Sensitivity to Uncertainty in a Phytoplankton-Oxygen Model for Lowland Streams

Straten, G. van & de Boer, B. (1979). Sensitivity to Uncertainty in a Phytoplankton-Oxygen Model for Lowland Streams. IIASA Working Paper. IIASA, Laxenburg, Austria: WP-79-028

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Abstract

The applicability of water quality models depends upon the quality of the parameter estimates. A phytoplankton-oxygen model developed for canalized lowland streams is tested against data from a limited plug following measurement program. The accuracy of the parameter estimates is limited by the inaccuracy of the BOD measurement in the presence of algae. Other sources of parameter uncertainties are: (i) site dependency of parameters lumping complex subsystems, such as the BOD decay rate coefficient, having a higher value directly after a waste discharge, and (ii) time dependency of lumped parameters, such as the algal death rate coefficient. A sensitivity analysis, based on the solution of the sensitivity equations of the model, is then performed to provide some insight into the effects of parameter uncertainties on model results. It appears that the growth and death rates of algae dominate the phytoplankton, BOD and oxygen behaviour, and that a separate estimate in the absence of accurate BOD measurements is difficult to obtain without additional information.

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