Sunday, November 12, 2006

Use of Buffers to Reduce Nitrogen Transport to Water Bodies.

Ali Fares1, Ahmet Dogan2, and Akitsu Kimoto2. (1) Univ of Hawaii at Manoa, 1910 East-West Road, Honolulu, HI 96822, (2) Univ of Hawaii-Manoa, 1910 East-West Road, Honolulu, HI 96822

Non-point source pollution has been recognized as the greatest threat to water quality. It  is difficult to control it because of its spatially and temporally varied disperse origin. Nitrogen is one of the essential nutrients for life while it is one of the main non-point source pollutants. N pollution poses human and ecosystem health risk.  The main source of N pollution is agricultural practices. Riparian buffers, which are areas of permanent vegetation adjacent to a fresh water body can reduce the impacts of non-point source pollution on water quality by (1) filtering polluted overland and subsurface flow from adjacent agricultural fields; (2) protecting banks of water bodies against erosion; (3) filtering polluted air; (4) avoiding intensive growth of aquatic macrophytes by canopy shading; (5) improving the microclimate in adjacent fields; and (6) creating new habits in land/in-land water ecotones.  Numerous studies showed that topographical factors, soil factors, hydrological factors, and vegetation types could affect the performance of riparian buffers.  Variable estimation methods or models have been used to predict the effects of riparian buffers on nutrient load reduction.  Optimal designs of riparian buffers and buffer installation strategies have been discussed and efforts have focused on the environmental and economical benefits of buffers.  Several case studies and modeling applications investigating the effects of temporal and spatial variability in riparian buffers have also been discussed.  This chapter presents also our current knowledge of the nitrogen removal function of riparian buffers.  Educational and extension efforts should focus on economic benefits of riparian buffers to farmers through the different national incentive program; this would result in more adoption of riparian buffers and non-point source pollution control.  There is still a need for establishing a tool to provide economically and environmentally beneficial buffer designs on specific situations.