Water Quality Standards


Water quality standards refer to mandated conditions that drinking and recreational water must achieve to be judged acceptable for use.


In the United States, the legislative process is used to establish standards for stream water quality by taking into account the use and value of a stream for public water supplies, propagation of fish and wildlife, recreational purposes, as well as agricultural, industrial, and other legitimate uses. The goals of water quality standards are to protect public health and the environment and to maintain a standard of water quality consistent with its designated uses.


To establish water quality standards for a water body, officials (a) determine the designated beneficial water use; (b) adopt suitable water quality criteria to protect and maintain that use; and (c) develop a plan for implementing and enforcing the water quality criteria.

Water quality is evaluated based on how well the designated uses are supported. In the United States, the Federal Water Act of 1972 and following amendments, together known as the Clean Water Act, require that, whenever possible, water quality standards should ensure the protection and propagation of fish, shellfish, and wildlife and should provide for recreation. States have primary responsibility for designating stream segment uses, so stream uses may vary from state to state. However, stream use as designated by one state must not result in the violation of another state's use of the same stream.

The 1987 amendments to the Clean Water Act required states to identify water not meeting its standards due to nonpoint source pollution (i.e., addition of pollutants from a wider geographical area, such as runoff from a field), identify general and specific nonpoint sources causing the problems, and develop management plans for the control of the these sources. The Clean Water Act also charged the federal government with the responsibility of setting standards for water quality and enforcing those standards. Until the implementation of the act, this responsibility rested with the individual states, which were free to enacted different standards.

Before the passage of the Clean Water Act, water pollution control efforts were considered successful if they achieved water quality standards. Water quality standards were retained as part of the overall strategy to control water pollution. However, rather than using water quality standards as the highest goal for determining water quality, state and federal authorities now consider water quality control standards to be the lowest acceptable level of water quality. In addition, point sources of pollution (i.e., addition of a contaminant at a single site, such as a pipeline) may be subject to more stringent requirements.

A type of unwanted microparticle or organism. In water, a contaminant may reduce clarity, quality, or be a health hazard.
Protozoa organisms—
Single-celled organisms that have animal-like behavior. Certain protozoa are harmful to humans and are found in water, making it important that water is treated and filtered before drinking.
A tiny particle that can cause infections by duplicating itself inside a cell using the cell's own software. Antibiotics are ineffective against viruses, though antiviral drugs exist for some viruses.

The development of water quality standards was first mandated in the United States by the Water Quality Act of 1965. Under this legislation, states had to develop water quality standards and water quality goals. By the early 1970s, these standards and goals had been adopted by all U.S. states. With the advancement of technology and scientific information, states have updated their standards over time. Legally enforceable legislation was also expanded by requirements in the Federal Water Pollution Control Act of 1972, with amendments in 1977 and 1987 (collectively referred to as the Clean Water Act).



The focus on protecting and improving water quality has made drastic changes to water quality around the world. In the United States, the Environmental Protect Agency (EPA) requires that 99.9% of viruses and protozoan organisms are removed before the water can be considered safe for human consumption. Water used for recreation must also pass strict standards. The EPA also requires that water to be consumed by humans be monitored for over 90 contaminants. This is much stricter than in Canada, which recommends checking for fewer than 70 contaminants, or the European Union, which requires that water be checked for 48 contaminants. Although these regulations and guidelines vary by country, all work to keep citizens healthy through protecting and improving both recreational and drinking water.

See also Clean Water Act (1972, 1977, 1987) ; Federal Water Act ; Viruses ; Water pollution ; Water quality .



American Water Works Association and James Edzwald. Water Quality & Treatment: A Handbook on Drinking Water (Water Resources and Environmental Engineering Series). New York: McGraw-Hill, 2011.

Chapra, Steven C. Surface Water-Quality Modeling. Long Grove, IL: Waveland Press, 2008.

Craig, Robin Kundis. The Clean Water Act and the Constitution. Washington, DC: Environmental Law Institute, 2009.

Virgil, Kenneth M. Clean Water: An Introduction to Water Quality and Pollution Control. Corvallis: Oregon State University Press, 2003.


United Nations Department of Economic and Social Affairs. “Water Quality.” http://www.un.org/waterforlifedecade/quality.shtml (accessed October 18, 2012).

United Nations Environment Programmes. “Clearing the Waters: A Focus on Water Quality Solutions.” http://www.unep.org/PDF/Clearing_the_Waters.pdf (accessed October 18, 2012).

United States Environmental Protection Agency. “Water Quality Criteria.” http://water.epa.gov/scitech/swguidance/standards/criteria/index.cfm (accessed October 18, 2012).

United States Environmental Protection Agency. “Water Quality Standards History.” http://water.epa.gov/scitech/swguidance/standards/history.cfm (accessed October 18, 2012).

United States Environmental Protection Agency. “What Are Water Quality Standards?” http://water.epa.gov/scitech/swguidance/standards/about_index.cfm (accessed October 18, 2012).


Centers for Disease Control and Prevention (CDC), 1600 Clifton Rd., Atlanta, GA, 30333, (404) 639-3534, (800) CDC-INFO (800-232-4636); TTY: (888) 232-6348, inquiry@cdc.gov, http://www.cdc.gov .

Environmental Protection Agency, 1200 Pennsylvania Ave., NW, Washington, DC, 20460, (202) 272-0167; (202) 272-0165, http://water.epa.gov .

National Institute of Environmental Health Science, PO Box 12233, MD K3-16, Research Triangle Park, NC, 27709, (919) 541-1919, Fax: (919) 541-4395, http://www.niehs.nih.gov .

Water Quality Association, 4151 Naperville Rd., Lisle, IL, 60532, (630) 505-0160, Fax: (630) 505-9637, http://www.wqa.org .

Judith L. Sims
Revised by Tish Davidson, AM

  This information is not a tool for self-diagnosis or a substitute for professional care.