Criteria Development Guidance for Wetlands Factsheet

November 2008

EPA has prepared a technical guidance manual to help states and tribes establish water quality criteria and standards for nitrogen and phosphorus in their wetlands. The manual explains how to consider water, vegetation and soil conditions and develop regionally-based numeric nutrient criteria for wetland systems.


Background

In the course of normal activities, people can increase runoff from the land surface and increase the amount of nitrogen and phosphorus (called nutrients) that enter surface waters, including wetlands. Normally, the addition of plant nutrients stimulates the growth of algae and other plants which, in turn, increases the number of fish and other organisms in the food web. But when nutrients accumulate in excessive quantities (called eutrophication), they can harm water quality, the aquatic life that depends on those waters, and human uses of that water. EPA is developing recommended nutrient criteria to help states and authorized tribes address the problem of eutrophication.

In 1998, EPA published a report entitled National Strategy for the Development of Regional Nutrient Criteria. This report outlined a framework for development of waterbody-specific technical guidance that can be used to assess nutrient status and develop region-specific numeric criteria for nitrogen and phosphorus. We have already released the companion Nutrient Criteria Technical Guidance Manuals for Rivers and Streams (2000), Lakes and Reservoirs (2000) and Estuarine and Coastal Marine Waters (2001). The document presented here is the wetland-specific technical guidance for developing numeric nutrient criteria (2008).

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What are Nutrient Criteria and how are they developed?

Nutrient criteria are numerical values used as limits on amounts of both causative (in this case, phosphorus and nitrogen) and response (vegetation changes, chlorophyll, and turbidity) variables associated with eutrophic conditions. We expect that states and tribes will use these criteria to help identify problem areas, serve as the basis of state water quality standards for nutrients, and evaluate success in reducing eutrophication caused by human activities. The guidance manual describes the elements of wetland nutrient criteria development:

  • Classification of Wetlands
    The guidance describes ways to classify wetlands to help develop appropriate nutrient criteria. Classifications include one or more of these characteristics: physiographic region, hydrogeomorphic class, water depth and duration, and/or vegetation type or zone.
  • Sampling Design
    The guidance describes three sampling approaches: stratified random sampling, targeted/tiered approach, and BACI (Before/After, Control/Impact).
  • Criteria Development
    The guidance presents three methods for developing nutrient criteria:
    1. Identifying reference systems for each wetland type and class based on either best professional judgment (BPJ) or percentile selections of data plotted as frequency distributions.
    2. Refining classification systems, using models, and/or examining system biological attributes to assess the relationships among nutrients, vegetation or algae, soil, and other variables.
    3. Using or modifying published nutrient and vegetation, algal, and soil relationships and values as criteria.

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How to Get Additional Information

You can download the complete document Nutrient Criteria Technical Guidance Manual Wetlands (EPA-822-B-08-001) from EPA's National Service Center for Environmental Publications (NSCEP).

EPA's National Management Measures to Protect and Restore Wetlands and Riparian Areas for the Abatement of Nonpoint Source Pollution Guidance provides technical assistance on the best available and economically achievable means to reduce pollution from surface water and groundwater.

EPA prepared several modules to give states and tribes "state-of-the-science" information that will help them develop biological assessment methods to evaluate both the overall ecological condition of wetlands and nutrient enrichment (one of the primary stressors on many wetlands).

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