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Water glossary



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Water Glossary - N

  • NAPLS: Nonaqueous phase liquids; i.e., chemical solvents such as trichloroethylene (TCE) or carbon tetrachloride – often toxic. Many of the most problematic NAPLs are DNAPLs – dense nonaqueous phase liquids.

  • Natural flow: The rate of water movement past a specified point on a natural stream. The flow comes from a drainage area in which there has been no stream diversion caused by storage, import, export, return flow, or change in consumptive use caused by man-controlled modifications to land use. Natural flow rarely occurs in a developed country.

  • Natural resource: Any form of matter or energy obtained from the environment that meets human needs.

  • Navigable waters: Traditionally, waters sufficiently deep and wide for navigation by all, or specific sizes of, vessels.

  • Navigational water use: Water utilized as a means of commercial (and sometimes recreational) transportation. Includes water used to lift a vessel in a lock, or maintain a navigable channel level. Navigational water use is considered a nonconsumptive instream use of water and is generally not measured.

  • Net water use: Water withdrawals plus or minus water transfers. In most counties, the net water use and water withdrawals are equal. However, in counties involved in water transfers (imports and exports), the net water use represents the actual amount of water used regardless of the amount of water withdrawn.

  • Neutralization: The addition of substances to neutralize water, so that it is neither acid, nor basic. Neutralization does not specifically mean a pH of 7.0, it just means the equivalent point of an acid-base reaction.

  • Neutron probe: Type of probe used to monitor soil moisture conditions to help determine when water should by applied.

  • Neutrons: Uncharged building blocks of an atom that play a part in radio-activity. They can be found in the nucleus.

  • NIPDWR: National interim primary drinking water regulations.

  • Nitrification: A biological process, during which nitrifying bacteria convert toxic ammonia to less harmful nitrate. It is commonly used to remove nitrogen substances from wastewater, but in lakes and ponds it occurs naturally.

  • Nitrogen: A plant nutrient that can cause an overabundance of bacteria and algae when high amounts are present, leading to a depletion of oxygen and fish kills. Several forms occur in water, including ammonia, nitrate, nitrite or elemental nitrogen. High levels of nitrogen in water are usually caused by agricultural runoff or improperly operating wastewater treatment plants. Also see phosphorous.

  • Non-Community water system: A public water system which provides piped water for human consumption to at least 15 service connections or which serves at least 25 individuals at least 60 days out of the year but which is not a community water system. The difference between a community water system and a non-community water system is that the former serves inhabitants whereas the latter serves transients or non-residents who other wise do not inhabit the building served by the system.

  • Nonconsumptive use: Using water in a way that does not reduce the supply. Examples include hunting, fishing, boating, water-skiing, swimming, and some power production. Compare consumptive use.

  • Noncontact recreation: Recreational pursuits not involving a significant risk of water ingestion, including fishing, commercial and recreational boating, and limited body contact incidental to shoreline activity. Compare contact recreation.

  • Non-point source: Source of pollution in which wastes are not released at one specific, identifiable point but from a number of points that are spread out and difficult to identify and control. Compare point source.

  • Nonporous: Something which does not allow water to pass through it. Compare porous.

  • Non-potable: Not suitable for drinking. Compare potable.

  • Non-renewable resources: Natural resources that can be used up completely or else used up to such a degree that it is economically impractical to obtain any more of them; e.g., coal, crude oil, and metal ores.

  • Nonthreshold pollutant: Substance or condition harmful to a particular organism at any level or concentration.

  • Non-Transient Non-Community water system: A public water system that is not a community water system and that regularly serves at least 25 of the same persons over a 6 month period.

  • NPDES permit: Permit issued under the National Pollutant Discharge Elimination System for companies discharging pollutants directly into the waters of the United States.

  • NTU: Nephlometric turbidity units.

  • Nucleus: The center of an atom, that contains protons and neutrons and carries a positive charge.

  • Nuisance Contaminant: Constituents in water, which are not normally harmful to health but may cause offensive taste, odor, color, corrosion, foaming, or staining.

  • Nutrient: As a pollutant, any element or compound, such as phosphorus or nitrogen, that fuels abnormally high organic growth in aquatic ecosystems (e.g., eutrophication of a lake).

  • Nutrient Pollution: Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.

Water glossary