Jump to main content.


Water Quality Standards (WQS)

Whis is a WQS? Why are WQS Important? Reviewing WQS
Indian Tribe Information WQS Regulation History

The Water Quality Standards (WQS) program is one of the cornerstones of the Clean Water Act (CWA). Through this program, the States and Indian Tribes set water quality standards for waters within their jurisdictions. Water quality standards define uses for water bodies and identify specific water quality criteria to achieve those uses. Water quality standards also contain antidegradation policies designed to protect improvements in water quality and existing high quality waters. The Water Quality Standards Program operates under §303 of the Federal Water Pollution Control Act (Clean Water Act), 1972 (33 U.S.C. 1313(c)). The current regulations implementing this section of the CWA were published on November 8, 1983 (48 FR 51400) and are codified at 40 Code of Federal Regulations (CFR) Part 131. Exit EPA Click for Disclaimer On May 30, 2000, the Alaska Rule became effective. This rule states, the water quality standards developed by a state are not effective until they have been approved by EPA. Region 7's purpose is to assist states and tribes in the development of Water Quality Standard's Programs that fulfill the Clean Water Act §101(a)(2) goals of restoring and maintaining the chemical, physical and biological integrity of the nation's waters; and, where attainable, to achieve a level of water quality that provides for the protection and propagation of fish, shellfish and wildlife and recreation in and on the water.

States and Tribes are required by the CWA to adopt criteria for toxic pollutants for which EPA has published CWA §304(a) criteria. Once Water Quality Standards have been adopted by the States and approved by EPA, they are used in determining National Pollutant Discharge Elimination System (NPDES) permit limits, impairment status, and Total Maximum Daily Load (TMDL) endpoints. If a water body is determined to be impaired or not meeting Water Quality Standards, then the water body is listed on the section 303(d) list.

Top of Page

A water quality standard consists of three basic elements:
1. Designated uses that describe the existing and/or potential uses of a waterbody (e.g., recreation, drinking water supply, aquatic life protection),

2. water quality criteria to protect the designated uses (typically expressed in terms of allowable numeric pollutant concentrations or narrative requirements), and

3. an antidegradation policy to maintain and protect existing water quality (i.e., where water quality is better than minimally required by the water quality criteria) and existing uses, whether or not such uses have been designated.

Water quality standards also contain other policies and provisions that explain, for example, how the standards are to be implemented.

Designated Uses: The water quality standards regulation requires that States and approved Indian Tribes specify appropriate water uses to be achieved and protected by taking into consideration the use and value of the water body for public water supply, for propagation of fish, shellfish, and wildlife, and for recreational, agricultural, industrial, and navigational purposes. In designating uses for a water body, States and Tribes examine the suitability of a water body for the uses based on the physical, chemical, and biological characteristics of the water body, its geographical setting and scenic qualities, and the social-economic and cultural characteristics of the surrounding area. Each water body does not necessarily require a unique set of uses. Instead, the characteristics necessary to support a use can be identified so that water bodies having those characteristics might be grouped together as supporting particular uses.

Any water body with standards not consistent with the section 101(a)(2) goals of the Act must be reexamined every three years to determine if new information has become available that would warrant a revision of the standard. In addition, the regulation requires that where existing water quality standards specify designated uses less than those that are being attained, the State or Tribe shall revise its standards to reflect the uses actually being attained.

Water Quality Criteria: States and Tribes adopt water quality criteria with sufficient coverage of parameters and of adequate stringency to protect designated uses. In adopting criteria to protect the designated use, States and Tribes may:

The water quality standards regulation encourages States and Tribes to adopt both numeric and narrative criteria. Numeric criteria are important where the cause of toxicity is known or for protection against pollutants with potential human health impacts or bioaccumulation potential. Narrative toxic criteria can be the basis for limiting toxicity in waste discharges (based on whole-effluent toxicity testing) where a specific pollutant can be identified as causing or contributing to the toxicity but there are no numeric criteria in the standards or where toxicity cannot be traced to a particular pollutant. Whole-effluent toxicity (WET) testing is also appropriate for discharges containing multiple pollutants because WET testing provides a method for evaluating synergistic and antagonistic effects on aquatic life.

