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Estimation Of TMDLs And Margin Of Safety Under Conditions Of Uncertainty
Citation:
HANTUSH, M. M. Estimation Of TMDLs And Margin Of Safety Under Conditions Of Uncertainty. In Proceedings, World Environmental & Water Resources Congress, Kansas, MO, May 17 - 21, 2009. American Society of Civil Engineers (ASCE), Reston, VA, ,, (2009).
Impact/Purpose:
To present a formal methodology for the estimation of TMDL and MOS as a function of analysis uncertainty, degree of protection provided, and fuzziness in water-quality standards.
Description:
In TMDL development, an adequate margin of safety (MOS) is required in the calculation process to provide a cushion needed because of uncertainties in the data and analysis. Current practices, however, rarely factor analysis' uncertainty in TMDL development and the MOS is largely arbitrarily selected. This paper presents a formal methodology for the estimation of TMDL and MOS as a function of analysis uncertainty, degree of protection provided, and fuzziness in water-quality standards. The probabilistic methodology is demonstrated through a hypothetical lake-sediment phosphorus model and eutrophication problem. Impacts of parametric uncertainty on the TMDL distribution and MOS are discussed. The performance of the widely used first-order approximation (FOA), with Gaussian and log-normal assumptions, is tested against the Monte Carlo (MC) method. The dependence of the MOS on the degree of protection provided against violating water quality standard is computed. NOTE: PAPER LISTED UNDER THURSDAY MAY21, 2009, CONCURRENT TECHNICAL SESSIONS XV, 9:00 AM-10:30 AM, WATERSHED, PROBABILISTIC APPROACHES FOR WATERSHED PROCESSES
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