HR: 1340h
AN: H43E-0412    [Abstracts]
TI: Measuring uncertainty in modeling toxic concentrations in the Niagara River
AU: * Franceschini, S
EM: sf5@buffalo.edu
AF: Dept. of Civil, Structural and Environmental Engineering, State University of New York at Buffalo, 207 Jarvis Hall North Campus, Buffalo, NY 14260 United States
AU: Tsai, C
EM: ctsai4@buffalo.edu
AF: Dept. of Civil, Structural and Environmental Engineering, State University of New York at Buffalo, 207 Jarvis Hall North Campus, Buffalo, NY 14260 United States
AB: In spite of the renowned history of the Niagara River as a recreational and tourist attraction, little is known about the variability of the natural phenomena linked to the fate and transport of contaminants along the natural channel that connects Lake Erie to Lake Ontario. Previous studies of the Niagara River have focused on water quality modeling using one-dimensional deterministic models. Only recently, the work by Franceschini (2004) has evaluated probabilistically the influence on the estimated concentrations at the end of the Niagara River of few model variables and parameters with inherent variability. Several factors contribute to the uncertainty of the estimated concentrations. Toxic concentrations in the Niagara River depend on the randomly varying magnitude of the flow, the processes of decay, volatilization, and sorption which the substances undergo, the rate of contaminated suspended sediment deposition and resuspension, the variability of the input sources and seasonal schedules of water diversions for hydropower production. This paper proposes to analyze the variability of the toxic concentrations in the Niagara River with respect to the variability of selected hydraulic components (e.g. flow velocity and dispersion coefficient), upstream incoming concentrations and non-point source loadings. A comparison of the uncertainty of the results obtained during different water diversion schedules for hydropower productions will be also analyzed. The influence of climate change will be investigated with respect to temperature and precipitation variations. The uncertainty of the model results will be analyzed by Point Estimate Methods (PEMs) and specifically the Modified Rosenblueth method (Tsai and Franceschini 2004) will be used. The application of PEMs to environmental engineering problems has recently attracted some attention. Compared to other uncertainty analysis methods, PEMs require a substantially smaller computational effort, for a comparable degree of accuracy in the estimation of the first few statistical moments of a model output distribution. Furthermore, the probabilistic analysis can be used as a more rigorous method to compare the modeled results with established water quality criteria. In this study, the toxic concentrations computed at the end of the Niagara River and their estimated variability will be compared with field data measurements. The purpose of this comparison is two-fold: (a) to evaluate the accuracy of the Modified Rosenblueth method in measuring the uncertainty of toxic concentration in the Niagara River and (b) to quantify the risk of exceeding established water quality standards when such uncertainty is accounted for.
DE: 1869 Stochastic processes
DE: 1871 Surface water quality
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting