View source for Nonpoint source pollution

{{Short description|Pollution resulting from multiple sources}}
[[File:muddy USGS.jpg|thumb|Muddy river polluted by [[sediment]]]]
{{Pollution sidebar|Water}}

'''Nonpoint source''' ('''NPS''') '''pollution''' refers to diffuse [[contamination]] (or [[pollution]]) of water or air that does not originate from a single discrete source. This type of pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. It is in contrast to [[point source pollution]] which results from a single source. Nonpoint source pollution generally results from [[Surface runoff|land runoff]], precipitation, [[Deposition (aerosol physics)|atmospheric deposition]], [[drainage]], [[Soil mechanics#Seepage: steady state flow of water|seepage]], or hydrological modification (rainfall and snowmelt) where tracing pollution back to a single source is difficult.<ref name="epa-nps-overview">{{cite web |title=Basic Information about Nonpoint Source Pollution |url=https://www.epa.gov/nps/basic-information-about-nonpoint-source-nps-pollution |author=<!--Not stated--> |date=2020-10-07 |publisher=US Environmental Protection Agency (EPA) |location=Washington, DC}}</ref> Nonpoint source [[water pollution]] affects a water body from sources such as polluted runoff from [[agricultural]] areas draining into a river, or wind-borne [[debris]] blowing out to sea. Nonpoint source [[air pollution]] affects air quality, from sources such as [[smokestack]]s or car [[tailpipe]]s. Although these [[pollutant]]s have originated from a point source, the long-range transport ability and multiple sources of the pollutant make it a nonpoint source of pollution; if the discharges were to occur to a body of water or into the atmosphere at a single location, the pollution would be single-point.

Nonpoint source water pollution may derive from many different sources with no specific solutions or changes to rectify the problem, making it difficult to  regulate. Nonpoint source water pollution is difficult to control because it comes from the everyday activities of many different people, such as lawn [[fertilizer|fertilization]], applying [[pesticide]]s, [[road construction]] or [[building construction]].<ref name="tceq-nps">{{cite web |url=https://www.tceq.texas.gov/waterquality/nonpoint-source/mgmt-plan/index.html |title=Management Program for Nonpoint Source Water Pollution |author=<!--Not stated--> |date=2017-08-22 |publisher=Texas Commission on Environmental Quality |location=Austin, TX}}</ref> Controlling nonpoint source pollution requires improving the management of urban and suburban areas, agricultural operations, forestry operations and marinas.

Types of nonpoint source water pollution include [[sediment]], [[nutrient]]s, toxic contaminants and chemicals and [[pathogen]]s. Principal sources of nonpoint source water pollution include: urban and suburban areas, agricultural operations, atmospheric inputs, highway runoff, forestry and mining operations, marinas and boating activities. In urban areas, contaminated storm water washed off of [[parking lot]]s, roads and highways, called [[urban runoff]], is usually included under the category of non-point sources (it can become a point source if it is channeled into storm drain systems and discharged through pipes to local surface waters). In agriculture, the leaching out of [[nitrogen]] compounds from fertilized agricultural lands is a nonpoint source water pollution.<ref name="Moss2008">{{cite journal |last1=Moss |first1=Brian |title=Water Pollution by Agriculture |journal=Phil. Trans. R. Soc. Lond. B |date=2008 |volume=363 |issue=1491 |pages=659–666 |doi=10.1098/rstb.2007.2176 |pmc=2610176 |pmid=17666391}}</ref> Nutrient [[surface runoff|runoff]] in [[stormwater|storm water]] from "sheet flow" over an [[agricultural field]] or a forest are also examples of non-point source pollution.    {{TOC limit|3}}

==Principal types (for water pollution)==
===Sediment===
[[Image:Runoff of soil & fertilizer.jpg|thumb|left|[[Surface runoff|Runoff]] of [[soil]] and [[fertilizer]] during a rain storm]]
{| class="wikitable" style="float:right; margin:1em;"
|+Characteristics of point and nonpoint sources of chemical inputs ''(modified from Novonty and Olem 1994)''<ref name="Carpenter, S.R. 1998">{{cite journal |last1=Carpenter |first1=S. R. |last2=Caraco |first2=N. F. |last3=Correll |first3=D. L. |last4=Howarth |first4=R. W. |last5=Sharpley |first5=A. N. |last6=Smith |first6=V. H. |title=Nonpoint Pollution of Surface Waters with Phosphorus and Nitrogen |journal=Ecological Applications |date=August 1998 |volume=8 |issue=3 |pages=559 |doi=10.2307/2641247 |jstor=2641247 |hdl=1813/60811 |hdl-access=free }}</ref>

