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WATERSHED CLASSIFICATION AS A TOOL FOR MONITORING, ASSESSMENT, AND MANAGEMENT
Citation:
Detenbeck, N E. WATERSHED CLASSIFICATION AS A TOOL FOR MONITORING, ASSESSMENT, AND MANAGEMENT. Presented at EPA Regions 8,9, and 10 Teleconference Presentation, EPA, Duluth, MN, February 19, 2003.
Description:
Most sources of stream impairment are related to nonpoint source pollution. To more efficiently deal with TMDL-related issues, an integrated approach to small watershed assessment, diagnosis, and restoration planning is needed that is based on differences in sensitivity and probability of impairment among watershed classes. ORD researchers at the Mid-Continent Ecology Division in Duluth have developed a watershed classification approach based on relationships between watershed characteristics and hydrologic regimes to facilitate this process. To date, the watershed classification approach has been demonstrated in three pilot projects, the first examining tributaries to Lake Superior, and the second and third in conjunction with REMAP projects for Great Lakes coastal wetlands and WV wadeable streams, respectively. A collaborative R-EMAP/RARE project involving WV DNR, WV DEP, US EPA Mid-Continent Ecology Division-Duluth (ORD/NHEERL) and US EPA Ecological Exposure Research Division-Cincinnati (ORD/NERL) was developed to meet multiple needs for the state of West Virginia, including the testing of a watershed-based assessment framework. This work has been extended by an interdivisional ORD workgroup which has been examining coastal classification schemes for Great Lakes and marine coastal watersheds and receiving waters (estuaries, coastal wetlands) of the conterminous US. The initial examples for watershed classification have focused on more humid rather than arid areas of the country, and the paradigm for watershed classification may need to be adjusted for other regions. Modifications to the watershed classification paradigm may be needed for western states, particularly for arid and semi-arid regions. Hydrologic thresholds identified for coastal and Great Lakes states have been related to watershed storage (% lakes and wetlands) and land-cover/land-use variables. In contrast, peak flow classes for many western regions have been related to variations in climate and physiography (e.g., precipitation, 2-year 24-hour events, elevation), with fewer relationships developed for % forest cover or watershed storage. Two additional factors that may need to be considered for application of watershed classification to the western U.S. include regional variations in low flow and seasonality of hydrologic regimes. Nonetheless, classification by hydrologic regime can be expected to aid in partitionning variation in stressor-response relationships for anthropogenic stressors in the west, including stressors related to climate change, grazing/bank destabilization, logging, wastewater inputs, flow regulation or water withdrawals, and urbanization.