Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2003
Publication Date: March 15, 2003
Citation: Angier, J., McCarty, G.W., Rice, C., Prestegaard, K.L. 2003. Relationship of stream flow rates to Nitrate-N and pesticide attenuation in an agriculturally impacted first-order riparian system, inner coastal plain, Maryland [abstract]. American Geophysical Union. March 2003. Technical Abstract: A valuable function of riparian zones is the mitigation of agricultural contaminants. This riparian function can be highly variable, both spatially and temporally, within a single ecosystem. Some of this variability may result from hydrological differences, which in turn are influenced by meteorological changes and local geomorphology. The study site is located in the USDA-ARS Beltsville Agricultural Research Center in Maryland. It consists of a small, first-order stream and associated riparian zone, which receives nutrient and pesticide loads from a neighboring agricultural field. The stream is instrumented with five sampling stations that evaluate stream flows and water quality. Approximately 170 piezometers have been instrumented throughout the site. Three full years of data have been compiled and analyzed. The exportability of some contaminants (nitrate-N and metolachlor metabolites) appears to be dependent upon stream flow conditions. Higher stream baseflows are linked to higher stream contaminant loads and concentrations. There are seasonal patterns in stream nitrate fluxes that suggest in-stream nitrate processing occurs. Evidence for loss of nitrate within the stream is especially apparent in late Autumn and early Winter, when decaying leaves collect in pools along the stream channel. Groundwater quality and delivery patterns vary spatially, and in response to changes in climate, affecting the stream water characteristics as well. Stream nitrate and pesticide loads increase with higher stream baseflow conditions because there is more rapid and extensive delivery of contaminated groundwater to the surface through preferential subsurface flow pathways and less residence time in the system overall. In addition, in-stream residence time decreases with higher stream flows, so conditions for in-stream nitrate processing are diminished. Annual stream nitrate loads exported from this system have varied by almost an order of magnitude according to prevailing hydrological and meteorological conditions, providing strong evidence that riparian function may be sensitive to climatic fluctuations.