|'''Point sources'''
{{smalldiv|
* Wastewater effluent (municipal and industrial)
* Runoff and leachate from waste disposal systems
* Runoff and infiltration from animal feedlots
* Runoff from mines, oil fields, unsewered industrial sites
* Overflows of combined storm and sanitary sewers
* Runoff from construction sites less than 20,000 m<sup>2</sup> (220,000&nbsp;ft²)
* Untreated sewage}}
<br>
'''Nonpoint sources'''
{{smalldiv|
* Runoff from agriculture due to fertilizers and pesticides /irrigation
* Runoff from pasture and range
* Urban runoff from unsewered areas
* Septic tank leachate
* Runoff from construction sites >20,000 m<sup>2</sup> (220,000&nbsp;ft²)
* Runoff from abandoned mines
* Atmospheric deposition over a water surface
* Other land activities generating contaminants
}}
|}
[[Sediment]] (loose [[soil]]) includes [[silt]] (fine particles) and [[suspended solids]] (larger particles). Sediment may enter surface waters from eroding stream banks, and from [[surface runoff]] due to improper plant cover on urban and rural land.<ref name="IAfact">Iowa State University. University Extension. Ames, IA. [http://www.extension.iastate.edu/Publications/EDC232A.pdf "Iowa Fact Sheet: Agriculture and Water Quality."] October 2001. Document No. EDC232a.</ref> Sediment creates [[turbidity]] (cloudiness) in water bodies, reducing the amount of light reaching lower depths, which can inhibit growth of submerged [[aquatic plants]] and consequently affect species which are dependent on them, such as [[fish]] and [[shellfish]].<ref>
{{cite report |last1=Stevenson |first1=J. Court |last2=Piper |first2=Catherine B. |last3=Confer |first3=Nedra |date=1979 |title=Decline of Submerged Plants in Chesapeake Bay |url=https://www.fws.gov/chesapeakebay/savpage.htm |publisher=U.S. Fish and Wildlife Service |location=Annapolis, MD |access-date=2017-10-08}}</ref> With an increased sediment load into a body of water, the oxygen can also be depleted or reduced to a level that is harmful to the species living in that area.<ref name="3.Turbidity and sediment dynamics">{{Cite web |title=3.Turbidity and sediment dynamics |url=https://www.ecoshape.org/en/knowledge-articles/sediment-and-ecology-in-delta-lakes/3-turbidity-and-sediment-dynamics/ |access-date=2024-04-23 |website=EcoShape - EN |language=en-US}}</ref> High turbidity levels also inhibit drinking [[water purification]] systems. Sediments are also transported into the [[water column]] due to waves and wind. When sediments are eroded at a continuous rate, they will stay in the water column and the turbidity level will increase.<ref name="3.Turbidity and sediment dynamics"/>

[[Sedimentation]] is a process by which sediment is transported to a body of water. The sediment will then be deposited into the water system or stay in the water column. When there are high rates of sedimentation, flooding can occur due to a build-up of too much sediment. When flooding occurs, waterfront properties can be damaged further by high amounts of sediment being present.<ref>{{Cite web |date=2013-12-30 |title=Sediment in stormwater is a common pollutant which negatively impacts water quality |url=https://www.canr.msu.edu/news/sediment_in_stormwater_is_a_common_pollutant_which_negatively_impacts_water |access-date=2024-04-23 |website=MSU Extension |language=en-us}}</ref>

Sediment can also be discharged from multiple different sources.  Sources include [[construction]] sites (although these are point sources, which can be managed with [[erosion control]]s and [[sediment control]]s), agricultural fields, stream banks, and highly disturbed areas.<ref name="PSUNonpoint">Penn State University. Pennsylvania Lake Erie NEMO. [http://seagrant.psu.edu/publications/fs/Nonpoint_Source_Pollution.pdf "Nonpoint Source Pollution."] {{webarchive|url=https://web.archive.org/web/20110727035540/http://seagrant.psu.edu/publications/fs/Nonpoint_Source_Pollution.pdf |date=2011-07-27 }}.</ref>

===Nutrients===
[[File:Nonpoint Source Pollution.svg|thumb|Nonpoint source pollution is caused when precipitation (1) carries pollutants from the ground such as nitrogen (N) and phosphorus (P) pollutants which come from fertilizers used on farm lands (2) or urban areas (3). These nutrients can cause [[eutrophication]] (4).]]
Nutrients mainly refers to inorganic matter from runoff, [[landfill]]s, [[livestock]] operations and crop lands. The two primary nutrients of concern are phosphorus and nitrogen.<ref name=Ohio>Rob Leeds, Larry C. Brown, Nathan L. Watermeier. [https://web.archive.org/web/20020223144636/http://ohioline.osu.edu/aex-fact/0465.html "Food, Agricultural and Biological Engineering."] Ohio State University Extension Fact Sheet.</ref>

