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Estimating Summer Nutrient Concentrations in Northeastern Lakes from SPARROW Load Predictions and Modeled Hydraulic Residence Time
Milstead, Bryan, Jeff Hollister, R. Moore, AND H. Walker. Estimating Summer Nutrient Concentrations in Northeastern Lakes from SPARROW Load Predictions and Modeled Hydraulic Residence Time. PLoS ONE . Public Library of Science, San Francisco, CA, 8(11):1-15, (2013).
Global nutrient cycles have been altered by use of fossil fuels and fertilizers resulting in increases in nutrient loads to aquatic systems. In the United States, excess nutrients have been repeatedly reported as the primary cause of lake water quality impairments. Setting nutrient criteria that are protective of a lakes ecological condition is one common solution; however, the data required to do this are not always easily available. A useful solution for this is to combine available field data (i.e., The USEPA’s National Lake Assessment (NLA)) with nutrient load models (i.e., USGS SPARROW model) to estimate summer concentrations across a large number of lakes. In this paper we use this combined approach and compare the observed nitrogen and phosphorus concentrations in Northeastern lakes from the 2007 National Lake Assessment to those predicted by the Northeast SPARROW model. We successfully calibrated the SPARROW predictions to the NLA observations with the use of Vollenweider equations, simple input-output models that predict nutrient concentrations in lakes based on nutrient loads and hydraulic residence time. This allows us to better predict summer concentrations of nitrogen and phosphorus in Northeastern lakes and ponds. On average we improved our predicted concentrations of nitrogen and phosphorus with Vollenweider models by 18.7% for nitrogen and 19.0% for phosphorus. These improved predictions are now being used to model ecosystem services (e.g., aesthetics) and dis-services (e.g. cyanobacterial blooms) for ~18,000 lakes in the Northeastern United States.
The Northeast SPARROW model predicts long-term average annual nitrogen and phosphorus loads and flow to stream segments in the Northeast United States (HUC region 01 &2). Predictions are based on land cover, atmospheric deposition, soils, climate, and point source inputs for each steam segment’s catchment. In this paper we provide methodologies to aggregate the stream inputs to lakes and to calibrate the SPARROW predictions to the summer N & P levels observed during the 2007 National Lake Assessment. This provides information on nutrient concentrations in ~18000 lakes in the Northeast that are standardized to summer conditions when problems associated with nutrients are most severe. These data will be useful to lake managers, researchers, and state regulatory agencies interested in the development of nutrient criteria for lakes. The approach can be extrapolated to other areas of the country. The input data and an R-script that replicates all analyses and figures are included with the paper.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB
ATLANTIC ECOLOGY DIVISION
MONITORING AND ASSESSMENT BRANCH