However, implementing biological criteria in water quality standards provides a systematic, structured, and objective process for making decisions about compliance with water quality standards. This distinguishes biological criteria from earlier use of biological information and increases the value of biological data in regulatory programs. Value of Biological Criteria Biological criteria provide an effective tool for addressing remaining water quality problems by directing regulatory efforts toward assessing the biological resources at risk from chemical, physical or biological impacts. A primary strength of biological criteria is the detection of water quality problems that other methods may miss or underestimate. Biological criteria can be used to determine to what extent current regulations are protecting the use.
Biological assessments provide integrated evaluations of water quality.
They can identify impairments from contamination of the water column and sediments from unknown or unregulated chemicals, non-chemical impacts, and altered physical habitat. Biological criteria require the direct measure of resident aquatic community structure and function to determine biological integrity and ecological function. Biological assessments and criteria have been useful for regulatory, resource protection, and monitoring and reporting programs. By incorporating biological criteria in programs, States can improve standards setting and enforcement, measure impairments from permit violations, and refine wasteload allocation models. In addition, the location, extent, and type of biological impairments measured in a waterbody provide valuable information needed for identifying the cause of impairment and determining actions required to improve water quality.