[[Phosphorus]] is a nutrient that occurs in many forms that are [[bioavailable]]. It is notoriously over-abundant in human sewage [[sludge]]. It is a main ingredient in many fertilizers used for agriculture as well as on residential and commercial properties and may become a [[limiting nutrient]] in freshwater systems and some [[estuaries]]. Phosphorus is most often transported to water bodies via [[soil erosion]] because many forms of phosphorus tend to be [[adsorption|adsorbed]] on to soil particles. Excess amounts of phosphorus in aquatic systems (particularly freshwater lakes, reservoirs, and ponds) leads to proliferation of microscopic algae called [[phytoplankton]]. The increase of organic matter supply due to the excessive growth of the phytoplankton is called [[eutrophication]]. A common symptom of eutrophication is [[algae]] blooms that can produce unsightly surface scums, shade out beneficial types of plants, produce taste-and-odor-causing compounds, and poison the water due to toxins produced by the algae. These toxins are a particular problem in systems used for drinking water because some toxins can cause human illness and removal of the toxins is difficult and expensive. Bacterial decomposition of algal blooms consumes dissolved oxygen in the water, generating [[hypoxia (environmental)|hypoxia]] with detrimental consequences for fish and aquatic invertebrates.<ref>{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=Ocean Shorts: NOAA PORTS |url=https://oceanservice.noaa.gov/podcast/june15/os10-hypoxia.html#:~:text=Excess%20nutrients%20in%20the%20water,lead%20to%20hypoxic%20water%20conditions. |access-date=2024-04-23 |website=oceanservice.noaa.gov |language=EN-US}}</ref>

[[Nitrogen]] is the other key ingredient in fertilizers, and it generally becomes a pollutant in saltwater or brackish estuarine systems where nitrogen is a limiting nutrient. Similar to phosphorus in fresh-waters, excess amounts of bioavailable nitrogen in marine systems lead to eutrophication and algae blooms. Hypoxia is an increasingly common result of eutrophication in marine systems and can impact large areas of estuaries, bays, and near shore coastal waters. Each summer, hypoxic conditions form in [[bottom water]]s where the [[Mississippi River]] enters the [[Gulf of Mexico]]. During recent summers, the aerial extent of this "dead zone" is comparable to the area of [[New Jersey]] and has major detrimental consequences for fisheries in the region.<ref>{{Cite web |date=2017-08-02 |title=New Jersey-Size 'Dead Zone' Is Largest Ever in Gulf of Mexico |url=https://www.nationalgeographic.com/science/article/gulf-mexico-hypoxia-water-quality-dead-zone |access-date=2024-04-23 |website=Science |language=en}}</ref>

Nitrogen is most often transported by water as [[nitrate]] (NO<sub>3</sub>). The nitrogen is usually added to a watershed as organic-N or [[ammonia]] (NH<sub>3</sub>), so nitrogen stays attached to the soil until [[oxidation]] converts it into nitrate. Since the nitrate is generally already incorporated into the soil, the water traveling through the soil (i.e., [[interflow]] and [[tile drainage]]) is the most likely to transport it, rather than surface runoff.<ref>{{Cite web |last=Kladivko |first=Eileen |date=2020 |title=Soil drainage and nitrate losses to surface waters: Insights from long-term SEPAC study |url=https://www.extension.purdue.edu/extmedia/AY/AY-399-W.pdf |website=Purdue University}}</ref>

===Toxic contaminants and chemicals===
Toxic chemicals mainly include [[organic compounds]] and [[inorganic compounds]]. Inorganic compounds, including heavy metals like [[lead]], [[mercury (element)|mercury]], [[zinc]], and [[cadmium]] are resistant to breakdown.<ref name="PSUNonpoint"/> These contaminants can come from a variety of sources including human sewage sludge, [[mining]] operations, vehicle emissions, [[fossil fuel]] combustion, urban runoff, industrial operations and landfills.<ref name=Ohio/>

Other toxic contaminants include organic compounds such as [[polychlorinated biphenyls]] (PCBs) and [[polycyclic aromatic hydrocarbons]] (PAHs), fire retardants, and many [[agrochemicals]] like [[DDT]], other pesticides, and fertilizers. These compounds can have severe effects to the ecosystem and water-bodies and can threaten the health of both humans and aquatic species while being resistant to environmental breakdown, thus allowing them to persist in the environment.<ref name="PSUNonpoint"/> These compounds can also be present in the air and water environments, causing damage to the environment and risking harmful exposure to living species.<ref>{{Cite web |title=Air Toxics Effects on Human Health - Air (U.S. National Park Service) |url=https://www.nps.gov/subjects/air/humanhealth-toxics.htm |access-date=2024-04-25 |website=www.nps.gov |language=en}}</ref> These toxic chemicals could come from croplands, nurseries, orchards, building sites, gardens, lawns and landfills.<ref name=Ohio/>

Acids and salts mainly are inorganic pollutants from irrigated lands, mining operations, urban runoff, industrial sites and landfills.<ref name=Ohio/> Other inorganic toxic contaminants can come from foundries and other factory plants, sewage, mining, and coal-burning power stations.

