ARS | Publication request: Including Sediment-Associated Bacteria Resuspension and Settling in SWAT Predictions of Microbial Water Quality

Submitted to: Annual International SWAT Conference
Publication Type: Abstract Only
Publication Acceptance Date: May 27, 2009
Publication Date: August 4, 2009
Citation: Kim, J., Pachepsky, Y.A., Shelton, D.R., Coppock, C.R., Cho, K.H. 2009. Including Sediment-Associated Bacteria Resuspension and Settling in SWAT Predictions of Microbial Water Quality. 2009 International SWAT Conference. Book of Abstracts. August 5-7, 2009. University of Colorado at Boulder. Boulder, Colorado. Texas AgriLife Research, Texas A&M University, USDA-Agricultural Research Service:60.

Technical Abstract: Streambed sediments have been shown to serve as environmental reservoirs for bacteria, including pathogenic strains. The Soil and Water Assessment Tool (SWAT) has been augmented with bacteria subroutine in 2005. Bacteria die-off is the only in-stream process considered in the current SWAT. The purpose of this work was to evaluate the potential significance of bacteria resuspension and settling for the SWAT microbial water quality simulations. In the newly developed submodule, bacteria were partitioned into free-floating and sediment-associated bacteria. Only sediment-associated bacteria were allowed to settle with depositing sediment while both bacteria were involved in sediment resuspension. The SWAT with the bacteria resuspension-settling submodule was applied to the Little Cove Creek watershed, Pennsylvania, with forestry, dairy pastureland, and field crop land uses. Streamflow, E. coli in water and streambed, and weather have been monitored for 2 years. E. coli in streambed was the model input, and was approximated with a log-scale sine curve function from monitored data. Observed E. coli in streambed peaked in summer to the values of 2E+5 CFU/g whereas in winter they decreased to 2E+2 CFU/g. Hydrologic parameters were calibrated with the monitored streamflow, and model performance was evaluated with monitored E. coli in stream water. The sediment-associated bacteria resuspension explained the E. coli persistence in stream water while surface runoff was the important source for the peak E. coli in stream water. Results indicated that improvements in sediment and sediment-associated bacteria transport components in SWAT could strengthen SWAT capability to predict bacteria fate and transport in streams.