A stochastic simulation study of the biochemical oxygen demand and dissolved oxygen in streams and estuaries

Abstract

Using Dobbins' deterministic equations Stochastic simulation was used to determine if, for K1, K2 and K3 randomized, the average BOD and DO would be close to its mean. The BOD and DO was determined by using the mean K values in Dobbins' equations. Similar calculations were performed where LO, and La, and DB were randomized and the average BOD and DO determined. The same procedure was used with Custer and Krutchkoff's stochastic model randomizing K2 and Kd. Tables were calculated for each situation. These indicate that the average BOD and DO values calculated for streams lie within three standard errors of their respective means. The average BOD and DO values of estuaries lie close to their respective means. This indicates that the variation in the K values of the estuarial model does not adversely effect the mean state Poisson distribution of the BOD and DO. A study was also made to determine if the variation in the previously discussed parameters found in the stream equations account tor the variance in the BOD and DO or whether this variance is in the stochastic process. Tables and graphs were constructed showing the observed and predicted variances of the BOD and 00 for each stream situation. These indicate that only a small part of the variance can be attributed to the variation in the non-stochastic parameters. Therefore the majority of the variance must be found in the stochastic process.