===Pathogens===
[[Pathogens]] are bacteria and viruses that can be found in water and cause diseases in humans.<ref name="PSUNonpoint"/> Typically, pathogens cause disease when they are present in public drinking water supplies. Pathogens found in contaminated runoff may include:<ref>{{Cite journal |last1=Pandey |first1=Pramod |last2=Kass |first2=Phillip |last3=Soupir |first3=Michelle |last4=Biswas |first4=Sagor |last5=Singh |first5=Vijay |date=2014 |title=Contamination of water resources by pathogenic bacteria |journal=AMB Express |volume=4 |issue=51|page=51 |doi=10.1186/s13568-014-0051-x |doi-access=free |pmid=25006540 |pmc=4077002 }}</ref>
* ''[[Cryptosporidium parvum]]''
* ''[[Giardia lamblia]]''
* ''[[Salmonella]]''
* ''[[Norovirus]]'' and other [[virus]]es
* [[Parasitic worm]]s (helminths).
[[Coliform bacteria]] and [[fecal matter]] may also be detected in runoff.<ref name="PSUNonpoint"/>  These [[bacteria]] are a commonly used [[indicator bacteria|indicator]] of water pollution, but not an actual cause of disease.<ref>U.S. Geological Survey. Reston, VA. [http://pubs.usgs.gov/fs/fs-027-01/ "A Primer on Water Quality."] FS-027-01. March 2001.</ref>

Pathogens may contaminate runoff due to poorly managed livestock operations, faulty [[septic system]]s, improper handling of pet waste, the over application of human sewage [[sludge]], contaminated storm sewers, and [[sanitary sewer overflow]]s.<ref name="IAfact"/><ref name="PSUNonpoint"/>

==Principal sources (for water pollution)==

===Urban and suburban areas===
[[Urban Area|Urban]] and [[Suburban|suburban areas]] are a main sources of nonpoint source pollution due to the amount of runoff that is produced due to the large amount of paved surfaces. Paved surfaces, such as [[Asphalt concrete|asphalt]] and [[concrete]] are impervious to water penetrating them. Any water that is on contact with these surfaces will run off and be absorbed by the surrounding environment. These surfaces make it easier for stormwater to carry pollutants into the surrounding soil.<ref name=NOAA>{{cite web |title=Nonpoint Source Pollution |website=National Ocean Service |publisher=U.S. National Oceanic and Atmospheric Administration (NOAA) |url=http://oceanservice.noaa.gov/education/tutorial_pollution/lessons/pollution_tutorial.pdf |location=Washington D.C. |date=2007}}</ref>

Construction sites tend to have disturbed soil that is easily eroded by [[precipitation (meteorology)|precipitation]] like [[rain]], [[snow]], and [[hail]]. Additionally, discarded debris on the site can be carried away by runoff waters and enter the aquatic environment.<ref name=NOAA/>

Contaminated stormwater washed off parking lots, roads and highways, and lawns (often containing [[fertilizer]]s and [[pesticide]]s) is called [[urban runoff]]. This runoff is often classified as a type of NPS pollution. Some people may also consider it a point source because many times it is channeled into municipal storm drain systems and discharged through pipes to nearby [[surface water]]s. However, not all urban runoff flows through [[storm drain]] systems before entering water bodies. Some may flow directly into water bodies, especially in developing and suburban areas. Also, unlike other types of point sources, such as industrial discharges, [[sewage treatment]] plants and other operations, pollution in urban runoff cannot be attributed to one activity or even group of activities. Therefore, because it is not caused by an easily identified and regulated activity, urban runoff pollution sources are also often treated as true nonpoint sources as municipalities work to abate them. An example of this is in Michigan, through a NPS (nonpoint source) program. This program helps stakeholders create watershed management plans to combat nonpoint source pollution.<ref>EGLE (2024). "Nonpoint Source Program". ''Department of Environment, Great Lakes, and Energy''. Retrieved March 30, 2024.https://www.michigan.gov/egle/about/organization/water-resources/nonpoint-source</ref>

Typically, in suburban areas, chemicals are used for lawn care. These chemicals can end up in runoff and enter the surrounding environment via storm drains in the city. Since the water in storm drains is not treated before flowing into surrounding water bodies, the chemicals enter the water directly.{{citation needed|date=March 2024}}

Other significant sources of runoff include [[habitat destruction|habitat modification]] and [[silviculture]] (forestry).<ref>
{{cite report|url=https://www.epa.gov/nps/hydromodification-and-habitat-alteration-national-management-measures|title=National Management Measures to Control Nonpoint Source Pollution from Hydromodification|date=July 2007|publisher=EPA|id=EPA 841-B-07-002}}</ref><ref>{{cite report|url=https://www.epa.gov/nps/national-management-measures-control-nonpoint-source-pollution-forestry|title=National Management Measures to Control Nonpoint Source Pollution from Forestry|date=May 2005|publisher=EPA|id=EPA 841-B-05-001}}</ref>

