ARS | Publication request: Evaluating uncertainty in E. coli retention in vegetated buffer strips

Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: March 27, 2007
Publication Date: April 25, 2007
Citation: Guber, A.K., Pachepsky, Y.A., Sadeghi, A.M. 2007. Evaluating uncertainty in E. coli retention in vegetated buffer strips. BARC Poster Day, April 25, 2007.

Technical Abstract: Vegetated buffer 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. 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. These factors cannot be defined accurately and time-independently for a particular VFS. Only probability distributions can be inferred for those factors. This creates an unavoidable uncertainty that cannot be ignored and has to be factored into 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. Analogous 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 useful in making decisions on VFS placement with respect to manure-borne pathogens.