Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs
The U.S. Environmental Protection Agency has issued final recommended ambient water quality criteria to address nutrient pollution in lakes and reservoirs. The agency has identified recommended concentrations for Total Nitrogen and Total Phosphorus to protect three designated uses: aquatic life, recreation, and drinking water sources. These recommendations contain criteria development tools based on stressor-response models and can combine state and national data to derive state-specific values that reflect local conditions. The tools provide flexibility for each state to incorporate their own risk management decisions in deriving final criteria. States, territories, and authorized Tribes can consider adopting these recommended criteria into their water quality standards and using them for Clean Water Act purposes. These recommendations replace those published by the EPA in 2000 and 2001 for lakes and reservoirs.
- Federal Register Notice: Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs (August 13, 2021)
- Fact Sheet: Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs (pdf)
- Response to Public Comments (pdf)
- Document: Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs (pdf)
The criteria document describes statistical models that relate nutrient concentrations to endpoints that quantify protection of different designated uses (aquatic life use, drinking water source, and recreation). These statistical models are provided in interactive applications that allow users to specify lake characteristics and risk management decisions to identify numeric criteria to protect each designated use. For waters with multiple use designations, states and authorized Tribes need to use the criteria that protects the most sensitive use.
Links to the interactive models are provided:
Note: Models were updated to include 2017 National Lakes Assessment data (September 8, 2022).
Learn more about these updates:
The EPA hosted a webinar to help members of the public understand the criteria and how they can be used. The webinar provided an overview of the EPA’s nutrient criteria for lakes and reservoirs, discussed how the models are structured, and presented the interactive web applications available to stakeholders to incorporate local lake characteristics and risk management decisions when deriving criteria.
- Webinar Slides: Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs (October 2021)
Frequently Asked Questions: Implementing the 2021 Recommended Clean Water Act Section 304(a) Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs
This final document, in a question-and-answer format, supports implementation of the EPA’s Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs (published in the Federal Register on August 13, 2021). This document provides information on how states and authorized Tribes may use the EPA’s ambient water quality criteria recommendations to address nutrient pollution in lakes and reservoirs to protect aquatic life, recreation, and drinking water sources in permitting, assessment, and watershed protection programs administered by state and Tribal governments.