Alternative Regionalization Scheme for Defining Nutrient Criteria for Rivers and Streams.

摘要

The USEPA has provided its administrative regions flexibility to refine this approach by establishing Regional Technical Assistance Groups (RTAGs), whose roles are to evaluate and possibly refine the boundaries of these relatively homogeneous areas and corresponding nutrient criteria (U.S. Environmental Protection Agency, 2000b). As part of RTAG efforts, the U.S. Geological Survey (USGS), in cooperation with the USEPA, assessed and refined the basic nutrient ecoregion approach for the Upper Midwest area of the United States (fig.2). This report describes the result of this effort and describes an alternative regionalization scheme developed by use of regression-tree analyses and a geographic information system (GIS). Various modifications to the method are also presented that would enable states or USEPA administrative regions to apply the method at different geographic scales and locations.