===Agricultural operations===
Nutrients ([[nitrogen]] and [[phosphorus]]) are typically applied to farmland as commercial [[fertilizer]], animal [[manure]], or spraying of municipal or industrial wastewater (effluent) or sludge. Nutrients may also enter runoff from [[crop residue]]s, [[irrigation]] water, [[wildlife]], and [[Deposition (Aerosol physics)|atmospheric deposition]].<ref name="EPA-agmm">
{{cite report|url=https://www.epa.gov/polluted-runoff-nonpoint-source-pollution/national-management-measures-control-nonpoint-source-0|title=National Management Measures to Control Nonpoint Source Pollution from Agriculture|date=July 2003|publisher=EPA|id=EPA-841-B-03-004}}</ref>{{Rp|p. 2–9}} Nutrient pollution such as nitrates can harm the aquatic environments by degrading water quality by lowering levels of oxygen, which can inturn induce algal blooms and [[eutrophication]].<ref>{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=What is nutrient pollution? |url=https://oceanservice.noaa.gov/facts/nutpollution.html#:~:text=Excessive%20amounts%20of%20nutrients%20can,such%20as%20seagrasses,%20to%20grow. |access-date=2024-04-25 |website=oceanservice.noaa.gov |language=EN-US}}</ref>

Other agrochemicals such as pesticides and fungicides can enter environments from agricultural lands through runoff and deposition as well. Pesticides such as DDT or atrazine can travel through waterways or stay suspended in air and carried by wind in a process known as [[Pesticide drift|"spray drift"]].<ref>{{Cite web |last=Services |first=Department of Health & Human |title=Chemicals and spray drift |url=http://www.betterhealth.vic.gov.au/health/healthyliving/chemicals-and-spray-drift |access-date=2024-04-25 |website=www.betterhealth.vic.gov.au |language=en}}</ref>  [[Sediment]] (loose [[soil]]) washed off fields is a form of [[agricultural pollution]]. Farms with large livestock and poultry operations, such as [[factory farm]]s, are often point source dischargers. These facilities are called "concentrated animal feeding operations" or "feedlots" in the US and are being subject to increasing government regulation.<ref>{{cite web|author=<!--Staff writer(s); no by-line.-->|date=2018-09-20|title=Animal Feeding Operations|url=https://www.epa.gov/npdes/animal-feeding-operations-afos|website=National Pollutant Discharge Elimination System|publisher=EPA}}</ref><ref>Iowa Department of Natural Resources. Des Moines, IA. [http://www.iowadnr.gov/afo/ "Animal Feeding Operations in Iowa."] Accessed March 5, 2009.</ref>

Agricultural operations account for a large percentage of all nonpoint source pollution in the United States. When large tracts of land are [[plow]]ed to grow [[crops]], it exposes and loosens soil that was once buried. This makes the exposed soil more vulnerable to [[erosion]] during [[rainstorm]]s. It also can increase the amount of fertilizer and pesticides carried into nearby bodies of water.<ref name="NOAA" />

===Atmospheric inputs===
{{Cite check|section|date=July 2016}}
Atmospheric deposition is a source of inorganic and organic constituents because these constituents are transported from sources of air pollution to receptors on the ground.<ref name="Colman">Colman, J.A., Rice, K.C., and Willoughby, T.C., 2001, Methodology and significance of studies of atmospheric deposition in highway runoff: U.S. Geological Survey Open-File Report 01-259, 63 p. https://doi.org/10.3133/ofr2001259</ref><ref name="Lopes">Lopes, T.J., Dionne, S.G., 1998, A review of semivolatile and volatile organic compounds in highway runoff and urban stormwater: U.S. Geological Survey Open File Report 98-409, 67 p. https://doi.org/10.3133/ofr98409</ref> Typically, industrial facilities, like [[factory|factories]], emit air pollution via a [[smokestack]]. Although this is a point source, due to the distributional nature, long-range transport, and multiple sources of the pollution, it can be considered as nonpoint source in the depositional area. Atmospheric inputs that affect runoff quality may come from dry deposition between storm events and wet deposition during storm events. The effects of vehicular traffic on the wet and dry deposition that occurs on or near highways, roadways, and parking areas creates uncertainties in the magnitudes of various atmospheric sources in runoff. Existing networks that use protocols sufficient to quantify these concentrations and loads do not measure many of the constituents of interest and these networks are too sparse to provide good deposition estimates at a local scale <ref name="Colman" /><ref name="Lopes" />

