Buffers and vegetative filter strips

Helmers, M.J. , Isenhart, T.M. , Dosskey, M , Dabney, S.M. , Strock, J.S.

Buffers have been found to be most effective in trapping particulate pollutants. In addition, the export of soluble pollutants is expected to decrease when infiltration is maximized. Narrow buffers have also been shown to be effective in reducing the export of particulate pollutants when the integrity of the system is maintained. This highlights that one of the primary functions of buffers is to slow surface water movement which reduces the export of pollutants, particularly particulate pollutants, and narrow strips of dense grass can function in this capacity and provide water quality benefits (Dabney et al. 2006). Also, these narrow strips could be used in-field as vegetative barriers to slow pollutant movement in-field and control concentrated flow erosion. To maximize infiltration of runoff, wider buffers or a greater buffer area to source area should be used. Research has found a significant range in buffer performance with reported sediment trapping efficiencies ranging from 41% to 100% and infiltration efficiencies ranging from 9% to 100%. Buffers that interact with shallow groundwater moving through the root zone have been found to remove nitrate. Nitrate-removal efficiency has been found to vary between 25 and 100 percent, with mean nitrate-removal efficiencies ranging from 48 to 85 percent in shallow groundwater under re-established riparian buffers (Simpkins et al. 200X).