TMDL Modeling of Fecal Coliform Bacteria with HSPF

Abstract

Fecal coliform TMDLs were developed for nine watersheds in Virginia using theHSPF model. The primary HSPF algorithms used to simulate FC loading and fate in the modelsare described in detail. Parameter values are summarized for all HSPF parameters related toFC simulation, as well as source data used external to the model for developing input loadsfrom the various individual FC sources. Although there are many areas of uncertainty inmodeling fecal coliform, a scientific approach was used in the evaluation of sources, therepresentation of the sources, and the evaluation of parameters used to simulate fecal coliformfate and transport with the HSPF model for nine sub-watersheds. The similarity of sourcereductions called for in each of the nine TMDLs support recommendations for the regionalapplication of key results from TMDL studies to watersheds with similar sources and for the useof adaptive implementation as presented in a recent National Research Council report toCongress assessing the scientific basis of TMDLs (NRC, 2001).