My watch list  

Water quality

v  d  e
Air pollution
Acid rain • Air Quality Index • Atmospheric dispersion modelingChlorofluorocarbon • Global dimming • Global warming • Haze • Indoor air quality • Ozone depletion • Particulate • Smog
Water pollution
EutrophicationHypoxiaMarine pollutionOcean acidification • Oil spill • Ship pollution • Surface runoff • Thermal pollution • Wastewater • Waterborne diseases • Water qualityWater stagnation
Soil contamination
BioremediationHerbicidePesticideSoil Guideline Values (SGVs)
Radioactive contamination
Actinides in the environment • Environmental radioactivityFission productNuclear falloutPlutonium in the environmentRadiation poisoning • Radium in the environment • Uranium in the environment
Other types of pollution
Invasive species • Light pollution • Noise pollution • Radio spectrum pollution • Visual pollution
Inter-government treaties
Montreal Protocol • Nitrogen Oxide Protocol • Kyoto Protocol • CLRTAP
Major organizations
DEFRA • EPA • Global Atmosphere Watch • Greenpeace • National Ambient Air Quality Standards
Related topics
Environmental Science • Natural environment

Water quality is the physical, chemical and biological characteristics of water in relationship to a set of standards. Water quality standards are created for different types of water bodies and water body locations per desired uses. The primary uses considered for such characterization are parameters which relate to drinking water, safety of human contact, and for health of ecosystems. The methods of hydrometry are used to quantify water characteristics.

In the setting of standards, political decisions are made about how the water will be used and in the case of natural water bodies, some reasonable estimate of pristine conditions. Different uses have different concerns and therefore different standards. Natural water bodies will vary in response to environmental conditions. Environmental scientists are working to understand the functioning of these systems, which determines sources and fates of contaminants. Environmental lawyers and policy makers are working to define water laws that designate the fore mentioned uses and natural conditions.

The vast majority of surface water on the planet is neither potable nor toxic. This remains true even if sea water in the oceans (which is too salty to drink) isn't counted. Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a very complex subject, in part because water is a complex medium intrinsically tied to the ecology of the Earth. Industrial pollution is a major cause of water pollution, as well as runoff from agricultural areas, urban stormwater runoff and discharge of untreated sewage (especially in developing countries).



The parameters for water quality are determined by the intended use. Work in the area of water quality tends to be focused on water that is treated for human consumption or in the environment.

Human Consumption

Contaminants that may be in untreated water include microorganisms such as viruses and bacteria; inorganic contaminants such as salts and metals; pesticides and herbicides; organic chemical contaminants from industrial processes and petroleum use; and radioactive contaminants. Water quality depends on the local geology and ecosystem, as well as human uses such as sewage dispersion, industrial pollution, use of water bodies as a heat sink, and overuse (which may lower the level of the water).

In the United States, the U.S. Environmental Protection Agency prescribes regulations that limit the amount of certain contaminants in the water provided by public water systems for tap water. The U.S. Food and Drug Administration (FDA) regulations establish limits for contaminants in bottled water that must provide the same protection for public health. Drinking water, including bottled water, may reasonably be expected to contain at least small amounts of some contaminants. The presence of these contaminants does not necessarily indicate that the water poses a health risk.

Some people use water purification technology to remove contaminants from the municipal water supply they get in their homes, or from local pumps or bodies of water. For people who get water from a local stream, lake, or aquifer, their drinking water is not filtered by the local government.

Environmental Water Quality

Environment Portal

Environmental water quality includes water bodies such as lakes, rivers, and oceans. In the case of environmental water quality, the standards vary significantly due to different environmental conditions, ecosystems, and intended human uses. Toxic substances and high populations of certain microorganisms can present a health hazard for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also impact wildlife which use the water for drinking or as a habitat. Modern water quality laws general specify protection of fishable/swimmable use and antidegredation of current conditions.

