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Criteria Development Guidance for Lakes and Reservoirs Fact Sheet

April 2000

EPA published a technical guidance manual which provides a method for setting nutrient water quality criteria for lakes and reservoirs. This guidance is intended to assist States, Tribes and others in establishing scientifically defensible ecoregional nutrient criteria. EPA will also use this guidance to develop nutrient criteria for lakes and reservoirs for various ecoregions across the country with the aim of reducing and preventing eutrophication on a National scale.

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EPA is publishing technical guidance which presents EPA's method for setting nutrient water quality criteria for lakes and reservoirs. EPA has not previously issued guidance for developing ecoregional nutrient criteria. In addition, current criteria for nutrients do not specifically address the prevention of eutrophication. In 1976, in EPA's publication entitled Quality Criteria for Water (also known as the Red Book), EPA presented ambient water quality criteria for nitrates, nitrites and phosphorus. The criterion for nitrate nitrogen was 10 mg/L for the protection of domestic water supplies. The phosphorus criterion was 0.10 ug/L elemental phosphorus for the protection of marine and estuarine waters. This criterion was based on a conservative estimate to protect against the toxic effects of the bioconcentration of elemental phosphorus to estuarine and marine organisms, and not on the potential to cause eutrophication. While this guidance does not present nutrient criteria for a specific lake or reservoir, it constitutes EPA's scientific recommendations regarding defensible approaches for developing regional nutrient criteria. EPA will use this guidance to develop default Section 304(a) (of the Clean Water Act) nutrient criteria for various ecoregions across the country. These criteria may then form the basis for States and Tribes to set enforceable water quality standards for lakes and reservoirs.

Why is EPA publishing a Nutrient Criteria Technical Guidance Manual for Lakes and Reservoirs?

On March 24, 1998, the President's Clean Water Action Plan was presented in the Federal Register. The Clean Water Action Plan specifically states that EPA will establish nutrient criteria that reflect the different types of water bodies and different ecoregions of the country and will assist States and Tribes in adopting numeric water quality standards based on these criteria.

Overview of the Problem

Cultural eutrophication (i.e., that associated with humans) of United States surface waters is a long standing problem; approximately half of the National waters reported as impaired are attributable to excess nutrients. Nitrogen and phosphorus are the primary cause of eutrophication and algal blooms are often a response to enrichment. Within lakes and reservoirs, chronic symptoms of overenrichment include low dissolved oxygen, fish kills, increased sediment accumulation, and species and abundance shifts of flora and fauna. The problem is National in scope, but varies in nature from one region of the country to another due to geographical variations in parent geology and soil types. Any criteria developed for management decision making must, therefore, be done on a ecoregional basis.

What are nutrient criteria and how will they be developed?

Nutrient criteria are numerical values for both causative (phosphorus and nitrogen) and response (chlorophyll and turbidity) variables associated with the prevention and assessment of eutrophic conditions. These criteria are expected to be used to help identify problem areas, serve as the basis of State and Tribal water quality standards for nutrients, and evaluate relative success in reducing cultural eutrophication.

The guidance manual describes the elements of a nutrient criterion development:
  • classification of the lakes and reservoirs by physical characteristics;
  • historical data and other information to establish perspective;
  • current reference site information;
  • models used to project existing information, when data are scarce;
  • evaluation of downstream consequences before finalizing criteria values; and
  • a panel of Regional, Federal, State and Tribal specialists to examine the information and establish criteria.

What are the activities related to this guidance document?

A Notice of Availability in the Federal Register was published to provide the public with the opportunity to provide scientific views on the guidance document. Therefore, EPA will review and consider information submitted by the public on significant scientific issues that have not otherwise been identified by the Agency during the development of this guidance. This guidance has been through external peer review, and a summary of these comments and other comments made on earlier drafts are available on the Nutrient website.

Guidance documents for rivers and streams, estuarine and coastal waters, and wetlands also are being developed by EPA.

Will this document be revised in the future?

After review of the submitted significant scientific information, EPA will publish a revised document, or publish a notice indicating its decision not to revise the document. EPA is also committed to updating the document in the future as new scientific information becomes available.

Additional Information

Nutrient Criteria Technical Guidance Manual: Lakes and Reservoirs

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