BUFFERS AND VEGETATIVE FILTER STRIPS

Authors: HELMERS, M - IOWA STATE UNIVERSITY; ISENHART, T - IOWA STATE UNIVERSITY; DOSSKEY, M - NRCS; Dabney, Seth; STROCK, J - UNIVERSITY OF MINNESOTA

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Book / Chapter
Publication Acceptance Date: 7/1/2007
Publication Date: 10/1/2008
Citation: Helmers, M.J., Isenhart, T., Dosskey, M., Dabney, S., Strock, J. 2008. Buffers and vegetative filter strips (Chapter 4). In Final Report: Gulf Hypoxia and Local Water Quality Concerns Workshop. Sept. 26-28, 2005, Ames, IA. American Society of Agricultural and Biological Engineers (ASABE), St. Joseph, MI. pp. 43-58 (Book Chapter).

Interpretive Summary: Buffers are widely used to improve the quality of water leaving agricultural fields. This literature review was undertaken to determine the state of knowledge of the cost effectiveness of buffers for improving improve water quality and to identify existing knowledge gaps. Buffers are areas of permanent vegetation located within and between agricultural fields and the water courses to which they drain. These buffers are intended provide setbacks for agrichemical application and to intercept and slow runoff thereby providing water quality benefits. In addition, in many settings they are intended to intercept shallow groundwater moving through the root zone below the buffer and so to remove dissolved contaminants. In designing the buffer systems, the flow of either surface water or groundwater through the buffer should be maximized and the integrity of the vegetation in the buffer should be maintained. While buffers have the potential to provide significant water quality improvement in-field management needs to be considered and best management practices implemented since buffers best serve as polishers of water moving through them.

Technical Abstract: Buffers and filter strips are areas of permanent vegetation located within and between agricultural fields and the water courses to which they drain. These buffers are intended to intercept and slow runoff thereby providing water quality benefits. In addition, in many settings they are intended to intercept shallow groundwater moving through the root zone below the buffer. The performance of buffer systems will depend on the field, topographic, and climatic conditions at the site. 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. In designing the buffer systems, the flow of either surface water or groundwater through the buffer should be maximized and the integrity of the vegetation in the buffer should be maintained. While buffers have the potential to provide significant water quality improvement in-field management needs to be considered and best management practices implemented since buffers best serve as polishers of water moving through them. Care should be taken to design buffer systems such that the interaction of surface and ground water with the buffer system is maximized. One area in which the water quality benefits may be reduced is in areas where there is significant subsurface drainage such that subsurface flow is short-circuited through the drain lines so that there is minimal interaction with the buffer zone. There is a need to better understand the in-field performance of buffers, where buffer integrity may be comprised by lack of vegetation or features that allow bypass flow to occur through the buffer. Such research would provide much needed information on the performance of this conservation practice under likely common field conditions where non-idealized flow may occur in order to better evaluate the costs and benefits of establishing buffer systems on a watershed scale.