WATERSHED-SCALE FATE AND TRANSPORT OF BACTERIA
Transactions of the ASAE , 52 , 2009

Chin, D.A., Sakura-Lemessy, D., Bosch, D.D., Gay, P.A.

The added dimensionality provided by using multiple models to predict the fate and transport of bacteria at the watershed scale were investigated. Both HSPF and SWAT were applied to the 15.6 km2 catchment K of the Little River Experimental Watershed (LREW) in Georgia. Over the seven‐year period from 1996 to 2002, SWAT provided a more accurate description of fecal coliform concentrations, with an NSE of 0.73 compared to 0.33 for HSPF. For this particular watershed, the SWAT process equations are more representative of the watershed‐scale fate and transport of bacteria than the HSPF process equations. Based on this comparative analysis, it can be inferred that elevated levels of fecal coliform in the receiving stream are primarily due to in‐stream sources. This source characterization could not be achieved by using only the HSPF model, which indicates a much greater contribution from groundwater and terrestrial nonpoint sources. A model‐averaging approach in which a weighted average of the HSPF and SWAT predictions are used to predict bacteria concentrations in the receiving stream demonstrates that model weights can be determined such that the NSE of the combined models will be greater than either of the models taken individually. However, in the present case, the marginal improvements in NSE obtained through this integration were small.