HR: 1340h
AN: H43E-0404    [Abstracts]
TI: Eutrophication Model Accuracy - Comparison of Calibration and Verification Performance of a Model of the Neuse River Estuary, North Carolina
AU: * Bowen, J D
EM: jdbowen@uncc.edu
AF: University of North Carolina at Charlotte, Civil Engineering Department, Charlotte, NC 28223 United States
AB: A modified version of an existing two-dimensional, laterally averaged model (CE-QUAL-W2) was applied to predict water quality conditions in the lower 80-km of the Neuse River Estuary. Separate time periods were modeled for calibration and verification (model testing). The calibration time period ran from June 1997 to December 1999, while the verification time period ran from January to December 2000. During this time the estuary received two periods of unusually high inflows in early 1998 and again in September and October 1999. The latter rainfall event loaded the estuary with the equivalent of nearly two years worth of water and dissolved inorganic nitrogen in just six weeks. Overall, the level of calibration performance achieved by the model was comparable to that attained in other eutrophication model studies of eastern U.S. estuaries. The model most accurately simulated water quality constituents having a consistent spatial variation within the estuary (e.g. nitrate, salinity), and was least accurate for constituents without a consistent spatial variation (e.g. phosphate, chlorophyll-a). Calibration performance varied widely between the three algal groupings modeled (diatoms and dinoflagellates, cryptomonads and chlorophytes, cyanobacteria). Model performance during verification was comparable to the performance seen during calibration. The model's salinity prediction capabilities were somewhat better in the validation, while dissolved oxygen performance in the validation year was slightly poorer compared to calibration performance. Nutrient and chlorophyll-a performance were virtually the same between the calibration and verification exercises. As part of the TMDL analysis, an unsuccessful attempt was made to capture model error as a component of model uncertainty, but it was found that model residuals were neither unbiased nor normally distributed.
DE: 9350 North America
DE: 4845 Nutrients and nutrient cycling
DE: 4855 Plankton
DE: 6309 Decision making under uncertainty
DE: 4235 Estuarine processes
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting