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Development of Landscape Indicators for Potential Nutrient Impairment of Streams in EPA Region 8

Karl A. Hermann 1, Thomas R. Johnson 1, Sarah A. Spaulding 2, and Anthony R. Selle 1

1 U.S. Environmental Protection Agency, Region 8, Denver, CO
2 U.S. Geological Survey, Biological Resources Division, Denver, CO

Landscape indicators for potential nitrogen and phosphorus impairment of streams were developed for EPA Region 8. The development effort included producing selected landscape metrics for hundreds of catchments related to field monitoring samples of nitrogen and phosphorus from the Environmental Monitoring and Assessment Program (EMAP) Western Study. One of the primary datasets used in creating the landscape metrics was the National Land Cover Dataset (NLCD). Forty different versions of GIS-based catchment delineations were created for each site by clipping the full sample site catchment at different interval distances from the sample site and using different stream buffer distances. Numerous statistical models were examined for each of the forty versions of catchment-derived landscape metrics and their corresponding nitrogen and phosphorous sample site concentrations. Final landscape indicators were selected as the best performing models of catchment interval distance and landscape metric combinations. The landscape indicator models were then utilized in estimating nitrogen and phosphorus concentrations in streams for individual grid cells across the entire region. The indicator map results serve as a tool for targeting areas for intensive sampling in an effort to improve 303(d) listings for nutrients.

Keywords: landscape indicators, landscape ecology, nutrients, phosphorous, nitrogen, streams, water quality, assessment

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