Uncertainty in dissolved oxygen prediction due to variability in algal photosynthesis

Abstract

The contribution of variance in river community metabolism to overall uncertainty in predictions from dissolved oxygen models is evaluated using Monte Carlo simulation. Results using a modification of the Streeter-Phelps model to include a term for mean daily net production show that uncertainty in parameters used to describe community metabolism must be considered when probability distributions of dissolved oxygen in rivers are estimated. This conclusion is shown to be valid for a range of conditions and is therefore applicable to all but heavily polluted or highly turbid streams. Use of a refined version of the oxygen balance equation that accounts for diel variation in algal productivity demonstrates that variance in dissolved oxygen in rivers is likely to be much larger than that predicted by models that use mean daily values of net production.