The role of dynamic surface water-groundwater exchange on streambed denitrification in a first-order, low-relief agricultural watershed

Water Resources Research
By: , and 

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Abstract

The role of temporally varying surface water-groundwater (SW-GW) exchange on nitrate removal by streambed denitrification was examined along a reach of Leary Weber Ditch (LWD), Indiana, a small, first-order, low-relief agricultural watershed within the Upper Mississippi River basin, using data collected in 2004 and 2005. Stream stage, GW heads (H), and temperatures (T) were continuously monitored in streambed piezometers and stream bank wells for two transects across LWD accompanied by synoptic measurements of stream stage, H, T, and nitrate (NO3) concentrations along the reach. The H and T data were used to develop and calibrate vertical two-dimensional, models of streambed water flow and heat transport across and along the axis of the stream. Model-estimated SW-GW exchange varied seasonally and in response to high-streamflow events due to dynamic interactions between SW stage and GW H. Comparison of 2004 and 2005 conditions showed that small changes in precipitation amount and intensity, evapotranspiration, and/or nearby GW levels within a low-relief watershed can readily impact SW-GW interactions. The calibrated LWD flow models and observed stream and streambed NO3 concentrations were used to predict temporal variations in streambed NO3 removal in response to dynamic SW-GW exchange. NO3 removal rates underwent slow seasonal changes, but also underwent rapid changes in response to high-flow events. These findings suggest that increased temporal variability of SW-GW exchange in low-order, low-relief watersheds may be a factor contributing their more efficient removal of NO3.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The role of dynamic surface water-groundwater exchange on streambed denitrification in a first-order, low-relief agricultural watershed
Series title Water Resources Research
DOI 10.1002/2014WR016739
Volume 51
Issue 12
Year Published 2015
Language English
Publisher American Geophysical Union
Contributing office(s) National Research Program - Western Branch
Description 25 p.
First page 9514
Last page 9538
Country United States
State Indiana
Other Geospatial Leary Weber Ditch
Online Only (Y/N) N
Additional Online Files (Y/N) N