PREDICTED FLUSHING TIMES AND POLLUTION DISTRIBUTION IN THE COLUMBIA RIVER ESTUARY

Victor T. Neal

Abstract


The observed salinity distribution in the Columbia River Estuary is used to predict the flushing times for various river discharge rates, varying tidal ranges, and varying salinity intrusions. Both the modified tidal prism method and the fraction of fresh water method are used, and the results are compared. The latter method predicts shorter flushing times, while both methods vary m a similar manner with changing river discharge and changing salinity intrusion. Both methods predict a relatively short flushing time for the estuary. The observed salinity distributions under varying conditions are also used to predict the distribution of conservative and non-conservative pollutants. In this case the fraction of fresh water method and the diffusion equation are used. In general, the fraction of fresh water method predicts higher concentrations. "When the lower estuary is divided into two channels, the two methods give quite different results. The diffusion equation method predicts a peak concentration upstream from the outfall rather than at the outfall, when the outfall location is arbitrarily placed at certain locations.

Keywords


estuary flushing; Columbia River; estuary pollution

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