The States and Tribes may adopt EPA's criteria, or they may develop site-specific criteria, based on site-specific conditions and sound science. One procedure that may be used to develop site-specific criteria is the Species Recalculation Procedure. This procedure allows the States to add or remove species toxicity data when determining criteria based on water body specific information. The state may also use the Water Effect Ratio procedure which takes into account relevant differences in pollutant toxicity for site water and laboratory water. The third procedure is the Resident Species Procedure, which is a combination of the other two procedures.

Section 303(c)(2)(B) of the Act requires States and approved Tribes to adopt criteria for all section 307(a) priority toxic pollutants for which the Agency has published criteria under section 304(a), if the discharge or presence of the pollutant could reasonably be expected to interfere with the designated uses of the water body. The section 307(a) list contains 65 compounds and families of compounds, which the Agency has interpreted to include 126 priority toxic pollutants for regulatory purposes. If data indicate that it is reasonable to expect that one or more of the section 307(a) toxic pollutants will interfere with the attainment of the designated use, or is actually interfering with the designated use, then the State or Tribe must adopt a numeric criterion for the specific pollutant. Section 303(c)(2)(B) also provides that where EPA-recommended numeric criteria are not available, States and Tribes shall adopt criteria based on biological monitoring or assessment methods.

Antidegradation Policy: Water quality standards include an antidegradation policy and methods through which the State or Tribe implements the antidegradation policy. The water quality standards regulation sets out a three-tiered approach for the protection of water quality.

"Tier 1" of antidegradation maintains and protects existing uses and the water quality necessary to protect these uses (40 CFR 131.12(a)(1)). An existing use can be established by demonstrating that fishing, swimming, or other uses have actually occurred since November 28, 1975, or that the water quality is suitable to allow such uses to occur, whether or not such uses are designated uses for the water body in question.

"Tier 2" protects the water quality in waters whose quality is better than that necessary to protect "fishable/swimmable" uses of the water body (40 CFR 131.12(a)(2)). The water quality standards regulation requires that certain procedures be followed and certain showings be made (an "antidegradation review") before lowering water quality in high quality waters. In no case may water quality on a tier 2 water body be lowered to a level at which existing uses are impaired.

"Tier 3" protects outstanding national resource waters (ONRWs), which are provided the highest level of protection under the antidegradation policy (40 CFR 131.12(a)(3)). ONRWs generally include the highest quality waters of the United States. However, the ONRW antidegradation classification also offers special protection for waters of "exceptional ecological significance," i.e., those water bodies which are important, unique, or sensitive ecologically, but whose water quality, as measured by the traditional parameters such as dissolved oxygen or pH, may not be particularly high. Waters of exceptional ecological significance also include waters whose characteristics cannot adequately be described by traditional parameters (such as wetlands and estuaries).

Antidegradation implementation procedures address how States and Tribe ensure that permits and control programs meet water quality standards and antidegradation requirements.

General Policies: The water quality standards regulation allows States and Tribes to include in their standards policies and provisions regarding water quality standards implementation, such as mixing zones, variances, and low-flow exemptions. Such policies are subject to EPA review and approval. These policies and provisions should be specified in the State or Tribe's water quality standards document. The rationale and supporting documentation should be submitted to EPA for review during the water quality standards review and approval process.

Mixing Zones: States and Tribes may, at their discretion, allow mixing zones for dischargers. The water quality standards should describe the methodology for determining the location, size, shape, outfall design, and in-zone quality of mixing zones. Careful consideration must be given to the appropriateness of a mixing zone where a substance discharged is bioaccumulative, persistent, carcinogenic, mutagenic, or teratogenic

Low-Flow Provisions: State and tribal water quality standards should protect water quality for the designated and existing uses in critical low-flow situations. States and Tribes may, however, designate a critical low-flow below which numerical water quality criteria do not apply. When reviewing standards, States and Tribes should review their low-flow provisions for conformance with EPA guidance.

