The Clean Water Act (303(c)(2)(a)) states "water quality standards shall serve the purposes of the [Act] and consider the use and value for public water supplies, propagation of fish and wildlife, recreational, agricultural, industrial and other purposes, and … navigation". The CWA requires states to develop Water Quality Standards (WQS) for all classified waters. Water quality criteria—narrative and numeric—is developed and assigned to water bodies based on the use assigned at classification.
Initially proposed in September of 2013 and undergoing the public review process, EPA's final updates to the National Water Quality Standards regulation were published in the Federal Register on August 21, 2015. The updated regulation is intended to "provide a better-defined pathway for states and authorized tribes to improve water quality and protect high quality waters". Look at a fact sheet explaining the Final Rule
Under the CWA, water bodies are initially classified by the states and a protection level is determined based on the goal use for the water body— a few examples of goal uses are fishing, swimming, or sourcing drinking water. Next, a water quality assessment of water bodies determines which waters are impaired and sets priorities for improvement. Permit limits for point source dischargers are set through the National Pollutant Discharge Elimination System (NPDES) and are based on the water quality standards. Water quality standards are also used to determine Total Maximum Daily Loads (TMDL) in impaired systems.
Components of Water Quality Standards regulation include requirements for:
- Designated Uses – uses specified in WQS regulation whether or not they are being attained considered to determine the necessary criteria needed to protect the use
- Water Quality Criteria – states adopt numeric and narrative criteria, and chemical-specific criteria to protect designated uses including: biological criteria (a description of the desired aquatic community), nutrient criteria (nutrient limits to protect against over-enrichment and cultural eutrophication), and sediment criteria
- Triennial Review – states must review WQS every three years
- Antidegradation – identified high quality waters require enhanced protection to avoid degrading pristine resources
- WQS Variances – a tool to help states or tribes meet compliance requriements and help ensure progress toward improving water quality is achieved by temporarily relaxing WQS
- Use Attainability Analyses (UAA) – all water uses are assumed to be swimmable/fishable unless documentation through a UAA shows those uses are unattainable
Missouri has not classified all its waters—an inaction that renders our state out of compliance with the federal Clean Water Act of 1972. Currently, designated uses have been assigned to the classified waters visible on a 1:100K map (1 inch on the map: 100,000 inches on the ground). Through its Water Protection Program, the state Department of Natural Resources (DNR) assigns designated uses and associated water quality standards to those classified waters. Criteria are set based on uses. Examples of regulated pollutants include chlorine, chloride, fluoride, nitrate, dissolved oxygen (minimum), oil and grease, and E. coli. See information from MDNR on Missouri's Water Quality Criteria
Unclassified waters are not legally protected from regulated levels of these and other pollutants that ensure a minimum level of water quality is preserved in our waters. MCE participates in stakeholder Water Quality Standards workgroups to advance water protections in the state. Check out our information on Missouri's unprotected waters
Nutrient pollution (primarily nitrogen and phosphorus) is particularly abundant in Missouri rivers, lakes, streams, and wetlands due to industrial discharges, agricultural runoff from fertilizer application, and stormwater runoff from urban areas. Nutrient pollution is a major cause of the Dead Zone in the Gulf of Mexico. Nutrient criteria has not been established for any classification of water bodies in Missouri. In 2011, EPA denied DNR's proposed lake nutrient criteria. DNR workgroups have developed draft criteria several times since EPA's disapproval, but political interests have stopped the process. DNR proposed its latest draft in October 2015. MCE participates in DNR's Nutrient Criteria Technical Subcommittee.