Author
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Boyer, Douglas |
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Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/3/2008 Publication Date: 6/12/2008 Citation: Boyer, D.G. 2008. Fecal coliform dispersal by rain splash on slopes. Agricultural and Forest Meteorology. 148:1395-1400. Interpretive Summary: The movement of fecal pathogens from land to surface and ground water are of great interest because of the public health implications. Best management practices that control the timing, volume, and placement of animal manures are commonly used to limit opportunities for fecal pathogens to enter water bodies. Increased infiltration capacity, water and waste diversions, and vegetated filter strips are used to control fecal pathogen movement in surface runoff. Fecal pathogens transported by rain splash could conceivably bypass physical barriers. The relationship between slope angle and the transport of fecal coliform bacteria by rain splash was studied. Transport of fecal coliform bacteria by rain splash from unobstructed soil surfaces was confirmed and significant. Fecal coliform bacteria splashed up to 2 meters in the downhill direction on steeper slopes. Sequential downhill movement of fecal coliform bacteria by repeated rain splash could transport the bacteria directly to water bodies or saturated areas where they can become entrained in overland runoff. Technical Abstract: The movement of fecal pathogens from land to surface and ground water are of great interest because of the public health implications. Non-structural best management practices that control the timing, volume, and placement of animal manures are commonly used to limit opportunities for fecal pathogens to enter water bodies. Increased infiltration capacity, water and waste diversions, and vegetated filter strips are used to control fecal pathogen movement in surface runoff. Fecal pathogens transported by rain splash could conceivably bypass physical barriers. The relationship between slope angle and the transport of fecal coliform bacteria by rain splash was studied. It was hypothesized that there would be a significant down slope transport of fecal coliform bacteria by raindrops falling on a bare soil surface inoculated with fecal coliform bacteria. Slopes from 0 deg to 40.8 deg were studied. The mean distance splash distance for fecal coliforms was less than 50 mm in all directions at 0 deg slope and more than 500 mm in the downslope direction on a 40.8 deg slope. Maximum splash distances ranged from about 400 mm on the horizontal surface to more than 1900 mm in the downslope direction on the 40.8 deg slope. The observed data were closely matched by a previously published model for rain splash droplet transport. Transport of FC bacteria by rain splash from unobstructed soil surfaces was confirmed and significant. Sequential downhill movement of FC bacteria by repeated rain splash could transport FC directly to water bodies or areas of saturation excess where they will become entrained in overland runoff. Further studies on raindrop and rainfall characteristics, as well as surface cover and soil characteristics, will be necessary to more fully understand the mechanisms of FC transport by rain splash. |