===Highway runoff===
Highway runoff accounts for a small but widespread percentage of all nonpoint source pollution.<ref>Gupta, M.K., Agnew, R.W., Gruber, D., and Kreutzberger, W.A., 1981, Constituents of highway runoff, in v. IV, Characteristics of runoff from operating highways—Research report: [https://archive.org/details/constituentsofhi00gupt_1 "Federal Highway Administration Report FHWA/RD–81/045"], 171 p.</ref><ref>Driscoll, E.D., Shelley, P.E., and Strecker, E.W., 1990, Pollutant loadings and impacts from highway stormwater runoff, v. III—Analytical investigation and research report: [https://newengland.water.usgs.gov/dev/g1/DOT/90Model/ "Federal Highway Administration Report FHWA–RD–88–008"], 160 p.</ref><ref>Young, G.K., Stein, Stuart, Cole, Pamela, Kammer, Traci, Graziano, Frank, and Bank, F.G., 1996, Evaluation and management of highway runoff water quality: Federal Highway Administration Report FHWA–PD–96–032, 480 p.</ref><ref>Granato, G.E., Bank, F.G., and Cazenas, P.A., 2003, Data quality objectives and criteria for basic information, acceptable uncertainty, and quality-assurance and quality-control documentation, in Granato, G.E., Zenone, Chester, and Cazenas, P.A., eds., National highway runoff water-quality data and methodology synthesis, v. I—Technical issues for monitoring highway runoff and urban stormwater: [https://newengland.water.usgs.gov/dev/g1/Reports/FHWA-EP03-054.pdf "Federal Highway Administration Report FHWA–EP–03–054"], p. 3–21.</ref><ref>Granato, G.E., and Cazenas, P.A., 2009, Highway-runoff database (HRDB version 1.0)—A data warehouse and preprocessor for the [[Stochastic Empirical Loading and Dilution Model]]: [https://newengland.water.usgs.gov/dev/g1/DOT/FHWA-HEP-09-004/FHWA-HEP-09-004.pdf "Federal Highway Administration Report FHWA–HEP–09–004"] 57 p.</ref><ref>Smith, K.P., and Granato, G.E., 2010, Quality of stormwater runoff discharged from Massachusetts highways, 2005–07: [http://pubs.usgs.gov/sir/2009/5269/ U.S. Geological Survey Scientific Investigations Report 2009–5269], 198 p., with CD–ROM.</ref> Harned (1988) estimated that runoff loads were composed of atmospheric fallout (9%), vehicle deposition (25%) and [[Road#Maintenance|highway maintenance]] materials (67%) he also estimated that about 9 percent of these loads were reentrained in the atmosphere.<ref>Harned, D.A., 1988, Effects of Highway Runoff on Streamflow and Water Quality in the Sevenmile Creek Basin, a Rural Area in the Piedmont Province of North Carolina, July 1981 to July 1982: [https://pubs.er.usgs.gov/publication/wsp2329 "U.S. Geological Survey Water-Supply Paper 2329"] 105 p.</ref>

===Forestry and mining operations===
[[Forestry]] and [[environmental impact of mining|mining]] operations can have significant inputs to nonpoint source pollution.<ref name="US Department of Commerce">{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=Nonpoint Source Pollution, NOS Education Offering |url=https://oceanservice.noaa.gov/education/tutorial_pollution/08forestry.html#:~:text=Forestry%20operations%20such%20as%20logging,increasing%20the%20risk%20of%20erosion. |access-date=2024-04-23 |website=oceanservice.noaa.gov |language=EN-US}}</ref>

====Forestry====
Forestry operations reduce the number of trees in a given area, thus reducing the oxygen levels in that area as well. This action, coupled with the heavy machinery (harvesters, etc.) rolling over the soil increases the risk of [[erosion]].<ref name="US Department of Commerce"/>

====Mining====
Active [[mining]] operations are considered point sources, however runoff from abandoned mining operations contribute to nonpoint source pollution. In [[strip mining]] operations, the top of the mountain is removed to expose the desired [[ore]]. If this area is not properly reclaimed once the mining has finished, [[soil erosion]] can occur. Additionally, there can be chemical reactions with the air and newly exposed rock to create acidic runoff. Water that seeps out of abandoned [[underground mining|subsurface mines]] can also be highly acidic. This can seep into the nearest body of water and change the pH in the aquatic environment.<ref name=NOAA/>

===Marinas and boating activities===
Chemicals used for boat maintenance, like [[paint]], [[solvent]]s, and [[oil]]s find their way into water through runoff. Additionally, spilling fuels or leaking fuels directly into the water from boats contribute to nonpoint source pollution. Nutrient and bacteria levels are increased by poorly maintained sanitary waste receptacles on the boat and pump-out stations.<ref name=NOAA/>

==Control (for water pollution)==
{{Main|Agricultural wastewater treatment|Erosion control}}
[[Image:Contour buffer strips NRCS.jpg|thumb|right|Contour [[buffer strip]]s used to retain soil and reduce [[erosion]]]]

===Urban and suburban areas===
To control nonpoint source pollution, many different approaches can be undertaken in both urban and suburban areas. [[Buffer strip]]s provide a barrier of grass in between impervious paving material like parking lots and roads, and the closest body of water.  This allows the soil to absorb any pollution before it enters the local aquatic system. [[Retention pond]]s can be built in drainage areas to create an aquatic buffer between runoff pollution and the aquatic environment. Runoff and storm water drain into the retention pond allowing for the contaminants to settle out and become trapped in the pond. The use of [[permeable paving|porous pavement]] allows for rain and storm water to drain into the ground beneath the pavement, reducing the amount of runoff that drains directly into the water body. Restoration methods such as [[Constructed wetland|constructing wetlands]] are also used to slow runoff as well as absorb contamination.<ref>{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=Nonpoint Source Pollution, NOS Education Offering |url=https://oceanservice.noaa.gov/education/tutorial_pollution/015controlling.html#:~:text=The%20buffer%20strip%20absorbs%20soil,trapped%20in%20the%20retention%20pond. |access-date=2024-04-23 |website=oceanservice.noaa.gov |language=EN-US}}</ref>

