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Date Permissions Signed

9-9-2015

Date of Award

Winter 2007

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Mitchell, Robert J. (Geologist)

Second Advisor

Babcock, R. Scott (Randall Scott)

Third Advisor

Matthews, Robin A., 1952-

Abstract

The Abbotsford-Sumas aquifer is a shallow, unconfined aquifer located in an agriculturally intensive area in northwestern Washington and southwestern British Columbia. Due to aquifer characteristics and surface land use, the Abbotsford-Sumas aquifer has had a history of nitrate contamination from non-point sources. As such, nutrient managers are interested in predictive tools to evaluate management strategies. I assessed the effectiveness of a GIS based nitrate fate and transport model developed specifically for the Abbotsford-Sumas aquifer by Almasri and Kaluarachchi (2004) as a predictive tool for nutrient management. This model couples four sub-models that collectively estimate nutrient loading, predict soil-nitrogen dynamics (NLEAP), calculate groundwater velocity (MODFLOW), and nitrate fate and transport in groundwater (MT3D). The model was used to validate measured nitrate concentrations in the aquifer, and to assess the impact of land use changes and irrigation on nitrate concentrations. Validating nitrate concentrations was difficult due to the model’s design as a single layer aquifer. For those well sites with similar modeled and measured depths, the model was fairly effective at predicting nitrate concentration. Previous work has shown that nitrate is stratified in the Abbotsford-Sumas aquifer, but this fate and transport model estimates the same nitrate concentration for an entire water column. The model was sensitive to land use changes; however, the scale of the model is too coarse to capture local changes and seasonal variation. Changes in irrigation rate and concentration showed little change in resulting nitrate leaching. This lack of response is contrary to previous work, and indicates that the model underestimates irrigation’s impact on groundwater nitrate concentrations.

Type

Text

Publisher

Western Washington University

OCLC Number

175001180

Digital Format

application/pdf

Geographic Coverage

Whatcom County (Wash.)

Genre/Form

Academic theses

Language

English

Rights

Copying of this thesis in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Included in

Geology Commons

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