Water Quality Standards Variances: As an alternative to removing a designated use, a State or Tribe may wish to include a variance as part of a water quality standard, rather than change the standard across the board, because the State or Tribe believes that the standard ultimately can be attained. By maintaining the standard rather than changing it, the State or Tribe will assure that further progress is made in improving water quality and attaining the standard. Variances are temporary, subject to review every 3 years, and may be extended upon expiration. Where a variance specifies an interim criterion applicable for the duration of the variance for a particular pollutant, a long-term underlying goal criterion is also specified that is adequate to protect the designated use. EPA has approved variances in the past and will continue to do so if:


Top of Page

Water quality standards are important because they help to address and solve many types of water quality problems. Standards help to monitor and assess water quality problems stemming from improperly treated wastewater discharges, runoff or discharges from active or abandoned mining sites, sediment, fertilizers, and chemicals from agricultural areas, and erosion of streambanks caused by improper grazing practices. Standards are also a critical aspect of many surface water quality protection efforts, including:
1. Calculating total maximum daily loads (TMDLs), waste load allocations (WLAs) for point sources of pollution, and load allocations (LAs) for nonpoint sources of pollution,
2. Developing water quality management plans which prescribe the regulatory, construction, and management activities necessary to meet the waterbody goals,
3. Calculating NPDES water quality-based effluent limitations for point source discharges,
4. Issuing water quality certifications for activities that may affect water quality and that require a federal license or permit,
5. Preparing various reports and lists (e.g. 303(d) lists or 305(b) reports) that document current water quality conditions, and developing, revising, and implementing an effective CWA § 319 management plan that outlines the States' and Tribes' control strategies for nonpoint sources of pollution.
Top of Page

The Clean Water Act requires States and approved Indian Tribes to hold a public hearing(s) to review their water quality standards at least once every three years, and revise them if appropriate. In preparing proposed revisions to their standards, States and Tribes consider all available information including information in CWA § 305(b) reports and requests from industry, environmental groups, or the public. Such public participation may occur through public meetings, workshops, or by soliciting public review of a preliminary draft set of revisions. Adoption of the needed revisions must be consistent with the public participation requirements found in EPA's water quality standards regulation (see 40 CFR 131.20(b)) and EPA's public participation regulation (40 CFR 25).

Once public participation requirements are met, the water quality standards are certified by the State Attorney General or other appropriate legal authority. This ensures that the water quality standards are dully adopted in accordance with State law.

After water quality standards revisions are officially adopted, a Governor, Tribal Council, or designee submits the standards to the appropriate EPA Regional Administrator for review. EPA reviews the standards to determine whether the analyses performed are adequate. The Agency also evaluates whether the designated uses and criteria are compatible throughout the water body and whether the downstream water quality standards are protected.

After reviewing the standards, EPA makes a determination whether the standards meet the requirements of the law and EPA's water quality standards regulations. If EPA disapproves a standard, the Agency indicates what changes must be made for the standard to be approved. If a State or Tribe fails to make the required changes, EPA promulgates a Federal standard, setting forth a new or revised water quality standard applicable to the State or Indian Reservation. Only existing water quality standards remain in effect. Those standards disapproved by EPA, are not effective until the State modifies them and are approved by EPA, or EPA promulgates a rule that supersedes the disapproved standards.
Top of Page

One major task is for the Tribe to qualify to administer the program. This is accomplished by developing and submitting an application to the U.S. Environmental Protection Agency (EPA) Regional Administrator. EPA then reviews the Tribe's application and decides whether the Tribe meets the applicable requirements. A second major task is the development of water quality standards. The two separate tasks, development of: (1) the application, and (2) the standards, can occur simultaneously. That is, the Tribe can develop a program application and adopt standards and then submit both to EPA for approval. It is recommended that the program application be submitted as soon as draft standards have been completed. This approach hopefully will lead to timely Agency approval of the Tribe's program application before the Tribe adopts final standards. In this way, when the adoption of standards occurs, the standards will be applicable (i.e., legally effective) under the Clean Water Act (CWA).

On December 14, 1994, EPA promulgated a regulation that simplified the process by which Indian Tribes may qualify to be treated in the same manner as States for purposes of various environmental programs under the CWA, Safe Drinking Water Act, and Clean Air Act. One of the amended regulations is the 40 CFR 131 water quality standards regulation, which had been previously amended December 12, 1991, to establish a process by which Tribes could qualify to administer the water quality standards program.

For the water quality standards program, the major modifications to the program approval process are summarized below. This summary is not comprehensive - the full text of the final regulation should be consulted for a complete discussion.

