Impact/Purpose:

Integrated hierarchical classification schemes are being developed at the scale of water bodies, watersheds, and regions to identify systems that are expected to respond similarly to aquatic stressors. Such a classification framework will provide regional, State, and Tribal regulatory authorities a tool to collapse the over 40,000 water bodies requiring TMDLs into a more manageable number of similar units or water body classes. With defined water body classes, a TMDL template for remediating the impairment could be created which could then be applied to all of the water bodies within the class with minor adjustments. This would eliminate the need for 40,000 unique TMDLs.

Classification frameworks will also help to regionalize criteria development or definition of thresholds for impairment. This would improve the applicability of criteria to specific sites or classes of sites and lower the error rate in identifying impaired or threatened aquatic ecosystems.

In particular, a watershed classification scheme within a regional framework will help to integrate and coordinate the 303(d) listing process at the watershed scale.

Description:

The goal of Diagnostics Research is to provide tools to simplify diagnosis of the causes of biological impairment, in support of State and Tribe 303(d) impaired waters lists. The Diagnostics Workgroup has developed conceptual models for four major aquatic stressors that cause impairment: nutrients, suspended and bedded sediments, toxics, and altered habitat. The conceptual models form the basis for classification of aquatic systems according to their sensitivity to these stressors. Classification of coastal systems is intended to provide evidence for causes of impairment at a national scale by grouping systems that have similar physical and hydrological characteristics and similar biological responses to load-based stressors. A classification framework will also simplify the task of applying stressor-response models to complex systems. The most useful classification framework for our purposes would group coastal watersheds that respond similarly to stressor loads. We developed an initial classification framework based on physical, hydrological, and biochemical factors that affect the biological response of coastal systems to stressors. The goal of Diagnostics Research is to provide tools to simplify diagnosis of the causes of biological impairment, in support of State and Tribe 303(d) impaired waters lists. The Diagnostics Workgroup has developed conceptual models for four major aquatic stressors that cause impairment: nutrients, suspended and bedded sediments, toxics, and altered habitat. The conceptual models form the basis for classification of aquatic systems according to their sensitivity to these stressors. Classification of coastal systems is intended to provide evidence for causes of impairment at a national scale by grouping systems that have similar physical and hydrological characteristics and similar biological responses to load-based stressors. A classification framework will also simplify the task of applying stressor-response models to complex systems. The most useful classification framework for our purposes would group coastal watersheds that respond similarly to stressor loads. We developed an initial classification framework based on physical, hydrological, and biochemical factors that affect the biological response of coastal systems to stressors. An extensive review of existing classification schemes was conducted and initial development of a classification framework for coastal watersheds was completed. Physical and hydrological parameters from Environmental Monitoring and Assessment (EMAP) and NOAA's Coastal Assessment and Data Synthesis (CA&DS) data sets were compiled for 203 estuarine drainage areas (EDA) and used to classify estuaries into groups whos members had similar characteristics. Four additional databases were generated for future validation exercises and stressor-response modeling: 1) land cover statistics, 2) stressor loads, 3) in situ stressor concentrations, and 4) modifying factors. A. posteriori classification of 203 EDAs was perfomed on the physical and hydrological parameters and identified eleven clusters or groups of EDA/CDAs. This classification did not group coastal watersheds explicitly by responses to stressor loads but, rather, by the hydrological characteristics thought to influence response to stressors. Watershed classes can be used to refine criteria development for nonpoint-source pollutants, to determine probabilities of impairment and set priorities for future monitoring, and to identify common strategies for TMDL development and watershed restoration. We have developed an approach for watershed classification based on the concept of hydrologic thresholds that, once exceeded, indicate a change in hydrologic regime from stable to flashy systems. Hydrologic thresholds can be linked to either natural or anthropogenic attributes of watershed, primarily land-use or land-cover features such as lake + wetland coverage (watershed storage). An increase in flow responsiveness can be linked to accelerated habitat degradation through bank erosion and scouring, increased delivery of pollutants downstream, and a greater probability of biological impairment. Watershed classification projects have been used to discriminate among watersheds with differing sensitivities to land-use and nonpoint stressors. The conceptual basis for classification has been developed. As part of a coastal classification framework, thresholds have been derived to support watershed classification in Great Lakes and marine coastal states. In conjunction with the R-EMAP program, watershed classification has been successfully tested in case studies within Great Lake states, and evaluation is underway for a comprehensive watershed classification framework for the state of WV. Products in this science area represent the combined efforts of three NHEERL Divisions (Atlantic Ecology Division, Gulf Ecology Division, and Mid-Continent Ecology Division) under the Diagnostics portion of the Aquatic Stressors Research Framework. Testing of the classification framework continues under a separate APM, Diagnostic Tool Development and Application through Regional Case Studies. Efforts are being supplemented by the extramural grants STAR program.

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