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Biological Condition Gradient - large image
This material was adapted from Use of Biological Information to Better Define Designated Aquatic Life Uses in State and Tribal WQS: Tiered Aquatic Life Uses (EPA-822-R-05-001). The document provides information that will help States and Tribes assess and communicate current biological conditions and progress towards meeting aquatic life protection goals. The document describes how to define aquatic life uses as tiers of biological condition, from natural to severely-altered. A waterbody's highest attainable use (tier) with its expected biological attributes and appropriate water quality criteria are determined by the waterbody's environmental setting. This tiered approach can help protect high-quality waters, while developing scientifically-sound expectations for restoration of damaged or impaired waters. The document is a result of several years of effort by a workgroup largely comprised of State and Tribal members, and draws from State programs that currently use a tiered approach to their aquatic life use designations.
With release of the document, EPA's Office of Science and Technology has requested the Regions share the document with their States and Tribes and initiate pilot demonstrations. During this pilot phase, State and Tribal feedback will be gathered and evaluated to ensure the tiered aquatic life uses approach works well. If necessary, the document will be revised accordingly and a second edition issued. For more information on the Biological Condition Gradient, please contact Susan Jackson in EPA's Office of Water.