There is some desire to return water bodies to pristine, or pre-industrial conditions. Current environmental laws focus of the designation of uses and therefore allow for some water contamination as long as the particular type of contamination is not harmful to the designated uses. Given the landscape changes in the watersheds of many freshwater bodies, returning to pristine conditions would be a significant challenge. In these cases, environmental scientists focus on achieving goals for maintaining populations of endangered species and protecting human health.


The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. Some of the simple measurements listed below can be made on-site (temperature, pH, dissolved oxygen, conductivity), in direct contact with the water source in question. More complex measurements that must be made in a lab setting require a water sample to be collected, preserved, and analyzed at another location. Making these complex measurements can be expensive. Because direct measurements of water quality can be expensive, ongoing monitoring programs are typical conducted by government agencies. However, there are local volunteer programs and resources available for some general assesment. Tools available to the general public are on-site test kits commonly used for home fish tanks and biological assessments.

The following is a list of indicators often measured by situational category:

Drinking Water

  • Alkalinity
  • Color of water
  • pH
  • Taste and odor (geosmin, 2-methylisoborneol (MIB), etc)
  • Dissolved metals and salts (sodium, chloride, potassium, calcium, manganese, magnesium)
  • Microorganisms such as fecal coliform bacteria (Escherichia coli), Cryptosporidium, and Giardia lamblia
  • Dissolved metals and metalloids (lead, Mercury (element),arsenic, etc.)
  • Dissolved organics: Colored Dissolved Organic Matter (CDOM), Dissolved Organic Carbon (DOC)
  • Radon
  • Heavy Metals
  • Pharmaceuticals
  • Hormone analogs


Chemical Assessment

  • pH
  • Conductivity (also see salinity)
  • Dissolved Oxygen(DO)
  • nitrate-N
  • orthophosphates
  • Chemical oxygen demand (COD)
  • Biochemical oxygen demand (BOD)
  • Pesticides

Physical Assessment

  • Temperature
  • Total suspended solids (TSS)
  • Turbidity

Biological Assessment

Biological monitoring metrics have been developed in many places, and one widely used measure is the presence and abundance of members of the insect orders Ephemeroptera, Plecoptera and Trichoptera (EPT). EPT indexes will naturally vary from region to region, but generally, within a region, the greater the number of taxa from these orders, the better the water quality. A number of websites originating in the United States offer guidance on developing a monitoring program and identifying members of these and other aquatic insect orders.

Individuals interested in monitoring water quality who cannot afford or manage lab scale analysis can also use biological indicators to get a general reading of water quality. One example is the IOWATER volunteer water monitoring program, which includes a benthic macroinvertebrate indicator key.[1]

Standards & Reports

United States

In the United States each governing jurisdiction (states, territories, and covered tribal entities) is required to submit a set of biennial reports on the quality of water in their area. These reports submitted to, and approved by, the Environmental Protection Agency are known as the 303(d), 305(b) and 314 reports[2]. In coming years it is expected that the governing jurisdictions will submit all three reports as a single document, called the Integrated Report. The 305(b) report is a general report on water quality throughout the state, providing overall information about the number of miles of streams and rivers and their agreegate condition. The 314 report provides similar information for lakes. Under the Clean Water Act, states are required to adopt water quality standards for each of the possible designated uses that they assign to their waters. Should evidence exist to suggest or document that a stream, river or lake has failed to meet the water quality criteria for one or more of its designated uses, it is placed on the 303(d) list, or the list of impaired waters. Once on the 303(d) list states are required to develop management plans establishing Total Maximum Daily Loads for the pollutant impairing the use of the water. These TMDLs establish what reductions in pollutants are needed to allow the water to regain its status as fully supporting the designated uses assigned to it. These reports are completed by the governing jurisdiction, typically a Department of Environmental Quality or similar state agency, and are available on the web.

Individuals interested in more information about water quality in areas of the United States may find information at the EPA's "Surf Your Watershed" website.

United Kingdom

In England and Wales acceptable levels are listed in the Water Supply (Water Quality) Regulations 1989.

See also


  1. ^
  2. ^ U.S. Clean Water Act
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Water_quality". A list of authors is available in Wikipedia.
Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE