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Estimation of Fecal Coliform Loadings to Galveston Bay

by Reem Jihan Zoun, M.S.E.

ABSTRACT

Elevated fecal coliform concentration in Galveston Bay causes water quality impairment for oyster water use in different locations of the bay. This thesis presents analysis of bacterial monitoring data using Geographic Information System (GIS) in six impaired TCEQ Water Quality segments not meeting water quality standard for oyster water use. It is shown that several high concentration zones of bacteria exist in the study area, and the causes and effects of contamination are situated within close proximity to one another. Bacterial concentrations are log-normally distributed in the detectable range of concentration. A regional GIS model is presented for estimation of non-point fecal coliform loadings from adjacent and upstream watersheds. Non-point loadings of bacteria are estimated using relationships between land use and expected bacterial concentration. Loadings from upstream watersheds are decayed along the streams and channels entering the bay system in the model. A methodology for estimation of fecal coliform contribution from Laughing Gull population in the bay is presented. A CSTR model accounting for the total loadings and decay of bacteria in the bay gives a bay concentration of fecal coliform in the same magnitude as the observed one. Non-point loadings from upstream watersheds represented the largest contributor of fecal coliform in Galveston Bay. Retention in upstream watershed segments should significantly lower loadings to the bay segments. Estimated fecal coliform loadings from Laughing Gull populations showed significant contributions to West Bay and Lower Galveston Bay.

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