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Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.


1120 SW Fifth Ave, Suite 600, Portland, OR 97204

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Glossary of Water Terms

  • alkalinity The capacity of water to neutralize acids, expressed in milligrams per liter of equivalent calcium carbonate.
  • aquifer An underground geologic formation capable of storing water.
  • ammonia A chemical used with chlorine to disinfect water.
  • Aquifer Storage and Recovery(ASR) A water supply management strategy that uses wells to recharge treated surface water into an aquifer (groundwater) system for withdrawal later when needed. The aquifer becomes a storage facility for treated drinking water.
  • chloramination Treating drinking water by applying chlorine before or after ammonia. This creates a persistent disinfectant residual.
  • chlorine A chemical which destroys small organisms in water.
  • chlorine residual The concentration of chlorine remaining in water after disinfection
  • coliform A group of bacteria commonly found in the environment. They are an indicator of potential contamination of water. Adequate and appropriate disinfection effectively destroys coliform bacteria.
  • conduits Large pipes like those which carry water from the Bull Run Watershed to Portland
  • contaminant Any natural or man-made physical, chemical, biological, or radiological substance or matter in water, which is at a level that may have an adverse effect on public health, and which is known or anticipated to occur in public water systems.
  • Cryptosporidium A disease-causing parasite, resistant to chlorine disinfection. It may be found in fecal matter or contaminated drinking water.
  • curtailment pricing Pricing water at a rate to reduce consumption.
  • Disinfection by-product A chemical by-proudct of the disinfection process
  • E. coliEscherichia coli is a bacterium commonly found in the human intestine. For water quality analyses purposes, it is considered an indicator organism. These are considered evidence of water contamination. Indicator organisms may be accompanied by pathogens, but do not necessarily cause disease themselves.
  • enterovirus A virus whose presence may indicate contaminanted water; a virus which may infect the gastrointestinal tract of humans.
  • fecal coliform A group of bacteria that may indicate the presence of human or animal fecal matter in water.
  • filtration A series of processes that physically removes particles from water.
  • finished water Treated drinking water that meets state and federal drinking water regulations.
  • Giardia lamblia A pathogenic parasite which may be found in contaminated water.
  • Haloacetic Acids (HAA5): The sum of the concentrations of dichloroacetic acid, trichloroacetic acid, monochloroacetic acid, monobromoacetic acid and dibromoacetic acid.
  • headworks The facility at the "head" of the water source where water is first treated and routed into the distribution system.
  • heterotrophic plate count bacteria A broad group of bacteria including nonpathogens, pathogens, and opportunistic pathogens; they may be an indicator of poor general biological quality of drinking water.
  • HydroPark A shared city resource – a property that serves both Portland ’s drinking water system and provides neighbors access to greenspace at a Portland Water Bureau property.
  • impervious Not allowing, or allowing only with great difficulty, the movement of water.
  • leaching A chemical reaction between water and metals (or other solids) that allows for removal of soluble materials.
  • Legionella A genus of bacteria, some specieis of which have caused a type of pneumonia called Legionnaire's Disease.
  • Maximum Contaminant Levels (MCLs) The maximum allowable level of a contaminant that federal or state regulations allow in a public water system. If the MCL is exceeded, the water system must treat the water so that it meets the MCL.
  • Maximum Contaminant Level Goal or MCLG
    The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.
  • microbe, microbial Any minute, simple, single-celled form of life, especially one that causes disease.
  • mg/L milligrams per liter
  • mL milliliter
  • naturally occurring conservation Conservation that results from plumbing code changes requiring the use of water-efficient plumbing fixtures, such as toilets.
  • nitrates A dissolved form of nitrogen found in fertilizers and sewage by-products which may leach into groundwater and other water sources. Nitrates may also occur naturally in some waters. Over time, nitrates can accumulate in aquifers and contaminate groundwater.
  • NTU (nephelometric turbidity unit) A measure of the clarity of water.
  • pathogens; disease-causing pathogens; waterborne pathogens A pathogen is a bacterium, virus or parasite that causes or is capable of causing disease. Pathogens may contaminate water and cause waterborne disease.
  • pCi/L, picocuries per liter A curie is the amount of radiation released by a set amount of a certain compound. A picocurie is one trillionth of a curie.
  • pH A measure of the acidity or alkalinity of water.
  • pipeline appurtenance Pressure reducers, bends, valves, regulators (which are a type of valve), etc.
  • potable water Water that is safe to drink.
  • primacy agency The agency authorized by law to enforce drinking water regulations. In Oregon, the U.S. Environmental Protection Agency has delegated enforcement authority to the Oregon Department of Human Services, Drinking Water Program.
  • programmatic conservation Conservation that results from public education efforts that influence consumer behavior. Examples include turning off the water when brushing your teeth, washing only full loads of laundry, fixing leaks, etc.
  • radionuclides Radioactive contaminants (non radon). Includes combined radium -226/-228, (adjusted) gross alpha, beta particle and photon radioactivity, and uranium. Radon is radioactive but is not currently regulated. 
  • raw water Water that has not been treated in any way; it is generally considered to be unsafe to drink.
  • reservoir An impoundment used to store water.
  • solder A fusible alloy used to join metallic parts.
  • standpipe A water tank that is taller than it is wide.
  • surface water Water which is open to the atmosphere and subject to surface runoff; generally, lakes, streams, rivers.
  • TCE, trichloroethylene A solvent and degreaser used for many purposes; it is a common groundwater contaminant.
  • treated water Disinfected and/or filtered water served to water system customers. It must meet or surpass all drinking water standards to be considered safe to drink.
  • Treatment Technique: A required process intended to reduce the level of a contaminant in drinking water.
  • Total Trihalomethanes (TTHM): four disinfection by-products: chloroform, bromodichloromethane, dibromochloromethane, and bromoform.
  • trihalomethanes (THM) Four separate compounds including chloroform, dichlorobromomethane, dibromochloromethane, and bromoform.
  • turbidity A measure of the cloudiness of water caused by suspended particles.
  • valve A device that opens and closes to regulate the flow of liquids. Faucets include valves.
  • watershed An area which drains all of its water to a particular water course or body of water.
  • water works All of the pipes, pumps, reservoirs, dams and buildings that make up a water system.

USGS Water Science Glossary of Terms