Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 27, 1999
Publication Date: N/A
Technical Abstract: Little is known about the impact of preferential flow pathways on the biological function of riparian buffers. A riparian/wetland system associated with a first-order stream in an agricultural ecosystem provides an example. Under base-flow conditions, the stream is fed primarily by groundwater exfiltration in the wetland. Differences in hydraulic conductivity within the wetland soil profile, in conjunction with marked stratification of soil profile denitrification activity, allows exfiltrating groundwater to bypass biologically active zones and limits the removal of nutrients. Under winter high-flow conditions, groundwater also exfiltrates directly to the stream through an extensive network of macropores in the stream channel, with evidence for direct movement of groundwater from the underlying aerobic sand aquifer. Flow of surface water through secondary channels in the wetland limits interaction of field drunoff with the riparian wetland and reduces the potential for retention o runoff sediment. This substantial potential for preferential movement of water though wetland systems limits the biogeochemical function of riparian systems in removing agricultural pollutants.