MODELING PATHOGEN FATE AND TRANSPORT IN WATERSHEDS TO SUPPORT TMDLS

Authors: BENHAM, BRIAN - VA TECH, BLACKSBURG,VA; BAFFAUT, CLAIRE - U. OF MISSOURI,COLUMBIAMO; ZECKOSKI, REBECCA - VA TECH, BLACKSBURG, VA; Pachepsky, Yakov; MANKIN, KYLE - KANSAS ST U.,MANHATTAN,KS; Sadeghi, Ali; BRANNAN, KEVIN - VA TECH, BLACKSBURG,VA; SOUPIR, MICHELLE - VA TECH, BLACKSBURG,VA; HABERSAC, MATHEW - VA TECH, BLACKSBURG, VA

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2006
Publication Date: 7/1/2006
Citation: Benham, B.L., Baffaut, C., Zeckoski, R.W., Pachepsky, Y.A., Mankin, K.R., Sadeghi, A.M., Brannan, K.M., Soupir, M.L., Habersac, M.J. 2006. Modeling Pathogen Fate and Transport in Watersheds to Support TMDLs. American Society of Agricultural and Biological Engineers. 49(4):987-1002.

Interpretive Summary: Fecal contamination of surface waters is a critical water-quality issue, leading to documented human illnesses and deaths. Total Maximum Daily Loads (TMDLs) specifies the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and allocates pollutant loadings among point and nonpoint pollutant sources. By law, EPA must approve or disapprove lists and TMDLs established by states, territories, and authorized tribes. Computer models have been recently developed to support TMDLs by evaluating the effect of remediation measures on the bacterial water quality. This paper describes HSPF, SWAT, and load-duration watershed models used to simulate microbial transport, and presents case studies demonstrating their use. Specific research needs are outlined to improve fecal microbe modeling and support the TMDL process.

Technical Abstract: Fecal contamination of surface waters is a critical water-quality issue, leading to documented human illnesses and deaths. Total Maximum Daily Loads (TMDLs), which set pollutant limits within a watershed and can guide remediation efforts, have been developed to address fecal-microorganism impairment of numerous water bodies in the U.S. Watershed models are widely used to support TMDLs, although their use for fecal bacteria simulation is in its infancy. This paper provides an overview of fecal microorganism fate and transport within watersheds, describes current watershed models used to describe microbial transport, and presents case studies demonstrating their use. Two models for fecal bacteria source characterization are discussed. Bacterial modeling capabilities and limitations of two widely used watershed models, HSPF and SWAT, as well as the load-duration method of setting TMDL limits, are described. Case studies of each model and method are presented and discussed. Specific research needs are outlined to improve fecal microbe modeling and support the TMDL process.