Submitted to: Joint Assembly of the European and American Geophysical Unions
Publication Type: Abstract only
Publication Acceptance Date: 4/1/2007
Publication Date: 5/22/2007
Citation: Pachepsky, Y.A., Guber, A.K., Sadeghi, A.M., Shelton, D.R. 2007. Uncertainty assessment for the vegetated filter strip performance with respect to manure-borne pathogens. Joint Assembly of the European and American Geophysical Unions. Paper No. B41C-02. Interpretive Summary:
Technical Abstract: Vegetated filter strips (VFS) separate fields and pastures from streams and other water bodies and can serve as barriers that prevent sediment and agricultural chemicals from entering waterways and spoiling them. Growing concern about the manure-borne pathogens as water pollutants defines the need to evaluate efficiency of VFSs with respect to pathogens. Selecting locations for the VFS placement can be done with the SWAT model allows for a comprehensive description of agricultural practices, and has proven to be efficient in applications to watershed with a substantial agricultural component. Functioning of VSF as barriers for manure-borne pathogens to the large extent depends on vegetation status, soil infiltration capacity in VFS, and rainfall intensity and duration. The effect of these factors on the pathogen breakthrough in VFS needs to be researched at the time scales smaller than the computation interval of one day that SWAT uses. The downscaling is necessary which creates an unavoidable uncertainty that cannot be ignored and has to be factored into the VFS efficiency estimates. We have developed the model STIR to simulate the overland transport and loss to infiltration of manure-borne pathogens in VFS. This model was used in Monte Carlo simulations in which the input parameters of vegetation, soil, rainfall, and pathogen load were drawn from probability distribution functions. The result of such simulations was also the probability distribution of the VFS efficiency. For the example of our experimental 6-m long VFS at the 20% slope, The VFS efficiency was less than 100% in 5% of cases, and less than 75% in 2.5% of cases. Relatively long high-intensity rainfalls, low hydraulic conductivities, high soil moisture contents before the rainfall, and high spread of surface water velocities were the main sources of the strip partial failure. Similar simulations can be done for any other VFS with site-specific soil and weather properties, and the results on terms of efficiency probabilities can be used in making decisions on VFS placement with respect to manure-borne pathogens.