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Evaluation and Application of Microbial Source Tracking Methodologies for TMDL Development in Texas

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Watershed ManWatershed Management to Meet Water Quality Standards and TMDLS (Total Maximum Daily Load) Proceedings of the 10-14 March 2007, San Antonio, Texas  701P0207.(doi:10.13031/2013.22477)
Authors:   J Andrew Sullivan, Faith Ann Hambleton
Keywords:   Keywords, bacteria source tracking, E coli, TMDL

Federal regulations require that Total Maximum Daily Loads(TMDLs) be conducted to restore impaired uses on waterbodies not attaining water quality standards. Addressing bacteria related water quality impairments involves identification and quantification of potential sources. DNA based source tracking tools have the potential to greatly enhance the source assessment phases of this process. The Texas Commission on Environmental Quality Studies have conducted several studies throughout Texas using several different library based methods. . The studies employed libraries ranging from1,058 to more than 120,500 isolates. The number of classification categories ranged from 6 to 21. The studies produced unknown classification rates ranging from 10% to 46.25%.. Rates of correct classification ranged from 9%-100% across all of the watersheds and methods. The results from these studies indicate that additional refinement is necessary before the methods are used in TMDL development with any certainty. The use of broad categories, large libraries and multiple methods could possibly enhance the performance of this tool for TMDL development. However, microbial source tracking tools should be utilized in concert with other methods to fully characterize sources for the development of effective restoration plans.

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