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SPARROW Modeling Case Study

SPARROW Modeling Case Study. By Jahangir Alam and Jonathan Goodall Dept of Civil Engineering University of South Carolina. Research Question: What is the impact of land use change in the U.S. from 1992 to 2001 on nitrogen delivery?. Observations Database: 400 sites.

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SPARROW Modeling Case Study

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  1. SPARROW Modeling Case Study By Jahangir Alam and Jonathan Goodall Dept of Civil Engineering University of South Carolina Research Question: What is the impact of land use change in the U.S. from 1992 to 2001 on nitrogen delivery?

  2. Observations Database: 400 sites For each NAWQA site where flow and concentration are available for time period of interest, relate spatially-referenced watershed characteristics to observed in-stream load.

  3. SPARROW Equations TNi = observed nitrogen loading at station i Sn,j = nitrogen source n for reach j Zj = watershed attributes for reach j Ti,j = travel time from reach j to station i βn , α, and k = calibration parameters Smith, R.A., Schwarz, G.E., and Alexander, R.B., 1997, Regional interpretation of water-quality monitoring data, Water Resources Research, 33, 12, 2781-2798. http://water.usgs.gov/nawqa/sparrow

  4. SPARROW SPARROW considers to basic processes in nitrogen transport: (1.) Overland transport (2.) In-stream transport (both are assumed to follow 1st order decay) Overland Transport In-stream Transport

  5. SPARROW Calibration Eno River Basin Nitrogen Observation Site Little Creek Sum all sources for all catchments upstream of an observed loading

  6. Example of Previous SPARROW Application: Nitrogen Transport to the Gulf Atmosphere Agriculture Point Sources Alexander, R.B., Smith, R.A., and Schwarz, G.E., 2000, Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico, Nature, 403, 758-761.

  7. Procedure • Prepare land cover data • Prepare loading data • Update “baseline” SPARROW inputs with 1992 and 2001 specific data

  8. Procedure • Prepare land cover data • Prepare loading data • Update “baseline” SPARROW inputs with 1992 and 2001 specific data

  9. National Land Cover Dataset (NLCD) • Products include classifications for 1992, 2001, and 2006 (in development), and change product (1992 to 2001) • 30m resolution; 25 classes • http://www.epa.gov/mrlc

  10. Urbanization in Columbia, SCChange Product (1992 to 2001) map of NLCD 2001 Colored Pixels are 2001 NLCD Black Pixels Change to Urban from 1992 to 2001

  11. Urbanization in Charlotte, NCChange Product (1992 to 2001) map of NLCD 2001 Colored Pixels are 2001 NLCD Black Pixels Change to Urban from 1992 to 2001

  12. Land Cover Change in the South East U.S. * all areas reported in units of km2

  13. Land Cover Change in South East U.S.(1992 to 2001)

  14. Summarizing Land Cover Modeling Units 1992 61,215 Watersheds 2001 1992 2001

  15. Procedure • Prepare land cover data • Prepare loading data • Update “baseline” SPARROW inputs with 1992 and 2001 specific data

  16. Data Preparation WorkflowTime Series Data Identify time series of interest Create sites.csv file Reformat files from WaterML to LOADEST inputs Run FetchWaterML.exe tool to create WaterML Cache Runkel, R.L., Crawford, C.G., and Cohn, T.A., 2004, Load Estimator (LOADEST): A FORTRAN Program for Estimating Constituent Loads in Streams and Rivers: U.S. Geological Survey Techniques and Methods Book 4, Chapter A5, 69 p.

  17. Creating a Cache of HIS Data Sites.csv c:> FetchWaterML.exe sites.csv ./daily-discharge-2/ input sites file output directory Downloaded WaterML Files (one for each time series requested)

  18. Estimating Load from Flow and Concentration

  19. TN Loading Data 1988-1996 Average Loading (kg/yr) < 5.0x106 5.0x106 - 10.0x106 10.0x106 - 20.0x106 20.0x106 - 50.0x106 > 50.0x106 1997-2005

  20. Difference, ‘92 and ‘01 Loadings Loading Difference (kg/yr) > - 5.0x106 -5.0x106 - 0 0 - 5x106 > 5.0x106 + (orange/red) increase in loading from 92 to 01 - (blue) decrease in loading

  21. Procedure • Prepare land cover data • Prepare loading data • Update “baseline” SPARROW inputs with 1992 and 2001 specific data

  22. Results

  23. Results

  24. Conclusions • Our model suggests that nitrogen loadings to streams have decreased from the 1990s to the 2000s by on average 1 kg/ha/yr (or roughly 10%). It also shows a shift in the relative contribution of nitrogen sources with a greater contribution from urban land use areas in the 2000s compared to the 1990s. That said, the current model assumes fertilizer application rates, point sources loadings, and animal populations are constant over time because it is difficult to obtain differences between these numbers of the two time periods of analysis.

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