The major changes to the program approval process for water quality standards can be summarized as follows:

  1. The phrase "treatment as a State" was deleted from the regulation. The Agency had previously decided to discontinue use of this phrase to the extent possible, and the December 14, 1994 simplification rule amended the water quality standards regulation to implement that decision. What was formally referred to as the "TAS approval process" will now be referred to, for water quality standards, as the "program approval process."

  2. More flexibility was established with respect to the items to be included in tribal applications. Prior to the December 14, 1994 amendments, there were a number of items that tribal applications were required to include. These items are now only recommended for inclusion. However, the Region continues to have discretion to request additional information that it determines is needed to make a decision. The net effect is that both Tribes and the Region have more flexibility in determining the items and information that should be included in tribal program applications.

  3. EPA no longer is required to evaluate "federal recognition" and "substantial duties and powers" for each program. Under the new simplified approval process, if a tribe has been previously determined by EPA under the Clean Water, Safe Drinking Water, or Clean Air Acts to meet these two criteria for program approval, these issues do not have to be revisited for any subsequent programs.

Tribes need not apply for program approval in advance of submitting water quality standards for approval. The preamble to the December 14, 1994 amendments clarifies that Tribes may optionally wait to submit the program application discussed in 40 CFR 131.8 along with their adopted water quality standards (which also must be submitted to EPA for approval). That is, tribal requests for EPA approval of the program application and the actual water quality standards can be handled in one submission to the Agency. This is merely a clarification of what has always been the case. As noted above, EPA Region 7 recommends, rather than waiting for final tribal adoption of water quality standards, Tribes apply for program approval as soon as a reasonably complete program application is assembled.
Top of Page

In the late 1960s and early 1970s the water quality standards program was initiated and administered based on minimal guidance and federal policies--many of which are still reflected in the water quality standards program today.

The Environmental Protection Agency (EPA) first promulgated a water quality standards regulation in 1975 as part of EPA's water quality management regulations mandated under Section 303(e) of the Clean Water Act (CWA). As discussed earlier, the standards program had a relatively low priority during this time. This was reflected in the minimal requirements of the first Water Quality Standards Regulation. Few requirements on designating water uses and procedures were included. The Regulation merely required "appropriate" water quality criteria necessary to support designated uses. Toxic pollutants or any other specific criteria were not mentioned. The antidegradation policy was incorporated as a regulatory requirement.

State response to the initial regulation was varied and in some cases inadequate. Some States developed detailed water quality standards regulations while others adopted only general provisions which proved to be of limited use in the management of increasingly complex water quality problems. The few water quality criteria that were adopted addressed a limited number of pollutants and primarily described fundamental water quality conditions (e.g., pH, temperature, dissolved oxygen and suspended solids) or dealt with conventional pollutants.

In the late 1970s, a greater appreciation evolved on the need to expand and accelerate the control of pollutants in surface waters using water quality-based controls. It became clear that primary reliance on industry effluent guidelines or effluent standards under Section 307 of the CWA would not comprehensively address pollutants, particularly toxic pollutants, and that existing State water quality standards needed to be better developed. EPA moved to strengthen the water quality program to complement the technology based controls.

To facilitate this effort, EPA decided to amend the Water Quality Standards Regulation to explicitly address toxic criteria requirements in State standards and other legal and programmatic issues. This effort culminated in the promulgation of a revised water quality standards regulation on November 8, 1983, which is still in effect. This regulation is much more comprehensive than its predecessor and it includes many more specific regulatory and procedural requirements. Nonetheless, it is still a succinct and flexible regulation for a program with a scope as broad as the national water quality criteria and standards program.

The regulation specifies the roles of the States, Tribes and EPA and the administrative requirements for States and Tribes in adopting and submitting their standards to EPA for review. It also delineates the EPA requirements for review of State and Tribal standards and promulgation of federal standards.