Construction sites typically implement simple measures to reduce pollution and runoff. Firstly, sediment or [[silt fence]]s are erected around construction sites to reduce the amount of sediment and large material draining into the nearby water body.  Secondly, laying grass or straw along the border of construction sites also work to reduce nonpoint source pollution.<ref name=NOAA/>

In areas served by single-home septic systems, local government regulations can force septic system maintenance to ensure compliance with water quality standards. In [[Washington (state)]], a novel approach was developed through a creation of a "shellfish protection district" when either a commercial or recreational shellfish bed is downgraded because of ongoing nonpoint source pollution. The shellfish protection district is a geographic area designated by a county to protect water quality and tideland resources, and provides a mechanism to generate local funds for water quality services to control nonpoint sources of pollution.<ref>{{cite web|url=http://psparchives.com/restore-habs/|title=Restore Habitat|date=10 April 2018|website=Marine|access-date=19 April 2018}}</ref> At least two shellfish protection districts in south [[Puget Sound]] have instituted septic system operation and maintenance requirements with program fees tied directly to property taxes.<ref>{{cite web|url=http://www.co.thurston.wa.us/health/ehrp/nisqually.html |title=PHSS HomeA-Z TopicsPrograms/Serv |publisher=Co.thurston.wa.us |access-date=2014-01-14}}</ref>

===Agricultural operations===
To control sediment and runoff, farmers may utilize erosion controls to reduce runoff flows and retain soil on their fields. Common techniques include [[contour plowing]], crop [[mulch]]ing, [[crop rotation]], planting [[perennial]] crops, or installing [[riparian buffer]]s.<ref name="EPA-agmm" />{{rp|pp. 4-95–4-96}}<ref>U.S. Natural Resources Conservation Service (NRCS). Fort Worth, TX. [ftp://ftp-fc.sc.egov.usda.gov/NHQ/practice-standards/standards/330.pdf National Conservation Practice Standard: Contour Farming."]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}} Code 330. June 2007.</ref><ref>NRCS. [ftp://ftp-fc.sc.egov.usda.gov/NHQ/practice-standards/standards/484.pdf National Conservation Practice Standard: Mulching."]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}} Code 484. September 2008.</ref> ''[[Conservation tillage]]'' is a concept used to reduce runoff. The farmer leaves crop residues from previous plantings on and in the ground to help reduce splash and sheet erosion.<ref name=NOAA/>

Nutrients are typically applied to farmland as commercial fertilizer; animal [[manure]]; or spraying of municipal or industrial wastewater (effluent) or sludge. Nutrients may also enter runoff from [[crop residue]]s, [[irrigation]] water, [[wildlife]], and [[Deposition (Aerosol physics)|atmospheric deposition]].<ref name="EPA-agmm" />{{rp|p. 2–9}} Farmers can develop and implement [[nutrient management]] plans to reduce excess application of nutrients.<ref name="EPA-agmm" />{{rp|pp. 4-37–4-38}}<ref>NRCS. [ftp://ftp-fc.sc.egov.usda.gov/NHQ/practice-standards/standards/590.pdf "National Conservation Practice Standard: Nutrient Management."]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}} Code 590. August 2006.</ref>

To minimize pesticide impacts, farmers may use [[Integrated Pest Management]] (IPM) techniques (which can include [[biological pest control]]) to maintain control over pests, reduce reliance on chemical pesticides, and protect [[water quality]].<ref>NRCS. [ftp://ftp-fc.sc.egov.usda.gov/NHQ/practice-standards/standards/595.pdf National Conservation Practice Standard: Pest Management."]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}} Code 595. July 2008.</ref><ref>EPA. [http://www.epa.gov/opp00001/factsheets/ipm.htm "Integrated Pest Management Principles."] March 13, 2008.</ref>

===Forestry operations===
With a well-planned placement of both logging trails, also called skid trails, can reduce the amount of sediment generated. By planning the trails location as far away from the logging activity as possible as well as contouring the trails with the land, it can reduce the amount of loose sediment in the runoff. Additionally, by replanting trees on the land after logging, it provides a structure for the soil to regain stability as well as replaces the logged environment.<ref name=NOAA/>

===Marinas===
Installing shut off valves on fuel pumps at a marina dock can help reduce the amount of spillover into the water. Additionally, pump-out stations that are easily accessible to boaters in a marina can provide a clean place in which to dispose of sanitary waste without dumping it directly into the water. Finally, something as simple as having trash containers around a marina can prevent larger objects entering the water.<ref name=NOAA/>

