Click on “Download PDF” for the PDF version or on the title for the HTML version.
If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.
Fecal Coliform TMDL Case Study for a Coastal Mississippi Estuary
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Pp. 377-382 in Total Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March 11-13, 2002 Conference, (Fort Worth, Texas, USA) 701P0102.(doi:10.13031/2013.7583)
Authors: K. A. Meherg
Keywords: TMDL Case Studies, TMDL Development and Process, Field and Watershed Scale Modeling
St. Louis Bay is a vital waterbody in the Mississippi Gulf Coast Region with designated uses of
shellfish harvesting and primary contact recreation. Several waterbody segments in the St. Louis
Bay watershed are on the Mississippi 1998 Section 303(d) List of Waterbodies as impaired due
to pathogens, which are indicated by the presence of fecal coliform bacteria. A comprehensive
hydrologic, hydrodynamic, and water quality modeling system was developed by the Civil
Engineering Department at Mississippi State University to support the development of TMDLs
for the St. Louis Bay estuary and other 303(d) listed waterbody segments within the watershed.
(Download PDF) (Export to EndNotes)
The modeling system includes the Nonpoint Source Model (NPSM) and the Environmental
Fluid Dynamics Code (EFDC) and considers both point source and nonpoint source loadings.
The Mississippi Department of Environmental Quality (MDEQ) and the Environmental
Protection Agency (EPA) have conducted intensive field data acquisition projects to provide
additional data to facilitate better understanding of this complex estuarine system and to provide
data for model calibration and validation.
The modeling system predicted a reduction in the total fecal coliform load of approximately 27
percent was necessary for St. Louis Bay to meet shellfish harvesting water quality standards.
Because over 99 percent of the allocated load is contributed by nonpoint sources, those sources
were the focus for reduction. The waters of St. Louis Bay are in various stages of restriction for
shellfish harvesting, and one of the goals of the St. Louis Bay fecal coliform TMDL is to
improve water quality to allow for upward reclassification of the waters to once again allow
shellfish harvesting where appropriate. Additional stakeholder input is needed to develop an
appropriate implementation plan for this watershed. However, the proactive efforts of several
programs and organizations that already focus conservation activities in the St. Louis Bay
watershed provide the opportunity for this to continue as a TMDL success story.