Exploring Tiered Aquatic Life Use in Southern California

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Aquatic life are a powerful alternative to chemistry for evaluating the health of waterbodies. Aquatic life integrates all stressors including flow, physical habitat, and measured, as well, as unmeasured chemical contaminants. Ultimately, aquatic life are the beneficial use to be protected and are consistent with the Clean Water Act goal of “fishable”. However, many states and the US EPA have a very broad definition of aquatic life beneficial uses. Definitions such as “warmwater” or “coldwater” habitat provide insufficient detail to properly set the biological expectations for various habitats. For example, biological expectations are likely different for two streams with varying hydrologic, channel modification, and physical habitat condition.

To adapt to the changing expectations of biological condition, the US EPA has provided states the option of using tiered aquatic life uses (TALU) to refine biological expectations for differences in habitat types. TALU is a management tool that more precisely defines the biological expectations for various habitat conditions without having to conduct use attainability analysis or remove a beneficial use designation. The tiering of aquatic life use provides a more detailed management endpoint enabling managers to better assess, maintain, and restore the highest attainable aquatic life goals for individual stream conditions.

Despite the utility of TALU, there are very few examples of its application around the country. The goal of this study was to identify the feasibility of TALU in southern California. Southern California was a perfect place to test this management tool because it has a diversity of habitat types and a large range of habitat modifications due to urban influences. The project began with a pilot study attempting to establish tiers based on biological condition (the biological condition gradient or BCG) and in stressor condition (generalized stressor gradient or GSG). Both a BCG and GSG were developed and preliminary tiers were constructed for perennial streams based on benthic macroinvertebrates. Modifications to the BCG were attempted for algae, fish, and amphibians. At least two different habitats were identified for TALU in southern California including high and low gradient streams. The lessons learned from the pilot study were then used to evaluate both the technical and political hurdles necessary to implement TALU on a regional basis. Fourteen hurdles in all were delineated, but the hurdles were not so onerous that projects could not be designed to overcome them. TALU development is now under consideration at the state regulatory agencies and could pave the way for changes in listing/delisting policies, TMDL targets, biocriteria, and improved water quality management.

Keywords: TALU; Tiered aquatic life use; beneficial use

Document Type: Research Article

DOI: http://dx.doi.org/10.2175/193864709793958183

Publication date: January 1, 2009

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