== Country examples ==

=== United States ===
{{Further|Water pollution in the United States}}Nonpoint source pollution is the leading cause of [[water pollution in the United States]] today, with polluted runoff from agriculture and [[hydromodification]] the primary sources.<ref name="EPA-2004-wq-report">{{cite report|url=https://www.epa.gov/waterdata/2004-national-water-quality-inventory-report-congress|title=National Water Quality Inventory: Report to Congress; 2004 Reporting Cycle|date=January 2009|publisher=EPA|id=EPA 841-R-08-001}}</ref>{{rp|15}} <ref name="EPA-agmm" />

==== Regulation of Nonpoint Source Pollution in the United States ====
{{Further|Nonpoint source water pollution regulations in the United States}}

The definition of a nonpoint source is addressed under the U.S. [[Clean Water Act]] as interpreted by the [[U.S. Environmental Protection Agency]] (EPA). The law does not provide for direct federal regulation of nonpoint sources, but state and local governments may do so pursuant to state laws. For example, many states have taken the steps to implement their own management programs for places such as their coastlines, all of which have to be approved by the [[National Oceanic and Atmospheric Administration]] and the EPA.<ref>{{cite web|last1=Department of Commerce|title=Coastal Nonpoint Pollution Control Program: Approval Decision on California Coastal Nonpoint Pollution Control Program|url=https://www.govinfo.gov/content/pkg/FR-2000-05-01/pdf/00-10778.pdf|website=GovInfo|publisher=Federal Register}}</ref> The goals of these programs and those alike are to create foundations that encourage statewide pollution reduction by growing and improving systems that already exist.<ref>{{cite web|last1=McCarthy|first1=Carolyn|title=Nonpoint Pollution Control Program|url=https://www.govinfo.gov/content/pkg/CREC-2000-02-09/pdf/CREC-2000-02-09-pt1-PgE100-3.pdf|website=GovInfo|publisher=Congressional Record}}</ref> Programs within these state and local governments look to [[Best management practice for water pollution|best management practices]] (BMPs) in order to accomplish their goals of finding the least costly method to reduce the greatest amount of pollution. BMPs can be implemented for both agricultural and urban runoff, and can also be either structural or nonstructural methods. Federal agencies, including EPA and the [[Natural Resources Conservation Service]], have approved and provided a list of commonly used BMPs for the many different categories of nonpoint source pollution.<ref>{{cite web|title=Handbook for Developing and Managing Tribal Nonpoint Source Pollution Programs Under Section 319 of the Clean Water Act|url=https://permanent.access.gpo.gov/gpo11965/tribal-handbook2010.pdf)|publisher=EPA}}</ref>

==== U.S. Clean Water Act provisions for states ====
Congress authorized the CWA section 319 grant program in 1987. Grants are provided to states, territories, and tribes in order to encourage implementation and further development in policy.<ref>{{Cite web|date=2019-12-04|title=319 Grant Program for States and Territories|url=https://www.epa.gov/nps/319-grant-program-states-and-territories|website=Polluted Runoff: Nonpoint Source Pollution|publisher=EPA}}</ref> The law requires all states to operate NPS management programs. EPA requires regular program updates in order to effectively manage the ever-changing nature of their waters, and to ensure effective use of the 319 grant funds and resources.<ref>{{Cite web|date=2013|title=Nonpoint Source Program and Grants Guidelines for States and Territories|url=https://www.epa.gov/sites/production/files/2015-10/documents/319-guidelines-fy14.pdf|publisher=EPA}}</ref>

The Coastal Zone Act Reauthorization Amendments (CZARA) of 1990 created a program under the [[Coastal Zone Management Act]] that mandates development of nonpoint source pollution management measures in states with coastal waters.<ref>{{Cite web|title=Coastal Nonpoint Program|url=https://coast.noaa.gov/czm/pollutioncontrol/media/6217progguidance.pdf|url-status=dead|archive-url=https://web.archive.org/web/20170502010936/https://coast.noaa.gov/czm/pollutioncontrol/media/6217progguidance.pdf|archive-date=2017-05-02|access-date=2019-03-05}}</ref> CZARA requires states with coastlines to implement management measures to remediate water pollution, and to make sure that the product of these measures is implementation as opposed to adoption.<ref>{{Cite web|title=Nonpoint Source Pollution Control Program|url=https://www.waterboards.ca.gov/water_issues/programs/nps/plans_policies.html|access-date=2019-03-05|publisher=California State Water Resources Control Board}}</ref>

==See also==
{{Portal|Water|Environment}}
*[[Fertilizer runoff|Agricultural nutrient runoff]]
*[[stochastic empirical loading and dilution model]]
*[[Trophic state index]] (water quality indicator)
*[[Surface-water hydrology]]
*[[Water quality]]
*[[Water quality modelling]]

==References==
{{Reflist|30em}}

==External links==
* [https://www.epa.gov/nps US EPA – Nonpoint Source Management Program]

{{marine pollution}}
{{pollution}}

[[Category:Agricultural soil science]]
[[Category:Environmental soil science]]
[[Category:Environmental science]]
[[Category:Water pollution]]