Basic Course: Supplemental Topics (g)

Each State/Tribe should have a methodology for assessing attainment of water quality standards based on analysis of various types of data (chemical, physical, biological, land use) from various sources for all waterbody types and all State/Tribal waters.

The methodology should describe how existing and available data and information, relevant to applicable water quality standards and core and supplemental indicators, will be compiled and analyzed to make attainment decisions. The methodology should also describe how the State/Tribe will integrate its primary data—collected specifically for making attainment decisions according to a QAPP—with data from secondary sources, which are collected for a variety of purposes under a variety of quality control practices. (Secondary data could include, for example, volunteer monitoring data or discharge monitoring reports.) The methodology also should:

• Identify the required or likely sources of existing and available data and information and procedures for collecting or assembling it.
• Describe or reference requirements relating to data quality and representativeness, such as analytical precision, temporal and geographical representation, and metadata documentation needs.
• Include or reference procedures for evaluating the quality of datasets.
• Explain data reduction procedures (e.g., statistical analyses) appropriate for comparing data to applicable water quality standards.

Key Point. The assessment methodology is critical for documenting the hierarchy of indicators, methods, and tools used to assess water quality. It establishes a record and provides for consistency from one reporting period to the next.

Resource. For more information on collecting and using water quality data and developing assessment methodologies, visit EPA’s web page on the Consolidated Assessment and Listing Methodology (CALM).

Resource. See EPA’s website on Aquatic Resource Monitoring.