Stormwater is a term used to describe water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt. Stormwater that does not soak into the ground becomes surface runoff, which either flows into surface waterways or is channeled into storm sewers. Runoff flowing into a stormwater drain Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle[1][2]. Runoff that occurs on surfaces before reaching a channel is also called overland flow. ... A storm drain, storm sewer, or stormwater drain (in Australia) system is designed to drain excess rain and ground water from an area. ...

Stormwater is of concern for two main issues - one related to the volume and timing of runoff water (flood control and water supplies) and the other related to potential contaminants that the water is carrying (water pollution). Picture of flooding in Amphoe Sena, Ayutthaya Province, Thailand For other uses, see Flood (disambiguation). ... Water pollution Water pollution is a large set of adverse effects upon water bodies (lakes, rivers, oceans, groundwater) caused by human activities. ...

Because impervious surfaces (parking lots, roads, buildings) do not allow rain to infiltrate into the ground, more runoff is generated than in the undeveloped condition. This additional runoff can erode watercourses (streams and rivers) as well as cause flooding when the stormwater collection system is overwhelmed by the additional flow. Because the water is flushed out of the watershed during the storm event, little infiltrates the soil, replenishes groundwater, or supplies stream base flow in dry weather. This article needs to be wikified. ...

Regulation in United States

In the United States, the EPA is charged with regulating stormwater as part of the Clean Water Act (CWA). Under the CWA, discharges to "Waters of the United States" require National Pollution Discharge Elimination System (NPDES) permits. NPDES permits for point source discharges have been required since the 1970s. In 1987, the CWA was expanded to require NPDES permits for discharges of non-point source discharges such as stormwater runoff. This 1987 expansion was promulgated in two phases - Phase I and Phase II. Phase I required that all municipalities of 100,000 persons or more, industrial dischargers, and construction sites of 5 acres or more have NPDES permits for their stormwater discharges. Phase I permits were issued in much of the U.S. in 1991. Phase II required that all municipalities, industrial dischargers, construction sites of 1 acre or more, and other large property owners (such as school districts) have NPDES permits for their stormwater discharges. Phase II rules came into effect in 2003. EPA redirects here. ... The Clean Water Act, 33 U.S.C.A. § 1251 et seq. ... The Clean Water Act, 33 U.S.C.A. § 1251 et seq. ... It has been suggested that this article or section be merged with Point source (sound), Point source (light), Point source (heat), Point source (radio) and Point source (fluid) (Discuss) A point source of pollution is a single identifiable localized source of air, water, thermal, noise or light pollution. ... A municipality is an administrative entity composed of a clearly defined territory and its population and commonly referring to a city, town, or village, or a small grouping of them. ... Image:Poo construction. ... An acre is an English unit of area, which is also frequently used in the United States and some Commonwealth countries. ... For other uses, see United States (disambiguation) and US (disambiguation). ... A municipality is an administrative entity composed of a clearly defined territory and its population and commonly referring to a city, town, or village, or a small grouping of them. ... Image:Poo construction. ... An acre is an English unit of area, which is also frequently used in the United States and some Commonwealth countries. ... School districts are a form of special-purpose district in the United States (amongst some other places) which serves to operate the local public primary and secondary schools. ...

The goal of the CWA is to restore all "Waters of the United States" to their "fishable" and "swimmable" conditions. Point source discharges, which originate mostly from municipal wastewater (sewage) and industrial wastewater discharges have been regulated for over two decades. Pollutant loadings from these sources are tightly controlled and limited. However, thousands of water bodies in the U.S. remain impaired meaning that they contain pollutants at levels higher than is considered safe by EPA for the intended beneficial use of the water. Wastewater is any water that has been adversely affected in quality by anthropogenic influence. ... Sewage is the liquid water produced by human society which typically contains washing water, laundry waste, faeces, urine and other liquid or semi-liquid wastes. ...

Thus, the last source of pollutants entering these waters is termed polluted runoff, and has been known as non-point source pollution. Daily human activities result in deposition of pollutants on roads, lawns, roofs, farm fields, etc. When it rains or there is irrigation, water runs off and ultimately makes its way to a river, lake, or the ocean. While there is some attenuation of these pollutants before entering the receiving waters, the quantity of human activity results in large enough quantities of pollutants to impair these receiving waters. This article or section does not cite its references or sources. ... For other uses, see Lawn (disambiguation). ... A roof tiled in imitation of thatch at Croyde, north Devon, England Rooftops in Vietnam Snow on the roof The roof, the top covering of a building, is one of the universal structures found on all buildings. ... A typical North American grain farm with farmstead in Ontario, Canada A farm is the basic unit in agriculture. ... Rain falling Rain on an umbrella Rain is a form of precipitation, as are snow, sleet, hail, and dew. ... High-altitude aerial view of irrigation in the Heart of the Sahara ( ) Irrigation is the replacement or supplementation of rainfall with water from another source in order to grow crops or plants. ... Impact of a drop of water. ... River Gambia flowing through Niokolokoba National Park A river is a large natural waterway. ... A man-made lake in Keukenhof, Netherlands A lake is a body of water or other liquid of considerable size surrounded by land. ... Oceans (from Okeanos in Greek) are saline waters that cover almost three quarters (71%) of the surface of the Earth. ... Reduction of signal strength during transmission. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin for wise man or knowing man) under the family Hominidae (the great apes). ...

The 1987 amendments to the CWA were designed to reduce the pollutants that enter the receiving waters from diffuse or non-point sources, aka stormwater.

Many States, such as Texas, California, South Carolina, New York etc., have created their own regulatory agencies to act as an intermediary between the EPA and the local cities and municipalities.

See also

• Impervious surface
• Line source
• Permeable paving
• Sanitary sewer overflow
• Surface runoff
• Best Management Practice

Impervious surfaces are artificial structures, such as pavements and building roofs, which replace naturally pervious soil with impervious construction materials. ... North-South Expressway in Malaysia; a roadway can be considered as a line source of air and noise pollution and need not be a straight line. ... Permeable paving, also called pervious paving or porous pavement, is a term used to describe paving methods for roads, parking lots and walkways that allow the movement of water and air through the paving material. ... Decentralized wet weather overflow event Sanitary sewer overflow (SSO} is a condition whereby untreated sewage is discharged into the environment, escaping wastewater treatment. ... Runoff flowing into a stormwater drain Surface runoff is water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle[1][2]. Runoff that occurs on surfaces before reaching a channel is also called overland flow. ... Best Management Practices (BMP) are actions, which are required by law, to keep soil and other pollutants out of streams and lakes. ...

References

• Ferguson, Bruce K., 1998, Introduction to Stormwater, New York: John Wiley and Sons

External links

• Software for Soakaway and SUDS systems design
• Japan: photo gallery of a large stormwater system
• Toronto: Homeowner's Guide to Rainfall
• How stormwater affects pollution of an urban stream and lake in Syracuse, NY.