Submitted to: Riparian Ecology and Management in Multiland Use Watersheds Meetings
Publication Type: Abstract Only
Publication Acceptance Date: December 21, 2000
Publication Date: N/A
Technical Abstract: Riparian buffers are believed to function as natural remediation sites for groundwater-borne agricultural contaminants, but this presupposes certain conditions. One assumption is that water infiltrates in the uplands, travels horizontally as groundwater through the riparian zone, and is discharged into the stream channel. Horizontal groundwater flow through the ewetland soils should ideally supply sufficient contact and residence time within the soil matrix for nutrient removal. Reducing conditions in the anaerobic soil and abundant carbon in the system enable this process to occur. Dense vegetation in these areas allows additional nitrate to be taken up by plants during the growing season. Significant deviations from these conditions may allow contaminated groundwater to enter surface waters. The study site, a small headwater stream in an agricultural setting, shows evidence of nutrient delivery by contaminated groundwater. Groundwater flow paths within the riparian zone appear to deviate considerably from a lateral direction. The region in which high nutrient levels are detected in the stream and groundwater also contains large areas within the floodplain that are permanently saturated. Transects of nested piezometers indicate that hydraulic gradients in these zones are strongly vertical (upwards) and weakly horizontal (toward the stream). Numerous macropores deliver water to the surface. High-hydraulic conductivity sand layers within the soil may interact with the macropore system to create preferential groundwater flow paths.