CGRG Bibliography of Canadian Geomorphology
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Author : Duval, T.P.; and Hill, A.R.
Date : 2005.
Title : Flow reversal and its effect on nitrogen cycling in a lowland headwater agricultural riparian zone.
Publication : Canadian Geophysical Union Annual Science Meeting, Banff, Alberta. May 8-11, 2005.
Issue :
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Abstract
Recent research indicates that stream recharge to riparian zones can often occur in temperate, lowland landscapes. The hydrology of this flow reversal and its control on riparian nitrogen biogeochemistry was studied in a second order agricultural stream in southern Ontario. Using piezomters and wells to characterize reach-scale subsurface flow this study investigated the timing of flow reversal and lateral extent of this bank seepage. Standard wet chemistry was employed to describe seasonal riparian nitrogen biogeochemistry. Results demonstrated the riparian zone was hydrologically disconnected from the adjoining upslope agricultural field for much of the growing season such that the hydraulic gradient was in the stream-to-field direction. This bank seepage was limited to a maximum distance of 10 m from the stream. A rise in the riparian zone water table during autumn was facilitated by increased lateral stream water seepage due to reduced evapotranspiration. The stream-origin nitrate was removed almost immediately during bank seepage, probably by denitrification. A plot scale investigation confirmed the lack of a gradient in nitrate reduction during bank seepage. Rapid consumption of high stream dissolved oxygen levels at the bank-stream interface facilitated nitrate reduction. Ammonium concentrations increased as the stream-origin water moved farther inland. A bromide/nitrate co-injection experiment depicted a slow movement of stream-borne water inland as well as the development of preferential flowpaths. Applied nitrate levels were significantly reduced during this injection. The lateral hyporheic retention time was quite long along this stream reach. While the flow reversal affected riparian nitrogen cycling, this process does not have a significant influence on stream chemistry due to the low flux of stream water inland.
Bibliography of Canadian Geomorphology