A preliminary study on coastal water quality monitoring and modeling.

The overall objective of this study was to assess the impact of individual rainfall events on Lake Pontchartrain water quality and risk to swimmers. Indicator organisms in lake water under dry weather conditions, in storm water runoff (prior to dilution with lake water), and in the outfall plume within the lake following storm events were monitored and quantified. Results indicated that drainage canals constitute a significant microbial loading to lake waters. Significant reductions of indicator microbes are observed in the water column following two to three days after storm pumping events into the lake. A mathematical model incorporating advection, dispersion, and bacterial die-off gives fairly good prediction on E. coli, enterococcoi, and fecal coliform titers. The somewhat under estimation by model suggests re-suspension of sediment and re-introduction of the indicator organisms that attached to the sediment back into the water column. Future direction of model development should include the mechanism of re-suspension and survival of indicator organisms in sediment.