U.S. Environmental Protection Agency found that when rivers and streams are impaired, 11% of the environmental damage comes from urban polluted runoff. When lakes and reservoirs are impaired, it accounts for 12% of the decline in water quality.