Progress towards Adopting Total Nitrogen and Total Phosphorus Numeric Water Quality Standards
About this indicator
This indicator provides information about states’ progress towards developing and adopting state-wide numeric water quality criteria for total nitrogen and total phosphorus for the three main waterbody types (river/streams, lakes/reservoirs, and estuaries). To protect waters from impairment, states develop, propose, and adopt water quality standards, or pollutant limits. EPA considers state adoption of numeric water quality criteria for nitrogen and phosphorus, the causal parameters directly responsible for eutrophication in immediate and/or downstream waters, a priority for water quality protection. Adoption of numeric criteria for nitrogen and phosphorus will facilitate and expedite the protection of waters by assisting states in identifying and listing impaired waters, developing total maximum daily loads (TMDLs), and writing National Pollutant Discharge Elimination System (NPDES) permits for facilities discharging nitrogen and phosphorus. Numeric criteria for nitrogen and phosphorus can also further improve water quality by assisting in best management practice implementation for non-point sources to limit nitrogen and phosphorus runoff and infiltration.
The information provided in this indicator shows whether or not each state has completed or provided dates for completing the following five milestones towards adoption of state-wide numeric total nitrogen and/or total phosphorus criteria for each of the three main waterbody types (river/streams; lakes/reservoirs, excluding the Great Lakes; and estuaries, where applicable): Planning for Criteria Development, Collection of Information and Data, Analysis of Information and Data, Proposal of Criteria, and Adoption of Criteria (EPA-approved). For more information on states’ progress towards adopting numeric nutrient criteria, refer to EPA’s website on State Development of Numeric Criteria for Nitrogen and Phosphorus Pollution. Additionally, visit states’ websites to learn more about their progress towards developing and adopting numeric total nitrogen and total phosphorus criteria.
What to consider when using these data
Some states may have numeric criteria for specific nutrient-related response parameters such as chlorophyll a (algae), and some states have site-specific total phosphorus and total nitrogen criteria. However, neither would be reflected in this indicator, which reports progress on adoption of total nitrogen and total phosphorus criteria for all waters within the state. For more information on states’ progress towards adopting numeric nutrient criteria, refer to EPA’s website on State Development of Numeric Criteria for Nitrogen and Phosphorus Pollution. Additionally, visit states’ websites to learn more about their progress towards developing and adopting numeric total nitrogen and total phosphorus criteria.
Source of data
This information is submitted by states in support of the National Water Program, and maintained by EPA internally. For more information on EPA’s performance measures, refer to the EPA Office of Water’s National Water Program Guidance.
Data source information
Development of statewide criteria for total numeric nitrogen and phosphorus has been included as part of EPA's National Water Program Guidance. The information presented in this indicator is part of what states submit to EPA every year in support of the National Water Program. To help EPA track state progress on the steps taken towards adopting—on a statewide basis—numeric total nitrogen and total phosphorus water quality standards for the three main waterbody types, states provide EPA with information concerning total nitrogen and total phosphorus numeric criteria development, proposal, and adoption through the following performance measures:
- WQ-1a - Number of numeric water quality standards for total nitrogen and for total phosphorus adopted by States and Territories and approved by EPA, or promulgated by EPA, for all waters within the State or Territory for each of the following waterbody types: lakes/reservoirs, rivers/streams, and estuaries.
- WQ-1d - Number of numeric water quality standards planned to be adopted within 3 years for total nitrogen and total phosphorus for all waters within the state or territory for each of the following waterbody types: lakes/reservoirs, rivers/streams, and estuaries, based on a full set of performance milestone information supplied annually by states and territories.
References and links to other data sources
1. U.S. EPA. Nutrient Pollution Policy and Data website.
2. U.S. EPA. State Development of Numeric Criteria for Nitrogen and Phosphorus Pollution.
3. U.S. Geological Survey. National Water Quality Assessment Program (NAWQA): Nutrient enrichment and criteria.