The regulation provided States and subsequently Tribes with the option of refining their use designation process by allowing them to establish subcategories of uses, such as cold water and warm water aquatic life designations. The regulation expanded and clarified the factors that could be applied by a State in removing a designated use that is not an existing use. The regulation recognized that naturally occurring pollutant concentrations, naturally low or intermittent flow conditions, human caused conditions or sources of pollution that cannot be remedied, hydrologic modifications (such as dams or channelized streams), natural physical conditions, and widespread economic and social impact could be used to demonstrate that attaining a use designation is not feasible (see 40 CFR 131.10(g)). Part 131.10(h) identified circumstances in which States are prohibited from removing designated uses.

Much more specificity was provided in the 1983 regulation regarding the requirements for States on the form of water quality criteria adopted by the States. Under 40 CFR 131.11(b) of the regulation, States and Tribes may use the criteria developed by EPA under Section 304(a) of the Act, 304(a) guidance modified to reflect site-specific conditions, or criteria developed through other scientifically defensible methods. Section 304(a) criteria are the water quality criteria that EPA develops and provides in the form of guidance to States and Tribes pursuant to CWA section 304(a). In practice, States and Tribes have applied all of these provisions in setting water quality standards.

The 1983 regulation also clarified that States and subsequently Tribes may adopt discretionary policies affecting the implementation of standards, such as mixing zones, low flows, and variances. Such policies are subject to EPA review under 303(c). Section 131.11 of the regulation requires States and subsequently Tribes with water quality standards programs to review available information and "...to identify specific water bodies where toxic pollutants may be adversely affecting water quality ...and... adopt criteria for such toxic pollutants applicable to the waterbody sufficient to protect the designated use."

Under the statutory scheme, during the 3-year review period following EPA's 1980 publication of section 304(a) water quality criteria to the protect human health and aquatic life, States were expected to review those criteria and adopt standards for many priority toxic pollutants. A few States adopted large numbers of numeric toxics criteria, primarily for the protection of aquatic life. Other States adopted few or no water quality criteria for priority toxic pollutants. Some relied on a narrative "free from toxicity" criterion, and "action levels" for toxic pollutants or occasionally calculated site-specific criteria. Few States addressed the protection of human health by adopting numeric human health criteria.

In support of the 1983 Regulation, EPA simultaneously issued program guidance entitled "Water Quality Standards Handbook" (December, 1983). The Handbook provided guidance on the interpretation and implementation of the Water Quality Standards Regulation. This document also contained information on scientific and technical analyses that are used in making decisions that would impact water quality standards. EPA also developed the Technical Support Document for Water Quality-Based Toxics Control (TSD) which provided additional guidance for implementing State water quality standards. In 1991, EPA revised and expanded the TSD. In 1994, EPA issued the Water Quality Standards Handbook: Second Edition (August 1994).

To accelerate compliance with CWA section 303(c)(2)(B) (created by the 1987 Water Quality Act), EPA started action in 1990 to promulgate numeric water quality criteria for those States that had not adopted sufficient water quality standards for toxic pollutants. The intent of the rulemaking, known as the National Toxics Rule, was to strengthen State water quality management programs by increasing the level of protection afforded to aquatic life and human health through the adoption of all available criteria for toxic pollutants present or likely to be present in State waters. This action culminated on December 22, 1992, with EPA promulgating Federal water quality criteria for priority toxic pollutants for 14 States and Territories.

Subsequent to the promulgation of criteria under the National Toxics Rule, EPA altered its national policy on the expression of aquatic life criteria for metals. On May 4, 1995, EPA issued a stay of several metals criteria (expressed as total recoverable metal) previously promulgated under the National Toxics Rule for the protection of aquatic life. EPA simultaneously issued an interim final rule that changed these metal criteria promulgated under the National Toxics Rule from the total recoverable form to the dissolved form.

The Water Quality Standards Regulation was amended in 1991 to implement Section 518 of the Act to expand the standards program to include Indian Tribes (December 12, 1991). EPA added 40 CFR 131.7 to describe the requirements of the issue dispute resolution mechanism (to resolve unreasonable consequences that may arise between a Tribe and a State or another Tribe when differing water quality standards have been adopted for a common body of water) and 40 CFR 131.8 to establish the procedures by which a Tribe applies for authorization to assume the responsibilities of the water quality standards and section 401 certification programs.

For more information visit EPA's Water Quality Standards home page, or visit your State's Water Quality Standards website.

Top of Page


Local Navigation


Jump to main content.