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Quantifying groundwater nitrogen impacts under an ongoing BMP investigation - Final report to the Environmental Farm Plan

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Title: Quantifying groundwater nitrogen impacts under an ongoing BMP investigation - Final report to the Environmental Farm Plan
Author: Harman, Jackie; McLellan, Jennifer; Ryan, Cathy
Abstract: This project arose out of a concern that groundwater impacts from agricultural chemicals were being inadequately monitored and quantified. The use of an inadequate conceptual model of the recharge and migration of non-point source solutes above and below the water table has underestimated some of the possible future impacts and has oversimplified the design and monitoring of investigative research. The frequent use of a single-point piezometer perpetuated an overly simplistic conceptual model, and resulted in inaccurate monitoring of chemical mass in groundwater from a given trial. Typically BMP evaluations have largely focused on nitrogen fate in the soil and surface water. Groundwater has been infrequently evaluated, and, when considered, almost always entailed the use of a monitoring well with a relatively long screen (e.g. a foot long) which is infrequently sampled. There is strong evidence that wide variations in groundwater nitrate concentrations occur both seasonally and over the length of a single field. These variable nitrate concentrations render the use of an infrequently sampled single-point piezometer questionable. The single point may grossly over- or underestimate the nitrate concentration in groundwater, and does not permit calculation of mass flux of nitrogen to groundwater. Thus, the N input to groundwater cannot be calculated, representing a significant flaw in the groundwater component of BMP evaluations. The stated objectives of this study were two-fold: to design and implement the first-ever intensive groundwater monitoring network in a field scale BMP evaluation, and to compare the results with the commonly used single piezometer method to evaluate relative groundwater impacts under different farm management practices (BMPs).
URI: http://hdl.handle.net/10214/14982
Date: 1998
Rights: In Copyright - Non-Commercial Use Permitted
Rights Holder: Agriculture Canada


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