Latin hypercube sampling (LHS) and the mean first-order reliability method
are applied to determine the parameters significantly affecting uncertainty
in the simulated dissolved oxygen (DO) concentrations at the point in the
Zenne River in Brussels, most prone to low concentrations. The DO simulatio
n involves the coupling of a nonpoint pollution load model, a constant trea
tment efficiency model, and a river water-quality model. LHS found that six
of the 53 model parameters significantly contribute to the variance of the
annual mean DO concentration, and five model parameters significantly cont
ribute to the variance in the number of hours that DO concentrations are <2
mg/L. The mean first-order reliability method found that these parameters
accounted for 73.6 and 84.7% of the variance in the respective output featu
res. Reanalysis with LHS, letting only these six parameters be uncertain, c
onfirmed the identification of these parameters as accounting for 78.1 and
83.0% of the respective variances. The identification of key sources of unc
ertainty provided insight with respect to treatment plant operation, model
improvements, and data collection programs.